Author + information
- Lilei Yu, MD, PhD,
- Menglong Wang, MD,
- Bing Huang, MD, PhD and
- Hong Jiang, MD∗ ()
- ↵∗Department of Cardiology, Renmin Hospital of Wuhan University, No. 238 Jiefang Road, Wuchang District, Wuhan City, Hubei Province 430060, People’s Republic of China
We thank Drs. Castro and Nobrega for their valuable comments. Although the auricular branch of the vagus nerve was found at the tragus in only 45% of those cases, it was found at the antihelix and cymba conchae in 73% and 100% of cases, respectively. It should be noted that these anatomic structures are very close and maybe highly connected to each other.
The beneficial effects of parasympathetic drugs on myocardial infarction were suggested many years ago (1). However, we believe parasympathetic dysfunction is not the underlying mechanism for ameliorative effects of low-level tragus stimulation (LL-TS) on ischemia-reperfusion injuries. The cardioprotective role of LL-TS may be due to the decreased inflammatory responses, which has been validated by both basic and clinical studies. The intensity of stimulation we used is well below that which slows heart rate and atrioventricular conduction, both standard “parasympathetic” responses. Furthermore, studies have shown that vasostatin-1, rather than the parasympathetic neurotransmitter acetylcholine, mediates the cardioprotective effects of LL-TS or LL vagus nerve stimulation (2). In addition, based on previous studies, LL-TS is antiadrenergic, through a nitric oxide–dependent way (3,4).
With regard to the selection of right or left tragus, we think that TS, no matter at the right or the left side, first activates the afferent nerve and transmits signals to the nucleus tractus solitaries, which integrates afferent information and further projects processed signals to the heart through bilateral efferent cervical vagal nerves. Therefore, we suggest that electrical stimulation at the left- or right-sided tragus may exert similar cardioprotective effects. Relative to the duration for the cardioprotective effects of LL-TS, it has been demonstrated that transcutaneous vagus nerve stimulation (120/s and 3 times a day) could reduce serum inflammatory cytokine levels at 24 h after initial stimulation in healthy volunteers (5). We are registering a prospective, multicenter, and randomized clinical trial, and believe this trial will provide more definitive evidence for the cardioprotective effects of LL-TS in STEMI patients.
Please note: This work was supported by grants from the National Nature Science Foundation of China (Nos. 81530011, 81570463, and 81600395), the Natural Science Foundation of Hubei Province (Nos. 2016CFA065 and 2016CFA048), the Foundation of Health and Family Planning Commission of Hubei Province (No. WJ2017C0005). The authors have reported that they have no relationships relevant to the contents of this paper to disclose.
- 2017 American College of Cardiology Foundation