Document Detail


Optical recordings in the rabbit heart show that defibrillation strength shocks prolong the duration of depolarization and the refractory period.
MedLine Citation:
PMID:  1873877     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
The present data were obtained using the technique of optical recording with the voltage-sensitive dye WW781. This technique, unlike electrical methods, was able to provide uninterrupted recordings free of artifacts during defibrillation shocks. Optical recordings were made from sites on the ventricular epicardium of perfused rabbit hearts during electrical pacing. Continuous recordings of the electrophysiological responses of an intact heart to defibrillation threshold-strength shocks were made. It was shown that these shocks were able to stimulate normal-appearing action potentials in nonrefractory myocardium. A new and unexpected finding was that defibrillation threshold-strength shocks were also able to evoke a sustained, depolarizing response from myocardium already undergoing an action potential. This prolonged the time that the myocardium remained in the depolarized state. Prolongation of the depolarized state was accompanied by an equal prolongation of the refractory period. There was no indication that this depolarizing shock response was due to damage of the myocardium by the shock, to heterogeneous electrical responses in the optical recording area, or to the methods used in this study. It is hypothesized that these shocks were able to elicit a new action potential in already depolarized myocardium by hyperpolarizing portions of the myocardium's cellular membranes and, in so doing, to reactivate the fast sodium current. This effect, if prevalent in a fibrillating ventricle, could play a role in the defribillation process by effectively resynchronizing electrical activity.
Authors:
S M Dillon
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Publication Detail:
Type:  Comparative Study; In Vitro; Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Circulation research     Volume:  69     ISSN:  0009-7330     ISO Abbreviation:  Circ. Res.     Publication Date:  1991 Sep 
Date Detail:
Created Date:  1991-09-26     Completed Date:  1991-09-26     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0047103     Medline TA:  Circ Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  842-56     Citation Subset:  IM    
Affiliation:
Department of Pharmacology, College of Physicians and Surgeons, Columbia University, New York, NY 10032.
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MeSH Terms
Descriptor/Qualifier:
Action Potentials
Animals
Cardiac Pacing, Artificial
Coloring Agents / diagnostic use
Electric Countershock*
Electrocardiography
Electrophysiology
Heart / physiology*
Optics and Photonics*
Perfusion
Rabbits
Grant Support
ID/Acronym/Agency:
HL-30557/HL/NHLBI NIH HHS; R01 HL-31393/HL/NHLBI NIH HHS
Chemical
Reg. No./Substance:
0/Coloring Agents

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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