Echocardiography in Pediatric and Adult Congenital Heart Disease, 2nd Ed.

12. Univentricular Atrioventricular Connections

Patients with only one ventricle (i.e., “functional single ventricle,” or the functionally univentricular heart) comprise a very heterogeneous group. With the Fontan operation as the preferred definitive palliation in patients with a univentricular heart, it remains important to determine if a given ventricular chamber is inadequate for support of either systemic or pulmonary circulation. Often, the atrioventricular (AV) connection is the determining factor.

Nomenclature and classification of the univentricular heart have long been subjects of debate and controversy, with terms such as “single ventricle,” “univentricular heart,” “univentricular atrioventricular connection,” and “double-inlet ventricle” being used over the years. Van Praagh and colleagues originally defined a univentricular heart as one ventricular chamber that receives both tricuspid and mitral valves or a common AV valve; hearts with one absent AV valve (including mitral and tricuspid atresia) were not included in this original review. Van Praagh et al. also pointed out that although these patients have a functionally univentricular heart, there are usually two ventricular chambers; thus, a “true” univentricular heart is exceedingly rare. Anderson and colleagues introduced the term “univentricular atrioventricular connection” and applied this to hearts where the AV connection was committed to one ventricle. They subsequently proposed that “univentricular heart of left ventricular type” be applied to hearts where the dominant ventricle was a morphologic left ventricle (LV) and “univentricular heart of right ventricular type” be applied to the dominant right ventricle (RV). Further characterization of the ventricular mass as consisting of three regions (inlet, trabecular, and outlet regions) was included. Assessment of a ventricle in this way could aid in the determination of the adequacy of a given ventricle, that is, whether a ventricle was complete or incomplete. However, a hypoplastic ventricle with all three components present does exist. In more recent publications on nomenclature, Jacobs and Anderson simply refer to the “functionally univentricular heart,” wherein the emphasis was placed on the inadequacy of one or the other ventricle to support the pulmonary or systemic circulation. Regardless of the preferred nomenclature, a segmental approach to echocardiographic evaluation is necessary in all cases, defining connections and relationships to provide the clinician with relevant information.

This chapter will cover the three main types of univentricular AV connection that produce a functionally univentricular heart: tricuspid atresia, mitral atresia (or hypoplastic left heart syndrome), and double-inlet LV (DILV). A brief review of the hypoplastic LV or mitral stenosis in the setting of multiple left-sided obstructive lesions is included. Typically, all of these conditions are the result of an absent, hypoplastic, or atretic AV connection.

All patients with a functionally univentricular heart require careful anatomic assessment to plan for a staged surgical approach that will provide definitive palliation. Although nomenclature may be debated, it is important that there is consensus regarding such nomenclature at the institutional level so that clinicians understand each other and are able to communicate clearly about the nature of complex congenital heart disease. A complete description of segmental anatomy and physiology, which inherently lends itself to clinical application and decision making, is most useful for the broadest audience.

TRICUSPID ATRESIA

Tricuspid atresia is the third most common form of cyanotic congenital heart disease, with a prevalence of 0.3% to 3.7%, and is characterized by absence of a direct communication between the right atrium (RA) and the RV (Fig. 12.1). There is a univentricular AV connection with the dominant ventricle having left ventricular morphology. The anatomic form of atresia is most commonly fibromuscular; less commonly, it is membranous, valvar, or Ebstein-like with valvar atresia. In the majority of patients, the floor of the RA is entirely muscular with separation from the hypoplastic RV by fibrofatty tissue. Although we use the term “tricuspid atresia” for lesions with an echogenic plate-like area beneath the floor of the right atrium and above the right ventricle, this echogenicity is usually not the result of an atretic tricuspid valve but rather it results from fibrofatty tissue in the AV groove. Therefore, tricuspid atresia is likely a result of failure of formation of the tricuspid valve rather than fusion of formed tricuspid valve leaflets. True atresia of tricuspid valve leaflets as seen in the atretic tricuspid valve in Ebstein anomaly is rare.

Figure 12.1. Pathologic specimen in tricuspid atresia showing the atretic fibrofatty tricuspid valve (arrow). The left atrium (LA) and left ventricle (LV) are enlarged. The right ventricle is extremely hypoplastic and appears as a “slit-like” space (asterisk). RA, right atrium.

Historically, based on the great artery relationship, tricuspid atresia is classified into three types, with subclassification based on the anatomy of the ventricular septal defect (VSD) and pulmonary valve (Table 12.1). However, to avoid miscommunication, the echocardiographer should describe the anatomy and physiology in detail.

Associated Anomalies

An opening in the atrial septum, either a patent foramen ovale or a secundum atrial septal defect (ASD), is obligatory for survival. Occasionally, the atrial septum is restrictive. Rarely, a primum ASD may be present. Thirty percent of patients with tricuspid atresia will have additional associated cardiac anomalies, including left superior vena cava (SVC) (16%), juxtaposed atrial appendages (more common with transposed great arteries), and coarctation of the aorta (8%). Associated cardiovascular anomalies are more common with transposed great arteries (63%), compared with normally related great arteries (18%). Also, approximately 20% of patients will have extracardiac anomalies, including gastrointestinal and neurologic defects.

Clinical History

The majority of patients with tricuspid atresia present with cyanosis. Patients with tricuspid atresia and normally related great arteries (ventriculoarterial concordance) have a high incidence of subvalvular or valvular pulmonary stenosis (less commonly, atresia). Clinical presentation depends on the amount of pulmonary blood flow, which is proportional to the size of the VSD and the degree of pulmonary valvar/subvalvular stenosis. If there is no significant pulmonary stenosis or restriction of the VSD, these patients may present between 4 and 8 weeks of age with signs and symptoms of pulmonary overcirculation (similar to the infant with a large VSD) and only mild hypoxemia due to the large amount of pulmonary blood flow. If not recognized early, these infants are at risk for longer-term complications from hypoxemic pulmonary overcirculation and elevated vascular resistance. In the presence of pulmonary atresia or critical pulmonary stenosis, closure of the ductus arteriosus results in severe cyanosis, hypoxemia, and acidosis, and, if not treated promptly, may result in death. Patients with transposed great arteries (ventriculoarterial discordance) typically have unobstructed pulmonary blood flow; as pulmonary vascular resistance drops in the neonatal period, these infants may also present with signs of congestive heart failure and pulmonary edema. However, if there is significant aortic arch obstruction or critical restriction of the VSD (supplying systemic output), once the ductus arteriosus closes, cardiovascular collapse and shock will develop.

Echocardiographic Examination of Tricuspid Atresia

Echocardiography in the neonate with tricuspid atresia provides comprehensive diagnostic information. Diagnostic cardiac catheterization is rarely needed. Careful attention to the absent right AV connection, the arrangement of the great arteries, the nature of the communication between the LV and hypoplastic RV, and the presence of aortic arch or pulmonary artery (PA) obstruction should provide the clinician with complete diagnostic assessment, allowing for accurate planning of staged surgical palliation.

Subcostal Views

Subcostal four-chamber (coronal) view Subcostal examination begins with a determination of abdominal viscera and atrial situs in all patients. Subcostal four-chamber (coronal) views will show dilation of the RA with absence of the connection to the RV (Fig. 12.2A [Video 12.1A]). As foreshortening of the RV may occur in this plane, short-axis (sagittal) plane imaging is useful for “three-dimensional” assessment of right ventricular size. The atrial septum is best visualized from subcostal imaging planes, and characterization of the ASD should be performed. Prominent Eustachian valve tissue may be present but typically does not contribute to obstruction. Color Doppler will show a right-to-left shunt from the RA to the left atrium (LA) and no flow from the RA to the RV. It is unusual for the ASD to be restrictive, but pulsed-wave Doppler interrogation should be used to evaluate the RA-to-LA gradient, tracing the signal over three cardiac cycles to determine a mean gradient. An atrial shunt is obligatory for survival; therefore, a restrictive ASD may result in severe hemodynamic compromise requiring urgent septostomy. Evaluation of the great arteries from multiple imaging planes to determine ventriculoarterial connections is important (Fig. 12.2BC [Video 12.1B, C]). An enlarged, posterior great artery (PA) that bifurcates early is consistent with transposed great arteries (ventriculoarterial discordance) (Fig. 12.3AB [Video 12.2A]). Examination of the ventricular septum may provide information on the size and location of the VSD, but orthogonal views will be needed. In tricuspid atresia, the VSD is usually muscular; rarely, the VSD can be doubly committed and subarterial or outlet in nature. The mitral valve and left ventricular function can be assessed initially from the four-chamber subcostal plane.

A left-juxtaposed right atrial appendage is visualized in the subcostal four-chamber scan plane. Both atrial appendages are located more leftward than normal. Echocardiographers should be alert to a left-juxtaposed right atrial appendage when visualizing an abnormal convexity of the atrial septum to the left or a transverse orientation of the septum when imaging posteriorly from the subcostal four-chamber plane. Further anterior angulation of the probe will reveal the connection of the RA to the leftward right atrial appendage. Juxtaposition of the appendages should not be confused with an ASD.

Figure 12.2. Tricuspid atresia with normally related great arteries; subcostal views. A: “Four-chamber” (coronal) view showing moderate-sized secundum atrial septal defect (asterisk), atretic tricuspid valve (arrow), hypoplastic right ventricle (RV), and dilated left ventricle (LV). B: Four-chamber view, angled anteriorly, illustrating the large ventricular septal defect (asterisk). Aortic (Ao) origin from LV in normally related great arteries. C: Short-axis (sagittal) view showing anterior RV, posterior LV, and muscular ventricular septal defect (asterisk). In normally related great arteries, the pulmonary artery (PA) arises anteriorly from the RV and bifurcates early. LA, left atrium; RA, right atrium (Video 12.1).

Subcostal short-axis (sagittal) view Subcostal short-axis views demonstrate the absent connection between the floor of the RA and the hypoplastic RV. Orthogonal views are very useful for evaluation of the atrial septal anatomy. Again, the right-to-left shunt should be unrestricted in the setting of an adequate interatrial communication. Rightward angulation of the transducer facilitates evaluation of the absent communication between the RA and the hypoplastic RV, and the size of the RV is more easily assessed in the subcostal short-axis view than in the four-chamber imaging plane (Figs. 12.2C and 3CD). Evaluation of the size of the VSD between the LV and hypoplastic anterior RV is important for documenting sites of obstruction to arterial outflow. Careful sweeps from right to left are important to obtain complete information about the location and degree of right ventricular outflow obstruction. Assessment of the ventriculoarterial connection is performed from the short-axis view; again, the proximal bifurcation of the PA should be assessed. The presence of parallel great arteries suggests transposition (ventriculoarterial discordance). A small anterior aorta should prompt a careful evaluation for coarctation of the aorta from additional views.

