Electrophysiologic and voltage clamp analysis of sotalol effects in cardiac muscle and Purkinje fibers. Circulation 68

The effect of dl-, d- and /-sotalol on electrophysiologic charac-tenstics of guinea-pig papillary muscles, sheep and rabbit Pur-kinje fibers was studied. Standard electrophysiologic and voltage clamp techniques were used. At concentrations between 1 O_6 and 1 O M, the main effect of sotalol consisted of prolongation of the action potential duration. In voltage clamp experiments this effect correlated with a substantial reduction of the time-dependent K current activated during the plateau of the action potential and a small reduction of the background K current. At concentrations above 1O M, a secondary shortening of the action potential concomitant with a fall in maximal rate of depo-larization was seen. In voltage damp experiments this effect correlated with a decrease of a slowly inactivating Na current. In the absence of catecholamines d- and /-sotalol exerted identica