Three-dimensional echocardiography (3DE) has become important in the management of patients with congenital heart disease (CHD), particularly with pre-surgical planning, guidance of catheter intervention, and functional assessment of the heart. 3DE is increasingly used in children because of good acoustic windows and the non-invasive nature of the technique. The aim of this paper is to provide a review of the optimal application of 3DE in CHD including technical considerations, image orientation, application to different lesions, procedural guidance, and functional assessment.
Introduction
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Three-dimensional Echocardiographic Imaging Techniques
Transducers
The evolution of 3DE techniques and transducer technology has been well described. The development of the matrix array probe with parallel processing has made real-time 3DE possible since the 1990s. Later generations of transducers have become smaller with footprints similar to two-dimensional echocardiography (2DE) transducers. The development of a small high-frequency pediatric 3DE transducer (2–7 MHz) has enhanced spatial and temporal resolution, especially pertinent for small children with high heart rates. Similarly, miniaturization has enabled the development of adult-size 3D transesophageal echocardiography (TEE) probes.
Workflow
Ideally, 3DE transducers should be capable of producing 2D images which are at least equivalent to 2DE transducers. Some 3D transesophageal transducers achieve this, but transthoracic 3DE probes still do not generally match the image quality of a dedicated 2D transducer. The difference remains most marked for high-frequency pediatric 3DE probes compared with the 2DE equivalent transducer. Consequently, the use of the combined 2DE–3DE transducer is not routine in smaller patients. Manufacturer recommendations suggest that current 3D TEE probes are used for patients >30 kg. Some pediatric cardiologists will extend use of such probes to smaller patients. Those undertaking such procedures should be aware of the specific manufacturer recommendation for the transducer. In any patient, the risk of complications such as damage to the oropharynx and oesophagus caused by an oversized probe needs to be balanced against the additional value of 3DE. For patients who are currently too small to accommodate 3D TEE transducers, epicardial 3D imaging with a transthoracic 3DE transducer is a feasible alternative technique during surgery.
Data Acquisition Modes
Good spatial and temporal resolution in 3DE is a priority for imaging of CHD, particularly valve pathology and complex lesions. The matrix transducer has different modalities of data acquisition whose use is dictated by the clinical question. For example, in the assessment of double outlet RV, the incorporation of the AV valves, ventricular septum, and great arteries is necessary for decision-making, whereas measuring the size of an isolated VSD does not require such an extended field of view. The exact configuration and nomenclature of different modes is vendor specific but with features in common.
2D Simultaneous Multiplane Mode
Current matrix probes allow 360° electronic rotation of the imaging plane as well as simultaneous display of more than one 2D imaging plane that can be electronically steered in the elevation or lateral plane. The crop plane is marked on the projection but with the drawback that temporal resolution is reduced. Applications include assessment of atrial septal defect (ASD) size and rim length, size and shape of VSDs, AV valve morphology and regurgitation ( Figure 1 A and B), outflow tracts and arterial valves.
Real-Time 3DE Mode
Real-time 3DE permits a display of an adjustable pyramidal volume, minimizing the issue with poor co-operation in children because there is no potential for ‘stitch’ artefacts between adjacent subvolumes. Increasing the region of interest decreases frame rate, and the limited field of view is a disadvantage for complex CHD where the relationship of different structures to each other is crucial for decision-making. Some manufacturers have a further 3D mode which permits the operator to select an area of interest but with relatively low frame rates particularly if colour flow Doppler is added. This mode is mainly used during catheter intervention, particularly ASDs, VSDs, and the AV valves. Depending on the system, vendor settings may be adjusted to allow the operator to prioritize volume rate at the expense of line density, thus achieving a higher temporal but lower spatial resolution.
ECG-gated Multi-beat Acquisition
With current imaging technology, ECG-gated multi-beat image acquisition is frequently used for pediatric 3DE because it acquires a large field of view with sufficient temporal resolution. However, the electronic ‘stitching’ of narrow volumes of data over 2–6 heartbeats may produce artefacts related to patient breathing or movement, particularly in young children. This is not an issue in ventilated children under general anesthesia, because ventilation can be suspended briefly, and is less of a problem during sleep or with sedation. Although ‘single-beat’ volume acquisition has been introduced, the limited temporal resolution is insufficient for high heart rates of infants and children unless the region of interest is small thereby permitting narrowing of the imaging sector, or if the region of interest is relatively static.
