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

5. Anomalies of the Pulmonary and Systemic Venous Connections

ANOMALOUS PULMONARY VENOUS CONNECTIONS

Introduction, Nomenclature, and Embryogenesis

Abnormalities associated with connections of the pulmonary veins are rare and comprise 0.5–1.5% of cases of congenital heart disease (CHD). These abnormalities traditionally have been divided into two major subgroups. Total anomalous pulmonary venous connection (TAPVC) occurs when all of the pulmonary veins from both lungs do not connect normally to the left atrium (LA) but instead connect to systemic veins in the chest or abdomen or directly to the right atrium (RA). With rare exception, it is obligatory for patients with TAPVC to have an atrial septal defect (ASD) or patent foramen ovale (PFO) to sustain life. Partial anomalous pulmonary venous connection (PAPVC) constitutes the abnormal connection of one or several pulmonary veins. But, in PAPVC at least one pulmonary vein connects normally to the LA. PAPVCs can have a large variety of connections to systemic veins or the RA. Most patients with PAPVC have an ASD.

There are important clinical differences between the two subgroups. Patients with a TAPVC will usually present early in life with cyanosis and severe pulmonary hypertension secondary to pulmonary venous obstruction, whereas patients with a PAPVC will usually be asymptomatic in childhood. Patients with PAPVC may be discovered incidentally in adulthood or present with signs and symptoms similar to an ASD. Meticulous echocardiographic assessment from multiple imaging planes is essential to confidently establish that the pulmonary venous connections are normal. If one cannot identify all of the pulmonary veins, then an exhaustive search for the pulmonary venous connections must ensue. If transthoracic echocardiography (TTE) is non-diagnostic, then other imaging modalities must be utilized, such as transesophageal echocardiography (TEE), computed tomography (CT), magnetic resonance imaging (MRI), or, rarely, cardiac catheterization.

Normally, there are two right-sided and two left-sided pulmonary veins. Although the normal right lung has three lobes, the right middle and upper veins usually join before entering the LA. The most common variation in normal pulmonary venous anatomy is to have a single pulmonary vein from either lung (a single left vein is more common). Healey reported in 1952 that this occurs in as many as 24% of anatomic specimens. During early embryogenesis, part of the splanchnic plexus forms the pulmonary vascular bed. The pulmonary vascular bed is connected to the umbilicovitelline and cardinal venous systems. The pulmonary vascular bed is not connected to the heart during early development. Eventually, an evagination from the LA joins the interparenchymal pulmonary veins to form the “common pulmonary vein.” The common pulmonary vein, also termed a pulmonary venous confluence, becomes incorporated completely into the LA during the first month of gestation. Once this connection to the heart is established, the original pulmonary venous attachments to the splanchnic plexus involute. All abnormalities of pulmonary venous connections can be understood based on the original development of the pulmonary veins from the splanchnic plexus (Fig. 5.1). In 2001, Tal Geva and Stella van Praagh provided an excellent review of pulmonary venous embryology and anomalies (Moss and Adams: Heart disease in infants, children and adolescents). This chapter is recommended reading for those interested in further description of the embryogenesis of pulmonary venous anomalies.

A distinction should also be made between the exact anatomic “connection” of a pulmonary vein to the LA or other vessel/chamber and the “drainage” of a pulmonary vein. Although a pulmonary vein may “connect” normally to the LA, if malposition of the atrial septum (Fig. 5.2) or an ASD is present, pulmonary venous flow may actually “drain” across the interatrial defect into the RA. Therefore, the echocardiographer should use this terminology carefully when communicating with a surgeon.

Features of Transthoracic (TTE) Imaging of Pulmonary Venous Connections

Accurate delineation of the pulmonary venous connections to the LA requires clear two-dimensional imaging from multiple imaging windows. Color and spectral Doppler imaging is required to demonstrate flow from each pulmonary vein into the LA. Suspicion of APVC should be raised if right-sided volume is demonstrated, especially if no interatrial communication is observed. In newborns, suspect TAPVC if the left atrial size is reduced.

Figure 5.1. Embryologic development of the pulmonary veins from the splanchnic plexus during the first month of embryogenesis. A: Lung buds connected to the splanchnic plexus. No connection to heart exists at this point. LCCV, left common cardinal vein; RCCV, right common cardinal vein; UV, umbilicovitelline vein. B: Later in development, the common pulmonary vein (CPV) has evaginated from the left atrium (LA) and connected to the pulmonary venous plexus. The pulmonary veins are connected to the splanchnic plexus and the heart at this point in development. LLB, left lung bud; RLB, right lung bud. C: The connections to the splanchnic plexus involute. D: By term, the common pulmonary vein has become completely incorporated into the LA and the individual veins connect to the LA. (From Geva T, Van Praagh S. Anomalies of the pulmonary veins. In: Allen HD, Gutgesell HP, Clark EB, Driscoll DJ, eds. Moss and Adams’ Heart Disease in Infants, Children and Adolescents. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2001:736–772. Originally adapted from work by R. C. Anderson, with permission.)

Subcostal Frontal (Four-Chamber) and Sagittal Views

The subcostal frontal and sagittal views offer precise imaging of the connections of the pulmonary veins, especially in infants. Likewise, these views are useful in the assessment of the atrial septum since the plane of sound is perpendicular to the plane of the septum. Frequently, a sinus venosus defect can be adequately assessed from the subcostal sagittal plane, obviating the need for alternative imaging. The subcostal sagittal view with rightward angulation offers a unique view of the right upper pulmonary vein as it travels between the superior vena cava (SVC) (anterior) and the right pulmonary artery (posterior) (Fig. 5.3A). When one rotates the transducer 90 degrees back to the frontal view, the SVC will no longer be visualized, but assessment of the right lower pulmonary vein (Fig. 5.3B) can occur. The os of the coronary sinus can also be evaluated from the subcostal frontal plane image; dilation of the coronary sinus may suggest APVC.

Figure 5.2. Subcostal frontal plane view (four-chamber) demonstrating normal “connection” of the right upper pulmonary vein (PV) to the left atrium (LA). However, due to malposition of the primum atrial septum (Sept 1°), the “drainage” from this vein is directed to the right atrial (RA) side of the septum.

