INTERNAL CARDIOVERSION OF ATRIAL-FIBRILLATION - MARKED REDUCTION IN DEFIBRILLATION THRESHOLD WITH DUAL CURRENT PATHWAYS

Background The ultimate acceptance of a fully automatic atrial defibri llator will depend on the reduction of pain to acceptable levels, requ iring a marked decrease in defibrillation thresholds. The purpose of t his study was to determine whether atrial defibrillation thresholds ca n be reduced by sequential shocks delivered through two current pathwa ys. Methods and Results Sustained atrial fibrillation was induced with rapid atrial pacing in 12 adult sheep. Defibrillation electrodes were positioned in the right atrial appendage (RAap), distal coronary sinu s (DCS), proximal coronary sinus (CSos), main/left pulmonary artery ju nction (PA), and right ventricular apex (RV). Single-capacitor biphasi c waveforms (3/1 ms) were delivered through combinations of these elec trodes. Probability-of-success curves were determined for single shock s with a single current pathway and sequential shocks with either sing le-or dual current pathways. The ED50 for delivered energy for the dua l current pathway RAap to DCS then CSos to PA was 0.36+/-0.13 J, which was significantly lower than the ED50 of the standard single current pathway RAap to DCS (1.31+/-0.3 J) and was significantly lower than al l other configurations tested. Conclusions Internal atrial defibrillat ion thresholds can be markedly reduced with two sequential biphasic sh ocks delivered over two current pathways compared with the standard si ngle shock delivered over a single current pathway or with sequential shocks delivered over a single current pathway.