Effects of Respiratory-Gated Auricular Vagal Nerve Stimulation (RAVANS) on Nonlinear Heartbeat Dynamics of Hypertensive Patients

The association between hypertension and cardiac autonomic dysfunction is well recognized and has been proved to be involved in the progression of coronary heart disease and heart failure, suggesting this physiological marker as a potential therapeutic target. In this study, we investigate the effects of a novel, respiratory-gated, auricular vagal afferent nerve stimulation (RAVANS) technique on heartbeat dynamics of hypertensive patients. Twelve hypertensive subjects underwent two experimental sessions on non-consecutive days. In each session subjects performed an initial paced breathing (PB) task without intervention, and a second PB task with either RAVANS or sham stimulation. Electrocardiogram and respiration signals were collected and point process nonlinear analysis of heartbeat dynamics was performed to obtain instantaneous time-domain (μ_RR,〖 σ〗_RR), spectral (LF, HF, LF/HF) and bispectral (LL, LH, and HH) features. We found that exhalatory-gated RAVANS resulted in a significant increase in μ_RR, HF and HH compared with PB alone and sham, revealing modulatory effects of this technique on complex dynamics associated with parasympathetic activity. We conclude that exhalatory-gated RAVANS could be a promising intervention for the treatment of cardiac autonomic dysfunction in hypertensive subjects