Patient-specific fluid simulation of transcatheter mitral valve replacement in mitral annulus calcification

Abstract

IntroductionTranscatheter mitral valve replacement is a promising alternative to open-heart surgery in elderly patients. Patients with severe mitral annulus calcification (MAC) are a particularly high-risk population, where postprocedural complications can have catastrophic effects. Amongst these, obstruction of the left ventricular outflow tract can lead to ventricular hypertrophic remodeling and subsequent heart failure, while subclinical valve thrombosis can result in early bioprosthetic valve failure.MethodsTo elucidate the mechanisms of left ventricular outflow tract obstruction and valve thrombosis following valve-in-MAC procedures, we used image processing and Computational Fluid Dynamics (CFD) software to generate patient- and device-specific models based on preprocedural CT data. Personalized computer simulations were performed to predict the left ventricular haemodynamics after implantation in three patients with severe MAC.ResultsThe simulations have successfully captured the increased pressure gradient in the left ventricular outflow tract as a result of the partial obstruction due to the implanted valve. Regions of wall shear stress above the threshold value for platelet activation were also observed on the bioprosthetic frame as a result of the reduced outflow tract area, which led to increases in flow resistance and blood residence time inside the ventricle. Consistent with these findings, areas of slow recirculating flow and blood stasis formed near the valve frame, creating potential pro-thrombotic conditions.DiscussionThis study provides insight into the relationship between size and shape of the outflow tract post-implantation, pressure gradients and pro-thrombotic flow metrics such as wall shear stress and blood residence time. Results show the potential of CFD modeling to bring key functional metrics into preprocedural assessment for a comprehensive evaluation of post-procedural risks beyond anatomical factors. Following further validation and extension to the atrial chamber, this approach can provide an in-depth analysis of the likelihood of valvular thrombosis.

A new boundary growth model for the analysis of microscopic blockage and various cross-section shapes effects in porous functional medical material

“…Since Computational Fluid Dynamics (CFD) can reflect changes in the fluid state from changes in the overall physical environment in which the fluid is located, some scholars in the medical field are currently studying the blood flow mechanism as well as the coagulation mechanism through CFD. For example, Hill et al (Hill et al, 2022) used CFD to study the risk of thrombosis near ventricular valves; Sun et al (Sun and Chaichana, 2010) used CFD to study the effect of renal stents on blood flow; And Zhao and Hao (Zhao et al, 2021) firstly proposed a CFD physical model of thrombus blockage inside hemostatic materials, which revealed the coagulation mechanism of the hemostatic materials from the perspective of blood flow. It can be seen that CFD plays a crucial role in blood research in the medical field, and clearly represents blood flow through physical state changes and can reflect the coagulation mechanism, which makes a necessary complement to the deficiencies in experimental and molecular simulation studies.…”