Cardiovascular Adverse Drug Reactions during Initiation of Antiarrhythmic Therapy for Atrial Fibrillation

Abstract

ABSTRACT Background: Patients with atrial fibrillation are often admitted to hospital for pharmacological cardioversion. However, it has been suggested that for patients without underlying heart disease, it might be safe to initiate antiarrhythmic drug therapy in the community setting. Objective: To compare the frequency of cardiovascular adverse drug reactions during attempted pharmacological cardioversion of atrial fibrillation in patients with and without underlying heart disease. Methods: A review of health records for patients admitted to hospital over a 1-year period for pharmacological cardioversion of atrial fibrillation or for whom atrial fibrillation was the primary diagnosis. Cardiovascular adverse reactions were defined as one or more of the following: bradycardia (heart rate less than 60 beats per minute), hypotension (systolic blood pressure less than 100 mm Hg), sinus pause (greater than 2 s), prolonged QT interval (longer than 0.55 s), or ventricular proarrhythmia (ventricular tachycardia, including torsades de pointes). Results: During the study period, 106 patients received a total of 175 drug courses for conversion of atrial fibrillation. Of these drug courses, 81 (46%) resulted in at least one cardiovascular adverse drug reaction, and 21 (12%) resulted in discontinuation of the drug therapy. For drug courses given to patients with underlying heart disease, there was a significantly higher relative risk of cardiovascular adverse drug reactions (66% versus 36% of drug courses; relative risk 1.83, 95% confidence interval 1.33 to 2.51), and a nonsignificant trend toward increased risk of drug discontinuation because of these adverse reactions (19% versus 9%; relative risk 2.16, 95% confidence interval 0.99 to 4.72). Conclusion: The risk of cardiovascular adverse drug reactions during initiation of antiarrhythmic therapy was higher for patients with underlying heart disease; however, even for patients without other heart disease, the risk of adverse drug reactions appeared high enough to warrant admission to hospital. RESUME Historique : Les patients atteints de fibrillation auriculaire sont souvent admis a l’hopital pour une cardioversion pharmacologique. Cependant, il existe des recommandations a l’effet que le traitement antiarythmique pouvait etre amorce de facon sure dans les milieux communautaires chez les patients qui souffrent de fibrillation auriculaire en absence de cardiopathie. Objectif : Comparer la frequence des reactions cardiovasculaires indesirables secondaire a une cardioversion pharmacologique de la fibrillation auriculaire chez les patients qui avaient ou non une cardiopathie sous-jacente. Methodes : Les dossiers medicaux des patients admis a l’hopital au cours d’une periode d’une annee pour une cardioversion pharmacologique d’une fibrillation auriculaire ou pour qui la fibrillation auriculaire etait le diagnostic primaire ont ete passes en revue. Les reactions cardiovasculaires indesirables ont ete definies comme etant la bradycardie (frequence cardiaque inferieure a 60 bpm), l’hypotension (tension systolique inferieure a 100 mm de Hg), l’arret (de plus de 2 s), l’intervalle Q-T allonge (superieur a 0,55 s), ou encore la proarythmie ventriculaire (tachycardie ventriculaire, y compris torsades de pointes). Resultats : Au cours de la periode d’etude, 106 patients ont recu un total de 175 cardioversions pharmacologiques pour leur fibrillation auriculaire. De ces traitements medicamenteux, 81 (46 %) ont provoque au moins une reaction cardiovasculaire indesirable et 21 (12 %) ont entraine l’arret du traitement. Chez les patients atteints d’une cardiopathie sous-jacente et qui ont recu une cardioversion pharmacologique, le risque relatif de reaction cardiovasculaire indesirable etait considerablement superieur (66 % contre 36 %; risque relatif de 1,83; intervalle de confiance a 95 % : 1,33 a 2,51) et on a observe une tendance non significative de risque accru d’interruption du traitement a cause des reactions cardiovasculaires indesirables au medicament (19 % contre 9 %; risque relatif de 2,16; intervalle de confiance a 95 % : 0,99 a 4,72). Conclusion : Le risque de reaction cardiovasculaire indesirable durant l’administration du traitement antiarythmique etait plus eleve chez les patients qui souffraient de fibrillation auriculaire et de cardiopathie sous-jacente. En revanche, meme chez les patients ne presentant aucune autre cardiopathie, le risque de reaction indesirable au medicament semblait etre suffisant pour commander l’hospitalisation.