Atrial septal defects (ASDs) account for approximately 7% to 10% of all congenital heart disease. Secundum defects, which comprise 60% to 75% of all ASDs, are the most common. Two-dimensional, Doppler, and color Doppler echocardiography play a key role in confirmation of the clinical diagnosis of an ASD, providing definitive evaluation of abnormalities of atrial septation. An ASD may exist in isolation or in association with other congenital cardiac abnormalities. It is important to recognize abnormalities of atrial septation, as these defects may affect clinical management, such as whether catheter-based or surgical treatment is preferred. Cor triatriatum, a very rare type of septation abnormality, will also be reviewed. Primum ASD, which is within the spectrum of atrioventricular septal defects, will be considered in a separate chapter.
ATRIAL SEPTAL ANATOMY AND EMBRYOLOGY
A defect in the atrial septum results in a direct communication between the left atrium (LA) and right atrium (RA). To characterize the location of ASDs, an understanding of septal anatomy is critical. An ASD is typically classified by its location in relationship to the fossa ovalis (Fig. 6.1). During embryologic development, the primitive atrium undergoes a complex septation process. The septum primum extends inferiorly from the middle of the atrium toward the region of the endocardial cushions, initially leaving an opening called the ostium primum. The inferior portion of the septum primum subsequently fuses with the developing endocardial cushions to close the inferiorly located ostium primum (see Fig. 6.1A–B). Tissue reabsorption (or programmed cell death) in the middle of septum primum leads to a second, central opening, or ostium secundum. Concurrently, development of the septum secundum occurs, and once joined with the endocardial cushions, the inferior portions of the two atria are separated. The remaining defect in septum secundum is the foramen ovale, which allows flow from the fetal RA to LA during gestation. Once birth occurs, fusion of these two septa should occur, functionally closing the foramen ovale; however, probe patency is present in approximately 25% to 30% of the population. Secundum ASDs, typically occurring in the central or secundum portion of the atrial septum, actually result from a true deficiency in the septum primum (see Fig. 6.1D).
Both venae cavae (superior and inferior) and the coronary sinus (CS) enter the more posterior smooth-walled portion of the RA. Defects within this superior/posterior portion of the atrial septum are termed sinus venosus defects (see Fig. 6.1D) and result from an abnormality of right pulmonary vein incorporation into the developing atrium. These defects typically occur in conjunction with an abnormality of pulmonary venous return from the right lung. Geva and Van Praagh propose that sinus venosus ASD is not a true ASD but an unroofing of the right pulmonary vein into the superior vena cava (SVC) with the interatrial communication being the left atrial orifice of the unroofed pulmonary veins.
A CS defect, or unroofed CS syndrome, results from an abnormality in the development of the left atrioventricular fold. In this spectrum of abnormalities, complete or partial unroofing of the CS, with direct communication to the LA, is present and is uniformly associated with a left SVC (see Fig. 6.1D).
Cor triatriatum sinister, another very rare form of abnormal atrial septation, occurs within the LA. Cor triatriatum may result from abnormal incorporation of the common pulmonary vein into the LA, causing obstruction between the pulmonary vein confluence and the LA; however, not all variants of this rare lesion are embryologically consistent with this theory.
ATRIAL SEPTAL DEFECT
Clinical presentation of the patient with an ASD varies with patient age, size of the defect, and the presence of associated lesions. In the infant with an isolated ASD, presentation with symptomatic pulmonary overcirculation is unusual, as right ventricular (RV) compliance is low and atrial shunting may be minimal early in life. An ASD may be found as part of complete evaluation of the infant with other cardiac anomalies. As right ventricular (RV) compliance improves during infancy and early childhood, left-to-right shunting at the atrial level typically increases. The child or adolescent with a hemodynamically significant ASD usually presents with a cardiac murmur or, less commonly, with symptoms of exercise intolerance or fatigue. The physical examination characteristically reveals a hyperdynamic RV impulse in a patient with a large shunt. A systolic ejection murmur is heard over the left sternal border in association with a widely fixed split second heart sound. A diastolic flow rumble over the tricuspid valve inflow area is present with a significant shunt at the atrial level due to the large volume of blood returning through the tricuspid valve. The chest radiograph may show cardiomegaly with increased pulmonary vascular markings in addition to prominence of the main pulmonary artery segment and central pulmonary arteries.
Figure 6.1. Atrial septal anatomy. A: Right-sided, two-chamber view of right atrium (RA) and right ventricle (RV). The interatrial septum (IAS) is outlined (dotted line); the superior limbus and inferior limbus surround the valve of the fossa ovalis. The atrioventricular septum (AVS) is shown just above the tricuspid valve. B: Left-sided, two-chamber view of left atrium with IAS depicted within the dotted line. C: Four-chamber view of the crux of the heart, demonstrating IAS (between the RA and LA) with superior limbus, inferior limbus, and valve of the fossa ovalis. The AVS lies between the RA and the left ventricle (LV). D: Diagrammatic representation of the different types of atrial septal defects (ASDs), numbered in decreasing frequency according to rates of occurrence: secundum ASD (1), primum ASD (2), sinus venosus ASD (3), coronary sinus ASD (4). CS, coronary sinus; IVC, inferior vena cava; IVS, interventricular septum; MV, mitral valve; PT, pulmonary trunk; RAA, right atrial appendage; SVC, superior vena cava; TV, tricuspid valve. (Reprinted by permission of Mayo Foundation.)
