Functional anatomy of normal mitral valve-left ventricular complex by real-time, three-dimensional echocardiography

A detailed anatomic examination of the mitral valve (MV)-left ventricular (LV) complex (annulus, leaflets, chordae, papillary muscles, and ventricular wall) is needed for the accurate assessment of functional mitral regurgitation, and for planning patient-specific valve repair. In the past, normal values for the various components of the MV-LV complex have been derived from two-dimensional echocardiography (2DE), but such measurements require unconventional image planes and allow no off-line adjustments. In addition, measurement of the LV volumes and dimensions of irregular structures (mitral annulus) is more accurate by using three-dimensional echocardiography (3DE). The study aim was to assess, quantitatively, the MV-LV complex by real-time 3DE in normal adults.

The components of the MV-LV complex were measured off-line at mid-diastole (anterior MV leaflet), end-diastole and end-systole, after full volume real-time 3DE data sets had been obtained using a matrix transducer in 10 normal adults (six females, four males; mean age 25 +/- 5 years; range: 18-35 years; mean body surface area 1.8 +/- 0.2 m2). 2DE measurements were made for comparison.

The 2DE measurements were systematically smaller (1-12%) than 3DE measurements, due to a foreshortening of the various components of the MV-LV complex during 2DE imaging. By 3DE imaging, MV competence in normal hearts was achieved by systolic reduction in the LV volume (58%), LV length (17%), inter-papillary muscle distance (39%), annular diameter (6% anteroposterior, 14% mediolateral), and the length of both papillary muscles (21-31%). At end-systole, the anterior MV leaflet was 20% shorter (2.5 +/- 0.3 versus 2.0 +/- 0.3 cm), due to folding at the coaptation point.

These data provide normal real-time 3DE reference values for the MV-LV complex. 3DE appears superior to 2DE for accurate functional assessment of the MV-LV complex.