Effects of amiodarone versus quinidine and verapamil in patients with chronic atrial fibrillation: Results of a comparative study and a 2-year follow-up

Abstract

Rapid, reliable and safe reestablishment of sinus rhythm is the major aim of pharmacologic treatment in patients with chronic atrial fibrillation. The mainstay of therapy in this arrhythmia has been quinidine. More recently, amiodarone was shown in non-comparative studies to be superior to class IA agents under certain conditions. In 40 patients with atrial fibrillation persisting for 4 weeks up to 2 years, the efficacy and safety of either quinidine and verapamil (days 1 to 3, quinidine 1,500 mg/day; days 4 to 6, quinidine 1,500 mg + verapamil 240 mg/day) or amiodarone therapy (days 1 to 3, amiodarone 1,200 mg/day intravenously; days 4 to 14, amiodarone 800 mg/day orally) were randomly examined. Responders continued on their effective medication for 3 months. Thereafter, all patients were treated with a fixed regimen of quinidine (480 mg/day) plus verapamil (240 mg/day) for up to 2 years.During atrial fibrillation, quinidine reduced mean ventricular cycle length by 40 ms (−5%), quinidine and verapamil increased mean cycle length by 57 ms (8%) and amiodarone by 192 ms (28%, p < 0.01). In addition, quinidine and verapamil had a characteristic “rate-smoothing” effect on atrioventricular conduction during atrial fibrillation. The rhythm was converted to sinus rhythm after quinidine in 5 (25%) of 20 patients and after the combination of quinidine and verapamil in 11 (55%) of 20 patients. Amiodarone restored sinus rhythm in 12 (60%) of 20 patients. Overall, a shorter duration of atrial fibrillation (p < 0.05) and a smaller left atrial size (p < 0.01) were predictive of successful conversion of the arrhythmia.In one patient on each regimen, medication was stopped because of side effects. Transient side effects occurred in 13 patients (33%), 5 receiving quinidine and verapamil and 8 receiving amiodarone. During long-term treatment, amiodarone could be safely replaced by quinidine and verapamil. Among 23 drug responders, atrial fibrillation recurred in 2 (1st 3 months), 5 (1st year) and 7 patients (2 years); side effects limited long-term therapy in 2 patients.In summary, a similar efficacy rate of 50% to 60% to reestablish sinus rhythm favors the clinical situation (e.g., left ventricular function, fast ventricular rate) to select the drug of choice for a particular patient. When sinus rhythm is reestablished, quinidine and verapamil provide a safe and effective therapeutic regimen in 60% of patients over a 2-year follow-up period.