Randomized comparison of a 90 uF capacitor three-electrode defibrillation system with a 125 uF two-electrode defibrillation system

Introduction: A variety of factors, including the number of defibrillation electrodes and shocking capacitance, may influence the defibrillation effic acy of an implantable defibrillator system. Therefore, the purpose of this study was to compare the defibrillation energy requirement using a 125 uF t wo-electrode defibrillation system and a 90 uF three-electrode defibrillati on system. Methods and Results: The defibrillation energy requirements measured with b oth systems were compared in 26 consecutive patients. The two-electrode sys tem used a single transvenous lead with two defibrillation coils in conjunc tion with a biphasic waveform from a 125 uF capacitor. The three-electrode system used the same transvenous lead, utilized a pectoral implantable defi brillator generator shell as a third electrode, and delivered the identical biphasic waveform from a 90 uF capacitor. The two-electrode system was ass ociated with a higher defibrillation energy requirement (10.8 +/- 5.5 J) th an was the three-electrode system (8.9 +/- 6.7 J, p < 0.05), however, the l eading edge voltage was not significantly different between systems (361 +/ - 103 V vs. 397 +/- 123 V, P = 0.07). The two-electrode system also had a h igher shocking resistance (49.0 +/- 9.0 ohms vs. 41.4 +/- 7.3 ohms, p < 0.0 01) and a lower peak current (7.7 +/- 2.6 A vs. 10.1 +/- 3.7 A, p < 0.001) than the three-electrode system, Conclusions: A three-electrode defibrillation system that utilizes a dual c oil transvenous lead and a subcutaneous pectoral electrode with lower capac itance is associated with a lower defibrillation energy requirement than is a dual coil defibrillation system with higher capacitance. This finding su ggests that the utilization of a pectoral generator as a defibrillation ele ctrode in conjunction with smaller capacitors is a more effective defibrill ation system and may allow for additional miniaturization of implantable de fibrillators.