Atrial level shunting tends to increase with age. The older patient may present with more significant symptoms of exercise intolerance or fatigue and very rarely with overt right heart failure. Atrial arrhythmias are uncommon before adulthood but may persist following late repair unless a surgical arrhythmia procedure is performed concurrently. Pulmonary hypertension or pulmonary vascular obstructive disease is uncommon in the setting of an isolated ASD but must be evaluated carefully before treatment recommendations can be made.
Communication between the LA and the RA allows oxygenated pulmonary venous blood to enter the RA via the defect in the atrial septum. Left atrial pressure is typically higher than right atrial pressure through most of the cardiac cycle, so the predominant shunt is left to right. A very transient right-to-left shunt is commonly observed due to variability in atrial compliance. A patent foramen ovale (PFO) may allow right-to-left shunting and the potential for paradoxical embolism to the systemic circulation. Most commonly in the setting of an ASD, left-to-right shunting at the atrial level produces right-sided volume overload, causing progressive RA and RV enlargement and pulmonary overcirculation. In the patient with pulmonary vascular disease or RV outflow obstruction, right-to-left shunting at the atrial level may be significant as RV compliance worsens over time.
A patient with a CS ASD and connection of the left SVC to the roof of the LA may have variable degrees of cyanosis due to mixing of systemic venous return with the oxygenated pulmonary venous return. The amount of desaturation is proportional to the amount of systemic venous blood carried by the left SVC.
A small ASD will typically undergo spontaneous closure (complete or nearly complete) and should not require treatment or produce long-term complications. A moderate (6 to 12 mm) or large (greater than 12 mm) ASD may not cause significant symptoms or complications early in life, but as left ventricular compliance decreases over time the volume of intracardiac shunt will steadily increase. It is unlikely that a defect larger than 8 mm will undergo spontaneous closure; in fact, the anatomic size of a moderate or large ASD may increase over time. Also, chronic RV volume overload may produce tricuspid annular dilation, resulting in progressive tricuspid valve regurgitation. Longstanding right atrial dilation contributes to an increased risk of atrial arrhythmias. Although atrial flutter and atrial fibrillation are uncommon in childhood, the prevalence increases with age in a patient with untreated or undiagnosed ASD. Arrhythmias may persist after repair, particularly with repair at an older age or in the setting of elevated pulmonary artery pressure or resistance. Natural history studies suggest that repair of a hemodynamically significant ASD before age 25 years should allow a normal life expectancy.
Pulmonary hypertension and pulmonary vascular obstructive disease in association with ASD are uncommon, occurring in a small percentage of patients. Additional complications of right-to-left shunting may include paradoxical emboli and risk of stroke. Less commonly seen in the setting of unroofed CS is cerebral embolization and risk of brain abscess.
EVALUATION OF ATRIAL SEPTAL DEFECT: OVERVIEW
Right-sided chamber enlargement is the hallmark of an atrial level shunt. When seen on echocardiographic imaging, this should prompt a comprehensive evaluation of the atrial septum and definition of pulmonary venous return.
Because the atrial septum is a complex three-dimensional structure, it must be imaged from multiple planes. Portions of the atrial septum may be quite thin and difficult to visualize; therefore, definitive imaging of the atrial septum with transthoracic echocardiography can be challenging, particularly in the older adolescent or adult. Orthogonal views are needed in order to resolve tissue rims. Diagnostic images are typically obtained with the imaging transducer perpendicular to the structures of interest, so as to not produce artificial dropout or the appearance of a defect where there is not an ASD. The echocardiographer needs to provide an assessment of defect location, size, and distance from surrounding cardiac structures. In addition, a complete assessment of potential associated cardiac abnormalities is indicated. Complete spectral Doppler and color Doppler assessment is important in evaluation of the primary defect as well as to provide hemodynamic evaluation, including estimation of RV systolic and pulmonary artery pressure and assessment of tricuspid regurgitation. Noninvasive shunt quantification is not typically performed.
The goals of imaging should be to provide definitive information for the clinician, to assess the hemodynamic significance of the defect(s), and to aid in planning for catheter-based intervention or surgical treatment. If image quality from the transthoracic approach is suboptimal and the echocardiographer suspects an atrial level shunt or abnormality of pulmonary venous return, then transesophageal echocardiography is warranted. In some cases, cardiac magnetic resonance imaging (MRI) may be needed to definitively evaluate abnormalities of pulmonary venous return, particularly if the abnormal connection is high in the superior vena cava.
Subcostal imaging is ideal for evaluation of the atrial septum when image quality is adequate. From this orientation, the transducer beam is relatively perpendicular to the atrial septum in both the four-chamber (coronal) and short-axis (sagittal) views, so that tissue structures can be resolved to be sure that artifactual dropout is not present. Key echo findings include the presence of true dropout in the atrial septum, and right-sided structural enlargement (RA, right ventricle, and pulmonary artery). The edges of the defect may produce additional reflections known as a “T-artifact,” allowing identification of defect rims.
Subcostal Four-Chamber (Coronal) Views
Four-chamber or coronal plane imaging provides images of the atrial septum along an anterior-to-posterior axis and is useful to identify the location and size of an ASD. Imaging is carried out with transducer sweeps from anterior to posterior, providing evaluation of the ASD in the long axis of the defect (Fig. 6.2A) (Video 6.1). The location of the defect in the septum and its relationship to the right-sided SVC and right upper pulmonary vein should be ascertained (Fig. 6.2B). Scanning anteriorly and superiorly provides evaluation of the atrial septum immediately behind the aorta. The posterior-inferior portion of the atrial septum can be evaluated by angling the transducer more posteriorly in the four-chamber plane, but artifactual dropout may occur. Short-axis imaging is preferred for evaluation of posterior and inferior rims. In the normal heart, the atrial septum should be seen inferiorly/posteriorly extending to the level of the atrioventricular valves.
