Background and Objective Increased transmural dispersion ofrepolarization (TDR) has been shown to contribute to initiation and maintenance of ventricular arrhythmia in long QT syndromes (LQTS).Intercellular uncoupling through gap junctions is an important mechanism for maintaining TDR in both intact and diseased heart.The present study was to test the hypothesis that improving gap junction communication reduces TDR and prevents ventricular arrhythmia in rabbit LQT2 model.Methods An arterially perfused rabbit left ventricular preparation and E4031 (0.5μmol/L) were used to establish a model of LQT2.Preparations were randomly assigned to control (n=10),AAP-100nmol/L(n=10),AAP-500nM(n=10) groups.Transmural ECG as well as action potentials from both endocardium and epicardium was simultaneously recorded.Results In LQT2 model,presence of 500nmol/L AAP 10 reduced endocardial action potential and TDR and prevented ventricular arrhythmia comparing with the control and AAP 100nmol/ L groups (P<0.05).Conclusions The presence of 500 nmol/L AAP10 reduces TDR and prevents ventricular arrhythmia in rabbit ventricular model of LQT2.This study suggests a possible role of GJs in TDR in rabbit LQT2 model and indicates a new clinical approach to the management of LQTS.
Bodi Chen Xiaoqing Quan Cuntai Zhang Jiagao Lu Rong Bai Nian Liu Yanfei Ruan Jun Ke Jin Ma Liandong Li Lei Ruan Department of Cardiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology,Wuhan 430030, China
The aim of this study was to determine if the potassium aspartate and magnesium （PAM） prevent reperfusion-induced ventricular arrhythmias （RIVA） in ischemia-reperfusion （IR） rabbit heart. Thirty rabbits were randomly divided into control, ischemia and PAM groups. Arterially-perfused rabbit left ventricular preparations were made, and transmural ECG as well as action potentials from both endocardium and epicardium were simultaneously recorded in the whole process of all experiments. In control group rabbit ventricular wedge preparations were continuously perfused with Tyrode＇s solution, and in ischemia group and PAM groups the perfusion of Tyrode＇s solution was stopped for 30 min. Then the ischemia group was reperfused with Tyrode＇s solution and the PAM group with Tyrode＇s solution containing 2.42 mg/L PAM, respectively. ECG, QT interval, transmural repolarization dispersion （TDR） and action potentials from epicardium and endocardium were simultaneously recorded, and the RIVA of the wedge preparation was observed. Compared with control group, TDR and incidence of RIVA were significantly increased in ischemia group （P〈0.05）. The incidence of RIVA in control, ischemia and PAM group was 0/10, 9/10 and 1/10, respectively. Compared with ischemia group, TDR and incidence of RIVA were significantly reduced in PAM group （P〈0.05）. Potassium aspartate and magnesium significantly reduce TDR and prevent ventricular arrhythmia in ischemic rabbit heart.
