Imaging protocols and methodology for assessment of MR via CMR
The ASE/ACC/AHA guidelines for the assessment of native valvular regurgitation highlight the importance of evaluating not only the severity of the regurgitant but also the hemodynamic effects the valvular lesion has on the LV as well as the left atrium.(4,9,28) Evaluating LV function and structure via cine images and flow imaging via phase contrast imaging is the cornerstone of the CMR evaluation of MR.
Initial imaging protocols for evaluating MR should follow the Society of Cardiac Magnetic Resonance (SCMR) recommendations and start with standard cine images. Steady state free-precession (SSFP) images should be taken in standard views: in the four-chamber, two-chamber and three-chamber views.
To optimize visualization of the mitral valve apparatus, a contiguous stack of cines should be taken perpendicular to the mitral valve and transect the principal line of cooptation. These should be contiguous with zero gap, and a slice thickness of 5-8 mm should be used to maximize special resolution with a goal temporal resolution of under 50 milliseconds.
Using this protocol, CMR can view the entire mitral valve interface and cooptation of the anterior and posterior leaflets along all three scallop-interfaces- from the lateral interface near the appendage, to the medial interface.
Additionally, standard cine short-axis LV imaging should be performed to evaluate LV function, but should be extended to cover the mitral valve.
In addition to cine imaging of the LV, the CMR protocol in patients with MR should include flow imaging through the aortic valve using the standard phase-contrast, velocity encoded methods. The SCMR recommendations include standard parameters for flow imaging. (4,7,10,29)