Table 5.

Vaughan Williams Classification

Class	Action	Representative drugs
Class I	Na+ channel blockade
IA	PR interval/QRS duration: prolong intermediatelyQT interval: prolong	quinidine, procainamide, disopyramide, cibenzoline, pirmenol
IB	PR interval/QRS duration: no changeQT interval: shortening	lidocaine, mexiletine, aprindine
IC	PR interval/QRS duration: prolong stronglyQT interval: no change	propafenone, flecainide, pilsicainide
Class II	Adrenergic β receptor blocker	propranolol, metoprolol, bisoprolol, etc.
Class III	APD prolongation (K+ channel blockade)	amiodarone, sotalol, nifekalant
Class IV	Ca2+ channel blockade	verapamil, diltiazem, bepridil

Abbreviation: APD, action potential duration.