Efficacy and safety of monophasic and biphasic waveform shocks using a braided endocardial defibrillation lead system

Abstract

Endocardial lead systems for implantable cardioverter-defibrillators utilize large (12F) rigid catheters with spring defibrillation electrodes, and lead system failure has been observed during long-term implant. We evaluated a novel flexible 8F braided electrode catheter for pacing and defibrillation in canine experiments. Active fixation and pacing were accomplished using a screw-in distal electrode, and defibrillation pulses were delivered through a braided electrode. Two braided electrode,catheters were positioned in the right ventricular apex (6 cm 2) and in the superior vena cava-right atrial junction (5 cm 2), respectively. An elliptical 13 cm 2 surface area pathch electrode was positioned along the left lateral cardiac border. Ventricular fibrillation (VF) was induced and monophasic and asymmetric biphasic shocks (leading voltages 260 to 1000 V) were delivered via dual and triple electrode configurations in each animal using a prospective randomized crossover study design. Mean right ventricular pacing threshold was 0.5 ± 0.2 mA, with a mean electrogram amplitude of 11.1 ± 2.8 mV during sinus rhythm prior to fibrillation and defibrillation. Two hundred seven VF inductions (mean 30 ± 4 per animal) were analyzed. The mean defibrillation threshold could be reduced to 8.0 ± 3.2 joules with biphasic shocks from 12.9 ± 5.1 joules obtained for monophasic shocks using a dual electrode system ( p < 0.004). Mean shock leading voltage was correspondingly reduced to 488 ± 100 V from 691 ± 154 V ( p < 0.0006). The mean defibrillation threshold could be reduced to 10.7 ± 3.4 joules with biphasic shocks from 14.8 ± 4.9 joules for monophasic shocks using a triple electrode system (right ventricle[−]/patch and right atrium[+]; p < 0.02). Mean shock leading voltage was correspondingly reduced to 543 ± 101 V from 717 ± 114 V ( p < 0.003). Pacing thresholds were unchanged after defibrillation ( p > 0.05). We conclude that successful pacing and defibrillation is feasible with a small-caliber braided electrode catheter. Percutaneous insertion of one or two catheters permits use with dual and triple electrode configurations. Asymmetric biphasic waveform pulses reduce endocardial defibrillation threshold with this catheter electrode system.