Prevalence and Extent of Obstructive Coronary Artery Disease Among Patients Undergoing Elective Coronary Catheterization in New York State and Ontario

IMPORTANCE Prior studies have shown that physicians in New York State (New York) perform twice as many cardiac catheterizations per capita as those in Ontario for stable patients. However, the role of patient selection in these findings and their implications for detection of obstructive coronary artery disease (CAD) are largely unknown. OBJECTIVE To evaluate the extent of obstructive CAD and to compare the probability of detecting obstructive CAD for patients undergoing cardiac catheterization. DESIGN, SETTING, AND PATIENTS An observational study was conducted involving patients without a history of cardiac disease who underwent elective cardiac catheterization between October 1, 2008, and September 30, 2011. Obstructive CAD was defined as diameter stenosis of 50% or more in the left main coronary artery or stenosis of 70% or more in a major epicardial vessel. MAIN OUTCOMES AND MEASURES Observed rates and predicted probabilities of obstructive CAD. Predicted probabilities were estimated using logistic regression models. RESULTS A total of 18 114 patients from New York and 54 933 from Ontario were included. The observed rate of obstructive CAD was significantly lower in New York at 30.4% (95% CI, 29.7%-31.0%) than in Ontario at 44.8% (95% CI, 44.4%-45.3%; P