Partial heart transplantation for pediatric heart valve dysfunction: A clinical trial protocol.

Congenital heart defects are the most common type of birth defects in humans and frequently involve heart valve dysfunction. The current treatment for unrepairable heart valves involves valve replacement with an implant, Ross pulmonary autotransplantation, or conventional orthotopic heart transplantation. Although these treatments are appropriate for older children and adults, they do not result in the same efficacy and durability in infants and young children for several reasons. Heart valve implants do not grow with the. Ross pulmonary autotransplants have a high mortality rate in neonates and are not feasible if the pulmonary valve is dysfunctional or absent. Furthermore, orthotopic heart transplants invariably fail from ventricular dysfunction over time. Therefore, the treatment of irreparable heart valves in infants and young children remains an unsolved problem. The objective of this single-arm, prospective study is to offer an alternative solution based on a new type of transplant, which we call "partial heart transplantation." Partial heart transplantation differs from conventional orthotopic heart transplantation because only the part of the heart containing the heart valve is transplanted. Similar to Ross pulmonary autotransplants and conventional orthotopic heart transplants, partial heart transplants contain live cells that should allow it to grow with the recipient child. Therefore, partial heart transplants will require immunosuppression. The risks from immunosuppression can be managed, as seen in conventional orthotopic heart transplant recipients. Stopping immunosuppression will simply turn the growing partial heart transplant into a non-growing homovital homograft. Once this homograft deteriorates, it can be replaced with a durable adult-sized mechanical implant. The protocol for our single-arm trial is described. The ClinicalTrials.gov trial registration number is NCT05372757.

Clinical approach to vasoplegia in the transplant patient from the Pediatric Heart Transplant Society.

This manuscript outlines a clinical approach to vasoplegia incorporating the current state of knowledge regarding vasoplegia in pediatric patients immediately post-transplant and to identify modifiable factors both pre- and post-transplant that may reduce post-operative morbidity, end-organ dysfunction, and mortality. Centers participating in the Pediatric Heart Transplant Society (PHTS) were asked to provide their internal protocols and rationale for vasoplegia management, and applicable adult and pediatric data were reviewed. The authors synthesized the above protocols and literature into the following description of clinical approaches to vasoplegia highlighting areas of both broad consensus and of significant practice variation.

Circumstances surrounding end-of-life in pediatric patients pre- and post-heart transplant: a report from the Pediatric Heart Transplant Society.

BACKGROUND: Although mortality has decreased considerably in pediatric heart transplantation, waitlist and post-transplant death rates remain notable. End-of-life focused research in this population, however, is very limited. This Pediatric Heart Transplant Society study aimed to describe the circumstances surrounding death of pediatric heart transplant patients. METHODS: A retrospective analysis of the multi-institutional, international, Pediatric Heart Transplant Society registry was conducted. Descriptive statistics and univariate analyses were performed to 1) describe end-of-life in pediatric pre- and post-heart transplant patients and 2) examine associations between location of death and technological interventions at end-of-life with demographic and disease factors. RESULTS: Of 9217 patients (0-18 years) enrolled in the registry between 1993 and 2018, 2804 (30%) deaths occurred; 1310 while awaiting heart transplant and 1494 post-heart transplant. The majority of waitlist deaths (89%) occurred in the hospital, primarily in ICU (74%) with most receiving mechanical ventilation (77%). Fewer post-transplant deaths occurred in the hospital (22%). Out-of-hospital death was associated with older patient age (p < .01). CONCLUSIONS: ICU deaths with high use of technological interventions at end-of-life were common, particularly in patients awaiting heart transplant. In this high mortality population, findings raise challenging considerations for clinicians, families, and policy makers on how to balance quality of life amidst high risk for hospital-based death.

A Validated Model for Sudden Cardiac Death Risk Prediction in Pediatric Hypertrophic Cardiomyopathy.

