Electrocardiographic changes during chest pain in unstable angina.

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Abstract
Twelve-lead ECG were recorded during one or more episodes of spontaneous chest pain in 41 patients with unstable angina. Selective coronary angiography 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, ECG abnormalities occured during chest pain in 24. In 5 patients, the ECG remained unchanged during pain. It was notable that 2 of the 12 patients without significant coronary artery disease also developed ECG abnormalities during chest pain. Of the 24 patients with coronary artery disease in whom ECG abnormalities were noted, ST segment elevation and ST segment depression occurred with equal frequency (11 patients each); 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 ECG changes occur in a high proportion of patients with coronary artery disease, the diagnostic value of the ECG recorded during chest pain is limited since false positives and false negatives are encountered in a substantial proportion of patients with the clinical features of unstable angina.