Effects of hospital volume of primary percutaneous coronary interventions on angiographic results and in-hospital outcomes for acute myocardial infarction

Background Several clinical studies have demonstrated an inverse relationship between hospital volume of primary percutaneous coronary interventions (PCI) and in-hospital mortality. However, the relationships among hospital primary PCI volume, angiographic results, and in-hospital prognosis in patients with acute myocardial infarction (AMI) have not been fully investigated in Japan. Methods and Results Using the AMI-Kyoto Multi-Center Risk Study database between January 2000 and December 2005, hospitals were classified into quintiles based on their annual volume of primary PCI. The fifth quintile of hospitals was labeled as high-volume, and the other quintiles were combined and defined as low-volume. Although patients undergoing primary PCI in high-volume hospitals (high-volume group, n=764) had a larger number of diseased vessels at initial coronary angiography and lower Thrombolysis In Myocardial Infarction (TIMI) flow grade in the infarct-related artery before PCI, compared with those in low-volume hospitals (low-volume group, n=1,021), the rates of achieving TIMI flow grade 3 just after PCI in the high-volume group was significantly higher than that in the low-volume group. The overall in-hospital mortality did not differ between the 2 groups. On multivariate analysis, in AMI patients undergoing primary PCI, Killip class ≥3 at admission, multivessel disease or left main trunk (LMT) as culprit lesion, number of diseased vessels ≥2 or diseased LMT, and age were the independent positive predictors of in-hospital mortality, whereas the TIMI flow grade 3 after primary PCI and elapsed time