Experimental Study of the Effect of Autonomic Nervous System on the Transmural Dispersion of Ventricular Repolarization under Acute Myocardial Ischemia in Vivo

The electrophysiologic heterogeneity of the ven-tricular myocardium is an important factor of devel-oping ventricular arrhythmia.Under the pathologiccondition,thedistribution and thefunction of the au-tonomic nerves,especially the sympathetic nerve,can produce the heterogeneity in the myocardium,which can accelerate the electrophysiologic hetero-geneity of the ventricular myocardium.Acute my-ocardial ischemia can induce the dysfunction of theautonomic nerve endings,resulting in the hetero-gene…

Experimental Study of the Effect of Autonomic Nervous System on the Transmural Dispersion of Ventricular Repolarization under Acute Myocardial Ischemia in Vivo

Summary: The effect of the autonomic nerves on the transmural dispersion of ventricular repolariza tion (TDR) under acute myocardial ischemia in intact canine was investigated. Using the monophasic action potential (MAP) recording technique, MAPs of the epicardium (Epi), midmyocardium (Mid) and endocardium (Endo) were recorded simultaneously by specially designed plunge-needle electrodes at the left ventricular free wall under acute myocardial ischemia in 12 open-chest dogs.MAPD90 and TDR among three myocardial layers as well as the incidence of the early afterdepolar ization (EAD) before autonomic nervous stimulation and during autonomic nervous stimulation were compared. It was found that 10 min after acute myocardial I~hemia, TDR was increased from 55±8.ms to 86± 15 ms during sympathetic stimulation (P＜0. 01). The TDR (53± 9 ms) during parasympathetic stimulation was not significantly different from that of the control (55±8 ms) (P＞0.05). The EAD was elicited in the Mid of 2 dogs (16 %) 10 min after acute myocardial ischemia,but the EAD were elicited in the Mid of 7 dogs (58 %) during sympathetic stimulation (P＜0. 01).It was concluded that: (1) Sympathetic stimulation can increase the transmural dispersion of repolari zation and induce early afterdepolarizations in the Mid under acute myocardial ischemia, which pro-vide the opportunity for the ventricular arrhythmia developing; (2) Parasympathetic stimulation has no significant effect on the transmural dispersion of repolarization under myocardial ischemia.