Effects of vagus nerve stimulation on cardiovascular regulation in patients with epilepsy

OBJECTIVE: To evaluate the impact of vagus nerve stimulation (VNS) on heart rate and blood pressure (BP) modulation in epilepsy patients. MATERIAL AND METHODS: Twenty-one epilepsy patients with VNS were tested during on (60 s) and off (5 min) phases. We monitored BP, RR intervals (RRI) and respiration. Spectral analysis was performed in low- (LF: 0.04-0.15 Hz) and high-frequency bands (HF: 0.15-0.5 Hz). For coherences above 0.5, we calculated the LF transfer function between systolic BP and RRI, and the HF transfer function gain and phase between RRI and respiration. Differences between the on and off phases were evaluated using Wilcoxon test. RESULTS: VNS did not change RRI and BP values. The LF power of BP and the LF and HF power of RRI increased significantly. There was a slight change in the RRI/BP LF gain and the RRI/respiration HF gain (ns). The HF phase between RRI and respiration decreased significantly. CONCLUSIONS: Our findings show that VNS influences both sympathetic and parasympathetic cardiovascular modulation. However, our results also show that VNS does not negatively influence autonomic cardiovascular regulation.