Early or Delayed Cardioversion in Recent-Onset Atrial Fibrillation

BACKGROUND: Patients with recent-onset atrial fibrillationcommonly undergo immediate restoration of sinus rhythmby pharmacologic or electrical cardioversion. However, whether immediate restoration of sinus rhythmis necessary is not known, since atrial fibrillationoften terminates spontaneously. METHODS: In a multicenter, randomized, open-label, noninferiority trial, we randomly assigned patients with hemodynamically stable, recent-onset (<36 hours), symptomatic atrial fibrillationin the emergency department to be treated with a wait-and-see approach (delayed- cardioversiongroup) or early cardioversion. The wait-and-see approach involved initial treatment with rate-control medication only and delayed cardioversionif the atrial fibrillationdid not resolve within 48 hours. The primary end point was the presence of sinus rhythmat 4 weeks. Noninferiority would be shown if the lower limit of the 95% confidence interval for the between-group difference in the primary end point in percentage points was more than -10. RESULTS: The presence of sinus rhythmat 4 weeks occurred in 193 of 212 patients (91%) in the delayed- cardioversiongroup and in 202 of 215 (94%) in the early- cardioversiongroup (between-group difference, -2.9 percentage points; 95% confidence interval [CI], -8.2 to 2.2; P = 0.005 for noninferiority). In the delayed- cardioversiongroup, conversion to sinus rhythmwithin 48 hours occurred spontaneously in 150 of 218 patients (69%) and after delayed cardioversionin 61 patients (28%). In the early- cardioversiongroup, conversion to sinus rhythmoccurred spontaneously before the initiation of cardioversionin 36 of 219 patients (16%) and after cardioversionin 171 patients (78%). Among the patients who completed remote monitoring during 4 weeks of follow-up, a recurrence of atrial fibrillationoccurred in 49 of 164 patients (30%) in the delayed- cardioversiongroup and in 50 of 171 (29%) in the early- cardioversiongroup. Within 4 weeks after randomization, cardiovascular complications occurred in 10 patients and 8 patients, respectively. CONCLUSIONS: In patients presenting to the emergency department with recent-onset, symptomatic atrial fibrillation, a wait-and-see approach was noninferior to early cardioversionin achieving a return to sinus rhythmat 4 weeks. (Funded by the Netherlands Organization for Health Research and Development and others; RACE 7 ACWAS ClinicalTrials.gov number, NCT02248753.).