title: Open-chest epicardial "surgical" defibrillation: biphasic versus monophasic waveform shocks.
abstract: The aim of the study was to compare biphasic versus monophasic shocks for open-chest epicardial defibrillation. Transthoracic biphasic waveform shocks require less energy to terminate ventricular fibrillation compared to monophasic waveform shocks. However, if biphasic shocks are effective for open-chest epicardial ("surgical") defibrillation has not been established. Twenty-eight anesthetized adult swine (15-25 kg) underwent a midline sternotomy. Ventricular fibrillation was electrically induced. After 15 seconds of ventricular fibrillation, each pig in group 1 (n = 16) randomly received damped sinusoidal monophasic epicardial shocks and truncated exponential biphasic epicardial shocks from large (44.2 cm2) paddle electrodes at eight energy levels (2-50 J). Pigs in group 2 (n = 12) received monophasic and truncated exponential biphasic shocks from small (15.9 cm2) paddle electrodes. In group 1 (large paddle electrodes), the overall percent shock success rose from 15 +/- 9% at 2 J to 97 +/- 3% at 50 J. In this group there was no significant difference in percent of shock success between damped sinusoidal monophasic and biphasic waveform shocks. In group 2 (small paddle electrodes), biphasic shocks yielded a significantly higher percent of shock success than monophasic shocks at mid-energy levels from 7 to 20 J (all P < 0.01). With small surgical paddle electrodes, biphasic waveform shocks demonstrated a significantly higher percent of shock success rate compared to monophasic waveform shocks. With large paddle electrodes, the two waveforms were equally effective.
authors.affiliation: Cardiovascular Center, College of Medicine, University of Iowa, Iowa City, Iowa, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhang
authors.forename: Loyd R
authors.initials: LR
authors.lastname: Davies
authors.forename: William J
authors.initials: WJ
authors.lastname: Coddington
authors.forename: M Bridget
authors.initials: MB
authors.lastname: Zimmerman
authors.forename: Scott
authors.initials: S
authors.lastname: Wuthrich
authors.forename: Janice L
authors.initials: JL
authors.lastname: Jones
authors.forename: Richard E
authors.initials: RE
authors.lastname: Kerber
mesh_terms: D000818:Animals; D004554:Electric Countershock; D017097:Electric Impedance; D004566:Electrodes; D011897:Random Allocation; D013552:Swine; D014693:Ventricular Fibrillation / Q000628:therapy*