EXERCISE-INDUCED QRS PROLONGATION IN PATIENTS WITH CORONARY-ARTERY DISEASE - A MARKER OF MYOCARDIAL-ISCHEMIA

The objective of this study was to investigate the effect of myocardial ischemia on the QRS duration in patients with coronary artery disease since acute myocardial ischemia decreases conduction velocity through the ischemic myocardium and may produce QRS prolongation on the surface electrocardiogram. One hundred fifty patients who underwent cardiac catheterization and exercise radionuclide ventriculography within 1 month of each other were studied. Forty patients had normal coronary arteries and 110 had coronary artery disease. QRS duration decreased with exercise in patients with normal coronary arteries (-3.0 msec, confidence limits -6.2 to 0.2), but increased in patients with coronary artery disease; exercise-induced QRS prolongation was directly related to the number of diseased vessels (4.8 msec in patients with one, 7.8 msec in patients with two, and 13.3 msec in patients with three-vessel disease, p < 0.001). Likewise, QRS duration decreased with exercise in patients without exercise-induced segmental contraction abnormalities (-1.8 msec, confidence limits -3.7 to 0.1), but increased in patients with segmental contraction abnormalities (6.7 msec in patients with one, 13.5 msec in patients with two, and 21 msec in patients with three segmental contraction abnormalities, p < 0.0001). Exercise-induced QRS prolongation was better related to the number of segmental contraction abnormalities than to the number of diseased vessels (p < 0.01). It was concluded that exercise produces QRS prolongation in patients with coronary artery disease in direct relation to the number of diseased vessels and to exercise-induced segmental contraction abnormalities. This QRS prolongation was more closely related to the number of exercise-induced segmental contraction abnormalities than to the number of diseased vessels. Thus exercise-induced QRS prolongation in patients with coronary artery disease may be a marker of exercise-induced myocardial ischemia.