Double outlet right ventricle (DORV) is not a specific congenital malformation, but rather, an abnormal ventriculo-arterial alignment whereby both great arteries arise from the morphologic RV (Figs. 12.16 and 12.17, Video 12.13). By most criteria, both great vessels must sit more than 50 % over the RV [27]. Typically, there is bilateral conus, with myocardium separating both great vessels from the AV valves. However, other conal anatomy can occur in DORV [28]. A VSD is present in almost all cases and usually acts as the “outlet” from the left ventricle (LV). There are rare reports of DORV with an intact ventricular septum [29, 30]. In DORV, the ventricular loop may be “D” (normal) or “L” (inverted) and this will affect the relationship of the great arteries to the ventricle and to each other.

The anatomic and physiologic spectrum of DORV is wide. Associated anomalies are common and include ventricular hypoplasia, superior/inferior ventricles, mitral valve anomalies (including mitral atresia, straddling or parachute mitral valve), common AV canal (in heterotaxy syndrome) and outflow obstruction [28, 31, 32].

The pathophysiology can be similar to TOF, transposition of the great arteries, or a large VSD. This physiology is determined by the location of the great vessels in relationship to the VSD and the degree of outflow obstruction. Of critical importance is the type and location of the VSD: it often determines the type of surgical repair as well as, in some instances, the viability for two-ventricle versus a single ventricle surgical strategy. By far, the most common type of VSD in DORV is the malalignment type, however any type of VSD (such as AV canal, mid muscular, or apical muscular) can occur [33]. The VSD is also classified as one of four types, based upon its relationship to the great vessels: subaortic, subpulmonary, noncommitted, and doubly committed. In those patients with DORV with malalignment type VSD, the most common location of the VSD is subaortic. This is seen on echocardiography as muscle between the mitral and aortic valves. If there is no pulmonary stenosis, the physiology is similar to a large unrestrictive VSD because the blood flow streams from the LV into the aorta. If there is pulmonary stenosis, the physiology is similar to TOF. However, the distinction between DORV and TOF is of utmost importance because those patients with TOF-like DORV have complete subaortic conus that can result in subaortic obstruction after surgery [34]. Subaortic stenosis is extremely rare in TOF.

DORV with subpulmonary VSD is classically termed a “Taussig-Bing” anomaly. In this defect, the great vessels are spatially oriented side-by-side, bilateral conus is present, and the aorta is to the right of the pulmonary artery. The blood from the LV streams into the pulmonary artery so that the physiology is similar to transposition of the great arteries (see below). The subaortic conus is usually small, thus arch obstruction is a frequent association. Some cases of DORV with subpulmonary VSD are not classic Taussig-Bing anomalies but rather fall within the spectrum of that anatomic description. The distinction is critically important when determining surgical strategy.

More uncommon locations of the VSD in DORV include non-committed or doubly-committed subtypes. In DORV with non-committed VSD, the VSD is usually a muscular or a canal (inlet) type VSD. Since it is far from both outflow tracts, baffling procedures may pose a significant challenge. Often, AV valve tissue is obstructing the potential pathway from the LV to the aorta. Moreover, straddling tricuspid valve can occur in association with a canal type VSD. When a muscular VSD is present, there is a tendency for the defect to get smaller over time because it is surrounded by muscle; therefore in general, muscular VSDs are not considered reliable pathways to a great artery. In the rare doubly-committed type, both great vessels sit directly over the VSD.

Other variations of DORV exist, most commonly including those with mitral atresia or hypoplasia associated with left ventricular hypoplasia. When there is significant ventricular hypoplasia, the single ventricle surgical strategy is usually indicated. DORV is often seen in patients with superior/inferior ventricles with criss-cross AV valves. In this rare anomaly, the RV is situated superior to the LV and it is typically hypoplastic. The VSD is usually a canal (inlet) type.

Genetic syndromes can be seen with DORV but there is not one particular association. Transforming growth factor (TGF)-beta 2 knockout mice have been observed to develop DORV in the majority of cases [35]. Heterotaxy syndrome often has DORV as one of its cardiac components.

