INVESTIGATION OF THE BLOOD FLOW AND MITRAL-SEPTAL OPPOSITION IN THE LEFT VENTRICLE WITH THE OBSTRUCTIVE HYPERTHROPHIC CARDIOMYOPATHY DURING SYSTOLE USING FLUID-STRUCTURE INTERACTION TECHNIQUE

摘要

In this article, fluid-structure interaction methodology was used to analyze the blood flow and Mitral-Septal opposition in the Left ventricle with the Obstructive Hyperthrophic Cardiomy-opathy (OHCM). The geometry of the computational model in cludes the diseased left ventricle with thickened septum and Mi tral valve. A semi-ellipsoidal geometry was developed with the dimensions, extracted from MR images of the diseased left ven tricle. Also, the geometry of the Mitral valve was created using anatomical data provided in literature [1]. The three element Windkessel model and atrial pressure [2,3] were used to intro duce mass flow and pressure boundary conditions to the aortic orifice and left atrium respectively. Effect of the fibers was taken into account by varying the Young's modulus of the mitral valve tissue with circumferential and radial coordinates. The fluid-structure interaction algorithm started at the beginning of the systole (when the mitral valve is fully open with zero stress) by applying the left ventricular pressure on the left ventricular wall and aortic mass flow outlet on the aortic orifice. The Navier-Stokes equations were solved with SIMPLE algorithm and finite volume method to calculate the blood flow inside the diseased left ventricle. The calculated pressure was applied to the surface ofthe mitral valve and the structural model of the tissue was solved using non-linear finite element. The deformation of the mitral valve was transferred to the blood by moving the fluid mesh. In the next time step, the same procedure was repeated with the new mesh. This algorithm was followed up to the end of the systole. The thickened septum creates a narrow passage for the blood flowing out of the left ventricle, thus a jet of blood flow is devel oped in this narrow passage which applies high shear stress on the anterior leaflet of the mitral valve. The drag force deforms the anterior leaflet toward the septum, obstructing the blood flow rushing toward the aortic orifice.