Objectives The purpose of this study was to investigate the relationship between the onset of asystole and transient loss of consciousness (TLOC) in tilt-induced reflex syncope and estimate how often asystole was the principal cause of TLOC. Background The presence of asystole in vasovagal syncope (VVS) may prompt physicians to consider pacemaker therapy for syncope prevention, but the benefit of pacing is limited in VVS. Methods We evaluated electrocardiography, electroencephalography, blood pressure, and clinical findings during tilt-table tests. Inclusion required TLOC (video), electroencephalographic slowing, accelerating blood pressure decrease, and an RR interval ≥3 s. We excluded cases with nitroglycerin provocation. Asystole after onset of TLOC (group A) or within 3 s before TLOC (group B) was unlikely to cause TLOC, but an earlier start of asystole (group C) could be the cause of TLOC. Results In one-third of 35 cases (groups A [n = 9] and B [n = 3]), asystole was unlikely to be the primary cause of TLOC. The median of the mean arterial pressure at the onset of asystole was higher when asystole occurred early (45.5 mm Hg, group C) than when it occurred late (32.0 mm Hg, groups A and B), which suggests that vasodepression was not prominent at the start of asystole in early asystole, further suggesting that early asystole was the prime mechanism of syncope. Conclusions In one-third of cases of tilt-induced asystolic reflex syncope, asystole occurred too late to have been the primary cause of TLOC. Reliance on electrocardiography data only is likely to overestimate the importance of asystole.
Bibliographical noteFunding Information:
Dr. Thijs has received grants from the Dutch Epilepsy Foundation, Medtronic, Nuts OHRA Foundation, AC Thomson Foundation, and ZonMw and personal fees from UCB Pharma S.A., and GlaxoSmithKline. Dr. Benditt has received personal fees and other income from Medtronic Inc. and St. Jude Medical Inc. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
© 2017 American College of Cardiology Foundation
- reflex syncope
- tilt-table testing