[ST segment analysis in 24-hour long-term ECG in patients with stable angina pectoris and angiographically detected...

ST-segment analysis on 24-hour Holter ECG was performed in 64 patients with angiographically proven coronary artery disease, a positive exercise test and chronic stable angina. During 125 days of recording, 494 episodes of transient ST-segment depression were observed, at an average of 4.0 +/- 3.7 episodes (1-13 episodes, median: 3 episodes) per day. The duration of ST depression per episode was 13.2 +/- 14.4 min (1-90 min; median: 8 min). No episodes of ST-elevation were observed. Only 27 (5.5%) ischemic episodes occurred during the night, between midnight and 6:00 a.m., but they were frequently observed during the morning hours between 7:00 and 12:00 a.m. Nearly all episodes of ischemia were preceded by an increase in heart rate. However, heart rate at the onset of significant ST-segment depression was significantly lower during Holter monitoring than during exercise test (p less than 0.001); this indicates that factors additional to the increase in myocardial demand might be relevant for transient myocardial ischemia during daily life. 382 of the 494 episodes (77.3%) of ischemia were asymptomatic; heart rate at the onset of ST-segment depression was similar in symptomatic and asymptomatic episodes; however, in asymptomatic episodes, maximal heart rate was significantly lower (p less than 0.001) and the duration of the episodes significantly longer (p less than 0.001). The percentage of asymptomatic episodes was very high in patients with one-vessel disease, whereas the duration and amount of ST-segment depression, as well as heart rate, at the onset of ischemia, were not dependent on the extent of coronary artery disease.