Defects in this endogenous cholinergic system are associated with fatal ventricular arrhythmias. (A) Top, representative electrocardiograms from patients diagnosed with ischaemic cardiomyopathy or dilated cardiomyopathy. Middle, representative western blot images showing different expression levels of key members of the endogenous cholinergic system in the ventricular myocardium from healthy control and ischaemic cardiomyopathy (ICM) or dilated cardiomyopathy (DCM) patients with or without a history of ventricular tachycardia/ventricular fibrillation (VT/VF) episodes. Bottom, the bar graph summarizes the expression levels of the key members of the endogenous cholinergic system. *P < .05, calculated by Student’s t-test; n = 5–6 per group. Sinus rhythm, SR. (B) Experimental design for analysing the effects of the desformylflustrabromine (dFBr) on treating the ventricular arrhythmias. (C) Representative in vitro electrocardiogram recordings showed that VT/VF can be terminated by the application of the dFBr but not the vehicle (Veh). The bar graph shows the VT/VF termination rate in the two groups (right). *P < .05, calculated by Fisher’s exact test, n = 8–9 per group. (D) Representative in vivo electrocardiogram recordings showed that VT/VF can be terminated by the application of dFBr but not the Veh. The bar graph shows the VT/VF rate in the two groups (right). *P < .05, calculated by Fisher’s exact test, n = 8 per group