Parasternal Long- and Short-Axis (PSLA and PSSA) Views

PSLA images with leftward angulation will demonstrate the connection of one or both left pulmonary veins to the LA. Color flow interrogation at the posterior aspect of the cardiac border can demonstrate these flows (Fig. 5.3C). PSSA images demonstrate the anterior and posterior aspects of the atrial septum. The connection of the right lower pulmonary vein to the LA can be demonstrated with rightward angulation when one focuses on the posterior edge of the atrial septum. PSSA at the level of the main pulmonary artery demonstrates the connection of the left pulmonary veins to the LA. A dilated coronary sinus may also be detected in the PSSA scans as well as the os of the coronary sinus between the tricuspid inlet and the inferior vena cava (IVC)-RA junction. The high right parasternal window offers a unique view of the relationship of the SVC and the right pulmonary veins. Figure 5.3D demonstrates three right-sided pulmonary veins connecting to the LA in a normal fashion.

Apical Four-Chamber View

The apical four-chamber image clearly demonstrates the connection of the right lower and left lower pulmonary veins (Fig. 5.3E). A common misconception is that the right upper pulmonary vein is demonstrated in this scanning plane. However, the true apical four-chamber image, which evaluates the crux of the heart and the hinge points of the atrioventricular (AV) valves, is not oriented in an anterior-to-posterior plane. Instead, the scan is entirely posterior from a superior-to-apical perspective, providing excellent imaging of the posteriorly positioned AV valves, the entrance of the IVC into the RA, and the respective lower pulmonary veins. From this view, with anterior angulation, the right upper vein connection to the dome of the LA can be visualized, but this requires one to move away from the plane of the AV valves.

Figure 5.3. Two-dimensional imaging from multiple imaging windows. A: Quad-image from the subcostal sagittal window demonstrating the relationships of the superior vena cava (SVC), right pulmonary artery (R), atrial septum, and right upper pulmonary vein. Left:Normal connection of the SVC to the RA with color flow demonstrated toward the transducer. Right: With rightward angulation, the course of the right upper pulmonary vein (asterisk) can be demonstrated as it travels between the SVC and the RPA. B: Subcostal frontal plane view of the atrial septum and right lower pulmonary vein (asterisk). C: Parasternal long-axis image of flow from a left pulmonary vein (black arrow) entering the LA. D: High right parasternal image demonstrating the relationship of the right upper pulmonary vein (RUPV), right middle pulmonary vein (RMPV), and right lower pulmonary vein (RLPV) to the SVC as the right veins enter the LA. E: Pathologic specimen in an apical four-chamber projection demonstrating normal connection of the right lower pulmonary vein (RLPV) and left lower pulmonary vein (LLPV) to the left atrium.

Suprasternal Notch Short-Axis or “Crab View”

The “crab” view (Fig. 5.4AC) permits the identification of all pulmonary veins connecting to the LA and should be part of all routine TTE assessments. This image usually provides excellent imaging of the normal pulmonary veins in small children. Adult echocardiography laboratories do not typically obtain this view. The Mayo Clinic congenital echocardiography laboratory demonstrated that the suprasternal notch short-axis view was obtained in 74% of 200 consecutive adult patients studied. But in this cohort, 2D and color Doppler imaging adequately demonstrated the connection of all pulmonary veins in only 46% of patients. Parameters of body habitus (body mass index, body surface area, height, and weight) did not correlate with ability to adequately evaluate the pulmonary venous connections (P. Katanyuwong, Mayo Clinic, unpublished data). In the crab view, avoid the pitfall of mistaking the LA appendage for the left upper pulmonary vein (Fig. 5.4D).

Total Anomalous Pulmonary Venous Connection

TAPVC is usually classified according to the position of the anomalous connection relative to the heart, and TAPVC is divided into four major subtypes (Fig. 5.5).

■Supracardiac

■Cardiac

■Infracardiac

■Mixed

In the supracardiac type of TAPVC, the pulmonary veins come together to form a confluence that does not enter the left side of the heart but instead enters a “vertical vein” (usually on the left side of the chest), which drains to the innominate vein (Fig. 5.6A). This is the most common type of TAPVC, accounting for 40–50% of cases in autopsy series. The anomalous vertical vein is an embryologic remnant of the splanchnic and cardinal systems. Children may come to medical attention due to an abnormal chest radiograph and enlargement of the right side of the heart. The chest radiograph is classically described as having a “snowman” appearance (Fig. 5.6B). These children generally have difficulty gaining weight and are tachypneic. In the more common form of supracardiac TAPVC, the left vertical vein originates from the pulmonary venous confluence and travels anterior to the left pulmonary artery (LPA), left mainstem bronchus, and aortic arch before it joins the innominate vein just proximal to where the left internal jugular and left subclavian veins join (Fig. 5.7). However, when the left vertical vein passes between the LPA and the left mainstem bronchus, it may become obstructed. This is referred to as a “vascular vise” (Fig. 5.8). The vertical vein is not referred to as a “left superior vena cava.” The term “left superior vena cava” should be used when a left-sided chest vessel connects the innominate vein to the coronary sinus or LA (Fig. 5.9). In cardiac TAPVC, all pulmonary veins connect to a vessel that directly enters the right atrium (usually the coronary sinus). These connections are usually unobstructed (Fig. 5.10). In infracardiac TAPVC, all of the pulmonary veins connect to a vertical vein that descends below the diaphragm (Fig. 5.11). This connection below the diaphragm occurs due to failed involution of the connection to the umbilicovitelline system. This form of TAPVC is associated with severe pulmonary hypertension and obstruction of the vertical vein as it crosses the diaphragm or enters the relatively smaller-caliber veins in or near the liver. Obstruction most commonly occurs as the infracardiac vertical vein enters the portal vein. Connection to the ductus venosus, hepatic veins, or IVC has also been observed. Infracardiac TAPVC usually requires emergent surgery in the first hours after birth. Angiography (Fig. 5.12A) or alternative imaging modalities rarely are needed to better delineate the course of the pulmonary veins before surgical repair. Infracardiac TAPVC should be suspected in newborns who present with respiratory distress and diffuse bilateral pulmonary venous congestion on chest radiography (Fig. 5.12B).

Figure 5.4. “Crab” views. A: Pathologic specimen similar to the suprasternal notch short-axis view demonstrating normal pulmonary venous connections. Coined the “crab view,” all four pulmonary veins can usually be identified from this scanning plane. This view is usually diagnostic in small children. This imaging window may not be as accessible in adults. Ao, aorta; LA, left atrium; LLPV, left lower pulmonary vein; LUPV, left upper pulmonary vein; RLPV, right lower pulmonary vein; RPA, right pulmonary artery; RUPV, right upper pulmonary vein; SVC, superior vena cava. B: Corresponding two-dimensional echocardiograph demonstrating the LA and the relative positions of the four pulmonary vein entrances (yellow asterisks). C: Diagram of the “crab” superimposed on a suprasternal short-axis image demonstrating an abnormal “crab view.” The RLPV is not demonstrated entering the LA in this patient with scimitar syndrome. D: Suprasternal short-axis view demonstrating an imaging pitfall. In this image, the yellow asterisk depicts the LA appendage and not the LUPV. E: A “true” crab view in which the pulmonary veins (arrows) are clearly identified connecting to the LA. The course of the proximal RPA just posterior to the ascending Ao is also demonstrated.