The addition of color Doppler typically reveals a continuous left-to-right shunt (Fig. 6.2C), although a transient, brief amount of right-to-left shunting may occur with variations in respiratory cycle. Pulsed-wave Doppler at the level of the ASD will demonstrate low-velocity, phasic, left-to-right flow; very transient right-to-left flow may be detected. Lack of phasic flow or increased velocity with continuous flow suggests a significant gradient between the LA and RA caused by a restrictive defect (depending on the direction of flow).
Figure 6.2. Subcostal imaging of a moderate-sized secundum atrial septal defect (ASD). A: Subcostal coronal plane focused on biatrial view, showing dropout in mid-septum between the left atrium (LA) and right atrium (RA) consistent with moderate-sized secundum ASD. The rims of the defect in this plane appear well developed (single arrows, superior edge; double arrow, inferiorly). The right pulmonary artery (asterisk) can be seen just posterior to the superior vena cava (SVC). B: Slight anterior angulation of the transducer from the coronal view (shown in A) will bring into view the right upper pulmonary vein (large asterisk) entering the LA. C: Addition of color Doppler shows left-to-right shunt through the ASD (double arrow) and the right pulmonary vein flow to the LA (single arrow). D: Rotating the transducer approximately 90 degrees from coronal view provides a short-axis (sagittal) view, demonstrating the secundum ASD with adequate superior (near the SVC) and inferior/posterior rims (single arrows) for consideration of device closure. (Imaging note: Farther rightward movement of the transducer to achieve a bicaval view will show the entrance of the inferior vena cava into the RA anterior to the inferior rim.) LV, left ventricle; RV, right ventricle.
Subcostal Short-Axis (Sagittal) Views
Subcostal short-axis (SAX) imaging is obtained in an orthogonal imaging plane to the four-chamber (coronal) view, providing imaging in a superior-inferior axis (Fig. 6.2D and Video 6.2). Sweeping the transducer from right to left allows evaluation of the relationship of the right-sided SVC, pulmonary veins (particularly right), and the superior/inferior rims of an ASD. One must be careful to note the position of the Eustachian valve, which is located anteriorly at the entrance of the inferior vena cava to the RA; this should not be confused with a rim of the ASD. Short-axis imaging allows imaging of the anterior-superior and posterior-inferior atrial septum. In addition, excellent images of the right ventricle (RV), RV outflow tract (RVOT), and pulmonary valve can be obtained from the subcostal short-axis plane. Doppler interrogation can be performed to evaluate RVOT velocities to determine if a significant outflow tract gradient exists.
Parasternal Long-Axis View
Characteristic signs of RV enlargement, volume overload, and paradoxical septal motion are seen in the parasternal long-axis plane when there is a significant atrial level shunt (Fig. 6.3A). Mitral valve prolapse, seen in association with ASD, is best demonstrated in the long-axis plane. Angling the transducer inferiorly toward the tricuspid inflow view may demonstrate color flow across the atrial septum, although this view is often insufficient for visualization of an ASD. Color Doppler should also be used to evaluate tricuspid valve regurgitation, and, if present, pulsed-wave Doppler can be used to obtain an estimation of RV systolic pressure (RVSP).
Figure 6.3. A: Parasternal long-axis view with severe right ventricular (RV) enlargement due to a large secundum. B: Parasternal short-axis view demonstrating RV enlargement and diastolic flattening of the interventricular septum, consistent with RV volume overload. Ao, aorta; LA, left atrium; LV left ventricle.
Angling the transducer superiorly toward the left shoulder will demonstrate the RVOT, the pulmonary valve leaflets, and main pulmonary artery. Dilation of the main pulmonary artery is seen with significant atrial level shunting. The pulmonary valve leaflets should be examined for morphology and function. In the RVOT, pulsed-wave Doppler velocities as high as to 2.5 m/s may be seen with large atrial level shunts; velocities greater than 2.5 m/s suggest an additional component of valvular pulmonary stenosis. Doming or restricted motion of the pulmonary valve will be seen with valve stenosis and should be evaluated carefully with two-dimensional imaging for correlation with Doppler findings.
Figure 6.4. Parasternal short-axis view of large secundum atrial septal defect (ASD). A: Right atrial (RA) and right ventricular (RV) enlargement are consistent with atrial level shunting. RA is significantly more enlarged than the left atrium (LA). The diminutive anterior, retroaortic rim (single arrow) of the ASD is well visualized in this image. The posterior rim is well demonstrated in this view (double arrow), as it is not parallel to the imaging plane. Ao, aorta. B: The addition of color Doppler shows a large shunt from LA to RA consistent with the secundum ASD.
Parasternal Short-Axis View
Parasternal short-axis imaging is also very useful for evaluating RV volume overload and flattening or paradoxical motion of the interventricular septum (Fig. 6.3B). Diastolic flattening of the septum is common with volume overload; systolic flattening is seen with pressure overload. Doppler evaluation of tricuspid regurgitation, including assessment of RVSP, is important for comprehensive hemodynamic assessment and to rule out possible coexistent pulmonary hypertension. RA enlargement is also appreciated from this view. As the atrial septum is somewhat perpendicular to this plane of imaging, septal rims may be evaluated accurately (Fig. 6.4A and Video 6.3). Color Doppler will show left-to-right shunting from LA to RA in a typical secundum ASD (Fig. 6.4B). The RVOT, pulmonary valve, and main pulmonary artery are well seen from the SAX view. Anatomic evaluation of the infundibulum and pulmonary valve is also recommended to correlate with Doppler findings.
