Quasi-Linear Viscoelastic Theory Applied to Internal Shearing of Porcine Aortic Valve Leaflets

[+] Author and Article Information
E. O. Carew, I. Vesely

Department of Biomedical Engineering, The Lerner Research Institute, The Cleveland Clinic Foundation, Cleveland, OH 44195

E. A. Talman

Department of Medical Biophysics, University of Western Ontario, London, Ontario, Canada

D. R. Boughner

Robarts Research Institute, London, Ontario, Canada

J Biomech Eng 121(4), 386-392 (Aug 01, 1999) (7 pages) doi:10.1115/1.2798335 History: Received January 17, 1998; Revised March 17, 1999; Online October 30, 2007


The elements of Quasi-Linear Viscoelastic (QLV) theory have been applied to model the internal shear mechanics of fresh and glutaraldehyde-fixed porcine aortic valve leaflets. A novel function estimation method was used to extract the material functions from experimental shear data obtained at one strain rate, and the model was used to predict the material response at different strain rates. In general, experiments and predictions were in good agreement, the larger discrepancies being in the prediction of peak stresses and hysteresis in cyclic shear. In shear, fixed tissues are stiffer (mean initial shear modulus, 13 kPa versus 427 Pa), take longer to relax to steady state (mean τ2 4,736 s versus 1,764 s) with a slower initial relaxation rate (mean magnitude of Ġ(0), 1 s−1 versus 5 s−1 ), and relax to a lesser extent than fresh tissues (mean percentage stress remaining after relaxation, 60 versus 45 percent). All differences were significant at p = 0.04 or less, except for the initial relaxation slope. We conclude that shear experiments can complement traditional tensile and biaxial experiments toward providing a complete mechanical description of soft biomaterials, particularly when evaluating alternative chemical fixation techniques.

Copyright © 1999 by The American Society of Mechanical Engineers
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