STS Intermacs 90-Day Mortality Risk Model for Durable Left Ventricular Assist Device Implant: Validation in an Expanded Contemporary Cohort.

BACKGROUND: Mortality risk models for durable LVAD implantation inform candidate selection, provider performance and quality improvement. We sought to validate the STS Intermacs mortality risk model in an expanded contemporary patient cohort. METHODS: STS Intermacs was queried for patients undergoing primary LVAD implantation between January 1, 2019, and March 31, 2025. Beyond the original derivation and validation cohorts (N=11,342), 4,344 additional eligible patients implanted between October 1, 2023, and March 31, 2025 were identified, yielding an expanded study population of 15,686 implants. Model performance was evaluated using measures of discrimination and calibration. RESULTS: Compared with the original cohort, patients in the new validation cohort were less likely to be White (54.4 vs. 58.6%, P<0.0001), have prior CABG (11.0 vs. 13.9%, P<.0001), more likely to have diabetes (16.4 vs. 12.6%, P<.0001), require concomitant surgery (58.1 vs. 51.8%, P<.0001), and have lower levels of SGOT/AST (36.7 vs. 41.0 IU/L, P=0.003), BUN (27.5 vs. 28.1 mg/dL, P=0.02) and bilirubin (1.1 vs. 1.2 mg/dL, P<.0001). Ninety-day mortality was similar between cohorts (P=0.99). After model refitting to account for significant baseline differences, logistic regression applied to the original full cohort (derivation) and new contemporary validation cohort produced similar discrimination (AUC, 0.6963 vs 0.6928) and calibration (Brier score, 0.074 vs 0.075). CONCLUSIONS: The STS Intermacs 90-day mortality risk model maintains acceptable performance when applied to an expanded cohort. The stability of discrimination and calibration in >15,000 patients support its utility as a robust tool for candidate selection, benchmarking, and quality assessment in a high-risk patient population.