Figure 6.5. Apical four-chamber view shows moderate right atrial (RA) and right ventricular (RV) enlargement. There is a large secundum atrial septal defect (ASD) with well-developed superior rim and inferior rims (single arrows). (Imaging note: One must be careful to define the rims of tissue carefully, as they are typically more parallel to the plane of imaging from the apex and artificial dropout should be avoided.)
Apical Four-Chamber View
RA and RV enlargement can be easily seen from the apical four-chamber orientation (Fig. 6.5). One should use color Doppler to evaluate the degree of tricuspid regurgitation and pulsed-wave Doppler to provide an accurate estimation of RVSP (Fig. 6.6) [Video 6.4]. Associated mitral valve abnormalities can also be evaluated, taking care to rule out mitral valve stenosis that may accentuate an atrial level shunt due to elevation of left atrial pressure. Because the four-chamber imaging plane is parallel to the atrial septum, the suggestion of dropout in the thinner mid-portion of the atrial septum must be confirmed from additional views. The apical four-chamber view can be used for evaluation of the inferior-most portion of the atrial septum at the level of the crux of the heart.
Figure 6.6. Apical four-chamber images in a patient with pulmonary hypertension and moderate secundum atrial septal defect (ASD). A: Severe right atrial (RA) and right ventricular (RV) enlargement with right ventricular hypertrophy is seen. B: Left-to-right shunt is seen through the ASD (double arrows) with associated tricuspid valve regurgitation (single arrow). C: Quantitative hemodynamic assessment with tricuspid regurgitation velocity of 4 m/s predicting elevated RV systolic pressure (64 mm Hg plus RA pressure). LA, left atrium; LV, left ventricle.
Angling the transducer anteriorly from the four-chamber view brings the left ventricular outflow tract into view; further anterior angulation (or para-apical) provides another excellent view of the pulmonary valve and RVOT. Doppler determination of any important RVOT obstruction is important with respect to planning therapeutic catheterization or surgery.
Suprasternal Notch Views
The right and left branch pulmonary arteries are seen well from suprasternal notch imaging. In a short-axis or coronal plane, the LA can be visualized inferior to the right pulmonary artery. Sweeping the transducer from left to right should demonstrate all four pulmonary veins connecting to the LA (the “crab” view). Rotating the transducer 90 degrees to the long-axis plane is helpful to rule out an anomalous left upper pulmonary vein to a vertical vein. From this imaging plane, color Doppler flow coursing superiorly toward the transducer, entering the innominate vein, should alert the echocardiographer to the possibility of an anomalous left pulmonary vein.
High right parasternal imaging can provide an additional window to evaluate the SVC-RA junction and superior portion of the atrial septum. In some patients, this imaging plane may provide a “bi-caval” view and further assessment of the superior and inferior septal rims of a secundum defect optimally visualizes a high sinus venosus ASD.
In the patient with right-sided cardiac enlargement on transthoracic imaging but no identifiable ASD or abnormality of pulmonary venous return, a transesophageal echocardiogram (TEE) is indicated. TEE imaging of the atrial septum is usually of sufficient quality to demonstrate most defects; however, one must be attentive to the very inferior/posterior portion of the atrial septum, as proximity to the imaging probe may obscure visualization. Cardiac MRI may also be of benefit if the atrial septum is adequately visualized from TEE but the pulmonary venous connections cannot be resolved.
TWO-DIMENSIONAL ECHO ANATOMY AND IMAGING
Patent Foramen Ovale
A PFO is located immediately beneath the superior limbus and is typically a small defect. In the majority of neonates undergoing echocardiography, a small amount of left-to-right shunting is present through the PFO with color Doppler echocardiography. Spontaneous closure occurs in the majority of patients, although probe patency persists in approximately 25%. In the older patient with clinical evidence of paradoxical embolism, a small defect or larger redundant septal flap, along with a tunnel, may be seen. In such patients, TEE will usually be needed to document septal anatomy in detail, with injection of agitated saline through an intravenous line to confirm a right-to-left shunt if not seen on baseline color Doppler interrogation.
Secundum Atrial Septal Defect
A secundum ASD produces characteristic dropout in the central-most portion of the atrial septum. Most defects are relatively elliptical in shape. Assessment from multiple views is needed to fully evaluate the maximum ASD dimensions, septal rims, and relationship of the ASD to surrounding cardiac structures. With the widespread availability of transcatheter device closure of secundum ASD, the echocardiographer plays a critical role in assessment and patient selection for catheter-based therapy. One must also exclude the presence of fenestrations or aneurysmal septal tissue in association with a secundum ASD, although these often remain amenable to device closure. It is very important to rule out any defects that would require surgical attention (i.e., anomalies of pulmonary veins).
