Comparison of the effects of sleep, exercise and autonomic drugs on ventricular extrasystoles, using ambulatory monitoring of electrocardiogram and electroencephalogram.

Ambulatory monitoring of the electrocardiogram (ECG) and the electroencephalogram (EEG) in 12 untreated patients with frequent ventricular extrasystoles showed a significant decrease in both ventricular extrasystoles and heart rate during sleep. The decrease in ventricular extrasystoles correlated more closely with the change in heart rate than with the level of arousal. During wakefulness, similar changes in ventricular extrasystoles and heart rate could be produced by the intravenous administration of propranolol and, to a lesser extent, by phenylephrine. Exercise produced an initial increase in ventricular extrasystoles, with suppression at higher levels in most patients. Thus, the frequency of ventricular extrasystoles is usually reduced at both extremes of heart rate, and the changes that occur during sleep can be explained by autonomic mediation, with the sympathetic limb of the autonomic nervous system having a greater effect than the vagus.