title: Effect of ventricular shock strength on cardiac hemodynamics.
abstract: BACKGROUND
  The effect of implantable defibrillator shocks on cardiac hemodynamics is poorly understood. The purpose of this study was to test the hypothesis that ventricular defibrillator shocks adversely effect cardiac hemodynamics.
  
  
  RESULTS
  The cardiac index was determined by calculating the mitral valve inflow with transesophogeal Doppler during nonthoracotomy defibrillator implantation in 17 patients. The cardiac index was determined before, and immediately, 1 minute, 2 minutes, and 4 minutes after shocks were delivered during defibrillation energy requirement testing with 27- to 34-, 15-, 10-, 5-, 3-, or 1-J shocks. The cardiac index was also measured at the same time points after 27- to 34-, and 1-J shocks delivered during the baseline rhythm. The cardiac index decreased from 2.30 +/- 0.40 L/min per m2 before a 27- to 34-J shock during defibrillation energy requirement testing to 2.14 +/- 0.45 L/min per m2 immediately afterwards (P = 0.001). This effect persisted for > 4 minutes. An adverse hemodynamic effect of similar magnitude occurred after 15 J (P = 0.003) and 10-J shocks (P = 0.01), but dissipated after 4 minutes and within 2 minutes, respectively. There was a significant correlation between shock strength and the percent change in cardiac index (r = 0.3, P = 0.03). The cardiac index decreased 14% after a 27- to 34-J shock during the baseline rhythm (P < 0.0001). This effect persisted for < 4 minutes. A 1-J shock during the baseline rhythm did not effect the cardiac index.
  
  
  CONCLUSIONS
  Defibrillator shocks > 9 J delivered during the baseline rhythm or during defibrillation energy requirement testing result in a 10% to 15% reduction in cardiac index, whereas smaller energy shocks do not affect cardiac hemodynamics. The duration and extent of the adverse effect are proportional to the shock strength. Shock strength, and not ventricular fibrillation, appears to be most responsible for this effect. Therefore, the detrimental hemodynamic effects of high-energy shocks may be avoided when low-energy defibrillation is used.
authors.affiliation: Department of Internal Medicine, University of Michigan Medical Center, Ann Arbor 48109-0022, USA.
authors.forename: T
authors.initials: T
authors.lastname: Tokano
authors.forename: D
authors.initials: D
authors.lastname: Bach
authors.forename: J
authors.initials: J
authors.lastname: Chang
authors.forename: J
authors.initials: J
authors.lastname: Davis
authors.forename: J J
authors.initials: JJ
authors.lastname: Souza
authors.forename: A
authors.initials: A
authors.lastname: Zivin
authors.forename: B P
authors.initials: BP
authors.lastname: Knight
authors.forename: R
authors.initials: R
authors.lastname: Goyal
authors.forename: K C
authors.initials: KC
authors.lastname: Man
authors.forename: F
authors.initials: F
authors.lastname: Morady
authors.forename: S A
authors.initials: SA
authors.lastname: Strickberger
mesh_terms: D000328:Adult; D000368:Aged; D002302:Cardiac Output / Q000502:physiology; D003326:Coronary Circulation / Q000502:physiology*; D017147:Defibrillators, Implantable; D015150:Echocardiography, Doppler; D017548:Echocardiography, Transesophageal; D004554:Electric Countershock / Q000009:adverse effects*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007432:Intraoperative Period; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000000981:diagnostic imaging / Q000503:physiopathology; D016276:Ventricular Function / Q000502:physiology