Silent myocardial ischemia in long-term ECG with various mani festations of coronary heart disease

Silent myocardial ischaemia seems to be of prognostic value in coronary artery disease. We examined 47 patients with coronary artery disease: 1. 20 patients with a history of myocardial infarction (MI), 2. 15 patients with chronic stable angina pectoris without a history of myocardial infarction (sAP), and 3. twelve patients with unstable angina with or without a history of myocardial infarction (uAP). Horizontal and downsloping ST-segment-depressions greater than or equal to 1 min and greater than or equal to 0.1 mV were defined as significant. There were 132 ST-segment-depressions, the relation between symptomatic and asymptomatic being 1:7.3, in MI 1:6.2, in sAP 1:5.3, in uAP 1:14. Heart rate increased before beginning of ST-segment-depression in 74% in MI, in 86% in sAP, but only in 38% in uAP. In sAP ST-segment-depressions were smaller (14% greater than 0.2 mV, none greater than 0.3 mV) than in patients with MI (42% greater than 0.2 mV, 12% greater than 0.3 mV) and uAP (25% greater than 0.2 mV, 9% greater than 0.3 mV). Mean duration of ST-segment-depression was 15.3 +/- 11.7 min in sAP (2 to 49 min), 28.5 +/- 35.6 min in MI (2 to 168 min), and 41.2 +/- 40 min in iAP (2 to 140 min). ST-segment-depressions in MI and sAP showed a circadian rhythm with a peak at midday and in the early evening and a small amount of ST-segment-depressions at night. In uAP ST-segment-depressions did not show that circadian variation. The number of ST-segment-depressions was higher in uAP than in MI and sAP.(ABSTRACT TRUNCATED AT 250 WORDS)