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 noncomparitive 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.(ABSTRACT TRUNCATED AT 250 WORDS)