Adaptive outflow boundary conditions improve post-operative predictions after repair of peripheral pulmonary artery stenosis. Biomechanics and modeling in mechanobiology 2016; 15 (5): 1345-1353
Peripheral pulmonary artery stenosis (PPS) is a congenital abnormality resulting in pulmonary blood flow disparity and right ventricular hypertension. Despite recent advance in catheter-based interventions, surgical reconstruction is still preferred to treat complex PPS. However optimal surgical strategies remain unclear. It would be of great benefit to be able to predict post-operative hemodynamics to assist with surgical planning toward optimizing outcomes. While image-based computational fluid dynamics has been used in cardiovascular surgical planning, most studies have focused on the impact of local geometric changes on hemodynamic performance. Previous experimental studies suggest morphological changes in the pulmonary arteries not only alter local hemodynamics but also lead to distal pulmonary adaptation. In this proof of concept study, a constant shear stress hypothesis and structured pulmonary trees are used to derive adaptive outflow boundary conditions for post-operative simulations. Patient-specific simulations showed the adaptive outflow boundary conditions by the constant shear stress model to provide better predictions of pulmonary flow distribution than the conventional strategy of maintaining outflow boundary conditions. On average, the relative difference, when compared to the gold standard clinical test, in blood flow distribution to the right lung is reduced from 20 to 4%. This suggests adaptive outflow boundary conditions should be incorporated into post-operative modeling in patients with complex PPS.
View details for DOI 10.1007/s10237-016-0766-5
View details for PubMedID 26843118
CT-defined phenotype of pulmonary artery stenoses in Alagille syndrome PEDIATRIC RADIOLOGY 2016; 46 (8): 1120-1127
Alagille syndrome is a rare disorder commonly associated with pulmonary artery stenosis. Studies exist discussing the cardiovascular sequela but no consistent phenotype, or pattern of pulmonary artery stenosis, has been described.The objective of this study was to characterize the distribution and severity of pulmonary artery stenosis in patients with Alagille syndrome based on computed tomography angiography.A retrospective chart review identified patients with Alagille syndrome who had undergone CT angiography. Pulmonary trunk (MPA), left main pulmonary artery (LPA) and right main pulmonary artery (RPA) diameters in Alagille patients were compared with those from matched control subjects. Stenoses at lobar and segmental pulmonary arteries were categorized as: Grade 1 (<33% stenosis), Grade 2 (33-66% stenosis) or Grade 3 (>66% stenosis). Involvement among the different lung regions was then compared.Fifteen patients ages 6months to 17years were identified; one had surgical augmentation of the central pulmonary arteries and was excluded from the central (main, right and left) pulmonary artery analysis. The proximal LPA and RPA, but not the MPA, were significantly smaller than those of the control subjects (P<0.01). The proximal LPA was significantly smaller than the proximal RPA (P<0.01) in the Alagille group (0.55 LPA:RPA ratio). Within the Alagille group, 75% of the lobar and segmental branches showed mild or no stenoses (Grade 1), 17% showed moderate stenosis (Grade 2) and 8% showed severe stenosis (Grade 3). While not statistically significant, the right lung demonstrated a greater percentage of Grades 2 and 3 stenoses (28%, right vs. 20% left, P=0.1). The right middle and lingula lobes of both lungs showed more Grade 2 and 3 stenoses (33% upper/middle vs. 18% lower, P<0.01).We describe a common pattern pulmonary artery stenosis in Alagille patients consisting of severe proximal LPA stenosis, heavy involvement of the lobar and segmental branches (more often right than left), and a greater involvement of the upper lobes. Knowledge of this phenotypic pattern can help in the diagnosis of Alagille syndrome in patients presenting with pulmonary artery stenosis.
View details for DOI 10.1007/s00247-016-3580-4
View details for Web of Science ID 000379037300005
View details for PubMedID 27041277
Hemodynamic Effects of Phenylephrine, Vasopressin, and Epinephrine in Children With Pulmonary Hypertension: A Pilot Study PEDIATRIC CRITICAL CARE MEDICINE 2016; 17 (5): 428-437
During a pulmonary hypertensive crisis, the marked increase in pulmonary vascular resistance can result in acute right ventricular failure and death. Currently, there are no therapeutic guidelines for managing an acute crisis. This pilot study examined the hemodynamic effects of phenylephrine, arginine vasopressin, and epinephrine in pediatric patients with pulmonary hypertension.In this prospective, open-label, nonrandomized pilot study, we enrolled pediatric patients previously diagnosed with pulmonary hypertensive who were scheduled electively for cardiac catheterization. Primary outcome was a change in the ratio of pulmonary-to-systemic vascular resistance. Baseline hemodynamic data were collected before and after the study drug was administered.Eleven of 15 participants were women, median age was 9.2 years (range, 1.7-14.9 yr), and median weight was 26.8 kg (range, 8.5-55.2 kg). Baseline mean pulmonary artery pressure was 49 19 mm Hg, and mean indexed pulmonary vascular resistance was 10 5.4 Wood units. Etiology of pulmonary hypertensive varied, and all were on systemic pulmonary hypertensive medications.Patients 1-5 received phenylephrine 1 g/kg; patients 6-10 received arginine vasopressin 0.03 U/kg; and patients 11-15 received epinephrine 1 g/kg. Hemodynamics was measured continuously for up to 10 minutes following study drug administration.After study drug administration, the ratio of pulmonary-to-systemic vascular resistance decreased in three of five patients receiving phenylephrine, five of five patients receiving arginine vasopressin, and three of five patients receiving epinephrine. Although all three medications resulted in an increase in aortic pressure, only arginine vasopressin consistently resulted in a decrease in the ratio of systolic pulmonary artery-to-aortic pressure.This prospective pilot study of phenylephrine, arginine vasopressin, and epinephrine in pediatric patients with pulmonary hypertensive showed an increase in aortic pressure with all drugs although only vasopressin resulted in a consistent decrease in the ratio of pulmonary-to-systemic vascular resistance. Studies with more subjects are warranted to define optimal dosing strategies of these medications in an acute pulmonary hypertensive crisis.
View details for DOI 10.1097/PCC.0000000000000716
View details for Web of Science ID 000379595900014
View details for PubMedID 27144689
Accuracy of Pulse Oximeters Intended for Hypoxemic Pediatric Patients PEDIATRIC CRITICAL CARE MEDICINE 2016; 17 (4): 315-320
Computational modeling and engineering in pediatric and congenital heart disease. Current opinion in pediatrics 2015; 27 (5): 587-596
Recent methodological advances in computational simulations are enabling increasingly realistic simulations of hemodynamics and physiology, driving increased clinical utility. We review recent developments in the use of computational simulations in pediatric and congenital heart disease, describe the clinical impact in modeling in single-ventricle patients, and provide an overview of emerging areas.Multiscale modeling combining patient-specific hemodynamics with reduced order (i.e., mathematically and computationally simplified) circulatory models has become the de-facto standard for modeling local hemodynamics and 'global' circulatory physiology. We review recent advances that have enabled faster solutions, discuss new methods (e.g., fluid structure interaction and uncertainty quantification), which lend realism both computationally and clinically to results, highlight novel computationally derived surgical methods for single-ventricle patients, and discuss areas in which modeling has begun to exert its influence including Kawasaki disease, fetal circulation, tetralogy of Fallot (and pulmonary tree), and circulatory support.Computational modeling is emerging as a crucial tool for clinical decision-making and evaluation of novel surgical methods and interventions in pediatric cardiology and beyond. Continued development of modeling methods, with an eye towards clinical needs, will enable clinical adoption in a wide range of pediatric and congenital heart diseases.
View details for DOI 10.1097/MOP.0000000000000269
View details for PubMedID 26262579
2015 SPCTPD/ACC/AAP/AHA Training Guidelines for Pediatric Cardiology Fellowship Programs (Revision of the 2005 Training Guidelines for Pediatric Cardiology Fellowship Programs): Introduction CIRCULATION 2015; 132 (6): E43-E47
Task Force 7: Pediatric Cardiology Fellowship Training in Pulmonary Hypertension, Advanced Heart Failure, and Transplantation JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY 2015; 66 (6): 732-739
Task Force 7: Pediatric Cardiology Fellowship Training in Pulmonary Hypertension, Advanced Heart Failure, and Transplantation. SPCTPD/ACC/AAP/AHA. Circulation 2015; 132 (6): e99-e106
Task Force 7: Pediatric Cardiology Fellowship Training in Pulmonary Hypertension, Advanced Heart Failure, and Transplantation CIRCULATION 2015; 132 (6): E99-E106
A multiscale model for the study of cardiac biomechanics in single-ventricle surgeries: a clinical case. Interface focus 2015; 5 (2): 20140079-?
Complex congenital heart disease characterized by the underdevelopment of one ventricular chamber (single ventricle (SV) circulation) is normally treated with a three-stage surgical repair. This study aims at developing a multiscale computational framework able to couple a patient-specific three-dimensional finite-element model of the SV to a patient-specific lumped parameter (LP) model of the whole circulation, in a closed-loop fashion. A sequential approach was carried out: (i) cardiocirculatory parameters were estimated by using a fully LP model; (ii) ventricular material parameters and unloaded geometry were identified by means of the stand-alone, three-dimensional model of the SV; and (iii) the three-dimensional model of SV was coupled to the LP model of the circulation, thus closing the loop and creating a multiscale model. Once the patient-specific multiscale model was set using pre-operative clinical data, the virtual surgery was performed, and the post-operative conditions were simulated. This approach allows the analysis of local information on ventricular function as well as global parameters of the cardiovascular system. This methodology is generally applicable to patients suffering from SV disease for surgical planning at different stages of treatment. As an example, a clinical case from stage 1 to stage 2 is considered here.
View details for DOI 10.1098/rsfs.2014.0079
View details for PubMedID 25844151
Flow simulations and validation for the first cohort of patients undergoing the Y-graft Fontan procedure JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 2015; 149 (1): 247-255
In this study, with the use of computational fluid dynamics, we evaluate the postoperative hemodynamic performance of the first cohort of patients undergoing a handcrafted Y-graft Fontan procedure and validate simulation predictions of hepatic blood flow distribution against invivo clinical data.An 18-122-mm handcrafted Y-graft modification of the Fontan procedure was performed in 6 patients. Early (at the time of discharge) and 6-month postoperative 3-dimensional magnetic resonance imaging data were collected. Patient-specific models were constructed for flow simulations.Hepatic blood flow distribution varied among patients. Lung perfusion data (n=3) showed good agreement with simulations. Postoperative asymmetry in hepatic blood flow distribution was reduced 6 months postoperatively. In 1 patient, low wall shear stress was found in the left limb of the Y-graft, corresponding to the location of subsequent thrombosis in the patient.The credibility and accuracy of simulation-based predictions of postoperative hepatic flow distribution for the Fontan surgery have been validated by invivo lung perfusion data. The performance of the Y-graft design is highly patient-specific. The anastomosis location is likely the most important factor influencing hepatic blood flow distribution. Although the development of thrombosis is multifactorial, the occurrence in 1 patient suggests that simulations should not solely consider the hepatic blood flow distribution but also aim to avoid low wall shear stress in the limbs.
View details for DOI 10.1016/j.jtcvs.2014.08.069
View details for Web of Science ID 000350550100070
Technical feasibility and intermediate outcomes of using a handcrafted, area-preserving, bifurcated Y-graft modification of the Fontan procedure JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 2015; 149 (1): 239-U381
Reported sildenafil side effects in pediatric pulmonary hypertension patients. Frontiers in pediatrics 2015; 3: 12-?
Sildenafil, a phosphodiestase type 5 inhibitor, was approved in 2005 for the treatment of pulmonary arterial hypertension (PAH) in adults and is commonly used off-label for pediatric patients. Little is known, however, about sildenafil's side effects in this population.Single institution, longitudinal survey-based study performed in an outpatient pediatric cardiology clinic. Pediatric patients on sildenafil [alone or in combination with other pulmonary hypertension (PH) therapies] completed questionnaires regarding frequency of vascular, gastrointestinal, neurologic, and hematologic side effects.Between January 2011 and May 2014, 66 pediatric patients with PH on sildenafil filled out 214 surveys, 32 patients (96 surveys) on monotherapy, and 43 patients (118 surveys) on sildenafil plus an endothelin receptor antagonist (ERA) (bosentan or ambrisentan) and/or a prostacyclin (epoprostenol or treprostinil). Overall, 30% of respondents identified at least one side effect. For all patients on sildenafil, incidence of side effects by system was 37% gastrointestinal, 35% vascular, and 22% neurologic. For patients on sildenafil monotherapy, incidence of side effects by system was 24% gastrointestinal, 21% vascular, and 18% neurologic compared to patients on combination therapy who reported an incidence of 48% gastrointestinal, 45% vascular, and 25% neurologic.Incidence of vascular, gastrointestinal, and neurologic side effect in pediatric patients on sildenafil therapy for PAH was 30%. Side effects were more common in patients on combination therapy with an ERA and/or prostacyclin than in patients on sildenafil monotherapy.
View details for DOI 10.3389/fped.2015.00012
View details for PubMedID 25806361
Technical feasibility and intermediate outcomes of using a handcrafted, area-preserving, bifurcated Y-graft modification of the Fontan procedure. journal of thoracic and cardiovascular surgery 2015; 149 (1): 239-45 e1
To demonstrate the technical feasibility and describe intermediate outcomes for the initial patients undergoing handcrafted, area-preserving, Y-graft modification of the Fontan procedure.A retrospective review of a pilot study was undertaken to describe preoperative, intraoperative, and postoperative results.Six patients underwent successful procedures and remain alive 3 to 4 years later. The median age at operation was 3.3 years, and median weight was 13.2 kg. Five operations were done without cardiopulmonary bypass and no intraoperative pressure gradients were found. Five patients were extubated by postoperative day 1, Fontan pressures were 12 to 14 mm Hg, transpulmonary gradients were 6 to 8 mm Hg, and no renal or hepatic function abnormalities were found. Length of stay was 10 to 64 days. One patient required venovenous extracorporeal membrane oxygenation for previously undiagnosed plastic bronchitis (64-day stay); another required reoperation for an incidentally diagnosed aortic thrombus (44-day stay). One patient had occlusion of a Y-graft limb noted on magnetic resonance imaging follow-up at 3 months. Catheterization showed excellent hemodynamic parameters and no Fontan obstruction. Occlusion was believed to be due to right-sided pulmonary arteriovenous malformations and widely discrepant flow (80%) to the right lung leading to low flow in the left limb.The area-preserving, bifurcated Y-graft Fontan modification is technically feasible and shows excellent intermediate outcomes. Additional study is required to determine whether the advantages seen in the computational models will be realized in patients over the long-term, and to optimize patient selection for each of the various Fontan options now available.
