EFFECTS OF AMIODARONE ON CARDIAC ELECTROPHYSIOLOGY IN RIGHT-VENTRICULAR RAPID PACING-INDUCED HEART-FAILURE DOGS

AIM: To study the effects of amiodarone (Ami) on cardiac electrophysio logic properties and ventricular fibrillation threshold (VFT) in right ventricular rapid pacing-induced congestive heart failure (CHF) dogs. METHODS: Dogs (n = 25) were randomly allocated into 3 groups: A) cont rol group; B) CHF group induced by right ventricular rapid pacing (4 p ulses.s(-1)) for 4 - 5 wk; C) CHF models po Ami 300 mg.d(-1) for 4 - 5 wk. The electrophysiologic parameters and VET were evaluated by elect ric stimulation and monophasic action potential (MAP) recording. RESUL TS: In CHF models, ventricular MAP duration (MAPD(90)), ventricular la te repolarization duration (VLRD), and intraventricular conduction tim e (IVCT) were prolonged by 43 %, 318 %, and 19 %, respectively; the ra tio of ventricular effective refractory period (VERP) to MAPD(90) (VER P/MAPD(90)) and VFT were decreased by 13 % and 48 % respectively; the dispersion of ventricular recovery time (RT-D) was increased by 185 %. In CHF models, Ami had no effects on ventricular MAPD(90), but increa sed VERP/MAPD(90), IVCT, and VFT by 15 %, 10 %, and 67 %, respectively , shortened VLRD by 87 %; and decreased RT-D by 87 %. Ami had no signi ficant influences on the hemodynamic parameters of the CHF dogs. CONCL USION: Ami normalizes the cardiac electrophysiologic properties in CHF dogs.