Vestibulo–sympathetic interaction and otolith function in postural orthostatic tachycardia syndrome

Background and Objective: The association between blood pressure variability (BPV) or heart rate variability (HRV) and the baroreflex is well established. However, the role of the vestibular–autonomic reflex in regulating BP and HR stability has primarily been explored only in experimental studies. We aimed to delineate the association of BPV and HRV with otolith function in postural orthostatic tachycardia syndrome (POTS). Methods: We retrospectively analyzed data from consecutive patients with POTS recruited between April 2021 and April 2025 at a tertiary referral-based hospital in South Korea. All patients underwent a head-up tilt table test using a Finometer^® device and cervical (cVEMP) and ocular vestibular evoked-myogenic potentials (oVEMP). The Finometer data were analyzed using a power spectral analysis. The Finometer, cVEMP, and oVEMP data were compared with those of 32 age- and sex-matched healthy participants. Results: A total of 47 patients with POTS (mean age ± standard deviation [SD] = 33 ± 10 years; 30 female patients) and 32 age- and sex-matched healthy participants were included for analysis. The n1–p1 amplitude of oVEMP was larger in patients with POTS than in healthy participants (p = 0.002). p13 latency was negatively correlated with the SD of heart rate in the supine position in patients with POTS (p = 0.001), a trend not observed in healthy participants. The n1–p1 amplitude (odds ratio [95% confidence interval] = 1.27 [1.08–1.49], p = 0.004) and root mean square of successive differences (RMSSD) during tilting (0.82 [0.72–0.93], p = 0.001) were associated with POTS after adjusting for other covariates. Conclusions: Otolithic function may play a role in accentuating BPV and HRV in POTS by contributing to enhanced sympathetic outflow.