View details for DOI 10.1016/j.jtcvs.2014.08.058
View details for PubMedID 25439786
Quantification of Local Hemodynamic Alterations Caused by Virtual Implantation of Three Commercially Available Stents for the Treatment of Aortic Coarctation PEDIATRIC CARDIOLOGY 2014; 35 (4): 732-740
Patients with coarctation of the aorta (CoA) are prone to morbidity including atherosclerotic plaque that has been shown to correlate with altered wall shear stress (WSS) in the descending thoracic aorta (dAo). We created the first patient-specific computational fluid dynamics (CFD) model of a CoA patient treated by Palmaz stenting to date, and compared resulting WSS distributions to those from virtual implantation of Genesis XD and modified NuMED CP stents, also commonly used for CoA. CFD models were created from magnetic resonance imaging, fluoroscopy and blood pressure data. Simulations incorporated vessel deformation, downstream vascular resistance and compliance to match measured data and generate blood flow velocity and time-averaged WSS (TAWSS) results. TAWSS was quantified longitudinally and circumferentially in the stented region and dAo. While modest differences were seen in the distal portion of the stented region, marked differences were observed downstream along the posterior dAo and depended on stent type. The Genesis XD model had the least area of TAWSS values exceeding the threshold for platelet aggregation in vitro, followed by the Palmaz and NuMED CP stents. Alterations in local blood flow patterns and WSS imparted on the dAo appear to depend on the type of stent implanted for CoA. Following confirmation in larger studies, these findings may aid pediatric interventional cardiologists in selecting the most appropriate stent for each patient, and ultimately reduce long-term morbidity following treatment for CoA by stenting.
View details for DOI 10.1007/s00246-013-0845-7
View details for Web of Science ID 000333165400025
View details for PubMedID 24259013
Hot Topics in Tetralogy of Fallot JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY 2013; 62 (23): 2155-2166
Tetralogy of Fallot (TOF) is the most common cyanotic congenital heart defect. We explore "hot topics" to highlight areas of emerging science for clinicians and scientists in moving toward a better understanding of the long-term management of patients with repaired TOF. From a genetic perspective, the etiology of TOF is multifactorial, with a familial recurrence risk of 3%. Cardiac magnetic resonance is the gold standard assessment tool based on its superior imaging of the right ventricular (RV) outflow tract, pulmonary arteries, aorta, and aortopulmonary collaterals, and on its ability to quantify biventricular size and function, pulmonary regurgitation (PR), and myocardial viability. Atrial re-entrant tachycardia will develop in more than 30% of patients, and high-grade ventricular arrhythmias will be seen in about 10% of patients. The overall incidence of sudden cardiac death is estimated at 0.2%/yr. Risk stratification, even with electrophysiologic testing and cardiac magnetic resonance, remains imperfect. Drug therapy has largely been abandoned, and defibrillator placement, despite its high risks for complications and inappropriate discharges, is often recommended for patients at higher risk. Definitive information about optimal surgical strategies for primary repair to preserve RV function, reduce arrhythmia, and optimize functional status is lacking. Post-operative lesions are often amenable to transcatheter intervention. In selected cases, PR may be treated with transcatheter valve insertion. Ongoing surveillance of RV function is a crucial component of clinical assessment. Except for resynchronization with biventricular pacing, no medical therapies have been shown to be effective after RV dysfunction occurs. In patients with significant PR with RV dilation, optimal timing of pulmonary valve replacement remains uncertain, although accepted criteria are emerging.
View details for DOI 10.1016/j.jacc.2013.07.100
View details for Web of Science ID 000328073000002
Food and Drug Administration (FDA) Postmarket Reported Side Effects and Adverse Events Associated with Pulmonary Hypertension Therapy in Pediatric Patients PEDIATRIC CARDIOLOGY 2013; 34 (7): 1628-1636
Because most medications for pediatric pulmonary hypertension (PH) are used off label and based on adult trials, little information is available on pediatric-specific adverse events (AEs). Although drug manufacturers are required to submit postmarket AE reports to the Food and Drug Administration (FDA), this information is rarely transmitted to practitioners. In the setting of a recent FDA warning for sildenafil, the authors sought to give a better description of the AEs associated with current therapies in pediatric PH. In January 2010, a written request was made to the Food and Drug Administration for AE records of commonly used PH medications. Reports were screened for pediatric patients, analyzed in terms of AEs, and compared with the medical literature. Arbitrarily, AEs that could be attributed to concomitant medications were not attributed to the PH medication in question. Adverse events occurring in more than 5% of events for each drug were assumed to be associated with the targeted PH medication. Between November 1997 and December 2009, 588 pediatric AE reports (death in 257 cases) were reported for the three most commonly used therapies: bosentan, epoprostenol, and sildenafil. Many of the AEs were similar to those reported previously. However, 27 AEs not previously reported in the literature (e.g., pulmonary hemorrhage, hemoptysis, and pneumonia) were found. The FDA postmarket records for PH medications in pediatric patients show a significant number of AEs. The discovery of AEs not previously reported will better inform those caring for these complex and critically ill children, and the large number of deaths suggest they may be underreported in current literature.
View details for DOI 10.1007/s00246-013-0688-2
View details for Web of Science ID 000324638500013
View details for PubMedID 23532466
Diagnostic evaluation of paediatric pulmonary hypertension in current clinical practice EUROPEAN RESPIRATORY JOURNAL 2013; 42 (3): 689-700
Current paediatric pulmonary hypertension (PH) diagnostic algorithms include some testing specifically for paediatrics, but it is unclear if this is used in clinical practice. We describe the current diagnostic workup of the TOPP (Tracking Outcomes and Practice in Paediatric Pulmonary hypertension) registry for suspected PH. We investigated 456 patients enrolled until February 2010. The majority had ECGs (94%), echocardiograms (96%) and/or chest radiographs (89%) performed and these were the noninvasive tests most frequently used for evaluation of suspected PH. No patient had all three tests considered normal, suggesting the potential for the combined use to rule out PH. For evaluation of complications associated with heart catheterisation (HC) we analysed a total of 908 HCs reported until February 2012. Of these, 554 were at diagnosis and 354 in follow-up. Complications were reported in 5.9% with five deaths considered related to HC, suggesting a higher rate of HC complications compared to adult studies. However, current recommendations support HC in paediatric PH. A proper application of the risk/benefit ratio for HC requires further data. Most children did not undergo the diagnostic workup currently recommended for adults, which highlights either incomplete awareness of current guidelines and/or challenges their appropriateness for children.
View details for DOI 10.1183/09031936.00140112
View details for Web of Science ID 000326160500019
View details for PubMedID 23563261
Children with pulmonary arterial hypertension and prostanoid therapy: Long-term hemodynamics JOURNAL OF HEART AND LUNG TRANSPLANTATION 2013; 32 (5): 546-552
Pediatric patients with severe pulmonary arterial hypertension (PAH) are treated with intravenous epoprostenol or intravenous or subcutaneous treprostinil. Little is known about longitudinal hemodynamics and outcomes of epoprostenol, treprostinil, and transitions from epoprostenol to treprostinil.This was retrospective study of 77 pediatric patients (47 idiopathic PAH, 24 congenital heart disease-PAH) receiving epoprostenol or treprostinil from 1992 to 2010 at 2 centers. Outcomes were defined as living vs dead/transplant.Mean age at baseline was 7.7 5.2 years, with follow-up of 4.3 3.4 years. Thirty-seven patients were treated with epoprostenol, 20 with treprostinil, and 20 were transitioned from epoprostenol to treprostinil. Mean pulmonary-to-systemic vascular resistance ratio (Rp/Rs) for epoprostenol was 1.0 0.4, 0.8 0.4, 0.8 0.4, 1.0 0.4, and 1.2 0.4, respectively, at baseline, 1, 2, 3, and 4 years. For treprostinil, Rp/Rs was 0.9 0.3, 0.7 0.3, 0.5 0.2, (p < 0.01 vs baseline), and 1.1 0.2, respectively, at baseline, 1, 2, and 3 to 4 years, respectively. There were similar changes in mean pulmonary artery pressure and pulmonary vascular resistance index. The Rp/Rs 1 year after epoprostenol to treprostinil transition increased from 0.6 to 0.8 (n = 7). Changes not statistically significant unless noted. Eight patients died or received a transplant within 2 years of baseline; compared with the rest of the cohort, mean baseline Rp/Rs, right atrial pressure, and pulmonary vascular resistance index were significantly worse in this group. Thirty-nine patients remain on prostanoids, 17 are off, 16 died, and 5 received heart-lung transplant. Kaplan-Meier 5-year transplant-free survival was 70% (95% confidence interval, 56%-80%).There was improvement in Rp/Rs on both therapies at 1 to 2 years that was not sustained. The 5-year transplant-free survival was better than in similar adult studies.
View details for DOI 10.1016/j.healun.2013.01.1055
View details for Web of Science ID 000317708500012
Validation of the Innocor Device for Noninvasive Measurement of Oxygen Consumption in Children and Adults PEDIATRIC CARDIOLOGY 2013; 34 (4): 847-852
Outpatient measurements of oxygen consumption (VO2) and cardiac output (CO) are valuable in the management of pediatric cardiac disease. Current methods are inaccurate and cumbersome or require invasive procedures. New devices to measure these variables in adults have not been rigorously tested for children. The Innocor system uses a photoacoustic analyzer to measure gas content for noninvasive measurement of VO2 and CO. This study sought to validate Innocor-derived VO2 measurements in children and adults by comparing them against the gold standard Douglas bag method. Subjects were tested in an outpatient setting. Adaptations were made for pediatric patients based on weight. Resting VO2 measurements were obtained simultaneously by the Innocor system and Douglas bag during 3 min. The study enrolled 31 children (mean age, 12.2 years; range, 7-17 years, 17 girls) and 29 adults (mean age, 36.7 years; range, 19-57 years; 17 women). Strong correlation between the two techniques was seen for both the adults (R (2) = 0.88) and the children (R (2) = 0.82). The average discrepancy between the Innocor and Douglas bag measurements was 1.7 % (range, 0.6-19.1 %) for the adults, and 5.4 % (range, 0.1-32.2 %) for the children. The discrepancy was more than 15 % for 17 % of the adults and 22 % of the children, with the Innocor device tending to overestimate VO2 in children compared with the Douglas bag. This trend was not seen in adults. The Innocor system has excellent correlation with the Douglas bag and shows promise for noninvasive measurement of VO2 and CO in the school-age pediatric population.
View details for DOI 10.1007/s00246-012-0555-6
View details for Web of Science ID 000316957900010
Magnetic resonance imaging of the right ventricle in pediatric pulmonary arterial hypertension. Pulmonary circulation 2013; 3 (2): 350-355
Pulmonary arterial hypertension (PAH) causes changes in the right ventricle (RV), affecting RV size and function, ultimately leading to death. These changes have been evaluated by cardiac MRI (CMR) in adults with PAH, but not in children. Using CMR in pediatric patients with PAH, we examined how RV size and function (1) compare to normal data, (2) change over time, and (3) compare to similar studies in the adult population. Data from two institutions were retrospectively reviewed. Subjects with PAH and a CMR were included. Baseline CMR variables (right and left ventricular end-diastolic and end-systolic volumes indexed for body surface area, and calculated stroke volume and ejection fraction) were compared to normative data and follow-up CMR data. Twenty-six subjects (15 female), age 2-16 (mean 11) years, with idiopathic PAH were included. All patients were on PAH medication, and 65% on prostacyclin therapy. The baseline 6-Minute Walk Distance (6MWD; 481 137) was normal. RV volumes and ejection fraction were markedly abnormal compared to normal data (P < 0.001). Follow-up CMRs were analyzed in 15 patients. RV volumes and function and LV stroke volume showed no significant change over one year. Our pediatric patients with PAH have markedly abnormal right ventricles by CMR but have normal walk distances. The lack of change in CMR parameters over one year may represent a stable cohort and is different than similar studies in adults.
View details for DOI 10.4103/2045-8932.114763
View details for PubMedID 24015335
Implications of the U.S. Food and Drug Administration Warning against the Use of Sildenafil for the Treatment of Pediatric Pulmonary Hypertension AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE 2013; 187 (6): 572-575
Pulmonary arterial hypertension (PAH) contributes to disability and death in children with diverse cardiac, pulmonary, or systemic diseases, and therapeutic options are currently limited. Data from adult studies provide the basis for most PAH-specific therapies; however, many of these medications are commonly used in children on an off-label basis due to the life-threatening nature of PAH. Although currently approved for use in adult PAH, sildenafil is used extensively off-label for the treatment of neonates, infants, and children with PAH. Past studies have generally suggested favorable effects and outcomes in infants and young children with PAH, but these reports are generally uncontrolled observations, except for one single-center trial for persistent pulmonary hypertension of the newborn. Despite extensive clinical experience with sildenafil therapy in children and approval by the European Medicines Agency for its pediatric use in Europe, the U.S. Food and Drug Administration recently issued a warning against the use of sildenafil for pediatric PAH between 1 and 17 years of age due to an apparent increase in mortality during long-term therapy. Although these data are extremely limited, this U.S. Food and Drug Administration review challenges the pediatric PAH community to further assess the efficacy and safety of sildenafil, especially with chronic treatment. Although low doses of sildenafil are likely safe in pediatric PAH, further studies should carefully examine its role in the long-term therapy of children, especially with diverse causes of PAH. Pediatric patients with PAH require close surveillance and frequent monitoring, and persistent sildenafil monotherapy is likely insufficient with disease progression.
View details for DOI 10.1164/rccm.201210-1928PP
View details for Web of Science ID 000316423800005
View details for PubMedID 23220921
Computational fluid dynamic simulations for determination of ventricular workload in aortic arch obstructions. journal of thoracic and cardiovascular surgery 2013; 145 (2): 489-495 e1
The cardiac workload associated with various types of aortic obstruction was determined using computational fluid dynamic simulations.Computed tomography image data were collected from 4 patients with 4 distinct types of aortic arch obstructions and 4 controls. The categorization of arch hypoplasia corresponded to the "A, B, C" nomenclature of arch interruption; a type "D" was added to represent diffuse arch hypoplasia. Measurements of the vessel diameter were compared against the normal measurements to determine the degree of narrowing. Three-dimensional models were created for each patient, and additional models were created for type A and B hypoplasia to represent 25%, 50%, and 75% diameter narrowing. The boundary conditions for the computational simulations were chosen to achieve realistic flow and pressures in the control cases. The simulations were then repeated after changing the boundary conditions to represent a range of cardiac and vascular adaptations. The resulting cardiac workload was compared with the control cases.Of the 4 patients investigated, 1 had aortic coarctation and 3 had aortic hypoplasia. The cardiac workload of the patients with 25% narrowing type A and B hypoplasia was not appreciably different from that of the control. When comparing the different arch obstructions, 75% type A, 50% type B, and 50% type D hypoplasia required a greater workload increase than 75% coarctation.The present study has determined the hemodynamic significance of aortic arch obstruction using computational simulations to calculate the cardiac workload. These results suggest that all types of hypoplasia pose more of a workload challenge than coarctation with an equivalent degree of narrowing.
