With the exception of MV prolapse, congenital diseases of the MV are rare [14]. They include abnormalities predominantly of the valve tissue (isolated MV clefts and MV dysplasia) and abnormalities of the valve and support apparatus (double orifice MV, parachute MV and arcade MV). These abnormalities can lead to stenosis, regurgitation or both, and can be challenging to surgically repair.

RT3DE allows visualization of the entire valve and support apparatus in one image. Early 3DE improved our understanding of the normal MV structure and function, including its saddle shape, influences on leaflet stress and dynamic changes throughout systole and diastole [15]. Early studies on the normal MV paved the way for its assessment in CHD. There have been many reports of RT3DE aiding in the diagnosis of congenital MV disease including MV prolapse, double orifice MV [16, 17] (Fig. 9.3), arcade MV [18], isolated MV dysplasia, cleft MV (Fig. 9.4) and parachute MV [19]. In addition RT3DE has contributed to the diagnosis of abnormalities of the supravalvar area including cor triatriatum [20] and supramitral ring [21]. In a larger cohort, Takahashi et al. [22] showed that RT3DE had improved accuracy compared to 2D echocardiography in detecting leaflet and commissural abnormalities and correlated well with surgical findings.

RT3DE can improve the assessment and quantification of mitral regurgitation. 2D echocardiography provides adequate assessment of central, symmetric jets of mitral regurgitation. However, mitral regurgitation jets in congenital MV disease are often eccentric, irregularly shaped and displaced towards a specific anatomic abnormality (i.e. cleft). The assessment of mitral regurgitation with RT3DE does not require assumptions about the jet shape, and has been shown to be superior to 2D echocardiography in the detection and assessment of commissural regurgitation [22]. Importantly, the assessment of regurgitation using RT3DE occurs in a physiologic state, which makes it superior to surgical saline testing, especially for commissural regurgitation and clefts [22]. Many studies have been performed in adults with structurally normal MV comparing 3D derived vena contracta area (Fig. 9.5) to traditional measures of mitral regurgitation [23–25], with excellent correlation between RT3DE and MRI. In patients with atrioventricular septal defects (AVSD), vena contracta area correlates well with 2D-derived measures of regurgitation [26]. However, no studies have compared RT3DE-derived vena contracta area with MRI-derived regurgitant fraction in patients with CHD, and no normal values have been established in the pediatric population.

The defining feature of an atrioventricular septal defect is a common atrioventricular junction with a trileaflet left atrioventricular valve and an unwedged aortic valve (Fig. 9.6). The presence and severity of inter-atrial and inter-ventricular shunting is variable. Although sometimes called a MV, the left atrioventricular valve is unique, as it is composed of three leaflets. The so-called cleft is actually the zone of apposition between the superior and inferior bridging leaflets and is often a source of significant regurgitation (Figs. 9.6 and 9.7). Even in the current surgical era, regurgitation and stenosis of the left atrioventricular valve cause significant long-term morbidity.

RT3DE has been shown to provide additional anatomic and functional information both prior to AVSD repair [27] and afterwards [28, 29]. RT3DE correlates better with surgical findings compared to 2D echocardiography [30], specifically in the detection of commissural abnormalities and related regurgitation and in assessing for a residual cleft post repair [27].

It is still poorly understood why some AV valves are at increased risk of dysfunction after AVSD repair compared to others. RT3DE has provided important information regarding valve function and physiology in patients with AVSD and aided in the determination of risk factors for regurgitation and optimal surgical strategies. Unlike 2D echocardiography RT3DE is able to quantify valve prolapse area, and it is now clear that increased prolapse is associated with increased AV valve regurgitation pre- and post-operatively [26]. RT3DE also allows the quantification of valve tethering, through the measurement of valve and support apparatus angles. Increased tethering, often associated with asymmetric commissures, is associated with increased valve regurgitation post-operatively, even in patients with minimal pre-operative valve dysfunction [28, 31]. This has led some institutions to perform routine RT3DE assessments of the left atrioventricular valve in patients with AVSD and alter their surgical approach in high-risk patients [31].

Congenital tricuspid valve (TV) disease usually includes TV dysplasia and Ebstein’s anomaly of the TV. The TV is more difficult to visualize compared to the mitral valve and there is no standard ‘en face’ view available using 2D echocardiography. It is often even more difficult to visualize the TV in patients with Ebstein’s anomaly due to the displacement and rotation of the functional valve orifice. The regurgitant jet is often very eccentric and difficult to evaluate.

