Antiarrhythmic effects of stimulating the left dorsal branch of the thoracic nerve in a canine model of paroxysmal atrial tachyarrhythmias

Abstract

BACKGROUND Stellate ganglion nerve activity (SGNA) precedes paroxysmal atrial tachyarrhythmia (PAT) episodes in dogs with intermittent rapid left atrial (LA) pacing. The left dorsal branch of the thoracic nerve (LDTN) contains sympathetic nerves originating from the stellate ganglia. OBJECTIVE The purpose of this study was to test the hypothesis that high-frequency electrical stimulation of the LDTN can cause stellate ganglia damage and suppress PATs. METHODS We performed long-term LDTN stimulation in 6 dogs with and 2 dogs without intermittent rapid LA pacing while monitoring SGNA. RESULTS LDTN stimulation reduced average SGNA from 4.36 mu V (95% confidence interval [CI] 4.10-4.62 mu V) at baseline to 3.22 mu V (95% CI 3.04-3.40 mu V) after 2 weeks (P5.028) and completely suppressed all PAT episodes in all dogs studied. Tyrosine hydroxylase staining showed large damaged regions in both stellate ganglia, with increased percentages of tyrosine hydroxylase-negative cells. The terminal deoxynucleotidyl transferase dUTP nick end labeling assay showed that 23.36% (95% CI 18.74%-27.98%) of ganglion cells in the left stellate ganglia and 11.15% (95% CI 9.34%-12.96%) ganglion cells in the right stellate ganglia were positive, indicating extensive cell death. A reduction of both SGNA and heart rate was also observed in dogs with LDTN stimulation but without rapid LA pacing. Histological studies in the 2 dogs without intermittent rapid LA pacing confirmed the presence of extensive stellate ganglia damage, along with a high percentage of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells. CONCLUSION LDTN stimulation damages both left and right stellate ganglia, reduces left SGNA, and is antiarrhythmic in this canine model of PAT.