3-DIMENSIONAL ACTIVATION SEQUENCE OF CESIUM-INDUCED VENTRICULAR ARRHYTHMIAS

To investigate the electrophysiological and electrocardiographic chara cteristics of ventricular arrhythmia due to abnormal repolarization, w e studied the three-dimensional activation sequence of cesium-induced ventricular tachycardia (VT) in 10 anesthetized dogs using a 384-chann el recording system. Seventeen monomorphic VT (mVT) and eight polymorp hic VT (PVT) episodes induced by cesium chloride (2 or 3 mM/kg) were a nalyzed. Only a single arrhythmogenic focus was detected in most beats of VT, whereas two competing foci were temporarily observed in two ep isodes of pVT. The site of arrhythmogenic focus of mVT was the endocar dium (5 of 17), the midmyocardium (4 of 17), or undetermined (8 of 17) . Both endocardial and midmyocardial arrhythmogenic foci were also fou nd in pVT, and most pVT (6 of 8) were associated with the transition o f the site of arrhythmogenic focus. These results are consistent with the view that both myocardial muscle fibers and Purkinje cells can cau se ventricular arrhythmia due to abnormal repolarization and that chan ging the site of arrhythmogenic focus is the main mechanism of pVT.