[Pharmacological restoration and maintenance of sinus rhythm by antiarrhythmic agents]

Paroxysmal atrial fibrillation is defined as an atrial fibrillation that terminates spontaneously. It is desirable that atrial fibrillation should be terminated immediately after onset, and should be prevented from re-initiation to avoid atrial electrical remodeling or atrial stunning after cardioversion. Antiarrhythmic agents are used for these reasons. The important factors for pharmacological cardioversion of atrial fibrillation are thought to be prolongation of atrial refractory and suppression of conduction time in the atrium. Therefore, class Ia and Ic antiarrhythmic drugs, including bepridil as class IV because of its characteristics of class Ia, are administered to restore sinus rhythm. Verapamil and diltiazem, or beta adrenergic blocker, or digitalis decreases the ventricular response during atrial fibrillation for disturbance of atrioventricular nodal conduction, and then cardioversion of atrial fibrillation may occur. Suppression of supraventricular extrasystoles and atrial conduction time, or prolongation of atrial refractoriness will be needed to maintain sinus rhythm. Class I, III, or bepridil as class IV excepting lidocaine and mexiletine are used to prevent paroxysmal atrial fibrillation. In general, sodium channel blocker is superior for defibrillation and potassium channel blocker is superior for prophylaxis of atrial fibrillation. Considering efficacy, antiarrhythmic agents should be selected depending on the following factors: cardiac function, renal or hepatic function, underlying heart disease, exercise-induced or enhanced mental condition, cholinergic induced, drug-resistant atrial fibrillation or not.