Frequency and Outcomes of Postrandomization Atrial Tachyarrhythmias in the Resynchronization/Defibrillation in Ambulatory Heart Failure Trial.

<bold>Background: </bold>Whether adding cardiac resynchronization therapy (CRT-D) to an implanted cardioverter-defibrillator alters the risk of atrial fibrillation or other atrial tachyarrhythmias (AF/AT), or if postimplantation AF/AT modulate the benefits of CRT-D, remain unknown.<bold>Methods and Results: </bold>We studied 972 Resynchronization/Defibrillation in Ambulatory Heart Failure Trial (RAFT) participants without permanent AF, who were randomized to CRT-D (n=495) versus nonresynchronization defibrillator (implanted cardioverter-defibrillator; n=477) within the predefined stratum eligible for an atrial lead. Occurrence of postrandomization AF/AT was prospectively assessed, and Cox models were used to test the independent association between the postrandomization AF/AT and the RAFT primary composite outcome of all-cause mortality or hospitalization for heart failure. Over 41 (±19) months, postrandomization AF/AT occurred in 216 (45.3%) patients randomized to implanted cardioverter-defibrillator and 249 (50.3%) randomized to CRT-D. After adjusting for competing risk of death, randomization to CRT-D increased risk of postrandomization AF/AT (hazard ratio, 1.20; 95% confidence interval, 1.00-1.42; P=0.045). Postrandomization AF/AT, which remained paroxysmal in 69.5%, did not reduce biventricular pacing percentage. In adjusted models, postrandomization AF/AT was not associated with the primary outcome (hazard ratio, 1.04; 95% confidence interval, 0.84-1.30). However, AF/AT was associated with a borderline decreased risk of mortality (hazard ratio, 0.75; 95% confidence interval, 0.58-1.00) but increased risk of heart failure hospitalization (hazard ratio, 1.43; 95% confidence interval, 1.08-1.90).<bold>Conclusions: </bold>In RAFT, nearly half of the patients developed postrandomization AF/AT, and those randomized to CRT-D had borderline significant higher risk. Postrandomization AF/AT was associated with risk of heart failure hospitalization, but not with the primary composite outcome.<bold>Clinical Trial Registration: </bold>URL: http://www.clinicaltrials.gov. Unique identifier: NCT00251251. [ABSTRACT FROM AUTHOR]