Transient myocardial ischaemia during ambulatory monitoring out of hospital in patients with chronic stable angina pectoris.

Transient myocardial ischaemia during daily life, detected by ambulatory electrocardiographic monitoring, was investigated in 42 patients with chronic stable angina and documented coronary artery disease. Ambulatory monitoring was initiated for 36 hours after all prophylactic antianginal medication had been withdrawn for 5 days. There were 196 episodes of ST-segment depression, 145 (74%) of which were not accompanied by angina. As well, a tendency to more prolonged and greater ST-segment change with symptomatic ischaemic episodes was noted. A diurnal variation in transient ischaemia both with and without symptoms was observed, the highest frequency being in the morning hours. Transient myocardial ischaemia was more frequent in patients with double or triple vessel disease, compared with single vessel disease, but with a great variation. Heart rate at the onset of ischaemia during ambulatory monitoring was significantly lower than heart rate at the onset of ST-segment change during exercise testing (100.2 +/- 14.6 vs. 115.8 +/- 19.6 beats/min, p less than 0.01), which may indicate different pathophysiological mechanisms. Transient impairment in coronary oxygen supply seems to be of importance during ischaemic episodes out of hospital.