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Background: Studies have shown that the optimal ischemia time (IT) threshold in pediatric heart transplantation (PHT) is up to 4 h, independent of other donor organ factors. The purpose of this study was to examine the relationship between IT and donor left ventricular ejection fraction (LVEF) and study their impact on PHT outcomes., Methods: This is a retrospective cohort study of PHT (<18 years) identified in UNOS between January 2000 and March 2020. Post-transplantation survival analysis of patients receiving donor hearts with IT<4, 4-6, and >6 h was performed using Kaplan-Meier curves. Cohort was divided according to donor LVEF median value, and survival was analyzed. Cox regression was performed., Results: Median LVEF was 65% in the study cohort (6669 PHT). Overall, IT>6 h was associated with worse survival compared to <4 h regardless of donor LVEF. For allografts with LVEF < 65%, IT = 4-6 h was associated with worse survival compared with IT < 4 h (p = .006) but had similar survival compared with IT > 6 h (p = .315). For allografts with LVEF ≥ 65%, IT = 4-6 h had similar survival compared with <4 h (p = .175) but improved survival compared with >6 h (p = .003). After adjusting for donor and recipient variables, Cox regression showed that IT = 4-6 h was not associated with increased mortality for LVEF ≥ 65%., Conclusions: The IT threshold of 4 h does not apply to all allografts. Recipients of hearts with LVEF≥65% can tolerate an IT up to 6 h without any detriment to survival. Routine acceptance of these donor hearts could mitigate longer waiting times and poor donor availability for many candidates., (© 2022 Wiley Periodicals LLC.)

Despite increasing utilization of continuous-flow pediatric ventricular assist devices (VAD) in children, data on exercise testing and cardiac rehabilitation (CR) are unknown. We described variation in CR practices and identified barriers to exercise testing and CR. A survey was performed through the Advanced Cardiac Therapies Improving Outcomes Network (ACTION) representing pediatric VAD centers across North America. Descriptive statistics were performed. A multidisciplinary cohort of 52 respondents from 28 pediatric VAD centers responded. Although 38% reported performing exercise testing, most (65%) used 6 minute walk tests rather than formal cycle or treadmill exercise testing. While all respondents refer to physical therapy during the initial inpatient stay for VAD placement, only 52% refer to a CR program. When performed, CR was performed at an ACTION center (84%), a local specialized center (21%), or a home-based CR program (26%). Commonly cited barriers to either CR or exercise testing were inadequate resources, inadequate implementation logistics knowledge, concerns about safety, inability of patients to travel to a CR facility, and concern about utility of exercise testing or CR. Over 90% of centers were interested in implementing a standardized pediatric VAD CR program. Utilization of exercise testing and CR after VAD placement is variable. Despite perceived barriers, most pediatric VAD centers are interested in implementing a standardized CR program for recipients. In response to this interest, we plan to implement a standardized CR protocol to all ACTION pediatric VAD centers in an effort to improve pretransplant waitlist rehabilitation and post-transplant outcomes., Competing Interests: Disclosure: The authors have no conflicts of interest to report., (Copyright © ASAIO 2021.)

Background: The impact of sex on phenotypic expression in hypertrophic cardiomyopathy (HCM) has not been well characterized in genotyped cohorts., Methods: Retrospective cohort study from an international registry of patients receiving care at experienced HCM centers. Sex-based differences in baseline characteristics and clinical outcomes were assessed., Results: Of 5873 patients (3788 genotyped), 2226 (37.9%) were women. At baseline, women were older (49.0±19.9 versus 42.9±18.4 years, P <0.001) and more likely to have pathogenic/likely pathogenic sarcomeric variants (HCM patients with a sarcomere mutation; 51% versus 43%, P <0.001) despite equivalent utilization of genetic testing. Age at diagnosis varied by sex and genotype despite similar distribution of causal genes. Women were 3.6 to 7.1 years older at diagnosis ( P <0.02) except for patients with MYH7 variants where age at diagnosis was comparable for women and men (n=492; 34.8±19.2 versus 33.3±16.8 years, P =0.39). Over 7.7 median years of follow-up, New York Heart Association III-IV heart failure was more common in women (hazard ratio, 1.87 [CI, 1.48-2.36], P <0.001), after controlling for their higher burden of symptoms and outflow tract obstruction at baseline, reduced ejection fraction, HCM patients with a sarcomere mutation, age, and hypertension. All-cause mortality was increased in women (hazard ratio, 1.50 [CI, 1.13-1.99], P <0.01) but neither implantable cardioverter-defibrillator utilization nor ventricular arrhythmia varied by sex., Conclusions: In HCM, women are older at diagnosis, partly modified by genetic substrate. Regardless of genotype, women were at higher risk of mortality and developing severe heart failure symptoms. This points to a sex-effect on long-term myocardial performance in HCM, which should be investigated further.

