Frailty, age, and treatment effect of surgical coronary revascularization in ischemic cardiomyopathy: a post hoc analysis of the STICHES trial

Frailty is common among older patients with heart failure (HF). The efficacy of coronary artery bypass grafting (CABG) on the risk of mortality among frail patients with ischemic cardiomyopathy and HF is uncertain, and whether frailty burden modifies the treatment benefits of CABG among these patients is unknown. We performed a post hoc analysis of the STICHES trial, a randomized trial of CABG with medical therapy vs medical therapy alone among participants with ischemic cardiomyopathy with ejection fraction ≤ 35%. Baseline frailty was assessed through a Rockwood Frailty Index (FI), and based on FI cut-offs from prior HF studies, participants with FI ≥ 0.311 were classified as more frail, and those with FI < 0.311 were classified as less frail. A multivariable Cox proportional hazard model with multiplicative interaction terms was constructed to evaluate whether frailty status modified the treatment effect of CABG on mortality in the overall trial cohort and among those < 60 vs ≥ 60 years of age. Of 1187 participants (12.4% female, 2.6% Black, median FI = 0.33 [IQR 0.27-0.39]), 678 were characterized as more frail. Frailty burden did not modify the efficacy of CABG on the risk of all-cause death in the overall cohort (P_int CABG × frailty = 0.2). In age stratified analysis, Baseline frailty status did not modify the treatment effect of CABG on the risk of all-cause mortality among younger (< 60 years, P_int CABG × frailty = 0.2) as well as older participants (≥60 years, P_int CABG × frailty = 0.6). In this post hoc analysis of the STICHES trial, baseline frailty status did not modify the efficacy of CABG in the overall cohort as well as among younger or older participants. Frailty alone should not be used as a criterion to determine the utilization of CABG among patients with ischemic cardiomyopathy.