View details for DOI 10.1016/j.jtcvs.2012.03.051
View details for PubMedID 22516390
Computational fluid dynamic simulations for determination of ventricular workload in aortic arch obstructions JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 2013; 145 (2): 489-U535
Optimization of a Y-Graft Design for Improved Hepatic Flow Distribution in the Fontan Circulation JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME 2013; 135 (1)
Single ventricle heart defects are among the most serious congenital heart diseases, and are uniformly fatal if left untreated. Typically, a three-staged surgical course, consisting of the Norwood, Glenn, and Fontan surgeries is performed, after which the superior vena cava (SVC) and inferior vena cava (IVC) are directly connected to the pulmonary arteries (PA). In an attempt to improve hemodynamic performance and hepatic flow distribution (HFD) of Fontan patients, a novel Y-shaped graft has recently been proposed to replace the traditional tube-shaped extracardiac grafts. Previous studies have demonstrated that the Y-graft is a promising design with the potential to reduce energy loss and improve HFD. However these studies also found suboptimal Y-graft performance in some patient models. The goal of this work is to determine whether performance can be improved in these models through further design optimization. Geometric and hemodynamic factors that influence the HFD have not been sufficiently investigated in previous work, particularly for the Y-graft. In this work, we couple Lagrangian particle tracking to an optimal design framework to study the effects of boundary conditions and geometry on HFD. Specifically, we investigate the potential of using a Y-graft design with unequal branch diameters to improve hepatic distribution under a highly uneven RPA/LPA flow split. As expected, the resulting optimal Y-graft geometry largely depends on the pulmonary flow split for a particular patient. The unequal branch design is demonstrated to be unnecessary under most conditions, as it is possible to achieve the same or better performance with equal-sized branches. Two patient-specific examples show that optimization-derived Y-grafts effectively improve the HFD, compared to initial nonoptimized designs using equal branch diameters. An instance of constrained optimization shows that energy efficiency slightly increases with increasing branch size for the Y-graft, but that a smaller branch size is preferred when a proximal anastomosis is needed to achieve optimal HFD.
View details for DOI 10.1115/1.4023089
View details for Web of Science ID 000314033800002
View details for PubMedID 23363213
Chronic effects of pulmonary artery stenosis on hemodynamic and structural development of the lungs AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY 2013; 304 (1): L17-L28
Chronic effects of pulmonary artery stenosis on hemodynamic and structural development of the lungs. American journal of physiology. Lung cellular and molecular physiology 2013; 304 (1): L17-28
Pulmonary artery (PA) stenosis is a difficult obstructive defect to manage since clinicians cannot know a priori which obstructions to treat and when. Prognosis of PA stenosis and its chronic effects on lung development are poorly understood. This study aimed to characterize the hemodynamic and structural effects of PA stenosis during development. Fourteen male Sprague-Dawley rats underwent left PA (LPA) banding at age 21 days, and 13 underwent sham operation. Hemodynamic and structural impacts were studied longitudinally at 20, 36, 52, 100, and 160 days. Chronic LPA banding resulted in a significant reduction in LPA flow (P < 0.0001) and size of both proximal LPA (P < 0.0001) and distal LPA (P < 0.01), as well as a significant increase in flow and size of the right PA (P < 0.05) throughout development. Flows and sizes adapted such that normal levels of wall shear were restored after banding. At 160 days, LPA banding resulted in a significant decrease in left lung volume and an increase in right lung volume but no significant differences in total lung volume. There was an elevation of proximal LPA pressure as well as right ventricular hypertrophy in the banded animals. The banded lung exhibited arterial disorganization, loss of vessels, and enlargement of its bronchial arteries, whereas the contralateral lung showed signs of vascular pathology. There are consequences on development of both lungs in the presence of an LPA stenosis at young age. These results suggest that early intervention may be necessary to optimize left lung growth and minimize right lung vascular pathology.
View details for DOI 10.1152/ajplung.00412.2011
View details for PubMedID 23043077
Wall shear stress is decreased in the pulmonary arteries of patients with pulmonary arterial hypertension: An image-based, computational fluid dynamics study. Pulmonary circulation 2012; 2 (4): 470-476
Previous clinical studies in pulmonary arterial hypertension (PAH) have concentrated predominantly on distal pulmonary vascular resistance, its contribution to the disease process, and response to therapy. However, it is well known that biomechanical factors such as shear stress have an impact on endothelial health and dysfunction in other parts of the vasculature. This study tested the hypothesis that wall shear stress is reduced in the proximal pulmonary arteries of PAH patients with the belief that reduced shear stress may contribute to pulmonary endothelial cell dysfunction and as a result, PAH progression. A combined MRI and computational fluid dynamics (CFD) approach was used to construct subject-specific pulmonary artery models and quantify flow features and wall shear stress (WSS) in five PAH patients with moderate-to-severe disease and five age- and sex-matched controls. Three-dimensional model reconstruction showed PAH patients have significantly larger main, right, and left pulmonary artery diameters (3.5 0.4 vs. 2.7 0.1 cm, P = 0.01; 2.5 0.4 vs. 1.9 0.2 cm, P = 0.04; and 2.6 0.4 vs. 2.0 0.2 cm, P = 0.01, respectively), and lower cardiac output (3.7 1.2 vs. 5.8 0.6 L/min, P = 0.02.). CFD showed significantly lower time-averaged central pulmonary artery WSS in PAH patients compared to controls (4.3 2.8 vs. 20.5 4.0 dynes/cm(2), P = 0.0004). Distal WSS was not significantly different. A novel method of measuring WSS was utilized to demonstrate for the first time that WSS is altered in some patients with PAH. Using computational modeling in patient-specific models, WSS was found to be significantly lower in the proximal pulmonary arteries of PAH patients compared to controls. Reduced WSS in proximal pulmonary arteries may play a role in the pathogenesis and progression of PAH. This data may serve as a basis for future in vitro studies of, for example, effects of WSS on gene expression.
View details for DOI 10.4103/2045-8932.105035
View details for PubMedID 23372931
Electrical and mechanical dyssynchrony in pediatric pulmonary hypertension JOURNAL OF HEART AND LUNG TRANSPLANTATION 2012; 31 (8): 825-830
Electrical and mechanical dyssynchrony are often seen in patients with left ventricular failure. In pediatric pulmonary hypertension (PH), right ventricular failure predominates; however, the prevalence of electrical and/or mechanical dyssynchrony in these patients is unknown. We examined the prevalence of electrical and mechanical dyssynchrony in pediatric PH patients.Medical records (including, functional status, electrocardiograms and echocardiograms) of pediatric PH patients were reviewed. QRS duration z-scores were calculated to determine electrical dyssynchrony. Echo vector velocity imaging was used to calculate the mechanical dyssynchrony index (DI).Seventy-seven PH patients (idiopathic pulmonary arterial hypertension [IPAH]: n = 26; congenital heart disease: n = 41; other: n = 10) were studied. Electrical dyssynchrony was seen in 84% (p < 0.01 vs historic controls), with a mean z-score of 4.3 (95% CI 3.5 to 5.1). There was no difference between those with IPAH, z = 3.6 (95% CI 2.5 to 4.6), and those without, z = 4.7 (95% CI 3.6 to 5.8). Mechanical dyssynchrony was seen in 76% of patients (mean DI = 66 47 vs 18 8 milliseconds in historic controls, p < 0.01) in both IPAH and non-IPAH patients. Post-operative congenital heart disease patients had the largest dyssynchrony index. No correlation was found among electrical or mechanical dyssynchrony, hemodynamics or disease severity.Significant electrical and mechanical dyssynchrony is present in pediatric PH patients, regardless of etiology. The overall effect of electrical and mechanical dyssynchrony on outcomes in this patient population is still unknown. Select patients may benefit from resynchronization therapy.
View details for DOI 10.1016/j.healun.2012.04.004
View details for Web of Science ID 000306449000006
View details for PubMedID 22682994
Pulmonary reperfusion injury after the unifocalization procedure for tetralogy of Fallot, pulmonary atresia, and major aortopulmonary collateral arteries JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 2012; 144 (1): 184-189
The aims of our study are to describe the incidence, clinical profile, and risk factors for pulmonary reperfusion injury after the unifocalization procedure for tetralogy of Fallot, pulmonary atresia, and major aortopulmonary collateral arteries. We hypothesized the following: (1) Pulmonary reperfusion injury is more likely to occur after unifocalization procedures in which a septated circulation is not achieved, (2) pulmonary reperfusion injury is directly related to the severity of stenosis in major aortopulmonary collateral arteries, and (3) pulmonary reperfusion injury leads to longer intubation time and longer hospitalization.Consecutive patients with tetralogy of Fallot/pulmonary atresia/major aortopulmonary collateral arteries who underwent unifocalization procedures over a 5-year period were identified in our institutional database. Chest radiographs before the unifocalization procedure, from postoperative days 0 to 4, and from 2 weeks after the unifocalization procedure or at discharge were evaluated by a pediatric radiologist for localized pulmonary edema. Determination of stenosis severity was based on review of preoperative angiograms. Statistical analyses using multivariate repeated-measures analyses were performed with generalized estimating equations.Pulmonary reperfusion injury was present after 42 of 65 (65%) unifocalization procedures. In 36 of 42 cases of reperfusion injury, unilateral injury was present. Risk factors for the development of reperfusion injury included bilateral unifocalization (P=.01) and degree of stenosis (P=.03). We did not identify an association between pulmonary reperfusion injury and time to tracheal extubation or hospital discharge.Pulmonary reperfusion injury is common after the unifocalization procedure for tetralogy of Fallot/pulmonary atresia/major aortopulmonary collateral arteries. Severity of stenosis and bilateral unifocalization are associated with the development of reperfusion injury.
View details for DOI 10.1016/j.jtcvs.2011.12.030
View details for Web of Science ID 000305412200031
View details for PubMedID 22244564
Hepatic blood flow distribution and performance in conventional and novel Y-graft Fontan geometries: A case series computational fluid dynamics study JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 2012; 143 (5): 1086-1097
A novel Y-shaped baffle has been proposed for the Fontan operation with promising initial results. However, previous studies have relied either on idealized models or a single patient-specific model. The objective of this study is to comprehensively compare the hemodynamic performance and hepatic blood flow distribution of the Y-graft Fontan baffle with 2 current designs using multiple patient-specific models.Y-shaped and tube-shaped grafts were virtually implanted into 5 patient-specific Glenn models forming 3 types of Fontan geometries: Y-graft, T-junction, and offset. Unsteady flow simulations were performed at rest and at varying exercise conditions. The hepatic flow distribution between the right and left lungs was carefully quantified using a particle tracking method. Other physiologically relevant parameters such as energy dissipation, superior vena cava pressure, and wall shear stress were evaluated.The Fontan geometry significantly influences the hepatic flow distribution. The Y-graft design improves the hepatic flow distribution effectively in 4 of 5 patients, whereas the T-junction and offset designs may skew as much as 97% of hepatic flow to 1 lung in 2 cases. Sensitivity studies show that changes in pulmonary flow split can affect the hepatic flow distribution dramatically but that some Y-graft and T-junction designs are relatively less sensitive than offset designs. The Y-graft design offers moderate improvements over the traditional designs in power loss and superior vena cava pressure in all patients.The Y-graft Fontan design achieves overall superior hemodynamic performance compared with traditional designs. However, the results emphasize that no one-size-fits-all solution is available that will universally benefit all patients and that designs should be customized for individual patients before clinical application.
View details for DOI 10.1016/j.jtcvs.2011.06.042
View details for Web of Science ID 000302810700015
View details for PubMedID 21962841
Fluid-structure interaction simulations of the Fontan procedure using variable wall properties INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2012; 28 (5): 513-527
A method for quantitative characterization of growth in the 3-D structure of rat pulmonary arteries MICROVASCULAR RESEARCH 2012; 83 (2): 146-153
Understanding mechanisms causing pulmonary vascular disease (PVD) frequently requires a thorough understanding of the underlying structural changes in the pulmonary circulation. Animal models have been used extensively to study different forms of PVD but conventional experimental techniques are limited in their ability to allow the study of the whole pulmonary vasculature at once. In this study, we introduce novel techniques of arterial casting, high-resolution imaging and tree analysis to study the pulmonary circulation in rodent models. Male Sprague-Dawley rats were used at 20, 36, 52, 100 and 160 days of age. A technique involving arterial casting with Microfil silicone polymer, high-resolution micro-computed tomography (micro-CT) at 12.5 ?m resolution and image data analysis involving segmentation and skeletonization was developed to both qualitatively and quantitatively describe the changes in the pulmonary vasculature with increasing age. Parameters identified to affect the quality of pulmonary arterial casting included polymer flow rate, total injected volume, polymer viscosity and polymerization time. By optimizing these parameters, we successfully created arterial casts of the pulmonary circulation in rats of different ages and demonstrated the feasibility of quantitatively characterizing the changes in the number of vessels with postnatal growth. These preliminary data suggest that the number of vessels with lumen diameters of 50-200 ?m increases rapidly in both lungs between 52 and 100 days of age. With this new technique, the pulmonary vasculature can now be studied in a whole lung animal model to better understand the global effects of disease on vascular structure.
View details for DOI 10.1016/j.mvr.2011.12.003
View details for Web of Science ID 000300818800009
View details for PubMedID 22230111
Sildenafil for Severe Lymphatic Malformations NEW ENGLAND JOURNAL OF MEDICINE 2012; 366 (4): 384-386
The Adult Congenital and Pediatric Cardiology Section Increasing the Opportunities for the Congenital Heart Disease Community Within the American College of Cardiology JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY 2012; 59 (1): 84-87
The Adult Congenital and Pediatric Cardiology (AC/PC) Section was established to develop a clear voice within the American College of Cardiology and address the myriad issues facing the congenital heart disease profession. The Section is governed by the AC/PC Council, which includes pediatric cardiologists, adult congenital cardiologists, a cardiac care associate, and a fellow-in-training member. The Council is responsible for bidirectional communication between the College's Board of Trustees and the AC/PC Section members. Since its founding in 2004, Section objectives have been defined by the College's mission: to advocate for quality cardiovascular care through education, research promotion, and the development and application of standards and guidelines and to influence health care policy. The pillars of the College-advocacy, quality, education, and member engagement-serve as the defining template for the Section's strategy. The Section has developed work groups in advocacy, clinical practice, education and training, quality, and publications. A separate leadership group has been developed for adult congenital heart disease. Work groups are open to all Section members. Recognition of the importance of lifelong care in congenital heart disease led Section leaders to incorporate pediatric cardiology and adult congenital heart disease content into each of the work groups. There are more than 1,200 Section members, with nearly 400 members actively contributing to Section activities. This article outlines Section efforts to date and highlights significant successes to date.
View details for DOI 10.1016/j.jacc.2011.08.060
View details for Web of Science ID 000298369800013
View details for PubMedID 22192673
Hypoplastic Left Heart Syndrome Current Considerations and Expectations JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY 2012; 59 (1): S1-S42
In the recent era, no congenital heart defect has undergone a more dramatic change in diagnostic approach, management, and outcomes than hypoplastic left heart syndrome (HLHS). During this time, survival to the age of 5 years (including Fontan) has ranged from 50% to 69%, but current expectations are that 70% of newborns born today with HLHS may reach adulthood. Although the 3-stage treatment approach to HLHS is now well founded, there is significant variation among centers. In this white paper, we present the current state of the art in our understanding and treatment of HLHS during the stages of care: 1) pre-Stage I: fetal and neonatal assessment and management; 2) Stage I: perioperative care, interstage monitoring, and management strategies; 3) Stage II: surgeries; 4) Stage III: Fontan surgery; and 5) long-term follow-up. Issues surrounding the genetics of HLHS, developmental outcomes, and quality of life are addressed in addition to the many other considerations for caring for this group of complex patients.
