Detection of apoptosis in ischemic heart. Usefulness in the diagnosis of early myocardial injury.

Myocardial samples of hearts with histologic findings of acute myocardial infarction (group A), sudden coronary deaths without histologic changes (group B), and chronic ischemic heart disease (group C) were analyzed to investigate the appearance of apoptosis in acute and chronic ischemic cardiac disorders. This analysis involved the morphologic detection of DNA strand breaks in myocyte nuclei by the terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay and the biochemical determination of DNA laddering in the myocardium using archival formalin-fixed, paraffin-embedded tissue sections of human myocardium. The authors demonstrated that apoptosis of myocardial cells could occur after ischemic myocardial cell injury. In all documented cases of acute myocardial infarction (group A), the infarcted area included extensive presence of both apoptosis and necrosis. In the tissue bordering on and away from the obviously infarcted areas, positive nuclei were intermingled with nonstained normal myocytes. The number of positive nuclei decreased with the distance from the infarction foci. In group B, myocardial samples showed focal or diffuse nuclear positivity of varying degrees for apoptosis, confirming the presence of myocardial ischemic cell death, whereas the histologic diagnosis remained inconclusive. This finding suggests that apoptosis could be used as a marker for acute ischemic injury. In group C, stained nuclei were dispersed with intermingled normal cardiomyocytes.