We assessed the clinical features of patients with myocardial rupture within 48 to 72 hours, defined as early myocardial rupture, after percutaneous coronary intervention (PCI) for ST-segment elevation acute myocardial infarction (STEMI). Six patients (4 men, 66 ± 13 years) with early myocardial rupture were identified from 1252 consecutive patients undergoing PCI for STEMI. We evaluated the degree of microvascular reperfusion using thrombolysis in myocardial infarction (TIMI) myocardial perfusion (TMP) grade and a resolution of sum of ST-segment elevation in a 12-lead electrocardiogram (ECG). Time from PCI to myocardial rupture was 11 ± 7 hours. All patients showed TMP grade 0 or 1 and an increase in sum of ST-segment elevation after PCI (1.9 ± 0.5 vs 2.5 ± 0.7 mV; P = .032), suggesting severely failed reperfusion at the level of microcirculation as the common feature to develop early myocardial rupture after PCI for STEMI.