Editing Antiarrhythmic agent (section)

==Action potential==
[[File:Cardiac action potential.svg|thumb|440px|class=skin-invert-image|Drugs affecting the [[cardiac action potential]]|alt=Plot of membrane potential versus time]]

{{main|Cardiac action potential}}

The cardiac myocyte has two general types of action potentials: conduction system and working myocardium. The action potential is divided into 5 phases and shown in the diagram. The sharp rise in voltage ("0") corresponds to the influx of sodium ions, whereas the two decays ("1" and "3", respectively) correspond to the sodium-channel inactivation and the repolarizing efflux of potassium ions. The characteristic plateau ("2") results from the opening of voltage-sensitive [[calcium channel]]s. Each phase utilizes different channels and it is useful to compare these phases to the most common classification system — Vaughan Williams — described below.