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  • American Physiological Society  (3)
  • 2000-2004  (3)
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Verlag/Herausgeber
  • American Physiological Society  (3)
Sprache
Erscheinungszeitraum
  • 2000-2004  (3)
Jahr
Fachgebiete(RVK)
  • 1
    Online-Ressource
    Online-Ressource
    American Physiological Society ; 2003
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 284, No. 5 ( 2003-05-01), p. H1552-H1559
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 284, No. 5 ( 2003-05-01), p. H1552-H1559
    Kurzfassung: Hyperglycemia is associated with generation of reactive oxygen species (ROS), and this action may contribute to accelerated atherogenesis. We tested the hypothesis that hyperglycemia produces alterations in left anterior descending coronary artery (LAD) wall shear stress concomitant with endothelial dysfunction and ROS production in dogs ( n = 12) instrumented for measurement of LAD blood flow, velocity, and diameter. Dogs were randomly assigned to receive vehicle (0.9% saline) or the superoxide dismutase mimetic 4- hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (tempol) and were administered intravenous infusions of d-glucose to achieve target blood glucose concentrations of 350 and 600 mg/dl (moderate and severe hyperglycemia, respectively). Endothelial function and ROS generation were assessed by coronary blood flow responses to acetylcholine (10, 30, and 100 ng/kg) and dihydroethidium fluorescence of myocardial biopsies, respectively. Indexes of wall shear stress were calculated with conventional fluid dynamics theory. Hyperglycemia produced dose-related endothelial dysfunction, increases in ROS production, and reductions in oscillatory shear stress that were normalized by tempol. The results suggest a direct association between hyperglycemia-induced ROS production, endothelial dysfunction, and decreases in oscillatory shear stress in vivo.
    Materialart: Online-Ressource
    ISSN: 0363-6135 , 1522-1539
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 2003
    ZDB Id: 1477308-9
    SSG: 12
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Online-Ressource
    Online-Ressource
    American Physiological Society ; 2002
    In:  Journal of Applied Physiology Vol. 93, No. 6 ( 2002-12-01), p. 1939-1946
    In: Journal of Applied Physiology, American Physiological Society, Vol. 93, No. 6 ( 2002-12-01), p. 1939-1946
    Kurzfassung: Coronary stents improve resting blood flow and flow reserve in the presence of stenoses, but the impact of these devices on fluid dynamics during profound vasodilation is largely unknown. We tested the hypothesis that stent implantation affects adenosine-induced alterations in coronary hemodynamics and wall shear stress in anesthetized dogs ( n = 6) instrumented for measurement of left anterior descending coronary artery (LAD) blood flow, velocity, diameter, and radius of curvature. Indexes of fluid dynamics and shear stress were determined before and after placement of a slotted-tube stent in the absence and presence of an adenosine infusion (1.0 mg/min). Adenosine increased blood flow, Reynolds (Re) and Dean numbers (De), and regional and oscillatory shear stress concomitant with reductions in LAD vascular resistance and segmental compliance before stent implantation. Increases in LAD blood flow, Re, De, and indexes of shear stress were observed after stent deployment ( P 〈 0.05). Stent implantation reduced LAD segmental compliance to zero and potentiated increases in segmental and coronary vascular resistance during adenosine. Adenosine-induced increases in coronary blood flow and reserve, Re, De, and regional and oscillatory shear stress were attenuated after the stent was implanted. The results indicate that stent implantation blunts alterations in fluid dynamics during coronary vasodilation in vivo.
    Materialart: Online-Ressource
    ISSN: 8750-7587 , 1522-1601
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 2002
    ZDB Id: 1404365-8
    SSG: 12
    SSG: 31
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    In: Journal of Applied Physiology, American Physiological Society, Vol. 97, No. 1 ( 2004-07), p. 424-430
    Kurzfassung: Restenosis limits the effectiveness of stents, but the mechanisms responsible for this phenomenon remain incompletely described. Stent geometry and expansion during deployment produce alterations in vascular anatomy that may adversely affect wall shear stress (WSS) and correlate with neointimal hyperplasia. These considerations have been neglected in previous computational fluid dynamics models of stent hemodynamics. Thus we tested the hypothesis that deployment diameter and stent strut properties (e.g., number, width, and thickness) influence indexes of WSS predicted with three-dimensional computational fluid dynamics. Simulations were based on canine coronary artery diameter measurements. Stent-to-artery ratios of 1.1 or 1.2:1 were modeled, and computational vessels containing four or eight struts of two widths (0.197 or 0.329 mm) and two thicknesses (0.096 or 0.056 mm) subjected to an inlet velocity of 0.105 m/s were examined. WSS and spatial WSS gradients were calculated and expressed as a percentage of the stent and vessel area. Reducing strut thickness caused regions subjected to low WSS ( 〈 5 dyn/cm 2 ) to decrease by ∼87%. Increasing the number of struts produced a 2.75-fold increase in exposure to low WSS. Reducing strut width also caused a modest increase in the area of the vessel experiencing low WSS. Use of a 1.2:1 deployment ratio increased exposure to low WSS by 12-fold compared with stents implanted in a 1.1:1 stent-to-vessel ratio. Thinner struts caused a modest reduction in the area of the vessel subjected to elevated WSS gradients, but values were similar for the other simulations. The results suggest that stent designs that reduce strut number and thickness are less likely to subject the vessel to distributions of WSS associated with neointimal hyperplasia.
    Materialart: Online-Ressource
    ISSN: 8750-7587 , 1522-1601
    RVK:
    RVK:
    Sprache: Englisch
    Verlag: American Physiological Society
    Publikationsdatum: 2004
    ZDB Id: 1404365-8
    SSG: 12
    SSG: 31
    Standort Signatur Einschränkungen Verfügbarkeit
    BibTip Andere fanden auch interessant ...
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