Effects of Exercise on the Signal-Averaged Electrocardiogram in Coronary Artery Disease Edward 6. Caref, MA, Nieca Goldberg, MD, Lawrence Mendelson, BA, Gerard Hanley, MD, Rachel Okereke, MS, Richard A. Stein, MD, and Nabil El-Sherif, MD

The effects of exercise on the signal-averaged electrocardiogram (SAECG) were investigated in 52 patients with stable coronary artery disease. The SAECG warn rewrded before and immediately after the exercise test and analyzed at 2S to 250 Hz and 40 to 250 Hz. All patients had SAECG with noise level 10.8 pV at 25 Hz and 50.6 pV at 40 Hz and with the ditkrenee in noise level between control SAECGs and SAECGs after exercise 10.2 to 0.3 pV. Twenty-eight patients developed ST changes consistent with transient subendocardial ischemia that persisted during the SAECG recording after exercise. There was no significant difference between control SAECGs and SAECGs after exercise in patients with or without a positive exercise test. The absence of significant change on the SAECG was not related to the presence or absence of prior myocardial infarction, site of infarction, development of exercise-induced ventricular arrhythmias or presence of an abnormal recording at baseline. These data suggest that exercise-induced electrophysiologic changes and ventricular arrhythmias may not be related to the anatomic-electrophysiologic substrate that underlies late potentials on the SAECG. (AmJCardid l-6654-58)

From the Department of Medicine, Cardiology Division, State University of New York Health Science Center and Veterans Administration Medical Center, Brooklyn, New York. This study was supported by grant HL 31341 from the National Institutes of Health, Bethesda, Maryland, and medical research funds from the Veterans Administration, Washington, DC. Manuscript received December 7, 1989; revised manuscript received February 21, 1990, and accepted February 22. Address for reprints: Edward B. Caref, MA, Cardiology, Box 1199, State University of New York Health Science Center, 450 Clarkson Avenue, Brooklyn, New York 11203.

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ate potentials on the signal-averaged electrocardiogram (SAECG) were found to correlate with spontaneous and induced ventricular tachycardia in patients with coronary artery disease and prior myocardial infarction.rh5 Late potentials seem to reflect a fixed anatomic-electrophysiologic substrate for reentrant tachyarrhythmias.6 Although late potentials develop early in the course of experimental acute myocardial infarction,’ their appearance during transient myocardial ischemia in humans is not well investigated. Because ventricular tachyarrhythmias could occur during the course of transient myocardial ischemia, such an investigation could provide some insight into the electrophysiologic mechanisms involved. In the present report we prospectively investigated the effect of exercise-induced transient ischemic ST changes on the SAECG in a stable group of patients with coronary artery disease.

L

METHODS Study group: We studied patients with documented

coronary artery disease who were referred to the exercise laboratory between June 1988 and July 1989 to evaluate clinically stable chest pain or discomfort caused by exertion and relieved by rest. Coronary artery disease was documented by evidence of prior myocardial infarction, based on clinical, electrocardiographic and serum creatine-MB enzyme changes, coronary angiography or a combination of these. Patients were included in the study if: (1) they were >3 weeks after myocardial infarction; (2) the 1Zlead electrocardiogram (ECG) showed no bundle branch block, nonspecific ST-T changes at rest, a QRS duration