Pilot trial finds acute taVNS effects on blood pressure differ by stimulation site and hypertension status

BACKGROUND: and PurposeTranscutaneous auricular vagus nerve stimulation (taVNS) has emerged as a promising noninvasive strategy to modulate autonomic function and reduce blood pressure (BP). However, whether the stimulation site influences acute cardiovascular responses remains unclear. OBJECTIVE: To compare the acute effects of taVNS applied to the tragus and cymba conchae on BP and cardiac autonomic modulation in hypertensive and healthy individuals. METHODS: This pilot randomized crossover clinical trial included 14 hypertensive and 14 healthy participants who underwent two taVNS sessions (tragus and cymba conchae) in randomized order, one week apart. Sessions lasted 30 min and delivered a sinusoidal current (30 Hz, 500 ms pulse width), with intensity adjusted to the individual sensory threshold. Systolic BP (SBP), diastolic BP (DBP), and heart rate variability (HRV) parameters were assessed at baseline, during stimulation, and post-stimulation. Generalized estimating equations were used for analysis. RESULTS: A significant group × time × stimulation site interaction was observed for SBP (χ = 19.0, p = 0.001) and DBP (χ = 10.0, p = 0.038). Cymba conche stimulation reduced BP in healthy individuals, whereas no meaningful BP changes were observed in hypertensive participants. Tragus stimulation reduced diastolic BP only in the hypertensive group. Significant interactions were also detected for normalized spectral HRV components and sample entropy (p < 0.05), though autonomic responses were modest and not consistently indicative of enhanced parasympathetic modulation. DISCUSSION: Acute taVNS induces site- and group-dependent cardiovascular responses, with limited clinical impact after a single session. These findings suggest that short-term stimulation may be insufficient to overcome impaired autonomic regulation in hypertension and highlight the need for repeated or longer stimulation protocols in future clinical trials.