Document Detail

Increased reversal and oscillatory shear stress cause smooth muscle contraction-dependent changes in sheep aortic dynamics: role in aortic balloon pump circulatory support.
MedLine Citation:
PMID:  17973954     Owner:  NLM     Status:  MEDLINE    
AIMS: The intra-aortic balloon pumping (IABP) changes pressure and increases the aorta shear stress reversal (SS(R)) and oscillatory (SS(O)) components. Hence, IABP-dependent changes in aortic biomechanics would be expected, because of vascular smooth muscle (VSM) tone (i.e. flow-induced endothelium-dependent response, related to SS(R) and SS(O) variations) and/or pressure changes. To characterize: (i) the IABP effects on the aortic and global (systemic circulation) biomechanics, analysing their dependence on pressure and VSM basic tone changes and (ii) the relation between the SS(R) and SS(O) and the aortic biomechanical changes associated with the VSM tone variations. METHODS: Aortic flow, pressure and diameter were measured in eight sheep during basal, augmented and assisted beats (1 : 1 and 1 : 2 IABP modalities). Calculations: (i) aortic effective and isobaric elasticity, viscosity, circumferential stress, pulse wave velocity, shear stress and buffer and conduit functions, (ii) peripheral resistance, global compliance, reflection coefficient and wave propagation times and (iii) the relation between SS(R) and SS(O) and biomechanical changes associated with variations in the aortic VSM tone. RESULTS: Augmented and assisted beats showed: global VSM relaxation pattern (reduced peripheral resistance and reflection coefficient; increased propagation times) and local VSM contraction pattern (increased viscosity; reduced diameter, elasticity and circumferential stress), associated with SS(R) and SS(O), levels and changes. The vascular changes reduced the ventricle afterload determinants, increased the vascular buffer performance and kept the conduit capability. CONCLUSION: In addition to pressure-dependent changes, IABP determined biomechanical changes related to variations in the VSM tone. The increased SS(R) and SS(O) were associated with the aortic VSM contraction pattern and biomechanical changes.
D Bia; Y Zócalo; R Armentano; J Camus; E de Forteza; E Cabrera-Fischer
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2007-10-31
Journal Detail:
Title:  Acta physiologica (Oxford, England)     Volume:  192     ISSN:  1748-1716     ISO Abbreviation:  Acta Physiol (Oxf)     Publication Date:  2008 Apr 
Date Detail:
Created Date:  2008-02-29     Completed Date:  2008-03-27     Revised Date:  2009-02-03    
Medline Journal Info:
Nlm Unique ID:  101262545     Medline TA:  Acta Physiol (Oxf)     Country:  England    
Other Details:
Languages:  eng     Pagination:  487-503     Citation Subset:  IM    
Physiology Department, School of Medicine, Republic University, Montevideo, Uruguay.
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MeSH Terms
Aorta / physiology*
Intra-Aortic Balloon Pumping*
Muscle, Smooth / physiology*
Shear Strength
Vasoconstriction / physiology*

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