Parasternal Views

Parasternal long axis Parasternal long-axis scans typically demonstrate a small anterior RV and a large posterior LV (Fig. 12.4A). This scan plane also provides excellent views of the ventricular septum. The size and position of the VSD should be noted (see Fig. 12.4A). The position and origin of the great arteries are confirmed. In the presence of transposed great arteries, the arteries appear parallel in their proximal course from the ventricles, with the posterior vessel (PA) bifurcating early (Fig. 12.5A). If the VSD is present in the outlet portion of the septum, anterior deviation of the septum (seen most commonly with normally related great arteries) may produce subpulmonary obstruction. Posterior deviation is seen more often with transposed great arteries. Muscular ridges or membranes can also cause ventricular outflow obstruction and should be evaluated from multiple imaging planes. Anterior angulation of the transducer toward the patient’s left shoulder may bring the right ventricular outflow tract (RVOT) into view. Doppler and color Doppler evaluation of the gradient from the LV to RV and into the RVOT should be used to provide information about the degree of restriction, either to the PA (for an estimation of the PA pressure) or to the anterior aorta in transposition.

Figure 12.3. Tricuspid atresia with transposed great arteries; subcostal long-axis (coronal) views. A: Dilated left ventricle (LV), hypoplastic right ventricle (RV), and a small muscular ventricular septal defect (asterisk). Note the pulmonary artery (PA) arising from the LV with early bifurcation (arrowhead). B: Color Doppler imaging in the same patient demonstrating flow in the PA bifurcation (arrow). C: Slight anterior angulation of the transducer demonstrates the LV, hypoplastic RV, and the restrictive ventricular septal defect (asterisk). The anterior aorta (Ao) arises from the hypoplastic RV. D:Color Doppler demonstrating the flow across the small ventricular septal defect (arrow), antegrade into the aorta (Video 12.2).

Figure 12.4. Tricuspid atresia with normally related great arteries; parasternal views. A: Long-axis view showing small anterior right ventricle (RV) and dilated posterior left ventricle (LV). There is a muscular ventricular septal defect (asterisk). B: Short-axis view at the cardiac base demonstrating normally related great arteries, an atretic tricuspid valve (arrow), and a secundum atrial septal defect (asterisk). C: Short-axis view at the level of the mitral valve (M) demonstrating the dilated LV communicating with the hypoplastic RV through a large muscular ventricular septal defect (asterisk). Ao, aorta; PA, pulmonary artery (Video 12.3).

Visualization of the atrial septum in a perpendicular orientation from the long-axis view may be consistent with a left-juxtaposed right atrial appendage. A dilated coronary sinus should alert the echocardiographer to the possibility of a left SVC returning to the coronary sinus (which has implications in planning for the bidirectional cavopulmonary shunt as palliation).

Parasternal short-axis view The parasternal short-axis view is useful for further characterization of the hypoplastic RV and VSD and position of the great arteries (Figs 12.4B and 5B). Left ventricular function should be evaluated. Scanning apically from the base of the heart toward the midventricular level, the right ventricle is seen in front of the dominant, large LV (Fig. 12.4C). In addition to orthogonal subcostal views, the size of the RV and the anatomy of the VSD can be assessed in the short-axis plane (Fig. 12.4C). The presence of additional VSDs should be assessed with both imaging and color Doppler. Pulsed-wave Doppler interrogation can provide an estimation of the gradient between the LV and RV as well as aid in assessing the restrictive VSD. Scanning superiorly toward the base of the heart to the level of the great arteries will again confirm their arrangement. If transposed, both great vessels are seen in short-axis, represented by two semilunar valves seen in the same imaging plane (Fig. 12.5B). In transposition, one can evaluate whether the anterior aorta is located rightward (d-transposition, more common) or leftward (l-transposition, less common).

It is necessary to evaluate the degree of restriction of the RVOT in the short-axis view. Color Doppler and pulsed-wave Doppler should be used in this assessment. With normally related great arteries, the presence of a large PA suggests that adequate or generous pulmonary blood flow is present. If the PA is very small or diminutive, it is necessary to confirm the presence of antegrade flow from the RV to the PA. Rarely, pulmonary atresia coexists with tricuspid atresia, creating a ductal-dependent critical condition. The ductus arteriosus should be assessed fully. Typically, a trifurcation view of the ductus, left PA, and right PA can be obtained in a high left parasternal plane.

Figure 12.5. Tricuspid atresia with transposed great arteries; parasternal views. A: Long-axis view showing the parallel orientation of the great arteries classically seen in transposition, with an anterior aorta (Ao); posterior pulmonary artery (PA) originating from the dilated left ventricle (LV). B: Short-axis view at the cardiac base showing both semilunar valves in short-axis at the same level, again consistent with transposition of the great arteries. The aortic valve (Ao) is hypoplastic and located anterior and slightly rightward, whereas the pulmonary valve (PA) is dilated and located posterior and leftward. LA, left atrium (Video 12.4).

Apical Views

An apical four-chamber view provides excellent definition of the absent right AV connection (Fig. 12.6A [Video 12.5A]). Angling the transducer posteriorly demonstrates the muscular atresia of the tricuspid valve appearing as an echo-dense plate of tissue in the floor of the RA. Again, assessment of the hypoplastic RV and its communication from the LV (VSD) is important. In the presence of juxtaposed atrial appendages, one can again see an abnormal atrial septal configuration. Mitral valve morphology and function are well visualized from the apical approach. Angling the transducer anteriorly facilitates development of a “five-chamber view,” providing further assessment of the outflow tracts and sites of potential obstruction (Fig. 12.6BC). The origin, size, and position of the great arteries and outflow tracts again are assessed in light of information obtained from all of the previous views. The size of the VSD and any evidence of obstruction are evaluated with both pulsed-wave and color Doppler, attempting to align the transducer beam in a parallel fashion with the VSD or outflow tracts. Para-apical imaging, directing the transducer more anteriorly toward the anterior great artery, can also facilitate assessment of obstruction and gradients.

Suprasternal Views

Beginning with the long-axis view of the aortic arch, careful evaluation for evidence of arch obstruction is very important. In the setting of transposition of the great arteries, coarctation is more common, particularly when the VSD is restrictive and the aorta is small (Fig. 12.7AB [Video 12.6A]). Critical coarctation in the neonate requires immediate recognition so ductal patency can be maintained appropriately until surgical intervention can be performed. Doppler interrogation of the coarctation gradient is unreliable due to the ductal flow distal to the site of coarctation (Fig. 12.7C). In the setting of coarctation of the aorta, a large ductal arch is present (this can be visualized from multiple views, in addition to suprasternal imaging). The native, diminutive aorta may insert “end-on-side” onto the large ductal arch (see Fig. 12.7A). Typical Doppler interrogation of the ductus will show bidirectional shunting with right-to-left flow in systole and reversal of flow into the PA branches in diastole. The amount of left-to-right diastolic flow is proportional to the pulmonary vascular resistance, with more flow seen with lower resistance. In normally related great arteries, the ductus is usually longer and narrower, as fetal flow patterns are predominantly from the aorta into the PA. If there is critical obstruction to PA flow from the RV, the ductus may be quite tortuous.

Short-axis suprasternal imaging demonstrates the branching pattern of brachiocephalic arteries and the sidedness of the aortic arch. The PA bifurcation is also seen from short-axis imaging, with branch sizes measured. The absence of an innominate vein should raise the possibility of a left SVC. A typical “crab” view should demonstrate normal pulmonary venous connections.

Tricuspid atresia vs. Double-inlet left ventricle In both tricuspid atresia and double-inlet left ventricle, the dominant ventricular chamber is the left ventricle. However, in double-inlet left ventricle both AV valves are committed to the dominant left ventricle, either through two valves of which one may be atretic, or through a common AV valve, and the ventriculoarterial connection is commonly discordant. In tricuspid atresia, only the morphologic left atrium is connected to the dominant left ventricle and ventriculoarterial connection is most frequently concordant.

Figure 12.6. Tricuspid atresia with transposed great arteries; apical views in same patient in Figure 12.4. A: Four-chamber view demonstrating the dilated left ventricle (LV), atretic tricuspid valve (arrow), and severely hypoplastic right ventricle (RV). There is a secundum atrial septal defect (asterisk). B: Slight anterior angulation of the transducer from the four-chamber view shows the aorta (Ao) arising from the hypoplastic RV and the dilated pulmonary artery (PA) from the LV. C: Color Doppler imaging demonstrates antegrade flow into the PA with a small amount flow into the restrictive ventricular septal defect (asterisk). LA, left atrium (Video 12.5).

HYPOPLASTIC LEFT HEART SYNDROME

Hypoplastic left heart syndrome (HLHS) is the fourth most common congenital cardiac anomaly of infancy, with a reported prevalence of 0.016% to 0.036% of live births, and occurs twice as often in boys as in girls.

Anatomy

HLHS encompasses a heterogeneous group of cardiac malformations characterized by normally related great arteries and varying degrees of underdevelopment of the left heart–aorta complex, resulting in obstruction to systemic cardiac output and the inability of the left heart to support the systemic circulation. The spectrum of anomalies includes mitral stenosis (Fig. 12.8A) or atresia, hypoplasia of the LV, aortic stenosis or atresia (Fig. 12.8B), and hypoplastic aortic arch. At the most severe end of the spectrum are mitral and aortic atresia, with a severely hypoplastic or “slit-like” LV. In milder forms, there is hypoplasia of the aortic and mitral valves and a varying degree of left ventricular hypoplasia. The ventricular septum is usually intact; a VSD, if present, is usually small. In rare cases of a large VSD with mitral atresia, the LV is usually well developed.

In HLHS, the systemic circulation is dependent on the RV and the ductus arteriosus. The aortic arch, ascending aorta, and coronary arteries are perfused by retrograde flow. Coarctation of the aorta is typically present.

Figure 12.7. Tricuspid atresia with transposed great arteries and restrictive ventricular septal defect; suprasternal views. A: Long-axis (sagittal) view in the same patient described in Figures 12.4 and 12.5 showing the hypoplastic transverse aortic arch (asterisk) and coarctation of the aorta (yellow arrow). B: Color Doppler imaging shows antegrade flow in the area of coarctation. C: Pulsed-wave Doppler interrogation of the coarctation in the presence of a large patent ductus arteriosus shows low-velocity flow. Doppler in this setting is unreliable in predicting the true severity of coarctation. Two-dimensional anatomic assessment is critical. Ao, aorta; IN, innominate vein; LA, left atrium; PDA, patent ductus arteriosus (Video 12.6).

Figure 12.8. Pathologic specimen from a patient with hypoplastic left heart syndrome (HLHS). A: Four-chamber view showing severely hypoplastic left ventricle (LV), hypoplastic mitral valve, and a small left atrium (LA). The right ventricle (RV) and right atrium (RA) are dilated. B: Long-axis outflow view demonstrates the atretic aortic valve (arrow) and hypoplastic aorta (Ao).

