Background:
Wide variation exists in the diagnostic yield of coronary angiography in stable ischemic heart disease (IHD). Previous work has primarily focused on patient factors for this variation. We sought to understand if system and physician factors, specifically hospital and physician type, as well as physician self-referral, have incremental impacts on the yield of coronary angiography, above and beyond that of patient factors alone.
Methods:
All patients who underwent a diagnostic coronary angiogram for possible stable IHD, at the 18 cardiac centers in Ontario, Canada were identified from October 1st, 2008 to September 30th, 2011. Obstructive coronary artery disease was defined as stenosis greater than 70% in the main coronary arteries or greater than 50% in the left main artery. Physicians were classified as either invasive or interventional. Hospitals were categorized into cath only, stand-alone PCI and full service centers. Multi-variable hierarchical logistic models were developed to identify system and physician level predictors of obstructive coronary artery disease, having adjusted for patient factors.
Results:
Our cohort consisted of 60,986 patients who underwent a diagnostic angiogram for possible stable IHD, of which 33,483 had obstructive coronary artery disease (54.9%), ranging from 41.0% to 70.2% across centers. Self-referral rates varied from 4.8% to 74.6%. Fewer self-referral patients (52.5%) had obstructive coronary artery disease compared to non-self-referral patients (56.5%), with an odds ratio (OR) of 0.89 (95% CI 0.85-0.93;p <0.001), after accounting for patient factors. Angiograms performed by interventional physicians had a higher likelihood of showing obstructive coronary artery disease (60.1% vs. 50.8%; OR 1.22; 95% CI 1.17-1.28; p<0.001). Fewer angiograms at cath only centers showed obstructive disease (45.0%) compared to full service centers (58.1%); this was of borderline significance (OR 0.59; 95% CI 0.34-1.00; p=0.05).
Conclusion:
Physician and system factors are important predictors of the diagnostic yield of coronary angiography in stable IHD, even after accounting for patient characteristics. Further study into the drivers of how these physician and system factors impact diagnostic yield is an important focus for quality improvement.
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