RISK OF INITIATING ANTIARRHYTHMIC DRUG-THERAPY FOR ATRIAL-FIBRILLATION IN PATIENTS ADMITTED TO A UNIVERSITY HOSPITAL

Background: The risks of antiarrhythmic therapy are increasingly recog nized, but the risks associated with the initiation of antiarrhythmic therapy in patients hospitalized for atrial fibrillation are poorly de fined. Objective: To determine the incidence, time course, and predict ors of adverse cardiac events that require intervention during initiat ion of antiarrhythmic drug therapy for atrial fibrillation. Design: Re trospective chart review. Setting: University hospital. Participants: 417 consecutive patients who underwent a total of 597 drug trials duri ng a total of 550 hospitalizations for atrial fibrillation. Interventi on: Initiation of therapy with antiarrhythmic drugs: procainamide (189 trials), quinidine (179 trials), disopyramide (20 trials), propafenon e (110 trials), flecainide (2 trials), sotalol (72 trials), and amioda rone (25 trials). Electrical conversion was performed during 247 trial s. Measurements: Incidence of adverse events and daily hazard rate wer e measured. Logistic regression was done to identify risk factors. Res ults: During the 597 drug trials, 80 (13.4%) cardiac adverse events oc curred in 73 patients. The risk was greatest during the first 24 hours of therapy. Bradyarrhythmias were the most common adverse event, occu rring in 47 trials (7.9%); prolongation of the QT interval warranting discontinuation of drug therapy (9 trials; 1.5%) and ventricular arrhy thmias (8 trials; 1.3%) were less frequent. In multivariate analysis, previous myocardial infarction was associated with increased risk (odd s ratio, 1.90 [95% CI, 1.05 to 3.43]) and the association between olde r age and increased risk (odds ratio, 1.29 per decade [CI, 0.97 to 1.7 2]) was of borderline statistical significance. Conclusions: A signifi cant risk for cardiac adverse events exists during initiation of antia rrhythmic therapy in patients hospitalized for atrial fibrillation. Ob servation with electrocardiographic monitoring seems advisable for 24 to 48 hours during initiation of antiarrhythmic therapy, particularly for elderly patients and patients who have previously had myocardial i nfarction.