Fig. 3.1
Full volume 3D four-chamber acquisition focus on the left ventricle for posterior analysis
If the entire LV is included in the volume data set, the left ventricular shape, the quantitative evaluation of volumes, and global and regional function can be measured by a 3D quantification software. This semiautomatic program requires the operators to determine reference points along the base and apex of the LV. An automatic endocardial border-tracking program then identifies and traces the endocardial border and the program calculates left end-systolic and end-diastolic volumes using a 3D deformable model without geometric assumptions [6] (Fig. 3.2).
Fig. 3.2
Full volume 3D four chamber view acquisition with off line post-processing. The program traces the end-systolic and end-diastolic endocardial borders and calculates the volumes, global and regional function without geometric assumptions
Left heart contrast administration can be used to enhance border detection in patients with poor endocardial visibility.
LV measurements:
LV volumes:
3D echocardiographic measurements of LV volumes are recommended when feasible depending on image quality.
Mitral annulus and LV apex are the points of reference used by the semiautomated quantification software to start the edge detection.
Papillary muscles and LV trabeculae should be included within LV cavity for the quantification.
LV volume is computed after the construction of a surface-rendered cavity cast of the LV.
The distance between transducer and LV does not permit, in some cases, good images of the left ventricular trabeculae from ME. In these cases, we can try to obtain images from transgastric viewpoint.
LV global and segmentary function:
In patients with good image quality, ejection fraction measurements are reproducible and should be performed when available and feasible.
A semiautomated endocardial interface algorithm performs the cavity contours and their changes during the cardiac cycle (manual corrections to the endocardial borders can be performed).
3D data allows the assessment of LV regional strain, synchrony and wall stress, but these measurements are not performed in a routine study
3D TEE data are complementary to 3D transthoracic data, which is the most common way to calculate LV systolic function.
LV mass:
Because 3D echocardiography is the only technique that measures myocardial volume in a direct way, it is an appropriate approach. However, available mass data are not sufficient to recommend normal reference values.
It could be used in abnormally shaped ventricles or in localized or asymmetric hypertrophy, but there are no validated reference values.
LV structural abnormalities:
3D TEE images can be obtained to study thrombus, inside ventricle masses or ventricular septal defect (3D Color flow mapping and visual assessment).
Right Ventricle (RV)
The RV is a functionally and structurally complex cardiac chamber. The marked trabeculation, the prominent intraventricular structures and the special shape of the RV represent a challenge for the echocardiographers [1, 7].
3D TEE is a reproducible tool to provide data about RV volumes and ejection fraction with an adequate correlation to reference standards (magnetic resonance image). However, the use of 3D echo in RV measurement is not a routine in all the echocardiographic labs.
A full volume data set should be acquired from a ME or subcostal view, making sure that the entire RV is included (Fig. 3.3).
Fig. 3.3
Multiplanar reconstruction image of the right ventricle. The 3D data set was obtained with full volume 3D from the subcostal view
The available methods used to quantify RV function include a volumetric semiautomated border detection algorithm and the methods of discs. A semiautomated border detection algorithm determinates the RV end-diastolic and end-systolic volume and the ejection fraction.
RV segmental function can be measured from the segmental analysis of the three main portions of the chamber (apex, inlet and outflow segments).
Right and Left Atria
The development of 3D TEE imaging is related to the progress of electrophysiology and the implant of percutaneous devices. 3D TEE is ideal for visualization of (LAA), pulmonary veins and the interatrial septum [2].
From ME 90° view of LAA and MV, we can obtain good images of the left pulmonary veins if we make a mild clockwise rotation. Zoom mode or narrow-angled acquisitions can be displayed [1].
Interatrial septum can be analyzed from ME view with a clockwise rotation. When viewing from the left atrium (LA), the atrial septum should be oriented with the right upper pulmonary vein at the one o’clock position; when viewing from the right atrium the superior vena cava should be located at the 11 o’clock position.
From ME (0–45–90–135°) view LAA imaging can be performed. Multiplane imaging can help to obtain information about LAA lobes. An “en face” view of the LAA orifice can be studied if we obtain a zoom mode image. 3D TEE offers an excellent estimation of LAA orifice area and useful information to choose the device’s correct size (Fig. 3.4).