Figure 5.5. Three forms of total anomalous pulmonary venous connection (TAPVC): supracardiac type (left), cardiac type to the coronary sinus (middle), infracardiac type (right). CPV, pulmonary venous confluence.

Figure 5.6. Supracardiac total anomalous pulmonary venous connection (TAPVC). A: Diagram depicting supracardiac TAPVC. The respective right (RPV) and left (LPV) pulmonary veins connect to a confluence (CPV) that is superior to the dome of the left atrium (LA). The pulmonary venous confluence connects to a dilated vertical vein (VV). In turn, the vertical vein connects to the left innominate vein (L Inn. V) and ultimately the superior vena cava (SVC). Both the SVC and innominate vein will appear dilated. CS, coronary sinus; IVC, inferior vena cava. B: Chest radiograph in a child with supracardiac TAPVC demonstrating the “snowman” sign. The left-sided mediastinal shadow (black arrow) is the dilated VV. The right-sided mediastinal shadow (white arrow) is the dilated SVC.

Figure 5.7. More common anatomic form of supracardiac total anomalous pulmonary venous connections (TAPVC). Top: Apical four-chamber view demonstrating right atrial (RA) and right ventricular (RV) dilation in a child with supracardiac TAPVC. Bottom left: Two-dimensional suprasternal notch image of a left-sided vertical vein (VV) connecting to the innominate vein (Inn V). Ao, aorta. Bottom right: Color Doppler image in the same plane demonstrating cephalad (red) flow in the vertical vein as it joins the innominate vein. SVC, superior vena cava.

Figure 5.8. “Vascular vise.” Left: Subcostal coronal image demonstrating the pulmonary venous confluence (asterisk) with the appearance of a “hat” on top of the superior aspect of the left atrium (LA). Right: Suprasternal short-axis view with color Doppler demonstrating a left vertical vein with aliased flow (arrow) at the point of a “vascular vise.” The vertical vein is partially obstructed as it passes between the left mainstem bronchus and the left pulmonary artery.

The diagnosis of infracardiac TAPVC may be particularly challenging in the premature newborn with lung disease. The signs and symptoms may be misinterpreted as persistent pulmonary hypertension. Echocardiographic imaging can be especially difficult if the patient is intubated and requires aggressive ventilator management. Clear 2D images of the pulmonary veins may be limited. In these patients, both color and spectral Doppler techniques need to be extensively used to ensure that flow from the pulmonary veins is demonstrated into the LA. In some situations, these neonates deteriorate rapidly. Resuscitation may include extracorporeal membrane oxygenation (ECMO). If the diagnosis of TAPVC is not established before initiation of ECMO, it may be difficult to wean the child from the circuit. In these circumstances, an alternative imaging method, such as angiography, may be useful to discover obstructed infracardiac TAPVC. Relief of pulmonary venous obstruction is needed to wean from ECMO.

The fourth and least common type of TAPVC is generically referred to as “mixed.” This form represents a combination of at least two of the other types. In the mixed form of TAPVC, there is no true pulmonary venous confluence. Imaging errors can easily be made in this situation. Unilateral obstruction may occur and patients with heterotaxy syndromes are predisposed to the mixed form of TAPVC. Patients with heterotaxy syndromes with situs ambiguous of the atria may have “ipsilateral” anomalous pulmonary veins, wherein the right and left veins connect to their respective sides of a common atrium.

Figure 5.9. Pulmonary vein stent placement. 3D CT reconstruction images in a young adult who was born with TAPVC to the coronary sinus. After neonatal repair he developed bilateral pulmonary vein stenosis. He required multiple surgical revisions and cath lab interventions. This ultimately resulted in stent placement to relieve obstruction in the left atrial appendage/left pulmonary vein connection and in the reconstructed right pulmonary vein confluence (A and B: arrows). He struggled with elevated RV systolic pressures through much of his young life but eventually achieved normal RV pressures after the most recent intervention at age 17 years.

Figure 5.10. Dilated coronary sinus. A: Apical four-chamber scan demonstrating a dilated coronary sinus (asterisk) in a patient with anomalous pulmonary venous connection to the coronary sinus. B: Color Doppler image in the same projection as A, demonstrating antegrade flow in the coronary sinus (yellow asterisk). C: Pathologic specimen from a posterior view demonstrating a pulmonary venous confluence connecting to a dilated coronary sinus (asterisk) in a cardiac form of total anomalous pulmonary venous connections (TAPVC).

Figure 5.11. Newborn patient with mild cyanosis and tachypnea. A: The pulmonary venous confluence (PVC) fails to connect to the dome of the left atrium (LA). B: A vertical vein (VV) in this patient descends below the diaphragm and enters the liver, where it is partially obstructed. C: Color Doppler image in the same projection as B, demonstrating flow from the vertical vein into the liver (red). D: Two-dimensional image in a different patient demonstrating an anomalous pulmonary vein (APVC) entering the right atrium (RA)–inferior vena cava (IVC) junction. E: Color Doppler of the patient in D demonstrating flow from the APVC into the RA–IVC junction.

Partial Anomalous Pulmonary Venous Connections

PAPVC, first described by Winslow in 1739, is an uncommon congenital anomaly found in 0.4% to 0.7% of autopsy series, therefore the true incidence may be higher. Both TTE and TEE have major roles in the detection of PAPVC. Echocardiography is important in the evaluation of associated hemodynamic changes such as volume overload of the right heart chambers, tricuspid regurgitation, and pulmonary hypertension. Children with PAPVC may be asymptomatic and escape detection until adulthood. When symptomatic, patients with PAPVC present with dyspnea, fatigue, atrial arrhythmia, pulmonary hypertension, unexplained cardiomegaly on chest radiograph, or unexplained right ventricular volume overload on TTE. PAPVC can be an isolated defect with an intact atrial septum or associated with a PFO or ASD. PAPVC is associated with 85% of patients with sinus venosus defects. In addition, PAPVC has been associated with AV septal defect, tetralogy of Fallot, congenitally corrected transposition and Turner syndrome.

