Is the denervation or hyperinnervation of the cardiac sympathetic nerve in the subepicardium related to unexpected cardiac death?

BackgroundPast studies have reported that abnormal innervation of cardiac sympathetic nerve can cause sudden cardiac death through the arrythmogenesis; however, the severe cardiac sympathetic degeneration does not necessarily cause clinical problems. This study aimed to examine whether denervation or hyperinnervation of cardiac sympathetic nerves in the subepicardium is associated with unexpected cardiac death (UCD).MethodsCardiac tissues of 278 forensic autopsy cases within 48 h after death were analyzed by double-staining immunohistochemistry for tyrosine hydroxylase and neurofilament. The density of nerve fascicles and the degeneration rate in the subepicardium of the left ventricular anterior wall were compared between the UCD group and the non-UCD group.ResultsThe density of nerve fascicles was lower in the SCD group (median: 51.9/cm2) than in the non-SCD group (median: 58.9/cm2); however, the difference was not significant (P=.08). The degeneration rate was higher in the SCD group (median: 0.19) than in the non-SCD group (median: 0.17), but again, the difference was not significant (P=.43). The multiple logistic regression model did not show a significant association between the incidence of UCD and the density of nerve fascicles or the degeneration rate.ConclusionsIt cannot be concluded that the denervation or hyperinnervation of cardiac sympathetic nerves in the subepicardium is related to UCD. Abnormal innervation of cardiac sympathetic nerves in the subepicardium may not have a substantial effect on UCD, compared to other arrhythmogenic factors.