Circadian rhythm of ventricular tachycardia.

A 24-hr electrocardiographic monitoring was performed in 406 patients (297 with ischemic heart disease). Forty-one episodes of ventricular tachycardia were detected in 32 subjects (7.88%). The average rate of tachycardia was 127.4 (range 180-65). No correlation was observed between the rate of ventricular tachycardia and the heart rate 30, 20, and 10 min before and at the moment of the episode. A circadian rhythm of all the episodes was demonstrated, with an acrophase at 1102 hr. A different acrophase was observed for the QT interval. No significant rhythm was observed for premature ventricular beats in the patients with ventricular tachycardia. The circadian variation of tachycardia suggests that this arrhythmia is related to sympathetic tone, but it will require further studies with a larger number of patients with ventricular tachycardia to clarify this problem.