Analysis of mitral valve regurgitation by computational fluid dynamics

Abstract

The clinical syndrome of mitral insufficiency is a common consequence of mitral valve (MV) prolapse, when the MV leaflets do not seal the closed orifice and blood regurgitates back to the atrium during ventricular contraction. There are different types of MV prolapse that may influence the degree of regurgitation also in relation to the left ventricle (LV) geometry. This study aims to provide some insight into the fluid dynamics of MV insufficiency in view of improving the different measurements available in the clinical setting. The analysis is performed by a computational fluid dynamics model coupled with an asymptotic model of the MV motion. The computational fluid dynamics solution uses the immersed boundary method that is efficiently integrated with clinical imaging technologies. Healthy and dilated LVs obtained by multislice cardiac MRI are combined with simplified models of healthy and pathological MVs deduced from computed tomography and 4D-transesophageal echocardiography. The results demonstrated the properties of false regurgitation, blood that did not cross the open MV orifice and returns into the atrium during the backward motion of the MV leaflets, whose entity should be accounted when evaluating small regurgitation. The regurgitating volume is found to be proportional to the effective orifice area, with the limited dependence of the LV geometry and type of prolapse. These affect the percentage of old blood returning to the atrium which may be associated with thrombogenic risk.

Comparative Analysis of Right Ventricle Fluid Dynamics

“…The two leaflets were allowed to move independently, each one associated with a degree of opening, say φ 1 ( t ) and φ 2 ( t ), for the anterior and posterior leaflets, respectively. The valve geometry is described by its coordinates X mv (ϑ, s , φ 1 , φ 2 ), which represents a two-dimensional set of intermediate positions associated with the different degrees of leaflets openings (Collia et al, 2019b ). This set of possible geometries is estimated by interpolation between the closed X mv (ϑ, s , 0, 0), and open configurations obtained from images as previously described.…”

Electro-fluid-mechanics of the heart

“…As an aside, we note that during mitral and tricuspid valve closure their leaflets approach while moving towards the atria and even after coapting, they keep retreating until the tension balances the pressure difference. This causes a physiologic backflow called ‘false regurgitation’ which is necessary for the proper sealing of the atrioventricular valves (Collia, Zovatto & Pedrizzetti 2019); the same phenomenon, however, produces also a pressure spike that, in the long term, could damage the thin atrial walls. To avoid this problem, each atrium is provided with a histologically distinct appendage which operates as a decompression chamber during ventricular systole or in the event of increased atrial pressure (Al-Saady, Obel & Camm 1999).…”

Surrogate models provide new insights on metrics based on blood flow for the assessment of left ventricular function

“…The study of fluid dynamics inside the left ventricle (LV) of the human heart is of considerable interest for the identification of long and short-term pathologies 1 , 2 . Several studies in the literature have highlighted how flow-mediated metrics participate to the progression or regression of cardiac pathologies 3 , 4 , making intracardiac fluid dynamics an increasingly integral part of clinical evaluations.…”

“…To date, various diagnostic techniques are used for the identification of flow-related LV functional properties through the use of tools such as 2D-transthoracic echocardiography, 4D-transesophageal echocardiography, and cardiac magnetic resonance (CMR), even though they present several limitations and are not routinely employed in clinical applications. At the same time, the direct numerical simulation (DNS) of the equation governing blood flow, carefully integrated with the boundary information obtained from routine diagnostic imaging, represents an alternate approach that is becoming popular in clinical research involving intraventricular fluid dynamics 6 – 8 ; this approach is demonstrating usefulness for analyzing patient-specific cardiac flow conditions 2 , 9 . DNS also represents a viable tool to integrate existing imaging technology and extend it with the capability of reproducing flow details in virtual conditions corresponding to hypothetical therapeutic solutions 10 .…”