Apoptosis in recent myocardial infarction

Purpose: Apoptosis is considered a common pathological feature in acute myocardial infarction (MI) and heart failure; however its role in the later phases post MI has not been characterised. The goal of our study was to investigate by pathological examination human hearts at 20 to 30 days post MI and identify signs of ongoing cell apoptosis. Materials and Methods: Two hearts were collected at autopsy from patients who died 20 to 30 days from the onset of MI (Cases 1 and 2). Gross anatomy and light microscopy examination of the hearts was performed to define the infarcted area and the infarct-related artery. The in situ end-labeling of DNA fragmentation (TUNEL) was performed to identify apoptotic cells and the apoptotic rate (AR) was calculated. Results: There were no signs of acute necrosis in any of the specimens examined. A high number of myocardiocyte were positive at TUNEL examination in specimens obtained at sites of infarction, mean AR=44%, but not in specimens derived from the same patients at regions remote from the MI, AR=0. Conclusions: High grade apoptosis is present at sites of infarction and not in regions remote from the infarcted area in the later phases post MI. These data support persistent myocardiocyte loss and identify a possible explanation of progressive left ventricular dysfunction in the subacute phases of MI.