Biaxial mechanical behavior of excised porcine mitral valve
leaflets.
May-Newman, Karen, and Frank C. P. Yin.
Division of Cardiology, Department of Medicine and Department of
Biomedical Engineering, Johns Hopkins School of Medicine, Baltimore,
MD 21205
APStracts 2:0156H, 1995.
Anterior and posterior leaflets from excised porcine mitral valves
were mechanically tested under cyclic equibiaxial and strip biaxial
stretch protocols at a strain rate of 4-12 %/sec following
preconditioning. Cauchy stress and Lagrangian strain were calculated
for both membrane and 3-D cases. The leaflets exhibited nonlinearly
elastic, anisotropic behavior. Both anterior and posterior leaflets
were less extensible in the circumferential than in the radial
direction under equibiaxial loading, with stress ratios of 5.7 and
4.3, respectively. The posterior leaflets exhibited greater
extensibility in both directions and lower circumferential post
-transitional moduli (ranges 690-820 vs. 2500-3200 N/m for anterior).
This larger posterior extensibility may be due to the greater number
of chordal attachments, which provide additional mechanical stability
to this structure. Coupling of radial and circumferential mechanical
behavior was evidenced by the response to different stretch
protocols, indicating a complex microstructural coupling between
individual collagen fibers or bundles. These are the first biaxial
data for mitral valves and are a foundation for the development of a
more detailed quantitative material description.
Received 19 December 1994; accepted in final form 11 April 1995.
APS Manuscript Number H1110-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 April 1995.