External cardioversion of atrial fibrillation: role of paddle position on technical efficacy and energy requirements

Aim-To define the effect of defibrillator paddle position on technical succ ess and de shock energy requirements of external cardioversion of atrial fi brillation. Methods-301 patients (mean (SD) age 62 (11) years) with stable atrial fibri llation were randomly assigned to elective external cardioversion using ant erolateral paddle position (ventricular apex-right infraclavicular area; gr oup AL (151 patients)) or anteroposterior paddle position (sternal body-ang le of the left scapula; group AP (150 patients)). A step up protocol was us ed, delivering a 3 J/kg body weight de shock, then a 4 J/kg shock (maximum 360 J), and finally a second 4 J/kg shock using the alternative paddle loca tion. Results-The two groups were comparable for the all clinical variables evalu ated. The cumulative percentage of patients successfully converted to sinus rhythm was 58% in group AL and 67% in group AP with low energy de shock (N S); this rose to 76% in group AL and to 87% in group AP with high energy de shock (p = 0.013). Thirty seven patients in group AL and 19 in group AP ex perienced de shock with the alternative paddle position; atrial fibrillatio n persisted in 10/37 in group AL and in 10/19 in group AP. Mean de shock en ergy requirements were lower for group AP patients than for group AL patien ts, at 383 (235) v 451 (287) J, p = 0.025. Arrhythmia duration was the only factor that affected the technical success of external cardioversion (succ essful: 281 patients, 80 (109) days; unsuccessful: 20 patients, 193 (229) d ays; p < 0.0001). The success rate was lower if atrial fibrillation persist ed for > 6 months: 29 of 37 (78%) v 252 of 264 (95%); p = 0.0001. Conclusions-An anteroposterior defibrillator paddle position is superior to an anterolateral location with regard to technical success in external car dioversion of stable atrial fibrillation, and permits lower de shock energy requirements. Arrhythmia duration is the only clinical variable that can L imit the restoration of sinus rhythm.