Medical Student University of British Columbia Victoria, British Columbia, Canada
Background: Cardiac surgeons receive referrals for coronary artery bypass grafting (CABG) from their colleagues in interventional cardiology (Interventionalists), who first perform the diagnostic angiography that informs treatment selection. The referral process is often guided by a collaborative multidisciplinary Heart Team approach to ensure that patients receive the most appropriate revascularization strategy based on their individual clinical and anatomical characteristics. However, Interventionalists also perform an alternative revascularization method to CABG themselves, percutaneous coronary intervention (PCI). We quantified the variation in rates of referral for CABG by Interventionalists and explored which factors were most associated with this variation.
METHODS AND RESULTS: We accessed the British Columbia Medical Services Plan billing records from 2010 to 2024 using the provincial Ministry of Health Data Platform. We included the records of 21,363 CABG procedures, 298,311 diagnostic angiograms, and 105,195 PCI procedures. The records included 232,564 patients aged 20-79, 48 Cardiac Surgeons, and 62 Interventionalists.
For each year and interventionalist, we calculated the Referral Ratio—the number of referred CABG procedures performed over a time period divided by the number of diagnostic angiograms performed—as a measure of propensity to refer for CABG. We similarly derived the PCI Ratio to reflect propensity to perform PCI. We also computed the average number of angioplasties (balloon inflations with or without stents) billed per PCI case, and the average number of patients treated in the cath lab per day. We quantified each Interventionalist’s contribution to the total volume of referred CABGs and PCI angioplasties performed. These data are visualized in Figure 1.
The Referral Ratio varied from 1.68% to 14.8% across Interventionalists, averaged over the entire study period. The Referral Ratio was negatively correlated with Interventionalists’ use of PCI (R=-0.59, P<.001), the average number of angioplasties Interventionalists performed during PCI (R=-0.54, P<.001), and the average number of patients Interventionalists saw per day in the catheterization laboratory (R=-0.48, P=.003). As a result, the Interventionalists that performed the most angioplasties over the study period had disproportionately fewer referred patients undergo CABG over the same period.
Conclusion: Propensity to refer for CABG varies over 8-fold across Interventionalists. It is negatively correlated with the extensiveness of PCI performed, and procedural volume in the catheterization laboratory. The top three Interventionalists by PCI volume accounted for over 25% of all angioplasties performed, but less than 11% of total CABG referrals.
