Antiarrhythmic Therapy

Posted by e-Medical PPT Thursday, August 26, 2010
Antiarrhythmic drugs are a group of pharmaceuticals that are used to suppress fast rhythms of the heart such as atrial fibrillation, atrial flutter, ventricular tachycardia, and ventricular fibrillation.Antiarrhythmic agents may be considered the first-line therapy in the prevention of sudden death in certain forms of structural heart disease, and failure of these agents to suppress arrhythmias may lead to implantation of an implantable cardioverter-defibrillator (ICD).
There are five main classes in the Vaughan Williams classification of antiarrhythmic agents:
* Class I agents interfere with the sodium (Na+) channel.
* Class II agents are anti-sympathetic nervous system agents. Most agents in this class are beta blockers.
* Class III agents affect potassium (K+) efflux.
* Class IV agents affect calcium channels and the AV node.
* Class V agents work by other or unknown mechanisms.
The class I antiarrhythmic agents interfere with the sodium channel and they are also called Membrane Stabilizing agents.Class II agents are conventional beta blockers. They act by blocking the effects of catecholamines at the β1-adrenergic receptors, thereby decreasing sympathetic activity on the heart.Class III agents predominantly block the potassium channels, thereby prolonging repolarization.Class IV agents are slow calcium channel blockers. They decrease conduction through the AV node, and shorten the plateau phase of the cardiac action potential.

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