EXTERNAL VALIDATION OF CURRENT INTERNATIONAL SHORT- AND LONG-TERM PROGNOSTIC MODELS FOR SURVIVAL IN HEART TRANSPLANT RECIPIENTS USING MARGINAL DONOR HEARTS AT SINGLE JAPANESE CENTER

Abstract

Introduction: Current prognostic models to predict survival in heart transplant (HTx) recipients, which are ‘Index for Mortality Prediction After Cardiac Transplantation (IMPACT) model’ using the recipient-factor and ‘International Heart Transplantation Survival Algorithm (IHTSA) model’ using both recipient- and donor-factors, have been verified the good adaptation on the global registry data in HTx recipients. In Japan, extremely serious donor shortages will necessitate a long waiting period, and using more marginal donor hearts. But several donor risk factors for HTx were not included enough in these prognostic models. It is unclear whether these prognostic models can be adapted with HTx using more marginal donor hearts. This study aimed to validate the usefulness of IMPACT and IHTSA models for the prediction of long-term mortality in recipients transplanted marginal hearts. Materials and Methods: Consecutive 126 adult HTx recipients who underwent HTx between May 1999 and February 2020 were included in this study. The risk score based on IMPACT model was calculated for each recipient. And we entered the clinical data of each recipient and donor into the web-based calculator of the IHTSA model and calculated predicted 5-year mortality rate based on the IHTSA model. The discrimination for survival in our subjects was evaluated using Harrell’s concordance index (C-index). Survival analysis was conducted to evaluate the actual mortality rate in our subjects. Results and Discussion: Over median follow-up of 4.9 years [interquartile range (IQR); 2.6-9.0 years] after HTx, 8 recipients (6.3%) died during follow-up. The IMPACT score was median of 6.0 (IQR; 3.0-8.0), and the estimated 5-year mortality rate based on IHTSA model was median of 0.25 (IQR; 0.21-0.29). The predicted versus actual 5-year survival rates were 73.7% versus 95.8%. The discrimination (C-index) for survival using IMPACT score and 5-year mortality rate based on the IHTSA model were 0.689 and 0.720, respectively. Conclusion: This study validated a usefulness of two current prognostic models, IMPACT and IHTSA, for survival in HTx recipients using marginal donor hearts. Our results suggest that these models might be useful even in HTx recipients using highly marginal donor hearts. Further validation is needed to adapt an appropriate prognostic model in such clinical situation as serious donor shortages.