Vaughan Williams antiarrhythmic classification

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Dr. E. M. Vaughan William's classification [1] is the most widely used scheme for antiarrhythmic agents and has stood the test of time.[2] This scheme classifies a drug based on the primary mechanism of its antiarrhythmic effect. Class V is a miscellaneous class, and may be subject to change if a further definite mechanism of anti-arrhythmic action is characterised. Many drugs will have subsidiary actions that are nonetheless important, so sotalol was actually first marketed as a beta-blocker and amiodarone was first developed as a potential anti-anginal vasodilator as it has calcium-channel blocking actions (and every other class except V!)


Class I agents

The class I antiarrhythmic agents interfere with the sodium (Na+) channel. They are subgrouped by their effects on the Na+ channel and cardiac action potentials.

Class Ia agents

Class Ia agents block the fast sodium channel which depresses the phase 0 depolarization (reduces Vmax), and prolongs the action potential duration.

Class Ib agents

Class Ib antiarrhythmic agents are sodium channel blockers that decrease Vmax in partially depolarized cells with fast response action potentials.

Class Ic agents

Class Ic antiarrhythmics markedly depress the phase 0 depolarization (decreasing Vmax) being the most potent sodium channel blockers.

Class II agents

Class II agents are beta-blockers

Class III agents

They predominantly block the K+ efflux channel.

Class IV agents

Class IV agents are slow calcium channel blockers. They decrease conduction through the AV node.

Class V agents


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