Quinidine Polygalacturonate

The Authors report a case of incessant torsade de pointes, associated with QT prolongation, due to the proarrhythmic effect of quinidine, which was successfully treated with i.v. verapamil. The arrhythmia occurred after oral administration of quinidine polygalacturonate (550 mg + 275 mg + 275 mg over a 4-hour period) for the conversion of atrial fibrillation in a 41-year-old woman with mild mitral stenosis and regurgitation. Verapamil was administered as an i.v. bolus (5 mg at a rate of 1 mg/min) and with in four minutes the arrhythmia disappeared. The electrophysiological mechanisms of torsade de pointes and the potential role of Ca+(+)-channel-blocking agents in its treatment are briefly discussed.

The efficacy of the association of verapamil plus quinidine in 70 patients with atrial fibrillation, 64 of them after having cardiac surgery, was assessed. Oral dosage ranged from 825 mg to 1,100 mg for quinidine polygalacturonate and 240 mg to 320 mg for verapamil. All patients but two reached a good control of heart rate (mean heart rate less than 110 beats/min) while arrhythmia persisted. Sixty patients (85.7%) reverted to normal sinus rhythm in a period of 2.4 +/- 1.5 days (mean +/- SD). According to the atrial fibrillation duration three subsets of patients with different conversion rates to sinus rhythm were established (p less than 0.01): group A (lasting from 1 day to 3 months) 31/39 (96%); group B (lasting 3 to 6 months) 18/21 (85.7%) and group C (lasting 6 to 12 months) 5/10 (50%) (p less than 0.01). Plasma quinidine levels were maintained at either near to or therapeutic range (2.6 +/- 0.94 micrograms/ml). Adverse effects comprised one ventricular arrhythmia-induced syncope (quinidine syncope) and two cases of systemic hypotension. Quinidine-verapamil association is a good alternative in the treatment of atrial fibrillation, particularly in those of recent onset, according to the high rates of conversion to normal sinus rhythm, affording control of heart rate while atrial fibrillation persists. Adverse reactions did not differ in severity from those observed with quinidine monotherapy.