Association Between Cardiac Acceleration Capacity and Susceptibility to Vasovagal Syncope: Autonomic Dysregulation in...

Vasovagal syncope (VVS) might be associated with alterations in vagal activity. Cardiac acceleration capacity (AC) is a novel index related to autonomic modulation. It remains unknown whether AC could be used to assess vagal tone and differentiate VVS patients.

This study aimed to investigate the association between AC and VVS, and evaluate the capability of AC to identify VVS susceptibility.

In this observational study, 204 VVS patients (41.2 ± 16.9 years, 40.2% [82 of 204] men) were included, of whom 87.3% (178 of 204) VVS patients had positive responses to tilt-table testing, and 116 asymptomatic individuals were included as controls. Twenty-four-hour Holter monitoring was performed for all participants. Multivariate logistic regression analysis and receiver-operating characteristic curves were performed for heart rate variability metrics.

VVS patients exhibited significantly higher AC than control subjects (8.81 ± 2.21 ms vs 5.89 ± 1.27 ms; P < 0.001). AC correlated with deceleration capacity (VVS: r = 0.90 [95% CI: 0.83-0.96]; controls: r = 0.92 [95% CI: 0.85-1.00]) and other vagal-dominant heart rate variability metrics. In multivariate models, increased AC was significantly associated with an elevated risk of VVS (adjusted OR: 3.54 [95% CI: 2.55-4.91]). Daytime AC showed strong discriminative power for VVS (area under curve 0.910 [95% CI: 0.879-0.942]), and outperformed nighttime measures in the identification of VVS.

Higher AC was observed in VVS patients during the nonsyncopal period, indicative of AC's potential association with vagal modulation. Daytime AC showed superior performance in detecting VVS susceptibility, offering a noninvasive approach to assisting clinical diagnosis.