Potassium channel blocker
Potassium channel blockers are agents which interfere with conduction through potassium channels.
Potassium channel blockers used in the treatment of cardiac arrhythmia are classified as class III antiarrhythmic agents.
Class III agents predominantly block the potassium channels, thereby prolonging repolarization. More specifically, their primary effect is on IKr.
Since these agents do not affect the sodium channel, conduction velocity is not decreased. The prolongation of the action potential duration and refractory period, combined with the maintenance of normal conduction velocity, prevent re-entrant arrhythmias. (The re-entrant rhythm is less likely to interact with tissue that has become refractory).
Class III antiarrhythmic agents exhibit reverse use dependent prolongation of the action potential duration (Reverse use-dependence). This means that the refractoriness of the ventricular myocyte increases at lower heart rates. This increases the susceptibility of the myocardium to Early Afterdepolarizations (EADs) at low heart rates. Antiarrhythmic agents that exhibit reverse use-dependence are more efficacious at preventing a tachyarrhythmia than converting someone into normal sinus rhythm. Because of the reverse use-dependence of class III agents, at low heart rates class III antiarrhythmic agents may paradoxically be more arrhythmogenic.
These agents include a risk of torsades de pointes.
Sulfonylureas come under the class of ATP-sensitive potassium channel blockers.
Dalfampridine, A potassium channel blocker has also been approved for use in the treatment of multiple sclerosis.
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