[Electrocardiographic effects and antiarrhythmic action of 1200 mg of oral amiodarone per day].

The authors administered 1 200 mg of amiodarone orally to 30 patients with paroxysmal supraventricular and ventricular arrhythmias for a period of 6 days. They evaluated the electrocardiographic modifications induced on the surface ECG as well as the anti-arrhythmic action which was assessed by continuous Holter ECG monitoring and endocavitary electrophysiological investigations. They found that the sinus rhythm was slowed by 22%, that the PR interval was prolonged by 22%, that the QTc interval was increased by 13.5% and that there were alterations in ventricular repolarisation in 48% of cases. These ECG modifications were maximal between the 5th and 7th days. The amiodarone controlled the arrhythmia in 57% of cases. Independent of the nature of the arrhythmia, the anti-arrhythmic effect appeared after a mean of 3.9 +/- 1.8 days. There was no significant relationship between the electrocardiographic modifications and the anti-arrhythmic effect. In three cases (10%), major side effects were observed, related to depression of sinus automatism. They only appeared after the 6th day. Thus, a loading dose of 1 200 mg/day of amiodarone p.o. can be administered without fear of major side effects for 4 to 5 days. Such treatment will control about 60% of cases of severe paroxysmal arrhythmias after 4 days.