# Alternative Measures of Body Composition and Outcomes Following Heart Transplant

## TL;DR

This study examines if body composition metrics beyond BMI better predict outcomes after heart transplants, finding that BMI is more useful than other measures for predicting readmissions and infections.

## Contribution

The study evaluates alternative body composition metrics as predictors of post-HT outcomes, revealing BMI's unique predictive value for readmission and infection risks.

## Key findings

- Highest and lowest BMI tertiles were significantly associated with increased hospital readmission and infection risks.
- Other body composition metrics like FMI, VAT/SAT, FFMI, and SMI were not associated with poor post-HT outcomes.
- BMI does not predict mortality but better differentiates readmission and infection risks than other metrics.

## Abstract

Current guidelines for heart transplant (HT) listing support body mass index (BMI) < 35 kg/m2, though data supporting this recommendation is mixed. It is unclear if other more specific measurements of body composition are better predictors of outcomes post‐HT. This retrospective study included patients who underwent HT between 2014 and 2019 and underwent an abdominal CT scan within 3 months of HT. Tissue characterization was performed using Slice‐O‐Matic software to derive measurements including BMI, fat mass index (FMI), visceral adipose tissue to subcutaneous adipose tissue ratio (VAT/SAT), fat free mass index (FFMI), and skeletal muscle index (SMI). Univariate and multivariate logistic regression analyses were used to investigate association of body composition variables by tertiles to 1 year mortality, readmission, primary graft dysfunction, length of stay, infection, and renal failure. Of the 104 patients, 80% were male and 56% were Caucasian. Highest and lowest BMI tertiles were significantly associated with an increased risk of hospital readmission within 1 year post HT (OR 3.4, [95%CI 1.1–11.4]; OR 5.9, [95% CI 1.7–25.1]; p = 0.01) as well as an increased risk of infections requiring hospitalization (OR 3.2, [95% CI 1.2–9.0]; OR 3.9, [95%CI 1.4–11.7]; p = 0.02). FMI, VAT/SAT, FFMI, and SMI were not associated with outcomes 1‐year post‐HT. Highest and lowest BMI tertiles were associated with increased rates of hospital readmission and infection in the first‐year post HT, while other measurements of body composition were not associated with any poor outcomes post‐HT. Although BMI does not predict mortality post‐HT, it can differentiate risk better than all other metrics.