In patients after acute myocardial infarction, signal-averaged electrocardiography is used as the one of the non-invasive methods for the prediction for ventricular arrhythmia, one of the causes ofn death in acute myocardial infarction. Signal-averaged electrocardiography has allowed the identification of low-amplitude, high-frequency signals(late potentials)in the terminal portion of the QRS complex. They are thougt to be occured in the portion of electrophysiologically unstable myocardium. The presence of late potentials identifies regions of delayed conducton in the elctrophysiologically unstable border zone of an acute infarction.

These electrophysiologic change of myocardium is influenced by the patency of infarct-related artery. A patent artery is associated with electrical stability of myocardium, decreased in cidence of late potentials and improved survival.

58 patients of acute myocardial infarction underwent signal-averaged electrocardiography, coronary angiography within 10 days after AMI, 20 of healthy persons underwent signal-averaged electrocardiography.

In patent group, late potentials were recorded in 7 of 38 patients(18%) as compared with 13 of 20 patients(65%) of non-patent group. The statistically significant parameters of signal-averaged electrocardiography beteen patent and non-patent group were filtered total QRS duration(TQRS, 106.7±20.9msec), high frequency low amplitude signal (HLAS, 30.8±7.5 vs 41.3±16.5 msec)with HLAS being the most powerful varialble in the model.

These results suggest that the patency of infarct-related artery is associated with electrophysiologic stability of myocardium and signal-averaged electrocardiography is one of the useful non-invasive method in risk stratification of acute myocrdial infarction.