Cardiac Effects of Vagus Nerve Stimulation in Patients with Major Depression

Introduction: Changes in the heart rate variability are well known among patients with depression. Amongst others, a modulation of the autonomic nervous system is discussed. An investigation of heart rate variability during terms of stimulation could give some insight in the central nervous effect of vagus nerve stimulation (VNS) and possible cardiac side effects. Methods: The effects of VNS on heart rate (HR) and heart rate variability were studied (HRV) during stimulation in nine patients with major depression according to ICD-10. Results: When comparing treated depressive patients with a sex- and age-matched healthy control group, the analysis of heart rate revealed significantly (t = 2.8; df = 16, p = 0.012) elevated heart rates during completely switched off conditions, during switched on VNS programme in stimulation-free intervals (5 min period) (t = 3.0; p = 0.009) and during stimulation conditions (30 s) (t = 2.8, Levene corrected, p = 0.015). The RMSSD (root mean square of successive differences) as a measure of the HRV increased significantly in switched on conditions during stimulation (30 s) in six patients compared to stimulation-free intervals (t = -4.7; df = 5, p = 0.006) and baseline. Discussion: Clinically relevant cardiac effects were not observed throughout the study. VNS induces reversible changes in heart rate variability in patients with major depression during stimulation conditions.