ANTIARRHYTHMIC PROPERTIES OF TEDISAMIL (KC8857), A PUTATIVE TRANSIENT OUTWARD K+ CURRENT BLOCKER

1 Rats were used to evaluate the antiarrhythmic properties of tedisamil, a novel agent with the electrophysiological properties of a Class III antiarrhythmic drug. Tedisamil was tested against coronary artery occlusion-induced arrhythmias in conscious animals. 2 The actions of tedisamil on the ECG, as well as responses to electrical stimulation, were compared with those on the configuration of epicardial intracellular action potentials recorded in vivo. 3 Tedisamil (1-4 mg kg-1, i.v.) caused bradycardia, elevated blood pressure and dose-dependently reduced ventricular fibrillation (VF) induced by occlusion of the left anterior descending coronary artery. Other ischaemia-associated arrhythmias were not so well suppressed. Antiarrhythmic activity was greatest when the tedisamil-induced bradycardia was prevented by electrically-pacing the left ventricle. 4 Tedisamil dose-dependently lengthened the effective refractory period and prevented electrically-induced VF. In vivo, tedisamil (0.5-4 mg kg-1, i.v.) prolonged the duration of epicardial intracellular action potentials by up to 400%. 5 Results showed that tedisamil possessed antifibrillatory actions in rats that were related to Class III electrophysiological actions as revealed by electrical stimulation and electrophysiological analyses.