Real-time 3D echocardiography in the assessment of mitral valve disease

Rheumatic mitral stenosis

Rheumatic mitral valve stenosis still remains an important public health concern in developed countries. To define the best therapeutic strategy in patients with rheumatic mitral valve stenosis, clinical data and accurate measurements of the MVA (Mitral Valve Area) are necessary. Doppler based methods are heavily influenced by hemodynamic variables, left ventricular hypertrophy and associated valvular disease. Accordingly, methods based on direct measurement of the valvular orifice should be more accurate.

To date, direct measurements of the MVA can only be performed using a planimetry, traced on 2D echo images. However, this method has multiple limitations, the major one being the correct image plane orientation (1,2). RT3D provides a unique “en-face” view of the complete mitral valve apparatus (3,4) and has shown that it can improve the accuracy of 2D echo MVA planimetry (5). Until now, 3D echocardiography has not been routinely performed due to the cumbersome nature of older platforms, prolonged data acquisition and off-line processing time. With the advent of the new transthoracic 3D matrix array probes that allow real-time 3D rendering, many of the above limitations could be circumvented.

Compared to all other echo-Doppler methods, RT3D agrees best with the invasively determined MVA, the usual gold-standard. Furthermore, RT3D provides a similar interobserver variability when compared to the pressure half-time method and shows a better interobserver agreement than 2D echo for the assessment of the pre-valvuloplasty Wilkins score (5,6).

RT3D has also shown its superiority in evaluating the MVA in the most difficult scenario for the traditional non-invasive methods: the immediate post-valvuloplasty period. Directly following a percutaneous mitral valvuloplasty, the pressure half-time method has been shown to have a poor agreement with invasive data (7). There are various reasons for this inaccuracy including the development of an atrial septal defect in many patients after the valvuloplasty, and the fact that the pressure half-time method assumes that left atrial and left ventricular compliances remain stable; this assumption is not valid in the immediate period following a percutaneous valvuloplasty because rapid changes in the left atrial pressure and left ventricular filling occur in this setting, affecting the compliance of both the left atrium and ventricle. The RT3D MVA assessment better agrees with the invasively derived MVA before and in the immediate post-valvuloplasty period (8).

Thus, we can conclude that RT3D is a feasible and accurate technique for measuring MVA in patients with rheumatic mitral valve stenosis and that it is still useful under the conditions where other non-invasive methods fail.

Mitral valve prolapse

Accurate assessment of the scallops involved in a mitral prolapse is important, mainly in those patients who are potential candidates for surgery, because this information may be crucial to evaluate their chances of valvular repair. So far, the only reliable echocardiographic technique to describe which scallops prolapse, was transesophageal echocardiography.

Off-line three-dimensional echocardiographic reconstruction of the mitral valve has been performed for many years, with excellent results (9). It has shown that using both transthoracic and transesophageal approaches, is a useful method to locate the prolapsing scallops of the mitral valve in order to guide the surgeon in his/her valvular reconstruction (10,11). 

Nevertheless, to date, 3D echocardiography has not been routinely performed due to its low cost-effectiveness ratio and the fact that it is time-consuming. With the advent of the new transthoracic 3D probes that allow real-time 3D rendering, these kind of studies could be easily performed in a short time. RT3D is a useful tool that easily provides us with information resulting from a transthoracic approach. Furthermore, the technique is very easy to acquire for doctors and technicians used to work with 2D images. They do not need elaborate training. Thus, these factors should not limit its routine use.

RT3D has shown that it is an accurate method for studying mitral prolapse for it is able to determine from a transthoracic approach which scallops are involved in the prolapse. This information is particularly relevant in patients who are potential candidates for surgical repair (12). New diagnostic echocardiographic signs for the evaluation of mitral valve prolapse are these days being described, such as the “mitral eversion” and the “pseudo-cleft” (13). The “mitral eversion” is defined as an image of negative relief of the mitral leaflets in systole respect to the annulus, observed from the left ventricle in a modified apical 3-chamber view (conventional 3-chamber view slightly tilted to include as much of the mitral annulus as possible); a normal mitral valve produces a positive relief with tent shape in this perspective. “Mitral eversion” has shown to be an accurate marker for diagnosing prolapse of all scallops in both leaflets. On the other hand, “pseudo-cleft” (defined as a line along the leaflet, from the free border to the annulus, appearing either as valvular discontinuity or as clear relief in its surface, in the paraesternal short axis view of the mitral valve or in an apical view) is a sign that represents the border between normal and prolapsing scallops.

To conclude, RT3D echocardiography allows us to perform a more complete evaluation of the mitral valve structures from different points of view. Furthermore, using this new diagnostic method, the surgeon can directly understand what is happening at the level of the mitral valve from a dynamic point of view. Finally, other kinds of diseases, such as aortic valve diseases and congenital cardiac diseases can also be accurately evaluated with RT3D.

The content of this article reflects the personal opinion of the author/s and is not necessarily the official position of the European Society of Cardiology.