Predicted Heart Mass in Obese Heart Transplant Donors and Recipients: An Analysis of the ISHLT Registry

Abstract

<h3>Purpose</h3> Predicted heart mass (PHM) was neither derived nor validated in an obese population. Our objectives were to determine survival according to size mismatch defined by actual PHM and recalculated PHM using ideal body weight (IBW) in obese recipients or recipients of obese donors, and to evaluate whether size mismatch using IBW-adjusted PHM improves risk assessment. <h3>Methods</h3> We included HT recipients (≥18 y) with BMI ≥30 kg/m² or recipients of donors with BMI ≥30 kg/m² from the ISHLT registry between 2008-2017. IBW was calculated using Devine's formula. Donor-recipient PHM was evaluated as a continuous variable and according to established groups: <-30%, -30 to -20%, -20 to 20%, 20 to 30% and >30%. We used Kaplan-Meier survival and multivariable Cox PH analyses to evaluate post-HT mortality by actual/IBW-adjusted PHM groups. We compared the 2 models using net reclassification index (NRI). <h3>Results</h3> We included 10,817 HT recipients, age 55 (IQR 46-62) yrs, 23% female, BMI 31 kg/m² (28-33) with follow up of 3.1 (1.2-6.0) yrs. Included donors were 34 (24-44) yrs, 31% female, and BMI 31 kg/m² (26-34). 692 (6%) and 335 (3%) recipient-donor pairs were reclassified as undersized by 20-30% and >30% respectively using IBW-adjusted PHM. 462 (4%) and 431 (4%) recipient-donor pairs were reclassified as oversized by 20-30% and >30% respectively when using IBW-adjusted PHM. Actual PHM was associated with lower 1-year survival (<i>p</i><0.001); however, differences in 1-year survival between IBW-adjusted PHM groups were not discernible (<i>p</i>=0.25). Undersizing using actual PHM was associated with higher 1-year mortality (<i>p</i><0.001), not seen with IBW-adjusted PHM (p=0.15 Fig). Models based on IBW-adjusted PHM had worse risk quantification for post-HT mortality than using actual PHM (category-free NRI -0.078, 95% CI -0.158, 0.006). <h3>Conclusion</h3> Calculation of PHM using IBW was not associated with post-HT survival. Actual PHM can be used for size matching when assessing mortality risk in recipients of obese donors or obese recipients.