Indexed Donor Cardiac Output for Improved Size Matching in Heart Transplantation

Abstract

<h3>Purpose</h3> Implantation of an appropriately sized donor heart is critical for optimal outcomes after heart transplantation. While predicted heart mass (PHM) has recently gained consideration, there remains a need for improved granularity in size matching, particularly among small donor hearts. We hypothesized that indexed donor cardiac output (CO) would be a sensitive metric to assess adequacy of a donor heart for a given recipient. <h3>Methods</h3> Isolated heart transplant recipients from the UNOS database were included if donor CO was reported (<i>N</i>=3,619). Donor CO was divided by recipient BSA to compute cardiac index (dCI) and PHM ratio (PHMr) was computed as donor/recipient PHM. The primary outcome was mortality <1 year after transplant, adjusting for age, gender, donor inotropes, and recipient hospitalization status. <h3>Results</h3> Among transplanted recipients, donor CO was 7.3 (5.8-9.0) LPM and dCI was 3.7 (3.0-4.6) LPM/m². PHMr was 1.01 (0.91-1.13). dCI moderately correlated with recipient weight (<i>r_s</i>=-0.18, <i>P</i><0.001), BSA (<i>r_s</i>=-0.18, <i>P</i><0.001), and PHMr (<i>r_s</i>=0.29, <i>P</i><0.001). In univariate analyses, higher dCI was associated with lower 1 year mortality risk (OR=0.89, <i>P</i>=0.042), but not strongly associated with stroke (<i>P</i>=0.176) or dialysis (<i>P</i>=0.161). Those in the highest dCI quartile (>4.4 LPM/m²) had a lower risk of death compared to those in the lowest quartile (<3.0 LPM/m²; <i>P</i>=0.027). After multivariable adjustment, higher dCI continued to be associated with lower 1 year mortality risk (OR=0.89, <i>P</i>=0.042; Figure). Recipients with PHMr<0.80 (<i>n</i>=227) had lower median dCI than those with PHMr≥0.80 (3.3 vs 3.7, <i>P</i><0.001). Among those with PHMr<0.80, higher dCI decreased the odds of 1 year mortality (OR=0.63, <i>P</i>=0.083). <h3>Conclusion</h3> Higher dCI was associated with a lower probability of 1 year mortality among patients undergoing heart transplantation and served to stratify mortality risk among those with a PHMr<0.80. dCI appears to be an effective tool for size matching and may serve as an adjunctive strategy among small donor hearts with a low PHMr.