Lisa A. Caplan, MD and Wanda C. Miller-Hance, MD

Texas Children’s Hospital and Baylor College of Medicine

Note: All video references are included at the end of this review

Transposition of the great arteries (TGA) is the most common cyanotic cardiac lesion in newborns, accounting for 5-10% of all congenital heart disease (CHD). The malformation occurs in about 20-30 per 100,000 live births and is seen more often in male babies. Without surgical correction, TGA is almost universally fatal during the first year of life. However, contemporary outcome studies have shown that survival rates after surgical intervention are excellent and that most patients live into adulthood. ⁽¹⁾

This review focuses on the use of echocardiography in patients with TGA. A brief overview of the anatomic and physiologic features that characterize this malformation and the corresponding surgical approaches are provided as a background relevant to echocardiographic imaging.

ANATOMY AND PHYSIOLOGY

In TGA, the ventriculoarterial connections or alignments are discordant, meaning that the great arteries originate from the morphologically inappropriate supporting ventricles (the aorta from the right ventricle [RV] and the pulmonary artery [PA] from the left ventricle [LV]). ⁽²⁾ ‘Transposition’ is the most common colloquial term for this defect. The most common variant of transposition ({S,D,D}, 80% of cases) is d-TGA, in which the d refers to the dextro looping pattern of the ventricles. Looping of the heart tube to the right during cardiac development positions the morphologic RV toward the right side relative to the morphologic LV (d-bulboventricular loop). Less frequently, transposition can be seen in the setting of situs inversus and l-looped ventricles ({I,L,L}).

In d-TGA (the subject of this review), the atria are arranged normally, which is also referred to as situs solitus of the atria (morphologic right atrium [RA] on the right and morphologic left atrium [LA] on the left), and the atrioventricular connections are concordant (morphologic RA connected to morphologic RV and morphologic LA connected to morphologic LV). In contrast to the normal subpulmonary infundibulum, there is a subaortic conus, and fibrous continuity is present between the pulmonary and mitral valves, unlike in the normal heart where an aortic-mitral curtain is found. ⁽³⁾ In 80% of cases, the spatial relationship of the great arteries is characterized by a rightward aorta that is located anteriorly to a posterior and leftwards PA (Video 1); however, this anatomical aspect can vary. The most common associated anomaly is a ventricular septal defect (VSD), which is found in 40% of patients and can occur anywhere along the septum. ⁽⁴⁾ Left ventricular outflow tract (LVOT) obstruction is seen in 5-10% of cases. The term ‘simple’ transposition refers to the malformation in which the ventricular septum is intact or nearly intact in the presence of a small VSD and the LVOT is not obstructed. Other structural anomalies/variants that are associated with TGA include pulmonary valve stenosis, obstruction to the RV outflow tract (RVOT), aortic stenosis, aortic arch obstruction, atrioventricular valve abnormalities, variations in coronary artery pattern, persistent left superior vena cava, and juxtaposed atrial appendages.

The physiology in TGA is characterized by a parallel circulation, where deoxygenated blood recirculates through the body and oxygenated blood through the lungs. ^{(4, 5)} Without the presence of an anatomic site of intercirculatory shunting, the pulmonary and systemic circulations are completely separated, a condition incompatible with life. In the neonate, the foramen ovale and ductus arteriosus are communications that, if of adequate size, may allow for intercirculatory mixing. Enlargement of a small or restrictive interatrial communication by balloon atrial septostomy (BAS) may be necessary to improve systemic arterial oxygenation. Prostaglandin E₁ therapy may be used to maintain ductal patency and enhance intercirculatory mixing in affected neonates. ⁽⁶⁾ The physiology of double outlet RV with a subpulmonary VSD (Taussig-Bing malformation) is similar to that of TGA but the malformation will not be addressed in this review.