BACKGROUND: Hypertrophic cardiomyopathy is the leading cause of sudden cardiac death (SCD) in children and young adults. Our objective was to develop and validate a SCD risk prediction model in pediatric hypertrophic cardiomyopathy to guide SCD prevention strategies. METHODS: In an international multicenter observational cohort study, phenotype-positive patients with isolated hypertrophic cardiomyopathy <18 years of age at diagnosis were eligible. The primary outcome variable was the time from diagnosis to a composite of SCD events at 5-year follow-up: SCD, resuscitated sudden cardiac arrest, and aborted SCD, that is, appropriate shock following primary prevention implantable cardioverter defibrillators. Competing risk models with cause-specific hazard regression were used to identify and quantify clinical and genetic factors associated with SCD. The cause-specific regression model was implemented using boosting, and tuned with 10 repeated 4-fold cross-validations. The final model was fitted using all data with the tuned hyperparameter value that maximizes the c-statistic, and its performance was characterized by using the c-statistic for competing risk models. The final model was validated in an independent external cohort (SHaRe [Sarcomeric Human Cardiomyopathy Registry], n=285). RESULTS: Overall, 572 patients met eligibility criteria with 2855 patient-years of follow-up. The 5-year cumulative proportion of SCD events was 9.1% (14 SCD, 25 resuscitated sudden cardiac arrests, and 14 aborted SCD). Risk predictors included age at diagnosis, documented nonsustained ventricular tachycardia, unexplained syncope, septal diameter z-score, left ventricular posterior wall diameter z score, left atrial diameter z score, peak left ventricular outflow tract gradient, and presence of a pathogenic variant. Unlike in adults, left ventricular outflow tract gradient had an inverse association, and family history of SCD had no association with SCD. Clinical and clinical/genetic models were developed to predict 5-year freedom from SCD. Both models adequately discriminated between patients with and without SCD events with a c-statistic of 0.75 and 0.76, respectively, and demonstrated good agreement between predicted and observed events in the primary and validation cohorts (validation c-statistic 0.71 and 0.72, respectively). CONCLUSION: Our study provides a validated SCD risk prediction model with >70% prediction accuracy and incorporates risk factors that are unique to pediatric hypertrophic cardiomyopathy. An individualized risk prediction model has the potential to improve the application of clinical practice guidelines and shared decision making for implantable cardioverter defibrillator insertion. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT0403679.

Cardiac allograft vasculopathy and graft failure in pediatric heart transplant recipients after rejection with severe hemodynamic compromise.

BACKGROUND: Rejection with severe hemodynamic compromise (RSHC) carries a mortality risk approaching 50%. We aimed to identify current risk factors for RSHC and predictors of graft failure after RSHC. METHODS: Data from 3,259 heart transplant (HT) recipients between January 2005 and December 2015 in the Pediatric Heart Transplant Study (PHTS) were analyzed. Predictors for RSHC and outcome after RSHC were sought. Time to RSHC was analyzed using the Cox proportional hazards regression model. Cardiac allograft vasculopathy (CAV) after HT and CAV after RSHC were analyzed as time-dependent covariates. Timing of RSHC was analyzed as occurring before and after 4 years after RSHC. RESULTS: There were 309 patients (9.5%) with ≥ 1 RSHC episodes. In 143 patients with RSHC, the first episode was within 1 year after HT. Independent risk factors for RSHC were age 1 to 5 years at HT (hazard ratio [HR], 1.51; 95% confidence interval [CI], 1.04-2.18), age > 10 years at HT (HR, 1.83; 95% CI, 1.29-2.60), black race (HR, 1.64; 95% CI, 1.25-2.15), prior cardiac surgery (HR, 1.55; 95% CI, 1.03-2.31), ventricular assist device support at HT (HR, 1.65; 95% CI, 1.18-2.29), maintenance steroids (HR, 1.39; 95% CI, 1.06-1.82), and recipient on inotropes, pressors, or thyroid hormones (HR, 1.45; 95% CI, 1.09-1.94). Graft survival at 5 years after RSHC was 45.7%. RSHC was a greater risk factor for earlier CAV (HR, 7.78; 95% CI, 5.82-10.40) than other rejection types (HR, 2.31; 95% CI, 1.79-3.00). Patients with late RSHC, after 1 year after RSHC had increased risk of graft loss 4 years after RSHC (HR, 7.12; 95% CI, 2.18-23.22). The 5-year graft survival after RSHC was 50.5% for early RSHC and 39.0% for late RSHC. CONCLUSIONS: Mortality after RSHC is high in the current treatment era. Many patient risk factors for RSHC cannot be modified, including age, race, prior cardiac surgery, and ventricular assist device support. After RSHC, CAV is the only predictor of graft failure. Patients who have late RSHC fare worse than those who have RSHC within the first year after HT.

