Mitral Annular Geometry

Flachskampf et al. and Kaplan et al. have shown that functional mitral regurgitation is associated with annular dilation and its reduced cyclic variation by using 3-D echocardiography.(5,6) Compared with normal subjects, the annulus in patients with functional mitral regurgitation is larger and has greater mitral annular area, longer perimeter, reduced annular height and eccentricity and increased distance between high points of the mitral annulus.

Leaflet Geometry

Using RT3D echocardiography, Kwan et al. studied the difference of mitral valve deformation between ischaemic and dilated cardiomyopathy with significant functional mitral regurgitation.(40) Mitral valve tethering has been found to be the strongest determinant of mitral regurgitation severity and the pattern of mitral valve deformation was asymmetrical in ischaemic heart disease, whereas it was symmetrical in dilated cardiomyopathy

Papillary Muscle Geometry

Several studies have been performed in an effort to elucidate a 3-D papillary muscle–mitral relationship.(41–44) The results of these studies show that medial and posterior shift of the ischaemic medial papillary muscle, measured by 3-D reconstruction, is particularly related to the development of functional mitral regurgitation.

Mitral Valve Repair and 3-D Echocardiography

Mitral valve repair has become more common in the last decade, accounting for half of the mitral valve procedures.(45) Various techniques have been proposed for valve reconstructions.(46–48) The decision of ‘how to operate’ depends on the underlying pathology of the mitral valve diagnosed by pre-operative echocardiography. Conventional 2-D echocardiography is a useful guide for accurate surgical analysis; however, in complex valvular pathologies some spatial relations and different structural features can be perceived erroneously even by experienced echocardiographers. The technique of repair is consistently modified in the operating room by close examination of the mitral valve, although the surgeon is challenged by limited time, operating field and non-physiological condition of the heart being devoid of blood. 3-D echocardiography has the potential to overcome these difficulties by showing the heart in the ‘surgeon’s view’ and even in a more physiological state as in operation.

There are few published data regarding the feasibility of 3-D echocardiography in the operating theatre. Abraham et al. demonstrated that, in 25% of cases, 3-D echocardiography can detect new morphologic findings (mainly valve fenestrations) not seen with 2-D TOE. In one patient, 3-D TOE resulted in a decision to perform valve repair instead of replacement. As previously mentioned, 3-D TOE has been proven as accurate in identifying the location of the prolapsing segment and quantifying the amount of the prolapsed tissue by measuring the area or the width. This information could aid the surgeon in deciding the extent of mitral valve resection.

Conclusion

3-D echocardiography allows visualisation of the heart differently to 2-D echocardiography, as it looks at the heart in true reality. The assessment of the morphology, function and pathology of the heart, and particularly the mitral valve apparatus by 3-D echocardiography, becomes more accurate. Compared with 2-D echocardiography, 3-D echocardiography offers advantages for the morphologic and quantitative assessment of mitral valve stenosis, prolapse and regurgitation. It appears that 3-D echocardiography has the potential for planning operations and assessing interventional or surgical results. Furthermore, 3-D echocardiography provides new quantitative indices unobtainable by conventional 2-D imaging. Both technical improvement and larger studies will enhance the clinical applicability of 3-D echocardiography in the near l'efuture.