Silent myocardial ischaemia in patients with angiographically proven coronary artery disease.

Twenty patients with angiographically proven coronary artery disease (CAD) were evaluated by Holter monitoring for assessment of total ischaemic burden during daily activities. Thirteen patients revealed ischaemia on Holter monitoring (symptomatic-2, silent-4 and both types-7). As compared to symptomatic ischaemia, the silent myocardial ischaemic episodes were more frequent (25 vs 10 episodes), longer in duration (15-53 minutes vs 8-45 minutes), occurred at lower heart rates (65-75/minute (mean 68) vs 70-90 per minute (mean 76) and silent ischaemic episodes exceeded symptomatic ones in both morning (10 vs 4) and evening (15 vs 6) peaks. Occurrence of symptomatic as well as silent ischaemia had no relation to rest, activity, left ventricular functions, and there was no difference in the extent (1-3mm) and type (horizontal or downsloping) of ST-segment depression. We conclude that in patients with significant coronary artery disease, silent myocardial ischaemia is more frequent than the symptomatic ischaemia during daily activities. It occurs at lower heart rates, lasts longer, and bears no relation to rest, activity or left ventricular function. Evening peaks may be as frequent or more than the morning peaks. Holter monitoring thus is helpful for assessment of total ischaemic burden in CAD patients.