PAPVC can involve the right- or left-sided pulmonary veins and rarely arises from both lungs in the same patient. If one includes patients with the sinus venosus defect, the most common form of PAPVC is a right-sided pulmonary vein connecting to the SVC or RA. As an isolated lesion, the most common form of PAPVC is connection of a left-sided pulmonary vein to the innominate vein via a left vertical vein. In addition, there are many reports of PAPVC to the left subclavian vein, brachiocephalic vein, azygous vein, portal vein, and coronary sinus. Essentially, PAPVC may occur to any thoracic systemic vein.

Figure 5.12. Infracardiac total anomalous pulmonary venous connection (TAPVC). A: Typical angiogram of an infant with infracardiac TAPVC demonstrating the descending vertical vein (VV), right lower pulmonary vein (RLPV), left lower pulmonary vein (LLPV), and left upper pulmonary vein (LUPV). B: Typical chest radiograph in a newborn with obstructed infracardiac TAPVC demonstrating diffuse pulmonary venous congestion.

Right Pulmonary Veins to the RA or SVC

Two-dimensional TTE combined with color flow Doppler are excellent diagnostic tools for visualization of PAPVC, particularly in children and young adults. The suprasternal short-axis view shows connection of the right upper pulmonary vein (RUPV) to the SVC. This scanning plane allows visualization of the innominate vein, SVC, aorta, and right pulmonary artery. In PAPVC of the right upper and/or middle pulmonary vein to the SVC, an abnormal color Doppler signal can be seen entering the wall of the SVC, and the flow is directed toward the suprasternal notch (Fig. 5.13). Spectral Doppler assessment of that signal will confirm the presence of a systolic and diastolic flow pattern typical of pulmonary venous flow.

Most patients with a sinus venosus defect will also have partial anomalous connection of the right pulmonary veins (usually upper and middle) to the RA and/or SVC. In children and thin adults, this can be adequately evaluated from the subcostal window (Fig. 5.14). The use of the term “ASD” is actually a misnomer in these patients. The anatomic defect is between the walls of the SVC and the right upper pulmonary vein as they cross each other. One form of surgical correction uses the “ASD” to baffle the right pulmonary venous flow to the LA.

Isolated anomalous connection of the right upper pulmonary vein to the SVC may occur in the absence of an ASD. The anomalous connection of the RUPV to the SVC may occur cephalad of the level azygous vein. When associated with a sinus venosus defect, the connection of the RUPV is typically below the level of the azygous connection to the SVC, the SVC–RA junction, or directly to the RA. A “high” connection of an anomalous RUPV to the SVC may be missed with TTE and TEE. During TEE, the probe should be withdrawn far enough in the esophagus to allow imaging cephalad of the azygous vein–SVC junction so that a high connection of the right pulmonary vein to the SVC is not missed.

Figure 5.13. Transthoracic short-axis view from the suprasternal notch demonstrating anomalous connection of a right pulmonary vein to the superior vena cava (SVC) (arrow). Inn, innominate vein; Ao, aorta; LA, left atrium; RPA, right pulmonary artery.

Figure 5.14. Sinus venosus atrial septal defect (ASD). A: Pathologic specimen of anomalous connection of two right pulmonary veins (asterisks) to the right atrium (RA). B: Left: Subcostal frontal image with superior angulation demonstrating a sinus venosus ASD (asterisk). Center: Subcostal sagittal orientation demonstrates the sinus venosus ASD (asterisk) just inferior to the right pulmonary artery (RPA). Note the location of the superior vena cava (SVC). Right: Color Doppler demonstrates the large left-to-right shunt through the sinus venosus ASD. C: Frontal subcostal image with slight rotation in a 10-year-old demonstrating anomalous connection of the right pulmonary vein (RPV) to the SVC just cephalad of the RA–SVC junction.

Scimitar Syndrome

Scimitar syndrome is a rare association of (a) anomalous connection of the right pulmonary vein(s) to the IVC, (b) right lung hypoplasia, and (c) aberrant arterial supply to the affected lobe of the right lung. It occurs in 1–3 of 100,000 live births, and the clinical presentation is quite variable. The lesion was first described by Cooper in 1836 and is termed “scimitar” because of the unique chest radiograph finding of the anomalous right pulmonary vein descending toward the IVC; it resembles a Turkish sword. Most (75%) patients with scimitar syndrome have normal intracardiac anatomy. Associated lesions that occur in the other 25% of patients include ASD, ventricular septal defect (VSD), patent ductus arteriosus (PDA), tetralogy of Fallot, and coarctation. Neonatal presentation is dramatic because these children have severe pulmonary hypertension and cyanosis. Surgical results for neonates with scimitar syndrome have been poor. More commonly, these patients present in adulthood with dyspnea, right-sided volume overload, or new-onset atrial arrhythmia. Subcostal images are uniquely suited for imaging scimitar syndrome. The anomalous right vein(s) can be demonstrated entering the IVC just below the IVC–RA junction. In scimitar syndrome, the heart may be shifted to the right due to hypoplasia of a portion of the right lung (Fig. 5.15).

Left Pulmonary Veins to the Innominate Vein

When the PAPVC involves the left lung, one or more left-sided pulmonary veins connect to the innominate vein via a left vertical vein (a remnant of the left anterior cardinal system) (Fig. 5.16). This is the most common form of isolated PAPVC. It is best visualized with TTE from the suprasternal window. During the examination, attention should be paid to the area on the left side of the aortic arch. Color flow and spectral Doppler will confirm that pulmonary venous flow is directed from the chest, cephalad into the innominate vein and subsequently to the SVC. In 2012, the Mayo Clinic described an adult with a left vertical vein that received anomalous left pulmonary veins and then connected to the innominate vein and the left atrium, creating a bidirectional shunt.

If the net shunt from the PAPVC is large, RA, RV, and MPA enlargement will be evident on TTE. RV enlargement will be associated with abnormal septal motion. In the case of anomalous left pulmonary vein(s), the innominate vein and SVC are enlarged. Enlargement of the SVC and innominate vein may be the first echocardiographic clue to the presence of PAPVC. Similarly, when left pulmonary vein(s) connect to the coronary sinus, the coronary sinus is enlarged on standard parasternal long-axis, short-axis, and apical views.

