The value of class IC antiarrhythmic drugs for acute conversion of paroxysmal atrial fibrillation or flutter to sinus rhythm

Abstract

In a single-blind randomized study, the efficacy and safety of intravenous propafenone (2 mg/kg body weight per 10 min) versus flecainide (2 mg/kg per 10 min) were assessed in 50 patients with atrial fibrillation or flutter. Treatment was considered successful if sinus rhythm occurred within 1 h. Conversion to sinus was achieved in 11 (55%) of 20 patients with atrial fibrillation treated with propafenone and in 18 (90%) of 20 with atrial fibrillation treated with flecainide (p less than 0.02). If atrial fibrillation was present less than or equal to 24 h, conversion to sinus rhythm was achieved in 8 (57%) of 14 patients in the propafenone group and 13 (93%) of 14 in the flecainide group (p less than 0.05). Atrial flutter was converted in two (40%) of five patients treated with propafenone and in one (20%) of five with flecainide (p = NS). Mean time to conversion was 16 +/- 10 min in the propafenone group versus 18 +/- 13 min in the flecainide group (p = NS). QRS lengthening (83 +/- 15 to 99 +/- 20 ms) was observed only in the patients treated with flecainide (p less than 0.001). Patients successfully treated with propafenone showed significantly higher plasma levels than those whose arrhythmia did not convert to sinus rhythm. Transient adverse effects were more frequent in the flecainide group (40%) than in the propafenone group (8%) (p less than 0.01). In conclusion, at a dose of 2 mg/kg in 10 min, flecainide is more effective than propafenone for conversion of paroxysmal atrial fibrillation to sinus rhythm. However, considering the propafenone plasma levels and very few adverse effects, the dose or infusion rate, or both, used in the propafenone group may not have been sufficient to achieve an optimal effect. Neither drug seems very effective in patients with atrial flutter.

Pharmacological conversion of recent atrial fibrillation: a randomized, placebo-controlled study of three antiarrhythmic drugs

“…Available data on the use of various regimens of propafenone loading in patients with organic heart disease are scant. This agent should be used cautiously or not at all for conversion of AF in such patients and should be avoided in patients with heart failure or severe obstructive lung disease (28,31,33,34,(36)(37)(38).…”

“…Transient hypotension and mild neurological side effects may also occur. Overall, adverse reactions are slightly more frequent with flecainide than with propafenone and these drugs should be avoided in patients with underlying organic heart disease involving abnormal ventricular function (27)(28)(29)(30)(31)(32)(33).…”

Tachycardia-Induced Change of Atrial Refractory Period in Humans

“…5,6 In addition, the incidence of successful restoration and maintenance of sinus rhythm was higher in patients with recent-onset AF than in those with chronic AF. 7,8 These findings suggested that AF was a progressive disease and that AF might be selfperpetuating. Wijffels et al 9 demonstrated that maintenance of AF by pacing in the normal goat heart resulted in the development of sustained AF within 1 to 3 weeks; these findings suggested that shortening of the effective refractory period (ERP; the so-called "electrical remodeling") was the main underlying electrophysiological change.…”

Remodelagem atrial elétrica reversa após cardioversão de fibrilação atrial isolada de longa duração

“…Persistent AF usually progresses to a permanent form and the successful restoration and maintenance of sinus rhythm largely depend on arrhythmia duration, with longstanding AF being more resistant to cardioversion and more prone to recurrence [6][7][8][9] . Both resistance to cardioversion and tendency of recurrence are strongly related to the development of electrophysiological substrates characterized by shortened atrial effective refractory period 2,4,5,[10][11][12][13] , slow conduction in the atrial myocardium 10,11,[14][15][16] and dispersion of refractoriness 4,13,17,18 .…”