title: Regional hyperkalemia increases ventricular defibrillation energy requirements: role of electrical heterogeneity in defibrillation.
abstract: BACKGROUND
  Increased spatial electrical heterogeneity has been associated with impaired defibrillation efficacy. The current study investigated the relationship between electrical heterogeneity and defibrillation efficacy by manipulating spatial electrical heterogeneity.
  
  
  RESULTS
  We increased spatial electrical heterogeneity by infusing potassium chloride (2 to 4 mEq/hour) or placebo in the left anterior descending artery in 13 pentobarbital anesthetized swine. Electrophysiologic measurements at five myocardial sites and defibrillation energy requirement (DER) values were determined at baseline and during regional hyperkalemia (n = 7) or placebo (n = 6). Regional potassium infusion was titrated to a 20% reduction in action potential duration in the perfused region. Regional hyperkalemia increased biphasic DER values by 87% (P = 0.02), whereas infusion of placebo did not alter defibrillation efficacy. Regional hyperkalemia decreased myocardial repolarization and refractoriness in the perfused region by 21% (P < 0.001) and 18% (P = 0.01), respectively. However, regional hyperkalemia increased ventricular fibrillation cycle length (VFCL) by 39% (P = 0.008). Consequently, dispersions of repolarization, refractoriness, and VFCL were significantly increased by 169%, 92%, and 200%, respectively. Regional hyperkalemia also increased ventricular conduction time to the perfused region by 54% (P = 0.006), indicating conduction velocity dispersion, while not affecting local pacing threshold or local voltage gradient.
  
  
  CONCLUSIONS
  Regional hyperkalemia increased DER values. Regional hyperkalemia likely impairs defibrillation by increasing myocardial electrical heterogeneity, which supports the theory that electrical heterogeneity promotes nonuniform propagation of early postshock activations, thereby inhibiting defibrillation.
authors.affiliation: University of Georgia College of Pharmacy, Medical College of Georgia School of Medicine, and Augusta VA Medical Center, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Sims
authors.forename: A W
authors.initials: AW
authors.lastname: Miller
authors.forename: M R
authors.initials: MR
authors.lastname: Ujhelyi
mesh_terms: D000818:Animals; D004554:Electric Countershock; D004560:Electricity; D004594:Electrophysiology; D006329:Heart Conduction System / Q000503:physiopathology; D006947:Hyperkalemia / Q000150:complications* / Q000503:physiopathology; D009994:Osmolar Concentration; D011188:Potassium / Q000097:blood; D012032:Refractory Period, Electrophysiological; D013552:Swine; D014693:Ventricular Fibrillation / Q000150:complications* / Q000503:physiopathology / Q000628:therapy*
chemical_list: D011188:Potassium