Background: Waitlist mortality (WM) remains elevated in pediatric heart transplantation. Allocation policy is a potential tool to help improve WM. This study aims to identify patients at highest risk for WM to potentially inform future allocation policy changes.
Methods: The Pediatric Heart Transplant Society database was queried for patients <18 years of age indicated for heart transplantation between January 1, 2010 to December 31, 2021. Waitlist mortality was defined as death while awaiting transplant or removal from the waitlist due to clinical deterioration. Because WM is low after the first year, analysis was limited to the first 12 months on the heart transplant list. Kaplan-Meier analysis and log-rank testing was conducted to compare unadjusted survival between groups. Cox proportional hazard models were created to determine risk factors for WM. Subgroup analysis was performed for status 1A patients based on body surface area (BSA) at time of listing, cardiac diagnosis, and presence of mechanical circulatory support.
Results: In total 5974 children met study criteria of which 3928 were status 1A, 1012 were status 1B, 963 were listed status 2, and 65 were listed status 7. Because of the significant burden of WM experienced by 1A patients, further analysis was performed in only patients indicated as 1A. Within that group of patients, those with smaller size and lower eGFR had higher WM, whereas those patients without congenital heart disease or support from a ventricular assist device (VAD) at time of listing had decreased WM. In the smallest size cohort, cardiac diagnoses other than dilated cardiomyopathy were risk factors for WM. Previous cardiac surgery was a risk factor in the 0.3 to 0.7 m2 and >0.7 m2 BSA groups. VAD support was associated with lower WM other than in the single ventricle cohort, where VAD was associated with higher WM. Extracorporeal membrane oxygenation and mechanical ventilation were associated with increased risk of WM in all cohorts.
Conclusions: There is significant variability in WM among status-1A patients. Potential refinements to current allocation system should factor in the increased WM risk we identified in patients supported by extracorporeal membrane oxygenation or mechanical ventilation, single ventricle congenital heart disease on VAD support and small children with congenital heart disease, restrictive cardiomyopathy, or hypertrophic cardiomyopathy.
Keywords: cardiomyopathies; eart defects, congenital; heart-assist device; mortality; pediatrics; transplantation.