Worldwide Experience of a Durable Centrifugal Flow Pump in Pediatric Patients.

The primary objectives of this study were to describe the characteristics and survival outcomes for children supported with the HeartWare HVAD® system from the global community. This was a retrospective survey of patients <18 years of age with an HVAD® system. Questionnaires were sent to sites worldwide in April 2015 and collected between May 2015 and 2016. Information on 205 patients was collected. The median age at implantation was 13.1 years (interquartile range [IQR] 9.8-15.8 years) and the weight was 42 kg (IQR 28-60 kg). Over half of the implants occurred in males (61%), with the most common diagnosis being cardiomyopathy (n = 168, 82%). The majority of HVAD® systems implanted were left ventricular assist device (n = 189, 92.2%). Temporary right ventricular support was utilized in 24 patients (12%) with a median duration of 12 days (6-32 days). Fifty-five percent (n = 111) of the patients were discharged home after implantation after a median (IQR) duration of hospital stay of 40 days (28-71 days). By 12 months, the proportion of patients who underwent heart transplant was 65.4%, 10.7% had died, 3.2% were explanted for recovery, and 20.8% remained on the device. Death on the device on multivariable analysis was associated with the need for temporary RV support (hazard ratio [HR] 10.65 (95% CI 12.53-44.81), P = 0.001) and pump exchange (HR 7.9 (95% CI 1.8-34.2], P = 0.006). The use of the HeartWare HVAD system in the pediatric population is associated with mortality with the majority of patients supported to heart transplant by 1 year post implant. These positive results are independent of geographic location. The need for a temporary right heart support and pump exchange is associated with a higher risk of poor outcomes, and further work is required to predict these patients to allow for optimization. Although survival results are promising, further studies are needed to delineate the associated morbidities with this technology in the pediatric population.

Heart failure after the Norwood procedure: An analysis of the Single Ventricle Reconstruction Trial.

BACKGROUND: Heart failure results in significant morbidity and mortality in young children with hypoplastic left heart syndrome (HLHS) after the Norwood procedure. METHODS: We studied subjects enrolled in the prospective Single Ventricle Reconstruction (SVR) Trial who survived to hospital discharge after a Norwood operation and were followed up to age 6 years. The primary outcome was heart failure, defined as heart transplant listing after Norwood hospitalization, death attributable to heart failure, or symptomatic heart failure (New York Heart Association [NYHA] Class IV). Multivariate modeling was undertaken using Cox regression methodology to determine variables associated with heart failure. RESULTS: Of the 461 subjects discharged home following a Norwood procedure, 66 (14.3%) met the criteria for heart failure. Among these, 15 died from heart failure, 39 were listed for transplant (22 had a transplant, 12 died after listing, and 5 were alive and not yet transplanted), and 12 had NYHA Class IV heart failure but were never listed. The median age at heart failure identification was 1.28 (interquartile range 0.30 to 4.69) years. Factors associated with early heart failure included post-Norwood lower fractional area change, need for extracorporeal membrane oxygenation, non-Hispanic ethnicity, Norwood perfusion type, and total support time (p < 0.05). CONCLUSIONS: By 6 years of age, heart failure developed in nearly 15% of children after the Norwood procedure. Although transplant listing was common, many patients died from heart failure before receiving a transplant or without being listed. Shunt type did not impact the risk of developing heart failure.