The presence of an intact or highly restrictive atrial septum has been recognized as a predictor of poor outcome among patients with HLHS. An intact atrial septum is present in approximately 6% of patients with HLHS; however, clinically deleterious restriction to flow at the level of the atrial septum can occur in as many as 22% of patients. During fetal life, a severely restrictive atrial septum may be associated with nonimmune fetal hydrops and pulmonary lymphangiectasia. In the presence of an intact atrial septum and mitral atresia, the only egress of blood from the LA may be a levoatriocardinal vein, a pulmonary-systemic connection that provides an alternative route for pulmonary venous blood to enter the systemic venous circulation. In the majority of patients, this vein connects the LA to the innominate vein. However, it may drain to other sites, including the left SVC or jugular venous system.

Clinical Presentation

The majority of fetuses with HLHS tolerate this cardiac anomaly well, with the majority of infants born at full-term, initially healthy in appearance. However, acute hemodynamic collapse follows closure of the ductus arteriosus (which may occur after discharge from the newborn nursery). If ductal patency is not restored promptly, poor systemic perfusion results in hypoxemia, acidosis, shock, and eventual death. On examination, the infant appears poorly perfused, tachypneic, and pale, with diffusely diminished pulses. There may be only a nonspecific cardiac murmur, but an S3 gallop is very common. The second heart sound is loud and single. There is often hepatomegaly. Echocardiographic identification of HLHS should prompt immediate intervention with infusion of prostaglandin E1 to maintain or improve ductal patency.

Infants with HLHS and a nearly intact atrial septum present with severe pulmonary venous hypertension and are even more critically ill with severe respiratory distress. These patients often present with cardiogenic shock and profound cyanosis at birth, needing immediate catheter-based septostomy/cutting balloon dilation of the atrial septum for survival to a palliative surgical procedure.

Echocardiography in Hypoplastic Left Heart Syndrome

The overall approach to imaging in HLHS is to provide complete diagnostic and hemodynamic information. Cardiac catheterization is reserved only for the patient requiring emergent intervention (usually for enlargement of the ASD). An assessment of right ventricular and tricuspid valve function, ductal physiology, and atrial septal anatomy is crucial for clinical management.

Systemic and pulmonary flow ratios are dependent on the difference in resistance between the two respective vascular beds. A large, nonrestrictive interatrial communication in the setting of low pulmonary resistance promotes preferential flow into the pulmonary vascular bed at the expense of the systemic circulation. Pulmonary overcirculation and imbalance in the pulmonary/systemic vascular resistance ratio contribute to hemodynamic instability in infants with HLHS. Conversely, a restrictive ASD in the presence of severely elevated PA pressure and resistance produces preferential right-to-left ductal shunting and restricted pulmonary blood flow at the expense of the patient’s oxygenation. Intervention to relieve severe obstruction may be needed before definitive surgical palliation. Thus, in patients with HLHS, the clinical presentation can be variable. Immediate echocardiographic assessment of the underlying physiology is critical for management of the patient before palliative surgery is planned and undertaken.

Subcostal Four-Chamber (Coronal) View

The subcostal four-chamber view typically demonstrates a dilated RA and RV. When angling the transducer posteriorly and imaging toward the base of the LA, the LV either appears very small or is not visualized (Fig. 12.9A [Video 12.7]). It should be immediately apparent when the LV is diminutive or “slit-like” that a significant discrepancy in the size of the RV compared with the LV is present. Once this view is obtained, the echocardiographer should evaluate the mitral valve and the great arteries very carefully. Anterior angulation of the transducer typically shows the dilated RVOT and main PA (MPA), but the very tiny aorta may be difficult to visualize in coronal plane imaging. A large patent ductus arteriosus (PDA) may be seen, essentially representing a continuation of the MPA as the ductal arch, but this is better visualized in subcostal short-axis views. In the setting of cardiovascular collapse, right ventricular function may also be reduced, sometimes significantly so. Tricuspid regurgitation is usually present in this clinical setting.

The atrial septum should be carefully evaluated from the subcostal windows. The size, number, and location of communications from LA to RA should be assessed (Fig. 12.9AB). Bulging of the atrial septum from the LA into the RA is suggestive of restriction to egress from the LA. Also, in the presence of a restrictive or intact atrial septum, the atrial septum is usually thick and the pulmonary veins are dilated (if normally connected). Color Doppler aids in mapping of the defects with the shunt typically occurring from left to right (see Fig. 12.9B). Alignment of the Doppler cursor parallel with the defect allows estimation of the mean transeptal gradient by tracing the Doppler signal across three cardiac cycles.

Bidirectional shunting is very unusual but may be seen in the presence of severe tricuspid regurgitation or anomalous venous connections. The echocardiographer should be alert to the possibility of anomalous connection and drainage of the pulmonary veins. While present in a minority of patients with HLHS, this should be suspected particularly if venous return into the diminutive LA cannot be seen from subcostal imaging.

Subcostal Short-Axis (Sagittal) Views

Orthogonal plane imaging provides confirmation of the cardiac anatomy. Subcostal short-axis views are excellent for interrogation of the atrial septum. The presence/location of atrial communications should be determined and color Doppler mapping of atrial shunting should be performed. The relative size of the very hypoplastic aorta posteriorly and dilated PA anteriorly is evaluated. Again, by angling the transducer rightward, the continuation of the dilated MPA as the ductal arch is easily demonstrated. Color Doppler interrogation may show bidirectional PDA shunting (typically right-to-left in systole with left-to-right shunting in diastole depending on pulmonary resistance characteristics). The entire aortic arch may be visualized in this view (with definitive imaging obtained from suprasternal imaging). Scanning toward the midventricular level shows the enlarged anterior RV and hypoplastic, posterior LV (Fig. 12.9C). Right ventricular function and tricuspid regurgitation should be assessed.

Figure 12.9. Hypoplastic left heart syndrome (HLHS); subcostal views. A: Long-axis (coronal) image showing very dilated right atrium (RA) and small left atrium. The secundum atrial septal defect (asterisk) is large and unrestrictive. The right ventricle (RV) is hypertrophied, and the left ventricle (LV) and mitral valve are severely hypoplastic (Video 12.7). B: Color Doppler imaging demonstrating nonrestrictive laminar flow across the atrial septal defect (asterisk). C: Short-axis (sagittal) view in the same patient, angled toward the midventricular level showing the anterior, hypertrophied RV. Note the echo-bright LV endocardium often seen in HLHS.

Parasternal Views

Parasternal long-axis view Parasternal long-axis views confirm the size discrepancy between the large RV anteriorly and the diminutive or small LV posteriorly (Fig. 12.10A). Careful examination for the slit-like, muscle-bound LV confirms that the anterior ventricle is the RV. The ventricular septum is most often intact. Right ventricular systolic function can be evaluated from the long-axis view, although angling the transducer inferiorly toward the tricuspid inflow is usually required. Left ventricular systolic function is usually severely decreased if a cavity is present. In this instance, the left ventricular endocardium and papillary muscles may be echo-bright, suggesting the presence of endocardial fibroelastosis secondary to long-term subendocardial ischemia. Mitral and aortic valve leaflets should be examined for mobility or patency. The mitral annulus is characteristically hypoplastic with the mitral valve and its subvalvular apparatus appearing abnormal. If patent, the valve may be thickened and doming, with shortened chordae. A supravalvar mitral ring may also be present. The aortic valve is usually completely atretic but may be thickened and doming. Subaortic obstruction may be present. The size of the hypoplastic aortic annulus and ascending aorta (usually an internal diameter of less than 5 mm) is more easily measured in the parasternal long-axis view (see Fig. 12.10A).

The transducer is angled anteriorly and superiorly to evaluate the RVOT, the dilated MPA, and the ductal arch. Typically, the ductus is very large. With Doppler interrogation, the PDA shunt is right-to-left during systole, while the amount of left-to-right shunt during diastole is dependent on the pulmonary vascular resistance. Moving the transducer to a high left parasternal window may bring the large ductus/ductal arch into view more easily. Pulsed-wave Doppler is used to evaluate a ductal gradient in the setting of early ductal constriction as typically indicated by an increased systolic Doppler flow velocity through the PDA (> 2.5 m/s).

From parasternal long-axis imaging, the LA is usually small. However, the LA can be dilated in the presence of a nearly intact atrial septum.

Parasternal short-axis view In the parasternal short-axis view, there is a large anterior RV and small posterior LV (Fig. 12.10B). This view is also useful in the assessment of ventricular function, mitral valve size and morphology, and mitral papillary apparatus number and position. The mitral valve may be “parachute-like” in nature with a single papillary muscle group. Short-axis scans at the base of the heart allow assessment of the ascending aortic size in cross section and further evaluation of aortic valve morphology. The great arteries are normally related with the severely hypoplastic aorta in the center. The coronary artery origins are most often normal and may appear as extensions of the diminutive aorta (Fig. 12.10C). The MPA is usually much dilated and the PDA is prominent (see Fig. 12.10C). The branch PAs should be assessed in this view, with slightly higher positioning of the probe on the patient’s chest to obtain the trifurcation view (see Fig. 12.10C). Again, with color Doppler and pulsed-wave Doppler examination, the PDA flow is most typically bidirectional. A systolic gradient should be assessed for early ductal constriction (particularly if the prostaglandin infusion has not been initiated).

Apical Views

An apical four-chamber view provides comparison of the relative sizes of the ventricles. The RV is typically dilated and hypertrophied. The LV is small, muscle bound, and non-apex forming (Fig. 12.11A[Video 12.9]). The mitral valve annulus is usually hypoplastic with either an atretic opening or severely stenotic leaflets. If flow is present, one should assess the degree of stenosis from this view (taking into account that a larger interatrial communication may reduce the measured gradient). Furthermore, the mitral leaflet excursion may be limited in the presence of critical aortic stenosis or atresia, secondary to severely elevated left ventricular end-diastolic pressure. The transmitral gradient may also be artificially reduced in this setting. Spectral and color Doppler flow may be used to evaluate mitral inflow, mitral regurgitation, and aortic outflow (if the valve is patent). Tricuspid valve function should be assessed carefully; significant tricuspid regurgitation is a poor prognostic indicator (Fig. 12.11BC). Anterior angulation of the probe to a para-apical view will show the dilated MPA, and color Doppler assessment of pulmonary valve regurgitation should be performed.

