Antiarrhythmic medication

Antiarrhythmic agents, also known as cardiac dysrhythmia medications, are a group of pharmaceuticals that are used to suppress abnormal rhythms of the heart (cardiac arrhythmias), such as atrial fibrillation, atrial flutter, ventricular tachycardia, and ventricular fibrillation.

Many attempts have been made to classify antiarrhythmic agents. The problem arises from the fact that many of the antiarrhythmic agents have multiple modes of action, making any classification imprecise.

The Vaughan Williams classification was introduced in 1970 by Miles Vaughan Williams.

Miles was the tutor for Pharmacology at Hertford College, Oxford; one of his students, Bramah N. Singh, contributed to the development of the classification system, and had a subsequent eminent career in the United States; the system is therefore sometimes known as the Singh-Vaughan Williams classification.

The five main classes in the Vaughan Williams classification of antiarrhythmic agents are:

With regards to management of atrial fibrillation, classes I and III are used in rhythm control as medical cardioversion agents, while classes II and IV are used as rate-control agents.

Sotalol is also a beta blockerAmiodarone has Class I, II, III & IV activity

The class I antiarrhythmic agents interfere with the sodium channel. Class I agents are grouped by what effect they have on the Na⁺ channel, and what effect they have on cardiac action potentials.

Class I agents are called membrane-stabilizing agents. The 'stabilizing' word is used to describe the decrease of excitogenicity of the plasma membrane which is brought about by these agents. (Also noteworthy is that a few class II agents like propranolol also have a membrane stabilizing effect.)

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