View details for DOI 10.1016/j.jacc.2011.09.022
View details for Web of Science ID 000298370300001
View details for PubMedID 22192720
COMPARISON OF CLINICAL AND SIMULATION RESULTS FOR THE STANFORD Y-GRAFT FONTAN PILOT TRIAL PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B 2012: 463-464
A PUBLIC REPOSITORY OF IMAGE-BASED COMPUTATIONAL MODELS FOR PATIENT-SPECIFIC BLOOD FLOW SIMULATION PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, PTS A AND B 2012: 969-970
Virtual surgeries in patients with congenital heart disease: a multi-scale modelling test case PHILOSOPHICAL TRANSACTIONS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES 2011; 369 (1954): 4316-4330
The objective of this work is to perform a virtual planning of surgical repairs in patients with congenital heart diseases--to test the predictive capability of a closed-loop multi-scale model. As a first step, we reproduced the pre-operative state of a specific patient with a univentricular circulation and a bidirectional cavopulmonary anastomosis (BCPA), starting from the patient's clinical data. Namely, by adopting a closed-loop multi-scale approach, the boundary conditions at the inlet and outlet sections of the three-dimensional model were automatically calculated by a lumped parameter network. Successively, we simulated three alternative surgical designs of the total cavopulmonary connection (TCPC). In particular, a T-junction of the venae cavae to the pulmonary arteries (T-TCPC), a design with an offset between the venae cavae (O-TCPC) and a Y-graft design (Y-TCPC) were compared. A multi-scale closed-loop model consisting of a lumped parameter network representing the whole circulation and a patient-specific three-dimensional finite volume model of the BCPA with detailed pulmonary anatomy was built. The three TCPC alternatives were investigated in terms of energetics and haemodynamics. Effects of exercise were also investigated. Results showed that the pre-operative caval flows should not be used as boundary conditions in post-operative simulations owing to changes in the flow waveforms post-operatively. The multi-scale approach is a possible solution to overcome this incongruence. Power losses of the Y-TCPC were lower than all other TCPC models both at rest and under exercise conditions and it distributed the inferior vena cava flow evenly to both lungs. Further work is needed to correlate results from these simulations with clinical outcomes.
View details for DOI 10.1098/rsta.2011.0130
View details for Web of Science ID 000295458900010
View details for PubMedID 21969678
Three-Dimensional Simulations in Glenn Patients: Clinically Based Boundary Conditions, Hemodynamic Results and Sensitivity to Input Data JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME 2011; 133 (11)
While many congenital heart defects can be treated without significant long term sequelae, some achieve successful palliation as their definitive endpoints. The single-ventricle defect is one such defect and leaves the child with only one operational ventricle, requiring the systemic and the pulmonary circulations to be placed in series through several operations performed during early childhood. Numerical simulations may be used to investigate these hemodynamic conditions and their relation to post-operative sequelae; however, they rely heavily on boundary condition prescription. In this study, we investigate the impact of hemodynamic input data uncertainties on simulation results. Imaged-based patient-specific models of the multi-branched pulmonary arteries and superior vena cava were built for five cavopulmonary connection (i.e. Glenn) patients. Magnetic resonance imaging and catheterization data were acquired for each patient prior to their Fontan surgery. Inflow and outflow boundary conditions were constructed to match available clinical data and resulted in the development of a framework to incorporate these types of clinical data into patient-specific simulations. Three-dimensional computational fluid dynamics simulations were run and hemodynamic indicators were computed. Power loss was low (and efficiency very high) and a linear correlation was found between power loss and cardiac index among the five patients. Other indicators such as low wall shear stress were considered to better characterize these patients. Flow was complex and oscillatory near the anastomosis, and laminar in the smaller branches. While common trends were seen among patients, results showed differences among patients, especially in the 3D maps, strengthening the importance of patient-specific simulations. A sensitivity analysis was performed to investigate the impact of input data (clinical and modeling) to construct boundary conditions on several indicators. Overall, the sensitivity of the output indicators to the input data was small but non-negligible. The sensitivity of commonly used hemodynamic indicators to compare patients is discussed in this context. Power efficiency was much more sensitive to pressure variation than power loss. To increase the precision of such indicators, mean flow split between right and left lungs needs to be measured with more accuracy with higher priority than refining the model of how the flow is distributed on average among the smaller branches. Although 10% flow split imprecision seemed reasonable in terms of patient comparison, this study suggests that the common practice of imposing a right pulmonary artery/left pulmonary artery flow split of 55%/45% when performing patient specific simulations should be avoided. This study constitutes a first step towards understanding the hemodynamic differences between pre- and post Fontan surgery, predicting these differences, and evaluating surgical outcomes based on preoperative data.
View details for DOI 10.1115/1.4005377
View details for Web of Science ID 000298009500006
View details for PubMedID 22168738
Computational Simulations for Aortic Coarctation: Representative Results From a Sampling of Patients JOURNAL OF BIOMECHANICAL ENGINEERING-TRANSACTIONS OF THE ASME 2011; 133 (9)
Treatments for coarctation of the aorta (CoA) can alleviate blood pressure (BP) gradients (?), but long-term morbidity still exists that can be explained by altered indices of hemodynamics and biomechanics. We introduce a technique to increase our understanding of these indices for CoA under resting and nonresting conditions, quantify their contribution to morbidity, and evaluate treatment options. Patient-specific computational fluid dynamics (CFD) models were created from imaging and BP data for one normal and four CoA patients (moderate native CoA: ?12 mmHg, severe native CoA: ?25 mmHg and postoperative end-to-end and end-to-side patients: ?0 mmHg). Simulations incorporated vessel deformation, downstream vascular resistance and compliance. Indices including cyclic strain, time-averaged wall shear stress (TAWSS), and oscillatory shear index (OSI) were quantified. Simulations replicated resting BP and blood flow data. BP during simulated exercise for the normal patient matched reported values. Greatest exercise-induced increases in systolic BP and mean and peak ?BP occurred for the moderate native CoA patient (SBP: 115 to 154 mmHg; mean and peak ?BP: 31 and 73 mmHg). Cyclic strain was elevated proximal to the coarctation for native CoA patients, but reduced throughout the aorta after treatment. A greater percentage of vessels was exposed to subnormal TAWSS or elevated OSI for CoA patients. Local patterns of these indices reported to correlate with atherosclerosis in normal patients were accentuated by CoA. These results apply CFD to a range of CoA patients for the first time and provide the foundation for future progress in this area.
View details for DOI 10.1115/1.4004996
View details for Web of Science ID 000295882200008
View details for PubMedID 22010743
Computational Simulations Demonstrate Altered Wall Shear Stress in Aortic Coarctation Patients Treated by Resection with End-to-end Anastomosis CONGENITAL HEART DISEASE 2011; 6 (5): 432-443
Atherosclerotic plaque in the descending thoracic aorta (dAo) is related to altered wall shear stress (WSS) for normal patients. Resection with end-to-end anastomosis (RWEA) is the gold standard for coarctation of the aorta (CoA) repair, but may lead to altered WSS indices that contribute to morbidity.Computational fluid dynamics (CFD) models were created from imaging and blood pressure data for control subjects and age- and gender-matched CoA patients treated by RWEA (four males, two females, 15 8 years). CFD analysis incorporated downstream vascular resistance and compliance to generate blood flow velocity, time-averaged WSS (TAWSS), and oscillatory shear index (OSI) results. These indices were quantified longitudinally and circumferentially in the dAo, and several visualization methods were used to highlight regions of potential hemodynamic susceptibility.The total dAo area exposed to subnormal TAWSS and OSI was similar between groups, but several statistically significant local differences were revealed. Control subjects experienced left-handed rotating patterns of TAWSS and OSI down the dAo. TAWSS was elevated in CoA patients near the site of residual narrowings and OSI was elevated distally, particularly along the left dAo wall. Differences in WSS indices between groups were negligible more than 5?dAo diameters distal to the aortic arch.Localized differences in WSS indices within the dAo of CoA patients treated by RWEA suggest that plaque may form in unique locations influenced by the surgical repair. These regions can be visualized in familiar and intuitive ways allowing clinicians to track their contribution to morbidity in longitudinal studies.
View details for DOI 10.1111/j.1747-0803.2011.00553.x
View details for Web of Science ID 000294919100005
View details for PubMedID 21801315
Quantitative characterization of postnatal growth trends in proximal pulmonary arteries in rats by phase-contrast magnetic resonance imaging AMERICAN JOURNAL OF PHYSIOLOGY-LUNG CELLULAR AND MOLECULAR PHYSIOLOGY 2011; 301 (3): L368-L379
Malformations of the pulmonary arteries can increase right heart workload and result in morbidity, heart failure, and death. With the increased use of murine models to study these malformations, there is a pressing need for an accurate and noninvasive experimental technique that is capable of characterizing pulmonary arterial hemodynamics in these animals. We describe the growth trends of pulmonary arteries in 13 male Sprague-Dawley rats at 20, 36, 52, 100, and 160 days of age with the introduction of phase-contrast MRI as such a technique. PCMRI results correlated closely with cardiac output measurements by ultrasound echocardiography and with fluorescent microspheres in right-left lung flow split (flow partition). Mean flow, average cross-sectional area, distensibility, and shear rates for the right and left pulmonary arteries (RPA and LPA) were calculated. The RPA was larger and received more flow at all times than the LPA (P < 0.0001). Right-left flow split did not change significantly with age, and arterial distensibility was not significantly different between RPA and LPA, except at 160 days (P < 0.01). Shear rates were much higher for the LPA than the RPA (P < 0.0001) throughout development. The RPA and LPA showed different structure-function relationships but obeyed similar allometric scaling laws, with scaling exponents comparable to those of the main pulmonary artery. This study is the first to quantitatively describe changes in RPA and LPA flows and sizes with development and to apply phase-contrast MRI techniques to pulmonary arteries in rats.
View details for DOI 10.1152/ajplung.00069.2011
View details for Web of Science ID 000295356900014
View details for PubMedID 21665961
Indications for Cardiac Catheterization and Intervention in Pediatric Cardiac Disease A Scientific Statement From the American Heart Association CIRCULATION 2011; 123 (22): 2607-2652
A Rapid and Computationally Inexpensive Method to Virtually Implant Current and Next-Generation Stents into Subject-Specific Computational Fluid Dynamics Models ANNALS OF BIOMEDICAL ENGINEERING 2011; 39 (5): 1423-1437
Computational modeling is often used to quantify hemodynamic alterations induced by stenting, but frequently uses simplified device or vascular representations. Based on a series of Boolean operations, we developed an efficient and robust method for assessing the influence of current and next-generation stents on local hemodynamics and vascular biomechanics quantified by computational fluid dynamics. Stent designs were parameterized to allow easy control over design features including the number, width and circumferential or longitudinal spacing of struts, as well as the implantation diameter and overall length. The approach allowed stents to be automatically regenerated for rapid analysis of the contribution of design features to resulting hemodynamic alterations. The applicability of the method was demonstrated with patient-specific models of a stented coronary artery bifurcation and basilar trunk aneurysm constructed from medical imaging data. In the coronary bifurcation, we analyzed the hemodynamic difference between closed-cell and open-cell stent geometries. We investigated the impact of decreased strut size in stents with a constant porosity for increasing flow stasis within the stented basilar aneurysm model. These examples demonstrate the current method can be used to investigate differences in stent performance in complex vascular beds for a variety of stenting procedures and clinical scenarios.
View details for DOI 10.1007/s10439-010-0238-5
View details for Web of Science ID 000289243100005
View details for PubMedID 21203844
Computational Fluid Dynamic Simulations of Aortic Coarctation Comparing the Effects of Surgical- and Stent-Based Treatments on Aortic Compliance and Ventricular Workload CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS 2011; 77 (5): 680-691
In this work, we examine the effects of stent-induced aortic stiffness on cardiac workload and blood pressure using computational fluid dynamic simulations. Background: Treatment of aortic coarctation (CoA) consists of either open, surgical repair or angioplasty with or without stenting. Although stenting is a minimally invasive alternative to surgery, aortic stiffness increases in the stented section. Concern over this increased stiffness has long been argued to be detrimental to the overall vascular health of the patient.MR imaging was performed on a 15-year-old female with CoA. A 3D model of the large thoracic arteries was created, and the heart and downstream vasculature were represented by lumped parameter models at the model inlet and outlets, respectively. A deformable wall assumption was used in conjunction with variable wall properties and tissue support, and 3D velocity, pressure, and wall dynamics were computed. The lumped parameter values and wall properties were tuned to match the mean flow and aortic deformation as measured by MRI. The CoA was then virtually removed from the model representing an end-to-end surgical correction. In a second model, the repaired section was prescribed to be nearly rigid, representing stenting. All other variables remained the same.When compared to surgery, stenting resulted in clinically negligible increases in cardiac work (0.4%) and no change in mean blood pressure.This pilot study suggests CoA stenting may not affect cardiac work to any significant degree as is commonly believed in the clinical community.
View details for DOI 10.1002/ccd.22878
View details for Web of Science ID 000288793200019
View details for PubMedID 21061250
Three-Dimensional Hemodynamics in the Human Pulmonary Arteries Under Resting and Exercise Conditions ANNALS OF BIOMEDICAL ENGINEERING 2011; 39 (1): 347-358
The biomechanical forces associated with blood flow have been shown to play a role in pulmonary vascular cell health and disease. Therefore, the quantification of human pulmonary artery hemodynamic conditions under resting and exercise states can be useful in investigating the physiology of disease development and treatment outcomes. In this study, a combined magnetic resonance imaging and computational fluid dynamics approach was used to quantify pulsatile flow fields, wall shear stress (WSS), oscillations in WSS (OSI), and energy efficiency in six subject-specific models of the human pulmonary vasculature with high spatial and temporal resolution. Averaging over all subjects, WSS was found to increase from 19.84.0 to 51.86.7 dynes/cm2, and OSI was found to decrease from 0.0940.016 to 0.0810.015 in the proximal pulmonary arteries between rest and exercise conditions (p<0.05). These findings demonstrate the localized, biomechanical effects of exercise. Furthermore, an average decrease of 10% in energy efficiency was noted between rest and exercise. These data indicate the amount of energy dissipation that typically occurs with exercise and may be useful in future surgical planning applications.
