The effect of body mass index on survival following heart transplantation: do outcomes support consensus guidelines?

Abstract

To determine the relationship between body mass index (BMI) at the time of transplant and posttransplant survival and morbidity. The recent International Society for Heart and Lung Transplantation listing criteria for heart transplantation stated that candidates should achieve a BMI <30 kg/m-or percent ideal body weight <140%-before listing for cardiac transplantation. However, data to support these recommendations are limited and often conflicting. United Network of Organ Sharing provided de-identified patient-level data. Analysis included 19,593 orthotopic heart transplant recipients aged >or=18 years and transplanted January 1 1995-December 31 2005. Follow-up data were provided through February 8, 2008. Recipients were stratified by BMI at the time of transplantation: BMI <18.5 (underweight), 18.5 to 24.99 (normal weight), 25 to 29.99 (overweight), 30 to 34.99 (obesity class I), and >or=35 (obesity class II/III). The primary outcome measure was post-transplant survival. Risk-adjusted median survival in the underweight, normal weight, overweight, obesity I, and obesity II/III groups was 8.31, 10.20, 10.03, 9.51, and 9.05 years, respectively. In multivariate Cox proportional hazards regression, BMI in the overweight (HR = 1.08, 0.99-1.17; P = 0.055) and obesity I (HR = 1.05, 0.99-1.12; P = 0.091) ranges were not associated with significantly diminished survival. However, BMI in the underweight (HR = 1.26, 1.11-1.43; P < 0.001) and obesity II/III (HR = 1.18, 1.01-1.38; P = 0.030) ranges were associated with diminished posttransplant survival. Findings from this analysis do not suggest that obesity I (BMI of 30-34.99) is associated with significantly higher morbidity and mortality. However, underweight and obesity II/III recipients have significantly higher morbidity and mortality compared with other groups.