Volume-Outcome Relationships for Percutaneous Coronary Intervention in Acute Myocardial Infarction

Background Lower primary percutaneous coronary intervention (PCI) volume is known to be associated with worse outcomes in patients with acute myocardial infarction (MI) at hospital level. The present study aimed to evaluate the relations of primary, elective, and total PCI volume and primary/total PCI volume ratio per hospital to in-hospital mortality in patients with acute MI undergoing primary PCI. Methods and Results Using a large nationwide administrative database, we included a total of 83 076 patients from 154 hospitals in Japan undergoing PCI for either acute MI or elective cases. Relations of annual procedural volumes for primary, elective, and total PCI to in-hospital mortality after acute MI at hospital level were evaluated. The ratio of primary to total PCI volume per hospital was also assessed. The primary end point was the ratio of observed to predicted mortality. Of 83 076 patients, 26 913 (32.4%) underwent primary PCI for acute MI, among whom 1561 (5.8%) died during hospitalization. Overall, observed in-hospital mortality after acute MI and observed/predicted mortality ratio were higher in hospitals with lower primary, elective, and total PCI volumes. Observed/predicted in-hospital mortality ratio was higher in hospitals with low primary/total PCI volume ratio, even in those with high total PCI volume. Conclusions Primary, elective, and total PCI volume at hospitals were inversely associated with in-hospital mortality in patients with acute MI undergoing primary PCI. Lower ratio of primary to total PCI volume were related to higher in-hospital mortality, suggesting primary/total PCI volume ratio as an institutional indicator of quality of care for acute MI.