Effect of cardiac resynchronization on the incidence of atrial fibrillation in patients with severe heart failure.

BACKGROUND Atrial fibrillation/flutter (AF) and heart failure often coexist; however, the effect of cardiac resynchronization therapy (CRT) on the incidence of AF and on the outcome of patients with new-onset AF remains undefined. METHODS AND RESULTS In the CArdiac REsynchronisation in Heart Failure (CARE-HF) trial, 813 patients with moderate or severe heart failure were randomly assigned to pharmacological therapy alone or with the addition of CRT. The incidence of AF was assessed by adverse event reporting and by ECGs during follow-up, and the impact of new-onset AF on the outcome and efficacy of CRT was evaluated. By the end of the study (mean duration of follow-up 29.4 months), AF had been documented in 66 patients in the CRT group compared with 58 who received medical therapy only (16.1% versus 14.4%; hazard ratio 1.05; 95% confidence interval, 0.73 to 1.50; P=0.79). There was no difference in the time until first onset of AF between groups. Mortality was higher in patients who developed AF, but AF was not a predictor in the multivariable model (hazard ratio 1.17; 95% confidence interval, 0.82 to 1.67; P=0.37). In patients with new-onset AF, CRT significantly reduced the risk for all-cause mortality and all other predefined end points and improved ejection fraction and symptoms (no interaction between AF and CRT; all P>0.2). CONCLUSIONS Although CRT did not reduce the incidence of AF, CRT improved the outcome regardless of whether AF developed.