Donor and Recipient Size Matching in Heart Transplantation with Predicted Heart and Lean Body Mass

Donor and recipient size matching during heart transplant can be assessed using weight or predicted heart mass (PHM) ratios. We developed sex-specific allomteric equations for PHM and predicted lean body mass (PLBM) using the United Kingdom Biobank (UKB) and evaluated their predictive value in the United Network of Organ Sharing (UNOS) database. Donor and recipient size matching was based on weight, PHM and PLBM ratios. PHM was calculated using the Multi-ethnic Study of Atherosclerosis and UKB equations. PLBM was calculated using the UKB and National Health and Nutrition Examination Survey (NHANES) equations. Relative prognostic utility was compared using multivariable Cox analysis, adjusted for predictors of one-year survival in the Scientific Registry of Transplant Recipients (SRTR) model. Of 53,648 adult patients in the UNOS database between 1996 and 2016, 6528 (12.2%) died within the first year. In multivariable analysis, undersized matches by any metric were associated with increased one-year mortality (all p<0.01). Oversized matches were at increased risk using PHM or PLBM (all p<0.01), but not weight ratio. There were significant differences in classification of size matching by weight or PHM in sex-mismatched donor-recipient pairs. A significant interaction was observed between pulmonary hypertension and donor undersizing (hazard ratio 1.15, p=0.026) suggesting increased risk of undersizing in pulmonary hypertension. Donor and recipient size matching with simplified PHM and PLBM offered an advantage over total body weight and may be more important for sex-mismatched donor-recipient pairs. Donor undersizing is associated with worse outcomes in patients with pulmonary hypertension.