Suprasternal Views

Suprasternal long-axis scans provide an excellent view of the ascending aorta, aortic arch, and upper descending aorta. The ascending aortic size may range from mild to severely hypoplastic (Fig. 12.12[Video 12.10]); however, the caliber of the aorta is much larger at the level of the innominate artery and beyond. Coarctation of the aorta is usually present (Fig. 12.13A). In the presence of a severe coarctation, there is a juxtaductal posterior ledge and increased distance between left common carotid and subclavian artery. The presence of coarctation may be difficult to assess due to a severely dilated ductus arteriosus. An anterior ledge is common where the dilated ductus enters the descending aorta. Using color Doppler, the flow in the transverse aortic arch and ascending aorta is retrograde in the presence of critical aortic stenosis or atresia. A transient forward flow in the aortic arch in systole may be secondary to movement of the atretic aortic valve during systole (Fig. 12.13BC [Video 12.11]). Confirmation of ductal shunt physiology is also performed from this view. Anomalous pulmonary venous drainage to a vertical vein or a levoatriocardinal vein draining the pulmonary venous system needs to be assessed from comprehensive suprasternal imaging. Color flow in the venous system toward the transducer in the suprasternal notch should prompt a thorough evaluation of pulmonary venous connections.

Figure 12.10. Hypoplastic left heart syndrome; parasternal views. A: Long-axis view showing a severely hypoplastic left ventricle (LV), severe mitral valve stenosis, and aortic atresia. The right ventricle (RV) is severely dilated. The ascending aorta (Ao) is diminutive, serving primarily as a conduit for retrograde coronary perfusion. B: Short-axis view at the cardiac base demonstrating the diminutive ascending Ao (arrow) and dilated pulmonary artery (PA) with trifurcation of branches into the right (R) and left (L) branch pulmonary arteries and large ductus arteriosus (D). The ductal arch continues into the descending aorta (DA). C: Short-axis view at midventricular level showing the enlarged, hypertrophied RV with severely hypoplastic LV. LA, left atrium; RA, right atrium (Video 12.8).

Role of 3-Dimensional Echocardiography in Hypoplastic Left Heart Syndrome

Additional assessment of right ventricular volume and function may be performed with 3D echocardiography. Right ventricular volume and function assessment by 3D imaging appears to be highly reproducible. When compared with cardiac magnetic resonance imaging, 3D echo systematically underestimates end-diastolic and end- systolic volumes. 3D echo is increasingly being recognized as the imaging modality of choice for evaluation of tricuspid valve morphology and the mechanism of tricuspid valve regurgitation. Significant tricuspid regurgitation in HLHS is commonly associated with either leaflet tethering or prolapse; however, one must be sure that coarctation of the aorta is not contributing as well. Tethering of tricuspid valve leaflets is associated with lateral displacement of the papillary muscles. However, in case of tricuspid valve prolapse, the annular height is greater, the septal leaflet size is smaller, and there is no papillary muscle displacement. 3D echo is also more accurate than 2D echo in evaluation of the tricuspid regurgitation vena contracta.

Figure 12.11. Hypoplastic left heart syndrome; apical views. A: Four-chamber view demonstrating enlargement of the right ventricle (RV) and right atrium (RA). The left atrium (LA) is small and there is severe hypoplasia of the mitral valve and left ventricle (LV). [Video 12.9] B: Four-chamber view, systolic frame, in another patient with severely hypoplastic LV (yellow asterisk) showing a large coaptation defect in the tricuspid valve (arrow). C: Color Doppler view in the same patient demonstrates severe tricuspid valve regurgitation.

Figure 12.12. Hypoplastic left heart syndrome; suprasternal view. Long-axis view showing the severely hypoplastic ascending aorta (Ao). IN, innominate vein (Video 12.10).

Figure 12.13. Hypoplastic left heart syndrome; high left parasternal view. A: Short-axis view demonstrating “end-to-side” connection of the hypoplastic aortic arch (arrow) to the ductal arch and a dilated patent ductus arteriosus supplying the descending aorta (asterisk). B:Characteristic color Doppler imaging of the aortic and ductal arches demonstrates right-to-left shunting (blue flow away from the transducer) in the ductus arteriosus with retrograde flow in the aortic arch (red flow toward the transducer) (Video 12.11). C: Pulsed-wave Doppler interrogation demonstrates retrograde flow in the transverse aortic arch. PA, main pulmonary artery.

Borderline Left Ventricle

One of the key questions in the management of patients with mitral and aortic stenosis is determining the ability of the hypoplastic LV to sustain the systemic circulation. Investigators have suggested numerous echocardiographic parameters that might be used to predict outcome following attempted biventricular or univentricular repair. However, it is important to recognize that these factors are lesion-specific and may not always be generalized. That is, the criteria used for univentricular versus biventricular repair in aortic stenosis may not be generalized or applied to mitral stenosis in the setting of a hypoplastic LV.

In aortic stenosis, based on an extensive retrospective analysis, Rhodes and colleagues showed the following echocardiographic parameters correlated with increased risk for hospital death: (1) left ventricular long-axis–to–heart long-axis ratio less than 0.8, (2) indexed aortic root diameter less than 3.5 cm/m2, (3) indexed mitral valve area less than 4.75 cm2/m2, and (4) left ventricular mass index less than 35 g/m2. The authors of this study proposed a scoring system called the “score of Rhodes.” Data for the Rhodes score were based on retrospective data from a small group (65 patients) with critical aortic stenosis who were preselected for biventricular repair. The scoring system was based on the following equation:

14.0 (BSA) + 0.943 (iROOT) + 4.78 (LAR) + 0.157 (iMVA) – 12.03

where BSA is body surface area, iROOT is indexed aortic root dimension, LAR is the ratio of the long-axis dimension of the LV to the long-axis dimension of the heart, and iMVA is the indexed mitral valve area. A score of less than 0.35 was predictive of mortality after biventricular repair. Subsequent reports have shown poor predictive capability of the Rhodes score, especially in lesions other than aortic stenosis.

Additional authors have proposed that other factors lead to an increased mortality following biventricular repair in HLHS (Table 12.2). The Congenital Heart Surgeon’s Society of North America has also proposed a “Critical Aortic Stenosis Calculator” that uses demographic and echocardiographic parameters. This equation is designed to predict the optimal surgical strategy (biventricular versus univentricular approach) in patients with aortic stenosis. Ongoing discussion of these different morphologic, demographic, and echocardiographic parameters by numerous investigators is an indication that there are inherent flaws in any rigid assessment system. Ongoing review of surgical results and assessment of echo parameters may continue to provide further information in the future. In conclusion, for patients with multiple left heart obstructive lesions and a borderline LV, there are no clear-cut guidelines. It is important to remember that univentricular palliation following attempted biventricular repair (crossover) is associated with higher mortality. Furthermore, a complicated biventricular repair with significant residual lesions may be worse than a successful univentricular palliation. None of these scores take into account the long-term functional and quality of life outcomes. Risk factors will keep changing and evolving with newer surgical techniques. Some centers are using a staged LV recruitment strategy that involves resection of noncompliant endocardial fibroelastosis, aortic and mitral valvuloplasty, and atrial level restriction for biventricular rehabilitation of mildly hypoplastic borderline left ventricles. Long-term outcome of this staged LV recruitment strategy and its effect on pulmonary vascular resistance and LV diastolic function remains unknown. A combination of the above-mentioned parameters and clinical/surgical experience will likely dictate the preference of an individual institution.

DOUBLE-INLET LEFT VENTRICLE

Double-inlet left ventricle (DILV), first described by Holmes in 1824 and named by De La Cruz and Miller in 1968, comprises 1% of all congenital heart malformations. DILV exists when the greater part of both AV junctions is supported by the same ventricular chamber. If mitral and tricuspid atresia are excluded, DILV is the most common form of univentricular AV connection. This malformation likely originates embryologically from a partial or complete block in the left-to-right expansion process of the AV canal, resulting in connection of both atria to the primitive ventricle, which then forms the LV and a hypoplastic RV. In DILV, the hypoplastic RV lacks the inlet portion and has either a bipartite (trabecular and outlet) or monopartite (trabecular) morphology. Typically, both left and right AV valves have mitral valve morphology with deeper anterior leaflets and shallower posterior leaflets. Both AV valves lie posteriorly in fibrous continuity with a semilunar valve.

Anatomy of Double-Inlet Left Ventricle

Typically, the AV connections are committed to the dominant posterior LV (Fig. 12.14). The inlet septum is absent and both AV valves are in close proximity to each other, posterior to the trabecular septum. Less commonly seen is a hypoplastic, or atretic, AV valve. An ASD must be present in this situation to provide communication from one atrium to the other.

Figure 12.14. Pathologic specimen from a patient with double-inlet left ventricle. Long-axis inflow view showing both right atrium (RA) and left atrium (LA) emptying in to left ventricle (LV).

Double-Inlet Left Ventricle with Transposed Great Arteries (Hypoplastic Subaortic Right Ventricle)

When there is a dominant LV and a hypoplastic RV, the ventriculoarterial connections are usually discordant. In this form of DILV, the aorta arises from the rudimentary RV or outlet chamber. This chamber is connected with the LV through a VSD, which is the embryologic remnant of the bulboventricular foramen. This is seen in approximately 85% of DILV cases. The aorta is usually leftward and anterior in position, with l-looping of the right ventricular outlet chamber. Alternatively, with d-looping of the right ventricular chamber, the aorta is anterior and rightward to the PA. There may be obstruction of the bulboventricular foramen and it may be associated with coarctation of aorta.

Double-Inlet Left Ventricle with Normally Related Great Arteries

Concordant ventriculoarterial connection, or normally related great arteries, is less common (15%) in DILV. This arrangement is called the “Holmes heart.” The bulboventricular foramen is frequently quite stenotic and results in subpulmonary stenosis.

Clinical Presentation

Infants with DILV typically present within the first few weeks of life. For those with restricted pulmonary blood flow, as the ductus arteriosus constricts, the presenting symptom will be cyanosis. Those with severe aortic obstruction (restrictive bulboventricular foramen or aortic arch) will typically present with poor peripheral perfusion and signs of low cardiac output as the ductus constricts. On clinical examination, the infant with restricted pulmonary blood flow will have cyanosis and a harsh systolic ejection murmur over the precordium; not unlike the infant with tetralogy of Fallot. Those infants with restricted systemic output will appear tachypneic and pale and have poor pulses throughout. The cardiac examination demonstrates precordial overactivity, a single second heart sound, a gallop, and a pulmonary flow murmur. Institution of prostaglandin E1 therapy is life saving after the diagnosis of DILV with ductal-dependent physiology (either systemic or pulmonary circulation) is confirmed by echocardiography.

Patients with unobstructed pulmonary blood flow and no significant subaortic obstruction may present a few weeks later with signs of congestive heart failure and pulmonary overcirculation as pulmonary vascular resistance falls. Infants with pulmonary overcirculation will have significant tachypnea and very mild desaturation (which may be evident only on pulse oximetry). In this setting, the clinical examination is much like that for the patient with a large VSD.

Echocardiographic Evaluation of Double-Inlet Left Ventricle

Echocardiography plays a critical role in the early diagnosis and management of univentricular AV connection. Once again, the key to evaluation of complex univentricular anatomy and physiology is to use the segmental anatomic approach. As an initial approach to diagnosis, the apical and subcostal four-chamber scan planes provide excellent views of the two closely placed AV valves without an intervening ventricular septum, providing the echocardiographer with the initial impression of a univentricular AV connection. Further imaging to evaluate the cardiac anatomy in detail should be conducted in a segmental approach as outlined later.