3DE Color Flow Doppler
3DE color flow Doppler can be added to any of the above modalities. In common with 2DE, the addition of color flow Doppler reduces temporal resolution. Depending on the size of the region of interest, the achievable frame rate may be too low for fast moving structures such as AV valves. Some manufacturers may permit the user to prioritize temporal resolution over spatial resolution to maintain an acceptable frame rate. The alternative is to use an ECG-gated multi-beat acquisition to maintain an acceptable frame rate.
Principles of 3DE Acquisition
3DE for CHD utilizes the same transducers and ultrasound systems as adults with the addition of high-frequency probes suitable for imaging babies and children. General points are summarized below with emphasis on points relevant to the child or adult with CHD. In all patients, meticulous attention to 2D image quality is necessary to optimize the quality of the 3DE dataset. A high-frequency 3DE transducer should be used where possible, especially in small children where ultrasound penetration is not an issue, and the sector width narrowed to include only the regions of interest. Axial resolution is higher than either lateral or elevational planes which impacts on the optimal transducer position for the lesion being evaluated. For example, the mitral valve may be interrogated either from apical or parasternal view to delineate both leaflets and the subvalvar apparatus. Review of the multiplanar images is particularly important prior to display of rendered images to avoid diagnostic error. Comprehensive reviews of 3DE artefacts have been published for reference.
Imaging of relatively static cardiac structures, such as ASDs and VSDs, may be achieved using live 3DE or 3DE ‘zoom’ modes because temporal resolution is sufficient. Gain settings during acquisition and post-processing are particularly important in smaller patients with thin valves to reduce ‘noise’ that may impede visualization ( Figure 2 A and B) while avoiding ‘holes’ or other artefacts from inadequate gain. The normal gain setting for a 3DE acquisition is slightly higher than conventional 2DE as gain can be reduced during post-processing to optimize the image, whereas if too little gain is used during acquisition, increasing gain during post-processing does not restore parts of the image which have not been adequately visualized during the acquisition. This affects thin structures such as valve leaflets in particular.
Presentation of 3DE images of CHD merits particular consideration, especially for valves, and individualized tilt or rotation to display the region of interest can help ( Figure 3 A and B). The 3D display modes for CHD are analogous to those used for adults and include (i) volume rendering, (ii) surface rendering, and (iii) multiplanar reformatted (MPR) image display. Volume-rendered datasets can be electronically segmented, allowing the operator to ‘crop’ the heart in multiple sections to expose the cardiac structure of interest from any desired angle. This is especially useful for CHD prior to surgery or intervention. Surface rendering presents the surfaces of structures or organs with a solid appearance and is mainly used to visualize size, shape, and function of cardiac structures. Analysis software for this mode includes semi and fully automated endocardial border detection for quantification of left ventricular (LV) and RV function as well as semi-automated mitral leaflet motion detection for quantification of valve function, both of which may be limited by the abnormal ventricular shape or valve morphology found in CHD.
MPR allows the 3DE dataset to be viewed on a quad screen with the 3D dataset cut into three planes (sagittal, coronal, and transverse) which are configurable by the user. Adjustment of the MPR planes is illustrated in Supplementary data online, Powerpoint 1 . This display of planes not available by 2DE can aid with understanding complex anatomies and facilitate measurement of many CHDs such as ASD and VSD size. Valve areas, effective orifice areas, and vena contracta areas of regurgitant jets can all be measured by manipulating cutting planes to avoid foreshortening or oblique measurements.
Future Directions
Improved temporal resolution of single-beat acquisitions or post-processing software to deal with stitch artefacts would enhance 3DE in younger patients. Software packages that can accommodate analysis of valves and chambers of abnormal morphology would also benefit the patient with CHD.
Recommendations
The 3DE approach should be tailored according to the patient. Small footprint and high-frequency 3DE transducers should be used in infants and young children and for epicardial 3DE.
3D TEE should be considered when patient size permits if 3D TTE provides insufficient imaging to plan therapy.
Three-dimensional Echocardiographic Imaging Techniques
Transducers
The evolution of 3DE techniques and transducer technology has been well described. The development of the matrix array probe with parallel processing has made real-time 3DE possible since the 1990s. Later generations of transducers have become smaller with footprints similar to two-dimensional echocardiography (2DE) transducers. The development of a small high-frequency pediatric 3DE transducer (2–7 MHz) has enhanced spatial and temporal resolution, especially pertinent for small children with high heart rates. Similarly, miniaturization has enabled the development of adult-size 3D transesophageal echocardiography (TEE) probes.
