Abstract
Systolic Anterior Motion (SAM) of the mitral valve – often associated with Hypertrophic Obstructive Cardiomyopathy (HOCM) – is a cardiac pathology in which a functional subaortic stenosis is induced during systole by the mitral leaflets partially obstructing the outflow tract of the left ventricle. Its assessment by diagnostic tests is often difficult, possibly underestimating its severity and thus increasing the risk of heart failure. In this paper, we propose a new computational pipeline, based on cardiac cine Magnetic Resonance Imaging (cine-MRI) data, for the assessment of SAM. The pipeline encompasses image processing of the left ventricle and the mitral valve, and numerical investigation of cardiac hemodynamics by means of Computational Fluid Dynamics (CFD) in a moving domain with image-based prescribed displacement. Patient-specific geometry and motion of the left ventricle are considered in view of an Arbitrary Lagrangian–Eulerian approach for CFD, while the reconstructed mitral valve is immersed in the computational domain by means of a resistive method. We assess clinically relevant flow and pressure indicators in a parametric study for different degrees of SAM severity, in order to provide a better quantitative evaluation of the pathological condition. Moreover, we provide specific indications for its possible surgical treatment, i.e. septal myectomy.
Highlights
Systolic Anterior Motion (SAM) is a pathological condition of the heart where the anterior leaflet of the mitral valve is displaced towards the septum narrowing the Left Ventricle Outflow Tract (LVOT)
The results presented are threefold: 1. in Section 4.1, we report the outcome of the reconstruction pipeline described in Section 2, that provides the endocardium displacement dMRI and the configurations of the mitral valve Γ for different levels of SAM severity; 2. in Section 4.2, the effect of SAM severity on hemodynamic quantities is assessed by means of Computational Fluid Dynamics (CFD) results; 3. in Section 4.3, we focus on some specific quantities in order to provide useful indications for the design of septal myectomy, a possible surgical treatment for the patient’s condition
The blood flow in the prescribed moving domain has been modeled with Navier–Stokes equations in Arbitrary Lagrangian–Eulerian (ALE) form, enhanced with a resistive method to represent the immersed mitral valve
Summary
Systolic Anterior Motion (SAM) is a pathological condition of the heart where the anterior leaflet of the mitral valve is displaced towards the septum narrowing the Left Ventricle Outflow Tract (LVOT). The motion of the ventricle endocardium and of the mitral leaflets are reconstructed from cine-MRI data and employed to deform the computational domain and to prescribe boundary conditions to the blood flow model In this way, the proposed computational framework: (i) avoids modeling the valve dynamics and myocardium mechanics, considerably reducing the computational effort; (ii) embeds patient-specific geometric and functional data without any prior assumption on the model parameters; (iii) avoids the modeling of the leaflets mechanics and the complex numerical treatment of an FSI problem; (iv) hinges upon standard image data routinely acquired in current clinical practice.
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