Precise characterization of the mitral valve is crucial for guiding the management of patients with mitral valve prolapse. From watchful monitoring to valve repair or replacement, different options may be considered on the basis of the assessment of the grade and mechanism of the regurgitation, the precise description of the abnormal valve, and the possibility of repair. Echocardiography remains the examination of choice for such evaluation: it is safe, and it is performed and interpreted in real time under normal hemodynamic conditions. On the other hand, echocardiographic evaluation of the mitral valve is complex and requires advanced operator training and experience to provide an accurate three-dimensional (3D) analysis of the valve. With experience, this analysis is usually achieved from multiple two-dimensional (2D) images, mentally reconstructed to form a 3D image. Using 3D technology, 3D volumetric data sets of the mitral valve are directly acquired and visualized, facilitating comprehensive understanding of the mitral valve anatomy and dynamics. This thorough valve analysis is essential for therapeutic decisions. It allows one to predict the feasibility of mitral valve repair, the optimal surgical technique, and its expected complexity. In addition to providing a better description of the mitral valve, the self-explanatory nature of the 3D images allows less experienced operators to visualize the whole mitral valve during real hemodynamic conditions.

In this issue of JASE , on the basis of those premises, Hien et al. report their evaluation of whether the known benefit of 3D over 2D transesophageal echocardiographic (TEE) imaging for the evaluation of mitral valve prolapse would persist among novice echocardiographers.

The authors selected six cases of mitral valve prolapse with severe mitral regurgitation, from whom expert operators had acquired 2D and 3D TEE images during mitral valve surgery. These six cases represented a large spectrum of mitral valve prolapse diversity, from the most common to the most complex diseases encountered. They asked 15 experts and 21 novices in TEE imaging to interpret blindly, offline, both sets of 2D and 3D TEE images. As expected, both groups of readers provided more accurate descriptions of the mitral valve prolapse with 3D than with 2D TEE images. But the most interesting and surprising result of this study was that this benefit was 3 times more important for inexperienced echocardiographers than for experts. A small difference remained between the two groups’ accuracy in analyzing images of mitral valve prolapse, but this difference was no longer significant when using 3D data sets. Furthermore, the beginners’ score with 3D TEE imaging (29.7 of 36) reached and even slightly exceeded the experts’ score on the basis of review of 2D TEE images only (28.3 of 36). In addition to the description of mitral valve prolapse, the authors assessed the accuracy of the physician reviewers in interpreting mitral chordal rupture. Both experts and novices significantly benefitted from 3D compared with 2D TEE images, but this benefit was greater for experts than for beginners for the detection of chordal rupture, unlike for the description of mitral valve prolapse. The difference in interpretation accuracy between the two groups was greater with 3D than with 2D TEE imaging.

On the basis of these results, Hien et al. concluded that the benefit of 3D technology observed in experts also applied to physicians who were just beginning their training in TEE imaging. For the description of mitral valve prolapse, novices seemed, to a certain extent, to make up for their lack of experience by using 3D technology.

This study is interesting in many ways. First it confirms that 3D TEE images provide better understanding of the mitral valve than 2D TEE images. By using 3D TEE images, novices can bypass the step of mental reconstruction from 2D images and describe mitral valve prolapse more accurately. Using 3D TEE images allows less experienced echocardiographers to reach interpreting scores close to experts’ scores using 2D TEE images only. These results open a new perspective in the yield of 3D echocardiography, as a means to increase inexperienced readers’ accuracy for the description of mitral valve prolapse. A possible explanation may be that the capability of 3D analysis from 2D images depends not only on experience but also on individual video spatial orientation skills. For the localization of prolapse only, the importance of experience may be reduced, because the mitral valve is already presented as a 3D image ideally oriented. From these results, it can be suspected that 3D echocardiography could facilitate the learning process for mitral valve evaluation, by making spatial orientation easier. Traditionally, beginners learn 2D echocardiographic views first and, as they gain experience, start using 3D imaging to refine their interpretation and for more complex cases. But the mitral valve is a 3D structure, and its analysis is more difficult when using 2D images than 3D volumes. By directly using 3D acquisitions, it is actually easier to understand the overall structure of the valve and the significance of 2D images. Of potential interest in the learning process, the multiplanar reconstruction mode allows the creation of three orthogonal 2D planes from a 3D volume. These planes can be manipulated in any direction, in relation to the 3D volume, to analyze the structures in the three dimensions. Although all spatial dimensions are used to guide the images, their analysis and interpretation are made from 2D images. This approach may help beginners understand spatial orientation and use both 2D and 3D images to provide an accurate description of mitral valve prolapse.

