The mitral valve was the first structure to be identified by echocardiography (figure 1) [1,2]. Technical advances have enabled echocardiography to identify almost any anatomic or functional abnormality of the mitral valve. The appearance of the normal mitral valve and the more commonly encountered mitral valvular abnormalities will be reviewed here.
NORMAL MITRAL VALVE
A standard transthoracic echocardiographic examination (TTE) of the mitral valve consists of an M-mode tracing, multiple two-dimensional views, and Doppler flow evaluation. If clinically indicated (eg, technically difficult TTE or evaluation of prosthetic paravalvular leak), a transesophageal echocardiogram (TEE) may be performed. Together, these elements form an integrated examination of the mitral valve that can reliably define its function and evaluate the severity of abnormalities .
Anatomically, the orientation of the anterior leaflet of the mitral valve places this broad surface toward the anterior chest wall, making it an ideal sound reflecting target. Furthermore, because of its relatively large margin-to-base ratio, the anterior leaflet is highly mobile (figure 2).
The mitral valve can be recorded by ultrasound through a variety of anatomic windows in the precordium, apical, and subxiphoid regions, all of which should be used in its examination.
M-mode echocardiogram — The M-mode examination is performed from the precordium and guided from the two-dimensional long and short axis views. Normally, the anterior mitral leaflet exhibits a motion pattern that reflects the phasic nature of ventricular filling and produces a familiar M-shaped pattern (figure 3). The posterior leaflet moves in a nearly mirror image "W" pattern with a smaller excursion.