The Effects of Sterilization and Storage Treatments on the Stress-Strain Behavior of Aortic Valve Leaflets

Tan, Annette; Holt, D.L.

doi:10.1016/s0003-4975(10)63984-7

Cited by 19 publications

(3 citation statements)

References 1 publication

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“…A material having less stiffness (lower elastic modulus) is easier to bend than a material having greater stiffness (higher elastic modulus). In vitro, stress-strain studies of fresh human (Clark, 1973;Wright and Ng, 1974;Yamada, 1970), porcine (Tan and Holt, 1976;Robel, 1972), and canine (Mundth et al, 1971) aortic leaflets have shown that the leaflets have a variable elastic modulus with a lower and a higher range. However, it is not known whether the leaflets function at both the lower and the higher values of moduli in vivo.…”

mentioning

confidence: 99%

The elastic modulus of canine aortic valve leaflets in vivo and in vitro.

Thubrikar¹,

Piepgrass²,

Bosher³

et al. 1980

Circulation Research

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Aortic valve leaflets undergo extraordinary flexion due to the complete reversal of their curvature during billions of cardiac cycles. The flexion stresses in the leaflet depend on its elastic modulus which we investigated in vivo and in vitro. In six dogs, we placed radiopaque markers on an aortic leaflet. Leaflet length was calculated from the marker positions recorded fluoroscopically. Aortic and ventricular pressures were recorded. Dogs were killed and leaflet stress-strain curves determined in vitro. Leaflet length in vivo decreased 10.4 +/- 4.7% from diastole to systole in each cardiac cycle. Using the law of LaPlace, pressure gradients across the leaflets were converted into the stresses in the leaflets. The leaflets had an initial "elastic phase" of low modulus in systole followed by an "inelastic phase" of high modulus in diastole. The elastic modulus was 2.4 +/- 0.7 x 10(6) dynes/cm2 in systole and 5.2 +/- 1.7 x 10(7) dynes/cm2 in diastole. These results were similar to those obtained in vitro. Since flexion rigidity is proportional to (elastic modulus) x (thickness)3, the lower modulus in systole greatly reduces flexion stresses in the leaflet and increases leaflet longevity. The higher elastic modulus in diastole prevents excessive bulging or prolapse of the leaflet while it is subjected to the diastolic pressure gradient. We conclude that a natural or prosthetic leaflet which is thickened or has a high elastic modulus throughout the cardiac cycle will have a greater flexion stress that could cause early failure.

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mentioning

confidence: 99%

The elastic modulus of canine aortic valve leaflets in vivo and in vitro.

Thubrikar¹,

Piepgrass²,

Bosher³

et al. 1980

Circulation Research

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“…For aortic valve leaflet and WPD, tensile moduli were 7.25 ± 2.10 MPa and ~ 3 GPa and tensile ultimate strengths were 1.83 ± 0.64 MPa and ~ 40 MPa, respectively. [22][23][24] Among all the substrates, the CON substrate was significantly lower (p < 0.01 by ANOVA) in terms of stiffness and ultimate strength.…”

Section: Resultsmentioning

confidence: 93%

“…The uniaxial bulk tensile moduli of CON and RON substrates were 0.33 ± 0.19 MPa and 3.82 ± 1.03 MPa, respectively, and their ultimate strengths were 0.14 ± 0.06 MPa and 1.21 ± 0.39 MPa, respectively. For aortic valve leaflet and WPD, tensile moduli were 7.25 ± 2.10 MPa and ∼3 GPa and tensile ultimate strengths were 1.83 ± 0.64 MPa and ∼40 MPa, respectively. − Among all the substrates, the CON substrate was significantly lower ( p < 0.01 by ANOVA) in terms of stiffness and ultimate strength.…”

Section: Resultsmentioning

confidence: 96%

In Vitro Model of a Fibrosa Layer of a Heart Valve

Jana

Lerman

Simari³

2015

ACS Appl. Mater. Interfaces

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The fibrosa layer of a cardiac aortic valve is composed mostly of a dense network of type I collagen fibers oriented in circumferential direction. This main layer bears the tensile load and responds to the high stress on a leaflet. The inner fibrosa layer is also the site of pathophysiologic changes that result in valvular dysfunction, including stenosis and regurgitation. In vitro studies of these changes are limited by the absence of a substrate that mimics the circumferentially oriented structure of the fibrosa layer. In heart valve tissue engineering, generation of this layer is challenging. This study aimed to develop an artificial fibrosa layer of a native aortic leaflet. A unique morphologically biomimicked, pliable, but standalone substrate with circumferentially oriented nanofibers was fabricated by electrospinning on a novel collector designed for this study. The substrate had low-bulk tensile stiffness and ultimate strength; thus, cultured valvular interstitial cells (VICs) showed a fibroblast phenotype that is generally observed in a healthy aortic leaflet. Furthermore, gene and protein expression and morphology of VICs in substrates were close to those in the fibrosa layer of a native aortic leaflet. This artificial fibrosa layer can be useful for in vitro studies of valvular dysfunctions.

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Stress analysis of porcine bioprosthetic heart valves in vivo

Thubrikar

Skinner

Eppink

et al. 1982

J. Biomed. Mater. Res.

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During the normal functioning of aortic porcine bioprosthetic valves, the leaflets undergo complex configurational changes which can produce stresses large enough to damage the leaflets. Stress analyses of these valves in vivo have not been performed before. We investigated the behavior of aortic bioprostheses in vivo in calves by placing radiopaque markers on the valves and observing them under x-ray. Based upon the behavior of the leaflets, a method of stress analysis is proposed. Membrane stresses were associated with a pressure gradient across the leaflet and bending stresses with a change in the leaflet curvature. Total stresses were obtained by summation of the two stresses. A model of leaflet deformation at its attachment is proposed and the stresses determined. In diastole, the total stresses in the leaflet were tensile. In systole, the total stresses at the leaflet attachment were large and compressive on the aortic surface. Since the leaflet is unable to sustain compressive stresses, it is concluded that large compressive stresses cause structural damage at the leaflet attachment. This may explain the clinical observation that bioprosthetic leaflets detach or calcify in this region.

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The Effects of Sterilization and Storage Treatments on the Stress-Strain Behavior of Aortic Valve Leaflets

Cited by 19 publications

References 1 publication

The elastic modulus of canine aortic valve leaflets in vivo and in vitro.

The elastic modulus of canine aortic valve leaflets in vivo and in vitro.

In Vitro Model of a Fibrosa Layer of a Heart Valve

Stress analysis of porcine bioprosthetic heart valves in vivo

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