Clinical and experimental pharmacology & physiology
-
Clin. Exp. Pharmacol. Physiol. · Sep 1996
Differential effects of antiarrhythmic agents on post-pause repolarization in cardiac Purkinje fibres.
1. Marked action potential duration (APD) prolongation with agents such quinidine is often a precursor of early after-depolarizations and triggered activity, thought to be underlying mechanism of torsade de pointes. Episodes of torsade de pointes commonly occur following a pause. 2. ⋯ None of D-sotalol, clofilium or dofetilide exhibits significant sodium channel blockade and, thus, these agents do not manifest post-pause prolongation of repolarization. Disopyramide does produce sodium channel blockade, but recovery from this effect is much slower than for quinidine or amitriptyline (time constant 12-50s). Thus, we propose insufficient recovery occurs during the intervals under study to uncover the action potential-prolonging effect of the unopposed potassium channel blockade for disopyramide.