The Role of Imaging of Flow Patterns by 4D Flow MRI in Aortic Stenosis

Aortic valve stenosis (AS) is the most prevalent valvular heart disease in developed countries and is associated with the development of severe secondary complications such as aortic dilatation and aneurysm. Emerging evidence suggests that the modified hemodynamic environment associated with AS can cause altered flow patterns in the ascending aorta associated with aortic wall remodeling and development of aortopathy. Recent advances in magnetic resonance imaging (MRI) allow for the comprehensive visualization and quantification of in vivo aortic flow pattern dynamics. In particular, the technique of 4-dimensional flow MRI offers the opportunity to derive advanced hemodynamic measures such as vorticity and helicity, wall shear stress, flow displacement, pressure gradients, viscous energy loss, and turbulent kinetic energy. This review introduces 4-dimensional flow MRI for blood flow visualization and quantification of hemodynamic metrics in the setting of aortic valve disease, with a focus on AS and associated secondary aortopathy.