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Electrocardiographic changes during chest pain in unstable angina.

Twelve-lead electrocardiograms were recorded during one or more episodes of spontaneous chest pain in 41 patients with unstable angina. Selective coronary angtography and left ventriculography were subsequently carried out in 40 patients. In the remaining patient, the coronary arteries were examined at necropsy. Among the 29 patients with significant coronary artery disease, electrocardiographic abnormalities occurred during chest pain in 24 (83%). In 5 patients, the electrocardiogram remained unchanged during pain. It was notable that 2 of the 12 patients without significant coronary artery disease also developed electrocardiographic abnormalities during chest pain. Of the 24 patients with coronary artery disease in whom electrocardiographic abnormalities were noted, ST segment elevation and ST segment depression occurred with equal frequency (11 patients each), whereas isolated T wave abnormality was noted less frequently (2 patients). No significant differences were observed in the severity or the extent of coronary artery disease in these 3 groups of patients, though ST segment elevation appeared to be more common in patients with old myocardial infarction. Though electrocardiographic changes occur in a high proportion of patients with coronary artery disease, the diagnostic value of the electrocardiogram recorded during chestpain is limited since false positives and false negatives are encountered in a substantial proportion of patients with the clinical features of unstable angina.