Rethinking Donor and Recipient Risk Matching in Europe and North America: Using Heart Transplant Predictors of Donor and Recipient Risk

Abstract

Background: In Europe, there is greater acceptance of hearts from higher-risk donors for transplantation, whereas in North America, the donor heart discard rate is significantly higher. A Donor Utilization Score (DUS) was used to compare European and North American donor characteristics for recipients included in the International Society for Heart and Lung Transplantation registry from 2000 to 2018. DUS was further evaluated as an independent predictor for 1-year freedom from graft failure, after adjusting for recipient risk. Lastly, we assessed donor-recipient risk matching with the outcome of 1-year graft failure.

Methods: DUS was applied to the International Society for Heart and Lung Transplantation cohort using meta-modeling. Posttransplant freedom from graft failure was summarized by Kaplan-Meier survival. Multivariable Cox proportional hazard regression was applied to quantify the effects of DUS and Index for Mortality Prediction After Cardiac Transplantation score on the 1-year risk of graft failure. We present 4 donor/recipient risk groups using the Kaplan-Meier method.

Results: European centers accept significantly higher-risk donor hearts compared to North America. DUS 0.45 versus 0.54, P<0.005). DUS was an independent predictor for graft failure with an inverse linear relationship when adjusted for covariates (P<0.001). The Index for Mortality Prediction After Cardiac Transplantation score, a validated tool to assess recipient risk, was also independently associated with 1-year graft failure (P<0.001). In North America, 1-year graft failure was significantly associated with donor-recipient risk matching (log-rank P<0.001). One-year graft failure was highest with pairing of high-risk recipients and donors (13.1% [95% CI, 10.7%-13.9%]) and lowest among low-risk recipients and donors (7.4% [95% CI, 6.8%-8.0%]). Matching of low-risk recipients with high-risk donors was associated with significantly less graft failure (9.0% [95% CI, 8.3%-9.7%]) than high-risk recipients with low-risk donors (11.4% [95% CI, 10.7%-12.2%]) Conclusions: European heart transplantation centers are more likely to accept higher-risk donor hearts than North American centers. Acceptance of borderline-quality donor hearts for lower-risk recipients could improve donor heart utilization without compromising recipient survival.

Keywords: United States; heart transplantation; machine learning; risk; tissue donor.

Figure 1.

Flow diagram showing European (left) and North American (right) study cohorts

Figure 2A.

Freedom from graft failure among European (red) and North American (blue) heart transplant recipients. 2B. European (left panel) and North American (right panel) freedom from graft failure stratified by Donor Utilization Score

Figure 3.

The plots show the adjusted hazard ratio of early graft failure for the continuous variables modelled as restricted cubic splines within the multivariate analysis.

Figure 4.

Comparison of donor estimated DUS with the IMPACT score of the recipient. Higher risk donor hearts were used for high-risk recipients and lower risk donor hearts were used for lower risk recipients showing the crisscrossed darker pattern.

Figure 5.

Proportion of 1-year graft failure stratified by donor and recipient risk profiles (red: high risk recipients and donors; blue: high risk recipients and low risk donors purple: low risk recipients and high risk donors; green: low risk recipients and donors)