Effects of auricular vagal neuromodulation therapy combined with slow-paced diaphragmatic breathing in individuals with postural tachycardia syndrome: a randomised controlled trial protocol
Tobias Brandl, Florian Pichler, Igor Grabovac, Thomas Waldhoer, Hans Keller, Dorothee Fenneker, Alexander Niessner, Ali KapanIntroduction
Postural orthostatic tachycardia syndrome (POTS) is a multifactorial disorder of the autonomic nervous system characterised by an excessive increase in heart rate (HR) on standing and a wide range of debilitating symptoms, including fatigue, exercise intolerance, cognitive impairment and a high prevalence of depression, anxiety and sleep disturbances. Conventional pharmacological strategies often offer limited relief and do not sufficiently address non-cardiac symptoms. Auricular vagal neuromodulation therapy (AVNT) and slow-paced diaphragmatic breathing (SDB) have each demonstrated promise in modulating autonomic function and alleviating symptom burden but their combined effects in POTS have yet to be investigated.
Methods and analysis
This single-centre, partially blinded, 12-week randomised controlled trial will be conducted at the Medical University of Vienna. A total of 100 participants with confirmed POTS will be recruited, with 25 per group. This sample size is already accounting for an anticipated 30% dropout rate. Participants will be randomised using stratified block randomisation with a 1:1:1:1 allocation ratio, stratified based on the presence or absence of post-exertional malaise (yes/no) to one of four groups: (1) AVNT+SDB, (2) AVNT+normal breathing, (3) sham AVNT+SDB and (4) sham AVNT+normal breathing. The primary endpoint is the change in orthostatic HR (ΔHR) during a 70° head-up tilt test. Secondary outcomes include beat-to-beat blood pressure responses, respiratory sinus arrhythmia, end-tidal CO₂, handgrip strength, activity monitoring and validated patient-reported measures, including Chalder Fatigue Scale, Malmö POTS Symptom Score, Nijmegen Questionnaire, Short Form Health Survey, Hospital Anxiety and Depression Scale and Vanderbilt Orthostatic Symptom Score. Interventions consist of daily 60-minute AVNT (or sham) sessions combined with standardised breathing training (10–15 min/day).
Ethics and dissemination
This study has been approved by the Ethics Committee of the Medical University of Vienna (EK number 1270/2024) and will be conducted in accordance with the Declaration of Helsinki and International Conference on Harmonisation-Good Clinical Practice guidelines. Results will be disseminated through peer-reviewed publications, conference presentations and reporting in the trial registry. Participants will receive study results in an accessible format.
Trial registration number