The HeartMate II Risk Score: An Adjusted Score for Evaluation of All Continuous-Flow Left Ventricular Assist Devices

The aim of this study was to evaluate the performance of an adjusted HeartMate II risk score (HMRS) in Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS; n = 9,733) and in HeartWare Ventricular Assist Device (HVAD) bridge to transplant (BTT) trial patients (n = 360). Interagency Registry for Mechanically Assisted Circulatory Support data were used to calculate an adjusted HMRS, omitting center volume, for all patients on continuous-flow left ventricular assist device (LVAD) support. Ninety day mortality was then evaluated in INTERMACS and HVAD-BTT patients. Four risk groups were identified based on INTERMACS patient-adjusted HMRS: very low (<5%, 90 day mortality; score <0.20), low (5-10%, 90 day mortality; score 0.20-1.97), medium (10-20%, 90 day mortality; score 1.98-4.48), and high risk (>20%, 90 day mortality; score >4.48). Within INTERMACS, there were significant differences in survival between all-adjusted HMRS risk groups (p < 0.001 in pairwise comparisons). Controlling for known mortality correlates, the adjusted HMRS mortality hazard ratio was 1.19 (1.25-1.23) per unit HMRS increase. The HVAD cohort was a low-risk cohort with 90 day survivals for very low-, low-, and medium-risk patients of 100%, 97 ± 1.1%, and 90 ± 3.6%, respectively (p = 0.007). Patients in the very low- and low-risk group had significantly improved survival compared with medium-risk patients, respectively (both p < 0.05). The adjusted HMRS appropriately risk stratified a large cohort of INTERMACS patients and was predictive of survival in HeartWare-supported patients.