Workflow
Ideally, 3DE transducers should be capable of producing 2D images which are at least equivalent to 2DE transducers. Some 3D transesophageal transducers achieve this, but transthoracic 3DE probes still do not generally match the image quality of a dedicated 2D transducer. The difference remains most marked for high-frequency pediatric 3DE probes compared with the 2DE equivalent transducer. Consequently, the use of the combined 2DE–3DE transducer is not routine in smaller patients. Manufacturer recommendations suggest that current 3D TEE probes are used for patients >30 kg. Some pediatric cardiologists will extend use of such probes to smaller patients. Those undertaking such procedures should be aware of the specific manufacturer recommendation for the transducer. In any patient, the risk of complications such as damage to the oropharynx and oesophagus caused by an oversized probe needs to be balanced against the additional value of 3DE. For patients who are currently too small to accommodate 3D TEE transducers, epicardial 3D imaging with a transthoracic 3DE transducer is a feasible alternative technique during surgery.
Data Acquisition Modes
Good spatial and temporal resolution in 3DE is a priority for imaging of CHD, particularly valve pathology and complex lesions. The matrix transducer has different modalities of data acquisition whose use is dictated by the clinical question. For example, in the assessment of double outlet RV, the incorporation of the AV valves, ventricular septum, and great arteries is necessary for decision-making, whereas measuring the size of an isolated VSD does not require such an extended field of view. The exact configuration and nomenclature of different modes is vendor specific but with features in common.
2D Simultaneous Multiplane Mode
Current matrix probes allow 360° electronic rotation of the imaging plane as well as simultaneous display of more than one 2D imaging plane that can be electronically steered in the elevation or lateral plane. The crop plane is marked on the projection but with the drawback that temporal resolution is reduced. Applications include assessment of atrial septal defect (ASD) size and rim length, size and shape of VSDs, AV valve morphology and regurgitation ( Figure 1 A and B), outflow tracts and arterial valves.
Real-Time 3DE Mode
Real-time 3DE permits a display of an adjustable pyramidal volume, minimizing the issue with poor co-operation in children because there is no potential for ‘stitch’ artefacts between adjacent subvolumes. Increasing the region of interest decreases frame rate, and the limited field of view is a disadvantage for complex CHD where the relationship of different structures to each other is crucial for decision-making. Some manufacturers have a further 3D mode which permits the operator to select an area of interest but with relatively low frame rates particularly if colour flow Doppler is added. This mode is mainly used during catheter intervention, particularly ASDs, VSDs, and the AV valves. Depending on the system, vendor settings may be adjusted to allow the operator to prioritize volume rate at the expense of line density, thus achieving a higher temporal but lower spatial resolution.
ECG-gated Multi-beat Acquisition
With current imaging technology, ECG-gated multi-beat image acquisition is frequently used for pediatric 3DE because it acquires a large field of view with sufficient temporal resolution. However, the electronic ‘stitching’ of narrow volumes of data over 2–6 heartbeats may produce artefacts related to patient breathing or movement, particularly in young children. This is not an issue in ventilated children under general anesthesia, because ventilation can be suspended briefly, and is less of a problem during sleep or with sedation. Although ‘single-beat’ volume acquisition has been introduced, the limited temporal resolution is insufficient for high heart rates of infants and children unless the region of interest is small thereby permitting narrowing of the imaging sector, or if the region of interest is relatively static.
3DE Color Flow Doppler
3DE color flow Doppler can be added to any of the above modalities. In common with 2DE, the addition of color flow Doppler reduces temporal resolution. Depending on the size of the region of interest, the achievable frame rate may be too low for fast moving structures such as AV valves. Some manufacturers may permit the user to prioritize temporal resolution over spatial resolution to maintain an acceptable frame rate. The alternative is to use an ECG-gated multi-beat acquisition to maintain an acceptable frame rate.
