Document Detail

Alterations in transmural strains adjacent to ischemic myocardium during acute midcircumflex occlusion.
MedLine Citation:
PMID:  15821645     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: Helically oriented left ventricular fibers assemble into transmural sheets, which are important for wall-thickening mechanics: 15% fiber shortening results in 40% cross-fiber left ventricular wall thickening and a 60% ejection fraction through sheet extension, thickening, and shear. Normal cardiac microstructure and strains are optimized; deviations could result in apoptosis and deleterious matrix remodeling, which degenerates into global cardiomyopathy. We studied alterations in transmural strains adjacent to ischemic myocardium during acute midcircumflex occlusion. METHODS: Nine sheep had radiopaque markers implanted to measure left ventricular systolic fractional area shortening; 3 transmural bead columns were inserted into the midlateral wall for strain analysis. Three-dimensional marker coordinates were obtained with biplane videofluoroscopy before and during 70 seconds of ischemia. Systolic strains were quantified along circumferential, longitudinal, and radial axes (n = 9) and were transformed into fiber-sheet coordinates by using quantitative microstructural measurements (n = 5). RESULTS: A functional border was defined in the midlateral left ventricle; ischemia decreased posterolateral fractional area shortening, and anterolateral fractional area shortening increased. In this demarcation junction, subepicardial end-systolic radial wall thickening decreased (0.16 +/- 0.08 vs 0.11 +/- 0.06) and sheet-normal shear was abolished (0.08 +/- 0.04 vs -0.01 +/- 0.03). Longitudinal shortening decreased in the subepicardium and midwall (-0.05 +/- 0.04 vs +/- -0.01 +/- 0.06), but circumferential-radial shear increased at these depths (0.04 +/- 0.04 vs 0.11 +/- 0.05). Subendocardial fiber stretch occurred during early systole (-0.01 +/- 0.03 vs 0.02 +/- 0.03), and end-systolic fiber-sheet shear increased (0.07 +/- 0.01 vs 0.11 +/- 0.04, all P < .05). CONCLUSIONS: Increased circumferential-radial shear and altered fiber-sheet strains reflect mechanical interactions between ischemic and nonischemic myocardium, which might be important in triggering remodeling processes that evolve into global ischemic cardiomyopathy.
Filiberto Rodriguez; Frank Langer; Katherine B Harrington; Allen Cheng; George T Daughters; John C Criscione; Neil B Ingels; D Craig Miller
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The Journal of thoracic and cardiovascular surgery     Volume:  129     ISSN:  0022-5223     ISO Abbreviation:  J. Thorac. Cardiovasc. Surg.     Publication Date:  2005 Apr 
Date Detail:
Created Date:  2005-04-11     Completed Date:  2005-05-19     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0376343     Medline TA:  J Thorac Cardiovasc Surg     Country:  United States    
Other Details:
Languages:  eng     Pagination:  791-803     Citation Subset:  AIM; IM    
Department of Cardiothoracic Surgery, Stanford University School of Medcine, Stanford, CA 94305-5247, USA.
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MeSH Terms
Endocardium / physiopathology
Heart Ventricles / physiopathology*
Imaging, Three-Dimensional
Models, Cardiovascular
Myocardial Contraction / physiology
Myocardial Ischemia / physiopathology*
Myocardium / cytology
Myofibrils / physiology
Pericardium / physiopathology
Stress, Mechanical
Systole / physiology
Ventricular Function, Left / physiology
Ventricular Pressure / physiology
Grant Support

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

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