Increased Short- and Long-term Mortality at Low-volume Pediatric Heart Transplant Centers

Abstract

The relationship between volume and outcome in many complex surgical procedures is well established. No published data has examined this relationship in pediatric cardiac transplantation, but low-volume adult heart transplant programs seem to have higher early mortality. The United Network for Organ Sharing (UNOS) provided center-specific data for the 4647 transplants performed on patients younger than 19 years old, 1992 to 2007. Patients were stratified into 3 groups based on the volume of transplants performed in the previous 5 years at that center: low [<19 transplants, n = 1135 (24.4%)], medium [19–62 transplants, n = 2321(50.0%)], and high [≥63 transplants, n= 1191 (25.6%)]. A logistic regression model for postoperative mortality was developed and observed-to-expected (O:E) mortality rates calculated for each group. Unadjusted long-term survival decreased with decreasing center volume (P<0.0001). Observed postoperative mortality was higher than expected at low-volume centers [O:E ratio 1.39, 95% confidence interval (CI) 1.05–1.83]. At low volume centers, high-risk patients (1.34, 0.85–2.12)--especially patients 1 year old or younger (1.60, 1.07–2.40) or those with congenital heart disease (1.36, 0.94–1.96)--did poorly, but those at high-volume centers did well (congenital heart disease: 0.90, 0.36–1.26; age<1 year: 0.75, 0.51–1.09). Similar results were obtained in the subset of patients transplanted after 1996. In multivariate logistic regression modeling, transplantation at a low-volume center was associated with an odds ratio for postoperative mortality of 1.60 (95% CI, 1.14–2.24); transplantation at a medium volume center had an odds ratio of 1.24 (95% CI, 0.92–1.66). The volume of transplants performed at any one center has a significant impact on outcomes. Regionalization of care is one option for improving outcomes in pediatric cardiac transplantation.