Document Detail

Transmembrane voltage changes produced by real and virtual electrodes during monophasic defibrillation shock delivered by an implantable electrode.
MedLine Citation:
PMID:  9300301     Owner:  NLM     Status:  MEDLINE    
INTRODUCTION: Epicardial point stimulation produces nonuniform changes in the transmembrane voltage of surrounding cells with simultaneous occurrence of areas of transient positive and negative polarization. This is the phenomenon of virtual electrode. We sought to characterize the responses of epicardial ventricular tissue to the application of monophasic electric shocks from an internal transvenous implantable cardioverter defibrillator (ICD) lead. METHODS AND RESULTS: Langendorff-perfused rabbit hearts (n = 12) were stained with di-4-ANEPPS. A 9-mm-long distal electrode was placed in the right ventricle. A 6-cm proximal electrode was positioned horizontally 3 cm posteriorly and 1 cm superiorly with respect to the heart. Monophasic anodal and cathodal pulses were produced by discharging a 150-microF capacitor. Shocks were applied either during the plateau phase of an action potential (AP) or during ventricular fibrillation. Leading-edge voltage of the pulse was 50 to 150 V, and the pulse duration was 10 msec. Transmembrane voltage was optically recorded during application of the shock, simultaneously from 256 sites on a 11 x 11 mm area of the anterior right ventricular epicardium directly transmural to the distal electrode. The shock effect was evaluated by determining the difference between the AP affected by the shock and the normal AP. During cathodal stimulation an area of depolarization near the electrode was observed, surrounded by areas of hyperpolarization. The amplitude of polarization gradually decreased in areas far from the electrode. Inverting shock polarity reversed this effect. CONCLUSION: ICD monophasic defibrillation shocks create large dynamically interacting areas of both negative and positive polarization.
I R Efimov; Y N Cheng; M Biermann; D R Van Wagoner; T N Mazgalev; P J Tchou
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Journal of cardiovascular electrophysiology     Volume:  8     ISSN:  1045-3873     ISO Abbreviation:  J. Cardiovasc. Electrophysiol.     Publication Date:  1997 Sep 
Date Detail:
Created Date:  1997-11-04     Completed Date:  1997-11-04     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9010756     Medline TA:  J Cardiovasc Electrophysiol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  1031-45     Citation Subset:  IM    
Department of Cardiology, Cleveland Clinic Foundation, OH 44195, USA.
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MeSH Terms
Action Potentials
Cardiac Pacing, Artificial / methods
Defibrillators, Implantable*
Electric Countershock* / instrumentation,  methods
Electrodes, Implanted
Image Interpretation, Computer-Assisted*
Models, Cardiovascular
Signal Processing, Computer-Assisted
Ventricular Fibrillation / physiopathology

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