J. Park2, P. Bonde1 1Yale University School Of Medicine,Cardiac Surgery,New Haven, CT, USA 2Yale University School Of Medicine,Bonde Artificial Heart Lab,New Haven, CT, USA
Introduction:
Current understanding of myxomatous mitral valve prolapse is limited to longitudinal echocardiographic studies with indicators of left ventricular adverse remodeling. This has resulted in surgical interventions being instituted when left ventricular dilatation has reached a certain dimension. Fundamental understanding of the mitral valve mechanism may provide a therapeutic target to be instituted earlier. In this study, we performed a computational study on the kinematics of the two-papillary muscles manipulating mitral valve motion.
Methods:
Three dimensional model of mitral valve is considered as a body at one end with two massless rods connected to the other end representing annular leaflet and chordal attachments. In order to evaluate spatial motion of each papillary muscle in three dimensions and determine its physiologically working range in cardiac cycle, kinematic analysis was carried out. Two massless rods within six degrees of freedom were simulated by varying its thickness and orientations based on spherical coordinate system (r, θ, φ), where r is thickness of the papillary muscle, θ is polar angle, and φ is azimuthal angle. Assuming that papillary muscle thickness variations can represent annulo-papillary muscle distance, three different thicknesses of 10, 15, and 25 mm were used in the simulation. Based on the plausible interpapillary muscle distance variations defined as 15 to 30 mm, three dimensional working ranges of the two papillary muscles for each condition were visualized.
Results:
Possible combinations were evaluated with a step interval of π/10. Assuming that two papillary muscles approaching or receding to each other within 45 degrees at maximum from their vertical position in systole and diastole, the distance between the fixed points of them are set to be 22.5 mm. For the simulation case with the papillary muscle thickness of 10 mm, 4961 out of 10201 cases, (48.6%) were found to be effective orientations for creating plausible interpapillary muscle distance from 15 to 30 mm. With larger thickness for both (r1, r2 = 25 mm), effective cases were reduced to 30% (2961 out of 10201 cases) and the working range overlaps up to the fixing position of each other, meaning fixing distance of the papillary muscle needs to be properly set based on their spatial movement. Within different thicknesses, 10 mm for the one papillary muscle (r1 = 10 mm and 25 mm for the other papillary muscle (r1 = 25 mm , asymmetric working zone could be seen.
Conclusion:
Three dimensional kinematic analysis on two papillary muscles offers unique insights in to the working ranges and interactions based on their geometries and configurations. This model offers a foundation for an advanced dynamic model of mitral valve.