A typical secundum ASD is seen in the subcostal (coronal) four-chamber orientation (Fig. 6.7) and in the short-axis (sagittal) imaging plane as a central area of septal dropout within the atrial septum with surrounding rims of tissue present. From the subcostal four-chamber imaging plane, a rim of tissue should separate the SVC entrance to the RA and the right upper pulmonary venous entrance to the LA from the ASD. More inferiorly with leftward and posterior angulation toward the crux of the heart, there is typically a larger rim of tissue separating the atrial defect from the atrioventricular valves and CS. Angling anteriorly, the defect can be seen posterior to the aorta; however, the retroaortic rim of tissue will be seen more definitively in the parasternal short-axis view. Subcostal short-axis imaging shows the superior/anterior rim of the defect just beneath the SVC–RA junction. The normally connected right upper pulmonary vein is seen entering the LA posterior to this rim. One of the rims that may be most difficult to visualize adequately in patients with secundum ASD is the posterior/inferior rim. Parasternal short-axis images also often demonstrate this rim posteriorly. Subcostal short-axis imaging is often diagnostic when image quality is adequate (see Fig. 6.7C). It is important to remember that the Eustachian valve tissue, which may be prominent and often confused with an ASD septal rim, enters the RA anterior to the inferior vena cava (for an example of a complex ASD see Fig. 6.8).
Parasternal long-axis views do not typically show the ASD adequately, even when angling inferiorly toward the tricuspid inflow view. However, parasternal short-axis views are very useful for visualization of the anterior (retroaortic) and posterior septal rims. These views may also be helpful in patients with difficult subcostal windows before the consideration of TEE. An absent “retroaortic” rim may not prevent successful device closure if other adequate rims are present; however, an adequate posterior septal rim should be present. Complete absence of the posterior/superior rim will preclude successful device closure of a secundum ASD (see Fig. 6.8B) [Video 6.5].
Imaging of a secundum ASD from the apical four-chamber view shows the superior rim between the right upper pulmonary vein and SVC, and the inferior rim above the mitral and tricuspid valves (see Fig. 6.5). Total atrial septal length, as well as superior and inferior rims, should be measured from this view when considering device closure of a secundum ASD.
Figure 6.7. Subcostal imaging of a moderate-sized secundum atrial septal defect (ASD) amenable to catheter-based device closure. A: Adequate rims are seen in the subcostal coronal view (defect indicated by asterisks). B: Color Doppler with left-to-right shunt through the ASD. C: Corresponding subcostal sagittal view with measurements of superior rim (1.3 cm) and inferior-posterior rim (1.2 cm). The ASD in this plane measured 1.8 cm. LA, left atrium; RA, right atrium.
Sinus Venosus Defect with Partial Anomalous Pulmonary Venous Connection
A sinus venosus ASD is located in the superior/posterior region of the atrial septum and will be seen directly adjacent to the SVC without an intervening superior rim. Sinus venosus ASD is typically associated with anomalous drainage of the right upper and/or middle lobe pulmonary veins to the SVC–RA junction. The lower right pulmonary vein is rarely involved. Although the connection of the anomalous pulmonary vein(s) may be “high” in the SVC, their connection is not typically present above the entry of the azygous vein to the SVC. Subcostal imaging in the four-chamber plane can be used to visualize this defect, with angling of the transducer superiorly and anteriorly to bring in the atrial septum between the SVC and RA (Fig. 6.9A) (Video 6.6). One or two of the right pulmonary veins can be seen entering the SVC or superior portion of the RA from this imaging plane and must be identified (Fig. 6.9C, D). The entrance of the SVC may appear enlarged as a result and may even appear to “override” the defect into the LA, but the SVC remains normally connected to the RA.
In the subcostal short-axis plane, there is dropout of tissue immediately below the entrance of the SVC to the RA, and again there is absence of the superior rim (Fig. 6.9B) (Video 6.7). The entrance of an anomalous right pulmonary vein to the SVC–RA junction may also be seen from this sagittal imaging plane during sweeps from right to left. If the pulmonary veins are not easily identified in conjunction with the images showing a sinus venosus ASD (particularly in the older patient), then TEE or MRI/magnetic resonance angiography (MRA) may be necessary to completely define the pulmonary venous anatomy in preparation for surgery (as in the case of high connection near the level of the azygous vein).
TEE imaging in sinus venosus ASD shows dropout in the superior portion of the atrial septum immediately beneath the SVC entrance (Fig. 6.10). Withdrawing the probe to a more superior position in the mediastinum, the anomalous right pulmonary vein can be identified from a short-axis view by visualization of a key hole (or “teardrop”) sign where the pulmonary vein enters the cava; normally, the SVC would appear as a complete circle in this view (Fig. 6.11A) (Video 6.8). Color Doppler confirms the venous flow into the SVC from the anomalous pulmonary vein (Fig. 6.11B) (Video 6.9).
Coronary Sinus Atrial Septal Defect (Unroofed Coronary Sinus)
When there is a coronary sinus (CS) ASD, an enlarged CS ostium is seen and might be confused with a simple left-sided SVC to the CS. However, the right-sided cardiac structures will be enlarged because of the atrial level shunt. Parasternal long-axis views can be used to confirm an unroofed CS, as there is an absent rim of tissue between the floor of the LA and the CS (Fig. 6.12A–B) (Video 6.10). Color Doppler examination shows flow going away from the transducer, as the shunt is from the LA to the CS through the defect in the roof of the CS (Fig. 6.12C) (Video 6.11). A CS ASD is almost always associated with connection of the left SVC to the roof of the LA. It is important to identify the drainage of the left SVC for purposes of surgical intervention. As an adjunct to imaging, an agitated saline injection through an intravenous line in the left arm will demonstrate bubbles appearing initially in the LA and subsequently the RA. If the left SVC is missed or is allowed to remain anomalously connected to the LA following surgical repair of the CS ASD, the patient will have persistent cyanosis due to systemic venous return to the LA.
