Original Article: PDF OnlySawada Kohei; Shoji, Tadao; Igarashi, Toshiji; Hiraoka, MasayasuJournal of Cardiovascular Pharmacology: January 1987 - p 51-56 Free Abstract Summary: Effects of a new antiarrhythmic agent, E-0747, on action potentials of swine cardiac Purkinje fibers were studied using standard microelectrode techniques. E-0747 decreased the maximum rate of rise (Vmax) of action potentials at concentrations higher than 3 × 10−7M at a frequency of 1 Hz without change in resting membrane potential. E-0747 (3 × 10−6M) shifted the steady-state relationship between the Vmax and the resting membrane potential in a hyperpolarizing direction by 9.2 ± 0.9 mV. E-0747 depressed the Vmax in a rate-dependent manner. At a concentration of 3 × 10−6M, the depression was ˜50% at a stimulation of 3.3 Hz. E-0747 (3 × 10−6M) did not depress the Vmax of the first action potential after a rest period of ˜30 min, but subsequently reduced the Vmax with successive stimulations reaching a new steady level after ˜20 min. The time course of recovery from inactivation of the Vmax in the presence of E-0747 (10−6M) did not differ from that of the control. E-0747 shortened the action potential duration (APD), but did not affect the ratio of effective refractory period (ERP) to APD. These results suggest that E-0747 depresses the Vmax by closely associating with open and/or inactivated sodium channels. It may be classified as an antiarrhythmic agent of class IC type of the Vaughan Williams' classification. © Lippincott-Raven Publishers.