Subcostal Views

Subcostal four-chamber (coronal) view Abdominal and atrial situs should be determined in this view. In DILV, atrial situs is predominantly solitus, followed by right or left isomerism. The four-chamber view reveals the dominant left ventricle with both AV valves entering this chamber; one must angle the transducer anteriorly to see the rudimentary outlet chamber and great arteries. The number, size, and location of defects in the atrial septum should be assessed. Assessment of the atrial septum is particularly important in the setting of a restrictive or atretic AV valve. The origin and orientation of the two great arteries should be assessed. Ventriculoarterial connections are usually discordant with the aorta anterior and to the left of the PA, so that echocardiographic similarities to transposition exist. Both great arteries are parallel in their course, with the posterior PA bifurcating. The size of the bulboventricular foramen as well as the communication between the LV and the outlet chamber should be evaluated in orthogonal views to rule out potential restriction. In the presence of a restrictive bulboventricular foramen, color Doppler flow appears aliased with increased velocity seen on spectral Doppler interrogation.

Subcostal short-axis (sagittal) view The subcostal short-axis view is useful for evaluation of atrial septal anatomy, visualization of the posterior LV receiving two AV valves, examination of the bulboventricular foramen, and confirmation of the arrangement of the great arteries. The two AV valves appear as two circles in the short-axis view; the leaflets touch each other when open in diastole if there is no stenosis. There is an anterior trabecular chamber that is not connected to the atrium. The communication of this anterior chamber with the LV is via the bulboventricular foramen, which is examined in this orthogonal plane to determine its size. In the presence of transposed great arteries, as is most common, the arteries have a parallel course at the base of the heart, with the posterior PA bifurcating. If the great arteries are normally related, the bulboventricular foramen is usually quite restrictive.

Parasternal Views

Parasternal long-axis view Parasternal long-axis imaging in DILV will demonstrate the posterior LV. With rightward/leftward angling of the transducer, it is seen that both AV valves enter this posterior left ventricular chamber. One must be careful not to confuse this anatomy with a VSD and enlarged LV, as typically only one AV connection is seen at a time (rotation to parasternal short-axis makes this apparent) (Fig. 12.15A [Video 12.12A]). In DILV, one great artery will typically originate from the main ventricular chamber and the other great artery is seen more anteriorly, arising from the rudimentary outlet chamber. The bulboventricular foramen should be evaluated for anatomic size and evidence of restriction, again from multiple imaging planes with 2D, spectral, and color Doppler interrogation.

Parasternal short-axis view Imaging from the parasternal short axis view shows both AV valves posterior to the trabecular septum (Fig. 12.15B [Video 12.12B]), which is oriented in a horizontal plane. In DILV, the hypoplastic right ventricular outlet chamber is usually positioned anterosuperior and leftward to the morphologic LV. However, it can occasionally be rightward; one must angle the transducer toward the base of the heart to visualize this relationship. A Doppler gradient is obtained in a parallel plane to the flow directed anteriorly through the bulboventricular foramen. Typically, the mean gradient will reflect the amount of obstruction more closely than the peak instantaneous gradient, as the obstruction is not typically dynamic.

Angling further toward the base of the heart should bring the great arteries into view, seen as two circles in the short-axis view when transposed, due to their parallel course. The relative leftward/rightward position of the anterior aorta in relation to the PA should be noted. With normally related great arteries, the relationship of the great arteries is similar to that seen in a normal heart, with the aorta seen in cross section and the PA in a more longitudinal plane. The PA confluence should be evaluated. Imaging from a higher left parasternal plane may bring the PA “trifurcation” into view in the patient with normally related great arteries, also showing the PDA.

Apical Four-Chamber View The apical four-chamber scan plane provides the best view of the crux of the heart. In DILV, the dominant LV has fine apical trabeculations, two main papillary muscle groups, a smooth “septal” surface with no chordal attachments; it receives two AV valves. These two separate AV valves guard the AV junction; both typically have mitral morphology and are in continuity with the posterior great artery (Fig. 12.16AB [Video 12.13]). The function of both AV valves, including whether there is stenosis or atresia, should be assessed in this view. Ventricular systolic function and AV valve regurgitation can also be evaluated. The presence of left AV valve stenosis may require atrial septostomy or septectomy to relieve left atrial obstruction.

Angling anteriorly, the origin, relationship, and size of the great arteries can be evaluated. When the great arteries are transposed, the PA typically originates from the main left ventricular cavity with the anterior (usually leftward) aorta arising from the rudimentary outlet right ventricular chamber. One should also assess the size of the bulboventricular foramen from this plane, using spectral and color flow Doppler.

Figure 12.15. Double-inlet left ventricle with normally related great arteries; parasternal views. A: Long-axis view showing the anterior hypoplastic right ventricle (RV), enlarged left ventricle (LV), and a muscular ventricular septal defect (asterisk). The LV gives rise to the aorta (Ao) (Video 12.12A). B: Short-axis view at the level of atrioventricular valves showing classic appearance of both the right (R) and left (L) atrioventricular valves committed to the LV posterior to the large ventricular septal defect (asterisk). LA, left atrium; PA, pulmonary artery (Video 12.12B).

Figure 12.16. Double-inlet left ventricle with normally related great arteries; apical views. A: Diastolic frame, showing both left atrium (LA) and right atrium (RA) emptying into the left ventricle (LV) through the left and right atrioventricular valves. B: Systolic frame in the same patient (Video 12.13).

Suprasternal Views

The suprasternal long-axis view demonstrates the aortic arch anatomy and the presence/absence of coarctation. If there is significant bulboventricular foramen obstruction, one should suspect arch obstruction—either coarctation or interruption of the aorta. In the neonate, a ductus arteriosus may be present, and if the arch is critically obstructed, patency is needed. The PA confluence and bilateral branch sizes can be evaluated in the short-axis imaging plane, as can pulmonary venous connections (“crab” view.)

Interventricular Communication in Double-Inlet Left Ventricle or Tricuspid Atresia with Ventriculoarterial Discordance

Many different terms have been used to define the connection between the dominant and rudimentary ventricle in univentricular AV connections, including “VSD,” “bulboventricular foramen,” and “the outlet foramen.” We prefer to use the term “bulboventricular foramen.” The bulboventricular foramen is a common site of outflow tract (subvalvular) obstruction. This communication is not circular but tends to be more elliptical. As a result, the area of the bulboventricular foramen should be measured in two orthogonal planes (long- and short-axis) by 2D echocardiography. The area is calculated as follows:

Area = [diameter (1) × diameter (2)] × π/4

and is then indexed to body surface area.

An individual with a bulboventricular foramen area less than 2 cm2/m2 is at higher risk for developing late obstruction. In addition, the Doppler gradient should be interrogated from multiple views to obtain the best alignment of the ultrasound beam to the angle of flow acceleration. One should remember that the gradient may be inaccurate in the presence of a large PDA or with a suboptimal Doppler angle of interrogation.

In addition, it is critical to assess the bulboventricular foramen size and rule out potential obstruction before the Fontan operation is carried out. Obstruction at the bulboventricular foramen may complicate the course of patients with a functional single ventricle, resulting in pressure overload, which leads to ventricular hypertrophy, fibrosis, and dysfunction (both systolic and diastolic). Such obstruction should be addressed at the time of surgery.

It is controversial whether PA banding accelerates the process of bulboventricular foramen obstruction or it is a de novo event. In a study of 28 neonates, all patients with an initial bulboventricular foramen area index of less than 2 cm2/m2, who did not undergo early bulboventricular foramen bypass, developed late obstruction. The rate of development of bulboventricular stenosis did not differ in patients with and without PA banding, but smaller size of the bulboventricular foramen correlated with the presence of aortic arch obstruction.

In the future, routine use of 3D echocardiography may provide a more accurate assessment of the area of the bulboventricular foramen in DILV, identifying patients with subaortic stenosis caused by a restrictive defect, or potentially identifying those at risk for future obstruction.

APPROACH TO THE PATIENT WITH UNIVENTRICULAR ATRIOVENTRICULAR CONNECTION: SURGICAL PLANNING

In all patients with univentricular AV connection (excluding those who had a 1.5- or even 2-ventricle repair), the final common pathway for surgical palliation is that of the modified Fontan procedure, wherein systemic venous return flows passively into the pulmonary circulation. The critical factor in surgical planning for all infants with univentricular physiology is to perform palliation in a timely fashion and in a way that will reduce the risk for later successful completion of the modified Fontan procedure. Thus, looking forward, one must keep in mind that the best candidates for the Fontan procedure will have the following: (a) preserved ventricular function without significant AV valve regurgitation, (b) low PA pressure and resistance, (c) normal pulmonary branch architecture, (d) absence of obstruction to the systemic circulation, and (e) an unrestrictive ASD. In the initial evaluation of the patient with single-ventricle physiology, the plan for initial palliation and eventual surgical approach should be directed toward optimization of all of these factors.

The Neonate with Excessive Pulmonary Blood Flow

For those patients with tricuspid atresia or DILV, initial management is guided by the presenting physiology and amount of pulmonary blood flow. In a patient with tricuspid atresia with normally related great arteries, the degree of restriction of the VSD and pulmonary outflow tract will dictate the initial approach. Infants with unrestrictive pulmonary blood flow will typically require a palliative PA band procedure between 4 and 8 weeks of age to protect the pulmonary bed from exposure to systemic pressure, which, if not addressed, will lead to irreversible pulmonary hypertension and vascular disease. The band serves two purposes: to decrease the downstream PA pressure in preparation for second- and third-stage surgery and to restrict the pulmonary blood flow.

The timing of the PA banding procedure will depend on the infant’s clinical course, as placement of a band is usually delayed until the pulmonary resistance declines (as manifested by increased left-to-right shunting) so that the surgeon may judge the adequacy of the band more easily. Echocardiographic follow-up during this time in the patient with tricuspid atresia/normally related great arteries may reveal signs of pulmonary overcirculation with increased flow in the PA, dilation of the LA and LV, and low-velocity VSD/RVOT Doppler signals indicative of persistent PA hypertension.

Echocardiographic Evaluation of Pulmonary Artery Band

The echocardiogram following PA banding should evaluate both the position of the band and the gradient across the band (Fig. 12.17AB). Confirmation of band position, branch PA anatomy, and Doppler gradient by echocardiography is warranted before hospital dismissal, so that comparison is possible during serial echocardiographic examinations. Over time, a band may migrate distally and cause distortion of the branch PAs (typically the right PA) (Fig. 12.17CD [Video 12.14A]). A PA band may also distort the pulmonary valve, resulting in varying degrees of pulmonary valve regurgitation.