TEE Imaging Evaluation of Normal Pulmonary Venous Connections

Alternative imaging is indicated if surface echocardiography does not completely delineate the connections of all pulmonary veins to the LA and signs of right-sided volume overload are present. CT, MRI, or TEE imaging fulfills this role, and the choice of modality will be dictated by patient age, size, comorbidities, or the need for the study to be performed at the patient’s bedside. Due to the posterior location of the probe, TEE is well suited to allow direct visualization of the PV connections as they enter the LA. In 1997, Ammash and colleagues described techniques that can be used to visualize the normal PV connections. A consistent and systematic examination of normal pulmonary venous connections begins with positioning the tip of the TEE probe posterior to the LA. The right pulmonary veins are seen in the longitudinal plane by flexing a biplane TEE probe tip medially or rotating a multiplane array to approximately 70 to 80 degrees (a foreshortened short-axis view of the left ventricular outflow tract is obtained). One then rotates the probe to the patient’s right off the medial wall of the LA. A Y-appearing image of the normal right upper and lower pulmonary veins entering the LA is thus obtained (Fig. 5.17). The left pulmonary veins are imaged by (a) flexing a biplane TEE tip laterally or rotating a multiplane array to approximately 110 to 120 degrees (a foreshortened long-axis view of the left ventricular outflow tract is obtained) and (b) rotating the probe to the patient’s left off the free wall of the LA. A Y-shaped appearing image of the normal left upper and lower pulmonary veins entering the LA is thus obtained. The normal pulmonary venous connections can also be visualized in short-axis views at the base of the heart using the transverse plane of a biplane probe or 0 or 45 degrees of a multiplane probe. The left upper pulmonary vein is seen adjacent to the left atrial appendage by rotating the probe to the patient’s left. The left lower pulmonary vein is imaged by advancing the probe into the esophagus or with more retroflexion of the shaft. The right pulmonary veins are imaged by rotating the probe medially to the patient’s right and withdrawing to the level of the right pulmonary artery projected in long axis. The view of the right upper pulmonary vein is medial to the SVC (Fig. 5.18). By slowly advancing the probe into the esophagus, the right upper pulmonary vein is seen as it enters the medial aspect of the LA. By advancing the probe farther with mild rotation to the patient’s right, the right lower pulmonary vein is seen entering the LA. This technique accurately identifies the normal pulmonary vein connections into the LA but also demonstrates the normal size and shape of the SVC. If normal pulmonary vein connections are not visualized with these maneuvers or if the SVC appears dilated, then PAPVC must be suspected.

Figure 5.15. Scimitar syndrome. A: Diagram of scimitar syndrome. Anomalous connection of right pulmonary vein(s) to the inferior vena cava (IVC), also associated with right lower lobe hypoplasia and aberrant arterial supply to the right lower lobe. B: Subcostal frontal image demonstrating a large pulmonary vein from the right lung (asterisk) entering the IVC just below the right atrium (RA)–IVC junction. C: Color Doppler image from the same projection as B demonstrating flow (red) from the right lung toward the IVC. D: Computed tomography in same patient with scimitar syndrome demonstrating a large anomalous right pulmonary vein (asterisk) that enters the IVC just below the RA–IVC junction. E: In another patient with scimitar syndrome, an anomalous right pulmonary vein has flow toward the liver (red) as it enters the intrahepatic portion of the IVC. F: Spectral Doppler flow in the same patient depicted in E, confirming that a pulmonary venous flow pattern is demonstrated below the diaphragm.

Figure 5.16. Left upper pulmonary vein connection to the innominate vein. A: Suprasternal long-axis view demonstrating a left vertical vein (VV) connecting to the innominate vein (IV). This VV connected to the left upper pulmonary vein (LUPV). B: Color Doppler image from the same window as in A demonstrating cephalad flow (red) of the VV connecting to the IV. C: Magnetic resonance angiogram demonstrating connection of the LUPV to a VV, which then connects to the IV. D: Angiogram demonstrating anomalous connection of the LUPV to a VV, which then connects to the IV.

Figure 5.17. Transesophageal echocardiographic (TEE) views. Top left: Normal right pulmonary venous connections are most consistently imaged from the transesophageal approach by orienting the array to approximately 70 degrees or medial flexion of the scope tip and then rotating the probe rightward (medially). The right upper (RU) and right lower (RL) pulmonary veins form a typical Y configuration as they enter the left atrium. Top right: Normal left pulmonary venous connections are most consistently imaged from the TEE approach by orienting the array to approximately 110 degrees or lateral flexion of the scope tip and then rotating the shaft leftward (laterally). The left upper (LU) and left lower (LL) pulmonary veins form a typical Y configuration as they enter the left atrium. (From Ammash NM, Seward JB, Warnes CA, et al. Partial anomalous pulmonary venous connection: diagnosis by transesophageal echocardiography. J Am Coll Cardiol. 1997; 29:1351–1358.)

Figure 5.18. TEE imaging of the right upper pulmonary vein. With the transesophageal array in the horizontal orientation (0 degrees) and withdrawn to the level of the right pulmonary artery (RPA), the RPA is visualized in its long axis. Anterior to the RPA are three ovoid-appearing vessels, and farthest to the patient’s right is the right upper pulmonary vein (RUPV) lying immediately adjacent to the superior vena cava (SVC). The ascending aorta (Ao) is leftward from the SVC and medial to the main pulmonary artery (MPA). (From Ammash NM, Seward JB, Warnes CA, et al. Partial anomalous pulmonary venous connection: diagnosis by transesophageal echocardiography. J Am Coll Cardiol. 1997; 29:1351–1358.)

TEE Evaluation of Partial Anomalous Pulmonary Venous Connections

Anomalous connection of the right pulmonary vein(s) to the SVC can be visualized by using a short-axis view of the SVC at the level of the right pulmonary artery. The right upper pulmonary vein enters the free wall of the SVC, resulting in a teardrop appearance to the normally round SVC (Figs. 5.19 and 5.20). Connections to the RA–SVC junction and the free wall of the RA are best visualized by slowly advancing the probe into the esophagus while in the same short-axis plane. Color Doppler will help identify the anomalous pulmonary vein flow. When the anomalous connection of the right pulmonary vein is visualized entering the SVC, then attention should be redirected to the sinus venosus defect. The longitudinal scanning plane of a biplane TEE probe or the 90-degree angle on a multiplane probe can be used to carefully visualize the atrial septum. If the left pulmonary vein cannot be easily visualized entering the LA, then PAPVC should be suspected. Instead of entering the LA, the left pulmonary veins typically enter a vertical vein lateral to the LA (Fig. 5.21). Rightward rotation of the probe will result in a long-axis view of the SVC that is dilated with this defect. Finally, anomalous connection of left pulmonary veins to the coronary sinus should be suspected when the coronary sinus is dilated for no other obvious reason. This can be visualized in the longitudinal plane by identifying the dilated coronary sinus and rotating the probe to the patient’s left. This will demonstrate one or more left pulmonary veins connecting to the coronary sinus.

Figure 5.19. Transesophageal echocardiographic image in short axis at the cardiac base demonstrating anomalous connection of the right upper pulmonary vein (RUPV) to the superior vena cava (SVC). The conjoined structures form a “teardrop” appearance (arrow). RPA, right pulmonary artery.

