Increased Short- and Long-term Mortality at Low-volume Pediatric Heart Transplant Centers: Should Minimum Standards Be Set? Retrospective Data Analysis

Objective: The relationship between volume and outcome in many complex surgical procedures is well established.

Background: No published data has examined this relationship in pediatric cardiac transplantation, but low-volume adult heart transplant programs seem to have higher early mortality.

Methods: 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.

Results: 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).

Conclusion: 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.