Cardioversion of atrial fibrillation with ibutilide: When is it most effective?

Background: Atrial fibrillation (AF) is found in 1% of persons above the age of 60 years. More than 5% of the population older than 69 years and about 14% of octogenarians are at risk for this arrhythmia. It is estimated that 1.5 to 3 million persons in the United States alone suffer from AF. The public health implications and attendant morbidity are a significant drain on our health care system. Hypothesis: The purpose of this study was to determine the clinical and echocardiographic predictors of success in converting AF of ≥ 24 h duration. Methods: Demographic and clinical and echocardiographic parameters of 101 patients with recent onset AF (>24 h) who received ibutilide were studied. Results: Of 101 patients, 56 (55%) converted to sinus rhythm. Age, gender, hypertension, diabetes mellitus, left ventricular ejection fraction (≤35%), congestive heart failure, and previous medication for rate control had no significant effect on the conversion rate. Conversion rate was only 30% (9/30 patients) in the presence of an enlarged left atrium (LA ≥ 5 cm) and 37.7% (23/61 patients) in the presence of mitral valve disease (MVD), whereas the conversion rate was 82.5% (33/40 patients) in the absence of MVD and 85% (29/34 patients) in the absence of both enlarged LA and MVD (p =<0.001). Patients with coronary artery disease (CAD) also exhibited a significantly greater response to ibutilide than patients without CAD (77 vs. 46%, p-value 0.005). Conclusion: As a therapy for cardioversion of AF, ibutilide is most effective in a selected subgroup patients, such as in patients with CAD and in patients without MVD and/or markedly enlarged left atrium.