View details for DOI 10.1007/s10439-010-0124-1
View details for Web of Science ID 000287213100030
View details for PubMedID 20640512
AORTIC COARCTATION: RECENT DEVELOPMENTS IN EXPERIMENTAL AND COMPUTATIONAL METHODS TO ASSESS TREATMENTS FOR THIS SIMPLE CONDITION. Progress in pediatric cardiology 2010; 30 (1): 45-49
Coarctation of the aorta (CoA) is often considered a relatively simple disease, but long-term outcomes suggest otherwise as life expectancies are decades less than in the average population and substantial morbidity often exists. What follows is an expanded version of collective work conducted by the authors' and numerous collaborators that was presented at the 1st International Conference on Computational Simulation in Congenital Heart Disease pertaining to recent advances for CoA. The work begins by focusing on what is known about blood flow, pressure and indices of wall shear stress (WSS) in patients with normal vascular anatomy from both clinical imaging and the use of computational fluid dynamics (CFD) techniques. Hemodynamic alterations observed in CFD studies from untreated CoA patients and those undergoing surgical or interventional treatment are subsequently discussed. The impact of surgical approach, stent design and valve morphology are also presented for these patient populations. Finally, recent work from a representative experimental animal model of CoA that may offer insight into proposed mechanisms of long-term morbidity in CoA is presented.
View details for PubMedID 21152106
Computational Simulation of the Pulmonary Arteries and its Role in the Study of Pediatric Pulmonary Hypertension. Progress in pediatric cardiology 2010; 30 (1-2): 63-69
The hemodynamic state of the pulmonary arteries is challenging to routinely measure in children due to the vascular circuit's position in the lungs. The resulting relative scarcity of quantitative clinical diagnostic and prognostic information impairs management of diseases such as pulmonary hypertension, or high blood pressure of the pulmonary circuit, and invites new techniques of measurement. Here we examine recent applications of macro-scale computational mechanics methods for fluids and solids - traditionally used by engineers in the design and virtual testing of complex metal and composite structures - applied to study the pulmonary vasculature, both in healthy and diseased states. In four subject areas, we briefly outline advances in computational methodology and provide examples of clinical relevance.
View details for PubMedID 21499523
Congenital extrahepatic portosystemic shunt associated with heterotaxy and polysplenia PEDIATRIC RADIOLOGY 2010; 40 (7): 1222-1230
Heterotaxy with polysplenia is associated with many cardiovascular anomalies including the occasional occurrence of congenital extrahepatic portosystemic shunts (CEPS). Missing this anomaly can lead to inappropriate and ineffective therapy.To emphasize the importance and associated anatomy of CEPS in conjunction with heterotaxy with polysplenia.Review of three young children who presented with cyanosis and pulmonary hypertension without a cardiac etiology. They were known (1) or discovered (2) to have heterotaxy with polysplenia.There was absence of the intrahepatic inferior vena cava (IVC) with azygos or hemiazygos continuation in all three cases. In spite of normal liver function, they were discovered to have large portosystemic shunts, splenorenal in location, along with diffuse peripheral pulmonary arterial dilatation suggestive of CEPS (Abernethy malformation) with hepatopulmonary or, more accurately, portopulmonary syndrome. All CEPS were ipsilateral to the spleens. Patency of the portal veins in these cases allowed for percutaneous shunt closure with resolution of cyanosis.CEPS is associated with heterotaxy with polysplenia and can be symptomatic because of pulmonary arteriovenous (AV) shunting. Portal and hepatic vein patency are critical for determining feasibility of CEPS closure.
View details for DOI 10.1007/s00247-009-1508-y
View details for Web of Science ID 000278582300007
View details for PubMedID 20069288
New Insights into Pacemaker Lead-Induced Venous Occlusion: Simulation-Based Investigation of Alterations in Venous Biomechanics CARDIOVASCULAR ENGINEERING 2010; 10 (2): 84-90
Venous obstruction is a major complication of transvenous pacemaker placement. Despite the increasing use of pacemakers and implantable cardiac defibrillators, a lack of understanding remains with regard to risk factors for the development of device-associated venous obstruction. We hypothesize that computational fluid dynamics simulations can reveal prothrombogenic locations and define thrombosis risk based on patient-specific anatomies. Using anatomic data derived from computed tomography, computer models of the superior vena cava, subclavian, innominate, and internal jugular veins were constructed for three adult patients with transvenous pacemakers. These models were used to perform patient-specific simulations examining blood flow velocity, wall shear stress, and blood pressure, both with and without the presence of the pacing leads. To better quantify stasis, mean exposure time fields were computed from the venous blood flow data. In comparing simulations with leads to those without, evident increases in stasis at locations between the leads and along the surface of the vessels closest to the leads were found. These locations correspond to regions at known risk for thrombosis. This work presents a novel application of computational methods to study blood flow changes induced by pacemaker leads and possible complications such as venous occlusion and thrombosis. This methodology may add to our understanding of the development of lead-induced thrombosis and occlusion in the clinical arena, and enable the development of new strategies to avoid such complications.
View details for DOI 10.1007/s10558-010-9096-x
View details for Web of Science ID 000278717400005
View details for PubMedID 20514553
Pulmonary Hypertension Associated With Congenital Heart Disease Pulmonary Vascular Disease: The Global Perspective CHEST 2010; 137 (6): 52S-61S
The incidence of congenital heart disease is approximately 8/1,000 live births and appears to be constant around the world. The currently accepted paradigm for the development of pulmonary vascular disease associated with congenital heart disease maintains that increased pulmonary blood flow and pressure trigger unfavorable vascular remodeling. Endothelial cell dysfunction, abnormal shear stress, circumferential wall stretch, and an imbalance in vasoactive mediators conspire to promote vasoconstriction, inflammation, thrombosis, cell proliferation, impaired apoptosis, and fibrosis. We estimate that worldwide 3 million children are at risk for the development of pulmonary vascular disease due to congenital heart disease. The majority of children at risk globally will have a reparable heart defect, such as an isolated atrial septal or ventricular septal defect or patent ductus arteriosus. Cardiac repair in the first 2 years of life would prevent the development of Eisenmenger syndrome, the most advanced form of pulmonary vascular disease secondary to congenital heart disease. Worldwide, only a small fraction of those at risk are offered surgical repair. Thus, access to timely medical care would eliminate the vast majority of suffering, disability, and death from Eisenmenger syndrome. Globally, pulmonary vascular disease associated with congenital heart disease may be the most preventable cause of pulmonary artery hypertension and related mortality and morbidity.
View details for DOI 10.1378/chest.09-2861
View details for Web of Science ID 000278561500007
View details for PubMedID 20522580
Majewski Osteodysplastic Primordial Dwarfism Type II (MOPD II): Expanding the Vascular Phenotype AMERICAN JOURNAL OF MEDICAL GENETICS PART A 2010; 152A (4): 960-965
Majewski Osteodysplastic Primordial Dwarfism, Type II (MOPD II) is a rare, autosomal recessive disorder. Features include severe intrauterine growth retardation (IUGR), poor postnatal growth (adult stature approximately 100 cm), severe microcephaly, skeletal dysplasia, characteristic facial features, and normal or near normal intelligence. An Institutional Review Board (IRB) approved registry was created and currently follows 25 patients with a diagnosis of MOPD II. Based on previous studies, a neurovascular screening program was implemented and 13 (52%) of these patients have been found to have cerebral neurovascular abnormalities including moyamoya angiopathy and/or intracranial aneurysms. The typical moyamoya pathogenesis begins with vessel narrowing in the supraclinoid internal carotid artery, anterior cerebral (A1) or middle cerebral (M1) artery segments. The narrowing may predominate initially on one side, progresses to bilateral stenosis, with subsequent occlusion of the vessels and collateral formation. We present four patients who, on neurovascular screening, were found to have cerebrovascular changes. Two were asymptomatic, one presented with a severe headache and projectile vomiting related to a ruptured aneurysm, and one presented after an apparent decline in cognitive functioning. Analysis of the registry suggests screening for moyamoya disease be performed at the time of MOPD II diagnosis and at least every 12-18 months using MRA or computerized tomographic angiography (CTA). We believe this is imperative. If diagnosed early enough, re-vascularization and aneurysm treatment in skilled hands can be performed safely and prevent or minimize long-term sequelae in this population. Emergent evaluation is also needed when other neurologic or cardiac symptoms are present.
View details for DOI 10.1002/ajmg.a.33252
View details for Web of Science ID 000276754000025
View details for PubMedID 20358609
A New Multiparameter Approach to Computational Simulation for Fontan Assessment and Redesign CONGENITAL HEART DISEASE 2010; 5 (2): 104-117
Despite an abundance of prior Fontan simulation articles, there have been relatively few clinical advances that are a direct result of computational methods. We address a few key limitations of previous Fontan simulations as a step towards increasing clinical relevance. Previous simulations have been limited in scope because they have primarily focused on a single energy loss parameter. We present a multi-parameter approach to Fontan modeling that establishes a platform for clinical decision making and comprehensive evaluation of proposed interventions.Time-dependent, 3-D blood flow simulations were performed on six patient-specific Fontan models. Key modeling advances include detailed pulmonary anatomy, catheterization-derived pressures, and MRI-derived flow with respiration. The following performance parameters were used to rank patients at rest and simulated exercise from best to worst performing: energy efficiency, inferior and superior vena cava (IVC, SVC) pressures, wall shear stress, and IVC flow distribution.Simulated pressures were well matched to catheterization data, but low Fontan pressure did not correlate with high efficiency. Efficiency varied from 74% to 96% at rest, and from 63% to 91% with exercise. Distribution of IVC flow ranged from 88%/12% (LPA/RPA) to 53%/47%. A "transcatheter" virtual intervention demonstrates the utility of computation in evaluating interventional strategies, and is shown to result in increased energy efficiency.A multiparameter approach demonstrates that each parameter results in a different ranking of Fontan performance. Ranking patients using energy efficiency does not correlate with the ranking using other parameters of presumed clinical importance. As such, current simulation methods that evaluate energy dissipation alone are not sufficient for a comprehensive evaluation of new Fontan designs.
View details for DOI 10.1111/j.1747-0803.2010.00383.x
View details for Web of Science ID 000289417500004
View details for PubMedID 20412482
Perioperative complications in children with pulmonary hypertension undergoing general anesthesia with ketamine PEDIATRIC ANESTHESIA 2010; 20 (1): 28-37
Pulmonary arterial hypertension (PAH) is associated with significant perioperative risk for major complications in children, including pulmonary hypertensive crisis and cardiac arrest. Uncertainty remains about the safety of ketamine anesthesia in this patient population.Retrospectively review the medical records of children with PAH to ascertain the nature and frequency of peri-procedural complications and to determine whether ketamine administration was associated with peri-procedural complications.Children with PAH (mean pulmonary artery pressure > or =25 mmHg and pulmonary vascular resistance index > or =3 Wood units) who underwent general anesthesia for procedures during a 6-year period (2002-2008) were enrolled. Details about the patient, PAH, procedure, anesthetic and postprocedural course were noted, including adverse events during or within 48 h of the procedure. Complication rates were reported per procedure. Association between ketamine and peri-procedural complications was tested.Sixty-eight children (median age 7.3 year, median weight 22 kg) underwent 192 procedures. Severity of PAH was mild (23%), moderate (37%), and severe (40%). Procedures undertaken were major surgery (n = 20), minor surgery (n = 27), cardiac catheterization (n = 128) and nonsurgical procedures (n = 17). Ketamine was administered during 149 procedures. Twenty minor and nine major complications were noted. Incidence of cardiac arrest was 0.78% for cardiac catheterization procedures, 10% for major surgical procedures and 1.6% for all procedures. There was no procedure-related mortality. Ketamine administration was not associated with increased complications.Ketamine appears to be a safe anesthetic option for children with PAH. We report rates for cardiopulmonary resuscitation and mortality that are more favorable than those previously reported.
View details for DOI 10.1111/j.1460-9592.2009.03166.x
View details for Web of Science ID 000273525800004
View details for PubMedID 20078799
VIRTUAL DESIGN FOR THE FONTAN PROCEDURE: FROM IDEALIZED TO PATIENT SPECIFIC MODELS USING CFD AND DERIVATIVE-FREE OPTIMIZATION PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, 2010 2010: 425-426
A COMPUTATIONAL FRAMEWORK FOR OPTIMIZATION AND UNCERTAINTY QUANTIFICATION IN SURGICAL DESIGN FOR PEDIATRIC CARDIOLOGY PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE, 2010 2010: 249-250
Constrained optimization of an idealized Y-shaped baffle for the Fontan surgery at rest and exercise COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2010; 199 (33-36): 2135-2149
Pulmonary arterial hypertension in children: Diagnostic work-up and challenges. Progress in pediatric cardiology 2009; 27 (1): 4-11
The diagnostic evaluation of a pediatric patient with suspected pulmonary arterial hypertension (PAH) is extensive but essential, given the rapid progression of the disease if left undiagnosed and untreated. The major goals of performing a complete diagnostic work-up are to confirm the diagnosis of PAH, assess disease severity, rule out associated diseases, and begin to formulate an individualized treatment plan for the pediatric patient with pulmonary hypertension. This article will provide a comprehensive review of the diagnostic work-up of the child with suspected PAH as well as a review of some of the challenges faced when assessing a child for PAH.
View details for PubMedID 21691442
Non-congenital heart disease associated pediatric pulmonary arterial hypertension. Progress in pediatric cardiology 2009; 27 (1-2): 13-23
Recognition of causes of pulmonary hypertension other than congenital heart disease is increasing in children. Diagnosis and treatment of any underlying cause of pulmonary hypertension is crucial for optimal management of pulmonary hypertension. This article discusses the available knowledge regarding several disorders associated with pulmonary hypertension in children: idiopathic pulmonary arterial hypertension (IPAH), pulmonary capillary hemangiomatosis, pulmonary veno-occlusive disease, hemoglobinopathies, hepatopulmonary syndrome, portopulmonary hypertension and HIV. Three classes of drugs have been extensively studied for the treatment of IPAH in adults: prostanoids (epoprostenol, treprostinil, iloprost, beraprost), endothelin receptor antagonists (bosentan, sitaxsentan, ambrisentan), and phosphodiesterase inhibitors (Sildenafil, tadalafil). These medications have been used in treatment of children with pulmonary arterial hypertension, although randomized clinical trial data is lacking. As pulmonary vasodilator therapy in certain diseases may be associated with adverse outcomes, further study of these medications is needed before widespread use is encouraged.
View details for PubMedID 21852894
On Coupling a Lumped Parameter Heart Model and a Three-Dimensional Finite Element Aorta Model ANNALS OF BIOMEDICAL ENGINEERING 2009; 37 (11): 2153-2169
Aortic flow and pressure result from the interactions between the heart and arterial system. In this work, we considered these interactions by utilizing a lumped parameter heart model as an inflow boundary condition for three-dimensional finite element simulations of aortic blood flow and vessel wall dynamics. The ventricular pressure-volume behavior of the lumped parameter heart model is approximated using a time varying elastance function scaled from a normalized elastance function. When the aortic valve is open, the coupled multidomain method is used to strongly couple the lumped parameter heart model and three-dimensional arterial models and compute ventricular volume, ventricular pressure, aortic flow, and aortic pressure. The shape of the velocity profiles of the inlet boundary and the outlet boundaries that experience retrograde flow are constrained to achieve a robust algorithm. When the aortic valve is closed, the inflow boundary condition is switched to a zero velocity Dirichlet condition. With this method, we obtain physiologically realistic aortic flow and pressure waveforms. We demonstrate this method in a patient-specific model of a normal human thoracic aorta under rest and exercise conditions and an aortic coarctation model under pre- and post-interventions.
