Optimal initial energy for biphasic shock cardioversion of atrial fibrillation

The optimal initial energy for transthoracic cardioversion (TCV) of atrial fibrillation (AF) using biphasic shock (BS) is unknown. Patients required TCV for AF were recruited. BS was used in all patients. A step-up protocol starting with 30J, with subsequent increments to 50, 100, 150 and 200J was used. 27 patients (16M and 11F, mean age 63.0+/-13.7 years) were recruited. 13 had persistent AF and 14 had recent onset AF, of which 11 occurred during cardiac procedures including cardiac electrophysiology studies, radiofrequency catheter ablation, percutaneous coronary intervention and cardiac pacing. 96.3%(26/27) were successfully cardioverted. 92.3%(24/26) were successfully cardioverted with 100J or less. In patients with any one of the unfavourable factors including persistent AF of duration >48 hours, left atrial size >5.0cm,left ventricular ejection fraction <50% or body weight >85kg, 86.7%(13/15) were cardioverted with 100J or less. With none of the unfavourable factors, 81.8%(9/11) were cardioverted with 50J or less.