Document Detail


Three distinct directions of intramural activation reveal nonuniform side-to-side electrical coupling of ventricular myocytes.
MedLine Citation:
PMID:  19808500     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
BACKGROUND: The anisotropy of cardiac tissue is a key determinant of 3D electric propagation and the stability of activation wave fronts in the heart. The electric properties of ventricular myocardium are widely assumed to be axially anisotropic, with activation propagating most rapidly in the myofiber direction and at uniform velocity transverse to this. We present new experimental evidence that contradicts this view. METHODS AND RESULTS: For the first time, high-density intramural electric mapping (325 electrodes at approximately 4x4x1-mm spacing) from pig left ventricular tissue was used to reconstruct 3D paced activation surfaces projected directly onto 3D tissue structure imaged throughout the same left ventricular volume. These data from 5 hearts demonstrate that ventricular tissue is electrically orthotropic with 3 distinct propagation directions that coincide with local microstructural axes defined by the laminar arrangement of ventricular myocytes. The maximum conduction velocity of 0.67+/-0.019 ms(-1) was aligned with the myofiber axis. However, transverse to this, the maximum conduction velocity was 0.30+/-0.010 ms(-1), parallel to the myocyte layers and 0.17+/-0.004 ms(-1) normal to them. These orthotropic conduction velocities give rise to preferential activation pathways across the left ventricular free wall that are not captured by structurally detailed computer models, which incorporate axially anisotropic electric properties. CONCLUSIONS: Our findings suggest that current views on uniform side-to-side electric coupling in the heart need to be revised. In particular, nonuniform laminar myocardial architecture and associated electric orthotropy should be included in future models of initiation and maintenance of ventricular arrhythmia.
Authors:
Bryan J Caldwell; Mark L Trew; Gregory B Sands; Darren A Hooks; Ian J LeGrice; Bruce H Smaill
Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-06-18
Journal Detail:
Title:  Circulation. Arrhythmia and electrophysiology     Volume:  2     ISSN:  1941-3084     ISO Abbreviation:  Circ Arrhythm Electrophysiol     Publication Date:  2009 Aug 
Date Detail:
Created Date:  2009-10-07     Completed Date:  2009-10-29     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101474365     Medline TA:  Circ Arrhythm Electrophysiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  433-40     Citation Subset:  IM    
Affiliation:
Auckland Bioengineering Institute, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
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MeSH Terms
Descriptor/Qualifier:
Action Potentials / physiology*
Animals
Anisotropy
Cardiac Pacing, Artificial
Computer Simulation
Electric Conductivity
Heart / physiology*
Heart Ventricles / cytology
Models, Cardiovascular
Myocardium / cytology*
Myocytes, Cardiac / physiology*
Swine
Tachycardia, Ventricular / physiopathology*

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


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