SKEWNESS OF INSTANTANEOUS MITRAL TRANSANNULAR FLOW-VELOCITY PROFILES IN NORMAL HUMANS

The spatial distribution of instantaneous diastolic flow velocities ac ross the mitral annulus was studied with cardiac gated cine magnetic r esonance imaging in 10 healthy persons aged 26-46 yr. Velocity encodin g used two interleaved gradient echo pulse sequences with velocity sen sitivity in the direction of flow perpendicular to the annular imaging plane. Velocity maps were reconstructed at 30- to 43-ms intervals thr oughout diastole. Velocity-time curves and mean flow rates were determ ined in five regions of the mitral annulus using a 0.6-cm(2) measureme nt area. The spatial velocity minimum was consistently in the anterola teral commissural area, whereas the maximum was in the anterior annulu s in early diastole shifting posteromedially in late diastole. The mea n flow rate (+/-SD) averaged 18.4 +/- 8.1 ml . s(-1). cm(-2) of annula r area centrally, 18.3 +/- 7.2 ml . s(-1). cm(-2) anteriorly, 16.9 +/- 7.4 ml . s(-1). cm(-2) posteriorly, 13.0 +/- 7.7 ml . s(-1). cm(-2) i n the anterolateral commissural area, and 23.0 +/- 7.3 ml . s(-1). cm( -2) in the posteromedial commissural area (P<0.001). We conclude that mitral transannular flow shows marked spatial inhomogeneity in normal humans. The skewness of flow profiles compromises the use of local vel ocity measurements as indexes of left ventricular filling.