Heart blocks during sleep: a case report in a healthy subject.

Cardiac arrhythmia was fortuitously discovered during an experimental sleep recording in a healthy 50-year-old man. a 24 hr electrocardiographic (ECG) monitoring revealed the prevalence of these abnormalities during sleep and their absence during the awake period. Sleep and ECG were recorded during 4 consecutive nights. Numerous (500-1, 100 events/night) heart blocks and sinus pauses occurred 60-80 min after going to bed. They were never observed during awakenings and were exacerbated during paradoxical sleep. The atrioventricular blocks were of the Wenckebach-Luciani type. No other abnormality was found. These conduction abnormalities are discussed as possibly due to phasic increases in vagal firing, which during paradoxical sleep would be superimposed on the tonic increase in heart rate.