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This Article Full Text Full Text (PDF) All Versions of this Article: 295/3/H1141    most recent 00284.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Krishnamurthy, G. Articles by Ingels, N. B. PubMed PubMed Citation Articles by Krishnamurthy, G. Articles by Ingels, N. B., Jr.

Material properties of the ovine mitral valve anterior leaflet in vivo from inverse finite element analysis

Departments of ¹Cardiothoracic Surgery and ²Mechanical Engineering, Stanford University, Stanford, California; ³Department of Management and Engineering, Linköping University, Linköping, Sweden; and ⁴Laboratory of Cardiovascular Physiology and Biophysics, Research Institute of the Palo Alto Medical Foundation, Palo Alto, California

Submitted 15 March 2008 ; accepted in final form 8 July 2008

We measured leaflet displacements and used inverse finite-element analysis to define, for the first time, the material properties of mitral valve (MV) leaflets in vivo. Sixteen miniature radiopaque markers were sewn to the MV annulus, 16 to the anterior MV leaflet, and 1 on each papillary muscle tip in 17 sheep. Four-dimensional coordinates were obtained from biplane videofluoroscopic marker images (60 frames/s) during three complete cardiac cycles. A finite-element model of the anterior MV leaflet was developed using marker coordinates at the end of isovolumic relaxation (IVR; when the pressure difference across the valve is 0), as the minimum stress reference state. Leaflet displacements were simulated during IVR using measured left ventricular and atrial pressures. The leaflet shear modulus (G_circ-rad) and elastic moduli in both the commisure-commisure (E_circ) and radial (E_rad) directions were obtained using the method of feasible directions to minimize the difference between simulated and measured displacements. Group mean (±SD) values (17 animals, 3 heartbeats each, i.e., 51 cardiac cycles) were as follows: G_circ-rad = 121 ± 22 N/mm², E_circ = 43 ± 18 N/mm², and E_rad = 11 ± 3 N/mm² (E_circ > E_rad, P < 0.01). These values, much greater than those previously reported from in vitro studies, may result from activated neurally controlled contractile tissue within the leaflet that is inactive in excised tissues. This could have important implications, not only to our understanding of mitral valve physiology in the beating heart but for providing additional information to aid the development of more durable tissue-engineered bioprosthetic valves.

mitral valve material properties; inverse finite-element analysis; ovine model; radiopaque markers