P2437Low level transcutaneous vagus nerve stimulation acutely ameliorates diastolic function in humans

Background: Recent animal and human studies suggest that a systemic proinflammatory state, produced by comorbidities, including aging, plays a central role in the development of HFpEF. We have recently shown that low-level transcutaneous vagus nerve stimulation (LLTS) for 1 hour decreased inflammatory cytokines and improved autonomic tone in humans. Purpose: We aimed to evaluate the acute effects of LLTS on diastolic dysfunction and autonomic tone. Methods: We conducted a prospective, randomized, double-blind, 2x2 cross over pilot study. Patients with normal left ventricular (LV) ejection fraction and evidence of diastolic dysfunction on previous echocardiograms were included. Patients received 2 separate, 1-hour sessions, at least 1 day apart, of active and sham LLTS, with the sequence of the sessions being randomized. LLTS (20Hz, 1mA below the discomfort threshold) was performed using a transcutaneous electrical nerve stimulation (TENS) device with electrodes attached to the tragus of the ear. Sham stimulation was performed at the earlobe, which is devoid of vagal innervation. Echocardiography was performed after 1 hour of LLTS or sham stimulation to assess diastolic function. A 5-minute ECG was performed at baseline and at 1 hour to assess heart rate variability (HRV), a measure of autonomic tone. HRV parameters included: 1. time domain: standard deviation of normal RR intervals (SDNN); 2. frequency domain: powers of high (0.15 to 0.4 Hz; HF) and low (0.04 to 0.15 Hz; LF) ranges, and the ratio of LF to HF power (LF/HF).