To determine the prevalence of decreases in left ventricular (LV) ejection fraction (EF) at rest in patients with coronary artery disease (CAD), including those with stable angina (n = 21), unstable angina (n = 13), and recent myocardial infarction (n = 11), continuous assessment of LV function for 162 +/- 136 minutes was performed using a new nuclear device. The results were compared with those of a group of normal subjects (n = 10) monitored for 80 +/- 28 minutes. Episodes of EF reduction of > 7% from baseline for a total duration of > 5% monitored time occurred in 0 of 10 normal subjects; episodes were more frequent in patients with stable angina (10 of 21, 48%; p = 0.01), with recent myocardial infarction (7 of 11, 64%; p = 0.004), and with unstable angina (11 of 13, 85%; p = 0.0001). The number of EF decreases per hour in patients after myocardial infarction (1.7 +/- 2.5 [SD]) and unstable angina (1.2 +/- 0.7) was significantly more frequent than in normal subjects (0.3 +/- 0.4), but was not different from that in patients with stable angina (0.8 +/- 1.0). The duration of the decrease in EF, expressed as minutes per hour of monitored time in normal subjects (0.7 +/- 1.0%), was significantly less than in patients with unstable angina (10 +/- 8%). Patients with stable angina (6 +/- 9%) and recent myocardial infarction (6 +/- 6%) were not significantly different from normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)