Principles of 3DE Acquisition
3DE for CHD utilizes the same transducers and ultrasound systems as adults with the addition of high-frequency probes suitable for imaging babies and children. General points are summarized below with emphasis on points relevant to the child or adult with CHD. In all patients, meticulous attention to 2D image quality is necessary to optimize the quality of the 3DE dataset. A high-frequency 3DE transducer should be used where possible, especially in small children where ultrasound penetration is not an issue, and the sector width narrowed to include only the regions of interest. Axial resolution is higher than either lateral or elevational planes which impacts on the optimal transducer position for the lesion being evaluated. For example, the mitral valve may be interrogated either from apical or parasternal view to delineate both leaflets and the subvalvar apparatus. Review of the multiplanar images is particularly important prior to display of rendered images to avoid diagnostic error. Comprehensive reviews of 3DE artefacts have been published for reference.
Imaging of relatively static cardiac structures, such as ASDs and VSDs, may be achieved using live 3DE or 3DE ‘zoom’ modes because temporal resolution is sufficient. Gain settings during acquisition and post-processing are particularly important in smaller patients with thin valves to reduce ‘noise’ that may impede visualization ( Figure 2 A and B) while avoiding ‘holes’ or other artefacts from inadequate gain. The normal gain setting for a 3DE acquisition is slightly higher than conventional 2DE as gain can be reduced during post-processing to optimize the image, whereas if too little gain is used during acquisition, increasing gain during post-processing does not restore parts of the image which have not been adequately visualized during the acquisition. This affects thin structures such as valve leaflets in particular.
Presentation of 3DE images of CHD merits particular consideration, especially for valves, and individualized tilt or rotation to display the region of interest can help ( Figure 3 A and B). The 3D display modes for CHD are analogous to those used for adults and include (i) volume rendering, (ii) surface rendering, and (iii) multiplanar reformatted (MPR) image display. Volume-rendered datasets can be electronically segmented, allowing the operator to ‘crop’ the heart in multiple sections to expose the cardiac structure of interest from any desired angle. This is especially useful for CHD prior to surgery or intervention. Surface rendering presents the surfaces of structures or organs with a solid appearance and is mainly used to visualize size, shape, and function of cardiac structures. Analysis software for this mode includes semi and fully automated endocardial border detection for quantification of left ventricular (LV) and RV function as well as semi-automated mitral leaflet motion detection for quantification of valve function, both of which may be limited by the abnormal ventricular shape or valve morphology found in CHD.
MPR allows the 3DE dataset to be viewed on a quad screen with the 3D dataset cut into three planes (sagittal, coronal, and transverse) which are configurable by the user. Adjustment of the MPR planes is illustrated in Supplementary data online, Powerpoint 1 . This display of planes not available by 2DE can aid with understanding complex anatomies and facilitate measurement of many CHDs such as ASD and VSD size. Valve areas, effective orifice areas, and vena contracta areas of regurgitant jets can all be measured by manipulating cutting planes to avoid foreshortening or oblique measurements.
Future Directions
Improved temporal resolution of single-beat acquisitions or post-processing software to deal with stitch artefacts would enhance 3DE in younger patients. Software packages that can accommodate analysis of valves and chambers of abnormal morphology would also benefit the patient with CHD.
Recommendations
The 3DE approach should be tailored according to the patient. Small footprint and high-frequency 3DE transducers should be used in infants and young children and for epicardial 3DE.
3D TEE should be considered when patient size permits if 3D TTE provides insufficient imaging to plan therapy.
Image Display and Orientation
Published standards have been produced for the echocardiographic assessment of patients with pediatric and CHD, including TTE, TEE, and quantification. Recent published work has defined standards for adult practice using 3DE, but the latter specifically excluded CHD. In the patient with CHD, cardiac position, situs, connections, and alignments may be abnormal which presents a major challenge compared with acquired heart disease. 3DE facilitates en face projections of cardiac septums and AV valves, which can be rotated in the z -plane to any desired orientation. If the analogy of a clock face is used, the use of z -plane rotation turns the image in a clockwise or counter clockwise direction to achieve an anatomically correct orientation (see Supplementary data online, Presentation 1 ). The retention of adjacent anatomic landmarks is desirable, where possible, to assist orientation. Echocardiographic evaluation of the patient with CHD is often complemented by other imaging modalities including magnetic resonance imaging (MRI), computed tomography (CT), and angiography. To gain maximum value, the orientation of 3DE images should be both consistent and intuitive, as exemplified by the ‘anatomic’ approach to image display, projecting the heart in the same orientation as a person standing in an upright position. With this approach, superiorly positioned structures will be displayed uppermost on the image. This anatomically correct approach is consistent with the projection of MRI and CT images. The application of an anatomic orientation can be illustrated with specific examples.
