Acute atrial fibrillation and flutter treated electively: rationale and design of the randomized controlled AFFELECT trial.

Aims: Cardioversion (CV) is commonly used in the emergency department (ED) to treat recent-onset atrial fibrillation (AF) or flutter (AFL). Design: The AFFELECT trial (NCT04267159) is an investigator-initiated, prospective, unblinded randomized controlled non-inferiority trial comparing experimental delayed rhythm control (elective CV performed within 5-9 days after the index visit) to standard acute rhythm control (CV performed in ED) in patients with recent-onset (duration <48 h) symptomatic AF/AFL suitable for rhythm control. A total of 500 patients are randomized in a 2:3 ratio to the acute and delayed groups, respectively, accounting for a possible one-third unplanned early CV rate in the delayed group due to higher symptom burden. Unplanned early CV means that patients with unbearable symptoms are offered the option for an earlier CV (before the 5-9 days target timeline) if needed. Patients randomized to delayed group are discharged immediately after adequate heart rate control (heart rate <110 bpm) and anticoagulation and are scheduled an appointment for delayed CV at a cardiology outpatient clinic (in transoesophageal echocardiography guidance if required). Patients randomized to acute CV undergo cardioversion in the ED within 48 h of arrhythmia onset and are assigned to a cardiologic outpatient clinic visit also within 5-9 days. The primary end-point is the presence of sinus rhythm on electrocardiogram at 4 weeks after the outpatient clinic visit. Conclusion: The AFFELECT trial tests whether delayed management of recent-onset AF/AFL is a non-inferior alternative to acute CV, aiming to reduce ED burden, number of needed CVs, and redirect care to specialized arrhythmia units.