Pre-operative mortality risk assessment in patients with continuous-flow left ventricular assist devices: application of the HeartMate II risk score

Abstract

Background: Survival with left ventricular assist device (LVAD) therapy is dependent on appropriate patient selection. The HeartMate II risk score (HMRS) was recently derived and validated to predict 90-day mortality in clinical trial patients with continuous-flow LVADs. The aim of this study was to test HMRS validity in predicting survival at our institution.

Methods: We performed a retrospective analysis of patients implanted with HeartMate II (HMII; Thoratec, Pleasanton, CA) LVADs from March 31, 2004 to September 20, 2012 at the Columbia University Medical Center (CUMC). Patients were stratified according to HMRS profiles (HMRS Low < 1.58, 1.58 ≤ HMRS Medium ≤ 2.48, HMRS High > 2.48) calculated using age, albumin, creatinine, international normalized ratio (INR) and center volume. Outcome was defined as survival at 90 days after device implantation.

Results: HeartMate II LVADs were implanted in 205 patients. Pre-operative data from 201 patients were categorized into HMRS Low (n = 101; 1.04 [0.64 to 1.31]), HMRS Medium (n = 73; 1.98 [1.78 to 2.25]) and HMRS High (n = 27, 3.07 [2.70 to 3.43]) (p < 0.0001). Kaplan-Meier survival estimates at 90 days (HMRS Low 91.0 ± 2.9%, HMRS Medium 91.7 ± 3.2%, HMRS High 88.7 ± 6.1%) and at 1 year (HMRS Low 85.5 ± 3.8%, HMRS Medium 79.3 ± 5.5%, HMRS High 82.4 ± 8.4%) after LVAD implantation were not statistically different (p = 0.43). Prediction of 90-day mortality by receiver operating characteristic was poor (AUC = 0.56).

Conclusion: HMRS stratification poorly discriminates 90-day mortality after HMII LVAD implantation at our institution. Its generalizability as a universal prognostic score may be limited.

Keywords: continuous-flow left ventricular assist device; heart failure; mechanical circulatory support; mortality; prognosis; risk score.