Longitudinal Outcomes of Patients With Single Ventricle After the Fontan Procedure.

BACKGROUND: Multicenter longitudinal objective data for survival into adulthood of patients who have undergone Fontan procedures are lacking. OBJECTIVES: This study sought to describe transplant-free survival and explore relationships between laboratory measures of ventricular performance and functional status over time. METHODS: Exercise testing, echocardiography, B-type natriuretic peptide, functional health assessment, and medical history abstraction were repeated 9.4 ± 0.4 years after the Fontan Cross-Sectional Study (Fontan 1) and compared with previous values. Cox regression analysis explored risk factors for interim death or cardiac transplantation. RESULTS: From the original cohort of 546 subjects, 466 were contacted again, and 373 (80%) were enrolled at 21.2 ± 3.5 years of age. Among subjects with paired testing, the percent predicted maximum oxygen uptake decreased (69 ± 14% vs. 61 ± 16%; p < 0.001; n = 95), ejection fraction decreased (58 ± 11% vs. 55 ± 10%; p < 0.001; n = 259), and B-type natriuretic peptide increased (median [interquartile range] 13 [7 to 25] pg/mol vs. 18 [9 to 36] pg/mol; p < 0.001; n = 340). At latest follow-up, a lower Pediatric Quality of Life Inventory physical summary score was associated with poorer exercise performance (R2 adjusted = 0.20; p < 0.001; n = 274). Cumulative complications since the Fontan procedure included additional cardiac surgery (32%), catheter intervention (62%), arrhythmia treatment (32%), thrombosis (12%), and protein-losing enteropathy (8%). Since Fontan 1, 54 subjects (10%) have received a heart transplant (n = 23) or died without transplantation (n = 31). The interval risk of death or/cardiac transplantation was associated with poorer ventricular performance and functional health status assessed at Fontan 1, but it was not associated with ventricular morphology, the subject's age, or the type of Fontan connection. CONCLUSIONS: Interim transplant-free survival over 12 years in this Fontan cohort was 90% and was independent of ventricular morphology. Exercise performance decreased and was associated with worse functional health status. Future interventions might focus on preserving exercise capacity. (Relationship Between Functional Health Status and Ventricular Performance After Fontan-Pediatric Heart Network; NCT00132782).

Systolic-diastolic functional coupling in healthy children and in those with dilated cardiomyopathy.

Systolic and diastolic function affect dilated cardiomyopathy (DCM) outcomes. However, systolic-diastolic coupling, as a distinct characteristic, may itself affect function but is poorly characterized. We hypothesized that echocardiographic left ventricular (LV) longitudinal systolic tissue velocities (S') correlate with diastolic longitudinal velocities (E') and that their relationship is associated with ventricular function and that this relationship is impaired in pediatric DCM. We analyzed data from the Pediatric Heart Network Ventricular Volume Variability study, using linear regression and generalized additive modeling to assess relationships between S' and E' at the lateral and septal mitral annulus. We explored relationships between the systolic:diastolic (S:D) coupling ratio (S':E' relative to age) and ventricular function. Up to 4 echocardiograms from 130 DCM patients (mean age: 9.3 ± 6.1 yr) and 1 echocardiogram from each of 591 healthy controls were analyzed. S' and E' were linearly related in controls (r = 0.64, P < 0.001) and DCM (r = 0.83, P < 0.001). In DCM, the magnitude of association between S' and E' was reduced with progressive ventricular remodeling. The S:D ratio was more strongly associated with LV function in controls vs. DCM. The septal S:D ratio was higher (presumed worse) in DCM vs. controls (0.69 ± 0.13 vs. 0.62 ± 0.12, P = 0.001). A higher septal S:D ratio was associated with worse LV dimensions (parameter estimate: 0.0061, P = 0.004), mass (parameter estimate: 0.0074, P = 0.002), ejection fraction (parameter estimate: -0.0303, P = 0.024), and inflow propagation (parameter estimate: -0.3538, P < .001). S:D coupling becomes weaker in DCM with LV remodeling and dysfunction. The S:D coupling ratio may be useful to assess coupling, warranting study in relation to patient outcomes.

