Determinants of variations in initial treatment strategies for stable ischemic heart disease

• Published in: Canadian Medical Association journal (CMAJ) 2015-07, Vol.187 (10), p.E317-E325
• Main Authors: Bennell, Maria C, Qiu, Feng, Kingsbury, Kori J, Austin, Peter C, Wijeysundera, Harindra C
• Format: Article
• Language: English
• Subjects: Age Factors; Aged; Angina, Stable - diagnostic imaging; Angina, Stable - epidemiology; Angina, Stable - therapy; Cardiovascular Agents - therapeutic use; Cardiovascular disease; Care and treatment; Clinical outcomes; Cohort Studies; Comorbidity; Coronary Angiography; Coronary Artery Bypass - statistics & numerical data; Databases, Factual; Diabetes Mellitus - epidemiology; Distribution; Exercise Test; Female; Forecasts and trends; Hospitals - statistics & numerical data; Humans; Hyperlipidemias - epidemiology; Hypertension - epidemiology; Income - statistics & numerical data; Logistic Models; Male; Medical statistics; Medical treatment; Middle Aged; Myocardial ischemia; Myocardial Ischemia - diagnostic imaging; Myocardial Ischemia - epidemiology; Myocardial Ischemia - therapy; Myocardial Revascularization - statistics & numerical data; Ontario; Patients; Percutaneous Coronary Intervention - statistics & numerical data; Peripheral Vascular Diseases - epidemiology; Practice Patterns, Physicians' - statistics & numerical data; Proportional Hazards Models; Pulmonary Disease, Chronic Obstructive - epidemiology; Severity of Illness Index; Smoking - epidemiology; Studies; Vascular surgery
• ISSN: 0820-3946; 1488-2329
• DOI: 10.1503/cmaj.141372

The ratio of revascularization to medical therapy (referred to herein as the revascularization ratio) for the initial treatment of stable ischemic heart disease varies considerably across hospitals. We conducted a comprehensive study to identify patient, physician and hospital factors associated with variations in the revascularization ratio across 18 cardiac centres in the province of Ontario. We also explored whether clinical outcomes differed between hospitals with high, medium and low ratios. We identified all patients in Ontario who had stable ischemic heart disease documented by index angiography performed between Oct. 1, 2008, and Sept. 30, 2011, at any of the 18 cardiac centres in the province. We classified patients by initial treatment strategy (medical therapy or revascularization). Hospitals were classified into equal tertiles based on their revascularization ratio. The primary outcome was all-cause mortality. Patient follow-up was until Dec. 31, 2012. Hierarchical logistic regression models identified predictors of revascularization. Multivariable Cox proportional hazards models, with a time-varying covariate for actual treatment received, were used to evaluate the impact of the revascularization ratio on clinical outcomes. Variation in revascularization ratios was twofold across the hospitals. Patient factors accounted for 67.4% of the variation in revascularization ratios. Physician and hospital factors were not significantly associated with the variation. Significant patient-level predictors of revascularization were history of smoking, multivessel disease, high-risk findings on noninvasive stress testing and more severe symptoms of angina (v. no symptoms). Treatment at hospitals with a high revascularization ratio was associated with increased mortality compared with treatment at hospitals with a low ratio (hazard ratio 1.12, 95% confidence interval 1.03-1.21). Most of the variation in revascularization ratios across hospitals was warranted, in that it was driven by patient factors. Nonetheless, the variation was associated with potentially important differences in mortality.