Figure 6.8. Subcostal sagittal images from a patient with a very large atrial septal defect (ASD) and associated anomalous connection of right pulmonary veins to the right atrium. A: There is no superior rim (double arrows pointing superiorly). A very prominent Eustachian valve (single arrow) is seen entering the right atrium (RA) anterior to the inferior vena cava (IVC). The posterior-inferior rim is seen near the IVC entrance (inferiorly directed double arrows). B: Further angulation of the transducer rightward in this sagittal plane demonstrates the right superior vena cava (yellow asterisk) entering the right atrium normally. However, there are absent superior and inferior/posterior rims in this part of the defect, seen only with careful sweeps of the transducer rightward (bordered by double arrows). The prominent Eustachian valve is seen anteriorly to hepatic vein return to the RA (single arrow). C:Leftward angulation of the transducer in the short sagittal does show the rim of the defect to be present (double arrow). A large Eustachian valve is seen again (single arrow). D:Rotating the transducer 90 degrees to a coronal plane shows the prominent Eustachian valve (single arrow) and the extent of the defect (double arrows). In this imaging plane, the superior rim appears to be absent and a right pulmonary vein (asterisk) is seen entering the right atrial aspect of the superior portion of the defect. (Imaging note: An ASD with absent rims and potential anomalous pulmonary venous return will require multiple imaging planes for confirmation of this cardiac anatomy. This type of defect is not suitable for device closure.) LA, left atrium.
Anomalous Pulmonary Venous Connection
One of the critical issues in evaluation of a patient with an ASD is a potential anomalous pulmonary venous connection. A sinus venosus ASD is usually associated with anomalous connection of the right upper/middle pulmonary veins to the SVC or right atrial junction. However, pulmonary vein anomalies can also be seen with secundum ASD and, if present, would be a contraindication to device closure of the ASD in the cardiac catheterization laboratory. Pulmonary veins may be difficult to visualize definitively with transthoracic echocardiography (TTE), especially in the older teenager or adult patient. Further imaging with TEE or cardiac MRI should be used for definitive documentation of all pulmonary vein connections when they cannot be defined by conventional TTE.
Figure 6.9. Subcostal imaging of sinus venosus atrial septal defect (ASD) (arrows). A: Coronal view showing superiorly located venosus defect adjacent to the superior vena cava (SVC) entry into the enlarged right atrium (RA). B: Sagittal view showing left atrium (LA) posteriorly and the superiorly located sinus venosus ASD in proximity to the SVC. Right pulmonary artery (RPA) is seen posterior to the SVC. C: In coronal view, transducer is angled slightly anterior to view obtained in A; the entry of the anomalous right upper and middle lobe pulmonary veins to the SVC can be seen (asterisk). D:Addition of color Doppler showing flow from anomalous right pulmonary veins (asterisk) entering the SVC. Ao, aorta; L, leftward; LV, left ventricle; P, posterior; RV, right ventricle; S, superior.
Pulmonary Valve Stenosis
Valvular pulmonary stenosis is identified by typical doming or thickening of the pulmonary valve leaflets, usually with restricted motion. Doppler velocities of up to 2.5 m/s can be seen with a significant left-to-right shunt at the atrial level, but velocities greater than this are more consistent with associated pulmonary valve stenosis. The pulmonary valve annulus and leaflets should be carefully evaluated with two-dimensional imaging. Accentuated post-stenotic dilation of the main pulmonary artery may be seen in ASD with pulmonary valve stenosis. Catheter-based treatment is possible for both defects and can be planned accordingly.
Annular dilation from longstanding atrial level shunting may result in progressive tricuspid regurgitation. Valve coaptation may be adversely affected. Assessment of the degree of tricuspid regurgitation is important in planning for treatment, as the patient with significant tricuspid regurgitation may require surgery rather than catheter-based intervention, if concomitant tricuspid valve repair is indicated.
Figure 6.10. Transesophageal echocardiographic (TEE) images of sinus venosus atrial septal defect (ASD) associated with anomalous connection of right upper pulmonary vein to superior vena cava (SVC). A: Longitudinal plane imaging in region of inferior edge of superior limbus (asterisk) shows intact atrial septum. Note the SVC dilation. B: Rotation of the transducer farther rightward with slightly more superior position in the esophagus shows dropout in the superior portion of the atrial septum (arrows) consistent with sinus venosus ASD. C: Color Doppler showing left-to-right shunt (blue) through the large sinus venosus ASD from left atrium (LA) to right atrium (RA). D: Color flow into the SVC from anomalous right pulmonary vein (red flow with arrows); this view is not diagnostic and further imaging to confirm the anomalous pulmonary vein connection will be needed. A, anterior; S, superior.
Figure 6.11. Transesophageal echocardiographic (TEE) images of anomalous connection of right upper pulmonary vein to superior vena cava (SVC) in a patient with sinus venosus ASD as seen in Figure 6.10. A: Short-axis imaging from level of right pulmonary artery (RPA) showing the teardrop “sign” (asterisk) where the anomalous right pulmonary vein enters the SVC, causing elongation of the normal circular-appearing vessel at this level. B: Color flow Doppler imaging shows red flow from right pulmonary vein into the SVC; flow in the RPA is away from the transducer (blue). A, anterior; L, leftward.