View details for DOI 10.1007/s10439-009-9760-8
View details for Web of Science ID 000270448300001
View details for PubMedID 19609676
ACC 2009 Survey Results and Recommendations: Addressing the Cardiology Workforce Crisis A Report of the ACC Board of Trustees Workforce Task Force JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY 2009; 54 (13): 1195-1208
Use of magnetic resonance imaging and computed tomography CARDIOLOGY IN THE YOUNG 2009; 19: 16-22
A Novel Non-Invasive Method of Estimating Pulmonary Vascular Resistance in Patients With Pulmonary Arterial Hypertension JOURNAL OF THE AMERICAN SOCIETY OF ECHOCARDIOGRAPHY 2009; 22 (5): 523-529
The assessment of pulmonary vascular resistance (PVR) plays an important role in the diagnosis and management of pulmonary arterial hypertension (PAH). The main objective of this study was to determine whether the noninvasive index of systolic pulmonary arterial pressure (SPAP) to heart rate (HR) times the right ventricular outflow tract time-velocity integral (TVI(RVOT)) (SPAP/[HR x TVI(RVOT)]) provides clinically useful estimations of PVR in PAH.Doppler echocardiography and right-heart catheterization were performed in 51 consecutive patients with established PAH. The ratio of SPAP/(HR x TVI(RVOT)) was then correlated with invasive indexed PVR (PVRI) using regression and Bland-Altman analysis. Using receiver operating characteristic curve analysis, a cutoff value for the Doppler equation was generated to identify patients with PVRI > or = 15 Wood units (WU)/m2.The mean pulmonary arterial pressure was 52 +/- 15 mm Hg, the mean cardiac index was 2.2 +/- 0.6 L/min/m2, and the mean PVRI was 20.5 +/- 9.6 WU/m2. The ratio of SPAP/(HR x TVI(RVOT)) correlated very well with invasive PVRI measurements (r = 0.860; 95% confidence interval, 0.759-0.920). A cutoff value of 0.076 provided well-balanced sensitivity (86%) and specificity (82%) to determine PVRI > 15 WU/m2. A cutoff value of 0.057 increased sensitivity to 97% and decreased specificity to 65%.The novel index of SPAP/(HR x TVI(RVOT)) provides useful estimations of PVRI in patients with PAH.
View details for DOI 10.1016/j.echo.2009.01.021
View details for Web of Science ID 000266091400017
View details for PubMedID 19307098
Short- and Long-Term Outcomes of Necrotizing Enterocolitis in Infants With Congenital Heart Disease PEDIATRICS 2009; 123 (5): E901-E906
Congenital heart disease is a significant risk factor for necrotizing enterocolitis in the term infant. We compared the short- and long-term necrotizing enterocolitis-specific outcomes of infants with congenital heart disease with those of neonates without congenital heart disease.A retrospective study of 202 patients with necrotizing enterocolitis treated at our center from May 1999 to August 2007 was conducted. Infants with necrotizing enterocolitis were grouped according to the presence (n = 76) or absence (n = 126) of congenital heart disease. Demographic and necrotizing enterocolitis-specific outcomes were recorded. The groups were compared by nonparametric and chi(2) analyses. Univariate and multivariate odds ratios were determined for each outcome.The average birth weight and gestational age of the 2 groups were not significantly different. The initial necrotizing enterocolitis severity, as determined by Bell stage, was less for necrotizing enterocolitis subjects with congenital heart disease compared with those without congenital heart disease. When controlling for birth weight and gestational age, the congenital heart disease group had decreased risk of perforation, need for a bowel operation, strictures, need for a stoma, sepsis, and short bowel syndrome compared with the non-congenital heart disease group. Although not statistically significant, subjects with congenital heart disease had a trend toward decreased risk of death from necrotizing enterocolitis, recurrent necrotizing enterocolitis, and need for peritoneal drainage.Infants with congenital heart disease and necrotizing enterocolitis have decreased risk of major short- and long-term negative outcomes associated with necrotizing enterocolitis compared with neonates without congenital heart disease. Differences in initial severity, range of age at diagnosis, and prognoses between subjects with necrotizing enterocolitis with and without cardiac disease suggest that necrotizing enterocolitis in the cardiac patient is a distinct disease process and should be labeled cardiogenic necrotizing enterocolitis.
View details for DOI 10.1542/peds.2008-3216
View details for Web of Science ID 000265528900048
View details for PubMedID 19403484
Angina Associated With Left Main Coronary Artery Compression in Pulmonary Hypertension JOURNAL OF HEART AND LUNG TRANSPLANTATION 2009; 28 (5): 527-530
Chest pain is a common complaint in patients with pulmonary arterial hypertension (PAH). Left main coronary artery (LMCA) compression by an enlarged pulmonary artery trunk (PAT) has been associated with angina, but appropriate diagnostic and treatment approaches remain poorly defined. We present two cases of angina caused by LMCA compression from an enlarged pulmonary artery, one of which also presented with new, severe left ventricular systolic dysfunction attributed to myocardial ischemia. Diagnosis of LMCA stenosis was made via coronary angiography followed by computed tomography-gated coronary angiography (CT-CA), which confirmed pulmonary artery enlargement as the source of extrinsic compression. Restoring LMCA patency with percutaneous intervention and/or aggressive treatment of pulmonary hypertension led to significant improvement in angina, cardiac function and quality of life. Given the negative impact on cardiac function, prompt diagnosis and treatment of extrinsic LMCA compression should be considered a priority.
View details for DOI 10.1016/j.healun.2008.12.008
View details for Web of Science ID 000266171400021
View details for PubMedID 19416787
Evaluation of a novel Y-shaped extracardiac Fontan baffle using computational fluid dynamics JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 2009; 137 (2): 394-U187
The objective of this work is to evaluate the hemodynamic performance of a new Y-graft modification of the extracardiac conduit Fontan operation. The performance of the Y-graft design is compared to two designs used in current practice: a t-junction connection of the venae cavae and an offset between the inferior and superior venae cavae.The proposed design replaces the current tube grafts used to connect the inferior vena cava to the pulmonary arteries with a Y-shaped graft. Y-graft hemodynamics were evaluated at rest and during exercise with a patient-specific model from magnetic resonance imaging data together with computational fluid dynamics. Four clinically motivated performance measures were examined: Fontan pressures, energy efficiency, inferior vena cava flow distribution, and wall shear stress. Two variants of the Y-graft were evaluated: an "off-the-shelf" graft with 9-mm branches and an "area-preserving" graft with 12-mm branches.Energy efficiency of the 12-mm Y-graft was higher than all other models at rest and during exercise, and the reduction in efficiency from rest to exercise was improved by 38%. Both Y-graft designs reduced superior vena cava pressures during exercise by as much as 5 mm Hg. The Y-graft more equally distributed the inferior vena cava flow to both lungs, whereas the offset design skewed 70% of the flow to the left lung. The 12-mm graft resulted in slightly larger regions of low wall shear stress than other models; however, minimum shear stress values were similar.The area-preserving 12-mm Y-graft is a promising modification of the Fontan procedure that should be clinically evaluated. Further work is needed to correlate our performance metrics with clinical outcomes, including exercise intolerance, incidence of protein-losing enteropathy, and thrombus formation.
View details for DOI 10.1016/j.jtcvs.2008.06.043
View details for Web of Science ID 000262919000020
View details for PubMedID 19185159
OPTIMIZATION OF AN IDEALIZED Y-GRAFT FOR THE FONTAN PROCEDURE USING CFD AND A DERIVATIVE-FREE OPTIMIZATION ALGORITHM PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B 2009: 449-450
A COMPUTATIONAL TECHNIQUE FOR UNCERTAINTY QUANTIFICATION AND ROBUST DESIGN IN CARDIOVASCULAR SYSTEMS PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2009, PT A AND B 2009: 17-18
Evaluation, risk stratification, and management of pulmonary hypertension in patients with congenital heart disease. Seminars in thoracic and cardiovascular surgery. Pediatric cardiac surgery annual 2009: 106-111
Surgical outcomes for patients with congenital heart disease have improved dramatically over the past few decades due, in part, to improvements in preoperative and postoperative management, cardiopulmonary bypass and intraoperative technique, and the development of pediatric cardiology as a subspecialty. Patients with pulmonary hypertension, however, remain a particularly challenging subgroup worldwide. Determination of operability and, when reasonable, timing of surgery, remains at times difficult. An overview of the evaluation process for this patient population is presented along with a review of evidence for risk stratification and a generalized account of the current state of medical therapy.
View details for DOI 10.1053/j.pcsu.2009.01.010
View details for PubMedID 19349023
A TECHNIQUE FOR QUANTITATIVE CHARACTERIZATION OF PULMONARY VASCULAR MORPHOLOGY AND APPLICATION IN A NORMAL RAT PROCEEDINGS OF THE ASME SUMMER BIOENGINEERING CONFERENCE 2008, PTS A AND B 2009: 309-310
Extension of Doppler-derived echocardiographic measures of pulmonary vascular resistance to patients with moderate or severe pulmonary vascular disease JOURNAL OF THE AMERICAN SOCIETY OF ECHOCARDIOGRAPHY 2008; 21 (6): 711-714
Pulmonary vascular resistance (PVR) is a critical parameter in the assessment and treatment of patients with pulmonary hypertension, regardless of origin. Noninvasive estimation of PVR could be helpful.Consecutive patients with known or suggested pulmonary hypertension referred for cardiac catheterization were evaluated prospectively and the PVR was calculated invasively. Subsequently, the tricuspid regurgitation velocity (TRV), the velocity-time integral (mean of 3 measurements) of the right ventricular outflow tract (VTIm), and the right ventricular outflow tract diameter were recorded noninvasively.The TRV/VTIm ratio and the TRV/VTIm corrected for the indexed RVOT diameter correlated well with the PVR at catheterization with R(2) = 0.711 and R(2) = 0.731, respectively, including patients with very high values of PVR. A TRV/VTI(RVOT) value of 38 provided a specificity of 100% for a PVR of 8 Woods units.Noninvasive estimation is feasible over a broad range of PVR values and could be a useful tool to estimate and longitudinally tracked changes in PVR.
View details for DOI 10.1016/j.echo.2007.10.004
View details for Web of Science ID 000256283900008
View details for PubMedID 18187297
A computational framework for derivative-free optimization of cardiovascular geometries COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2008; 197 (21-24): 1890-1905
Ketamine does not increase pulmonary vascular resistance in children with pulmonary hypertension undergoing sevoflurane anesthesia and spontaneous ventilation ANESTHESIA AND ANALGESIA 2007; 105 (6): 1578-1584
The use of ketamine in children with increased pulmonary vascular resistance is controversial. In this prospective, open label study, we evaluated the hemodynamic responses to ketamine in children with pulmonary hypertension (mean pulmonary artery pressure >25 mm Hg).Children aged 3 mo to 18 yr with pulmonary hypertension, who were scheduled for cardiac catheterization with general anesthesia, were studied. Patients were anesthetized with sevoflurane (1 minimum alveolar anesthetic concentration [MAC]) in air while breathing spontaneously via a facemask. After baseline catheterization measurements, sevoflurane was reduced (0.5 MAC) and ketamine (2 mg/kg IV over 5 min) was administered, followed by a ketamine infusion (10 microg x kg(-1) x min(-1)). Catheterization measurements were repeated at 5, 10, and 15 min after completion of ketamine load. Data at various time points were compared (ANOVA, P < 0.05).Fifteen patients (age 147, 108 mo; median, interquartile range) were studied. Diagnoses included idiopathic pulmonary arterial hypertension (5), congenital heart disease (9), and diaphragmatic hernia (1). At baseline, median (interquartile range) baseline pulmonary vascular resistance index was 11.3 (8.2) Wood units; 33% of patients had suprasystemic mean pulmonary artery pressures. Heart rate (99, 94 bpm; P = 0.016) and Pao2 (95, 104 mm Hg; P = 007) changed after ketamine administration (baseline, 15 min after ketamine; P value). There were no significant differences in mean systemic arterial blood pressure, mean pulmonary artery pressure, systemic or pulmonary vascular resistance index, cardiac index, arterial pH, or Paco2.In the presence of sevoflurane, ketamine did not increase pulmonary vascular resistance in spontaneously breathing children with severe pulmonary hypertension.
View details for DOI 10.1213/01.ane.0000287656.29064.89
View details for Web of Science ID 000251274400014
View details for PubMedID 18042853
Noninherited risk factors and congenital cardiovascular defects: Current knowledge a scientific statement from the American Heart Association Council on cardiovascular disease in the young CIRCULATION 2007; 115 (23): 2995-3014
Prevention of congenital cardiovascular defects has been hampered by a lack of information about modifiable risk factors for abnormalities in cardiac development. Over the past decade, there have been major breakthroughs in the understanding of inherited causes of congenital heart disease, including the identification of specific genetic abnormalities for some types of malformations. Although relatively less information has been available on noninherited modifiable factors that may have an adverse effect on the fetal heart, there is a growing body of epidemiological literature on this topic. This statement summarizes the currently available literature on potential fetal exposures that might alter risk for cardiovascular defects. Information is summarized for periconceptional multivitamin or folic acid intake, which may reduce the risk of cardiac disease in the fetus, and for additional types of potential exposures that may increase the risk, including maternal illnesses, maternal therapeutic and nontherapeutic drug exposures, environmental exposures, and paternal exposures. Information is highlighted regarding definitive risk factors such as maternal rubella; phenylketonuria; pregestational diabetes; exposure to thalidomide, vitamin A cogeners, or retinoids; and indomethacin tocolysis. Caveats regarding interpretation of possible exposure-outcome relationships from case-control studies are given because this type of study has provided most of the available information. Guidelines for prospective parents that could reduce the likelihood that their child will have a major cardiac malformation are given. Issues related to pregnancy monitoring are discussed. Knowledge gaps and future sources of new information on risk factors are described.
View details for DOI 10.1161/CIRCULATIONAHA.106.183216
View details for Web of Science ID 000247153300015
View details for PubMedID 17519397
Morphometry-based impedance boundary conditions for patient-specific modeling of blood flow in pulmonary arteries ANNALS OF BIOMEDICAL ENGINEERING 2007; 35 (4): 546-559
Patient-specific computational models could aid in planning interventions to relieve pulmonary arterial stenoses common in many forms of congenital heart disease. We describe a new approach to simulate blood flow in subject-specific models of the pulmonary arteries that consists of a numerical model of the proximal pulmonary arteries created from three-dimensional medical imaging data with terminal impedance boundary conditions derived from linear wave propagation theory applied to morphometric models of distal vessels. A tuning method, employing numerical solution methods for nonlinear systems of equations, was developed to modify the distal vasculature to match measured pressure and flow distribution data. One-dimensional blood flow equations were solved with a finite element method in image-based pulmonary arterial models using prescribed inlet flow and morphometry-based impedance at the outlets. Application of these methods in a pilot study of the effect of removal of unilateral pulmonary arterial stenosis induced in a pig showed good agreement with experimental measurements for flow redistribution and main pulmonary arterial pressure. Next, these methods were applied to a patient with repaired tetralogy of Fallot and predicted insignificant hemodynamic improvement with relief of the stenosis. This method of coupling image-based and morphometry-based models could enable increased fidelity in pulmonary hemodynamic simulation.
