4D Flow MRI quantification of blood flow patterns, turbulence and pressure drop in normal and stenotic prosthetic...

To assess valvular flow characteristics and pressure drop in a variety of normal and stenotic prosthetic heart valves (PHVs) using 4D Flow MRI.

In-vitro flow phantoms with four different PHVs were studied: Medtronic-Hall tilting disc, St. Jude Medical standard bileaflet (STJM), Medtronic CoreValve Evolut R and Edwards SAPIEN 3. The valvular flow characteristics were investigated in normal and stenotic PHVs by using 4D Flow MRI.

The results showed that each valve provided a different amount of signal loss in the 4D Flow MRI. The defect size of the signal loss from each valve was 37.5 mm, 39.0 mm, 37.5 mm and 51.0 mm for the Tilting disk, STJM, SAPIEN 3 and CoreValve, respectively. The 4D Flow MRI-based estimation of the elevation of the pressure drop through the stenotic PHV using both Bernoulli-based and turbulence-based methods correlated well with the true values for the Tilting disc, STJM and SAPIEN 3 valve. However, the obstructive hemodynamics in the stenotic CoreValve was not clearly identified due to the large signal void from the long struts, resulting in a severe underestimation of the pressure drop using 4D Flow MRI.

The Tilting disc, STJM and SAPIEN 3 valves provided reasonable estimates of peak velocity, turbulence production and the corresponding pressure drop. In contrast, the large strut of the CoreValve and corresponding signal void prevented accurate measurements of the velocity and turbulence production; therefore, 4D Flow MRI prediction of the pressure drop through the CoreValve was not feasible.