24-HOUR VARIATION IN THE OCCURRENCE AND SURVIVAL OF POTENTIALLY LETHAL VENTRICULAR TACHYARRHYTHMIA

The temporal pattern in the occurrence and primary outcome of resuscit ation of out-of-hospital ventricular fibrillation/tachycardia was stud ied. The onset time of 117 cases of tachyarrhythmia exhibited a double -peaking 24-h variation with a first prominent peak in the midmorning and a second less prominent one during the late afternoon and early ev ening hours. Survival after resuscitation also was time dependent, sho wing a quite different temporal pattern. Survival was lowest during th e daytime and greatest (four to five times greater) during the night. The findings are consistent with the hypothesis that out-of-hospital v entricular fibrillation/tachycardia may be dependent on autonomic regu lation.