Synergy between Diastolic Mitral Valve Function and Left Ventricular Flow Aids in Valve Closure and Blood Transport during Systole

Vijay Govindarajan,Krishnan B Chandran,Sarah C Vigmostad,John Mousel,H S Udaykumar,David D Mcpherson,Hyunggun Kim

doi:10.1038/s41598-018-24469-x

Vijay Govindarajan, Krishnan B Chandran + Show 5 more

Open Access

https://doi.org/10.1038/s41598-018-24469-x

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Abstract

Highly resolved three-dimensional (3D) fluid structure interaction (FSI) simulation using patient-specific echocardiographic data can be a powerful tool for accurately and thoroughly elucidating the biomechanics of mitral valve (MV) function and left ventricular (LV) fluid dynamics. We developed and validated a strongly coupled FSI algorithm to fully characterize the LV flow field during diastolic MV opening under physiologic conditions. Our model revealed that distinct MV deformation and LV flow patterns developed during different diastolic stages. A vortex ring that strongly depended on MV deformation formed during early diastole. At peak E wave, the MV fully opened, with a local Reynolds number of ~5500, indicating that the flow was in the laminar-turbulent transitional regime. Our results showed that during diastasis, the vortex structures caused the MV leaflets to converge, thus increasing mitral jet’s velocity. The vortex ring became asymmetrical, with the vortex structures on the anterior side being larger than on the posterior side. During the late diastolic stages, the flow structures advected toward the LV outflow tract, enhancing fluid transport to the aorta. This 3D-FSI study demonstrated the importance of leaflet dynamics, their effect on the vortex ring, and their influence on MV function and fluid transport within the LV during diastole.

Highlights

Interventricular hemodynamics, the effects of the fast-moving mitral valve (MV) leaflets in response to physiologic blood flow conditions remain elusive[9]
Our 3D-Fluid structure interaction (FSI)-predicted MV deformation during early rapid filling and fluid dynamics in the left ventricular (LV) during late diastole were qualitatively consistent with those of previous clinical MRI studies, demonstrating that our model can capture the significant features of MV function and LV fluid dynamics (Fig. 3)[42,43]
The interaction of the blood flow with the rapidly opening MV leaflets and the expanding LV wall resulted in highly complex fluid dynamics

Summary

Introduction

Interventricular hemodynamics, the effects of the fast-moving MV leaflets in response to physiologic blood flow conditions remain elusive[9]. Kunzelman’s group developed FSI models of the MV to analyse the hemodynamic determinants of MV closure sound, MV deformation, and leaflet and chordal stresses[16,17,18], but assumptions such as blood being compressible with reduced bulk modulus for computational efficacy, symmetric boundary conditions, coarse mesh to discretize the fluid domain, and lack of LV made the simulations non-physiological. They performed an FSI study using an ovine MV model to evaluate the MV opening and closing and analyse the chordal forces[19]. Our model revealed important information on fluid and solid dynamics during diastole that closely corresponded to the results of previous clinical MRI studies

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Discussion

Conclusion