Baroreflex sensitivity predicts the induction of ventricular arrhythmias by cesium chloride in rabbits

Previous studies have shown that the autonomic nervous system plays an impo rtant role in the genesis of ventricular tachycardia (VT) in patients with long VT syndrome, and in cesium chloride (Cs)-induced VT in animals. The pr esent study investigated whether baroreflex sensitivity predicts the induct ion of VT by Cs in the rabbit in vivo. Monophasic action potentials (MAPs) of the left ventricular endocardium were recorded simultaneously with the s urface ECG in 27 rabbits. Rabbits were divided into 4 groups based on the C s-induced ventricular arrhythmias: (1) no ventricular premature contraction s (No-VPC group), (2) single or paired VPC (VPC group), (3) monomorphic VT (MVT group), and (4) polymorphic VT (PVT group). Baroreflex sensitivity was significantly lower in the MVT and PVT groups than in the No-VPC and VPC g roups. The plasma norepinephrine concentration before Cs injection was sign ificantly higher in the MVT group than in the other 3 groups, and the norep inephrine concentration after Cs injection was significantly higher in the MVT and PVT groups than in the No-VPC and VPC groups. Baroreflex sensitivit y was negatively correlated with the norepinephrine concentration before Cs injection. These results suggest that autonomic nervous system dysfunction , as defined by reduced baroreflex sensitivity, and elevated plasma norepin ephrine concentrations predict increased susceptibility to Cs-induced VT.