Nocturnal angina pectoris. Comparison between angina with ST segment elevation and depression documented by continuous orthogonal ECG recording.

In 30 patients with nocturnal angina, the night-time ECGs were continuously recorded, and the time and duration of attack, cyclic character of attacks, the relation of chest pain to ischemic ECG changes and arrhythmias during attack were compared between 18 cases with ST elevation and 12 cases with ST depression during attack. In cases with ST elevation, 1) attacks occurred between 2:00 and 8:00 a.m., being most frequent between 4:00 and 5:00 a.m. 2) the duration of attack measured from the duration of ischemic ECG changes was less than 5 min in 88% of the attacks, 3) the attack often recurred with intervals less than 30 min and ECG changes were often unaccompanied bt chest pain, 4) the attack was complicated with various kinds of arrhythmias. These features were in marked contrast to the cases with ST depression, in which attacks were evenly distributed over the night-time, of longer duration, sporadic in occurrence and far less complicated with arrhythmias. These data suggest that the difference of mechanisms causing attacks between both groups.