Introduction

Although echocardiography is the imaging modality of choice for cardiac heart valves, it still has significant limitations when imaging prosthetic cardiac valves. These limitations are significant with bioprosthetic valves and are particularly problematic with mechanical valves. The classic limitation is the inability to evaluate mitral regurgitation (MR) from the apical window in patients with mechanical prosthetic valves because of reverberation artifacts and acoustic shadowing. Many of these limitations, particularly while imaging the mitral valve (MV), are overcome by transesophageal imaging; direct imaging from the left atrial side of the valve eliminates these shadowing artifacts, which reside on the ventricular aspect of the valve (Figure 8-1; Video 8-1). Sparse data exist regarding the use of real-time three-dimensional transthoracic echocardiography (RT3DTTE) with prosthetic valves, although in a small series of four patients with endocarditis, vegetations and/or dehiscence not recognized by two-dimensional (2D) TTE were seen.¹ Evaluation of prosthetic valves by RT3D transesophageal echocardiography (TEE) has been extensively reviewed.^2,3 In one study, RT3DTEE has been shown to be particularly accurate for diagnosing all types of prosthetic valve pathology compared with direct surgical inspection.⁴ However, MV visualization, particularly valve leaflet visualization, was far superior to that of aortic or tricuspid valves. Also in this study, most of the valves were free of disease and, in fact, had recently been placed. Despite being a study of 87 patients, fewer than 40 had prosthetic valves, and the number who had metallic prosthetic valves is not clear from the report.

Figure 8-1 Two-dimensional mid-esophageal image of a mechanical double-tilting-disk mitral valve prosthesis captured in the closed position during systole. The image clearly illustrates the characteristic V pattern produced by the occluding disks.

A notable advantage of RT3DTEE compared with 2DTEE for all mechanical valves in the mitral position is the ability to visualize the entire valve in one full-volume or 3D zoom capture compared with visualization of only a single thin slice by 2D (Figures 8-1 to 8-6; Videos 8-1 to 8-6). Besides live 3D imaging, RT3DTEE has the ability to acquire a 3D volume that can then be cropped and rotated to reveal pathology such as leaflet immobility, thrombi or vegetations, dehiscence, or, with the addition of 3D color, even small perivalvular leaks (see Figure 8-4 and Video 8-4). Details of the valve, such as the sewing ring, the individual stitches, the struts, and the entire leaflet motion are well visualized by RT3DTEE (see Figure 8-6 and Video 8-6). Again, such visualization is much less frequently seen in valves in either the aortic or tricuspid position.

Figure 8-2 En face view of a mechanical double-tilting-disk mitral valve prosthesis captured in the open position during diastole. The image clearly illustrates the sewing ring and the two disks.

Figure 8-3 Two-dimensional echocardiographic image of a stented bioprosthetic valve in the mitral position.

Figure 8-4 Ventricular aspect of a stented bioprosthetic valve in the mitral position imaged with three-dimensional transesophageal echocardiography.

Figure 8-5 Two-dimensional mid-esophageal short-axis view of a 23-mm bioprosthetic aortic valve (PERIMOUNT Magna, Edwards Lifesciences, Irvine, CA) in the closed position. The image depicts the three stents at the commissural points.

Figure 8-6 Three-dimensional mid-esophageal en face view of a 23-mm bioprosthetic aortic valve (PERIMOUNT Magna, Edwards Lifesciences, Irvine, CA) in the closed position. The image depicts the three stents at the commissural points as well as the closure line of the three leaflets.

Abnormal Pathology with Mechanical Valves

Visualization of masses or the pannus on mechanical valves by RT3DTEE has not been rigorously studied because such problems are relatively uncommon. Only case reports exist of pannus formation on bileaflet mechanical valves in the mitral position evaluated by RT3DTEE, but in one published case, the pannus was identified by RT3DTEE and not seen at all by 2DTEE.⁵ Thrombus formation can be more precisely evaluated by RT3DTEE than by 2DTEE; in fact, this has confirmed our observation of the ability of RT3DTEE to appreciate that thrombi are larger and more numerous than thrombi detected by 2DTEE.^6,7

Guidance of Percutaneous Valve Placement

TEE is the standard for guiding percutaneous transcatheter aortic valve implantation. Data regarding the use of RT3DTEE for this particular procedure are limited, although it is routinely performed.¹⁰ Several potential advantages exist for RT3DTEE in this setting. The third dimension allows (1) more accurate assessment of the aortic annulus, the left ventricular outflow tract, and the aortic root size and shape; (2) measurement of the distance between the annulus and the left main coronary artery ostium; and 3) seating of the percutaneous valve while viewing the aortic valve en face and visualizing the valve leaflets and the tissue surrounding the prosthetic annulus.¹¹ This en face view is critically important for placement of the prosthetic valve to avoid postprocedure perivavluar regurgitation. RT3DTEE and biplane imaging also assist with the perioperative monitoring of all procedural aspects, including advancements of guidewires into the aortic valve and the placement of pigtail catheters in the sinus of Valsalva and the left ventricle, as well as balloon valvuloplasty or valve deployment. Ultimately, 2DTEE and RT3DTEE should be used as complementary imaging modalities to assess the satisfactory positioning and function of the implanted valve.

Reports of small series of transcatheter mitral valve-in-valve implantations have appeared in the literature. RT3DTEE has also been routinely used for this purpose.¹² Although this procedure is currently not available in the United States, RT3DTEE will be a mainstay for deployment of mitral valve-in-valve devices when they do become available.