The gradient across the PA band will help in estimation of distal PA pressure (see Fig. 12.17B). Peak instantaneous and mean gradients should be recorded for serial examinations. Optimal Doppler alignment with the band positioned in the mid-MPA can be achieved from parasternal short-axis or subcostal views. Over time, the band gradient should increase, as the band is “outgrown.” A progressive decrease in the trans-PA band gradient should raise the possibility of increasing distal PA pressure. Elevation in distal pressure may be secondary to a loose band and resultant inadequate protection of distal PA bed, resulting in pulmonary vascular obstructive disease; or it may be due to elevation of distal pressure (perhaps in a situation where the band was placed relatively late).

In a patient with transposition of the great arteries or subaortic stenosis, PA banding may result in accelerated narrowing of the VSD or progression of the subaortic stenosis, resulting in obstruction to both great arteries. In this situation, echocardiography plays a critical role in following patients for the development of subaortic stenosis, which produces ventricular hypertrophy and potential ventricular dysfunction, all of which complicate future palliation.

The Neonate with Restricted Pulmonary Blood Flow

Infants with tricuspid atresia/normally related great arteries and a restrictive VSD or pulmonary stenosis, or the infant with DILV and normally related great arteries, will usually have cyanosis at presentation. As the VSD becomes more restrictive, the echocardiogram will show the reduced flow through the VSD or pulmonary outflow tract with increased Doppler gradient if proper alignment can be achieved. In this setting, a modified Blalock-Taussig (BT) shunt is the most commonly performed systemic-to-PA shunt for initial palliation to provide a stable source of pulmonary blood flow. The modified BT shunt is generally a 3- to 4-mm nonvalved polytetrafluoroethylene conduit connecting the subclavian or innominate artery and the right branch PA (Fig. 12.18A [Video 12.15]). Postoperative echocardiographic assessment of a BT shunt should include the evaluation of shunt patency and Doppler flow pattern. The BT shunt is best visualized from the suprasternal notch in a short-axis view. Additional off-axis views may be needed depending on the course and length of the shunt. Color Doppler imaging will facilitate mapping of the shunt course and its entry into the PA (see Fig. 12.18A). It is important to recognize that a continuous-wave Doppler gradient across the BT shunt and other shunts made of prosthetic material will not be accurate, as the long tubular nature of the shunt interferes with accurate determination of its pressure drop (Fig. 12.18B). However, an increasing gradient on serial exams may help identify shunt stenosis. The echocardiographer should evaluate the size and relative Doppler flow patterns in each PA (right and left) to rule out important branch stenosis.

Figure 12.17. Pulmonary artery band (PAB). A: Modified para-apical view with the transducer angled anteriorly to image the pulmonary artery. Color Doppler imaging with aliased flow through the PAB (arrow). B: Continuous-wave Doppler interrogation of the PAB demonstrating high-velocity systolic flow with a maximum instantaneous gradient of 127 mm Hg and a mean gradient of 76 mm Hg. C: High left parasternal short-axis image in different patient with PAB; Color Doppler interrogation of the branch pulmonary arteries demonstrates potential distal migration of the band with early impingement of flow (arrow) into the right pulmonary artery (RPA). Note the normal flow in the left pulmonary artery (LPA) (Video 12.14A). D: On subsequent follow-up in the patient in C, further compression of the proximal RPA (arrow) results in almost complete occlusion with little flow demonstrated (Video 12.14B).

Figure 12.18. Right modified Blalock-Taussig (BT) shunt. A: Suprasternal short-axis imaging with color Doppler mapping to aid in visualization of shunt (Video 12.15). B: Continuous-wave Doppler in the shunt demonstrates high-velocity continuous flow throughout the cardiac cycle. Ao, aorta; LPA, left pulmonary artery; RPA, right pulmonary artery.

“The Balanced Infant”

The infant with DILV and pulmonary stenosis, or tricuspid atresia and pulmonary stenosis, will have a balanced circulation and a protected pulmonary bed (no exposure to increased pressure), adequate oxygen saturation, and no significant clinical signs or symptoms of heart failure or excessive cyanosis. In this situation, very early neonatal palliation may not be necessary and the initial palliative procedure may be delayed until the time of the bidirectional cavopulmonary anastomosis (usually between 3 and 6 months of age).

The Neonate with Restricted Systemic Blood Flow

In neonates with HLHS or severe left-sided obstruction with a small LV, a modified Norwood operation is the first-stage surgical procedure. The modified Norwood approach, first introduced for patients with HLHS, has been applied to a heterogeneous group of cardiac defects characterized by the presence of a functional single ventricle with systemic outflow tract obstruction, including patients with tricuspid atresia and transposed great arteries with restrictive VSD and arch obstruction. In the neonate with DILV and aortic arch obstruction, the initial approach likely includes modifications of the Norwood or Damus-Kaye-Stansel operation.

Modified Norwood Procedure

The modified Norwood procedure is designed (1) to provide unobstructed systemic output, including relief of aortic arch obstruction, (2) to maintain the functional single ventricle as the systemic ventricle, and (3) to provide a stable source of pulmonary blood supply. The Norwood procedure consists of surgical reconstruction and augmentation of the ascending aorta and aortic arch, an atrial septectomy, and a systemic-to-pulmonary shunt. Important aspects of the initial procedure include successful relief of arch obstruction and creation of an unrestrictive ASD. The two means of providing pulmonary blood flow in these patients are either a modified BT shunt or an RV-to-PA conduit (also known as a Sano shunt). The latter has the potential advantage of a stable immediate postoperative hemodynamic status by preventing diastolic runoff. However, many experienced centers have shown no significant survival advantage of the Sano shunt over a traditional BT shunt. Moreover, the long-term effects of a ventriculotomy-related scar on right ventricular function and arrhythmia potential remains to be seen. The operative risk factors for the Stage 1 Norwood procedure include low birth weight, prematurity, associated chromosomal and noncardiac congenital anomalies, pulmonary venous obstruction, tricuspid valve regurgitation, smaller caliber of ascending aorta, and increased circulatory arrest time.

The Hybrid Procedure

Stage I palliation of HLHS can be performed as a hybrid procedure in high-risk patients with multiple comorbidities as a bridge to transplant or as a bridge to a Norwood operation and thereby avoid neonatal cardiopulmonary bypass in a neurologically vulnerable period. At some centers, the hybrid procedure is used as a primary stage I management strategy in all infants with HLHS or in patients with a borderline LV as a bridge to a two-ventricle repair. A hybrid approach for stage I palliation combines surgical and interventional catheterization procedures. During the hybrid procedure, bilateral pulmonary artery banding is performed surgically while catheterization is used for stenting of the ductus arteriosus and performing a balloon atrial septostomy.

Echocardiographic Evaluation Following Stage 1 Norwood Procedure

Apart from the usual postoperative echocardiographic evaluation, patients undergoing a Norwood procedure should be carefully evaluated for restriction of the ASD, residual or recurrent aortic arch obstruction, and PA branch stenosis or distortion. Evaluation of the BT shunt is as discussed earlier. The atrial septal gradient will depend on the size of systemic-to-PA shunt/conduit and amount of pulmonary blood flow. If restriction is present, color Doppler will show aliased flow and an elevated mean gradient from LA to RA (Fig. 12.19AC [Video 12.16A, B]). Worsening cyanosis early after a Norwood procedure may be secondary to a restrictive atrial septum which is best imaged in the subcostal sagittal or coronal view.

Echocardiography plays a key role in the evaluation of the reconstructed aortic arch following Stage 1 Norwood palliation (Fig. 12.20AB). The systemic RV in HLHS patients does not tolerate aortic arch obstruction. Accordingly, one of the earliest clues that should direct the echocardiographer to suspect aortic arch obstruction is the development of tricuspid regurgitation and reduced right ventricular function. Suprasternal views are optimal for aortic arch imaging. Due to the relatively larger size of the “neoaorta,” there will be a change in caliber of the aorta at the usual site of recurrent coarctation, which also makes the diagnosis challenging (Fig. 12.21AC [Video 12.18A]). Mild Doppler flow acceleration at the junction of the reconstructed aorta and native descending aorta is a common finding secondary to the size discrepancy between the two segments (see Fig. 12.20B). Significant anatomic obstruction in the neoaortic arch will typically occur at the distal anastomosis. A significant gradient, a discrete posterior shelf, and significant narrowing compared with the abdominal aorta at the level of the diaphragm are all indicative of recoarctation. An abnormal abdominal Doppler flow pattern with blunted upstroke and continued diastolic forward flow (rather than brief early diastolic reversal) is also consistent with coarctation (Fig. 12.21D). Recoarctation is common and seen in almost 1 in 5 patients. It occurs in the majority of patients within the first 6 months following the procedure, usually within the first 3 months. In HLHS, recoarctation has been shown to exacerbate tricuspid valve regurgitation and ventricular dysfunction as well as increase mortality risk. The Doppler gradient may underestimate the severity of recoarctation and 2D and color Doppler imaging may be required for accurate identification of recoarctation.

In the patient with the Sano shunt modification, the ventriculotomy is typically on the anterior surface of the RV, approximately 1 cm below the native pulmonary valve (now the “neoaortic”) annulus (Fig. 12.22AB). Over time, the right ventricular connection may become severely obstructed secondary to muscular hypertrophy and dynamic obstruction. The sternum may also compress the conduit anteriorly. The origin of the Sano conduit is visualized from the parasternal long-axis view angled toward the right (see Fig. 12.22A). The subcostal sagittal or the parasternal long-axis view may be used to obtain the conduit gradient. The conduit can also be visualized from the subcostal view or a modified apical view (medially with angling anteriorly). As the conduit travels to the PA, it takes an abrupt posterior angulation. The PA end of the conduit is best imaged in a high suprasternal short-axis view (Fig. 12.22BC[Video 12.19A, B]). Depending on the surgical technique, the conduit may arch to the right or left of the neoaorta, connecting to the PA confluence, or proximal right PA or left PA. An optimal Doppler gradient at the distal anastomosis may also be obtained from a suprasternal short-axis view, but, as with the BT shunt, gradients are unreliable for absolute determination of distal pressure. However, pulmonary hypertension is uncommon.

As is true with the right ventricular end of the Sano, the pulmonary insertion of the conduit may also be prone to stenosis. Distortion or stenosis of the PAs is somewhat common. The Sano shunt is valveless, so there is “free” regurgitation, and diastolic Doppler flow reversal may be seen in the branch PAs. The Doppler signal appears as a “to-and-fro” signal with the highest velocity in systole. Diastolic velocities are typically low and taper to the baseline very rapidly (Fig. 12.22E). In contrast to patients with a modified BT shunt, there is an absence of diastolic runoff in the aorta. Stenosis of a Sano shunt may be difficult to evaluate using echocardiography secondary to aliasing and poor acoustic windows. Increasing Doppler velocity and change in the normal sawtooth pattern of the Sano Doppler signal may suggest Sano conduit stenosis. The neoaortic valve is best seen in the subcostal sagittal view and should be evaluated for regurgitation or stenosis. The area of anastomosis between native and neoaorta may become stenotic and should be evaluated from subcostal sagittal and coronal views. Evaluation of systolic and diastolic RV function and tricuspid valve regurgitation should be an integral part of all echocardiographic evaluations.

