Marked Reduction in Internal Atrial Defibrillation Thresholds With Dual-Current Pathways and Sequential Shocks in Humans

Abstract

Background —This study tested the ability of sequential shocks delivered through dual-current pathways to lower the atrial defibrillation threshold (ADFT) compared with a biphasic shock through a standard single-current pathway. Methods and Results —Electrodes were positioned in the right atrial appendage (RA), left subclavian vein (LSV), proximal coronary sinus (CSos), and distal coronary sinus (DCS) in 14 patients with chronic atrial fibrillation (170±185 days). Using a step-up protocol, we compared ADFTs for a single-current pathway (RA→DCS) that used a single 7.5/2.5-ms biphasic shock from a 150-μF capacitor with those for a dual-current pathway system (RA→DCS followed by CSos→LSV) using sequential 7.5/2.5-ms biphasic shocks with capacitor discharge waveforms for 150-μF and 600-μF capacitors. Both dual-current pathway configurations (2.0±0.4 J for 150-μF capacitance, 2.4±0.5 J for 600-μF capacitance) had a significantly lower ADFT than the single-current pathway (5.1±1.8 J). Whereas the dual-current pathway with 150-μF capacitor shocks had a significantly lower energy threshold, there was no statistical difference in terms of leading-edge voltage compared with the dual-current pathway with 600-μF capacitance shocks. There were no ventricular arrhythmias induced with appropriately synchronized shocks. Conclusions —For internal atrial defibrillation in humans, sequential biphasic waveforms delivered over dual-current pathways resulted in a markedly reduced (>50% reduction) ADFT compared with a single shock over a single-current pathway.