Characteristics of dynamic electrocardiogram, heart rate variability, and electrophysiological study in a Chinese population with vasovagal syncope

Background: Little is known about characteristics of dynamic electrocardiogram (DCG), heart rate (HR) variability (HRV), and invasive electrophysiological study (EPS) in the presence, pattern, and stage of vasovagal syncope (VVS) during head-up tilt test (HUTT). The present study aims to explore predictive value of these tests for HUTT outcomes with underlying mechanisms. Subjects and Methods: This retrospective study consecutively enrolled 519 patients with VVS from January 2007 to December 2017. Parameters of DCG, HRV, and EPS were evaluated according to the presence, pattern, and stage of syncope during HUTT. Results: Mixed pattern was the predominant subtype of VVS, and vasodepressor patients had a positive response earlier than in cardioinhibitory patients. Compared with negative group, positive group with mixed and cardioinhibitory patterns had significantly slower maximal HR and mean HR all day, at daytime, nighttime, and each hour point. No significance was observed in parameters of HRV between negative and positive groups. There was no significant difference in HR, spectral power components, and time-domain variables among syncopal patterns and syncopal stages. Positive group had longer durations of A-H interval, sinus node recovery time, Wenckebach point, and Wenckebach 2:1 point than negative group. There was a significant difference only in sinus node recovery time among syncopal patterns as well as A-H interval among syncopal stages. Conclusion: DCG-derived HR and EPS properties rather than 24-h HRV may be used to predict positive responses, but they could not predict syncopal patterns and syncopal stages.