SURGICAL APPROACHES FOR TRANSPOSITION OF THE GREAT ARTERIES

Atrial Switch Operation

In the past, most patients with TGA underwent either a palliative procedure or an atrial switch operation. The atrial baffle procedures (Mustard and Senning operations) reroute the systemic venous return to the LV and the pulmonary venous return to the RV, thus allowing for physiologic correction in transposition. ⁽⁷⁾ Most adult patients are likely to have undergone this type of repair. Long-term problems related to these interventions led to the evolution of the surgical approach for this lesion. ⁽⁸⁾

Arterial Switch Operation

The arterial switch operation (ASO) is the current preferred surgical strategy for patients with TGA. This single-stage procedure is performed in the first few weeks of life and involves transecting both arterial roots above their respective sinuses, switching the great arteries to restore the normal ventriculoarterial connections, and translocating the coronary vessels to the ‘neoaortic’ root. Outcomes after the operation are generally excellent. ⁽⁸⁾

Strategies for Transposition with VSD and Pulmonary Stenosis/LVOT Obstruction

The concomitant presence of a VSD and pulmonary stenosis/LVOT obstruction in the setting of TGA requires alternative surgical management strategies. ⁽⁹⁾ One such approach is the Rastelli procedure, which involves creating an intracardiac patch or tunnel that reroutes the LV output through the aorta while closing the interventricular communication, and placing an extracardiac tube or conduit between the RV and PA. The ‘Réparation a l’etage ventriculaire’, also known as the REV procedure, offers reconstruction of the RVOT without the use of extracardiac prostheses. ⁽¹⁰⁾ Another approach in complex forms of TGA is the Nikaidoh procedure. This repair consists of harvesting the aortic root from the RV while the coronaries are still attached, resecting the LVOT obstruction (dividing the outlet septum and excising/oversewing the pulmonary valve), reconstructing the LVOT (with the posteriorly translocated aortic root and the VSD patch), and establishing the RV to PA connection. ⁽¹¹⁾ Although more technically demanding than other surgical options, the Nikaidoh operation may be less likely to result in recurrent LVOT obstruction, as suggested by intermediate outcomes data. ⁽¹²⁾

 

ROLE OF ECHOCARDIOGRAPHY

The important role of echocardiography in patients with TGA is well established. ^{(4, 13, 14)} The recently published guidelines for multimodality imaging have described in detail the significant contributions of echocardiography in the diagnosis, surgical planning, and long-term surveillance of patients with TGA. ⁽¹⁵⁾ Selected aspects of the application of echocardiography in TGA as related to cardiac anesthesia practice are highlighted in the following sections.

 

Fetal Echocardiography

Fetal cardiac imaging allows for the prenatal diagnosis of TGA but usually requires the expertise of a specialist. ⁽¹⁶⁾ In the antenatal period, echocardiography can be used to provide early detection, which can affect counseling and potentially alter clinical outcomes. ^(17–20)

 

Transthoracic Echocardiography

Transthoracic echocardiography (TTE) plays a major role in characterizing the anatomic and hemodynamic abnormalities in the neonate with transposition and, in most cases, provides all the necessary information for medical management and surgical planning. ⁽¹³⁾ In fact, the need for additional cardiovascular imaging modalities for this lesion is highly unusual in the neonatal period. ⁽²¹⁾

Diagnostic Applications

A complete TTE evaluation in the neonate with TGA typically consists of two-dimensional (2D) imaging, Doppler interrogation (pulsed, continuous, and color modalities), M-mode, and tissue Doppler. The diagnosis is based on the sequential segmental analysis that characterizes the detailed assessment of CHD and requires multiple cross-sectional imaging of cardiac and vascular structures. The hallmark feature of the interrogation is the demonstration of the presence of concordant atrioventricular connections and discordant ventriculoarterial connections.

The anatomic features characteristic of the classic malformation as depicted by TTE include

