Circadian variation of vasovagal syncope

Circadian Variation of Vasovagal Syncope, Introduction: Circadian patterns have been demonstrated for several cardiovascular catastrophes. Chronobiologic factors play a role in the emergence of vasovagal syncope (VVS); however, diurnal variation of syncopal episodes in WS has not been reported previously, Methods and Results: We assessed daily distribution of the time of syncopal episodes in VVS, Time of syncope could be determined in 80 episodes in 54 patients (32 men and 22 women; mean age 37 years, range 12 to 67). Patients who were prescribed beta blockers or vasodilators, and who had syncopes related to alcohol intake, were excluded from the study, Head-up tilt testing was performed in 53 patients The distribution of the episodes of VVS in 3-hour intervals differed significantly from uniform occurrence (P < 0.0001), with a peak frequency between 6 A.M. and noon (67.5% of total episodes), In patients who had experienced the initial syncope in the morning, most (78%) of the next syncopal episodes also occurred in the morning. There was no significant correlation between the time of last syncopes and tilt testing results, Conclusion: We demonstrated a prominent circadian variation in the frequency of WS, with a peak in the morning. Recognition of the daily distribution of VVS is useful for patient education and therapeutic strategy.