The Atrial Septum
The atrial septum can be visualized from the right or left atrial aspect. A projection from the right atrium permits visualization of important landmarks such as the superior vena cava, inferior vena cava, ascending aorta, tricuspid valve, oval fossa, and os of the coronary sinus. The preferred anatomic image orientation has the superior vena cava uppermost and tricuspid valve seen to the right of the atrial septum ( Figure 4 ).
The Ventricular Septum
The ventricular septum can be visualized from either the RV or the LV aspect. By convention, the components of the ventricular septum are named as if the septum is viewed from the RV side with the free wall of the RV removed. With the anatomic approach, the diaphragmatic border of the heart is lowermost, the RV apex is seen to the right and the RV outflow tract viewed uppermost on the projected image so that landmarks such as the tricuspid valve, moderator band, and septomarginal trabeculation are seen in anatomically appropriate position ( Figure 5 A). Similarly, the LV aspect of the ventricular septum can be viewed in an anatomic projection ( Figure 5 B), to include both the septum and LV outflow tract.
AV Valves
In CHD, the left-sided AV valve may not be a bileaflet valve of ‘mitral’ type and the right-sided AV valve may not be the tricuspid valve. Regardless of the morphology of the valve, or whether an en face view is projected from the ventricular or atrial aspect, the 3D rendered image is rotated so that the diaphragmatic surface of the heart is shown lowermost ( Figure 6 A and B). This means, for example, that the superior bridging leaflet in an AV septal defect will be shown uppermost on the image and the inferior bridging leaflet lowermost ( Figure 7 ).
Aortic and Pulmonary Valves
The morphology, position and patency of the aortic, and pulmonary valves cannot be assumed in CHD. These valves are therefore projected in an anatomic format using the standard conventions for nomenclature of the valve leaflets. For example, the aortic valve may be projected as if seen from the ascending aorta or from the LV outflow tract. The conventional nomenclature of left, right, and noncoronary leaflets and sinuses is used in exactly the same fashion as in 2DE. An example of the preferred orientation of the aortic valve is shown ( Figure 8 ) and a similar approach is used for the pulmonary valve.
Complex Abnormalities of Cardiac Connections
When the main cardiac connections are abnormal, an anatomic presentation of images is particularly important so that the abnormal anatomy is displayed in a manner as close as possible to the actual spatial locations. An accurate understanding of the relationship of intracardiac structures has a direct impact on the surgical approach.
‘Surgical’ Views of the Heart
The term ‘surgical’ view has been used to describe 3D projections that are most akin to the surgeon’s view during an operation. There are specific considerations for this term, particularly in contrast to the ‘anatomic’ view. The anatomic view is projected as if the person is standing upright, whereas a surgical view is projected as if the patient is lying supine with the lead surgeon operating from the right side of the patient. The effect of this is that an anatomic en face view of the right side of the atrial or ventricular septum would be rotated counter clockwise 90° when projecting a ‘surgical’ view ( Figure 9 ). Views of the atrial aspect of the AV valves are often referred to as ‘surgical’ even though the surgeon may take a different access route to repair the valve in question. For example, the truly surgical view of the mitral valve would be presented with the patient supine with the left atrium accessed through the atrial septum. This contrasts with the usual projected 3DE view obtained by cropping away the posterior aspect of the atriums and rotating the AV valves en face with rotation of the whole dataset into an anatomic position. In practice, our preference is an anatomic orientation, which maintains consistency with projections of MRI and CT scans, knowing that ‘surgical’ visualization of the structures may be different. A visual demonstration of the common manipulations of 3D datasets accompanies this document (see Supplementary data online, Presentation 1 ).
Future Directions
The availability of orientation markers, already available for CT angiography and MRI, is needed for 3DE to mark, for example, the true left/right or superior/inferior orientation of an image. This should be coupled with the ability to ‘landmark’ important anatomical structures to enhance display of complex CHD as the data is manipulated. Fusion imaging, where 3DE datasets can be co-registered with datasets from other modalities (fluoroscopy, CT angiography, and MRI), will allow for both automated anatomic orientation of 3DE images and visualization of regions which may be sonographically inaccessible. Widespread implementation would require co-registration across vendors, modalities, and platforms.
