Relation between Exercise-Induced QRS Prolongation and Reversible Myocardial Perfusion Defects in Patients with Coronary Artery Disease

Acute myocardial ischemia decreases conduction velocity through the ischemic myocardium and may produce QRS prolongation on the surface electrocardiogram. To investigate the effect of exercise-induced myocardial ischemia on the QRS duration, 124 patients who underwent diagnostic cardiac catheterization and exercise thallium-201 scintigraphy were studied. Seventeen patients had normal coronary arteries and 107 had coronary artery disease. QRS duration decreased with exercise in patients with normal coronary arteries (-3.7 ms, confidence interval -7.7 to 0.3) but increased in patients with coronary artery disease; exercise-induced QRS prolongation was directly related to the number of vessel disease (1.2 ms in patients with one-vessel disease; 8.7 ms in patients with two-vessel disease, and 10.5 ms in patients with threevessel disease, p < 0.001). Likewise, exercise-induced QRS duration decreased in patients without exercise-induced reversible perfusion defects (-1.3 ms, confidence limits -2.8 to 0.2) but increased in patients with exercise-induced perfusion defects (9.7 ms in patients with one perfusion defect; 13.6 ms in patients with two perfusion defects, and 16.3 ms in patients with three perfusion defects, p < 0.001). Exercise-induced QRS prolongation was best related to the number of exercise-induced perfusion defects than to the number of vessel disease, p < 0.001. In conclusion, exercise-induced QRS prolongation in patients with coronary artery disease was directly related to the number of vessel disease and to exercise-induced perfusion defects. This QRS prolongation was better related to the number of reversible perfusion defects than to the number of vessel disease. Thus, exercise-induced QRS prolongation in patients with coronary artery disease may be a marker of exercise-induced myocardial ischemia.