title: Defibrillation efficacy using two low-profile endocardial electrodes.
abstract: The hypothesis that improved energy delivery and defibrillation efficacy can be achieved by using two widely separated endocardial electrodes and a cutaneous patch electrode was explored by positioning two 6.5 F electrodes (NuMed, Hopkinton, New York) with 5 cm platinum-iridium coils in the right ventricular apex (RVA) and the right ventricular outflow (RVO) in eight dogs. In another 12 dogs, an additional electrode was positioned in the RVA. A cutaneous patch (P) was placed at the cardiac apex. Biphasic pulses were delivered, the first pulse (6 ms) positive, the second negative (2 ms). The leading edge of the second was equal to the trailing edge of the first. RVO-/P+ and RVA-RVO-/P+ were compared with RVA-/P+ at a constant voltage setting required to achieve a 60% probability of success (P60) for RVA-/P+. At a constant voltage output, the probability of success for RVA-RVO-/P+ was significantly higher (81%) than RVO-/P+ (60%) or RVA-/P+ (67%) (p less than 0.03). The current delivered was greater for RVA-RVO-/P+ (9.9 +/- 2.3 amps) than for either RVA-RVO-/P+ (8.7 +/- 1.9 amps) or RVO-/P+ (9.0 +/- 2.0 amps) (p less than 0.0001). Similarly, the impedance was significantly lower for RVA-RVO-/P+ (66 +/- 12 omega) than for RVA-/P+ (75 +/- 12 omega) and RVO-/P+ (72 +/- 9.6 omega) (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, University of Louisville, School of Medicine, KY 40292.
authors.forename: I
authors.initials: I
authors.lastname: Singer
authors.forename: C
authors.initials: C
authors.lastname: Maldonado
authors.forename: F
authors.initials: F
authors.lastname: Vance
authors.forename: P
authors.initials: P
authors.lastname: Simpson
authors.forename: J
authors.initials: J
authors.lastname: Kupersmith
mesh_terms: D000818:Animals; D004285:Dogs; D004554:Electric Countershock / Q000295:instrumentation*; D004567:Electrodes, Implanted; D004594:Electrophysiology; D006321:Heart / Q000502:physiology