Copyright © 1999 by the European Society of Cardiology.
Conversion of recent onset paroxysmal atrial fibrillation to normal sinus rhythm: the effect of no treatment and high-dose amiodarone. A randomized, placebo-controlled study
a Department of Medicine ‘A’ Assaf Harofeh Medical Center, Zerifin, Israel
b The Cardiology Institute, Assaf Harofeh Medical Center, Zerifin, Israel
c The Clinical Pharmacology Research Unit, Assaf Harofeh Medical Center, Zerifin, Israel
revised June 7, 1999; accepted June 9, 1999
Abstract
Background Spontaneous conversion of recent onset paroxysmal atrial fibrillation to normal sinus rhythm occurs commonly and is not affected by low-dose amiodarone treatment.
Methods In a randomized, placebo-controlled trial of 100 patients with paroxysmal atrial fibrillation of recent onset (<48h) we compared the effects of treatment with continuous intravenous amiodarone 125mg per hour (total 3g) and intravenous placebo. Patients in the placebo group who did not convert to normal sinus rhythm within 24h were started on amiodarone therapy.
Results Conversion to normal sinus rhythm occurred within 24h in 32 of 50 patients (64%) in the placebo group, most of whom converted within 8h. Lower conversion rates were observed in patients with hypertension, ischaemic heart disease or congestive heart failure and in patients with echocardiographic findings of left atrial diameter above 45mm, ejection fraction below 45% or significant mitral regurgitation. However, in most patients these clinical or echocardiographic risk factors of decreases in conversion rate were not present. In such patients the spontaneous conversion rate was approximately 90%. The conversion rate during 24h of treatment in the amiodarone group was 92% (P=0·0017, compared to the placebo group). In this group, the conversion rate was largely unaffected by baseline characteristics. Of the 18 patients who did not convert with placebo, 15 (85%) converted after being crossed over to amiodarone. All patients not responding to high-dose amiodarone were in chronic atrial fibrillation within 1 month. In patients still in atrial fibrillation after 8h of treatment, the pulse rate decreased significantly more in the amiodarone as compared to the placebo group (83±15 vs 114±20 beats.min–1,P =0·0014).
Conclusion The spontaneous conversion of recent onset paroxysmal atrial fibrillation is high and approaches 90% in specific clinical and echocardiographically defined subgroups. Intravenous high-dose amiodarone safely facilitates conversion of paroxysmal atrial fibrillation. However, such treatment should be reserved for patients with unfavourable risk factor profiles, not converting during 8h of observation or requiring rate control.
Key Words: Paroxysmal atrial fibrillation, conversion to normal sinus rhythm, amiodarone
f1 Correspondence: Dr Cotter at the Cardiology Institute, Assaf-Harofeh Medical Center, Zerifin 70300, Israel.
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