It is essential to demonstrate origin of the left coronary artery from the aortic root in all patients with the clinical picture of pure mitral regurgitation, bearing in mind that, in patients with a pericardial effusion, the transverse sinus of the pericardium may be mistaken for the left coronary artery by the inexperienced observer If not diligently sought, anomalous origin or atresia of the left coronary artery may well be missed With the advent of color-flow Doppler, in conjunction with a measurement of the right coronary artery,51,52 it is now rare to miss the diagnosis An imperforate mitral valve may be recognized as a thin, sometimes mobile membrane between the left atrium and left ventricle, which can usually but not invariably be distinguished from the thick wedge produced by the atrioventricular groove when the left atrioventricular connection is absent In other cases, the mitral valvar regurgitation can be caused by dysplastic leaflets that are relatively immobile, thus preventing full coaptation during systole (Fig 34.24) From personal experience, the mural leaflet seems to be involved more frequently in this process.53 FIG 34.24 Cross-sectional image and color Doppler in a patient with dysplastic mitral valvar regurgitation There is no coaptation (arrow); however, a large vertical jet of regurgitation with a predominant annular dilation is seen The left atrium (LA) is ectatic LV, Left ventricle Pulsed and Continuous-Wave Doppler Echocardiography Doppler echocardiography has had a major impact on the evaluation of mitral valvar disease in the areas of both stenosis and regurgitation With mitral valvar stenosis, a turbulent inflow jet is seen both by pulsed and continuous-wave Doppler The latter modality can be used to calculate the gradient across the valve and also its area In adults and older patients, the pressure half-time provides an accurate assessment of area independent of cardiac output This same technique can be applied to children, although absolute areas calculated in this way are of little value because of the wide variation in body surface area.54 Mean gradients across the valve, as assessed using color-flow images, have traditionally been used in the assessment of congenitally malformed hearts (Fig 34.25) despite the limitation of their dependency on cardiac output.54 A combination of pressure half-time, mean mitral gradient, and left atrial size assesses the severity of congenital mitral valvar stenosis This, in conjunction with an assessment of pulmonary arterial pressure, either resulting from tricuspid regurgitation or pulmonary insufficiency, completes the hemodynamic evaluation FIG 34.25 Continuous-wave tracing showing the flows across a stenotic mitral valve Using this trace, it is possible to calculate the mean gradient across the valve Although pulsed Doppler flow mapping has fallen from grace in assessing the severity of mitral regurgitation, it still plays a small semiquantitative role through the use of pulmonary venous sampling In general, reversed systolic flow in the pulmonary veins is seen in hearts with more severe regurgitation.55 A quantitative measurement of regurgitant volume and fraction can be obtained using pulsed Doppler techniques This is achieved by calculating the difference between forward stroke volume through the aorta and that measured through the mitral valve, the latter consisting of normal pulmonary venous return plus the regurgitant volume.56 The contribution of color-flow Doppler in this lesion is twofold First, it excludes or establishes associated regurgitation and, second, it pinpoints the site of obstruction and the pattern of flow through the valve (Fig 34.26) In patients with an associated supramitral ring, the variance starts just above the annulus In the other forms, it starts below the level of the annulus This technique also provides valuable clues about the site of exit of the blood In a parachute valve, for example, there appears to be a conical jet of blood, whereas in those with two papillary muscles, the jet is more dispersed Assessment of mitral valvar regurgitation is well suited to the technology of color-flow Doppler This technique permits an accurate assessment of the site of the regurgitant jet, for example, from the edges of a cleft mitral valve or at the site of prolapse in those with floppy leaflets It also provides information regarding the direction of the jet, along with the extent to which the velocity signal can be observed in the left atrium One of the major problems, however, is that mapping of flow provides only a semiquantitative assessment of the severity of the regurgitation, as the echocardiographer measures velocity, not volume Despite this limitation, a reasonably reliable assessment of severity is possible, particularly if more than one plane is used Limitations relate to depth, position of the jet in relationship to the atrial wall, gain settings, driving pressure, and transmitted frequency.57,58