During primary percutaneous coronary intervention (PCI), physician experience significantly modifies the hospital volume-outcome relationship, according to a registry published in the Feb. 17 issue of the Journal of the American College of Cardiology.
V.S. Srinivas, MBBS, department of medicine, division of cardiology at Montefiore Medical Center in Bronx, N.Y., and colleagues sought to examine the combined effect of hospital and physician volume of primary PCI on in-hospital mortality. Using the N.Y. State PCI registry, the researchers examined yearly hospital volume, physician volume and risk-adjusted mortality in 7,321 patients undergoing primary PCI for acute MI. Risk-adjusted mortality rates for high-volume hospitals ( >50cases/year) and high-volume physicians ( >10 cases/year) were compared with their respective low-volume counterparts.
The authors found that primary PCI by high-volume hospitals and high-volume physicians was associated with lower odds of mortality. Furthermore, there was a significant interaction between hospital and physician volume on adjusted mortality.
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 percent), the risk-adjusted mortality rate was not statistically significant (3.8 vs. 8.4 percent), according to the researchers.
In low-volume hospitals, Srinivas and colleagues found that the average risk-adjusted mortality rate for low-volume physicians was 8.4 percent versus 4.8 percent for high-volume physicians. However, in high-volume hospitals, the risk-adjusted mortality rate for high-volume physicians was 3.8 percent, compared with 6.5 percent for low-volume physicians.
According to the researchers, physician volume was "a powerful effect modifier of hospital volume on outcome." They said that these outcomes could be explained as a disproportionate case mix of high-risk patients; care-related differences in low-volume hospitals; or operator inexperience. The investigators performed risk adjustment to account for differences in case mix and stratified analyses to equalize the effect of care-related differences. "Despite these measures, low physician volume was an independent predictor, leaving physician inexperience as the most plausible explanation for this effect," Srinivas and colleagues said.
Based on their findings, “policymakers need to consider physician experience when developing strategies to improve access to primary PCI,” the authors stated.