Effect of Physician Volume on the Relationship Between Hospital Volume and Mortality During Primary Angioplasty

Abstract

We sought to examine the combined effect of hospital and physician volume of primary percutaneous coronary intervention (PCI) on in-hospital mortality. An inverse relationship between volume and outcome has been observed for both hospitals and physicians after primary PCI for acute myocardial infarction. Using the New York State PCI registry, we examined yearly hospital volume, physician volume, and risk-adjusted mortality in 7,321 patients undergoing primary PCI for acute myocardial infarction. Risk-adjusted mortality rates for high-volume hospitals (>50 cases/year) and high-volume physicians (>10 cases/year) were compared with their respective low-volume counterparts. Primary PCI by high-volume hospitals (odds ratio [OR]: 0.58; 95% confidence interval [CI]: 0.38 to 0.88) and high-volume physicians (OR: 0.66; 95% CI: 0.48 to 0.92) was associated with lower odds of mortality. Furthermore, there was a significant interaction between hospital and physician volume on adjusted mortality (p = 0.02). Although unadjusted mortality was lower when primary PCI was performed by high-volume physicians in high-volume hospitals compared with low-volume physicians in low-volume hospitals (3.2% vs. 6.7%, p = 0.03), the risk-adjusted mortality rate was not statistically significant (3.8% vs. 8.4%, p = 0.09). In low-volume hospitals, the average risk-adjusted mortality rate for low-volume physicians was 8.4% versus 4.8% for high-volume physicians (OR: 1.44; 95% CI: 0.68 to 3.03). However, in high-volume hospitals, the risk-adjusted mortality rate for high-volume physicians was 3.8% versus 6.5% for low-volume physicians (OR: 0.58; 95% CI: 0.39 to 0.86). During primary PCI, physician experience significantly modifies the hospital volume-outcome relationship. Therefore, policymakers need to consider physician experience when developing strategies to improve access to primary PCI.