Arrhythmia is an abnormality of the rate, rhythm or site of origin of the cardiac impulse or an abnormality in the impulse conduction. Cardiac arrhythmias may be due to abnormal generation or conduction of impulses. Anti-arrhythmics are mainly grouped into sodium channel blockers, beta adrenergic blockers, potassium channel blockers and calcium channel blockers. Sodium channel blockers depress phase 0 depolarization and depress all cardiac properties including automaticity, excitability, conduction velocity, and prolongs repolarization. Class 1B drugs block the sodium channels and also shorten repolarization. Beta blockers depress myocardial contractility, automaticity and conduction velocity. Amiodarone is a powerful antiarrhythmic and acts by multiple mechanisms. Verapamil is used to terminate PSVT.