Biphasic shocks for AF and Atrial flutter

Based on a study of 453 consecutive patients undergoing their first transthoracic electrical cardioversion for atrial tachyarrhythmias, recommendations were developed to aim at delivering the lowest possible total cumulative energy with ≤2 consecutive shocks using the specific truncated exponential biphasic waveform incorporated in Medtronic Physio-Control devices: they recommend an initial energy setting of 50 J in patients with atrial flutter or atrial tachycardia, of 100 J in patients with atrial fibrillation (AF) of 2 or less days in duration, and of 150 J with AF of more than 2 days in duration. If the initial shock fails to restore sinus rhythm, a rescue shock of 250 J for AFL/AT or of 360 J for AF should be applied to secure the highest possible probability of successful cardioversion for each patient.
Optimization of initial energy for cardioversion of atrial tachyarrhythmias with biphasic shocks
Am J Emerg Med. 2010 Feb;28(2):159-65