RT3DE allows the TV to be visualized ‘en face’ and has been shown to be more accurate for detecting abnormalities in the TV anatomy and sources of regurgitation compared to 2D echocardiography alone [22] (Fig. 9.8). In Ebstein’s anomaly RT3DE has been helpful in visualizing the TV anatomy and assessing tricuspid regurgitation using the vena contracta area [32, 33]. It has proven valuable in evaluating the RV size and function in this lesion [32, 33]. More recently, the MPR mode has allowed a more accurate determination of dysplastic versus Ebsteinoid TV, and has correlated well with surgical findings [34].

Despite advances in pre-operative, surgical and post-operative care, the morbidity and mortality in patients with single ventricle physiology remains high. These patients are at risk of significant AV valve regurgitation, which puts them at even higher risk. These valves can be challenging to image as they are often structurally different from mitral or tricuspid valves and commonly additional abnormalities including clefts, prolapse and tethering (Fig. 9.9).

RT3DE has significantly improved our ability to visualize the atrioventricular valve anatomy in single ventricles, as well as our understanding of the mechanisms of regurgitation. In patients with normal cardiac anatomy, it is well known that there are ventricular-ventricular interactions that can affect atrioventricular valve function. These interactions are altered in patients with single ventricle physiology and may lead to ventricular dysfunction and valvar regurgitation. In patients with hypoplastic left heart syndrome, RT3DE has shown that the tricuspid valve annulus shape is flatter, more circular, more dilated and less dynamic throughout the cardiac cycle [34, 35]. These changes and chordal abnormalities may lead to tethering and prolapse and are associated with increased regurgitation [34, 35]. Not only does this information improve our understanding of valve function in these lesions. It may help predict high-risk patients. Kutty et al. has shown that patients with increased tethering and a flatter annulus prior to stage 1 palliation are at increased risk of tricuspid regurgitation post operatively [35]. Interestingly, they did not find significant prolapse at this stage, and propose that prolapse may develop over a longer time period in these patients.

Quantification of valve regurgitation in these patients is often difficult and qualitative. RT3DE has been used to quantify tricuspid regurgitation (vena contracta area) in structurally normal hearts, with excellent correlation with 2D echocardiography [36]. This method has a superior correlation with MRI quantification in the evaluation of other cardiac valves compared to 2D echocardiography, and is often used as the gold standard for assessment of regurgitation. Although definitive studies have not been performed to evaluate quantification of AV valve regurgitation in the single ventricle population using RT3DE, this method is promising in improving the ability to quantify regurgitation in this population.

Atrial septal defects (ASDs) are one of the most common CHD, occurring in 19% of CHD [14]. Traditionally ASDs were closed surgically; however more defects are now amenable to interventional device closure in the cardiac catheterization laboratory. The appropriate selection of patients for device ASD closure is critical and requires specific information on the number, size and shape of defects, as well as their relation to other cardiac structures. In some patients, these factors can be difficult to determine using 2D echocardiography alone.

In children, the atrial septum is a thin structure that is prone to dropout artifact, and maximizing the spatial resolution during image acquisition is important. Subcostal and right parasternal transthoracic views, and mid-esophageal TEE (0 and 90 degrees) views maximize spatial resolution by imaging in the axial plane. In older children and adults with limited subcostal views, apical 4 chamber views can be cropped to visualize the atrial septum ‘en face’. Although the spatial resolution is decreased, it is often sufficient in older patients with a thicker atrial septum [37]. The addition of colour Doppler to 3D images can help to distinguish defect from dropout. Anatomic and surgical views from the right and left atria [38], as well as standard 2D views with added depth can be used to display the anatomy (Fig. 9.10).

RT3DE has aided in the diagnosis of all types of inter-atrial communications [39], but its true value has been aiding the characterization and management of secundum ASDs. Early on, RT3DE was shown to provide additive information on the size and shape of ASDs as well as the size of their rims that correlated well with catheter and surgical findings [40–42]. In larger studies, RT3DE has been shown to be similar to 2D echocardiography in determining rim size, but superior in evaluating the number and shape of defects [43, 44]. RT3DE is especially advantageous for characterizing patients with multiple defects, as determining the relative size and shape of multiple defects is difficult using 2D echocardiography [45].