View details for DOI 10.1007/s10439-006-9240-3
View details for Web of Science ID 000245078300005
View details for PubMedID 17294117
Noninvasive assessment of pulmonary arterial capacitance by echocardiography JOURNAL OF THE AMERICAN SOCIETY OF ECHOCARDIOGRAPHY 2007; 20 (2): 186-190
Pulmonary arterial capacitance (PAC) has been associated with right ventricular (RV) workload and mortality in pulmonary hypertension, but is not routinely evaluated in children. We investigated whether PAC can be estimated noninvasively by echocardiography.We retrospectively determined PAC in 31 children with pulmonary hypertension, using echocardiography, and compared the results with those obtained at cardiac catheterization.PAC derived from echocardiography was similar to that derived from catheterization (mean +/- SD 1.16 +/- 1.0 vs 1.10 +/- 0.95 mL(3) x mm Hg(-1), P = not significant) and the two correlated well (r = 0.74, P < .0001). There was a highly significant polynomial relationship between PAC and RV anterior wall thickness indexed to body surface area (R(2) = 0.54, P < .0001), but not between pulmonary vascular resistance and RV wall thickness. Pulmonary vascular resistance and PAC did not correlate.Echocardiography can reliably estimate PAC, which strongly correlates with RV hypertrophy, a surrogate for RV work.
View details for DOI 10.1016/j.echo.2006.08.009
View details for Web of Science ID 000244162000013
View details for PubMedID 17275705
Effects of exercise and respiration on hemodynamic efficiency in CFD simulations of the total cavopulmonary connection ANNALS OF BIOMEDICAL ENGINEERING 2007; 35 (2): 250-263
Congenital heart defects with a single functional ventricle, such as hypoplastic left heart syndrome and tricuspid atresia, require a staged surgical approach to separate the systemic and pulmonary circulations. Ultimately, the venous or pulmonary side of the heart is bypassed by directly connecting the vena cava to the pulmonary arteries with a modified t-shaped junction. The Fontan procedure (total cavopulmonary connection, TCPC) completes this process of separation. To date, computational fluid dynamics (CFD) simulations in this low pressure, passive flow, intrathoracic system have neglected the presumed important effects of respiration on physiology and higher "stress" states such as with exercise have never been considered. We hypothesize that incorporating effects of respiration and exercise would provide more realistic estimates of TCPC performance. Time-dependent, 3D blood flow simulations are performed by a custom finite element solver for two patient-specific Fontan models with a novel respiration model, developed to generate physiologic time-varying flow conditions. Blood flow features, pressure, and energy efficiency are analyzed at rest and with increasing flow rates to simulate exercise conditions. The simulations produce realistic pressure and flow data, comparable to that measured by catheterization and echocardiography, and demonstrate substantial increases in energy dissipation (i.e. decreased performance) with exercise and respiration due to increasing intensity of small scale vortices in the flow. As would be expected, these changes are highly dependent on patient-specific anatomy and Fontan geometry. We propose that respiration and exercise should be incorporated into TCPC CFD simulations to provide increasingly realistic evaluations of TCPC performance.
View details for DOI 10.1007/s10439-006-9224-3
View details for Web of Science ID 000243471200008
View details for PubMedID 17171509
Evaluation of hemodynamic efficiency in a new "Y-graft" design for the Fontan operation PROCEEDING OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2007 2007: 473-474
Use of computational fluid dynamics for the replication of clinical blood flow and pressure measurements and characterization of hemodynamics in the normal ascending and thoracic aorta PROCEEDING OF THE ASME SUMMER BIOENGINEERING CONFERENCE - 2007 2007: 511-512
Percutaneous translurninal coronary angioplasty in a two-month old with coronary stenosis presenting as congenital cardiomyopathy: Acute results and intermediate follow-up CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS 2006; 68 (4): 632-636
Congenital or nonsurgically acquired obstructive coronary artery disease in infancy is exceedingly rare, and previous reports of catheter-based therapies in very young patients have been solely in patients having undergone arterial switch or other cardiovascular surgical procedures. We describe a previously unreported cause for ventricular dysfunction and heart failure in an infant, isolated congenital circumflex coronary artery stenosis, and successful treatment with percutaneous transluminal coronary angioplasty. Technical considerations, immediate results, and 3-year follow-up are provided.
View details for DOI 10.1002/ccd.20750
View details for Web of Science ID 000241048000023
View details for PubMedID 16969876
Unifocalization of major aortopulmonary collaterals in single-ventricle patients ANNALS OF THORACIC SURGERY 2006; 82 (3): 934-939
Unifocalization of major aortopulmonary collateral arteries (MAPCAs) in pulmonary atresia with ventricular septal defect and intracardiac repair has become the standard of care. However, there are no reports addressing unifocalization of MAPCAs in single-ventricle patients. It is unknown whether their pulmonary vascular bed can be reconstructed and low enough pulmonary vascular resistance achieved to allow for superior or total cavopulmonary connections.We reviewed data on all patients with functional single ventricles and unifocalization procedures of MAPCAs. From 1997 to 2005, 14 consecutive children with various single-ventricle anatomies were operated on.Patients had a median of three surgical procedures (range, 1 to 5). Two patients had absent, all others diminutive central pulmonary arteries, with an average of 3.5 +/- 1.2 MAPCAs. Seven patients (50%) had bidirectional Glenn procedures, and 3 of these had Fontan procedures. Median postoperative pulmonary artery pressures measured 12.5 mm Hg (Glenn) and 14 mm Hg (Fontan), respectively. Six patients are alive today (46%), with 1 patient lost to follow-up. Three patients died early and 3 late after initial unifocalization to shunts. One other patient survived unifocalization, but was not considered a candidate for a Glenn procedure and died after high-risk two-ventricle repair. Another patient with right-ventricle-dependent coronary circulation died of sepsis late after Glenn.In selected patients with functional single ventricles and MAPCAs, the pulmonary vascular bed can be reconstructed sufficiently to allow for cavopulmonary connections. Venous flow to the pulmonary vasculature decreases cardiac volume load and is likely to increase life expectancy and quality of life for these patients.
View details for DOI 10.1016/j.athoracsur.2006.03.063
View details for Web of Science ID 000239996300025
View details for PubMedID 16928512
Relative lung perfusion distribution in normal lung scans: observations and clinical implications. Congenital heart disease 2006; 1 (5): 210-216
While relative lung perfusion distributions are cited in clinical decision making for congenital and acquired pulmonary vascular diseases, normal values and ranges have not been published for a large population of normally perfused lungs. These values of normal relative perfusion will be useful for establishing what is abnormal and for clinical decisions related to various pulmonary vascular diseases.Relative perfusion distributions were quantified for the top, middle, and bottom thirds of the right and left lungs with a semiautomatic algorithm in 206 normal scintigraphy lung studies (45 +/- 18 years, 149 female, 57 male) acquired between January 1, 2000 and March 30, 2004 in the Nuclear Medicine Division at Stanford Hospital and Clinics.The perfusion data were found to be highly non-Gaussian in nature (necessitating the use of Wilcoxon statistical comparisons), and the right/left perfusion ratio was found to be 52.5/47.5 (+/-2.1%) rather than the often quoted 55/45 split. While this right/left split was consistent between the genders, males had proportionally less perfusion in the lower left lung as compared with females (P < .05).The long-standing 55/45 right/left perfusion ratio assumption was found to be more than 1 standard deviation greater than the mean, and the population variance is very small. Relative pulmonary perfusion distribution varies significantly with lung region, gender, and age, and should be considered when making clinical decisions based on pulmonary perfusion.
View details for DOI 10.1111/j.1747-0803.2006.00037.x
View details for PubMedID 18377528
A novel echocardiographic Doppler method for estimation of pulmonary arterial pressures JOURNAL OF THE AMERICAN SOCIETY OF ECHOCARDIOGRAPHY 2006; 19 (5): 559-562
Current noninvasive methods for estimating diastolic and mean pulmonary artery pressures (PAp) in children are cumbersome and have limited accuracy. We hypothesized that systolic PAp correlates with diastolic and mean PAp, and that this correlation can be used to estimate diastolic and mean PAp from Doppler flow data.We recorded PAp in 112 patients 30 years or younger catheterized for heart failure, heart transplant, pulmonary hypertension, or congenital heart disease. We derived the relationship of systolic PAp to diastolic and mean PAp. We then applied these relations to systolic PAp measured by tricuspid regurgitation (TR) Doppler flow in a subset of 17 patients with pulmonary hypertension to predict mean and diastolic PAp, and correlated the results.An excellent linear relation was found between systolic PAp and both the diastolic and mean PAp measured at cardiac catheterization (r = 0.95, P < .0001; r = 0.98, P < .0001, respectively). The calculated diastolic PAp calculated from TR Doppler correlated well with invasive data (31 +/- 13 vs 30 +/- 11 mm Hg, respectively, not significant; r = 0.85, P < .0001) and surpassed existing methods that are based on pulmonary regurgitation for predicting diastolic PAp. Similarly, mean PAp calculated from TR Doppler flow correlated well with invasive data (r = 0.86, P < .0001).A strong linear relationship between systolic and diastolic PAp allows for easy and accurate noninvasive estimation of diastolic and mean PAp from TR Doppler flow.
View details for DOI 10.1016/j.echo.2005.12.020
View details for Web of Science ID 000237488600014
View details for PubMedID 16644441
Percutaneous pulmonary valve placement in a 10-month-old patient using a hand crafted stent-mounte d porcine valve CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS 2006; 67 (4): 644-649
Percutaneous replacement of the pulmonary valve in a right ventricle to pulmonary artery (RV-PA) conduit using bovine jugular valves has recently been described as an alternative to surgical options in selected patients weighing >or=20 kg. We report the first case of transcatheter pulmonary valve implantation in an infant and the first use of "off the shelf" components. A 12-mm (Hancock) porcine valve was sutured into a predilated Genesis 2510b stent. The valved stent was manually crimped and mounted on a 12-mm balloon. Snare-assisted deployment in the middle of the RV-PA conduit was accomplished without the use of a long sheath. After the initial deployment, a 14-mm balloon was used to further approximate the stent to the walls of the conduit. Short-term (11 month) follow-up has demonstrated continued valve integrity, markedly decreased right ventricular size and improved function and symptomatic improvement. At 10 months of age, this case represents the youngest patient to undergo percutaneous valve placement and documents the technical feasibility of the procedure.
View details for DOI 10.1002/ccd.20668
View details for Web of Science ID 000236724200024
View details for PubMedID 16532496
AngioJet catheter-based thrombectomy in a neonate with postoperative pulmonary embolism CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS 2005; 66 (3): 442-445
A 2-day-old male with pulmonary atresia and an intact ventricular septum underwent central aortopulmonary shunt placement and right ventricular outflow tract reconstruction. Postoperatively, the patient had difficulty weaning from mechanical ventilation and was found to have a large thrombus occluding the entire right lower pulmonary artery. The patient underwent successful percutaneous catheter-based thrombectomy in the early postoperative period with the Possis AngioJet catheter. The patient had immediate improvement in gas exchange and was able to be weaned from the ventilator shortly thereafter. This represents the first published use of mechanical thrombectomy in a postoperative neonate.
View details for DOI 10.1002/ccd.20518
View details for Web of Science ID 000233106700025
View details for PubMedID 16216022
Surgical and interventional therapies for pulmonary arterial hypertension SEMINARS IN RESPIRATORY AND CRITICAL CARE MEDICINE 2005; 26 (4): 417-428
Surgical and interventional therapies for pulmonary arterial hypertension (PAH) in appropriately selected patients have the potential to dramatically improve or, in some cases, cure PAH. These include atrial septostomy, a palliative procedure or bridge to transplantation in patients with refractory right heart failure, pulmonary thromboendarterectomy for pulmonary hypertension associated with chronic thromboembolic disease, and closure of congenital systemic-pulmonary shunts in patients with PAH but without significant pulmonary vascular disease. Lung transplantation should be considered for patients with all forms of PAH who demonstrate advanced or progressive disease.
View details for Web of Science ID 000231671900010
View details for PubMedID 16121319
Experience of percutaneous coronary intervention in the management of pediatric cardiac allograft vasculopathy JOURNAL OF HEART AND LUNG TRANSPLANTATION 2005; 24 (6): 769-773
In a retrospective study, we examined the procedural success rate and the short-, intermediate-, and long-term outcomes of coronary interventional procedures in children with cardiac allograft vasculopathy. Seven patients underwent 13 interventional procedures: balloon angioplasty alone (n = 3), angioplasty with stenting (n = 9), or angioplasty with brachytherapy (n = 1), with procedural success in all. Two major complications (cardiac arrest) and a single death occurred in the immediate postprocedural period. Five (83%) of the remaining 6 patients developed moderate to severe restenosis, diffuse disease, or progressive vasculopathy; 3 have been retransplanted, 1 died from progressive cardiac allograft vasculopathy, and 1 is awaiting retransplantation, 40 months after the procedure.
View details for DOI 10.1016/j.healun.2004.04.009
View details for Web of Science ID 000229869700018
View details for PubMedID 15949739
Proximal pulmonary artery blood flow characteristics in healthy subjects measured in an upright posture using MRI: The effects of exercise and age JOURNAL OF MAGNETIC RESONANCE IMAGING 2005; 21 (6): 752-758
To use MRI to quantify blood flow conditions in the proximal pulmonary arteries of healthy children and adults at rest and during exercise in an upright posture.Cine phase-contrast MRI was used to calculate mean flow and reverse flow index (RFI) in the main (MPA), right (RPA), and left (LPA) pulmonary arteries in healthy children and adults in an open-MRI magnet equipped with an upright MRI-compatible ergometer.From rest to exercise (150% resting heart rate), blood flow (liters/minute/m2) increased in the RPA (1.4+/-0.3 vs. 2.5+/-0.4; P<0.001), LPA (1.1+/-0.3 vs. 2.2+/-0.6; P<0.001), and MPA (2.7+/-0.5 vs. 4.9+/-0.5; P<0.001). RFI decreased in the LPA (0.040+/-0.030 vs. 0.017+/-0.018; P<0.02) and MPA (0.025+/-0.024 vs. 0.008+/-0.007; P<0.03). Adults experienced greater retrograde flow in the MPA than the children (0.042+/-0.029 vs. 0.014+/-0.012; P<0.02).It appears that at both rest and during exercise, in children and adults alike, RPA/LPA mean blood flow distribution is predominantly determined by distal vascular resistance, while retrograde flow is affected by proximal pulmonary bifurcation geometry.
