Comparative effectiveness of revascularization versus routine medical therapy for stable ischemic heart disease: a population based study

Background ─ Randomized studies have shown optimal medical therapy to be as efficacious as revascularization in stable ischemic heart disease (IHD). It is not known if these efficacy results are reflected by real-world effectiveness.

Objective – To evaluate the comparative effectiveness of routine medical therapy versus revascularization with percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG) in stable IHD.

Design – Observational cohort study.

Patients – Stable IHD patients from 1 October 2008 to 30 September 2011, identified using a registry of all angiography patients in Ontario, Canada.

Intervention – Revascularization, defined as PCI/CABG within 90 days after index angiography.

Main Measures – Death, myocardial infarction (MI) or repeat PCI/CABG. Revascularization was compared to medical therapy using a) multivariable Cox-proportional hazard models with therapy strategy treated as a time-varying covariate; and b) a propensity score matched analysis. Post-angiography medication use was determined.

Key Results – The authors identified 39,131 stable IHD patients, of whom 15,139 were treated medically, and 23,992 were revascularized (PCI = 15,604; CABG = 8,388). Mean follow-up was 2.5 years. Revascularization was associated with fewer deaths (HR 0.76; 95% CI 0.68–0.84; p < 0.001), MIs (HR 0.78; 95% CI 0.72–0.85; p < 0.001) and repeat PCI/CABG (HR 0.59; 95% CI 0.50–0.70; p < 0.001) than medical therapy. In the propensity-matched analysis of 12,362 well-matched pairs of revascularized and medical therapy patients, fewer deaths (8.6% vs 12.7%; HR 0.75; 95% CI 0.69–0.81; p < 0.001), MIs (11.7% vs 14.4%; HR 0.84; 95% CI 0.77–0.93 p < 0.001) and repeat PCI/CABG (17.4% vs 24.1%; HR 0.67; 95% 0.63–0.71; p < 0.001) occurred in revascularized patients, over the 4.1 years of follow-up. The revascularization patients had higher uptake of clopidogrel (70.3% vs 27.2%; p < 0.001), β-blockers (78.2% vs 76.7%; p = 0.010), and statins (94.7% vs 91.5%, p < 0.001) in the 1-year post-angiogram.

Conclusions – Stable IHD patients treated with revascularization had improved risk-adjusted outcomes in clinical practice, potentially due to under-treatment of medical therapy patients.