Classifications of Antiarrhythmic Agents 

Updated: Apr 18, 2019
Author: Ethan Levine, DO;

Classifications of Antiarrhythmic Agents

As the number of available drugs with antiarrhythmic properties increased, the need for a conceptual framework for their classification became increasingly important.[1, 2] The classification scheme most commonly in use today is the eponymously titled Vaughan Williams classification.[3] The basis of this classification is the grouping of agents according to their general effect.

In the years since the widespread adoption of the Vaughan Williams classification, there has been an exponential increase in our understanding of cardiac electrophysiology, the mechanisms of cardiac arrhythmia, and the discovery of new ion channels. In light of these more recent advances, there has been some criticism of the Vaughan Williams classification, most notably by the arrhythmia working group of the European Society of Cardiology, who, in 1991, proposed an alternative classification commonly referred to as the Sicilian gambit.[4] While these investigators raised several valid concerns, the Vaughan Williams classification remains in widespread use and is requisite knowledge for those working in the field of cardiac electrophysiology.[5]

The list below contains the classically described members of each drug class but is not comprehensive.

Class I: Fast sodium (Na) channel blockers

See the list below:

  • Ia -Quinidine, procainamide, disopyramide (depress phase 0, prolonging repolarization)

  • Ib -Lidocaine, phenytoin, mexiletine (depress phase 0 selectively in abnormal/ischemic tissue, shorten repolarization)

  • Ic -Flecainide, propafenone, moricizine (markedly depress phase 0, minimal effect on repolarization)

Class II: Beta blockers (partial list)

See the list below:

  • Propranolol (decreases slope of phase 4)

  • Esmolol (decreases slope of phase 4)

  • Timolol (decreases slope of phase 4)

  • Metoprolol (decreases slope of phase 4)

  • Atenolol (decreases slope of phase 4)

Class III: Potassium (K) channel blockers

See the list below:

  • Amiodarone (prolongs phase 3; also acts on phases 1, 2, and 4)

  • Sotalol (prolongs phase 3, decreases slope of phase 4)

  • Ibutilide (prolongs phase 3)

  • Dofetilide (prolongs phase 3)

Class IV: Slow calcium (Ca) channel blockers

See the list below:

  • Verapamil (prolongs phase 2)

  • Diltiazem (prolongs phase 2)

Class V: Variable mechanism

See the list below:

  • Adenosine

  • Digoxin

  • Magnesium sulfate