title: Circadian and infradian rhythms of vasovagal syncope in young and middle-aged subjects.
abstract: BACKGROUND
  The most cardiovascular physiological and pathophysiological events show a circadian rhythm. It is thought that the autonomic nervous system and biologic factors play a key role in the pathogenesis of vasovagal syncope (VVS). In this study, we investigated the circadian and infradian variation of VVS.
  
  
  METHODS
  A prospective consecutive series of 246 patients (142 women; mean age 36+/-7 years) with recurrent syncope and with a positive head-up tilt testing (HUT) were included in this study. The daily and weekly distributions of the syncopal episodes were investigated. The assessments of episodes were done according to the days of the week and three time periods of the day (6 a.m.-12 noon, 12 noon-6 p.m., 6 pm-12 midnight).
  
  
  RESULTS
  According to the results of HUT, 76 patients (31%) had cardioinhibitory, 62 patients (25%) had vasodepressor, and 108 patients (44%) had mixed type of VVS. During the initial passive phase, 40% of patients (99/246) showed positive response. Time to syncope was 20+/-2 minutes during HUT. The mean number of syncopal episodes was 4+/-2/years. In all, 1,070 episodes were evaluated. The distribution of the episodes in 6-hour intervals was significantly different from uniform occurrence (38%, 33%, and 29%, respectively) (P=0.02). The frequency of episodes was higher in the morning (P=0.045) and in the middle of the week (P=0.046). A significant difference was found between week and weekend days in terms of the frequency of episodes (75.5% vs 24.5%, P=0.01).
  
  
  CONCLUSIONS
  VVS may show a circadian and infradian rhythm.
authors.affiliation: Department of Cardiology, Ege University Medical Faculty, Izmir, Turkey.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Zoghi
authors.forename: Hamza
authors.initials: H
authors.lastname: Duygu
authors.forename: Hasan
authors.initials: H
authors.lastname: Gungor
authors.forename: Sanem
authors.initials: S
authors.lastname: Nalbantgil
authors.forename: Filiz
authors.initials: F
authors.lastname: Ozerkan
authors.forename: Azem
authors.initials: A
authors.lastname: Akilli
authors.forename: Mustafa
authors.initials: M
authors.lastname: Akin
mesh_terms: D000328:Adult; D001794:Blood Pressure; D021081:Chronobiology Disorders / Q000503:physiopathology*; D002940:Circadian Rhythm; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D019462:Syncope, Vasovagal / Q000503:physiopathology*