Cesium chloride induced ventricular arrhythmias in dogs: three-dimensionalactivation patterns and their relation to the cesium dose applied

Introduction: Cesium chloride has widely been used in experimental models t o produce various ventricular arrhythmias. The study was designed to evalua te whether type and mechanism of these arrhythmias are dose-dependent. Methods: In 7 dogs with acute AV-block, 60 pins containing 4 bipolar electr odes each were inserted into both ventricles to provide 240 endo-, epi- and midmyocardial recording sites. A computerized mapping system was used to d etermine three-dimensional activation patterns of ventricular arrhythmias i nduced by three injections of 1mmol/kg cesium chloride at 20 minute interva ls. Results: Out of all arrhythmias induced, 25 ventricular extrasystoles, 31 m onomorphic and 47 polymorphic ventricular tachycardias were mapped. Nonsust ained ventricular tachycardias were readily inducible by a single bolus of cesium chloride, whereas sustained episodes required repetitive injections (1.45 +/- 0.61 vs. 2.61 +/- 0.57 doses, p < 0.05). Polymorphic tachycardias were observed more commonly than monomorphic tachycardias (87 vs. 31). Ini tiation and maintenance of cesium induced arrhythmias were exclusively base d on focal mechanisms originating from the subendocardium, irrespective of morphology and dosage. All monomorphic arrhythmias were caused by repetitiv e firing of single immobile foci located in either the right or the left ve ntricle. Bi- and multifocal mechanisms, however, were found to underlie the polymorphic episodes. Conclusions: Although there is a dose-dependence as to the sustenance of mo no- or polymorphic tachycardias, this does not reflect on the three-dimensi onal activation pattern of cesium induced arrhythmias, which are due to mon o- or multifocal activation originating from the subendocardium.