Left Cervical Vagal Nerve Stimulation Reduces Skin Sympathetic Nerve Activity in Patients with Drug Resistant Epilepsy

Background We recently reported that skin sympathetic nerve activity (SKNA) can be used to estimate sympathetic tone in humans. In animal models, vagal nerve stimulation (VNS) can damage the stellate ganglion, reduce stellate ganglion nerve activity, and suppress cardiac arrhythmia. Whether VNS can suppress sympathetic tone in humans remains unclear. Objective The purpose of this study was to test the hypothesis that VNS suppresses SKNA in patients with drug-resistant epilepsy. Methods ECG patch electrodes were used to continuously record SKNA in 26 patients with drug-resistant epilepsy who were admitted for video electroencephalographic monitoring. Among them, 6 (2 men, age 40 ± 11 years) were previously treated with VNS and 20 (7 men, age 37 ± 8 years) were not. The signals from ECG leads I and II were filtered to detect SKNA. Results VNS had an on-time of 30 seconds and off-time of 158 ± 72 seconds, with output of 1.92 ± 0.42 mA at 24.17 ± 2.01 Hz. Average SKNA during VNS off-time was 1.06 μV (95% confidence interval [CI] 0.93–1.18) in lead I and 1.13 μV (95% CI 0.99–1.27) in lead II, which was significantly lower than 1.38 μV (95% CI 1.01–1.75; P = .036) and 1.38 μV (95% CI 0.98–1.78; P = .035) in the control group, respectively. Heart rate was 65 bpm (95% CI 59–71) in the VNS group, which was significantly lower than 77 bpm (95% CI 71–83) in the control group. Conclusion Patients with VNS had significantly lower SKNA than those without VNS

Simultaneous noninvasive recording of skin sympathetic nerve activity and electrocardiogram

BACKGROUND: Sympathetic nerve activity is important to cardiac arrhythmogenesis. OBJECTIVE: The purpose of this study was to develop a method for simultaneous noninvasive recording of skin sympathetic nerve activity (SKNA) and electrocardiogram (ECG) using conventional ECG electrodes. This method (neuECG) can be used to adequately estimate sympathetic tone. METHODS: We recorded neuECG signals from the skin of 56 human subjects. The signals were low-pass filtered to show the ECG and high-pass filtered to show nerve activity. Protocol 1 included 12 healthy volunteers who underwent cold water pressor test and Valsalva maneuver. Protocol 2 included 19 inpatients with epilepsy but without known heart diseases monitored for 24 hours. Protocol 3 included 22 patients admitted with electrical storm and monitored for 39.0 ± 28.2 hours. Protocol 4 included 3 patients who underwent bilateral stellate ganglion blockade with lidocaine injection. RESULTS: In patients without heart diseases, spontaneous nerve discharges were frequently observed at baseline and were associated with heart rate acceleration. SKNA recorded from chest leads (V1-V6) during cold water pressor test and Valsalva maneuver (protocol 1) was invariably higher than during baseline and recovery periods (P < .001). In protocol 2, the average SKNA correlated with heart rate acceleration (r = 0.73 ± 0.14, P < .05) and shortening of QT interval (P < .001). Among 146 spontaneous ventricular tachycardia episodes recorded in 9 patients of protocol 3, 106 episodes (73%) were preceded by SKNA within 30 seconds of onset. Protocol 4 showed that bilateral stellate ganglia blockade by lidocaine inhibited SKNA. CONCLUSION: SKNA is detectable using conventional ECG electrodes in humans and may be useful in estimating sympathetic tone