Figure 5.20. Color Doppler of the same image in Figure 5.19 demonstrating flow (red) from the right upper pulmonary vein (RUPV) to the superior vena cava (SVC).

TEE imaging confidently visualizes the normal pulmonary vein connections and detects the most common forms of PAPVC. Stumper et al. (1991) demonstrated all pulmonary venous connections in 91% of patients studied. But Sutherland (1989) reported that defining normal pulmonary veins by TEE was more variable. In that study, the detection rate was 100% for the left upper pulmonary vein, 62% for the left lower pulmonary vein, 90% for the right upper pulmonary vein, and 23% for the right lower pulmonary vein. Conversely, in a 1997 Mayo Clinic study, 45 patients (age 2 to 75 years) with PAPVC had a TEE. Sixty-six anomalous pulmonary venous connections were detected in 43 patients. In the other two patients, TEE was suggestive but not diagnostic of PAPVC. Right-sided anomalous pulmonary veins were identified in 35 patients (81%), left-sided in 7 patients (16%), and bilateral in 1 patient (2%). There was a single anomalous pulmonary vein in 23 patients (53%) and multiple anomalous veins in the other 47%. The site of anomalous connection was SVC in 59% of patients, RA–SVC junction in 9%, RA in 12%, IVC in 1 patient, and coronary sinus in 2 patients. A sinus venosus defect was the most common associated anomaly, followed by secundum ASD or PFO. PAPVC was confirmed at the time of surgery in all patients, including the two patients whose TEE was only suggestive of PAPVC. With the current instrumentation and techniques described earlier in this chapter, the identification of the normal pulmonary venous connections with TEE imaging should be expected. PAPVC should always be considered as a potential cause for unexplained right ventricular volume overload.

Figure 5.21. Left pulmonary veins (arrows) connecting to a left-sided vertical vein (VV) illustrated in this short-axis transesophageal echocardiographic view. In this adult patient, the vertical vein passes anterior to the left pulmonary artery (LPA) and is unobstructed. The patient may have presented earlier in life if the course of the vertical vein was posterior to the LPA, thereby entrapping the vessel in a “vascular vise.”

Postoperative Echocardiography in PAPVC

Surgical repair of PAPVC is indicated in the presence of symptoms of dyspnea, fatigue, or exercise intolerance. Additional indications for intervention include: right-sided volume overload, atrial arrhythmias, pulmonary hypertension, or right heart failure. Anomalous right upper pulmonary veins currently are repaired with the Warden procedure, whereby the anomalous veins are channeled into the LA using the floor of the SVC and a pericardial patch. This pathway is constructed through an existing or surgically created ASD, thereby allowing the right-sided pulmonary veins to drain into the LA (Fig. 5.22). If the surgically constructed baffle is large and obstructs the SVC, then the SVC could also be enlarged using a pericardial patch. Alternatively, the SVC could be transected above the baffle and connected to the right atrial appendage. Long-term complications of surgical repair of anomalous right-sided pulmonary veins include SVC obstruction, baffle leak or stenosis, and atrial arrhythmias (especially if present preoperatively and in older patients). Left-sided PAPVC may be repaired through a left thoracotomy. The vertical vein draining the anomalous left-sided vein(s) is transected and connected to the left atrial appendage. The proximal end of the vertical vein is then closed. The result of surgical repair is confirmed with intraoperative TEE.

Figure 5.22. Zoomed four-chamber image of a surgically created baffle (arrow) after a Warden operation. This enables the anomalous right pulmonary veins to drain to the left atrium (LA).

Periodic surveillance with TTE imaging is needed to ensure the adequacy of repair and the absence of long-term complications. Meticulous postoperative scans in these patients need to include evaluation of SVC flow by color and spectral Doppler, 2D demonstration of the pulmonary vein pathway entering the LA, and interrogation of the atrial septum. Majdalani and colleagues described a 20-year experience with surgical repair of isolated PAPVC in 43 patients age 20–73 years old. During short-term follow-up (mean 2.7 years), 19 of 28 patients (68%) had reduction in RV size and 7 patients had reduction in pulmonary artery pressure.

ANOMALIES OF THE SYSTEMIC VEINS

Introduction

Isolated anomalies of the systemic venous connections are rare. The most common isolated lesion is a persistent left SVC that enters the RA via the coronary sinus. This isolated anomaly creates no physiologic derangement and may be considered a variant from normal. The incidence of a persistent left SVC in the general population is less than 0.5%. It becomes important only if placement of a central venous catheter or pacemaker lead becomes necessary. In patients with CHD, the occurrence of a left SVC is higher and may be observed in 10% to 20% of patients with tetralogy of Fallot and AV septal defects. A left SVC occurs due to failure of regression of the left anterior cardinal and common cardinal veins.

The vast majority of patients with complex CHD and heterotaxy syndromes have systemic venous anomalies. Bilateral SVCs are common in patients with heterotaxy syndromes (asplenia, .70%; polysplenia, 50%). Rarely, a left SVC may directly enter the LA; in these cases, the coronary sinus may be partially or completely unroofed. Abnormalities of the coronary sinus are common in patients with heterotaxy syndromes. Very rarely, the right SVC connects to the LA, resulting in cyanosis. If the left SVC is large, then usually there is a diminutive or absent “bridging” or innominate vein connecting the right and left SVCs (Fig. 5.23). Conversely, if the innominate vein is of normal caliber, then a left SVC usually is small. Knowledge of the connections of the systemic veins to the heart is important in patients with complex heart disease when considering vascular access for cardiac catheterization and cannulation in the operating room. Patients with single-ventricle physiology requiring a cavopulmonary connection may be at increased risk of thrombosis if bilateral SVCs are present, particularly if the SVCs are discrepant in size. As with the discussion of pulmonary venous anomalies, the reader is referred to the excellent review by Geva and van Praagh (2008) of the embryology and anatomy of the systemic venous anomalies, entitled “Abnormal Systemic Venous Connections.”

