Quinidine for Pharmacological Cardioversion of Long-lasting Atrial Fibrillation

Background: In the daily clinical practice, patients with atrial fibrillation (AF) lasting more than 48h (or not datable at all) are not uncommon. In long-lasting AF changes in electrophysiological features (electrical remodeling) can occur, resulting in a loss of sensibility to most antiarrhythmic drugs. There is strong evidence that the main mechanism involved in electrical remodeling is a global shortening in refractory period. To assess safety and efficacy of quinidine in pharmacological cardioversion of long-lasting AF, compared with propafenone and amiodarone. Methods and Results: Ninety consecutive patients with AF lasting more than 6 weeks were randomized to amiodarone (5mg\kg bolus, then 15mg\kg in 24h) , propafenone (2 mg\kg bolus then 0.007mg\kg for 2h), and quinidine (275mg of quinidine arabogalattan sulphate per os every 2h for 8h maximum) for pharmacologic cardioversion. All patients had been previously treated with adequate oral anticoagulation and had been submitted to transthoracic echocardiogram. The 3 groups of patients did not differ for baseline and echocardiographic characteristics. Sinus rhythm was restored in 16 patients treated with quinidine (53%), compared with 6 patients (20%) in the amiodarone and propafenone groups (p<0.01). No major adverse effect was reported during the treatment. Conclusions: Quinidine seems to be safe and effective in pharmacological cardioversion of long-lasting AF.