Figure 12.19. Hypoplastic left heart syndrome; postoperative Stage I Norwood with restriction of the atrial septal defect (ASD). A: Subcostal long-axis (coronal) view showing restriction of surgically created ASD (arrowheads) with thickened tissue rims (Video 12.16A). B: Color Doppler flow demonstrating aliased signal through the narrowed ASD (black asterisk) (Video 12.16B). C: Continuous-wave Doppler interrogation with the gradient (5 to 6 mm Hg) determined by tracing the Doppler flow over two or three cardiac cycles. LA, left atrium; RA, right atrium.

Figure 12.20. Hypoplastic left heart syndrome; postoperative evaluation of normal aortic arch. A: Suprasternal long-axis imaging following Norwood Stage I palliation, demonstrating size discrepancy between the dilated proximal reconstructed neoaorta and the normal-caliber descending aorta. B:Color Doppler flow in the reconstructed aortic arch following Norwood procedure demonstrating mild flow acceleration in this anatomic transition zone secondary to the size discrepancy (Video 12.17).

Figure 12.21. Hypoplastic left heart syndrome; Stage I Norwood with postoperative recurrent coarctation of the aorta. A: Suprasternal long-axis view of arch reconstruction showing recoarctation (asterisk) of aorta at the junction of reconstructed aorta and native descending aorta (DA). Note the more significant size discrepancy than illustrated in normal arch in Figure 12.20 (Video 12.18A). B: Color Doppler interrogation of the aortic arch demonstrating the area of coarctation (arrow) (Video 12.18B). C: Continuous-wave Doppler interrogation of aortic arch using non-imaging probe demonstrating recoarctation of aorta with a mean gradient of 24 mm Hg. D: Pulsed-wave Doppler interrogation of the abdominal aorta in the same patient demonstrates delayed upstroke with continued antegrade flow into diastole (and the absence of diastolic flow reversal) suggestive of significant recoarctation.

Figure 12.22. Postoperative Norwood Stage I palliation with Sano shunt (nonvalved conduit) to the pulmonary arteries. A: Parasternal short-axis view at midventricular level demonstrating the anterior/leftward right ventricular (RV) origin of the Sano shunt (arrow). B:Color Doppler imaging shows aliased flow into the proximal Sano shunt (Video 12.19A). C: High left parasternal view with color Doppler imaging demonstrates systolic forward flow in the Sano shunt (arrow) (Video 12.19B). D: Diastolic flow reversal is seen in the nonvalved conduit (arrow). E: Continuous-wave Doppler imaging of the Sano shunt demonstrating the systolic forward flow and rapid diastolic reversal suggestive of unrestricted conduit regurgitation. LPA, left pulmonary artery; RPA, right pulmonary artery.

Echocardiographic Evaluation Following Hybrid Procedure

Following a hybrid procedure, patients need close regular follow-up. Echocardiography is the mainstay of follow-up surveillance after a hybrid procedure. Apart from RV function and tricuspid valve regurgitation, the echocardiogram should focus on the atrial septum, pulmonary artery bands, ductal stent, and retroaortic arch-gradients. The atrial septum is best imaged in the subcostal coronal and sagittal views. A mean interatrial gradient of ≥8 mm is considered a sign of a restrictive atrial septum and an indication for balloon atrial septostomy or further intervention, such as stent placement. Doppler flow through the PDA stent is bidirectional, with antegrade flow in systole, and reversal of flow in diastole (Fig. 12.23AB). The PDA stent gradient also increases gradually following the procedure. A PDA stent peak velocity of ≥ 3 m/s may suggest in-stent stenosis and warrants further evaluation and treatment. Evaluation of the retroaortic arch for obstruction is critical, since the majority of the systemic cardiac output and coronary artery perfusion occurs through this segment (Fig. 12.23CD). Aortic atresia and small aortic root size are associated with a higher incidence of retroaortic arch obstruction. The high parasternal ductal view is the best view for evaluation of the retroaortic arch, with a peak Doppler velocity <2.5 m/s considered normal. The sensitivity of echocardiography in the evaluation of retroaortic aortic obstruction is suboptimal. A retroaortic arch peak Doppler velocity ≥ 2.5 m/s, concerning 2D findings, progressively increasing retroaortic arch velocity and a lower limb systolic blood pressure ≥ 20 mm Hg higher than the upper limb systolic blood pressure should prompt further evaluation.

The bilateral proximal branch pulmonary artery bands are typically best evaluated in the high parasternal short-axis view (Fig. 12.24AC). Doppler signals are similar to those found in a Blalock-Taussig shunt. The pulmonary artery band gradient should increase gradually with time. Lack of an increase in this gradient or a decrease in the diastolic forward flow across the band may be suggestive of loosening of the pulmonary artery band, downstream obstruction (pulmonary artery or pulmonary vein stenosis), or increasing pulmonary vascular resistance.

Echocardiographic Evaluation of the Bidirectional Cavopulmonary (Glenn) Anastomosis

The second stage in the surgical management of patients with a univentricular AV connection is a bidirectional cavopulmonary anastomosis (or modified bidirectional Glenn shunt) where the right SVC is connected directly to the right PA. In a patient with bilateral SVCs, these anastomoses are performed to both the right PA and left PA. A cavopulmonary shunt is typically performed between the ages of 3 and 6 months. If no other source of pulmonary blood flow is present, the volume load on the heart is significantly decreased once the cavopulmonary shunt is constructed, which is of particular benefit to the patient with a systemic RV. The right cavopulmonary anastomosis is best visualized from the suprasternal short-axis view. In this view, the entire length of SVC and anastomosis to the right PA can be seen (Fig. 12.25AB [Video 12.20A, B]). With color Doppler interrogation, there is laminar venous flow (Fig. 12.25C). The Nyquist limit should be lowered to appreciate the low-velocity flow. Doppler interrogation over multiple cardiac cycles will show variation with respiration. In the absence of any additional blood flow, pulsed-wave Doppler interrogation of the SVC or branch PA will show biphasic, low-velocity forward flow with significant accentuation of flow with inspiration. Continuous flow at mildly elevated velocities that does not return to the Doppler baseline is very suggestive of obstruction. If present, tracing the mean gradient over three cardiac cycles will likely show a gradient of more than 3 mm Hg. In the venous system, such a gradient may be clinically significant. Noting the presence of a dilated azygous vein (if it was not surgically ligated) warrants a careful evaluation for obstruction in the cavopulmonary anastomosis. One should also be vigilant in looking for PA stenosis or distortion at the site of the previous BT or Sano shunt, including evaluating the caliber of the branch PAs by 2D imaging.

Echocardiographic Evaluation of the Fontan Circulation

The evaluation of a patient following completion of the modified Fontan procedure will be covered elsewhere in the text.

Figure 12.23. Hypoplastic left heart syndrome following hybrid palliation. A: Suprasternal long-axis view showing stent in patent ductus arteriosus (PDA, asterisk). B: Doppler interrogation in the PDA stent showing typical antegrade flow through the stent into the descending aorta in systole (below the baseline) with retrograde flow in the stent in diastole (above the baseline) C: Color Doppler flow (arrow) in the proximal retroaortic arch segment, demonstrating no evidence of coarctation D: Typical low-velocity Doppler in retroaortic arch segment confirming the absence of a significant gradient to retrograde flow into the ascending aorta from the ductal stent. DA, descending aorta.

Figure 12.24 Hypoplastic left heart syndrome following hybrid palliation. A: High left parasternal short-axis view demonstrating the pulmonary artery bifurcation and aliasing of color Doppler flow due to the presence of bilateral pulmonary artery bands (arrows). B: Angling of the transducer more rightward from the high left parasternal view brings the proximal right pulmonary artery band into view (arrow). C: High left parasternal view showing the proximal left pulmonary artery band (arrow) and the ductal stent (asterisk). D: Typical Doppler pattern obtained in the proximal pulmonary artery bands, with higher systolic velocity and continuous forward flow into diastole. LPA, left pulmonary artery; RPA, right pulmonary artery.

Figure 12.25. Right bidirectional Glenn shunt (cavopulmonary anastomosis). A: Suprasternal short-axis view of the widely patent anastomosis (asterisk) between the right superior vena cava (SVC) and right pulmonary artery (RPA) (Video 12.20A). B: Color Doppler imaging of the Glenn shunt (asterisk) showing low-velocity laminar flow from SVC to the pulmonary artery. Note the use of a low Nyquist limit to document laminar venous flow (Video 12.20B). C: Pulsed-wave Doppler interrogation demonstrating normal phasic flow with accentuation during atrial contraction and ventricular diastole. Ao, aorta; IN, innominate vein; PA, pulmonary artery.

SUMMARY

In conclusion, echocardiographic evaluation of the neonate with univentricular AV connection is critical for diagnosis, early management, and planning the approach to initial palliation.

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Questions

1.A 3-month-old male with hypoplastic left-heart syndrome who underwent a Norwood procedure with a right ventricle to pulmonary artery conduit at one week of age presents to a high-risk clinic with sweating during feeding and failure to gain weight. A 2-D echo was performed. Compared to an echocardiogram performed a month ago, the echocardiogram at this clinic visit showed worsening tricuspid regurgitation and a mild decrease in right ventricular systolic function. There is no history of interim illness, hospitalization, or medication change since last clinic visit. The most likely explanation for this change on echo is:

A.branch pulmonary artery stenosis.

B.right ventricular to pulmonary artery conduit stenosis.

C.aortic arch obstruction.

D.restriction of atrial septal defect.

E.coronary artery obstruction.

2.A 3-year-old female with double-inlet left ventricle and L-transposed great arteries underwent pulmonary artery banding at two months of age followed by bidirectional cavopulmonary anastomosis and resection and oversewing of the main pulmonary artery at eight months of age. In preparation for Fontan, she underwent an echocardiogram that showed a peak gradient of 50 mm Hg from the left ventricle to the aorta (across the bulboventricular foramen). LV function is normal with an estimated ejection fraction of 55%. There is no atrioventricular valve regurgitation. The next best step in the management of this patient is:

A.proceed with Fontan procedure, the subaortic obstruction will get better following Fontan.

B.Fontan procedure should be combined with enlargement of VSD.

C.subaortic obstruction should be addressed first followed by Fontan at a later date.

D.reconstruction of main pulmonary artery and a Damus-Kay- Stansel procedure.

E.patient should be referred for cardiac transplantation.

3.A newborn with a prenatal diagnosis of hypoplastic left-heart syndrome develops acute respiratory distress and worsening cyanosis within an hour following birth. As an echocardiographer, what is the most important issue that most likely needs immediate evaluation and potential intervention?

