Impact of Recipient Body Mass Index on Organ Allocation and Mortality in Orthotopic Heart Transplantation

Background: It is unknown whether obesity affects organ allocation in orthotopic heart transplantation (OHT). The United Network for Organ Sharing (UNOS) database provides an opportunity to examine this issue. Methods: We reviewed UNOS data to identify 27,002 OHT candidates placed on the heart transplantation wait list (1998 to 2007). Patients were stratified by body mass index (BMI) at listing. Multivariate Cox proportional hazards model estimated the chance of receiving OHT, adjusting for factors that might affect allocation. Mortality on the wait list and post-OHT mortality were estimated using the Kaplan-Meier method. Results: Of 27,002 patients listed, the distribution of BMI was as follows: BMI 18.5 to 24.9, n = 9,734 (36.0%); BMI 25 to 29.9, n = 10,063 (37.2%); BMI 30 to 34.9, 5,500 (20.4%); and BMI ≥35, 1,705 (6.3%). BMI was strongly associated with a decrease in the likelihood of receiving OHT once on the wait list (hazard ratio [HR] 0.96, 95% confidence interval [CI] 0.95 to 0.96, p < 0.001). Patients with BMI ≥35 had a 46% lower likelihood of receiving a donor heart after risk adjustment (HR 0.54, 95% CI 0.49 to 0.60, p < 0.001). On the wait list, patients with extreme BMIs (≥35) who were listed as UNOS Status 1 had the lowest cumulative survival (61% at 3 years). After OHT, patients with high BMI did not have increased short-term mortality at 30 days, 90 days or 1 year. Conclusions: Obese individuals wait longer and have a lower likelihood of receiving a donor heart after listing, despite similar short-term survival. The results of this study point to a potential provider bias for obese individuals in OHT.