View details for DOI 10.1002/jmri.20333
View details for Web of Science ID 000229453900012
View details for PubMedID 15906332
Blood flow conditions in the proximal pulmonary arteries and vena cavae: healthy children during upright cycling exercise AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY 2004; 287 (2): H921-H926
Diagnostic testing in patients with congenital heart disease is usually performed supine and at rest, conditions not representative of their typical hemodynamics. Upright exercise measurements of blood flow may prove valuable in the assessment of these patients, but data in normal subjects are first required. With the use of a 0.5-T open magnet, a magnetic resonance-compatible exercise cycle, and cine phase-contrast techniques, time-dependent blood flow velocities were measured in the right (RPA), left (LPA), and main (MPA) pulmonary arteries and superior (SVC) and inferior (IVC) vena cavae of 10 healthy 10- to 14-yr-old subjects. Measurements were made at seated rest and during upright cycling exercise (150% resting heart rate). Mean blood flow (l/min) and reverse flow index were computed from the velocity data. With exercise, RPA and LPA mean flow increased 2.0 +/- 0.5 to 3.7 +/- 0.7 (P < 0.05) and 1.6 +/- 0.4 to 2.9 +/- 0.8 (P < 0.05), respectively. Pulmonary reverse flow index (rest vs. exercise) decreased with exercise as follows: MPA: 0.014 +/- 0.012 vs. 0.006 +/- 0.006 [P = not significant (NS)], RPA: 0.005 +/- 0.004 vs. 0.000 +/- 0.000 (P < 0.05), and LPA: 0.041 +/- 0.019 vs. 0.014 +/- 0.016 (P < 0.05). SVC and IVC flow increased from 1.5 +/- 0.2 to 1.9 +/- 0.6 (P = NS) and 1.6 +/- 0.4 to 4.9 +/- 1.3 (P < 0.05), respectively. A 56/44% RPA/LPA flow distribution at both rest and during exercise suggests blood flow distribution is dominated by distal pulmonary resistance. Reverse flow in the MPA appears to originate solely from the LPA while the RPA is in relative isolation. During seated rest, the SVC-to-IVC venous return ratio is 50/50%. With light/moderate cycling exercise, IVC flow increases by threefold, whereas SVC remains essentially constant.
View details for DOI 10.1152/ajpheart.00022.2004
View details for Web of Science ID 000222848000064
View details for PubMedID 15031121
Regression of severe pulmonary arteriovenous malformations after Fontan revision and "Hepatic factor" rerouting ANNALS OF THORACIC SURGERY 2004; 78 (2): 697-699
Although previously described in patients undergoing staged palliation for univentricular heart disease, the mechanism by which hepatic venous flow prevents development of pulmonary arteriovenous malformations is still not completely understood. We present a case in which successful H-type Fontan revision with rerouting of hepatic venous flow through a hemiazygous vein successfully reversed the progression of severe left pulmonary arteriovenous malformations.
View details for DOI 10.1016/j.athorascur.2004.02.003
View details for Web of Science ID 000222999300055
View details for PubMedID 15276554
Identifying cardiac transplant rejection in children: Diagnostic utility of echocardiography, right heart catheterization and endomyocardial biopsy data JOURNAL OF HEART AND LUNG TRANSPLANTATION 2004; 23 (3): 323-329
There has been a continued search for alternative diagnostic techniques that do not necessitate endomyocardial biopsy for diagnosing rejection in cardiac transplant recipients. The purpose of this study is to evaluate the role of echocardiography and hemodynamic catheterization data compared with endomyocardial biopsy results, in rejection surveillance for the pediatric heart transplant recipient.A prospective, blinded evaluation was performed utilizing echocardiographic and standard right heart catheterization parameters to predict acute rejection episodes.Forty-nine patients underwent 281 biopsies. Two groups were defined: those with Grade <2 rejection and those with grade > or =2 rejection. None of the echocardiographic variables showed significant differences between the study groups and all group data were within normal limits. Mixed venous saturation, mean right atrial pressure, right ventricular end-diastolic pressure and mean pulmonary artery pressure were found to be statistically significant between groups. Receiver-operator characteristic (ROC) curves were constructed to determine the extent to which the various parameters were clinically useful. The ROC found little clinical usefulness for all variables, including those found to be statistically significant.Differences in both echocardiographic and hemodynamic data were not clinically significant between the 2 groups of patients. Although many of the catheterization-derived parameters were statistically significant, they did not permit effective discrimination between groups. This is the only clinically relevant application of such data and may explain the conflicting previous reports. It is only through analyses such as ROC that the clinical application (or lack thereof) can be appreciated in this population.
View details for DOI 10.1016/S1053-2498(03)00209-2
View details for Web of Science ID 000220155700009
View details for PubMedID 15019642
Transcatheter closure of postinfarction ventricular septal defects using the new Amplatzer muscular VSD occluder: Results of a US registry CATHETERIZATION AND CARDIOVASCULAR INTERVENTIONS 2004; 61 (2): 196-201
The objective of this study was to assess the immediate and mid-term results of transcatheter closure of postinfarct muscular ventricular septal defects (VSDs) using the new Amplatzer postinfarct muscular VSD device (PIMVSD). Ventricular septal rupture occurs in 0.2% of myocardial infarcts and remains associated with very high morbidity and mortality. Data were prospectively collected for 18 patients who underwent attempted device closure of postinfarction VSDs between 2000 and 2003. Five patients underwent the closure in the acute phase (within 6 days from the infarct); the remaining patients underwent closure on day 14-95 after the diagnosis of the infarct. Outcome parameters included procedural success, evidence of residual shunts on echocardiography, and occurrence of procedure-related complications. The procedure was successful in deploying a device across the VSD in 16 of 18 patients. The 30-day mortality was 28%. Eleven patients are still alive and have been followed up for a median of 332 days. Two patients required a second procedure to close a residual VSD. At the most recent outpatient follow-up, the VSD was completely closed in two patients, six patients had a trivial or small residual shunt, and two patients had a moderate residual shunt. We conclude that percutaneous device closure of postinfarction VSDs using the Amplatzer PIMVSD occluder appears to be safe and effective. Further trials are required to assess long-term efficacy and compare the results with those of surgical closure.
View details for DOI 10.1002/ccd.10784
View details for Web of Science ID 000188807400008
View details for PubMedID 14755811
Electrical resynchronization - A novel therapy for the failing right ventricle CIRCULATION 2003; 107 (18): 2287-2289
Many patients with congenital heart disease develop right ventricular (RV) failure due to anatomy and prior therapy. RV problems may include right bundle-branch block (RBBB), volume loading, and chamber enlargement. Because the failing RV may have regional dyskinesis, we hypothesized that resynchronization therapy might augment its performance.We studied 7 patients with RV dysfunction and RBBB, using a predefined pacing protocol. QRS duration, cardiac index (CI), and RV dP/dt were measured in 4 different pacing states. Atrioventricular pacing improved CI and RV dP/dtmax and decreased QRS duration as compared with atrial pacing or sinus rhythm.Atrioventricular pacing in patients with RBBB and RV dysfunction augments RV and systemic performance. RV resynchronization is a promising novel therapy for patients with RV failure.
View details for DOI 10.1161/01.CIR.0000070930.33499.9F
View details for Web of Science ID 000182807000014
View details for PubMedID 12732607
Usefulness of epoprostenol therapy in the severely ill adolescent/adult with Eisenmenger physiology AMERICAN JOURNAL OF CARDIOLOGY 2003; 91 (5): 632-635
Temporary IVC filtration before patent foramen ovale closure in a patient with paradoxic embolism JOURNAL OF VASCULAR AND INTERVENTIONAL RADIOLOGY 2002; 13 (12): 1275-1278
Pulmonary embolism (PE) and associated acute peripheral ischemia suggest the diagnosis of paradoxic embolism. The most common intracardiac defect associated with paradoxic emboli is a patent foramen ovale (PFO). Therapeutic options include anticoagulation, thrombolysis, inferior vena cava (IVC) filtration, and closure of the intracardiac defect. The authors discuss the diagnosis and treatment of a young female athlete who presented with massive PE complicated by a paradoxic embolus to the right subclavian artery. Systemic and catheter-directed thrombolysis, IVC filtration, and percutaneous closure of a PFO were performed in an effort to return the patient to the level of competitiveness she desired.
View details for Web of Science ID 000179761700016
View details for PubMedID 12471194
Comparison of contrast echocardiography versus cardiac catheterization for detection of pulmonary arteriovenous malformations AMERICAN JOURNAL OF CARDIOLOGY 2002; 89 (3): 281-285
Because clinical diagnosis of pulmonary arteriovenous malformations (AVMs) is difficult and cardiac catheterization invasive, contrast echo has been used to aid in the diagnosis. Correlation between contrast echo and catheterization data in these patients remains poorly defined. We examined the ability to detect pulmonary AVMs by contrast echocardiography, pulmonary angiography, and pulmonary vein saturations in patients who have undergone cavopulmonary (Glenn) shunts. Pulmonary vein saturations were obtained from catheterization reports. Blinded observers reviewed angiographic and contrast echo data retrospectively in 27 patients who had undergone a Glenn shunt and in 19 controls with biventricular hearts. Contrast echo was positive in 68 of 99 lungs (69%). Angiography showed AVMs in 65 of 98 lungs (66%). Pulmonary vein desaturation was found in 13 of 45 lungs sampled (29%). Only 10 of 38 lungs with positive contrast echo had pulmonary vein desaturation, but only 1 patient had pulmonary vein desaturation without positive contrast echo. The degree of desaturation did not correlate with severity of contrast echo return; 6 of 11 patients with 3+ contrast echo studies had normal pulmonary vein saturations. In a control group of patients with biventricular hearts, only 1 of 19 (5.3%) contrast echos was weakly positive. Contrast echo correlates poorly with angiography and pulmonary vein saturation for evaluation of AVMs. Contrast echo is extremely sensitive and often positive despite normal pulmonary vein saturation. Assessment of pulmonary vein desaturation in 100% oxygen may improve its sensitivity and correlation with contrast echo. Additional studies are needed to follow patients with mildly positive contrast echo studies to enable determination of their clinical relevance.
View details for Web of Science ID 000173624800006
View details for PubMedID 11809429
A technique for maintenance of airway access in infants with a difficult airway following tracheal extubation PAEDIATRIC ANAESTHESIA 2001; 11 (5): 622-625
Tracheal extubation of patients with a difficult airway represents a challenge to anaesthesiologists and intensive care physicians. While a variety of techniques designed to maintain access to the airway in case of the need for tracheal reintubation have been described in adults, no reports have been published in infants and young children. We describe an approach to this issue in a young child with severe micrognathia.
View details for Web of Science ID 000171023200018
View details for PubMedID 11696131
Balloon pulmonary angioplasty for treatment of chronic thromboembolic pulmonary hypertension CIRCULATION 2001; 103 (1): 10-13
Although pulmonary thromboendarterectomy is increasingly successful for the definitive treatment of chronic thromboembolic pulmonary hypertension (CTEPH), not all patients have surgically accessible disease. Others are poor surgical candidates because of comorbid illness. Therefore, for selected patients, we defined and implemented an alternative interventional strategy of balloon pulmonary angioplasty (BPA).Eighteen patients (mean age, 51.8 years; range, 14 to 75 years) with CTEPH underwent BPA; they averaged 2.6 procedures (range, 1 to 5) and 6 dilations (range, 1 to 12). Selection of pulmonary artery segments for dilation required (1) complete occlusion, (2) filling defects, or (3) signs of intravascular webs. After an average of 36 months of follow-up (range, 0.5 to 66 months), the average New York Heart Association class improved from 3.3 to 1.8 (P:<0.001), and 6-minute walking distances increased from 209 to 497 yards (P:<0.0001). Pulmonary artery mean pressures decreased from 43.0+/-12.1 to 33. 7+/-10.2 mm Hg (P:=0.007). Eleven patients developed reperfusion pulmonary edema; 3 required mechanical ventilation.BPA reduces pulmonary artery hypertension in patients with CTEPH and is associated with long-term improvement in New York Heart Association class and 6-minute walking distances. BPA is a promising interventional technique that warrants randomized comparison with medical therapy in CTEPH patients who are not surgical candidates.
View details for Web of Science ID 000166287300006
View details for PubMedID 11136677
Preoperative management of pulmonary venous hypertension in hypoplastic left heart syndrome with restrictive atrial septal defect AMERICAN JOURNAL OF CARDIOLOGY 1999; 83 (8): 1224-1228
A severely restrictive atrial septal defect (ASD) in neonates with hypoplastic left heart syndrome (HLHS) results in pulmonary venous hypertension, pulmonary edema, and intractable hypoxia. Between January 1983 and June 1998, 21 of 355 neonates presenting with HLHS (5.9%) underwent cardiac catheterization at median age 1 day (range 0 to 25), for creation or enlargement of a restrictive or absent interatrial communication. One patient died during preliminary angiography. Three underwent blade septostomy with 2 procedure-related deaths, and 1 had balloon atrial septostomy (BAS); all 4 died before surgical intervention. Fifteen underwent Brockenbrough atrial septoplasty with transatrial needle puncture and serial balloon dilations of the new ASD, 5 after unsuccessful BAS. The most recent patient had a stent placed across the atrial septum after transatrial needle puncture. In the 16 patients treated with septoplasty or stent, oxygen saturation increased from 50 +/- 4% to 83 +/- 2% (p <0.0001) and transatrial pressure gradient decreased from 16 +/- 1 to 6 +/- 1 mm Hg (p <0.0001). One patient died awaiting transplantation, supportive care only was requested in 1, and 14 underwent stage 1 palliation. Eight of 14 (57%) survived to hospital discharge. Six of 7 (86%) survived bidirectional Glenn and the 3 who have undergone fenestrated Fontan are alive. In neonates with HLHS, a restrictive ASD resulting in profound cyanosis demands urgent intervention. BAS is frequently unsuccessful and blade septostomy has high mortality. Pulmonary venous hypertension can be adequately relieved by Brockenbrough atrial septoplasty or stenting, allowing stabilization before reconstructive surgery or while awaiting transplant.
View details for Web of Science ID 000079659100016
View details for PubMedID 10215289
Using cardiac phase to order reconstruction [CAPTOR]: A method to improve diastolic images JMRI-JOURNAL OF MAGNETIC RESONANCE IMAGING 1997; 7 (5): 794-798
A method is proposed to reconstruct multiphase images that accurately depicts the entire cardiac cycle. A segmented, gradient-recalled-echo sequence (FASTCARD) was modified to acquire data continuously. Images were reconstructed retrospectively by selecting views from each heartbeat based on cardiac phase rather than the time elapsed from the QRS complex. Cardiac phase was calculated using a model that compensates for beat-to-beat heart rate changes. Images collected using cardiac phase to order reconstruction (CAPTOR) depict the entire cardiac cycle and lack the temporal gap that is characteristic of prospectively reconstructed sequences. Time-volume curves of the left ventricle capture the contribution of atrial contraction to end-diastolic volume (EDV). Transmitral phase-contrast flow measurements show a second peak inflow (alpha wave) that is absent in the standard sequence. Because atrial contraction contributes to ventricular EDV, images using CAPTOR potentially may provide a more reliable measure of EDV, stroke volume, and ejection fraction than standard techniques.
View details for Web of Science ID A1997XW88300004
View details for PubMedID 9307903