Recommendations
An ‘anatomic’ approach to image display is recommended as it reflects the real position of structures in space and is consistent with other modalities such as MRI and CT.
En face views of septums and AV valves should retain important landmarks and be rotated into a correct anatomic orientation.
The term ‘surgical’ view should be used only for projections that show anatomy as the surgeon would visualize the region of interest.
Optimal Sonographic Projections for Different Congenital Heart Lesions
Standard imaging planes in 2DE have been developed from a combination of anatomical constraints and accessible sonographic windows, forming the basis for published standards. 3DE is less constrained since post-processing will allow interrogation of structures contained within the acquired volume. A corollary is that a structure of interest can be displayed similarly after post-processing despite being acquired from a range of different echocardiographic windows. However, the principles of imaging physics apply as much to 3DE as they do to 2DE. For this reason, there are optimal approaches for data acquisition that should allow for optimal demonstration of the structure of interest. General recommendations can be made about the optimal acoustic windows to show different regions of interest. These include the following:
- (i)
clear visualization of the region of interest on 2DE
- (ii)
insonation orthogonal to the plane of the structure of interest where possible
- (iii)
inclusion of clinically relevant adjacent structures
- (iv)
optimization of volume width and depth
For example, acquiring a 3D dataset to display an ASD is best achieved in a subcostal window because insonation from this view is orthogonal to the plane of the atrial septum. With TEE there is less flexibility to adjust the sonographic window; however, this is offset by higher image quality than TTE.
Although image quality is central to interrogation of regions of interest and good 3D reconstruction, there are important differences from 2DE. For example, parasternal long-axis (PLAX) and parasternal short-axis (PSAX) views are used in 2DE to evaluate a perimembranous VSD (pmVSD) because the defect is in the near field, and good alignment to Doppler jets can be achieved. However, 3DE is especially useful for its ability to display VSDs en face and to delineate adjacent structures. PLAX and PSAX views are limited because of the small size of the ultrasound sector in the near field. Thus, subcostal and modified apical views may better define adjacent structures because the VSD is in the centre of the imaging field with a wider sector. This tailored approach is also employed for more complex lesions such as double outlet RV where AV valves, ventricular septum, and outlets all have to be incorporated into the 3DE volume. Table 1 summarizes optimal TTE sonographic views and the usefulness of 3D TEE for common forms of CHD.
| Subcostal | Apical | PLAX | PSAX | 3D-TEE | |
|---|---|---|---|---|---|
| Atrial septum | |||||
| ASD | +++ | + (modified) | + (modified) | + (modified) | +++ |
| SV ASD | +++ | − | +++ | ||
| AV junction | |||||
| AVSD | +++ | +++ | ++ (LAVV) | + (LAVV) | +++ |
| Ebstein’s/TV dysplasia | +++ | ++ (Anterior angulation) | + | ++ | + |
| MV chordal structure | − | + (smaller patients) | +++ | ++ | +++ |
| Double orifice MV | ++ | ++ | + | ++ | ++ |
| MVP | − | ++ | +++ | ++ | +++ |
| Parachute MV | ++ | ++ | ++ | ++ | ++ |
| Supra mitral membrane | − | ++ | +++ | + | +++ |
| Ventricular septum | |||||
| mVSD (except anterior defects) | +++ | ++ | + | + | ++ |
| Membranous VSD | +++ | + | + | + | ++ |
| Doubly committed subarterial VSD | ++ | − | ++ (Angled to PA) | + | ++ |
| Outlets | |||||
| Aortic valve | − | + | ++ | ++ | +++ |
| Pulmonary valve | − | + | − | + | ++ |
| Double outlet right ventricle | +++ | + | − | + | + |
Technical limitations may, however, persist irrespective of the imaging plane. Both the aortic and pulmonary valves are thin, rapidly moving structures. These are often imaged by 3D TTE using a PLAX or PSAX view where the plane of insonation does not lend itself to good quality rendering of the entirety of individual valve leaflets, particularly the body of the leaflet. This issue can be overcome by TEE in patients large enough to accommodate the 3D TEE probe.
Recommendations
Optimal Sonographic Projections for Different Congenital Heart Lesions
The angle of insonation should be tailored to the region of interest and ideally should be orthogonal to the relevant structure.
The size of 3DE region of interest should be adjusted to optimize temporal and spatial resolution.
