Catheter Ablation for Atrial Fibrillation with Heart Failure

To the Editor: In the Catheter Ablation versus Standard Conventional Therapy in Patients with Left Ventricular Dysfunction and Atrial Fibrillation (CASTLE-AF) trial, Marrouche et al. (Feb. 1 issue)1 found a 46% lower rate of death from any cause among patients who were randomly assigned to catheter ablation than among those who were assigned to medical therapy. One concern in interpreting these results is that the patients underwent randomization before the run-in phase.2,3 During the run-in phase, 18 patients in the ablation group and 9 in the medical-therapy group were excluded. This process may have affected patient assignments and subverted randomization. Consequent imbalances that may have had an effect on the primary end point include a significantly higher proportion of patients in the medical-therapy group than in the ablation group who had a diagnosis of ischemic cardiomyopathy, who had diabetes mellitus, and who were receiving digoxin at baseline. Ischemic heart disease, diabetes, and a high serum digoxin concentration have all been associated with increased mortality, and no data regarding digoxin dosing or monitoring were reported in the article.4,5 Although ischemic heart disease and digoxin therapy are known confounding factors, the possibility of imbalances of unknown confounding factors cannot be ruled out.