Volume-Outcome Relations of Percutaneous Coronary Intervention in Patients Presenting With Acute Myocardial Infarction (from the J-PCI Registry)

A lower institutional primary percutaneous coronary intervention (PCI) volume is associated with a higher risk of postprocedural poor outcomes, particularly in urgent or emergent settings (e.g., PCI for acute myocardial infarction [MI]). However, the individual prognostic impact of PCI volume stratified by indication and the relative ratio remains unclear. Using the Japanese nationwide PCI database, we investigated 450,607 patients from 937 institutions who underwent either primary PCI for acute MI or elective PCI. The primary end point was the observed/predicted in-hospital mortality ratio. The predicted mortality per patient was calculated using the baseline variables and averaged for each institution. The relation between the annual primary, elective, and total PCI volumes and institutional in-hospital mortality after acute MI was evaluated. The association between the primary-to-total PCI volume per hospital and mortality was also investigated. Of the 450,607 patients, 117,430 (26.1%) underwent primary PCI for acute MI, of whom 7,047 (6.0%) died during hospitalization. The median total PCI volume and primary-to-total PCI volume ratio were 198 (interquartile range 115 to 311) and 0.27 (0.20 to 0.36). Overall, the observed in-hospital mortality and observed/predicted mortality ratio in patients with acute MI were higher in institutions with lower primary, elective, and total PCI volumes. The observed/predicted mortality ratio was also higher in institutions with lower primary-to-total PCI volume ratios, even in high-PCI volume hospitals. In conclusion, in this nationwide registry-based analysis, lower institutional PCI volumes, regardless of setting, were associated with higher in-hospital mortality after acute MI. The primary-to-total PCI volume ratio provided independent prognostic information.