Must antidysrhythmic agents be given to all patients with new-onset atrial fibrillation?

We investigated the spontaneous conversion rate of new-onset atrial fibrillation (AF) in emergency department patients and the recurrence rate of AF during a 1 month follow-up period. Sixty-six consecutive hemodynamically stable patients presenting to a university hospital emergency department with new-onset atrial fibrillation (less than 72 hours duration) comprised the study population. Patients were initially monitored for 8 hours and observed for spontaneous conversion of AF to sinus rhythm. If conversion did not occur in the first 8 hours, an oral loading dose (600 mg) of propafenone was given, and patients were observed for an additional 8 hours. All patients were reevaluated at 24 hours and at 1 month. The spontaneous conversion rate in patients presenting within 6 hours of AF onset during the initial 8-hour observation period was 71%. The spontaneous conversion rate for all patients during the initial observation period was 53%. The conversion rates between patients presenting "early" (less than 6 hours) and "late" (7-72 hours) were significantly different (P < 0.001). Many patients with new-onset AF, especially those with atrial fibrillation duration less than 6 hours, may need observation only, rather than immediate intervention, to treat their dysrhythmia.