| Intramural virtual electrodes in ventricular wall: effects on epicardial polarizations. | |
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MedLine Citation:
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PMID: 15117837 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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BACKGROUND: Intramural virtual electrodes (IVEs) are believed to play an important role in defibrillation, but their existence in intact myocardium remains unproven. Here, IVEs were detected by use of optical recordings of shock-induced transmembrane potential (V(m)) changes (DeltaV(m)) measured from the intact epicardial heart surface. METHODS AND RESULTS: To detect IVEs, isolated porcine left ventricles were sequentially stained with a V(m)-sensitive dye by 2 methods: (1) surface staining (SS) and (2) global staining (GS) via coronary perfusion. Shocks (2 to 50 V/cm) were applied across the ventricular wall in an epicardial-to-endocardial direction during the action potential plateau via transparent mesh electrodes, and shock-induced DeltaV(m) were measured optically from the same epicardial locations after SS and GS. Optical recordings revealed significant differences between DeltaV(m) of 2 types that became more prominent with increasing shock strength: (1) for weak shocks, SS-DeltaV(m) were larger and faster than GS-DeltaV(m); (2) for intermediate shocks, cathodal GS-DeltaV(m) became multiphasic, whereas SS-DeltaV(m) remained monophasic; and (3) for strong shocks, cathodal GS-DeltaV(m) became uniformly negative, whereas SS-DeltaV(m) typically remained positive. The radical differences in the shape and polarity of SS and GS polarizations can be explained by the contribution of subepicardial IVEs to optical signals. Histological examination revealed a dense network of collagen septa in the subepicardium, which could form the IVE substrate. CONCLUSIONS: Intramural virtual electrodes are reflected in optical measurements of shock-induced DeltaV(m) on the intact epicardial surface. These IVEs could be a result of microscopic resistive discontinuities formed by collagen septa. |
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Authors:
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Oleg F Sharifov; Vladimir G Fast |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, P.H.S. Date: 2004-04-26 |
Journal Detail:
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Title: Circulation Volume: 109 ISSN: 1524-4539 ISO Abbreviation: Circulation Publication Date: 2004 May |
Date Detail:
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Created Date: 2004-05-18 Completed Date: 2004-10-08 Revised Date: 2008-11-21 |
Medline Journal Info:
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Nlm Unique ID: 0147763 Medline TA: Circulation Country: United States |
Other Details:
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Languages: eng Pagination: 2349-56 Citation Subset: AIM; IM |
Affiliation:
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Department of Biomedical Engineering, University of Alabama at Birmingham, AL 35294, USA. |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Action Potentials Animals Azo Compounds / analysis Collagen / analysis Coloring Agents / analysis Electric Stimulation Electrodes* Equipment Design Fluorescent Dyes / analysis Heart Ventricles / chemistry Membrane Potentials* Microscopy, Fluorescence Pericardium / physiology* Pyridinium Compounds / analysis Staining and Labeling Swine Ventricular Function* |
| Grant Support | |
ID/Acronym/Agency:
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HL-67748/HL/NHLBI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Azo Compounds; 0/Coloring Agents; 0/Fluorescent Dyes; 0/Pyridinium Compounds; 25188-41-4/C.I. direct red 80; 9007-34-5/Collagen; 90134-00-2/1-(3-sulfonatopropyl)-4-(beta)(2-(di-n-butylamino)-6-naphthylvinyl)pyridinium betaine |
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