All-night polygraphic studies of nocturnal angina pectoris.

In 12 patients with nocturnal angina pectoris, all-night continuous polygraphic recordings were made, including electroencephalogram, electrooculogram, electromyogram, impedance pneumogram and electrocardiogram, and ECG was analyzed in relation to heart rate and sleep stages. Out of 58 episodes of ischemic ST,T changes which were recorded with the peak frequency between 4:00 and 6:00a.m., 24 were REMassociated and 21 occurred in awake state. The number of attacks per hour in individual sleep stages was most prominent in REM sleep stage. In 3 cases episodes were seen only in awake period, and in 1 case in NREM sleep stages alone. The analyses of ECG and heart rate during sleep disclosed that the attacks were not likely to be induced by REM-associated increase of heart rate and, in individual episodes, heart rate increase did not precede the ST,T changes. The triggering mechanism of attacks remains to be investigated. Two representative cases were presented.