title: Electrode system influence on biphasic waveform defibrillation efficacy in humans.
abstract: BACKGROUND
  Several clinical studies have demonstrated a general superiority of biphasic waveform defibrillation compared with monophasic waveform defibrillation using epicardial lead systems. To test the breadth of utility of biphasic waveforms in humans, a prospective, randomized evaluation of defibrillation efficacy of monophasic and single capacitor biphasic waveform pulses was performed for two distinct nonthoracotomy lead systems as well as for an epicardial electrode system in 51 cardiac arrest survivors undergoing automatic defibrillator implantation.
  
  
  RESULTS
  The configurations tested consisted of a right ventricular-left ventricular (RV-LV) epicardial patch-patch system, an RV catheter-chest patch (CP) nonthoracotomy system, and a coronary sinus (CS) catheter-RV catheter nonthoracotomy system. For each configuration, the defibrillation current and voltage waveforms were recorded via a digital oscilloscope to measure defibrillation threshold voltage, current, resistance, and stored energy. Biphasic waveform defibrillation proved more efficient than monophasic waveform defibrillation for the epicardial RV-LV system (4.8 +/- 4.1 versus 6.7 +/- 4.9 J, p = 0.047) and the nonthoracotomy RV-CP system (23.4 +/- 11.1 versus 34.3 +/- 10.4 J, p = 0.0042). Biphasic waveform defibrillation thresholds were not significantly lower than monophasic waveform defibrillation thresholds for the CS-RV nonthoracotomy system (15.6 +/- 7.2 versus 20.0 +/- 11.5 J, p = 0.11). Biphasic waveform defibrillation proved more efficacious than monophasic waveform defibrillation in 13 of 20 patients (65%) with RV-LV epicardial patches, 10 of 15 patients (67%) with an RV-CP nonthoracotomy system, and nine of 16 patients (56%) with an RV-CS nonthoracotomy system.
  
  
  CONCLUSIONS
  Biphasic pulsing was useful with nonthoracotomy lead systems as well as with epicardial lead systems. However, the degree of biphasic waveform defibrillation superiority appeared to be electrode system dependent. Furthermore, for a few individuals, biphasic waveform defibrillation proved less efficient than monophasic waveform defibrillation, regardless of the lead system used.
authors.affiliation: Department of Medicine, University of Washington, Seattle 98195.
authors.forename: G H
authors.initials: GH
authors.lastname: Bardy
authors.forename: C
authors.initials: C
authors.lastname: Troutman
authors.forename: G
authors.initials: G
authors.lastname: Johnson
authors.forename: R
authors.initials: R
authors.lastname: Mehra
authors.forename: J E
authors.initials: JE
authors.lastname: Poole
authors.forename: G L
authors.initials: GL
authors.lastname: Dolack
authors.forename: P J
authors.initials: PJ
authors.lastname: Kudenchuk
authors.forename: D M
authors.initials: DM
authors.lastname: Gartman
mesh_terms: D000328:Adult; D000368:Aged; D009202:Cardiomyopathies / Q000503:physiopathology / Q000628:therapy*; D004056:Differential Threshold; D004554:Electric Countershock / Q000295:instrumentation / Q000379:methods*; D004566:Electrodes; D005260:Female; D006331:Heart Diseases / Q000503:physiopathology / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011897:Random Allocation