Size matching in combined heart-lung transplant: An undersized predicted heart mass is associated with increased mortality

Background: Numerous studies have analyzed the consequences of donor-recipient organ size mismatch within both heart and lung transplantation. However, there is very little data on size matching in combined heart-lung transplantation (HLTx). We reviewed how donor/recipient predicted total lung capacity (pTLC), predicted heart mass (pHM), weight, and height ratios affect HLTx survival and graft rejection outcome.

Methods: We performed a retrospective analysis on adult HLTx patients using the UNOS database. Overall survival at 1- and 5-years, as well as 5-years bronchiolitis obliterans syndrome (BOS) and coronary artery vasculopathy (CAV) development, were the outcomes of interest. Each sizing modality was split into 5 groups for survival analysis and 3 groups for graft rejection analysis based on an approximately equal size-matched reference group.

Results: In total, 747 patients were analyzed in our study. Of the 4 sizing modalities, only pHM ratio had a significant difference in acute and long-term survival. In particular, a severely undersized pHMr of < 83% was associated with an increased risk of mortality compared to an approximately equally sized match (1-year: HR=1.95, 95% CI=1.30-2.91, p = 0.001; 5-year: HR = 1.47, 95% CI = 1.05-2.06, p = 0.027). No sizing metric was predictive of BOS or CAV development.

Conclusion: Our analysis supports the use of pHM ratio for size matching in HLTx. Based on our results, a donor/recipient pHM ratio of >83% should be achieved to minimize mortality risk associated with sizing mismatch.