['Patients with acute myocardial infarction (AMI) whose culprit lesion lies in a branch of the 3 major coronary arteries have well-preserved cardiac function. A first MI with preserved cardiac function is a risk factor for left ventricular free wall rupture (LVFWR), so the aim of this study was to investigate the possible relationship between AMI with branch segment occlusion and LVFWR.', 'The 439 patients with AMI were retrospectively studied. They were divided into 2 groups: group B (n=70; segments 4 atrioventricular node artery, 4 posterior descending coronary artery, 8, 9, 10, 12, 14, or 15 according to the AHA classification), and group P (n=369; segments 1, 2, 3, 5, 6, 7, 11, or 13). Primary percutaneous coronary intervention (PCI) was more often performed in group P (75% vs 57%; P=0.0018). In-hospital mortality tended to be lower in group B (1.4% vs 6.2%; P=0.105). The incidence of LVFWR was significantly higher in group B (10.0% vs 1.6%; P=0.0002).By multivariate logistic regression analysis, 1-vessel disease, absence of primary PCI, branch segment occlusion, and age were identified as independent predictors of LVFWR.'] Is branch segment occlusion with acute myocardial infarction a risk for left ventricular free wall rupture?