There are pertinent findings seen with DORV to keep in mind when performing a TEE:

One of the most important aspects of the pre-operative evaluation of the patient with DORV is assessment of location and size of the VSD and its relationship to the great vessels (Fig. 12.18, Video 12.14). This, along with the other echocardiographic goals mentioned above, can often help in the determination of the optimal surgical strategy. TEE is an excellent tool to assess for AV valve abnormalities that might preclude a biventricular repair. For example, a straddling AV valve over a VSD usually obstructs the pathway from the LV to a great artery. TEE can also assess whether a VSD is restrictive and the mechanism of the restriction (i.e. AV valve tissue, conal muscle) [36]. Moreover, important anatomic features to help determine a surgical strategy include prominence of the conal septum, presence of tricuspid valve attachments to conal septum, and the distance between the pulmonary and tricuspid valves [37].

The standard ME 4 Ch view may not show evidence of pathology other than RV hypertrophy. However, probe withdrawal and anteflexion will demonstrate that both great vessels arise mostly or completely from the anatomic RV (Fig. 12.16 and 12.17). The anatomy of the AV valves can be seen in this view, as well as in a sweep of the multiplane angle from 0 to 90° that incorporates both the ME RV In-Out and ME 2 Ch views. Alignment of the great vessels is dependent on their position; therefore no single TEE view will be adequate for all patients with DORV. The advantage of the multiplane probe is that the best view of the outflow tracts can be determined as the study is performed. The DTG LAX and DTG Sagittal views are also useful to visualize the great arteries and their relationship to the VSD (Fig. 12.19, Video 12.15). Additional VSDs can be viewed in the ME 4 Ch and ME RV In-Out views, with variation of multiplane angle between 0 and 90° and axial probe rotation to perform a complete sweep of the ventricular septum. The transgastric short axis views (TG Basal SAX, TG Mid SAX) are also useful to evaluate for additional VSDs. Other associated anomalies can be demonstrated using TEE, including AV canal defect (as is common in heterotaxy syndrome), as well as juxtaposition of the atrial appendages, which can be seen from a modified ME 4 Ch view as well as ME AV SAX view (Fig. 12.20, Video 12.16). Systemic venous connections can be evaluated with the LE Situs SAX and lower esophageal IVC long axis (LE IVC LAX) views, as well as the ME Bicaval view (Chap.​ 4). Pulmonary venous connections can be evaluated using the modified ME 4 Ch and ME Bicaval/ME 2Ch views, as described in Chaps.​ 4 and 6.

Color Doppler can be used to assess for preoperative AV and semilunar valve regurgitation as well as restriction of flow across the VSD. Color interrogation can also be useful to assess inflow into each ventricle, particularly when straddling or overriding AV valves are suspected. Pulsed and continuous wave Doppler assessment of outflow tract obstruction is dependent on the angle of interrogation. The DTG LAX and DTG Sagittal views can be very helpful for this purpose. LV systolic pressure estimate (as measured by mitral regurgitation jet) is important if a restrictive VSD is suspected. The LV may be at suprasystemic pressure in these instances. This method of assessment, performed in the ME 4 Ch and ME 2 Ch views, is particularly important when the VSD jet is not at an appropriate angle for interrogation.

When both ventricles and both AV valves are well developed, the goal of surgical repair is to utilize the VSD to baffle the LV to one of the great arteries. If baffled to the aorta, a “physiologic repair” is achieved. If baffled to the pulmonary artery, an arterial switch operation is required. In cases where the VSD is remote from the great arteries, septation might not be possible. In addition, presence of a straddling tricuspid valve over a canal type VSD or straddling mitral valve over a malalignment VSD may also preclude septation into two ventricles. In these cases, staged surgical palliation culminating in the Fontan operation is usually performed [38].

