Abstract P387: Sub-Perception Transdermal Vagal Stimulation in Postural Tachycardia Syndrome

Abstract

Postural Tachycardia Syndrome (POTS) is a clinical syndrome characterized by an excessive increase in heart rate (>= 30 bpm) on standing in the absence of orthostatic hypotension, and frequent orthostatic symptoms for more than 6 months. While most researchers focus on the hyperadrenergic features of POTS, these patients also have significant cardio-vagal (parasympathetic) impairment. We tested the hypothesis that transdermal electrical stimulation of the auricular branch of the vagus nerve will enhance cardio-vagal modulation, reduce heart rate, upright symptoms, and improve orthostatic tolerance. We studied 14 patients with POTS (31.5+/-11.7 years, BMI 22.6+/-3.9 kg/m 2 ). Sham or sub-perception threshold transdermal electrical vagal stimulation was applied in random order to the auricular branch in the right ear in supine and during graded tilt maneuver. Patients with low vagal modulation (low high frequency HF < 200 ms 2 ) responded to vagal stimulation (Kruskal Wallis p=0.01, n=7, Fig left) with significant increase in HF power (eg @50Hz: +51+/-10 ms 2 , p=0.0032). Vagal stimulation during upright tilt tended to reduce orthostatic tachycardia and overall orthostatic symptom score. It improved significantly tilt time (+5.3+/-2.6 min, p=0.0156, Fig right). Patients with higher baseline vagal modulation (HF >= 200 ms 2 ) did not respond to vagal stimulation (interaction p=0.41). This proof of concept study indicates that auricular transdermal vagal stimulation improves supine cardio-vagal function in POTS patients with low vagal modulation. Further research will determine if this approach can be used therapeutically, alone or in combination with other therapies.