Iso-risk curves as a tool for clinical decision-making: Donor factors and medical urgency in cardiac transplantation

Background: No significant improvement of overall graft survival in cardiac transplantation has occurred during the past decade, notwithstanding the i dentification of several prognostic donor and recipient risk factors. By tr anslating multivariate results into iso-risk curves plots, stratified for m edical urgency, we attempt to present results in a more practical manner, t o be used as guidelines at the time of donor heart offer and of allocation. Methods: We analyzed all first heart-only transplants performed in adults a nd carried out between January 1, 1997, and June 30, 1998 (N = 1120). Befor e transplant, 687 patients were at home, 233 on hospital wards, and 200 on the intensive care unit. The overall Cox model yielded 5 independent factor s associated with 1-year graft outcome: donor age, donor:recipient weight r atio, medical urgency, end-stage heart disease, and transplant country. We used the significant donor variables of donor age and donor: recipient weig ht ratio for the iso-risk curves; we calculated relative risks for all comb inations of donor age and donor:recipient weight ratio. We obtained iso-ris k curves by linking equal relative risks. Results: All iso-risk curves showed that with older donor age, the donor:re cipient weight ratio must be higher to obtain the same relative risk for al l 3 medical urgency groups. The more urgent the heart transplant candidate, the higher the course of the iso-risk curve for all donor ages. Conclusions: Iso-risk curve is an elegant tool for presenting multivariate analyses in a more practical and patient-oriented manner. The more understa ndable prognostic factors become the more likely we are to achieve better r esults in cardiac transplantation and to use more optimally donor hearts. A s an example, we have demonstrated the interaction between donor age, donor :recipient size ratio, and, medical urgency.