title: Planar biaxial creep and stress relaxation of the mitral valve anterior leaflet.
abstract: A fundamental assumption in mitral valve (MV) therapies is that a repaired or replaced valve should mimic the functionality of the native valve as closely as possible. Thus, improvements in valvular treatments are dependent on the establishment of a complete understanding of the function and mechanical properties of the native normal MV. In a recent study [Grashow et al. ABME 34(2), 2006] we demonstrated that the planar biaxial stress-strain relationship of the MV anterior leaflet (MVAL) exhibited minimal hysteresis and a stress-strain response independent of strain rate, suggesting that MVAL could be modeled as a "quasi-elastic" material. The objective of our current study was to expand these results to provide a more complete picture of the time-dependent mechanical properties of the MVAL. To accomplish this, biaxial stress-relaxation and creep studies were performed on porcine MVAL specimens. Our primary finding was that while the MVAL leaflet exhibited significant stress relaxation, it exhibited negligible creep over the 3-h test. These results furthered our assertion that the MVAL functionally behaves not as a linear or non-linear viscoelastic material, but as an anisotropic quasi-elastic material. These results appear to be unique in the soft tissue literature; suggesting that valvular tissues are unequalled in their ability to withstand significant loading without time-dependent material effects. Moreover, insight into these specialized characteristics can help guide and inform efforts directed toward surgical repair and engineered valvular tissue replacements.
authors.affiliation: Department of Bioengineering, Engineered Tissue Mechanics Laboratory, University of Pittsburgh, 100 Technology drive, Room 234, PA 15219, USA.
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Grashow
authors.forename: Michael S
authors.initials: MS
authors.lastname: Sacks
authors.forename: Jun
authors.initials: J
authors.lastname: Liao
authors.forename: Ajit P
authors.initials: AP
authors.lastname: Yoganathan
mesh_terms: D000818:Animals; D016880:Anisotropy; D001696:Biomechanical Phenomena; D001698:Biomedical Engineering; D004548:Elasticity; D066298:In Vitro Techniques; D008943:Mitral Valve / Q000033:anatomy & histology* / Q000502:physiology*; D008955:Models, Cardiovascular; D013314:Stress, Mechanical; D034421:Sus scrofa