The Effect of Institutional Volume on Complications and Their Impact on Mortality After Pediatric Heart Transplantation

Abstract

Background: This study evaluated the potential association of institutional volume with survival and mortality subsequent to major complications in a modern cohort of pediatric patients after orthotopic heart transplantation (OHT).

Methods: The United Network of Organ Sharing database was queried for pediatric patients (aged ≤18 years) undergoing OHT between 2000 and 2010. Institutional volume was defined as the average number of transplants completed annually during each institution's active period and was evaluated as categoric and as a continuous variable. Logistic regression models were used to determine the effect of institutional volumes on postoperative outcomes, which included renal failure, stroke, rejection, reoperation, infection, and a composite complication outcome. Cox modeling was used to analyze the risk-adjusted effect of institutional volume on 30-day, 1-year, and 5-year mortality. Kaplan-Meier estimates were used to compare differences in unconditional survival.

Results: A total of 3,562 patients (111 institutions) were included and stratified into low-volume (<6.5 transplants/year, 91 institutions), intermediate-volume (6.5 to 12.5 transplants/year, 12 institutions), and high-volume (>12.5 transplants/year, 8 institutions) tertiles. Unadjusted survival was significantly different at 30 days (p = 0.0087) in the low-volume tertile (94.2%; 95% confidence interval, 92.7% to 95.4%) compared with the high-volume tertile (96.8%; 95% confidence interval, 95.7% to 97.7%). No difference was observed at 1 or 5 years. Risk-adjusted Cox modeling demonstrated that low-volume institutions had an increased rate of mortality at 30 days (hazard ratio, 1.91; 95% confidence interval, 1.02 to 3.59; p = 0.044), but not at 1 or 5 years. High-volume institutions had lower incidences of postoperative complications than low-volume institutions (30.3% vs 38.4%, p < 0.001). Despite this difference in the rate of complications, survival in patients with a postoperative complication was similar across the volume tertiles.

Conclusions: No association was observed between institutional volume and adjusted or unadjusted long-term survival. High-volume institutions have a significantly lower rate of postoperative complications after pediatric OHT. This association does not correlate with increased subsequent mortality in low-volume institutions. Given these findings, strategies integral to the allocation of allografts in adult transplantation, such as regionalization of care, may not be as relevant to pediatric OHT.