Mitral valve regurgitation: accurate blood flow quantification with MRI

The quantification of transvalvular blood flow through the mitral valve (MV) and regurgitant flow in particular is difficult with echocardiography, which is the method of choice to diagnose patients selected for valve repair or replacement. With magnetic resonance imaging, information on the intraventricular blood flow can be obtained. Several scanning techniques have attempted to assess the regurgitant flow. These techniques either do not directly assess the complete flow through the MV, or they do not measure the flow at the location of the valve.

To investigate the accuracy of a novel method using three-directional velocity-encoded MRI to acquire the transvalvular blood flow directly from the intraventricular blood flow field, also representing the regurgitant flow during systole.

Ten volunteers without cardiac valvular disease were recruited. The transvalvular MV flow volume was measured with three-directional velocity-encoded MRI (3-dir MV flow).

The transvalvular flow measurements correlate very well with the flow measured in the aorta (r_p=0.92, p<0.01). The small differences (mean -5±7 ml) are insignificant (p=0.06) and demonstrate the high accuracy of the new method. Intra- and inter-observer studies showed non-significant mean differences of 0.9±5.1 ml and 1.3±5.6 ml, respectively, thereby proving the high reproducibility.

Three-directional velocity-encoded MRI is a patient-friendly and easy-to-use method suitable for quantifying the regurgitant MV flow in clinical practice.