Added Value of 3DE for Different Congenital Heart Lesions
The literature on application of 3DE to CHD covers a wide variety of lesions including the AV valves, atrial septum, ventricular septum, and the outflow tracts. The use of 3DE techniques has increased as technology has improved, but there is wide institutional variability in the adoption of the technique. A central point in this regard is the evidence of additional diagnostic information compared with either 2DE or other imaging modalities. There have been no randomized trials relating to procedural success, morbidity or mortality related to the application of 3DE. Rather, 3DE has been adopted into practice on the basis of a clinical need to provide additional diagnostic information. Tables 2 and 3 present our consensus view of the added value of 3DE to assess some major groups of lesions. A selection of the key references relating to each of the different lesions is also included within the tables as well as a summary of the additional information provided. The type of lesions for which 3DE has a major role is heavily weighted towards valvar lesions and defects in both the atrial and ventricular septum (see Supplementary data online, Appendix 1, Presentation 1 ). A good example of the application of 3DE to more complex CHD is decision-making in patients with double outlet RV where particular considerations include the size and location of the VSD, and the relative position of the great arteries ( Figure 10 A–D , Supplementary data online, Video 1A–D ). The depth of field enhances visualization of the position and size of the VSD relative to the great arteries, and projections are achieved from the RV aspect and apex which cannot be achieved by 2DE.
| Region of interest | 3D modalities | Information acquired (I) Comment (C) | Strength of recommendation |
|---|---|---|---|
| Atrial septum | GS/CFM TTE/TEE | I: Size/number/shape/location of defects C: High value for multiple defects, multiple device deployment, residual leaks, spiral defects | HIGH for complex or residual defects MODERATE for single central defects LOW for PFO |
| Tricuspid valve abnormality | GS/CFM TTE/TEE | I: Leaflet morphology Chordal support Delineation of regurgitant jets C: Mechanism/severity of regurgitation refined | HIGH |
| Mitral valve | GS/CFM TTE/TEE | I: Leaflet morphology Chordal support Delineation of regurgitant jets C: Mechanism/severity of regurgitation refined | HIGH |
| Ventricular septum | GS/CFM TTE/TEE | I: Size/number/shape/location of defects C: High value for multiple defects, unusually located defects or consideration of interventional closure | HIGH for more complex defects LOW for other defects |
| Left ventricular outflow tract | GS/CFM TTE/TEE | I: Morphology of subaortic obstruction and aortic valve C: Clarify mechanism of obstruction and/or regurgitation | HIGH |
| Aortic valve | GS/CFM TTE/TEE | I: Measurement of aortic valve Morphology of aortic valve leaflets Mechanism of aortic regurgitation C: Imaging of aortic valve leaflets more difficult by 3D TTE, 3D TEE preferred | HIGH Especially by TOE |
| Aortic arch | GS/CFM TTE | I: Morphology and sizing of aortic arch C: Imaging may be difficult due to probe size, acoustic access | LOW/MOD |
| Right Ventricular Outflow tract | GS/CFM TTE/TEE | I: RVOT morphology Visualization of site of RVOT obstruction C: Questionable benefit over 2DE | LOW/MODERATE |
| Pulmonary valve | – | I: PV morphology and function C: May be able to visualize PV morphology better than 2DE | Low |
| Branch pulmonary arteries | – | Not routinely used | None |
| Abnormal cardiac connection | 3D modalities | Information acquired (I) Comment (C) | Strength of recommendation |
|---|---|---|---|
| Systemic venous abnormalities | – | Not routinely used | No recommendation |
| Abnormal pulmonary venous drainage | – | Not routinely used | No recommendation |
| Atrioventricular septal defect | GS/CFM TTE/TEE | I: Size of atrial and ventricular components of the defect Leaflet morphology and chordal support Delineation of regurgitant jets Valvar and ventricular size in unbalanced defects C: Enhances measurement of valve size, chordal support and relative size of AV valves and ventricles | HIGH |
| Discordant atrioventricular connections | GS/CFM TTE/TEE | I: TV and MV morphology and function Location and size of associated VSDs Right and LV outflow tract C: Improves assessment of feasibility of Senning/Rastelli approach. Improves localization of VSDs | HIGH |
| Simple transposition of the great arteries | – | Not routinely used | No recommendation |
| Complex transposition of the great arteries | GS/CFM TTE/TEE | I: MV and TV morphology and size. Size, location of associated VSDs Anatomy of left or RV outflow tract obstruction C: Suitability for procedures such as Rastelli, Nikaidoh and arterial switch operations | HIGH |
| TOF | GS/CFM TTE | I: VSD size/location and RVOT anatomy C: Indicated where specific concerns, e.g. VSD position or RVOT anatomy More extensive use for RV volume estimation postoperatively | LOW |
| Common arterial trunk | GS/CFM TTE/TEE | I: Truncal valve morphology/regurgitation C: Not routinely indicated in infancy May assist delineation of truncal valve morphology/regurgitation in older patients by TEE | HIGH for truncal valve in older patients LOW in infancy |
| Double outlet RV | GS/CFM TTE | I: Relationship of AV valves VSD size and location Relative position of great arteries C: High value for guiding appropriate type of repair | HIGH |
Recommendations
Added Value of 3DE for Different Congenital Heart Lesions
3DE is recommended for the assessment of valvar lesions, septal defects, and complex abnormalities of the cardiac connections.