• The posterior ventricle of LV morphology gives rise to a great artery, the PA, which acutely angulates or dives towards the lungs, and the aorta originates from the anterior chamber of RV morphology on parasternal long-axis (LAX) imaging (Video 2). Shunting across a patent ductus arteriosus (PDA), as identified by color flow Doppler, confirms the posterior great artery as the PA (Video 3). Fibrous continuity is present between the mitral and pulmonary valves. At the base of the heart, the posterior great artery bifurcates into two branches on parasternal short-axis (SAX) imaging (Video 4).
• The discordant ventriculoarterial connections are confirmed in other views that allow for interrogation of the ventricles, the outflow tracts, and the great arteries. Apical and subxiphoid imaging are particularly helpful in this assessment. The 2D examination requires sweeping the imaging plane between posterior and anterior positions. The atrioventricular connections are examined from a posterior view and documented as being normal (concordant) after examining the morphologic features unique to the atrial and ventricular chambers. More anterior transducer angulation demonstrates the abnormal ventriculoarterial connections with the smooth-walled LV (on the patient’s left) giving rise to a vessel, the PA, which bifurcates into two branches (Video 5). Ductal flow into the PA may also be seen in this view (Video 6). From a slightly more anterior plane, a triangular-shaped RV with prominent muscle bundles (on the patient’s right) can be seen giving rise to an elongated vessel (the aorta, Video 7), which arches on more superior scanning.
• The great arteries course in parallel alignment, in contrast to the normal heart where they intertwine around each other. This is best seen in the parasternal LAX view, where both great arteries can be displayed longitudinally at the same time (Video 2), and as the arterial trunks are examined in the apical and subxiphoid views. In SAX imaging, the spatial great artery relationship in TGA results in the arterial roots being displayed in cross-sections, appearing as two circles (Video 8). In contrast, the wrapping of the great arteries around each other in the normal heart produces a ‘circle-sausage appearance.’
• The abnormal position of the arterial roots (aorta, anterior and rightward and PA, posterior and leftward in most cases) is seen with parasternal SAX imaging (Video 8). The aortic valve is usually superior to the pulmonary valve due to the underlying conus or muscular infundibulum that supports the aorta in TGA.

Additional relevant aspects of the examination include

• Assessment of the atrial septum and ductus arteriosus

Determining the adequacy of cardiac mixing is one of the most important components of the initial evaluation in the neonate with TGA. The atrial septum is optimally examined on subxiphoid imaging to assess the presence and size of the communication. Color flow imaging provides information on the direction and magnitude of the atrial level shunting (Video 9), and spectral Doppler allows for the determination of the mean pressure gradient across the interatrial septum. The PDA can be examined from parasternal and suprasternal notch imaging to determine its patency, size, and flow (Video 10).

• Characterization of co-existing anomalies

Echocardiography allows for the detailed characterization of associated lesions in TGA such as VSD(s), LVOT obstruction, aortic arch obstruction, and tricuspid valve abnormalities. This examination requires complementary imaging obtained by multiple cross-sectional views at various levels. The entire interventricular septum (IVS) is examined to determine the presence of defect(s) and the type, size, flow direction, and velocity (Videos 11 and 12). If multiple defects are present, their identification before surgical intervention can be challenging given the equal systolic ventricular pressures. Documenting the patency of outflow tracts, the PAs, and the aortic arch is an important aspect of the examination. When an obstruction is present, its nature is characterized by comprehensive 2D imaging. Hemodynamic assessment of the severity of the obstruction is performed in views that allow for parallel alignment of the spectral Doppler signal with the direction of flow. Morphologic and functional information on the semilunar and atrioventricular valves (assessment of annulus size, patency, and competence) requires the combined use of 2D and Doppler imaging.

• Delineation of coronary artery anatomy

Coronary artery anatomy in patients with TGA is highly variable, and certain patterns can affect surgical outcome. ^{(22, 23)} Cross-sectional views in the parasternal, apical, and subxiphoid windows are particularly helpful in this assessment. ⁽²⁴⁾ The branching pattern of the coronary arteries is determined by using a combination of views and sweeps. In the ‘usual’ arrangement, the right coronary artery (RCA) arises from the right sinus of Valsalva and the left main coronary artery from the leftward sinus (Videos 1 and 13), which then branches into the left anterior descending (LAD) and circumflex (Cx) arteries. Three main patterns account for most cases: 1) the usual coronary anatomy as described above; 2) origin of the Cx from the RCA, in which case the Cx courses behind the PA (Video 14); and 3) a single RCA. An important aspect of the evaluation is characterizing the coronary ostia and the proximal course of these vessels to identify abnormalities such as an intramural course, where a coronary artery travels within the wall of the aorta, given the potential risk factor of this finding in the coronary translocation. ^(25–28) Features suggestive of an intramural course include a coronary artery, originating from the opposite sinus of Valsalva, that travels between the semilunar valves; a juxtacommissural origin at an acute angle from the aortic root; or a high take-off from the sinotubular junction. ⁽²⁹⁾

• Assessment of chamber size, systolic function, and determination of left ventricular preparedness

Preoperative TTE includes the evaluation of ventricular size and systolic function and is usually performed by qualitative and quantitative assessment. The timing of corrective surgery is important to avoid the prolonged effects of pulmonary overcirculation in the neonate and the progressive regression of LV mass, which increases perioperative risks. The physiology of the neonate with transposition and the ability of the LV to support the systemic circulation after the first few weeks of life depend on factors such as the size and nature of flow across the PDA, relative pulmonary and systemic vascular resistances, the size and presence of associated intracardiac communications, and the presence of LVOT obstruction. ⁽³⁰⁾ Of relevance in the echocardiographic examination is the determination of the suitability of the LV to operate as the systemic pump after the ASO.

