Atrial Fibrillation in Acute Obstructive Sleep Apnea: Autonomic Nervous Mechanism and Modulation

Background--The mechanisms of atrial fibrillation (AF) induced by obstructive sleep apnea (OSA) are not completely understood. This study investigated the roles of the intrinsic and extrinsic cardiac autonomic nervous system in OSA-induced AF and provided noninvasive autonomic nervous modulation for the suppression of OSA-induced AF by using low-level transcutaneous electrical stimulation (LL-TS) of the auricular branch of the vagus nerve at the tragus. Methods and Results--Eighteen dogs received tracheostomy under general anesthesia and were randomly divided into 3 groups: the OSA group (OSA was simulated via clamping of the endotracheal tube at end expiration for 1.5 minutes every 10 minutes, n= 6), the LL-TS + OSA group (simulated OSA plus LL-TS, at 80% of the slowing sinus rate, n= 6), and the control group (sham surgery without stimulation, n= 6). The effective refractory period was significantly shortened after 1 hour of simulated OSA, and the window of vulnerability and plasma norepinephrine levels were both markedly increased in the OSA group. OSA dramatically increased the neural function and activity of the intrinsic and extrinsic cardiac autonomic nervous system, including the superior left ganglionated plexus, the left stellate ganglion, and the left renal sympathetic nerve. OSA also significantly upregulated the expression levels of c-fos and nerve growth factor in the superior left ganglionated plexus and the left stellate ganglion. However, LL-TS markedly improved these parameters. Conclusions--These findings suggest that the intrinsic and extrinsic cardiac autonomic nervous system plays crucial roles in the acute stage of OSA-induced AF. Noninvasive LL-TS suppressed shortening of atrial refractoriness and autonomic remodeling, which prevented OSA-induced AF.