In Japan, the use of percutaneous transluminal coronary angioplasty (PTCA) for the treatment of acute myocardial infarction (AMI) is extraordinarily frequent, resulting in large medical expenditure. Using chart-based data and exploiting regional variations, we explore what factors explain the frequent use of PTCA, employing propensity score matching to estimate the average treatment effects on hospital expenditure and hospital days. We find that the probability of receiving PTCA is affected by the density of medical resources in a region. Moreover, expenditure is higher for treated patients while there are no significant differences in hospitalization days, implying that the frequent use of PTCA is economically motivated.