An interrupted IVC is another example of a systemic venous anomaly usually encountered in patients with complex CHD and heterotaxy syndromes. It occurs in less than 0.5% of the general population, but more than 75% of patients with polysplenia have an interrupted IVC. An interrupted IVC results from failure of the right subcardinal and vitelline veins to merge, causing the right supracardinal vein to dilate. When the IVC is interrupted, no intrahepatic portion exists. The hepatic veins usually connect independently to the right-sided atrium. Abnormalities of hepatic venous connections to the heart may occur in up to 25% of patients with heterotaxy syndromes. When an interrupted IVC occurs, the abdominal systemic venous return travels cephalad via the azygous vein. The azygous vein connects the IVC drainage above the level of the kidneys to the right SVC. Its course at the diaphragm is posterior to the peritoneal reflection and posterior to the aorta. In the thorax, the azygous vein passes through the diaphragm behind the heart and then arches over the right bronchus and right pulmonary artery to join the posterior aspect of the SVC. In cases of bilateral SVCs, bilateral azygous veins may also be present. The left-sided azygous vein is sometimes referred to by the misnomer “hemiazygous vein.” The presence of an interrupted IVC and azygous “continuation” is important in patients with single-ventricle physiology when contemplating a Fontan operation. In these patients, creation of the cavopulmonary connection nearly completes the Fontan pathway with the exclusion of only the hepatic venous flow, which connects to the atrium. Hepatic venous flow can be routed via a separate tube to the pulmonary artery to complete the Fontan circuit.

Figure 5.23. Pathologic specimen demonstrating right (RSVC) and left (LSVC) superior venae cavae with no obvious bridging vein.

The os of the coronary sinus, when present, is a useful anatomic landmark to identify the morphologic RA. The coronary sinus is involved with many of the systemic and pulmonary venous abnormalities discussed in this chapter. Sometimes referred to as the “forgotten systemic vein,” the coronary sinus serves to drain the coronary veins to the RA. Its course typically is in the posterior left atrioventricular groove. An unroofed coronary sinus has been discussed elsewhere in this textbook and serves as a rare form of an atrial level shunt. An unroofed coronary sinus usually has an associated left SVC. An exceedingly rare anomaly is atresia of the os of the coronary sinus. In this lesion, coronary venous blood may drain to the LA if the coronary sinus is unroofed or via a left SVC to the innominate vein. The coronary sinus may be dilated in several situations—lesions in which RA pressure is elevated (tricuspid stenosis/atresia), eccentric tricuspid regurgitation that is directed into the os of the coronary sinus, anomalies of systemic (persistent left SVC) or pulmonary (cardiac form of TAPVC) venous connections, and lesions in which coronary blood flow is increased. The importance of the anatomic location of the os and course of the coronary sinus has increased as cardiac resynchronization therapy with biventricular pacing becomes more widely used in patients with CHD.

Echocardiographic Assessment of Systemic Venous Anomalies

Left SVC to Coronary Sinus

The parasternal long-axis view readily demonstrates a dilated coronary sinus that may be the first clue to the presence of a persistent left SVC connecting to the RA (Fig. 5.24A). The parasternal short-axis view at the level of the pulmonary artery bifurcation demonstrates the anterior course of the left SVC over the LPA (Fig. 5.24B). Further clockwise rotation will demonstrate the “long axis” of the left SVC as it courses into the coronary sinus (Fig. 5.24B). Subcostal scans demonstrate the os of the coronary sinus and can be used to evaluate the roof of the coronary sinus. TEE imaging, especially in the operating room, is useful to alert the surgeon to the presence of a left SVC and the status of the coronary sinus (Fig. 5.25). Color Doppler assessment from the suprasternal notch window with leftward angulation may demonstrate a blue flow indicative of flow away from the innominate vein into the left SVC as it courses toward the coronary sinus. This is in contradistinction to a levoatriocardinal vein, referred to earlier in this chapter as a “left vertical vein.” A levoatriocardinal vein may course anterior or posterior to the LPA and may become obstructed as it passes between the bronchus and pulmonary artery. When imaging from the suprasternal notch, color Doppler flow in a levoatriocardinal vein or left vertical vein will be red since anomalous pulmonary venous flow is connecting to the innominate vein, unless there is still a connection to the coronary sinus.

Interrupted IVC with Azygous Continuation

The lack of an intrahepatic IVC when scanning in the subcostal plane is the first clue to probable interruption of the IVC and presence of a large azygous vein that connects the suprarenal systemic venous return to the SVC. Sagittal images of the abdomen will fail to demonstrate an IVC within the hepatic mass, and a large venous structure may be visualized posterior to the peritoneal reflection. This is the azygous vein, and typically it lies near the midline and posterior to the aorta. The echocardiographer should be suspicious of an azygous vein if color Doppler demonstrates a venous flow in a cephalad direction posterior to the pulsatile abdominal aorta. Once identified, the azygous can be followed along its entire course above the diaphragm as it arches in a posterior to anterior direction over the right pulmonary artery. This can best be viewed in the subcostal sagittal plane when one visualizes the “bicaval” view (Fig. 5.26).

Retroaortic Innominate Vein

This is a rare anomaly of the innominate vein where it courses posterior to the ascending aorta. It can be identified from the suprasternal long-axis view during assessment of the ascending aorta. Normally, only one vessel (the right pulmonary artery) is visualized posterior to the ascending aorta. If a second vessel is present beneath the ascending aorta, one should be alerted to the presence of a retroaortic innominate vein (Fig. 5.27). In this situation, the innominate vein–SVC connection lies just cephalad of the RA–SVC junction. Retroaortic innominate veins may occur in up to 1% of patients with CHD, most commonly in conotruncal lesions. The location of the innominate vein–SVC junction may be of surgical importance, especially during creation of cavopulmonary connections.

Figure 5.24. Parasternal long-axis and short-axis views. A: Parasternal long-axis projection demonstrating a dilated coronary sinus (CS). B: arasternal short-axis images in the same patient. Right: Note the anterior location of the left superior vena cava (SVC) (asterisk) as it is viewed in short axis anterior to the left pulmonary artery (PA). Left: With clockwise rotation, one can develop the length of the left SVC (asterisk) as it connects to the CS.

Figure 5.25. Transesophageal echocardiographic images of a left superior vena cava (SVC) entering the coronary sinus. Left: The left SVC enters the coronary sinus and is apparent posterior to the left atrial appendage (LAA) and anterior to the left upper pulmonary vein (LUPV). Ao, aorta; RVO, right ventricular outflow tract. Right: Color Doppler demonstrating flow (red) in the left SVC traveling posteriorly into the coronary sinus. Also noted is the posteriorly directed flow in the LUPV connecting normally to the LA.

Figure 5.26. Subcostal sagittal plane views. A: Cross-sectional image of the abdomen in patient with polysplenia and situs inversus demonstrating an azygous vein (Az vn) positioned posterior to the aorta (Ao) and the peritoneal reflection. No intrahepatic inferior vena cava (IVC) is present. B: High right parasternal images in this patient with pulmonary atresia demonstrating that the azygous vein (Az V) arches from posterior to anterior around a diminutive right pulmonary artery (PA) to enter the posterior aspect of the superior vena cava (SVC) just above the right atrium (RA)–SVC junction.

