Abstract 15633: No Significant Difference in Yield of Obstructive Coronary Artery Disease Between an Initial Testing Strategy With Stress or Anatomical Imaging and Exercise Stress Testing in Ontario, Canada

Introduction: The optimal initial non-invasive diagnostic testing strategy for stable coronary artery disease (CAD) is unknown. While the American guidelines recommend an exercise stress test (GXT) as the first line test, the European guidelines suggest that stress imaging or coronary computed tomography angiography (CCTA) may be a preferable approach. Understanding the relationship between the initial strategy and downstream yield of obstructive CAD may provide insight as to the optimal strategy. Methods: We conducted a population-based retrospective cohort study of adults in Ontario (approximate population 10.1 million) using a combination of health administrative and clinical data. The first non-invasive test for each patient was identified between January 1 and December 31, 2012. Patients were followed for 6 months to determine receipt and results of invasive angiography. Patient characteristics were compared between the initial testing strategies and the relationship between the initial strategy and obstructive CAD on invasive angiography was examined. Results: Overall, 15,467 patients underwent invasive angiography after non-invasive testing during our study period. Of these, 54% with an initial CCTA had obstructive CAD on angiography, compared with 47% with an initial GXT and MPI and 45% with an initial stress echo (p=0.18). Patients with an initial MPI were more likely to have a high modified Framingham risk score (33% vs. 31% for GXT, 29% for stress echo and 27% for CCTA, p=0.03). After adjusting for co-variates, patients undergoing an initial MPI, CCTA or stress echo did not have significantly different odds of having obstructive CAD on angiography when compared to those with an initial GXT (see figure). Conclusions: An initial strategy with stress imaging or CCTA failed to result in a higher yield of obstructive CAD when compared to one with a GXT. These results do not support routine initial use of stress imaging or CCTA in the workup of stable angina.