Effects of disopyramide and quinidine on action potentials of canine ventricular myocardium and Purkinje fibers after myocardial infarction
Abstract
Mongrel dogs were anaesthetized with sodium pentobartital. A left thoractomy was performed and the left anterior descending coronary artery was ligated in two stages. After 3-5 d, the dogs were anaesthetized and the hearts were excised. Preparations consisting of roughly equal portions of normal and infarcted areas were removed. The effects of disopyramide (D) and quinidine (Q) (both 0.2, 2, 20, 200μmol/L) on non-infarcted (Nif) and infarcted (Inf) tissues were analyzed by standard microelectrode techniques. Intracellular action potentials (AP) were recorded from ventricular muscle fibers (VM) and Purkinje fibers (PF) in 16 isolated epicardial (Epi) and endocardial (Endo) preparations, respectively.
D and Q both decreased APA and Vmax of PF and VM cells in Nif and Inf areas. In both zones, the conduction time of PF were prolonged and the conduction velocity of VM were slowed down by D and Q. There were differential effects of D and Q on APD. D had the same prolongation effect on APD50 and APD95 of PF and VM in Nif and Inf. Under the action of Q in both Nif and Inf zones APD50 of PF were unchanged and APD95 of PF were lenthened, but on the contrary, starting from low concentration APD50 and APD95 of VM were consistently shortened. Increases in ERP after D and Q were significantly greater in Inf than those in Nif fibers.
Keywords:
D and Q both decreased APA and Vmax of PF and VM cells in Nif and Inf areas. In both zones, the conduction time of PF were prolonged and the conduction velocity of VM were slowed down by D and Q. There were differential effects of D and Q on APD. D had the same prolongation effect on APD50 and APD95 of PF and VM in Nif and Inf. Under the action of Q in both Nif and Inf zones APD50 of PF were unchanged and APD95 of PF were lenthened, but on the contrary, starting from low concentration APD50 and APD95 of VM were consistently shortened. Increases in ERP after D and Q were significantly greater in Inf than those in Nif fibers.