Predictive Value of HeartMate Risk Score
What is the validity of the HeartMate Risk Score (HMRS)?
The investigators performed a retrospective, longitudinal, comparative study using the INTERMACS (Interagency Registry for Mechanically Assisted Circulatory Support) database. They calculated HMRS for each patient and assessed its association with mortality using Cox models. To maintain consistency with current clinical practice and previously published studies, they subsequently categorized HMRS into low (<1.58), mid (1.58-2.48), and high (>2.48). To explore the applicability of the HMRS score to centrifugal devices, they built a Cox model including the variable axial versus centrifugal device type and they studied the interaction between HMRS and this variable, including a prespecified interaction by INTERMACS profile groups (1 vs. 2 vs. 3 vs. 4).
The study cohort was comprised of 10,847 patients with a mean age of 57.0 ± 12.9 years, 88.8% received an axial device, 78.9 % were male and predominantly white; and 14.1%, 37.4%, 30.4%, and 18.2% were in INTERMACS profile groups 1, 2, 3, and ≥4, respectively. The investigators found that HMRS showed moderate discrimination for both short-term (90-day, C-index 0.62) and long-term (2-year, C-index 0.60) mortality, with no significant difference between axial and centrifugal devices. The HMRS, as a continuous variable, was strongly associated with 90-day mortality (hazard ratio [HR], 1.32; 95% confidence interval [CI], 1.26-1.38, for each unit increase in HMRS). 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 (12.9% vs. 4.6%; p < 0.001) and 1.6 times greater than those in the mid-HMRS group (unadjusted rates, 12.9% vs. 8.2%; p < 0.001). They found similar results for 1-year (HR, 1.27; 95% CI, 1.23-1.32) and 2-year mortality (HR, 1.25; 95% CI, 1.21-1.29). 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 (1 vs. 2 vs. 3 vs. ≥4; p = 0.85).
The investigators concluded that HMRS is not only a valid score for risk-stratifying patients across all INTERMACS profiles, but may be superior to traditional INTERMACS classification. They argued that low INTERMACS profiles should therefore not be considered a contraindication to mechanical support because of their findings, that risk stratification with the HMRS within each INTERMACS profile groups, showed a wide spectrum of mortality risk.
This is an important study because it suggests that HMRS is superior to the INTERMACS profile in predicting outcomes. Prospective studies are needed to corroborate these important findings.
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