Low body mass index is associated with increased waitlist mortality among children listed for heart transplant

In adults, low body mass index (BMI) and high BMI have been associated with increased mortality after heart transplantation. Studies of BMI in children with heart failure have had inconsistent results.

The United Network for Organ Sharing database has 4,035 listings for primary, isolated heart transplant in patients 3 to 18 years old (1995-2012). BMI percentile-for-age (BMI%) was calculated, and patients were stratified based on BMI% into 4 groups: underweight (BMI% <5, n = 701 [17.4%]), normal weight (BMI% 5-84, n = 2,321 [57.5%]), overweight (BMI% 85-94, n = 440 [10.9%]), or obese (BMI% ≥95, n = 573 [14.2%]). Outcomes of patients on the waitlist and after transplantation were assessed.

Unadjusted early waitlist mortality was highest in underweight patients (16.7%) compared with normal-weight (11.4%), overweight (10.9%), and obese (12.9%) patients (p = 0.04). In multivariable analysis, underweight patients had elevated risk-adjusted waitlist mortality (odds ratio = 1.4, 95% confidence interval = 1.0-2.2). Unadjusted post-transplant mortality did not differ across BMI% groups (underweight, 5.7%; normal weight, 5.4%; overweight, 5.5%; obese, 5.8%), but obese patients had borderline higher risk-adjusted post-transplant mortality (odds ratio = 1.7, 95% confidence interval = 1.0-3.0). Change in BMI% while waiting did not affect post-transplant mortality.

Children listed for heart transplant are commonly either underweight or obese. Underweight patients have high risk-adjusted mortality before transplantation, whereas obese patients have borderline higher adjusted post-transplant mortality.