Fig. 3.4
Multiplanar reconstruction mode used to measure left atrial appendage dimensions to choose the device correct size, from zoom 3D acquisition of the left atrial appendage
Devices
3D TEE offers a good orientation and spatial visualization of the different cardiac structures and intracardiac devices during catheter-based percutaneous procedures.
In most patients with pacemakers or implantable cardioverter-defibrillators we can identify with this technique, the atrial or ventricular leads position inside right chambers, and the occasional tricuspid regurgitation [8]. Thrombi or vegetations can appear as complications of a pacemaker or central catheter’s implantation. Usually, thrombus is positioned in the right atrium (RA) (the junction of the right atrium and the superior vena cava). To evaluate this kind of complications, images can be acquired using live 3D echocardiography and 3D zoom mode in a bicaval plane or in ME four chamber view (focused on right chambers), and we must display a simultaneous dual-plane visualization in order to obtain complete information of the spatial disposition.
As a further application, 3D echocardiography could be an available tool to guide the positioning of LV lead in coronary veins during biventricular pacemaker implantation.
Mitral Valve
Assessment of the mitral valve (MV) primarily requires the understanding of its complex structure and function. That correct function is reliant on the integrity and coordination of each of its components: mitral leaflets, mitral annulus and subvalvular apparatus (chordae tendinae and papillary muscles). Due to that complexity, imaging of the MV valve is one of the most challenging applications of 3D echocardiography as it has the power to provide an understanding of the mechanism of valve failure and the likelihood of a successful surgical MV repair when needed [9].
Anatomy
The MV comprises two leaflets, attached to the atrioventricular junction by the mitral annulus, and by the chordae tendinosus to the papillary muscles.
The mural or posterior leaflet is narrow but has a larger circumferential attachment occupying two thirds of the mitral annulus. It presents indentations (called clefts) along the elongated free edge, which divide the leaflet into three scallops. Carpentier’s nomenclature organizes these scallops into P1, P2 and P3 ranging from the anterolateral to the posteromedial commissure. The anterior or aortic leaflet is broader, with a cuadrangular/semicircular shape. By its attachment to the anterior third of the mitral annulus makes continuity with left and non-coronary cusps of the aortic valve (AV), and with the interleaflet triangle between the aortic cusps that abuts onto the membranous septum, making up the fibrous trigonous of the heart. For clinical purposes, it is also divided into three scallops corresponding to the opposite regions of the mural leaflet [10].
Mitral annulus is a nonplanar saddle-shaped structure with two high points (peaks) lying anteriorly and posteriorly (at the aortic insertion and posterior left ventricular wall), and two low points (troughs) closest to the apex, located medially and laterally. Its geometry is poorly understood by 2D echocardiography as it is equivalent to a hyperbolic paraboloid [9], a geometric surface where all sections parallel to one coordinate plane are hyperbolas and all sections parallel to another coordinate plane are parabolas.
Subvalvular apparatus comprises the cordae tendinae and the papillary muscles. Papillary muscles bundles are generally described in anterolateral and posteromedial positions of the LV so any impairment on left ventricular muscle (as happens in ischaemic or dilated cardiomyopathy) may contribute to MV dysfunction.
Data Acquisition
3D TEE has improved visual assessment of the MV. It provides easily understanding images without requiring probe manipulation of 2D echo, allowing a more efficient examination process.
A preliminary study of the mitral apparatus by using the 2D multiplane modality of transesophageal echocardiography is useful as a first approach to the MV. 2D images at different degrees of exploration, usually obtained at ME depth, may help us to identify the primary mechanism and aetiology of MV dysfunction.
Nevertheless, 3D echocardiography probes permit the use of a dual screen to obtain two real 2D images simultaneously by simultaneous multiplane imaging (Fig. 3.5). The first image would be a reference view of the valve, typically at ME depth (so you can assess the MV and the subvalvular apparatus), while the second image or lateral plane represents a plane rotated 30–150° from the reference one [1]. This preliminary survey must be done with and without colour flow Doppler to identify the mechanism of mitral valve dysfunction if present.
