Volume-outcome relationships for intra-aortic balloon pump in acute myocardial infarction

Abstract Background Acute myocardial infarction (MI) is one of the major scenarios of intra-aortic balloon pump (IABP) use, particularly when complicated by cardiogenic shock. The utilization of mechanical circulatory support devices including IABP varies widely per hospital, while whether a higher IABP volume at each hospital is translated into better outcomes in acute MI is unclear. Purpose To evaluate the relationship between the volume of IABP use and mortality at the hospital level in patients with acute MI undergoing percutaneous coronary intervention (PCI). Methods Using a Japanese nationwide administrative database, a total of 26,490 patients with acute MI undergoing primary PCI from 154 hospitals were included. The primary endpoint was the observed/predicted in-hospital mortality ratio. The predicted mortality per patient was calculated using baseline variables and was averaged for each hospital. The associations among PCI volume for acute MI, observed and predicted in-hospital mortality, and observed and predicted IABP use were assessed at the hospital level. Results Of the 26,490 patients, 2,959 (11.2%) were treated with IABP and 1,283 (4.8%) died during hospitalization. The annualized number of IABP use per hospital in acute MI was 4.5 [2.4-10.7]. In lower primary PCI volume centers, IABP was more likely to be underused than expected, and the observed/predicted in-hospital mortality ratio was higher than in higher volume centers (Figure). The observed/predicted mortality ratio seemed lowest in hospitals where the observed/predicted IABP use ratio was around one. Conclusions The present study showed that the lower annual number of IABP use was associated with an increased mortality risk at the hospital level, and suggested that standardized IABP use can be an institutional quality indicator in a setting of acute MI.