Mechanisms of Action of Drugs Used in Cardiac Arrhythmias

Cardiac arrhythmia is defined as disturbance of initiation or conduction of cardiac impulse. Most of us have occasional disturbances (ripple) of cardiac rhythm which are transient and go unnoticed. Normal healthy heart, not genetically predisposed to arrhythmia, is resistant to such minor disturbances by triggers. However, sometimes arrhythmias can be symptomatic and certain arrhythmias are fatal, e.g. those following acute MI. Anti-arrhythmic drugs are the drugs used to prevent or correct cardiac arrhythmias. The antifibrillatory drugs are compounds which prevent the development of atrial and ventricular fibrillation. The antifibrillatory drugs must be differentiated from the defibrillatory drugs i.e. drugs capable of restoring normal sinus rhythm of the heart under atrial and ventricular fibrillation. Although many drugs are able to arrest rapid atrial and ventricular arrhythmias, no drug is available that can consistently restore normal rhythm to a fibrillating ventricle