Factors affecting Fontan length of stay: Results from the Single Ventricle Reconstruction trial.

BACKGROUND: In the Single Ventricle Reconstruction trial, infants with hypoplastic left heart syndrome (HLHS) who received a right-ventricle-to-pulmonary-artery shunt (RVPAS) versus a modified Blalock-Taussig shunt (MBTS) had lower early postoperative mortality, but more complications at 14 months. We explored the effect of shunt type and other patient, medical, and surgical factors on postoperative length of stay (LOS) after the Fontan operation. METHODS: Fontan postoperative course was ascertained from medical record review. Cox proportional hazards modeling was used to identify factors associated with LOS. RESULTS: Of 327 subjects who underwent Fontan, 323 were analyzed (1 death, 1 biventricular repair, 2 with missing data). Median age and weight at Fontan were 2.8 years (interquartile range [IQR]: 2.3, 3.4) and 12.7 kg (IQR: 11.4, 14.1), respectively. Fontan type was extracardiac in 55% and lateral tunnel in 45%; 87% were fenestrated. The RVPAS and MBTS subjects had similar LOS (median 11 days [IQR: 9, 18] vs 10 days [IQR: 9, 13]; P = .23). Independent risk factors for longer LOS were treatment center (P < .01), LOS at stage II (hazard ratio [HR] 1.02 for each additional day; P < .01), and pre-Fontan complications (HR 1.03 for each additional complication; P = .04). Use of deep hypothermic circulatory arrest at Fontan (HR 0.64; P = .02) was independently associated with shorter LOS. When center was excluded from the model, pre-Fontan complications and use of circulatory arrest were no longer significant; instead, older age at stage II (HR 1.08 for each additional month; P = .01) predicted longer LOS. In 254 subjects who had a pre-Fontan echocardiogram, at least moderate tricuspid regurgitation was independently associated with longer LOS, both with center (HR 1.72; P < .01) and without center in the model (HR 1.49; P = .02). CONCLUSIONS: In this multicenter prospective cohort of subjects with HLHS, Norwood shunt type was not associated with Fontan LOS. Rather, global measures of earlier medical complexity indicate greater likelihood of longer LOS after the Fontan operation.

Paediatric cardiovascular clinical trials: an analysis of ClinicalTrials.gov and the Food and Drug Administration Pediatric Drug Labeling Database.

Recent regulatory initiatives in the United States of America and Europe have transformed the paediatric clinical trials landscape by significantly increasing capital investment and paediatric trial volume. The purpose of this manuscript was to review the impact of these initiatives on the paediatric cardiovascular trials landscape when compared with other paediatric sub-specialties. We also evaluate factors that may have contributed to the success or failure of recent major paediatric cardiovascular trials so as to inform the optimal design and conduct of future trials in the field.

Elevated pre-transplant pulmonary vascular resistance is not associated with mortality in children without congenital heart disease: a multicenter study.

