Predicted heart mass for size matching in obese heart transplant donors and recipients

Introduction Predicted heart mass (PHM) was neither derived nor evaluated in an obese population. Our objective was to evaluate size mismatch using actual body weight or ideal body weight (IBW)‐adjusted PHM on mortality and risk assessment. Methods We conducted a retrospective cohort study of adult recipients with BMI ≥30 kg/m 2 or recipients of donors with BMI≥30 kg/m 2 from the ISHLT registry. We used multivariable Cox proportional hazard models to evaluate 30‐day and 1‐year mortality. The two models were compared using net reclassification index. Results 10,817 HT recipients, age 55 (IQR 46–62) years, 23% female, BMI 31 kg/m 2 (IQR 28–33) were included. Donors were age 34 (IQR 24–44) years, 31% female, and BMI 31 kg/m 2 (IQR 26–34). There was a significant nonlinear association between mortality and actual PHM but not IBW‐adjusted PHM. Undersizing using actual PHM was associated with higher 30‐day and 1‐year mortality ( p < .01), not seen with IBW‐adjusted PHM. Actual PHM better risk classified .6% (95% CI .3–.8) patients compared to IBW‐adjusted PHM. Conclusion Actual PHM can be used for size matching when assessing mortality risk in obese recipients or recipients of obese donors. There is no advantage to re‐calculating PHM using IBW to define candidate risk at the time of organ allocation.