To evaluate the applicability of the index for mortality prediction after cardiac transplantation (IMPACT) and the United Organ Allocation Network (UNOS) scoring model in the heart transplant population of Fuwai Hospital of Chinese Academy of Medical Sciences (hereinafter referred to as Fuwai Hospital).

The clinical data of 914 recipients underwent heart transplant in Fuwai Hospital from January 2005 to December 2019 were retrospectively analyzed. The primary outcome was post-transplant 1-year all-cause mortality, and the secondary outcome was the in-hospital mortality. The risk score of each recipient and the 1-year predicted mortality were calculated according to the IMPACT and UNOS scoring models. Total 914 recipients were divided into three subgroups according to the time of transplantation: 2005-2009, 2010-2014 and 2015-2019. The 914 recipients were also divided into low-risk, intermediate-risk and high-risk groups based on IMPACT scores of <5, 5-<10, and ≥10 points, and UNOS scores of 0-2, 3-5, and >5 points. Normally distributed measurement data between groups were compared by group t test or one-way analysis of variance, non-normally distributed measurement data were compared by Mann-Whitney U test, and count data were compared by Chi-square test. Binary Logistic regression was used to analyze the correlation between IMPACT and UNOS score values and the in-hospital and 1-year postoperative mortality. The receiver operating characteristic (ROC) curve was used to evaluate the predictive performance of IMPACT and UNOS scoring models on the 1-year mortality rate of 914 recipients and the subgroups, and the area under curve (AUC) was calculated. The Kaplan-Meier method was used to draw survival curves of heart transplant recipients in the low-, intermediate- and high-risk groups, and the log-rank test was used for comparison. P<0.05 indicates that the difference is statistically significant.

The median IMPACT score of the Fuwai Hospital heart transplant cohort was 3 points (0-26 points), and the median UNOS score was 3 points (0-11 points). Logistic regression analysis results suggest that the increased IMPACT and UNOS scores are correlated with increased risk for in-hospital mortality [(OR=1.25, 95%CI: 1.18-1.34, P<0.05) and (OR=1.77, 95%CI: 1.48-2.12), P<0.05)] and 1-year mortality [(OR=1.21, 95%CI: 1.13-1.28, P<0.05) and (OR=1.58, 95%CI: 1.35-1.84, P<0.05)]. The 1-year mortality rates of 914 recipients predicted by IMPACT and UNOS score were 9.91% and 11.20% respectively, and the correction coefficients were 0.65 and 0.58 respectively. The ROC AUC of the IMPACT score for prediction of 1-year mortality was 0.662 (95% CI: 0.587-0.736, P<0.05), and the sensitivity was 49.2% and the specificity was 72.9% when the cut-off value was 0.10. The ROC AUC of the UNOS score for prediction of 1-year mortality was 0.661 (95% CI: 0.586-0.736, P<0.05), and the sensitivity was 81.4% and the specificity was 40.0% when the cut-off value was 0.10. The prediction efficacies of the IMPACT and UNOS scores were both poor, with the ROC AUC was less than 0.7 in population of different periods except for the UNOS score used in the population underwent heart transplant in the period of 2005-2009 (AUC=0.799). Based on the IMPACT score, the in-hospital mortality rates in the low-, intermediate-, and high-risk groups were 2.9%, 5.3%, and 34.3%, and the 1-year mortality rates were 4.6%, 7.5%, and 34.3%, the differences were both statistically significant (χ²=73.2 and 49.1, all P<0.05); the predicted 1-year mortality rates were 7.8%, 12.4%, and 32.1% respectively. Based on the UNOS scoring model, the in-hospital mortality rates in the low-, intermediate-, and high-risk groups were 1.7%, 4.5%, and 28.0%, and the 1-year mortality rates were 3.1%, 6.7%, and 28.0%, the differences were both statistically significant (χ²=67.7 and 45.0, all P<0.05); the predicted 1-year mortality rates were 7.0%, 13.0%, and 22.0%, respectively. Based on the IMPACT scoring model, the 10-year survival rates of the low-, intermediate-, and high-risk groups were 79.0%, 72.5%, and 52.3%, respectively, and the difference was statistically significant (χ²= 26.7, P<0.05); Based on the UNOS scoring model, the 10-year long-term survival rates of low-, intermediate- and high-risk groups were 82.0%, 76.4%, and 57.3%, respectively, and the difference was statistically significant (χ²= 29.4, P<0.05).

The IMPACT and UNOS scoring models can reflect the surgical risk of Chinese heart transplant recipients to a certain extent, but the accuracy is not good. It is urgent to establish a survival risk prediction model suitable for Chinese heart transplant recipients.