Skin sympathetic nerve activity and the temporal clustering of cardiac arrhythmias

BACKGROUND. Simultaneous noninvasively recorded skin sympathetic nerve activity (SKNA) and electrocardiogram (neuECG) can be used to estimate cardiac sympathetic tone. We tested the hypothesis that large and prolonged SKNA bursts are associated with temporal clustering arrhythmias. METHODS. We recorded neuECG in 10 patients (69 +/- 10 years old) with atrial fibrillation (AF) episodes and in 6 patients (50 +/- 13 years old) with ventricular tachycardia (VT) or fibrillation (VF) episodes. Clustering was defined by an arrhythmic episode followed within 1 minute by spontaneous recurrences of the same arrhythmia. The neuECG signals were bandpass filtered between 500-1000 Hz to display SKNA. RESULTS. There were 22 AF clusters, including 231 AF episodes from 6 patients, and 9 VT/VF clusters, including 99 VT/VF episodes from 3 patients. A total duration of SKNA bursts associated with AF was longer than that during sinus rhythm (78.9 min/hour [interquartile range (IQR) 17.5-201.3] vs. 16.3 min/hour [IQR 14.5-18.5], P = 0.022). The burst amplitude associated with AF in clustering patients was significantly higher than that in nonclustering patients (1.54 mu V [IQR 1.35-1.89], n = 114, vs. 1.20 mu V [IQR 1.05-1.42], n = 21, P < 0.001). The SKNA bursts associated with VT/VF clusters lasted 9.3 +/- 3.1 minutes, with peaks that averaged 1.13 +/- 0.38 mu V as compared with 0.79 +/- 0.11 mu V at baseline (P = 0.041). CONCLUSION. Large and sustained sympathetic nerve activities are associated with the temporal clustering of AF and VT/VF.