Figure 6.12. Parasternal long-axis images of coronary sinus atrial septal defect (ASD). A: Enlargement of the coronary sinus (CS) is seen in this long-axis image (asterisk) with a hint of dropout in the wall of the CS (arrow). B: A larger gap in the wall of the CS (arrows) is seen during a different part of the cardiac cycle. C: Color Doppler interrogation showing flow (blue, arrow) from the left atrium (LA) to the CS. A, anterior; Ao, aorta; LV, left ventricle; RV, right ventricle; S, superior.
Assessment of RV systolic pressure is an important part of the evaluation of all patients with an ASD (see Fig. 6.6C). The tricuspid regurgitant velocity must be carefully evaluated from multiple imaging planes. In the absence of RV outflow obstruction, this Doppler velocity will reflect pulmonary artery systolic pressure. With significant pulmonary hypertension, there will be RV hypertrophy and eventually decreased RV systolic function.
Interventional and Post-Interventional Imaging
If catheter-based device closure is undertaken for secundum ASD, echocardiography is a crucial adjunct for guidance. Various modalities may be applicable (transthoracic, transesophageal, or intracardiac), depending on patient size and other factors. In some settings, such as with the smaller child, TTE may be all that is needed for guidance, provided that images are of diagnostic quality. Subcostal imaging is optimal for visualization of septal rims and device position with additional imaging planes such as allowing visualization of the ASD device in relationship to the atrioventricular valves. In general, however, for device closure, TEE or intracardiac echocardiography are more commonly used. With TEE, care must be taken to adequately visualize all septal rims, as it may be challenging to see the most posterior portion of the defect with the probe in proximity to the posterior rim and LA. Regardless of the imaging modality chosen, a careful examination will again be necessary to evaluate septal rims and static defect size from multiple imaging planes (Figs. 6.13 and 6.14). In a setting where balloon sizing is performed, echocardiography is crucial for evaluation of the stretched diameter of the ASD at the point where shunt from left to right ceases (“stop-flow” technique). Continuous visualization during careful balloon inflation is used so as not to overstretch the defect; this allows selection of the smallest size device for ASD closure. During device delivery and deployment, careful imaging is warranted to be sure that the left and right atrial discs of the device are in their proper locations, do not prolapse (i.e., LA disc into RA), and do not interfere with surrounding cardiac structures (Fig. 6.15). In addition, once the left side of the closure device is deployed within the LA, shadowing of the RA may occur, so careful imaging is needed. Transgastric imaging may avoid some of the interference from the ASD device and is often helpful after device placement. TEE will usually require general anesthesia due to the potential for airway compromise, in addition to consideration of patient comfort.
Figure 6.13. Transesophageal echocardiographic imaging in a patient with a moderate secundum atrial septal defect (ASD). A: Longitudinal plane imaging demonstrates central ASD (asterisks) with superior (S) and inferior rims. B: Color Doppler demonstrates left-to-right shunt (blue flow) from left atrium (LA) to right atrium (RA). A, anterior.
Figure 6.14. Transesophageal echocardiographic (TEE) imaging in an adult patient with a large secundum atrial septal defect (ASD). Assessment of septal rims is performed in multiple imaging planes and confirms that the defect is not suitable for device closure due to absence of the inferior and posterior rims. A: Apical four-chamber view with probe rotated toward right-sided structures. There is a large secundum ASD (arrows) with a small superior rim and adequate inferior rim seen in this imaging plane. Right atrial (RA) and right ventricular (RV) enlargement are seen. B: Rotation to a short-axis plane reveals the ASD (asterisks) with visible retroaortic rim but no visible posterior rim. C: Further rotation of the imaging plane to a longitudinal view shows absence of posterior/inferior rim (arrow). Care must be taken to fully evaluate this rim from TEE, as the imaging transducer is in very close proximity to the rim. D: Deep transgastric imaging in a longitudinal plane confirms the absence of the posterior/inferior rim of this large ASD (arrow), making it unsuitable for consideration of device closure. The entry of the SVC to the RA is just seen anteriorly to the superior rim (asterisk). A, anterior; Ao, aorta; LA, left atrium; S, superior; SVC, superior vena cava.
Figure 6.15. Transesophageal echocardiographic imaging in patient after implantation of AMPLATZER® Septal Occluder (St. Jude Medical, Inc., St. Paul, MN). A: Longitudinal plane TEE image showing normal device position following delivery; right atrial (RA) disc (arrow) in good position without interference in superior vena caval (SVC) drainage. Septal rims appear appropriate between the left and right discs of the device. B: Modified short-axis image showing device with anterior rims in proximity behind the aortic root, right atrial disc (arrow) in good position. Ao, aorta; LA, left atrium.
In our laboratory, we generally prefer the use of intracardiac echocardiography for catheter-based device closure of secundum ASD or PFO. The smallest probe with four-way steerability (AcuNav; Acusón, Mountain View, CA) can be introduced through an 8 French sheath in the femoral vein. Image quality is excellent, typically allowing an 8.5- to 10-mHz frequency. With the intracardiac echocardiographic catheter positioned in the RA, evaluation of defect rims and pulmonary veins is easily accomplished. The use of intracardiac echocardiography is covered more extensively elsewhere in this text.
If surgery is required for closure of a secundum ASD, TEE typically will be used intraoperatively to evaluate immediate results (Fig. 6.16).