Fig. 3.5
X plane image acquisition of the mitral valve. The left hand image displays the live image. Adjusting the cursor will alter the angle of acquisition of the second image on the right hand side
Once this first approach is done, it is time for 3D images acquisition. To obtain quality 3D images, we can use the live 3D mode to optimize gain settings. Live 3D could also be useful to evaluate LV geometry and papillary muscles. In addition, it might be interesting to view the mitral apparatus in continuity with the left ventricular walls, by obtaining a real time 3D image from the entire LV after having increased depth and focus of the 2D reference image. Moreover, a real-time 3D view of the mitral apparatus could be obtained at the end of the exam from the transgastric two-chamber view to assess the papillary muscles and chordae tendineae.
Then, as we have to examine a pyramidal volume to assess the whole three-dimensional valve, we can use different acquisition modes: Live-3D, full-volume or zoom mode.
3D zoom permits a focused, wide-sector view of the MV apparatus from the annulus to the papillary muscle tips. When selected, the 3D zoom mode displays a bi-plane preview screen showing the original view and the corresponding orthogonal image (as in simultaneous multiplane mode), and it displays a sector (zoom sector) over the region of interest in both planes. Zoom sector boxes should be placed carefully and sector-width minimized to obtain the leaflets and the annulus, so we can improve temporal resolution and optimize image quality. Now, acquisition can be done, so a pyramidal volume is obtained.
The obtained volume must be reoriented to be able to assess MV structure, so it should be rotated 90° counter clockwise, around the x axis to present the valve as viewed from the LA (surgeon view), or 90° clockwise, to present it as viewed from the LV. In addition, the MV should be rotated counterclockwise in the z-plane so that aortic valve is located superiorly at the 12-o’clock position (Fig. 3.6, Video 3.2).
Fig. 3.6
3D zoom acquisition of the mitral valve and X plane display. Subsequent rotation allows visualization of the valve from the left atrium. In addition, the mitral valve should be rotated so that aortic valve is located superiorly at the 12-o’clock position
The obtained 3D dataset can be view from multiple angles and cropped in different planes to estimate the smallest true MV orifice by planimetry.
Finally, colour flow Doppler should be added to 3D morphology to exclude the presence of regurgitant jets or stenosis [3]. 3D colour Doppler acquisition could be performed using live 3D or multiple-beat full-volume acquisition. As smaller colour Doppler volumes and lower frame rates limit live 3D mode, we recommend colour full volume acquisition for MV study. As explained before, for its preparation from a dual screen with a simultaneous colour Doppler 2D–image, zoom sectors should be limited to the region of interest, placing the regurgitant jet in the center of the sector to reach a balance between the region of exploration (larger sector) and frame rate (high line density images) to obtain good and reliable images.
The 3D colour full volume data set can be rotated and cut in different planes in order to quantify the origin of the regurgitant jet as well as estimate the vena contracta and regurgitant orifice area (Fig. 3.7, Video 3.3).
Fig. 3.7
Two orthogonal views of the mitral valve following 3D zoom acquisition with superimposed 3D colour flow Doppler, to evaluate the origin of the regurgitant jet as well as estimate the vena contracta and regurgitant orifice area
As a guide to explore the mitral valve we propose the following approach:
In the first place, use the simultaneous multiplane mode at ME depth as a starting point for the exam. Optimize 2D quality images and then use the 3D live mode to modify gain settings for a better 3D image and to assess LV anatomy and subvalvular apparatus.
Use the dual reference view to prepare real time 3D zoom acquisition mode. This dual view can be obtained at 90° (two chambers view), and the second image would represent an orthogonal at 120°, (an aortic long axis view).
To continue, acquire a real time 3D zoom data set by keeping the MV in the zoom sector in both the two chamber and its orthogonal plane.
Once acquired, the image should be displayed. For that purpose, volume should be rotated around the x-axis towards the examiner, to present the valve as viewed from the LA (surgical view), or in the opposite direction if we prefer a vision from the LV. Finally, and irrespective of perspective, the AV should be placed at 12 o’clock position.
Finally, colour flow Doppler should be added to the region of interest to analyse regurgitant jets or valve stenosis. If present, detailed information is needed so we recommend to prepare real time 3D zoom acquisition with superimposed 3D colour flow Doppler. Now, region of interest (for example, the regurgitant jet) should be placed in the centre of the sector in both images of the simultaneous dual screen. The region of interest should be limited to the mitral apparatus and colour flow Doppler jet to optimize temporal and spatial resolution.
Applications
To assess the MV morphology and pathology.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