The concept of ‘LV retraining’ arose before the development of the neonatal switch operation, when this intervention was typically carried out in two stages (the initial stage consisting of PA banding and placement of an aortopulmonary shunt, followed by the ASO at a later time). ^(31–34) Today, this strategy of LV retraining is considered more within the context of the surgical management of congenitally corrected TGA. ⁽³⁵⁾

The specific criterion for determining what constitutes a ‘prepared’ LV is a controversial topic. Nonetheless, in infants with simple transposition who present in the late neonatal period or beyond, the following echocardiographic parameters are examined to ensure the likelihood a good outcome after the ASO: LV muscle mass, posterior wall thickness, shape of the IVS, and the presence of coexisting anomalies such as a PDA and LVOT obstruction. Estimates of LV muscle mass are usually obtained from 2D-oriented M-mode echocardiography, or alternatively, by MRI. An LV muscle mass < 35 g/m² is generally considered an indication for LV retraining and the need for remodeling optimally to 50-65 g/m². ^{(33, 34)} The geometry of the IVS reflects the pressure gradient between the two ventricles and is directly related to the relative LV afterload and pulmonary vascular resistance. LV preparedness is considered present when the chamber displays a circular configuration with convexity of the IVS towards the RV on SAX imaging of the ventricles. Indications for ventricular retraining would include a septum that bulges right to left or has a banana-shape configuration. Aside from echocardiographic criteria, other signs of LV preparedness might be considered.

 

Role of Echocardiography During Balloon Atrial Septostomy

A BAS is indicated in the neonate with transposition who has a low systemic arterial oxygen saturation related to inadequate mixing at the atrial level. In this procedure, a balloon-tipped catheter is introduced into the LA, usually through a patent foramen ovale or a small interatrial communication, and forcefully withdrawn across the interatrial septum into the RA under either fluoroscopic or echocardiographic guidance (Video 15). ^(36–38) In some cases, the catheter intervention can be life-saving. The procedure may be performed in the cardiac catheterization laboratory or at the bedside. ⁽³⁹⁾ End points for the intervention include a 10% increase in arterial oxygen saturation, a very minimal pressure gradient between the two atria, or an increase in the diameter of the atrial septal defect of more than a third of its original size. Subxiphoid 2D imaging combined with color and pulsed-Doppler is ideal for monitoring during the procedure and to ensure adequacy of the defect. The size of the communication, the mobility of adjacent septal tissue, and the magnitude and direction of flow across the defect are the main parameters assessed.

 

Transesophageal Echocardiography

Indications for transesophageal echocardiography (TEE) in patients with TGA relate to its use in the operative setting, in the cardiac catheterization/electrophysiology laboratory, and elsewhere. ⁽⁴⁰⁾ The benefits of intraoperative TEE include confirmation of the structural abnormalities, exclusion of suspected pathology, monitoring (ventricular preload, adequacy of cardiac dearing, ventricular function-global and regional), assessment of the surgical results, and guidance on the necessity of returning to bypass. If TEE is not feasible, epicardial echocardiography offers an alternative imaging option. In addition to the intraoperative setting, TEE can be useful in patients with TGA for guiding procedures in the cardiac catheterization or electrophysiology laboratory (e.g., balloon or blade atrial septostomy, closure of shunts, dilation of baffles, and arrhythmia mapping and ablation procedures). ⁽⁴¹⁾ Moreover, TEE may be beneficial in patients who have suboptimal TTE windows, as may be the case in adolescents or adults, particularly after surgery, and in those who require imaging to exclude intracardiac thrombus before electrical therapy for a cardiac rhythm disturbance.

Comprehensive TEE in TGA includes the use of 2D/3D imaging, spectral Doppler, color flow mapping, and possibly contrast echocardiography. ⁽⁴²⁾ A detailed study encompasses multiple planes of interrogation and sweeps between the various planes. When a study is performed to address a specific question, a more focused examination may be undertaken. The following discussion highlights general aspects of the TEE evaluation, mostly when used in the intraoperative setting.

