Effects Of Papillary Muscle Position On The In Vitro Dynamic by dfhrf555fcg


									P86. Effects of Papillary Muscle Position on the In Vitro
Dynamic Strain on the Porcine Mitral Valve
Zhaoming He
Georgia Institute of Technology, Atlanta, Georgia, United States

OBJECTIVES: To understand the in-vitro dynamic strain on the anterior leaflet of the porcine
mitral valve.
METHODS: Fresh porcine valves were mounted in an in-vitro physiological flow loop. Two
papillary muscles (PMs) were set to normal, taut, and slack positions to simulate pathological
PM displacements. Dual camera stereo photogrammetry was used to monitor the motion of the
mitral valve anterior leaflet. Tissue deformation was measured by tracking the displacements
of sixteen markers placed in the central region of the anterior leaflet. Local leaflet tissue strain
and strain rates were calculated from the measured displacements under dynamic loading
conditions. A total of 11 mitral valves were studied.
RESULTS: 1) There was a rapid rise in anterior leaflet strain during valve closure, followed
by a plateau, where no additional strains occurred. Furthermore, the strain field was highly
anisotropic with larger strains in the radial direction. 2) The averaged areal strain rate during
valve closure was typically ~750% per second in the normal PM position. 3) The anterior
leaflet showed the highest areal strain rate during valve closure when the PM was in the slack
position. Furthermore, the slack PM position led to a delay in the transition and rapid leaflet
stiffening in late systole, compared to the other two PM positions.
CONCLUSIONS: The mitral valve exhibited a pronounced mechanically anisotropic
behavior. PM position influenced the loading process in the central area of the anterior leaflet,
with slack PM position causing rapid sudden stiffening in late systole.

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