For those undergoing a biventricular repair, selection of the appropriate operation depends upon an assessment of great artery relationship in relation to the ventricles and VSD, whether outflow tract obstruction is present and if so, which outflow tract is obstructed and to what degree. Based upon these assessments, a determination can be made as to the most suitable operation to effect a complete biventricular repair. The most common operations include:

Postoperative assessment is dependent upon the surgical intervention. In those patients with a subaortic VSD, the two most important issues for intraoperative TEE are assessment for a residual VSD and determination of possible LV outflow tract obstruction from the baffle to the aorta. Subaortic conus as well as VSD patch position may result in significant subaortic obstruction. The best view to assess the LV outflow tract is variable, depending on the relationship of the aorta to the LV. Though the ME AV LAX view with a multiplane angle of 120° is best for a normal LV outflow tract, this may not be the case in DORV, thus trying different TEE views, probe rotations, and multiplane angles, will often be required to obtain the best image. Doppler interrogation of the outflow tracts can also be challenging. A variety of different TEE views will often be necessary to obtain the optimal Doppler angle of interrogation; these usually include a combination of mid esophageal, transgastric, and (when available) deep transgastric views. Severity of obstruction may also have to be determined by other methods such as smallest diameter. In some cases, direct pressure measurements in the LV and the aorta might be required.

Assessment for residual ventricular communications is very important in patients undergoing repair of DORV. Intramural type defects can occur in this lesion as well (See section “Tetralogy of Fallot”). In patients with Taussig-Bing anatomy that undergo the arterial switch operation, intraoperative TEE assesses adequacy of the neo-aortic and neo-pulmonic anastomoses (see section “Transposition of the Great Arteries”) as well as the adequacy of the repair of associated defects.

Truncus arteriosus communis, also known more simply as truncus arteriosus (TA) or common arterial trunk, is characterized by the following anatomic features: a solitary great vessel arises from the heart, giving rise to the aorta, at least one pulmonary artery, and at least one coronary artery. Almost always, there is a large VSD in which the septal band (septomarginal trabeculation) forms the “floor” of the VSD, and the truncal root overrides the crest of the ventricular septum so that the solitary truncal valve forms the “roof” of the VSD [41]. The morphology of the VSD in TA is virtually identical in to that of TOF [42], however in TA the infundibular septum is absent. TA must be distinguished from TOF/PA. In TOF/PA a remnant of the main pulmonary artery and valve can often be seen. In the most extreme form of TOF/PA, the pulmonary circulation may be supplied directly from the aorta. Thus, the distinction between TOF/PA and TA is sometimes difficult. In TA, the solitary semilunar valve, the truncal valve, is often morphologically abnormal. Though a tricuspid truncal valve is the most common anatomic subtype (69 %), other variations can occur including (in order of frequency), quadricuspid (22 %), bicuspid (9 %), and rarely valves with five leaflets (0.3 %) [43]. Because of these frequent abnormalities in valvar anatomy, truncal valve stenosis and/or regurgitation are common, and if clinically significant, they may need to be addressed surgically. Approximately 25 % of patients with TA have a right aortic arch. Other associated cardiac anomalies include aberrant origin of a subclavian artery from the descending aorta, persistent left superior vena cava to coronary sinus connection, coronary anomalies, and an atrial communication in the form of a patent foramen ovale or secundum atrial septal defect. There have been rare reports of TA with single ventricle. In the absence of aortic arch obstruction a ductus is rarely seen in this lesion.

Two classification schemes have been proposed for this malformation: one described by Collett and Edwards [44], the other by Van Praagh [42, 45]. Both are based principally upon the manner in which the pulmonary arteries arise. The classifications share similarities although there are also some important differences (Fig. 12.22).

The Collett and Edwards classification is listed as follows:

The Van Praagh classification is listed below:

Of note, the original Van Praagh classification provided a subclassification of each type: A (with a VSD) and B (no VSD). Thus a Type 1 TA could be divided into Type A1 and Type B1, depending upon the presence/absence of a VSD [42]. However given the fact that a VSD is almost always present, the Type B subclassifications are rarely seen. The reader will also note that the first two types of TA for both classification schemes are essentially identical; these are by far the common types of TA encountered. Another important point is that many TA patients are classified as “Type 1” when, in reality, the two pulmonary artery orifices are located so close together that no main pulmonary artery segment is present. This type is often referred to as “truncus arteriosus Type 1–2” or “Type 1½” (Fig. 12.22) [46].

Genetic syndromes are quite common in association with TA. In fact, 40 % of patients have 22q11 deletion syndrome; this association is particularly high in those with a right aortic arch [47]. Other chromosomal defects such as isochromosome 8q have been implicated as well [48].

