Heart valve disease
The evaluation of heart valve disease using 3D echocardiography has been validated in different studies. To date, the best documented have been diagnostic studies of pathological mitral valves
(9) – (12). During the last decade, there has been a change in the surgical treatment of mitral valve disease. New surgical techniques have enabled the repair of mitral defects in many patients who would previously have had to have valve replacement. Reparative surgery of this kind requires a very high degree of precision in diagnostics of the mitral valve’s form and function, to enable the correct surgical method to be employed. In our own department, we use 3D echocardiography to investigate patients with mitral valve regurgitation, to enable us to locate exactly the damage to the valve (Figure 2). We have benefited especially from the so-called «surgeon’s view» from the left atrium, where the entire mitral valve can be represented in the same image as shown in Figure 2.
Figure 2 Transthoracic recording of the mitral valve viewed from the left atrium («surgeon’s view»). The white arrowhead marks prolapse of the posterior mitral valve seal, which comprises the medial and posteromedial thirds (P2 and P3, respectively).
Currently, two-dimensional transoesophageal echocardiography is required in order to determine which surgical technique is desired to treat mitral valve prolapse. Interestingly, it was recently demonstrated that 3D external echocardiography (transthoracic) was equally as good as 2D transoesophageal echocardiography in localising mitral valve prolapse
(10). Three-dimensional transoesophageal echocardiography was even more precise in assisting diagnosis of commissural prolapse, which can be difficult to repair. This is important information to have when planning which surgical method is the more appropriate as regards artificial valve versus valve-preserving, reparative surgery. Three-dimensional echocardiography is now routinely performed at a number of European cardiac surgical centres prior to plastic repair of the mitral valve.
Quantitation of regurgitation is also an important part of the diagnostic picture in patients with mitral valve regurgitation. Two-dimensional colour Doppler has clear weaknesses in these diagnostics. Studies show that 3D colour Doppler echocardiography is a more robust measurement for estimating valve regurgitation and calculating the effective regurgitant orifice area (EROA)
(13, 14). Three-dimensional colour Doppler echocardiography offers unique possibilities for multiple-plane imaging of vena contracta. A simple technique permits planimetry of the area corresponding to the vena contracta (14, 15).
Several studies have been produced on the assessment of aortic valve stenosis using both direct planimetry
(16) – (19) and with 3D colour Doppler echocardiography for determination of stroke volume and derivation of the area with continuity equation (16, 20). Particularly in the presence of septal bulging, which is common among the elderly, the latter method was more precise than using conventional 2D echocardiography (20). Three-dimensional echocardiography also enables quantitation of aortic insufficiency, where two-dimensional echocardiography currently has evident weaknesses (18).
With new techniques, such as percutaneous procedures to treat valve disease (implantation of artificial aortic valve) and repair of mitral valve regurgitation using a transcatheter technique (MitraClip), 3D echocardiography will have a central place in cardiac procedures
(21). In the next few years, 3D echocardiography may also be used to assist new percutaneous techniques, not only MitraClip. Techniques are currently being developed (in animal models) for other purposes such as replacement/repair of mitral valve chords and insertion of mitral rings and new percutaneous mitral valves.
In patients with mitral stenosis, the method has also proved to be more precise than the techniques used routinely today
(12, 22) – (24). The advantage of 3D echocardiography is the opportunity it offers for defining the image plane «en-face» through the smallest orifice area of the stenosis, so that the true stenosis area can be estimated more precisely.
We have also found 3D echocardiography useful in patients with residual mitral regurgitation after mitral valve surgery. In paravalvular regurgitation, a good overview can be obtained of the localisation and extent of the regurgitation. Other clinical problems for which we employ 3D echocardiography are in diagnosing endocarditis. In addition to more precise localisation, it enables a better overview of the extent of abscesses and any fistula formation (Figure 3).
Fig 3 Transthoracic recording in patient with aortic valve endocarditis. The yellow arrowhead marks valvular vegetations and the white arrowhead the abscess cavity in the aortic root anteriorly.