Randomised comparison of electrode positions for cardioversion of atrial fibrillation

Objective-To compare the relative efficacy of anteroanterior v anteroposter ior electrode pad positions for external cardioversion of atrial fibrillati on. Design-Prospective randomised trial. Setting-Tertiary referral cardiology centre in the United Kingdom. Patients-90 patients undergoing elective cardioversion for atrial fibrillat ion. Interventions-Cardioversion was attempted with self adhesive electrode pads with an area of 106 cm(2) placed either in the anteroanterior (AA) or ante roposterior (AP) positions. Initial shock was 100 J which, if unsuccessful, was followed by 200 J, 300 J, and 360 J if required. Peak current and tran sthoracic impedance were measured. Main outcome measures-Cardioversion success rate and energy requirements. Results-Cardioversion was successful in 81% of the patients (73/90). There was no statistically significant difference in the cardioversion success ra te (AA 84%, 38/45 patients; AP 78%, 35/45 patients; p = 0.42) or mean (SD) energy requirement for all patients (AA 223 (96.1) J; AP 232 (110) J) or fo r patients who were successfully cardioverted (AA 197.9 (82.4) J; AP 195.4 (97.2) J; p = 0.9) between the two pad positions. The mean transthoracic im pedance (TTI) for the first shock (AA 77.5 (18.4) ohms; AP 73.7 (18.7) ohms ; p = 0.34) was not significantly different between the two groups. TTI cor related significantly with body mass index, percentage body fat, and chest AP diameter. There was a progressive decrease in TTI with serial shocks. Wh ile aetiology and TTI were the two independent significant predictive facto rs for energy requirement, duration of atrial fibrillation was the only ind ependent predictor of cardioversion success in a multivariate analysis. Conclusions-Electrode pad position is not a determinant of cardioversion su ccess rate or energy requirement.