Novel Methods for Donor and Recipient Size Matching in Heart Transplantation

Abstract

Heart donor and recipient size matching is associated with improved post-transplant outcomes. Many programs use total body weight ratios, which do not account for body composition or heart specific mass. We derived equatinos for lean body mass (LBM) and predicted heart mass (PHM) in the UK Biobank (UKB), and determined associations with survival using the United Network for Organ Sharing (UNOS) database. We derived LBM and PHM equations from 2846 participants in the UKB who underwent cardiac MRI and dual-energy X-ray absorptiometry for body composition analysis. Prognostic utility was validated in adults patients in the UNOS database between January 1996 and November 2017. Donor-recipient size matching was based on five methods: weight ratio, two methods for LBM ratio (National Health and Nutrition Examination Survey [NHANES] and UKB) and two methods for PHM ratios (Multi-ethnic Study of Atherosclerosis [MESA] and UKB). Relative prognostic utility was compared using multivariable Cox analysis adjusted for variables in the SRTR one year patient survival equation. Donor-recipient matching was defined as < 0.8 (undersized), 0.8 to 1.2 (matched) or > 1.2 (oversized). In the validation cohort, 6528 of 53,648 patients (12.2%) died within the first year. In multivariable analysis, undersized matches were associated with increased one-year mortality for all methods (p<0.01). Oversized matches by LBM or PHM ratios (adjusted HR 1.08 - 1.15, all p<0.05) were also associated with increased one-year mortality. Donor oversizing by UKB LBM was associated with worse outcomes in female donors to male recipients (Figure, interaction p=0.001). Significant under or oversizing of donor hearts, predicted using either of LBM or PHM algorithms, was associated with worse one-year survival following cardiac transplantation. Donor-recicipient sex mismatches should also be considered when using LBM and PHM based ratios.