Each class of antiarrhythmic agents affects different ion channels or receptors within the heart muscle. Sodium channel blockers slow down the conduction of electrical impulses by inhibiting sodium ions. Beta-blockers reduce the effects of adrenaline and slow the heart rate. Potassium channel blockers prolong repolarization by blocking potassium ions. Calcium channel blockers decrease the heart rate by blocking calcium ions, and miscellaneous agents have varied mechanisms that don't fit neatly into the other categories.
