The HeartMate Risk Score Identifies Patients With Similar Mortality Risk Across All INTERMACS Profiles in a Large Multicenter Analysis

Objectives This study sought to assess the performance of the HeartMate Risk Score (HMRS) in a large multicenter cohort, with a focus on its performance as a function of disease severity. Background The HMRS has been proposed as a simple tool for risk stratification of LVAD recipients, but subsequent studies have challenged its validity. Methods We performed a retrospective, longitudinal, comparative study using the INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) database. The HMRS was calculated for each patient and its association with mortality was assessed using Cox models, including a pre-specified interaction by INTERMACS profile groups (1 vs. 2 vs. 3 vs 4+). Results Among 10,847 patients with a mean age of 57.0 ± 12.9 years, 78.9 % were male; and 14.1%, 37.4%, 30.4%, and 18.2% were in INTERMACS profile groups 1, 2, 3, and ≥4, respectively. The HMRS showed moderate discrimination for both short-term (90-day, C-index 0.62) and long-term (2-years, C-index 0.60) mortality, with no significant difference between axial and centrifugal devices. Patients in the highest HMRS group had a relative risk of 90-day mortality 2.8 times greater than those in the lowest HMRS group (13.0% vs. 4.7%; p < 0.001). Importantly, the relative risks of higher HMRS scores were similar across INTERMACS profile groups, with subgroups of patients in INTERMACS profile 1 and 2 having comparable or lower mortality than some in INTERMACS profile 4+. Conclusions The HMRS is a valid means of risk-stratifying patients across all INTERMACS profiles and may be superior to traditional INTERMACS classification. Risk stratification with the HMRS showed that patients within each INTERMACS profile groups have a wide spectrum of mortality risk and low INTERMACS profiles should therefore not be considered a contraindication to mechanical support.