With the new era of increasing use of mechanical circulatory support (MCS) in children, seemingly more patients with elevated pulmonary vascular resistance (PVR) are having positive outcomes. The purpose of this study was to define the effect of MCS on pediatric patients listed for heart transplant with an elevated PVR. The United Network for Organ Sharing (UNOS) database was used to identify patients aged 0-18 at the time of listing for heart transplant between 2010 and 2019 who had PVR documented (n = 2081). Patients were divided into MCS (LVAD, RVAD, BiVAD, and TAH) and No MCS groups, then divided by PVR (PVR) at the time of listing: <3, 3-6, and >6 Wood units (WU). MCS was used in 20% overall (n = 426); 57% of those with PVR <3, 27% with PVR 3-6, and 16% with PVR >6. MCS, PVR <3 patients had a higher chance of positive waitlist outcome than all No MCS groups (vs. PVR <3, P = .049; vs. PVR 3-6, P = .004; vs. PVR >6, P < .001). MCS, PVR 3-6 patients had a higher chance of positive waitlist outcome than all No MCS groups (vs. PVR <3, P = .048; vs. PVR 3-6, P = .009; vs. PVR >6, P < .001). MCS, PVR >6 patients had a higher chance of positive waitlist outcome than No MCS, PVR >6 patients (P = .012). Within the No MCS group, patients with a PVR >6 had a higher incidence of negative waitlist outcome compared to PVR <3 (17% vs. 10%, P = .002); this was not the case in the MCS group (5% vs. 6%, P = .693). More patients in the MCS group were ventilator dependent (15% vs. 9%, P < .001) at the time of listing and less likely to have a functional status >50% (43% vs. 73%, P < .001). No significant differences in post-transplant survival were found in pairwise comparisons of MCS and No MCS PVR subgroups. Patients supported with MCS had a significantly higher chance of a positive waitlist outcome than those without such support regardless of PVR status. This was most pronounced with a PVR greater than 6 WU. MCS compared to No MCS patients had better waitlist survival and equivalent post-transplant survival. MCS patients, despite being more ill, had better overall survival regardless of PVR., (© 2020 International Center for Artificial Organs and Transplantation and Wiley Periodicals LLC.)

Background: Exercise limitation is almost universal among Fontan patients. Identifying unique clinical features in the small fraction of Fontan patients with normal exercise capacity (high-capacity Fontan [HCF]) provides potential to inform clinical strategies for those with low exercise capacity (usual Fontan)., Methods: We performed a retrospective chart review of all patients with single-ventricle physiology palliated with a Fontan operation who underwent incremental cardiopulmonary exercise testing at Cincinnati Children's Hospital Medical Center from 2013 to 2018. Comparison was between patients with peak oxygen uptake < vs ≥ 80% predicted., Results: A total of 22 of 112 patients were classified as HCF (68% were female; aged 18 ± 7 years). During incremental exercise, peak oxygen uptake (86.1% ± 6.1% vs 62% ± 12.2% predicted; P < 0.001) was greater in HCF vs usual Fontan despite similar chronotropic impairment, resulting in a greater oxygen pulse in HCF. Pulmonary function, breathing reserve, and ventilatory equivalent for CO 2 output slope were not different between groups. Those in the HCF group were more likely to self-report exercise ≥ 4 days/week for at least 30 minutes (77% vs 10%, P < 0.001), have normal systolic function (95% vs 74%, P = 0.003), have fewer postoperative complications (8% vs 36%, P = 0.04), and have shorter post-Fontan length of stay (8 ± 2.8 vs 12.4 ± 0.9 days, P = 0.04)., Conclusions: Approximately 1 in 5 Fontan patients who undergo cardiopulmonary exercise testing have normal exercise capacity despite chronotropic impairment. This implies a better preserved stroke volume, perhaps due to greater muscle pump-mediated preload. Additionally, a complicated perioperative Fontan course is associated with eventual impaired functional capacity., (Copyright © 2019 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.)

Patients with a Fontan circulation have impaired exercise capacity. Cardiac rehabilitation (CR) has shown promise in enhancing peak exercise parameters in this population, but an improvement in submaximal exercise has not been consistently demonstrated. We assessed the hypothesis that participation in CR will be associated with more efficient oxygen extraction and ventilation during submaximal exercise. In this prospective study, pediatric Fontans completed two 60 min CR sessions per week for 12 weeks. Cardiopulmonary exercise testing and stress echocardiography were performed at baseline and last CR session, and then compared with a paired sample t test. Ten pediatric Fontans completed the study. Five had tricuspid atresia and five had hypoplastic left heart syndrome. No serious adverse events occurred during CR sessions. Peak indexed oxygen consumption increased by a mean of 3.7 mL/kg/min (95% CI 1.5-5.9; p = 0.004), and peak oxygen pulse increased by a mean of 0.9 mL/beat (95% CI 0.4-1.4; p = 0.004). The peak respiratory exchange ratio did not change significantly. The significant difference in oxygen pulse became evident during submaximal exercise without a corresponding difference in echocardiographic stroke volume. Indexed oxygen consumption at ventilatory anaerobic threshold increased by a mean of 3.0 mL/kg/min (95% CI - 0.07 to 6.0; p = 0.055). The slope for the volume of expired ventilation to volume of carbon dioxide production improved by a mean of 4.5 (95% CI - 8.4 to - 0.6; p = 0.03). We observed significant improvements in both submaximal and peak exercise performance in pediatric Fontans undergoing CR with no serious adverse events. These changes appeared to be mediated, at least in part, by more efficient oxygen extraction and ventilation.

The objective of this study is to describe identifiable risk factors, complications, and pitfalls while listing pediatric patients for heart transplantation, which is the standard of care for end-stage heart disease in children. Since the introduction of cyclosporine in the 1980s, the management in pediatric heart transplantation has shown consistent improvement, mainly because of technological advances and the integration of multidisciplinary teams in the field. However, the complexity of this patient population makes medical providers vulnerable to complications as a result of undesirable mistakes. Transplant survival is impacted negatively when mistakes from health-care providers compound the high-risk status of the patient. The identification of multiple risk factors and undesirable miscalculations may help transplant teams make decisions before allocating organs, intervene or minimize morbidity, and provide the best quality of life to recipients., (Copyright © 2017 Elsevier Inc. All rights reserved.)