Johan Nilsson and Mattias Ohlsson and Peter Höglund and Björn Ekmehag and Bansi Koul and Bodil Andersson
The International Heart Transplant Survival Algorithm (IHTSA): a new model to improve organ sharing and survival
LU TP 15-05

Background: Heart transplantation is life saving for patients with end-stage heart disease. However, a number of factors influence how well recipients and donor organs tolerate this procedure. The main objective of this study was to develop and validate a flexible risk model for prediction of survival after heart transplantation using the largest transplant registry in the world.

Methods and Findings: We developed a flexible, non-linear artificial neural networks model (IHTSA) and a classification and regression tree to comprehensively evaluate the impact of recipient-donor variables on survival over time. We analyzed 56,625 heart-transplanted adult patients, corresponding to 294,719 patient-years. Furthermore, we compared the discrimination power with three existing scoring models, donor risk index (DRI), risk-stratification score (RSS) and the index for mortality prediction after cardiac transplantation (IMPACT). The accuracy of the model was excellent (C-index 0.600 [95% CI: 0.595-0.604]) and a predicted versus actual 1- year, 5-year and 10-year survival rates of 83.7% versus 82.6%, 71.4%-70.8%, and 54.8%-54.3% in the derivation cohort; 83.7% versus 82.8%, 71.5%-71.1%, and 54.9%- 53.8% in the internal validation cohort; and 84.5% versus 84.4%, 72.9%-75.6%, and 57.5%-57.5% in the external validation cohort. The IHTSA model showed superior or similar discrimination in all of the cohorts. The receiver operating characteristic area under the curve to predict one-year mortality was for the IHTSA: 0.650 (95% CI: 0.640- 0.655), DRI 0.56 (95% CI: 0.56-0.57), RSS 0.61 (95% CI: 0.60-0.61), and IMPACT 0.61 (0.61-0.62), respectively. The decision-tree showed that recipients matched to a donor younger than 38 years had an additional expected median survival time of 2.8 years. Furthermore, the number of suitable donors could be increased by up to 22%.

Conclusions: We show that the IHTSA model can be used to predict both short-term and long-term mortality with high accuracy globally. The model also estimates the expected benefit to the individual patient.

LU TP 15-05