Ideal Body Weight Ratio for Donor-to-Recipient Size Matching in Heart Transplantation

While various models are useful for donor-recipient size matching, the optimal approach for predicting the correct match remains unclear. We sought to determine the association between ideal body weight (IBW) ratio and post-transplant survival.

The United Network for Organ Sharing (UNOS) database was queried for all patients who underwent isolated heart transplantation between July 2000 and July 2023. Donor-recipient size matching was assessed using predicted heart mass (PHM), ideal predicted heart mass (IPHM), and IBW. Ratios were stratified as undersized (≤0.8), properly sized (>0.8 to <1.2), and oversized (≥1.2). Stratified Kaplan-Meier analysis was conducted using the log-rank test. Restricted cubic splines (RCS) were constructed to evaluate the association with mortality.

A total of 46 721 donor-recipient matches were identified. PHM demonstrated higher survival for properly sized and oversized patients compared to undersized (p < 0.01). For IPHM, survival was highest in the properly sized patients, lower in the oversized, and lowest in the undersized patients (p < 0.01). For IBW, survival was superior in properly sized group compared to undersized and oversized patients (p < 0.03). Non-linear analysis of PHM showed increased mortality risk with undersizing and decreased risk with oversizing (p < 0.01). IPHM demonstrated higher mortality risk with undersizing but no notable risk with oversizing (p < 0.01), whereas IBW showed increased risk with both undersizing and oversizing (p < 0.01).

The IBW model appears to be non-inferior to PHM. IBW penalized equally for both undersizing and oversizing, making it potentially an additional useful metric in the evaluation of donor-recipient size matching.