Three-dimensional activation sequence of cesium-induced ventricular arrhythmias.

To investigate the electrophysiological and electrocardiographic characteristics of ventricular arrhythmia due to abnormal repolarization, we studied the three-dimensional activation sequence of cesium-induced ventricular tachycardia (VT) in 10 anesthetized dogs using a 384-channel recording system. Seventeen monomorphic VT (mVT) and eight polymorphic VT (pVT) episodes induced by cesium chloride (2 or 3 mM/kg) were analyzed. Only a single arrhythmogenic focus was detected in most beats of VT, whereas two competing foci were temporarily observed in two episodes of pVT. The site of arrhythmogenic focus of mVT was the endocardium (5 of 17), the midmyocardium (4 of 17), or undetermined (8 of 17). Both endocardial and midmyocardial arrhythmogenic foci were also found in pVT, and most pVT (6 of 8) were associated with the transition of the site of arrhythmogenic focus. These results are consistent with the view that both myocardial muscle fibers and Purkinje cells can cause ventricular arrhythmia due to abnormal repolarization and that changing the site of arrhythmogenic focus is the main mechanism of pVT.