The pertinent aspects of cardiac anatomy and function that should be evaluated in a patient with TA includes the following:

TEE can be very helpful in the pre-operative evaluation of the patient with TA. A careful TEE study can be used to evaluate all of the elements listed above. The ME 4 Ch view provides for evaluation of AV valve function and global assessment of ventricular performance. Withdrawal of the probe with anteflexion will demonstrate the truncal valve. Forward rotation of the multiplane angle to 30–45° will often reveal the truncal valve anatomy en face (Fig. 12.23, Video 12.18). Similar to all conotruncal defects, complementary TEE views (modified ME 4 Ch, ME Bicaval, LE Situs SAX and LE IVC LAX) establish the systemic venous connections and confirm the presence of an atrial communication, if present. The VSD can be visualized in orthogonal planes in the ME 4 Ch view (using probe anteflexion) or the ME AV LAX view (Fig. 12.24, Video 12.19). In Type 1 or 2 TA, the mid ME Asc Ao SAX and mid esophageal ascending aortic long axis (ME Asc Ao LAX) views, will often demonstrate the pulmonary arteries originating from the posterior aspect of the trunk (Fig. 12.24, Video 12.19). It can be difficult to see the entire length of the branch pulmonary arteries by TEE, but significant portions can be visualized using the aforementioned TEE views as well as the upper esophageal views (UE PA LAX, UE Ao Arch SAX).

It is important to consider that TEE probe placement can be difficult in small infants with TA especially when there is associated 22q11 deletion syndrome (Chap.​ 3).

Surgery for TA is usually performed in the neonatal period because most patients become symptomatic with congestive symptoms and pulmonary vascular obstructive disease can develop early. The type of surgical approach is dictated by the truncal anatomy. For the common forms of TA (Types 1 and 2) surgical repair consists of closure of the VSD to the truncal valve, establishing continuity between the LV and truncal valve, removal of the pulmonary arteries from the common trunk, and in most cases, placement of a conduit between the RV and the pulmonary arteries. In TA Type A4 (of Van Praagh), the interrupted arch is addressed in addition to VSD closure and RV to pulmonary artery conduit, as noted above. For all TA repairs, if the truncal valve manifests significant stenosis and/or regurgitation, surgical intervention might be necessary.

Postoperative TEE helps determine adequacy of the repair. The goals of this imaging are to assure that there is unobstructed flow from the LV to the truncal root, no significant residual VSD and unobstructed flow from the RV to the branch pulmonary arteries. Evaluation of the interatrial septum should be undertaken for residual shunting. It should be noted that in some cases, an intentional small interatrial communication remains, allowing for potential right to left shunting and the maintenance of cardiac output during the immediate postoperative period. In addition, the postbypass examination is of benefit in the evaluation of truncal valve function (estimation of residual severity of obstruction and/or regurgitation) in cases where concomitant valve interventions were performed.

The ME 4 Ch view sweeping from inferior to superior demonstrates that the VSD patch is in the correct position and color flow Doppler can be used to determine whether there is residual shunting (Fig. 12.25, Video 12.20). The intramural type VSD previously described can also occur with TA repair [23]. Assessment for a residual VSD should always occur in more than one view. The ME RV In-Out view is quite useful to demonstrate a peri-patch residual leak. In addition, the RV to pulmonary artery pathway is best seen in this view with a counterclockwise turn of the probe toward the left side of the patient. Doppler interrogation of this pathway can also be performed to assess for outflow tract obstruction. The LV to truncal valve pathway can be seen well in the ME AV LAX view along with assessment of truncal stenosis and regurgitation (Fig. 12.26, Video 12.21) [50]. When available, the deep transgastric views (DTG LAX, DTG Sagittal) can provide visualization of the LV outflow tract and proximal RV to pulmonary artery conduit, as well as excellent angles of insonation for spectral Doppler assessment. The ME 4 Ch and ME Bicaval views can be used to assess the atrial septum, and the ME 4 Ch, ME RV In-Out, and ME 2 Ch views can facilitate the evaluation AV valve function.