title: Biphasic and monophasic transthoracic defibrillation in pigs with acute left ventricular dysfunction.
abstract: OBJECTIVE
  Our purpose was to compare biphasic versus monophasic shock success for VF termination in a porcine model of acute left ventricular (LV) dysfunction.
  
  
  BACKGROUND
  For the termination of ventricular fibrillation (VF), transthoracic biphasic waveform shocks achieve higher success rates than monophasic shocks. However, the effectiveness of biphasic versus monophasic defibrillation in a setting of left ventricular dysfunction has not been reported.
  
  
  METHODS
  In 23 open-chest adult swine (15-25 kg), LV dysfunction [> or =25% decline in cardiac output (CO)] was induced by continuous inhalation of halothane (1-1.75%). Each pig randomly received transthoracic biphasic and monophasic shocks at three energy levels (30, 50 and 100 J) in two conditions: baseline and LV dysfunction. Halothane effect on left ventricular size and contraction was measured by echocardiography in three additional swine.
  
  
  RESULTS
  With halothane, pigs demonstrated a decline in CO (baseline 4.16+/-0.19, halothane 2.72+/-0.19 l/min, P<0.01), mean arterial pressure (baseline 107.2+/-3.5, halothane 80.1+/-3.4 mmHg, P<0.01) and increased left ventricular end-diastolic pressure (baseline 6.4+/-0.9, halothane 12.7+/-0.8 mmHg, P<0.01). LV diameters increased and fractional shortening fell. During baseline, biphasic shocks achieved significantly greater success (termination of VF) compared to monophasic waveforms (100 J: biphasic 83.3+/-9.5 versus monophasic 38.9+/-9.5%, P<0.01; 50 J: biphasic 67.1+/-8.8 versus monophasic 11.8+/-5.7%, P<0.01; 30 J: biphasic: 31.9+/-6.4 versus monophasic 0+/-0%, P<0.01). The superiority of the biphasic waveform to terminate VF was retained during LV dysfunction at all energy levels (100 J: biphasic 78.3+/-7.3 versus monophasic 37.5+/-8.1%, P<0.01; 50 J: biphasic 65.5+/-11.5 versus monophasic 11.7+/-5.9%, P<0.01; 30 J: biphasic: 40.6+/-8.0 versus monophasic 3.1+/-3.1%, P<0.01). Within both waveforms, there were no significant differences in percent shock success at any energy level comparing baseline with LV dysfunction.
  
  
  CONCLUSIONS
  In this porcine model of acute LV dysfunction, biphasic waveform shocks were not only superior to monophasic waveform shocks for termination of VF during baseline, but retained superiority to monophasic waveform shocks when LV dysfunction was present.
authors.affiliation: The Cardiovascular Center, College of Medicine, University of Iowa, Iowa City, IA 52242, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.forename: G
authors.initials: G
authors.lastname: Karlsson
authors.forename: L R
authors.initials: LR
authors.lastname: Davies
authors.forename: W J
authors.initials: WJ
authors.lastname: Coddington
authors.forename: R E
authors.initials: RE
authors.lastname: Kerber
mesh_terms: D000208:Acute Disease; D018685:Anesthetics, Inhalation / Q000009:adverse effects; D000818:Animals; D002302:Cardiac Output / Q000502:physiology; D002307:Cardiography, Impedance; D004195:Disease Models, Animal; D004554:Electric Countershock; D005260:Female; D006221:Halothane / Q000009:adverse effects; D008297:Male; D011897:Random Allocation; D013552:Swine; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000139:chemically induced / Q000503:physiopathology / Q000628:therapy*
chemical_list: D018685:Anesthetics, Inhalation; D006221:Halothane