3DE should be regarded as a technique that complements rather than replaces 2DE for assessment of CHD.
Use of 3DE to Guide Catheter Intervention
3D TEE is a rapid and useful imaging technique for the assessment of CHD during catheter-based interventions, including device closure of ASDs and VSDs. 3D TEE complements rather than replaces 2D TEE, and both modalities are used to assess defects and adjacent margins, rims, and structures. 3DE is particularly helpful for irregularly or asymmetrically shaped defects where 2D assessment of size by rotation of the TEE probe is insufficient. En face views of defects permit more precise appreciation of adjacent structures than 2D TEE alone, particularly for more complex lesions. 3D TEE of younger patients is typically done under general anesthesia and is only feasible in patients large enough to accommodate the 3D TEE probe. Current manufacturers’ recommendations propose a minimum patient weight of 30 kg. Time is limited during the procedure; therefore, rapid, simple, and minimal post-processing real-time 3D acquisition modes are often most effective. A 3D full-volume acquisition is favoured at some centers to produce a high-resolution view of the entire region of interest at the start of the procedure, followed by more focused imaging using live techniques. Lesion-specific targeted views have to be obtained, as discussed in subsequent sections. En face views are consistently used to demonstrate the relevant anatomy and interventional hardware. In addition to rendered 3D views, MPR imaging is useful for quantitation and image display during interventions ( Figure 10 ).
ASD Device Closure
Transcatheter device closure of a secundum ASD has become the preferred method of treatment when the anatomy is favorable. Accurate assessment of ASD type, size, position, number of orifices, shape, and rim sizes ( Figure 11 ) is essential for correct patient selection, device selection, and deployment. Detailed analysis of device position, configuration, anchorage, residual shunt as well as the relationship of the device to the aorta, mitral valve, tricuspid valve, superior and inferior vena cava, and the pulmonary veins is necessary ( Figure 11 ). Demonstration of these features is usually enhanced and at times only possible with 3DE.
The 3D TEE right atrial en face views from the mid-oesophagus selecting the region of interest to produce real-time 3D images can often demonstrate the key features during secundum ASD intervention. 3D full-volume acquisition may be needed if the volume rate using focused live 3D acquisition is too low. The deep trans-gastric sagittal bicaval view best demonstrates the inferior rim and septal length and provides a good view from which to monitor device deployment. Precise measurement of the ASD is best performed using the MPR four panel format, but measurement of the rendered image is an alternative ( Figure 10 ). Color Doppler flow analysis of the size, position, and mechanism of residual shunts is best performed with live 3D color or biplane imaging. There are reports of using transthoracic 3DE to guide ASD closure from a subcostal view.
VSD Device Closure
Transcatheter closure of VSDs has developed as an alternative treatment to surgical closure of muscular VSDs (mVSDs) and pmVSDs. Specific advantages of 3DE over 2DE are improved visualization of the VSD shape, size, and location as well as characterization of the tricuspid pouch and surrounding structures. En face presentation of the ventricular septum from both RV and LV aspects can be accomplished most expeditiously from a four-chamber view using live 3D ( Figure 12 ) or ECG-gated full-volume acquisition. Monitoring of interventional device hardware and device deployment is seen in a frontal four-chamber view ( Figure 12 ). Following device deployment, live 3DE, cross plane, or MPR imaging with color flow Doppler is optimal for assessing the interventional result.