Presurgical Examination

Goals of the 2D/3D examination:

• Assessment of atrioventricular and ventriculoarterial connections (Midesophageal [ME] 4 Chamber [Ch], ME 2 Ch, ME 5 Ch, ME LAX, Transgastric [TG], and Deep Transgastric [DTG] views; Video 16)
• Characterization of associated pathology such as intracardiac communications (Video 17) and outflow tract obstruction. If a VSD is present, the defect is defined in terms of location, extension, and proximity to the outflow tracts and semilunar valves (ME 4 Ch, ME 5 Ch, ME LAX, ME RV Inflow-Outflow [In-Out], ME Bicaval [Bic], TG, and DTG views; Video 18). If ventricular outflow tract obstruction is present, its nature (fixed versus dynamic) and severity are determined (ME 4 Ch, ME 5 Ch, ME LAX, ME RV In-Out, TG, and DTG views; Video 19)
• Morphology of the atrioventricular and semilunar valves (ME 4 Ch, ME 2 Ch, ME 5 Ch, ME Mitral Commissural, ME LAX, and ME Aortic Valve SAX and LAX views)
• Determination of ventricular geometry and septal configuration (ME 4 Ch and TG SAX views)
• Estimation of ventricular size and systolic function (ME 4 Ch, ME 2 Ch, and TG views)
• Confirmation of coronary artery pattern (ME SAX views and ME Sweeps)

Goals of the Doppler examination:

• Characterization of intracardiac communications (size, location, and shunting pattern across the atrial and ventricular septum). Flow at the atrial level is usually from the LA into the RA or bidirectional (Video 17). Flow across a VSD is from the RV to the LV (Video 18), opposite of what is expected in the normal heart
• Assessment of outflow tract patency and gradients (Video 19)
• Evaluation of valvar competence (atrioventricular and semilunar valves) (Video 20)

Examination after surgical procedures/catheter interventions

For atrial switch (atrial baffle) procedures:

• TEE may be superior to TTE in evaluating systemic and pulmonary venous baffles for obstruction or leaks. This is best performed in the ME views with the use of sweeps. In the ME 4 Ch view, probe anteflexion/retroflexion and right/left rotation allows for examination of the pulmonary and systemic venous baffles (Video 21). In the ME Bic view, probe advancement/withdrawal and right/left rotation display the inferior and superior limbs of the systemic venous baffle. Spectral (mean pressure gradient estimation) and color flow Doppler imaging facilitate the evaluation of the obstruction site and the determination of severity of pathology.
  • Evaluation of systemic venous baffle for obstruction: The superior limb of the baffle is the most common site of systemic venous obstruction. In the absence of obstruction in this region, injection of agitated saline or an equivalent agent into a peripheral or central vein in the upper body produces a contrast effect that rapidly courses from the superior vena cava into the systemic venous atria, and no contrast should be seen from the inferior (inferior vena cava) aspect of the baffle. In the case of severe obstruction of the superior venous limb, the contrast agent is diverted through collaterals to the lower aspect of the systemic venous baffle.
  • Identification of intracardiac shunting: In addition to color flow Doppler interrogation (Video 22), injection of agitated saline (or an equivalent) into a peripheral or central venous catheter is useful for identifying baffle leaks as intermittent right-to-left shunting may be evidenced by opacification of the pulmonary venous atrium (Video 23). This may also be helpful in assessing communications at the ventricular level.
• Assessment of atrioventricular valve regurgitation, particularly the systemic tricuspid valve (ME 4 Ch, ME 5 Ch, and ME Modified Bic Tricuspid Valve views)
• Evaluation of ventricular function, particularly the systemic RV (ME 4 Ch, ME 5 Ch, ME RV Inflow-Outflow, TG, and DTG views)
• Monitoring and guidance during transcatheter-based interventions of obstructed venous pathways (dilation and stenting), baffle leaks, closure of intracardiac defects, and electrophysiologic procedures

For the ASO:

