Heart rate, magnitude and duration of ST-segment depression in symptomatic and asymptomatic episodes of myocardial ischemia in patients with coronary artery disease recorded by Holter.

In the group of 85 patients with coronary artery disease the exercise and 24-hour ambulatory electrocardiograms were recorded in order to analyse the frequency of asymptomatic episodes of myocardial ischemia and to determine differences between symptomatic and asymptomatic episodes of myocardial ischemia. All patients had ischemic ST-segment depression (greater than or equal to 1 mm) on the exercise electrocardiogram. During exercise testing, 23 (27%) patients had ST-segment depression without anginal pain or dyspnea. On the 24-hour ambulatory electrocardiogram transient episodes of myocardial ischemia were found in 50 (58.8%) patients. In 16 patients all episodes were asymptomatic, in 9 all episodes were symptomatic, and in 25 patients some episodes were symptomatic and some asymptomatic. During a 24-hour electrocardiogram in 25 patients with both types of ischemia, 175 transient episodes of myocardial ischemia were recorded. Most of them (125, i.e. 71.4%) were asymptomatic. The heart rate in symptomatic and asymptomatic episodes was similar. The magnitude of ST-segment depression in symptomatic episodes was higher than in asymptomatic episodes (P less than 0.01). There was not significant difference in the duration of the two types of myocardial ischemia. This study suggests: 1. During daily activities, in patients with the positive exercise test, asymptomatic episodes of myocardial ischemia are more frequent than symptomatic episodes. 2. The magnitude of ST-segment depression is the main factor in the determination of the presence of anginal pain.