Abstract:

Mitral regurgitation alters the flow conditions in the left ventricle. To account for quantitative changes and to investigate the behavior of different flow components, a realistic computational model of the whole human heart was employed in this study. While performing fluid dynamics simulations, a scalar transport equation was solved to analyze vortex formation and ventricular wash-out for different regurgitation severities. Additionally, a particle tracking algorithm was implemented to visualize single components of the blood flow. We confirmed a significantly lowered volume of the direct flow component as well as a higher vorticity in the diseased case.

Abstract:

In this thesis, left valvular heart diseases have been analysed based on numerical hemody- namic simulations. Three different severity gradings of mitral regurgitation were imple- mented in the same physiological left human heart, as well as aortic and mitral stenosis. The heart valves have hereby been modeled as porous zones with dynamic permeability. Our approach was to represent mitral regurgitation with an area of high permeability within the porous zone. During ventricular systole, the permeability was set high, in a way that retrograde flow was made possible. In the case of aortic stenosis, a proper ventricular systolic ejection was impaired by an impermeable porous ring. In the case of mitral stenosis, the atrioventricular orifice was guarded by an impermeable porous ring during diastole. The simulated regurgitant volumes agree with clinical measurements to a reasonable extent. Eccentric retrograde jets caused a slightly inferior regurgitant volume. Further, results show that a stenotic valve itself, within a healthy left heart environment, is not alone proficient to generate plausible hemodynamic properties. Modified boundary conditions did not rule out this pitfall. Thus the approach to model heart valves as porous zones is questionable. The conception of a high fidelity human mitral valve model, whereupon a wide morphomet- rical range can be addressed, inspired the modelling of a parametric mitral valve. An adaptable mitral valve model was developed using hyperbolic parabolic functions. Afore- mentioned prepares subsiding numerical hemodynamic simulations with prescribed mitral valve leaflet motion and can supersede the porous zone approach.