• Evaluation of atrioventricular and semilunar valves for regurgitation (ME 4 Ch, ME 2 Ch, ME 5 Ch, ME LAX, ME RV In-Out, and DTG views; Video 24)
• Interrogation of outflow tracts (including flow across aortic and PA anastomoses) and branch PAs to exclude obstruction ⁽⁴³⁾ (ME Ascending Aorta LAX and SAX, ME 5Ch, ME LAX, ME RV In-Out, and DTG views)
• Identification and characterization of residual shunts (ME 4 Ch, ME 5 Ch, ME LAX, ME RV In-Out, ME Bic, TG, and DTG views)
• Assessment of global and segmental ventricular function (ME 4 Ch, ME 2 Ch, and TG views; Video 25). The TG views are particularly useful for determining overall ventricular function and regional wall motion abnormalities. ⁽⁴⁴⁾

For procedures addressing TGA in association with a VSD and LVOT obstruction:

• Evaluation of atrioventricular and semilunar valves for regurgitation
• Identification and characterization of residual intracardiac shunting (atrial and ventricular levels) (Videos 26 and 27)
• Interrogation of the pathway between the LV and the aorta to exclude systemic outflow obstruction (ME 5 Ch, ME LAX, TG, and DTG views; Videos 28-30)
• Evaluation of the RVOT reconstruction (ME RV Inflow-Outflow, ME LAX, and DTG views; Video 31)
• Assessment of global and segmental ventricular function

 

Use of Echocardiography During Routine Surveillance After Surgical Intervention

In current practice anesthesiologists will encounter patients with TGA who have undergone one or more surgical interventions as noted above. Regardless of the specific procedure(s), this patient population is at risk for residual pathology and sequelae that require lifelong surveillance by a cardiologist following recommended guidelines. ⁽¹⁾ Echocardiography plays a pivotal role in long-term follow-up by facilitating the identification and characterization of postoperative problems in this patient group (Table).

Table

Postoperative Sequelae in TGA as Assessed by Surveillance Echocardiography

 

Arterial Switch Operation	Atrial Switch Operation	Interventions for Complex TGA
Supravalvar and branch PA stenosis (most common problem)   Neoaortic root dilation   Neoaortic regurgitation   Residual shunts   Residual aortic arch obstruction   Coronary issues resulting in ischemia, LV dilation, and functional impairment (global/regional wall motion abnormalities)   Pulmonary hypertension (assessed by parameters such as TR or PR jet velocity, configuration of IVS) Atrial baffle leaks (left-to-right shunts)	Atrial baffle stenosis: systemic venous baffle (superior limb most common site of obstruction) and pulmonary venous baffle   TV regurgitation (systemic AV valve)   Systemic RV dysfunction   Outflow tract obstruction   Pulmonary hypertension (assessed by parameters such as MR jet velocity and configuration of IVS; as PA pressure increases septum bows towards systemic RV) Conduit dysfunction stenosis/regurgitation (depending on type of RVOT reconstruction)	RVOT obstruction/PA stenosis   Residual shunts (particularly at ventricular level)   LVOT obstruction (baffle obstruction after Rastelli operation)   Coronary issues (related to distortion of vessels or if reimplantation required in Nikaidoh operation)

 

Abbreviations:

AV atrioventricular, IVS interventricular septum, LV left ventricle, LVOT left ventricular outflow tract, MR mitral regurgitation, PA pulmonary artery, PR pulmonary regurgitation, RV right ventricle, RVOT right ventricular outflow tract, SVC superior vena cava, TV tricuspid valve, TR tricuspid regurgitation

 

Summary

The management of patients with TGA has evolved significantly since the malformation was first described in the eighteenth century. ⁽⁴⁵⁾ Studies have extensively documented the importance of echocardiography in the comprehensive anatomic and hemodynamic assessment of this congenital cardiac lesion as well as its role in preoperative planning, intraoperative monitoring, and postoperative surveillance. This review highlights selected aspects of the applications of this imaging modality in patients with TGA. As ultrasound technology continues to evolve, its usefulness in all patients with congenital cardiovascular malformations including those with TGA will undoubtedly increase.

 

VIDEOS

Video 1.       Intraoperative video recording of a neonate with d-transposition of the great arteries. Note the origin of the aorta from the anterior right ventricle and the pulmonary artery from the posterior left ventricle. The spatial orientation of the great arteries depicted represents the most common arrangement. Note the origins of the coronary arteries from the right and left sinuses of Valsalva facing the pulmonary artery.

 

 

Video 2.       Abnormal ventriculoarterial connections in TGA (parasternal long-axis imaging). Note the parallel orientation of the great arteries. Ao aorta, LV left ventricle, PA pulmonary artery, RV right ventricle.

 

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