Accurate quantitation of regurgitant volume with MRI in patients selected for mitral valve repair.
OBJECTIVE
Echocardiography, the currently preferred diagnostic approach for mitral valve regurgitation, cannot accurately quantify the amount of regurgitation. Flow quantification with MRI is possible, but the conventional method (1-directional velocity-encoding) acquires the flow at a fixed location during the cardiac cycle, which is not necessarily the location of the mitral valve during the whole cycle. In this study, the exact flow through the mitral valve was quantified with a 3-directional velocity-encoded MRI approach.


METHODS
Ten patients with severe mitral valve regurgitation (class 3-4+with echocardiography) resulting from systolic restrictive motion of both leaflets (Carpentier IIIb) which were selected for valve repair and 10 healthy volunteers without cardiac valvular disease confirmed with echocardiography were included in this study. The intra-ventricular flow was sampled with a radial stack of six acquisition planes parallel to the long-axis of the left ventricle. Three-directional velocity-encoded MRI was performed resulting in the intra-ventricular flow velocity vector field for 30 phases during the cardiac cycle. The position of the mitral valvular plane in this vector field was indicated manually for each phase. Velocity values perpendicular to this plane determined the flow through the mitral valve. Both the 3-directional encoded mitral valve flow and the 1-directional encoded mitral valve flow were compared with the flow determined with MRI at the ascending aorta.


RESULTS
One-directional velocity-encoded MRI showed a mean overestimation (P<0.01) of 25 ml/cycle compared to the aortic flow. Correlation was very poor (r(P)=0.15, P=0.68). The 3-directional velocity-encoded MRI on the other hand, showed no over/underestimation and a good correlation (r(P)=0.91, P<0.01 for volunteers, r(P)=0.90, P<0.01 for patients). The regurgitant flow fractions were between 3 and 30%.


CONCLUSIONS
With 3-directional velocity-encoded MRI, measurement of the flow through the mitral valve is accurate and reproducible. This is a valuable tool for diagnosing and absolute quantification of regurgitant volume.
Westenberg
Jos J M
JJ
Division of Image Processing, Departments of Radiology, Cardiology and Cardio-thoracic Surgery, Leiden University Medical Center, 2333 ZA Leiden, The Netherlands. j.j.m.westerberg@lumc.nl
Doornbos
Joost
J
Versteegh
Michel I M
MI
Bax
Jeroen J
JJ
van der Geest
Rob J
RJ
de Roos
Albert
A
Dion
Robert A E
RA
Reiber
Johan H C
JH
D000328:Adult; D000368:Aged; D001783:Blood Flow Velocity; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008875:Middle Aged; D008943:Mitral Valve / Q000503:physiopathology* / Q000601:surgery; D008944:Mitral Valve Insufficiency / Q000503:physiopathology* / Q000601:surgery*; D011300:Preoperative Care / Q000379:methods; D012039:Regional Blood Flow; D015203:Reproducibility of Results