Behaviour of the bovine pericardium used in cardiac bioprostheses when subjected to a real fatigue assay

Martín, A. Carrera San; Paez, J.M. Garci ́a; Jorge-Herrero, Eduardo; Navidad, R.; Sestafe, J.V. Garci ́a; Candela, Ignacio; Castillo‐Olivares, J. L.

doi:10.1016/0142-9612(93)90079-h

Cited by 18 publications

(1 citation statement)

References 22 publications

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“…[1][2][3][4] Histologic and ultrastructural studies 5 have failed to determine definitively whether the bioprostheses are unreliable because of mechanical or metabolic aspects, or both. [6][7][8] Among the causes of the failure of the bioprostheses made of calf pericardium, the role of the interaction among the different materials employed in their construction may not have been assessed thoroughly enough. This interaction can be described as the effect produced when two or more materials with different mechanical and/or elastic characteristics are joined to form a functional structure: in the case of bioprostheses, the relationship between the suture and the pericardium that make up the valve leaflet.…”

Section: Introductionmentioning

confidence: 99%

Selection and interaction of biomaterials used in the construction of cardiac bioprostheses

Martín¹,

Páez²,

Sestafé³

et al. 1998

J. Biomed. Mater. Res.

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The mechanical behavior of calf pericardium employed in the manufacture of cardiac bioprostheses was assessed according to the region from which it was selected. For this purpose, selected samples of the tissue were sewn with different types of commercially available sutures and subjected to tensile testing, the results of which were compared with the findings in selected, but not sutured, tissue used as a control. The results confirm a loss of resistance--that is, a reduction of the capacity of sutured samples of the biomaterial to withstand breakage stress compared with control samples. Taking into account the marked resistance to breakage of the suture thread, this phenomenon can only be explained as a consequence of the deleterious mechanical interaction between the suture and chemically treated pericardium. This interaction is illustrated by the shearing force which is responsible for the loss of resistance in the tested samples. These trials demonstrate that the results can be improved and the deleterious interaction diminished, although not eliminated, when the pericardium is selected from a given region.

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Section: Introductionmentioning

confidence: 99%

Selection and interaction of biomaterials used in the construction of cardiac bioprostheses

Martín¹,

Páez²,

Sestafé³

et al. 1998

J. Biomed. Mater. Res.

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Mechanical behavior of chemically treated ostrich pericardium subjected to uniaxial tensile testing: influence of the suture

Páez

Carrera

Herrero

et al. 2002

J. Biomed. Mater. Res.

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The mechanical behavior of sutured ostrich pericardium was studied by uniaxial tensile testing. One hundred forty-four tissue specimens were assessed: 96 sutured samples (48 in which a centrally located suture was placed at an angle of 90 degrees with respect to the longitudinal axis, whereas in the remaining 48, a centrally located suture was placed at a 45 degrees angle to the longitudinal axis, in sets of 12 samples each, sewn with sutures made of Gore-Tex, nylon, Prolene, or silk), and 48 unsutured controls. Each group of 24 samples sewn at one angle or the other with the different suture materials was assayed together with a corresponding control group of 12 unsutured samples. The mean tensile strengths in the unsutured controls ranged between 30.16 MPa and 43.42 MPa, whereas those of the sutured sets ranged from 14.68 MPa to 21.91 MPa. The latter presented a statistically significant loss of resistance (p < 0.01) when compared with the unsutured tissue samples. The angle of the suture with respect to the longitudinal axis influenced the degree of shear stress produced by the suture, as well as the behavior of the different suture materials used. The set of samples sewn with Prolene appeared to be that most sensitive to changes in the angle of the suture, whereas tissue sewn at a 45 degrees angle with Gore-Tex presented lower shear stress values in comparison with samples in which the other three materials were used. A method of tissue selection based on morphological and mechanical criteria was used to ensure the homogeneity of the results in such a way that the coefficients of determination (R2) for the stress/strain curve fitting equation ranged between 0.888 and 0.995. This excellent fit made it possible, applying regression analysis, to predict the mechanical behavior of a specimen by determining that of a contiguous tissue sample. Thus, it should be possible, at least theoretically, to characterize the behavior of a specific region or zone of the biomaterial. In conclusion, ostrich pericardium exhibits strong resistance to rupture, even when sutured. The selection method used ensures the homogeneity of the samples and, thus, of the results. The angle of the suture with respect to the longitudinal axis, where the load is centered, determines the shear stress produced by the suture and the mechanical behavior of each suture material.

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Durability of a cardiac valve leaflet made of calf pericardium: Fatigue and energy consumption

Páez

Sanmartín

Herrero

et al. 2006

J Biomedical Materials Res

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We studied the mechanical behavior of membranes of calf pericardium, similar to those employed in prosthetic valve leaflets, when subjected to tensile fatigue. The objective was to assess its durability, as a fundamental property of cardiac bioprosthesis, and analyze the energy consumption. For this purpose, the authors built a hydraulic simulator to subject a spherical valve leaflet made of calf pericardium to cyclic stress mimicking cardiac function. A total of 522 assays were performed in 40 samples, subjected to cyclic pressures greater than 6 atm, and 482 subjected to pressures ranging between 2 and 6 atm. The mathematical expression that establishes the relationship between the pressure exerted and the frequency was obtained. If we assume that the function is continuous, this equation provides the range of fatigue tolerated for a given number of cycles. Using the optimal values (the five highest values per series), the expression was found to be y = 9.95x(-0 1214) (R(2) = 0.955), where x represents the frequency in cycles per second and y the pressure in atmospheres. In addition, we established the mathematical relationship between the energy consumed and the frequency, which was a function of the pressure exerted, regardless of the region or zone from which the samples had been obtained. The methods of manual and morphology-based selection employed produced widely dispersed results. When a mechanical criterion was included, the similarity in the energy consumed during fatigue testing markedly improved the correlation, with a coefficient of determination between paired samples of R(2) = 0.7477. A mechanical criterion, such as energy consumption, can help to improve sample selection and produce more consistent results. Finally, we obtained the mathematical expression that relates the energy consumed to the pressure exerted and the number of cycles per second to which the valve leaflet was subjected. This procedure enables us to establish the limit to the energy that a biomaterial can consume over a period of time during which it is subjected to a working pressure and, thus, calculate more precisely its durability.

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Behaviour of the bovine pericardium used in cardiac bioprostheses when subjected to a real fatigue assay

Cited by 18 publications

References 22 publications

Selection and interaction of biomaterials used in the construction of cardiac bioprostheses

Selection and interaction of biomaterials used in the construction of cardiac bioprostheses

Mechanical behavior of chemically treated ostrich pericardium subjected to uniaxial tensile testing: influence of the suture

Durability of a cardiac valve leaflet made of calf pericardium: Fatigue and energy consumption

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