Amodarone loading therapy, beta-blockers and digitalis in patients with atrial fibrillation and structural heart disease: Is there danger of early proarrhythmic effects?

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Background: Amiodarone (Amio) is considered the most efficient and safe antiarrhythmic drug in the treatment of atrial fibrillation (AF). Though proarrhythmic effects under Amio are rare, the aim of the present study was to identify clinical constellations which may lead to Amio associated proarrhythmia. Methods: 63 consecutive patients (pts) with persistent or paroxysmal AF [14 female and 49 male, 64 10.3 years; 35 with coronary (CAD) and 11 with congestive (CHD) heart disease] were included in this retrospective analysis. All received an oral (92.1%) or i.v. (7.9%) loading dose of Amio in hospital. Cardiac diseases, concomitant treatment and proarrhythmic effects were analyzed. Results: 11 pts (17.5%) were concomitantly treated with a beta-blocker, 19 pts (30.2%) with digitalis. In 12 pts (19.0%) Amio was used in combination with both beta-blockers and digitalis. 3 pts (4.8%) developed a clinical relevant Torsade de pointes tachycardia (TdP), 3-48h after initiation of Amio loading (2 pts i.v., 1 pt oral). In all pts with proarrhythmia, Amio was initiated with concomitant beta-blocker-/digitalis-therapy. 25% with this ‘triple’ therapy developed TdP. The mean QTc was prolonged (483.7ms 61.8ms), mean heart was decreased (61.0 7.5bpm vs. 74.5 24.1bpm; p 0.05). CAD was present in all of these pts, in 2 pts left ventricular ejection fraction (EF) was severely reduced (30%). EF in pts treated for heart failure with triple therapy (40.8 10.8%) was not signifcantly different as compared to pts with beta-blocker (42.7 11.9%) or digitalis (48.9 11.9%) alone. Conclusion: Out of 63 consecutive pts with initiation of Amio therapy, in 3 pts TdP were observed. These were characterized by CAD and a combination-therapy of Amio with beta-blockers and digitalis. As a result of the changes in the treatment of heart failure, use of beta-blockers with digitalis is more widespread. The present study implicates that additional Amio therapy in such pts with AF may increase the risk of Amio-associated proarrhythmia and predispose to the development of TdP. P6-112 UNUSUAL MANIFESTATIONS OF ENDLESS LOOP TACHYCARDIA IN A CARDIAC RESYNCHRONIZATION DEFIBRILLATOR *Sergio L. Pinski, MD and Marcelo E. Helguera, MD. Cleveland Clinic Florida, Weston, FL.