Left cardiac sympathetic denervation reduces skin sympathetic nerve activity in patients with Long QT syndrome

BACKGROUND Although left cardiac sympathetic denervation (LCSD) is an effective antiarrhythmic therapy for patients with long QT syndrome (LQTS), direct evidence of reduced sympathetic activity after LCSD in humans is limited. OBJECTIVE The purpose of this study was to assess skin sympathetic nerve activity (SKNA) in patients with LQTS undergoing LCSD. METHODS We prospectively enrolled 17 patients with LQTS who underwent LCSD between 2017 and 2019. SKNA recordings from the left arm (L-SKNA) and chest (C-SKNA) leads were performed before and after LCSD. Mean SKNA, burst activity, and nonburst activity of L-SKNA and C-SKNA were analyzed. RESULTS The mean patient age was 21 +/- 9 years (8 men 47%). The longest baseline corrected QT value was 497 +/- 55 ms at rest and 531 +/- 38 ms on exercise stress testing. Five patients (29.4%) had previous LQTS-triggered cardiac events including syncope, documented torsades de pointes, and ventricular fibrillation. In the 24 hours after LCSD, mean L-SKNA decreased from 1.25 +/- 0.64 to 0.85 +/- 0.33 mu V (P = .005) and mean C-SKNA from 1.36 +/- 0. 67 to 1.05 +/- 0.49 mu V (P = .11). The frequency of episodes of SKNA bursts recorded from the left-arm lead (2.87 +/- 1.61 bursts per minute vs 1.13 +/- 0.99 bursts per minute; P < .001) and mean L-SKNA during burst (1.82 +/- 0.79 1.tV vs 1.15 +/- 0.44 mu V; P < .001) and nonburst (1.09 +/- 0.60 mu V vs 0.75 +/- 0.32 mu V; P = .03) periods significantly decreased after LCSD, while the frequency of episodes of SKNA bursts recorded from the chest lead (P = .57) and mean C-SKNA during burst (P = .44) and nonburst (P = .10) periods did not change significantly. No arrhythmic events were documented after 11.9 months (range 3.0-22.2 months) of follow-up. CONCLUSION LCSD provides an inhibitory effect on cardiac sympathetic activity by suppressing burst discharge as measured by SKNA.