In addition to image interpretation, echocardiographers should be proficient in the acquisition of optimal 2D and/or 3D TEE images. Unfortunately, Hien et al. could not assess this skill set in this study, because of practical issues, and they acknowledge this limitation in their discussion. They postulate that including this step would increase the benefit gained from 3D TEE, because the evaluation of the mitral valve from 2D TEE images requires a careful acquisition of several different views, with many different transducer manipulations, including probe advancement, flexion, and multiplane rotation. We do not totally agree with this statement. The acquisition, cropping, and manipulation of 3D images require a different but equally important skill set compared with 2D imaging. The operator has to choose between different acquisition modes (live or full volume), crop the images on the region of interest while maintaining an adequate frame rate, optimize the image color scale and gain, and, most important, orient the image correctly. The 3D TEE data set is initially displayed across the left atrium, mitral valve, and left ventricle. It must be cropped and reoriented to visualize the mitral valve from the surgeon’s perspective (i.e., from the left atrium) for analysis. The orientation of the image in the three dimensions is an important step, which may jeopardize the analysis of the whole valve. The time and expertise needed for this task have never been evaluated and may be significant in untrained hands. This would have to be balanced against the advantage of seeing the whole valve in one 3D image. Using 3D TEE technology necessitates a different skill set than 2D TEE imaging and requires a large scope of skills from immediate anatomic orientation and transducer manipulation to manipulation of 3D images. Because most of the postanalysis can be done offline, the examination time can be reduced, but the time required for postacquisition offline analysis may be significantly increased. More studies will be needed to determine if the benefit of 3D versus 2D TEE imaging persists when all the steps of acquisition, image manipulation, and interpretation are included.

Another limitation of this study is the artificial separation between 2D and 3D analysis. In real life, 3D images are neither acquired nor interpreted by themselves, without using 2D images. Both imaging modalities are not mutually exclusive but complementary, and they provide different types of information. Two-dimensional images are usually used for guidance of 3D TEE acquisitions. Two-dimensional images have better temporal and lateral resolutions and give more anatomic details on small mobile structures such as ruptured chords. Three-dimensional images help visualize the whole mitral valve and determine the location and movements of each structure in relation to adjacent ones, of the mitral leaflets in relation to the annulus, for example. The benefit gained from each imaging modality is not separate but synergistic, and a thorough analysis requires constant back-and-forth between both modalities. In addition, this comprehensive anatomic analysis of the mitral valve is improved by integrating hemodynamic parameters using Doppler. Color Doppler helps determine the origin and direction of the regurgitation jet, to understand the mechanism of mitral valve prolapse and the hemodynamic consequences of each abnormality. In the future, the same advantages of 3D imaging may be applied to color images and improve the quantification and description of the mitral regurgitation. But currently, 3D color data sets are still very challenging to interpret because of their limited sector and temporal resolution.

In conclusion, should every echocardiographer buy high-end ultrasound platforms and 3D transesophageal transducers to improve his or her analysis of the mitral valve? If universal access to 3D were possible, it might improve the accuracy of mitral valve assessment at all levels of operators’ expertise and facilitate the echocardiographic learning process. But unfortunately, cost is still a significant limitation to widespread use of 3D TEE imaging. Technologic advances are still needed to improve 3D temporal resolution or color analysis. As suggested by the analysis of ruptured chords, 3D technology still provides more benefits to experts than to novices for evaluation of subtle structures. Furthermore, 3D echocardiography per se does not solve all the challenges of the mitral valve. Even with 3D transesophageal echocardiography, imaging expertise and clinical experience are still extremely important for the assessment of the mitral valve to determine the best therapeutic option. The description of mitral valve prolapse must be put in perspective with other parameters, such as associated valvular disease, ventricular function, and surgical possibilities of repair. As 3D imaging becomes more available, further studies will be needed to delineate the role of 3D echocardiography in the hands of inexperienced operators.