A.Severe coarctation of aorta

B.Right ventricular dysfunction

C.Coronary artery fistula

D.Atrial septal restriction

E.Severe tricuspid regurgitation

4.A newborn with tricuspid atresia, transposed great arteries, and a small ventricular septal defect presents with acute onset respiratory distress and hypotension. What is the most likely explanation for this presentation?

A.Restricted atrial septal defect

B.Severe pulmonary valve stenosis

C.Coarctation of the aorta

D.Branch pulmonary artery stenosis

E.Aortic valve regurgitation

5.A one-week-old female presents with coarctation of the aorta. A 2-D echocardiogram was performed that shows discrete coarctation of aorta with mild transverse arch hypoplasia. The aortic valve and ascending aorta are normal in size. The right ventricle is dilated and hypertrophied with mildly reduced systolic function and the left ventricle is mildly hypoplastic but apex forming with normal systolic function. There is no evidence of mitral valve stenosis and there is a small patent foramen ovale with predominantly left-to-right shunting. The remainder of the echocardiogram was normal. Which of the following statements is most likely to be true in this patient?

A.Rhodes score should be used for assessment of left-ventricle adequacy before surgery.

B.The CHSS (Congenital Heart Surgeon’s Society) score should be used for assessment of left-ventricle adequacy before surgery.

C.Patient should undergo aortic arch repair only.

D.Patient should undergo a Norwood procedure and single ventricle palliation.

E.Patient should not have any surgery and palliative care should be recommended.

6.Following a hybrid procedure for hypoplastic left-heart syndrome, a four-week-old newborn develops progressive cyanosis. The most likely explanation for this finding is:

A.restricted atrial septal defect.

B.reverse coarctation.

C.reduced right ventricular systolic function.

D.worsening tricuspid regurgitation.

7.Following a bidirectional cavopulmonary anastomosis, an eight-month-old female develops progressive facial edema. On echo, the superior vena cava to pulmonary artery anastomosis Doppler shows a mean gradient of 3 mm Hg with loss of phasic flow and respiratory variation. What is the next best step in the management of this patient?

A.Gradient is too low to be clinically significant

B.Cardiac catheterization and angiography with intervention if obstruction is found

C.A mean gradient of 3mm Hg is a normal finding in the cavopulmonary anastomosis

D.Patient needs close monitoring and intervention if the mean gradient increases above 6 mmHg.

8.A seven-week-old infant with HLHS who had a Stage I Norwood palliation with a modified Blalock-Taussig shunt presents with acutely worsening cyanosis. The most likely echocardiogram finding that would explain this clinical situation is:

A.worsening tricuspid regurgitation.

B.worsening right ventricular function.

C.increased modified Blalock-Taussig shunt gradient.

D.recoarctation of aorta.

9.An individual with bulboventricular foramen area less than the following would be considered at higher risk for developing late obstruction:

A.1.5 cm2/m2

B.3 cm2/m2

C.2 cm2/m2

D.4 cm2/m2

10.In a newborn with tricuspid atresia and transposed great arteries, the echocardiogram was interpreted as showing a large secundum atrial septal defect (ASD) and severe pulmonary valve stenosis. On Day 5 of life, the patient underwent a modified Blalock-Taussig shunt and resection of the atrial septum. On surgical inspection of the atrial septum, the orientation of atrial septum was abnormal and there was no evidence of a large secundum ASD and only a patent foramen ovale (PFO). What was the most likely explanation for echocardiographic misdiagnosis of atrial septal defect in this case?

A.The ASD reduced in size spontaneously to a PFO.

B.On cardiopulmonary bypass, large atrial septal defects often appear like a PFO.

C.Patient had left-juxtaposed right-atrial appendage.

D.Patient had right-juxtaposed left-atrial appendage.

E.Patient had a sinus venosus ASD that was missed by surgeon.

Answers

1.Answer: C. Recurrent aortic arch obstruction after Norwood procedure (Stage 1 palliation) for hypoplastic left-heart syndrome (HLHS) is not uncommon and often presents with worsening of right ventricular (RV) systolic function. Timely intervention on the recoarctation usually results in recovery of right ventricular systolic function. Recoarctation should be excluded in all patients with HLHS who underwent a Norwood procedure who present with reduced RV systolic function. Conduit or PA branch stenosis typically presents with increasing cyanosis and ventricular function is typically preserved; restriction of the ASD will also present with worsening cyanosis and increased work of breathing. Coronary artery obstruction is rare and more likely to present immediately after the Norwood procedure.

2.Answer: B. A peak gradient of 50 mm Hg across bulboventricular foramen suggests significant obstruction to left ventricular outflow. Systemic outflow obstruction across the bulboventricular foramen in single ventricle patients is known to be progressive. If the VSD is not enlarged during the Fontan operation, progressive LV outflow tract obstruction can result in LV hypertrophy and LV systolic and diastolic dysfunction resulting in Fontan failure. Reconstruction of the over-sewn MPA to create a Damus-Kaye-Stansel connection would be very difficult in this setting. If the patient has preserved ventricular function, there is no reason to consider transplantation at this early age.

3.Answer: D. In newborns with HLHS or critical left-heart obstruction, the existence of an unobstructed interatrial communication is crucial for delivery of oxygenated blood to the body and to prevent pulmonary vascular congestion and edema. In newborns with HLHS and acute onset of respiratory distress, adequacy of the interatrial communication should be assessed immediately. If there is restriction of flow at the atrial septum or the atrial septum is thick and intact, urgent cardiac catheterization should be arranged to relieve the septal obstruction and improve oxygenation. Alternatively, an early Stage I Norwood could be performed if the atrial septal anatomy appears unfavorable for intervention. Subcostal coronal and sagittal imaging planes are ideal for evaluation of the interatrial septum. Pulsed-wave Doppler-derived mean gradients are used for quantifying the atrial septal restriction. The other issues listed will rarely cause immediate decompensation in a newborn with HLHS.

4.Answer: C. In patients with tricuspid atresia, transposed great arteries, and a small ventricular septal defect (VSD), the aorta arises from the hypoplastic right ventricle. The size of aorta and aortic arch is usually directly proportional to the amount of blood flow across the ventricular septal defect into the ascending aorta. When the VSD is small, there is limited blood flow across the aortic valve, ascending aorta, and aortic arch during fetal life, which results in hypoplasia of the aortic valve, ascending aorta, and aortic arch and coarctation of the aorta or interrupted aortic arch. Acute onset of respiratory distress and hypotension in the neonatal period in these patients is likely secondary to closing of the patent ductus arteriosus, resulting in reduced systemic perfusion secondary to coarctation of the aorta. Atrial septal restriction is very unusual in tricuspid atresia. In the setting of transposition, valvular pulmonary stenosis is also highly unlikely; branch PA stenosis would not typically cause hemodynamic decompensation, nor would aortic valve regurgitation, as most of the systemic output will be supplied from the ductus arteriosus.

5.Answer: C. In neonates with coarctation of the aorta, the right ventricle is often enlarged and hypertrophied, and when the ductus arteriosus closes, right ventricular function can deteriorate. In these patients, the left ventricle often appears mildly hypoplastic but is usually apex forming. In these patients, in the absence of aortic or mitral valve stenosis, correction of coarctation of the aorta results in normalization of ventricular size discrepancy. Rhodes and CHSS scores for evaluation of left-ventricular adequacy for biventricular repair have only been validated for critical aortic stenosis. These scores should not be used in conditions where the right ventricle is dilated and the left ventricle is compressed due to abnormal loading conditions like coarctation of aorta or total anomalous pulmonary venous return.

6.Answer: A. Unlike Norwood surgical palliation, where patients undergo a surgical atrial septectomy, in a hybrid procedure the atrial septal defect is enlarged using a transcatheter approach. If balloon septostomy is all that is originally performed, patients who undergo a hybrid procedure are at higher risk for restriction at the atrial septum. A restrictive ASD can lead to progressive cyanosis secondary to lack of adequate mixing of oxygenated blood. Restriction at the atrial septum in these patients is usually addressed using a transcatheter approach with implantation of a stent.

7.Answer: B. In a univentricular heart following bidirectional cavopulmonary anastomosis, scarring and distortion of the superior vena cava and/or pulmonary artery can result in stenosis of the cavopulmonary anastomosis. In these cavopulmonary anastomosis circuits with passive venous flow, even a small gradient (1-2 mm Hg) can be hemodynamically significant and should prompt further investigation and intervention if obstruction is found. Loss of low-velocity phasic flow and small gradients, especially in the presence of signs of superior vena caval obstruction like facial edema, should prompt further investigation to define the anatomy of the cavopulmonary anastomosis and to perform definitive intervention as warranted. In a patient like this with clinical symptoms, a full evaluation is warranted.

8.Answer: C. In a single ventricle patient with a modified Blalock-Taussig shunt, the most likely cause for early onset of worsening cyanosis is stenosis of the shunt (or pulmonary artery branches). Since this modified Blalock-Taussig shunt is the only source of pulmonary blood flow in the above-described patient, an increased shunt gradient is most likely secondary to shunt stenosis. It is important to remember that accuracy of the Bernoulli equation for estimation of the pressure gradient across stenotic Blalock–Taussig shunts is poor and a single value in isolation is of limited value. However, serial echocardiograms showing an increasing shunt gradient with worsening cyanosis points to a shunt obstruction that should be further investigated. Coarctation of the aorta will typically lead to worsening RV function and increasing tricuspid regurgitation. Worsening of TR/RV function will usually cause symptoms of congestive heart failure prior to a significant change in saturations.

9.Answer: C. Bulboventricular foramen obstruction may result in systemic ventricular outflow tract obstruction in single left-ventricle patients with transposed great arteries. The bulboventricular foramen is measured in two orthogonal planes by 2-D echocardiography, its area calculated, and then indexed to body surface area (see Chapter 12). A bulboventricular foramen area less than 2 cm2/m2 would be considered at higher risk for developing late obstruction.

10.Answer: C. Left-juxtaposed right-atrial appendage can be misdiagnosed as a secundum atrial septal defect on a 2-D echocardiogram. In patients with tricuspid atresia, left-juxtaposed right atrial appendage may be present and is more common in patients with transposed great arteries and pulmonary stenosis. The echocardiographic features of left-juxtaposed right atrial appendage include: 1) horizontal orientation of the anterior atrial septum, which represents the floor of the left-juxtaposed right atrial appendage and 2) the left and right atrial appendages are both to the left of the great arteries and the anteriorly-located right atrial appendage could be visualized coursing beneath the great arteries and leftward over the left atrial cavity. This can be best visualized in the parasternal short-axis view. A large secundum ASD should not reduce in size to a PFO within five days. A large secundum or sinus venosus ASD should not be missed on surgical inspection. Right-juxtaposed left atrial appendage is rare in tricuspid atresia and should not result in the above echocardiographic findings.