Determinants of variations in coronary revascularization practices

Abstract

Background: The ratio of percutaneous coronary interventions to coronary artery bypass graft surgeries (PCI:CABG ratio) varies considerably across hospitals. We conducted a comprehensive study to identify clinical and nonclinical factors associated with variations in the ratio across 17 cardiac centres in the province of Ontario.

Methods: In this retrospective cohort study, we selected a population-based sample of 8972 patients who underwent an index cardiac catheterization between April 2006 and March 2007 at any of 17 hospitals that perform invasive cardiac procedures in the province. We classified the hospitals into four groups by PCI:CABG ratio (low [< 2.0], low-medium [2.0-2.7], medium-high [2.8-3.2] and high [> 3.2]). We explored the relative contribution of patient, physician and hospital factors to variations in the likelihood of patients receiving PCI or CABG surgery within 90 days after the index catheterization.

Results: The mean PCI:CABG ratio was 2.7 overall. We observed a threefold variation in the ratios across the four hospital ratio groups, from a mean of 1.6 in the lowest ratio group to a mean of 4.6 in the highest ratio group. Patients with single-vessel disease usually received PCI (88.4%-99.0%) and those with left main artery disease usually underwent CABG (80.8%-94.2%), regardless of the hospital's procedure ratio. Variation in the management of patients with non-emergent multivessel disease accounted for most of the variation in the ratios across hospitals. The mode of revascularization largely reflected the recommendation of the physician performing the diagnostic catheterization and was also influenced by the revascularization "culture" at the treating hospital.

Interpretation: The physician performing the diagnostic catheterization and the treating hospital were strong independent predictors of the mode of revascularization. Opportunities exist to improve transparency and consistency around the decision-making process for coronary revascularization, most notably among patients with non-emergent multivessel disease.

Figure 1:

Distribution of hospitals by ratio of PCI:CABG procedures performed within 90 days after index cardiac catheterization at that hospital. For analysis, hospitals were classified into four categories of ratios such that there were similar numbers of hospitals (four or five) in each category. The red line represents the mean PCI:CABG ratio (2.7). CABG = coronary artery bypass graft, PCI = percutaneous coronary intervention. The names of the hospitals appear in Box 1.

Figure 2:

Treatment initially recommended by the cardiologist performing the index catheterization and the treatment ultimately received within 90 days after the catheterization. The weighted kappa statistic was 0.81 (95% confidence interval 0.80–0.82) for agreement between the recommended treatment and the treatment received. Excludes 202 patients who died within 90 days after the index catheterization. CABG = coronary artery bypass graft, PCI = percutaneous coronary intervention.

Figure 3:

Ratio of percutaneous coronary intervention (PCI) to coronary artery bypass graft (CABG) surgery (top panel) and frequency of ad hoc PCIs (performed immediately after the index catheterization) among patients with multivessel disease (bottom panel), by category of hospital PCI:CABG ratio and type of cardiologist who performed the index catheterization. Excludes patients with emergent ST-segment elevation myocardial infarction and patients with cardiogenic shock.