Burden of medical co-morbidities and benefit from surgical revascularization in patients with ischaemic cardiomyopathy

Aims: The landmark STICH trial found that surgical revascularization compared to medical therapy alone improved survival in patients with heart failure (HF) of ischaemic aetiology and an ejection fraction (EF) ≤ 35%. However, the interaction between the burden of medical co‐morbidities and the benefit from surgical revascularization has not been previously described in patients with ischaemic cardiomyopathy. Methods and results: The STICH trial (ClinicalTrials.gov Identifier: NCT00023595) enrolled patients ≥ 18 years of age with coronary artery disease amenable to coronary artery bypass grafting (CABG) and an EF ≤ 35%. Eligible participants were randomly assigned 1:1 to receive medical therapy (MED) (n = 602) or MED/CABG (n = 610). A modified Charlson co‐morbidity index (CCI) based on the availability of data and study definitions was calculated by summing the weighted points for all co‐morbid conditions. Patients were divided into mild/moderate (CCI 1–4) and severe (CCI ≥ 5) co‐morbidity. Cox proportional hazards models were used to evaluate the association between CCI and outcomes and the interaction between severity of co‐morbidity and treatment effect. The study population included 349 patients (29%) with a mild/moderate CCI score and 863 patients (71%) with a severe CCI score. Patients with a severe CCI score had greater functional limitations based on 6‐min walk test and impairments in health‐related quality of life as assessed by the Kansas City Cardiomyopathy Questionnaire. A total of 161 patients (Kaplan–Meier rate = 50%) with a mild/moderate CCI score and 579 patients (Kaplan–Meier rate = 69%) with a severe CCI score died over a median follow‐up of 9.8 years. After adjusting for baseline confounders, patients with a severe CCI score were at higher risk for all‐cause mortality (hazard ratio 1.44, 95% confidence interval 1.19–1.74; P < 0.001). There was no interaction between CCI score and treatment effect on survival (P = 0.756). Conclusions: More than 70% of patients had a severe burden of medical co‐morbidities at baseline, which was independently associated with increased risk of death. There was not a differential benefit of surgical revascularization with respect to survival based on severity of co‐morbidity.