The cyclic changes and structure of the base of the aortic valve

Thubrikar, Mano J.; Nolan, Stanton P.; Bosher, L.Paul; Deck, J. David

doi:10.1016/0002-8703(80)90768-1

Cited by 81 publications

(42 citation statements)

References 6 publications

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“…As important as understanding the dynamic loading behavior of heart valves, few studies have been performed due to technical difficulties. Previous studies by Thubrikar 44,45 estimated the dynamic strains for the aortic valve in vivo, but used onedimensional strain measurement techniques. More recent studies have developed complete in-surface approaches, 17,43 but focus on the aortic valve.…”

Section: Discussionmentioning

confidence: 99%

Surface Strains in the Anterior Leaflet of the Functioning Mitral Valve

Sacks

Baijens

et al. 2002

Annals of Biomedical Engineering

135

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Sacks, Michael S.; He, Z.; Baijens, L.; Wanant, S.; Shah, P.; Sugimoto, H.; Yoganathan, A.P. Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers) Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Abstract-The mitral valve ͑MV͒ is a complex anatomical structure whose function involves a delicate force balance and synchronized function of each of its components. Elucidation of the role of each component and their interactions is critical to improving our understanding of MV function, and to form the basis for rational surgical repair. In the present study, we present the first known detailed study of the surface strains in the anterior leaflet in the functioning MV. The threedimensional spatial positions of markers placed in the central region of the MV anterior leaflet in a left ventricle-simulating flow loop over the cardiac cycle were determined. The resulting two-dimensional in-surface strain tensor was computed from the marker positions using a C 0 Lagrangian quadratic finite element. Results demonstrated that during valve closure the anterior leaflet experienced large, anisotropic strains with peak stretch rates of 500%-1000%/s. This rapid stretching was followed by a plateau phase characterized by relatively constant strain state. We hypothesized that the presence of this plateau phase was a result of full straightening of the leaflet collagen fibers upon valve closure. This hypothesis suggests that the MV collagen fibers are designed to allow leaflet coaptation followed by a dramatic increase in stiffness to prevent further leaflet deformation, which would lead to valvula...

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Section: Discussionmentioning

confidence: 99%

Surface Strains in the Anterior Leaflet of the Functioning Mitral Valve

Sacks

Baijens

et al. 2002

Annals of Biomedical Engineering

135

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“…The sections were either allocated as fresh or static controls or cyclically stretched in a tensile stretch bioreactor to three levels of strain magnitudes: 10% (physiological, see Ref. 34), 15% (pathological/hypertensive), and 20% (hyperpathological/severely hypertensive) at 1.167 Hz, which corresponds to 70 beats/min (2). Fresh cusp sections were extracted from the same location in separate aortic valves.…”

Section: Methodsmentioning

confidence: 99%

Elevated cyclic stretch alters matrix remodeling in aortic valve cusps: implications for degenerative aortic valve disease

Balachandran

Sucosky²,

Jo³

et al. 2009

American Journal of Physiology-Heart and Circulatory Physiology

175

147

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Matrix metalloproteinases (MMPs) and cathepsins are proteolytic enzymes that are upregulated in diseased aortic valve cusps. The objective of this study was to investigate whether elevated cyclic stretch causes an increased expression and activity of these proteolytic enzymes in the valve cusp. Circumferentially oriented fresh porcine aortic valve cusp sections were stretched to 10% (physiological), 15% (pathological), and 20% (hyperpathological) in a tensile stretch bioreactor for 24 and 48 h. The expression and activity of MMP-1, MMP-2, MMP-9, tissue inhibitor of MMP-1, and cathepsin L, S, and K were quantified and compared with fresh controls. Cell proliferation and apoptosis were also analyzed. As a result, at 10% physiological stretch, the expression and activity of remodeling enzymes were comparable with fresh controls. At 15% stretch, the expression of MMP-1, -2, -9 and cathepsin S and K were upregulated, whereas the expression of cathepsin L was downregulated compared with controls. A similar trend was observed at 20% stretch, but the magnitudes of upregulation and downregulation of the expression were less than those observed at 15%. In addition, there were significantly higher cell proliferation and apoptosis at 20% stretch compared with those of other treatment groups. In conclusion, elevated mechanical stretch on aortic valve cusps may detrimentally alter the proteolytic enzyme expression and activity in valve cells. This may trigger a cascade of events leading to an accelerated valve degeneration and disease progression.

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“…The closure mechanisms of the aortic valve are more precise than those involved in the dynamics of the atrioventricular valves, which have a larger coaptation surface and larger subvalvar structures which help the plastic corrections without replacement by prostheses [7][8][9][10][11] . Specific studies of the anatomy of the aortic valve were carried out by Silver and Roberts 12 , Swanson and Clark 13 , Thubrikar et al 14 , and Angelini et al 15 , aiming to better define peculiarities of this valve. In addition to performing an anatomical assessment, they analyzed some linear variables in each cusp and documented the presence of some fenestrations close to the commissural attachments.…”

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confidence: 99%