BACKGROUND: Traditionally, an elevated pulmonary vascular resistance index (PVRI) has been a relative contraindication to pediatric orthotopic heart transplantation. This study examined the risk of elevated pre-transplant PVRI on early (30-day) and intermediate-term mortality in pediatric heart transplant recipients without congenital heart disease (CHD). METHODS: A review of the prospective multicenter Pediatric Heart Transplant Study registry identified all patients without CHD in whom a pre-transplant PVRI was recorded. Of 35 participating centers, 29 reported heart transplants in children with a markedly elevated PVRI (> 5 WU × m(2), corresponding to the highest quartile). Multiphase parametric analysis was performed, adjusting for potential risk factors to assess the association of PVRI with early and intermediate-term mortality. RESULTS: Between 1993 and 2011, 1,909 children without CHD underwent heart transplantation at a median age of 9.7 years (range, 1.6 months-18 years). Of those, 795 (42%) had a recorded or calculable pre-transplant PVRI, and PVRI > 5 WU × m(2) was present in 193 patients (24%). For all recipients, median pre-transplant PVRI was 3.15 WU × m(2) (range, 0.4-23 WU × m(2)); 2.8 WU × m(2) in infants < 1 year, 3.5 WU × m(2) in patients aged 1 to 10 years, and 3.0 WU × m(2) in patients aged > 10 years (p = 0.03). Multivariable hazard analysis controlling for graft ischemic time and pre-transplant ventilation showed no association of elevated PVRI with early mortality (relative risk, 1.2; p = 0.66), nor with intermediate mortality when controlled for year of transplant, age, race, and pre-sensitization (relative risk, 0.7; p = 0.27). CONCLUSIONS: Elevation of PVRI did not affect post-transplant survival in this large, multicenter cohort of pediatric heart transplant recipients without CHD, suggesting that the barrier of elevated PVRI can be successfully overcome in this population.

ABO-incompatible heart transplantation: analysis of the Pediatric Heart Transplant Study (PHTS) database.

BACKGROUND: ABO incompatible (ABOi) heart transplantation is an accepted approach to increasing organ availability for young patients. Previous studies have suggested that early survival for ABOi transplants is similar to ABO compatible (ABOc) transplants. We analyzed the Pediatric Heart Transplant Study (PHTS) database from 1/96 to 12/08 to further assess this strategy. METHODS: We analyzed the numbers of ABOi and ABOc done at the PHTS centers. We then compared the clinical characteristics, and short-term freedom from death, rejection and infection in the ABOi patients with the patients that had an ABOc heart transplant during the same period. All patients were less than or equal to 15 months of age at listing (the age of the oldest ABOi patient). We adjusted for co-variates shown to increase risk for mortality (age less than 1 month, extracorporeal membrane oxygenation (ECMO), ventilator, previous sternotomy, and congenital heart disease). RESULTS: There were 931 total transplants done at 34 PHTS centers during the 12 year time period in patients ≤15 months of age. Of these, 502 transplants were performed at 20 PHTS centers that did at least one ABOi heart transplant. Eighty-five of the 502 (17%) were ABOi. At time of transplant, ABOi recipients compared with ABOc were more likely to be on a ventilator (49.4% vs 36.5%, p=0.025), and more often supported with ECMO (23.5% vs 13.4%, p=0.018). There was similar survival at 12 months (82% vs 84%, p=0.7). In risk adjusted analysis ABOi status was not associated with 1 year mortality (HR 0.85, 95% CI 0.45-1.6, p=0.61). The ABOi patients had greater freedom from rejection when compared with ABOc patients for all 34 centers (75% vs 62%, p=0.016), but the difference was not significant when limited only to the 20 centers doing ABOi transplants (75% vs 69%, p=0.4). The ABOi cohort had lower infection rates (23.5% vs 37.9%, p = 0.013). This difference remained after adjusting for center and other covariates. CONCLUSIONS: In center and risk adjusted analysis, young children who received an ABOi transplant had equivalent one-year survival and freedom from rejection compared with those who received an ABOc transplant. In spite of the favorable outcome for ABOi recipients, many centers appear to reserve ABOi transplantation for sicker patients. These data mandate reexamination of the current United Network for Organ Sharing (UNOS) policy that gives priority to ABOc over ABOi transplantation in the United States.