Figure 5.27. In these suprasternal short-axis images, a large retroaortic innominate vein (RAIV) is identified coursing posterior to the ascending aorta (Ao) joining the superior vena cava (SVC) (asterisks).

Imaging the Coronary Sinus

The coronary sinus, in the normal heart, can be readily assessed in the subcostal frontal (4-chamber) view. Although diminutive in the normal heart, the coronary sinus can be identified in the parasternal long-axis projection in the left atrioventricular groove just anterior to the echogenic pericardial strip. It should not be confused with the descending thoracic aorta, which lies posterior to the pericardial strip (Fig. 5.28). In the parasternal long-axis projection, gradually scanning toward the tricuspid inflow view will provide a smooth assessment of the roof of the coronary sinus and the entrance to the RA (Fig. 5.29). The course of a left SVC into the coronary sinus can be assessed with modified parasternal views with posterior angulation (Fig. 5.30A and Video 5.1). The coronary sinus can also be identified in the apical four-chamber projection by scanning posteriorly. Once the leaflets of the mitral valve are not visualized, the posterior left atrioventricular groove becomes apparent and the course of the coronary sinus can be visualized. TEE can also adequately visualize the coronary sinus when the probe is retroflexed in the four-chamber projection, providing a view of the left posterior atrioventricular groove. Saline contrast injection in a left arm vein can assist in identifying the connection of a left SVC to the coronary sinus and prompt filling of the LA and LV (Fig. 5.30B).

Figure 5.28. Parasternal long-axis image demonstrating a normal descending thoracic aorta (Dao) located posterior to the pericardial strip. This should not be confused with the coronary sinus or circumflex coronary artery (white arrow) that travels in the left atrioventricular groove.

Figure 5.29. Parasternal tricuspid inflow view demonstrating an intact roof of the coronary sinus (black arrow). This view is particularly helpful if an unroofed coronary sinus or left superior vena cava (SVC) connecting to a coronary sinus is suspected.

Figure 5.30. Left SVC to coronary sinus and saline contrast injection. A: Modified parasternal long-axis image of the course (yellow arrows) of a left SVC connecting to an unroofed coronary sinus. Also seen in Video 5.1. B: Injection of saline contrast in the left antecubital vein demonstrates prompt filling of the entire left heart.

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Questions

1.What is the most common form of total anomalous pulmonary venous connection (TAPVC)?

A.Supracardiac

B.Cardiac

C.Infracardiac

D.Mixed

2.The chest radiograph description of a “snowman” sign is associated with which of the following forms of TAPVC?

A.Supracardiac

B.Cardiac

C.Infracardiac

D.Mixed

3.Which of the following forms of TAPVC is associated with a vascular “vise”?

A.Supracardiac

B.Cardiac

C.Coronary sinus

D.Mixed

4.The embryologic origin of infracardiac TAPVC is related to failure of involution of which of the following connections?

A.Left-anterior cardinal vein

B.Right-anterior cardinal vein

C.Umbilicovitelline system

D.Ductus venous

5.What is the most common site of obstruction in infracardiac TAPVC?

A.Anterior cardinal vein

B.Ductus venosus

C.Portal vein

D.Inferior vena cava

6.In which of the following situations would a bridging innominate vein be absent?

A.Situs inversus with a left superior vena cava (LSVC)

B.Situs solitus with a right superior vena cava

C.Bilateral superior vena cavae with a large LSVC entering the coronary sinus

D.Interrupted IVC with azygous continuation to a right SVC

7.Which of the following is LEAST likely to cause dilation of the coronary sinus?

A.Left superior vena cava (LSVC)

B.Sinus venosus ASD

C.Unroofed coronary sinus

D.Elevated right atrial pressure

8.What is the most common form of partial anomalous pulmonary venous connection (PAPVC)?

A.Left-lower vein connected to a vertical vein

B.Azygous vein connected to the right SVC

C.Right-upper pulmonary vein to the SVC

D.Right-lower pulmonary vein to the IVC

9.Scimitar syndrome may have all of the following EXCEPT:

A.Anomalous connection of the right-lower pulmonary vein to the IVC

B.Aberrant arterial supply to the right-lower lobe

C.Sequestered right-lower lobe

D.Anomalous right coronary artery

10.In a patient with Scimitar syndrome, which of the following is most common?

A.ASD

B.Tetralogy of Fallot

C.Coarctation of the aorta

D.Normal intracardiac anatomy

Answers

1.Answer: A. Supracardiac is the most common type of TAPVC. Obstruction of either the supracardiac or infracardiac TAPVC constitutes a neonatal surgical emergency. The mixed form does not have a true pulmonary venous confluence.

2.Answer: A. In the supracardiac form of TAPVC, the pulmonary venous confluence usually connects to a left-sided vertical vein that travels cephalad towards the innominate vein, creating the “snowman” shadow on the chest radiograph.

3.Answer: A. The vascular vise occurs when the left vertical vein passes between the left pulmonary artery and the left mainstem bronchus. Obstruction of the vein occurs at this point and usually requires immediate surgery.

4.Answer: C. Failure of involution of the umbilicovitelline system will cause infracardiac connection of the pulmonary venous confluence. The left-anterior cardinal vein is related to a left-vertical vein in supracardiac TAPVC.

5.Answer: C. The portal vein is the most common site of obstruction for infracardiac TAPVC. Connections to the ductus venosus, hepatic veins or IVC have also been observed. Infracardiac TAPVC with obstruction usually requires emergent surgery within hours after birth.

6.Answer: C. When bilateral SVCs are present, their bridging vein is usually diminutive. One would expect a normal innominate (bridging) vein in the other situations.

7.Answer: B. Coronary sinus (CS) dilation can be caused by connection of a LSVC, anomalous pulmonary venous connection to the CS, elevated RA pressure, and/or eccentric tricuspid regurgitation. The sinus venosus “ASD” is actually not a defect in the atrial septum, but instead a defect between the SVC and the right upper pulmonary vein. It is not related to the CS.

8.Answer: C. Anomalous connection of the right-upper and right-middle pulmonary veins to the SVC or RA is observed with sinus venosus defects, and is the most common form of PAPVC.

9.Answer: D. Answers A, B, and C are typical features of scimitar syndrome, although many adult patients with Scimitar syndrome do not have aberrant arterial supply or sequestered lobes.

10.Answer: D. Only 25% of patients with Scimitar syndrome have associated lesions. Most have normal intracardiac anatomy. The other lesions listed have been reported in patients with Scimitar.