Cardiovascular effects of auricular stimulation -a systematic review and meta-analysis of randomized controlled clinical trials

Author: Kevin Hua1, Mike Cummings2, Miriam Bernatik3, Benno Brinkhaus1, Taras Usichenko4,5, Joanna Dietzel1
1 Institute for Social Medicine, Epidemiology and Health Economics, Berlin Institute of Health, Charité - University Medicine, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, Berlin, Germany.
2 British Medical Acupuncture Society, London, United Kingdom.
3 International Society for Chinese Medicine, Munich, Germany.
4 Department for Anesthesiology, University Hospital Greifswald, Greifswald, Germany.
5 Department of Anesthesia, McMaster University, Hamilton, ON, Canada.
Conference/Journal: Front Neurosci
Date published: 2023 Sep 1
Other: Volume ID: 17 , Pages: 1227858 , Special Notes: doi: 10.3389/fnins.2023.1227858. , Word Count: 332

The number of randomized controlled trials using auricular stimulation (AS) such as transauricular vagus nerve stimulation, or other auricular electrostimulation or auricular acupuncture or acupressure, in experimental and clinical settings, has increased markedly over the last three decades. This systematic review focusses on cardiovascular effects of auricular stimulation.

Methods and analysis:
The following databases were searched: MEDLINE (PubMed), EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), ISI Web of Science, and Scopus Database. RCTs were reviewed that had been published in English and European languages. Data collection and analysis was conducted by two reviewers independently. Quality and risk assessment of included studies was performed and the meta-analysis of the effect of the most frequently assessed biomarkers.

Altogether, 78 trials were included. 38 studies assessed heart rate (HR), 19 studies analyzed heart rate variability (HRV), 31 studies analyzed blood pressure (BP) and 7 studies were identified that measured oxygen saturation (O2), 2 studies on baroreflex sensitivity and 2 studies on skin conductance were evaluated in this review. 26 studies contained continuous data and were eligible for meta-analysis, 50 trials reported non continuous data and were evaluated descriptively. The overall quality of the studies was moderate to low. AS leads to a significant reduction of HR, the changes though were not considered an adverse reaction. Furthermore, when looking at HRV, AS was able to reduce the LF/HF ratio significantly compared to control procedures. No other cardiovascular parameters (blood pressure, oxygen saturation, baroreflex sensitivity) were changed significantly. AS produced only minor side effects in all trials.

AS can lead to clinically safe reduction of HR and changes in the LF/HF ratio of the HRV, which is presumably via an increase in vagal activity. More research is needed to clarify whether AS can be used to modulate tachycardia or indications with autonomic imbalance.

Systematic review registration: PROSPERO, ID CRD42021231885.

Keywords: auricular acupuncture; auricular stimulation; cardiovascular; randomized controlled trials; systematic review; transauricular vagus nerve stimulation.

PMID: 37727325 PMCID: PMC10505819 DOI: 10.3389/fnins.2023.1227858