Following intervention, echocardiography is used to evaluate the post-intervention anatomy and function. In device intervention, it is typical to perform an echocardiogram prior to dismissal from hospital the following day. It is important to document device position, as embolization risk is highest in the first day after placement. Right-sided cardiac enlargement often improves immediately and continues to improve over time. There should be no evidence of residual shunt at atrial level by color Doppler. It is important to assess for a pericardial effusion in those patients undergoing closure of ASD, particularly in those who have had surgical intervention early in the course of recovery or in those having relatively large devices in place, as there is a very small risk of long-term device erosion. Longer-term monitoring of the closure device and relationship to surrounding cardiac structures is needed during serial follow-up examinations. In rare situations, there may be a residual shunt around the device (Fig. 6.17). Longer-term noninvasive monitoring will demonstrate the device position and rule out any interference with surrounding cardiac structures, valves, or venous drainage (Figs. 6.18 and 6.19) (Videos 6.12 and 6.13).
Figure 6.16. Transesophageal echocardiographic (TEE) images from the patient in Figure 6.14, following pericardial patch repair of large secundum atrial septal defect (ASD). A: Apical four-chamber TEE views showing intact pericardial patch repair of ASD (arrows). B: Short-axis view of patch between left atrium (LA) and right atrium (RA) (arrows). C: Intact patch seen in longitudinal plane imaging. A, anterior; Ao, aorta; LV, left ventricle; RV, right ventricle; S, superior; SVC, superior vena cava.
Sinus Venosus Defect with Partial Anomalous Pulmonary Venous Return
The goal of surgical correction is to restore the original connection of the right pulmonary veins to the LA, functionally closing the interatrial communication. In addition, unobstructed drainage of the right SVC to the RA must be maintained, either within the original vessel or by reattaching the SVC to the right atrial appendage, sometimes using an interposition graft (Warden procedure). Intraoperative TEE is used for preoperative and postoperative assessment of the patient undergoing complete repair. Post bypass TEE is useful for evaluation of the pulmonary venous pathway and to ensure patency and absence of residual shunt through the pulmonary vein baffle to the RA (Fig. 6.20A–B). In addition, the flow from the SVC to the RA should be laminar with no gradient (Fig. 6.20C–D) (Video 6.14).
Figure 6.17. Images from patient who previously underwent implantation of a CardioSEAL device (NMT Medical, Inc., Boston, MA) for closure of a moderate-sized secundum atrial septal defect (ASD). A: Subcostal coronal view demonstrating the right atrial arms (arrows) are more everted than normal in this patient. Left atrial arms are well opposed to the septum. B: Color flow Doppler interrogation shows a moderate shunt (arrow) from left atrium (LA) to right atrium (RA) through the inferior portion of the device. C: Parasternal long-axis, tricuspid inflow view showing everted right atrial arms of the device (arrows). D: Color flow Doppler demonstrating left-to-right shunt (arrow) through the inferior part of the defect, which remains patent secondary to the position of the device. LV, left ventricle; RV, right ventricle.
Longer postoperative follow-up requires ongoing TTE surveillance for vena cava obstruction and pulmonary vein obstruction. In the adult patient with challenging TTE images, additional TEE or MRI may be required to evaluate the anatomy and physiology definitively.
Figure 6.18. Subcostal imaging in patient following closure of a large secundum atrial septal defect (ASD) with the AMPLATZER® Septal Occluder (St. Jude Medical, Inc., St. Paul, MN). A: Coronal view showing the device in good position in the atrial septum. B:Slightly anterior angulation of the probe, with color Doppler, shows normal, non-aliased superior vena caval (asterisk) flow into the right atrium (RA). C: Rotating the transducer 90 degrees to a short-axis view shows the right atrial disc in relationship to the right atrial structures. The left atrium is foreshortened in this view (arrow). The RA and right ventricle (RV) are normal in size. The inferior vena cava (IVC) entry is widely patent. D: Additional color Doppler flow imaging shows normal, laminar flow into the RA from the SVC (arrow) and the IVC (blue flow). The right atrial disc does not impinge on right atrial inflow despite the large size of the device. LV, left ventricle; S, superior.
FIGURE 6.19. Transthoracic images from same patient as in Figure 6.18. Parasternal short-axis image showing normal right atrial (RA) and right ventricular (RV) size. A: The AMPLATZER® Septal Occluder (St. Jude Medical, Inc., St. Paul, MN) device sits in a normal position in the atrial septum (arrows), without impingement upon the anterior aortic root (Ao). B: Apical four-chamber view shows no device interference with atrioventricular valves. Left atrial (double arrow) and right atrial discs (arrows) are in good position. LA, left atrium; LV, left ventricle.
Figure 6.20. Intraoperative transesophageal echocardiogram (TEE) following repair of sinus venosus atrial septal defect (ASD) associated with partial anomalous pulmonary venous return to the superior vena cava (SVC) (preoperative images shown in Figs. 6.10and 6.11). The repair incorporated a graft between the SVC and the right atrium (RA) (Warden technique). A: Longitudinal plane imaging shows the patch (small arrows) that directs right pulmonary veins (asterisk) to the left atrium (LA) through the ASD. B: Color Doppler shows laminar flow from unobstructed pulmonary vein baffle to the LA. This baffle serves two purposes: the ASD is functionally closed and the right pulmonary veins are directed to the LA. C: Further rightward and slightly superior imaging in the longitudinal plane brings the superior vena caval (asterisk) connection to the RA into view. D: Color Doppler from this imaging plane is foreshortened, although there is no obvious turbulence that would suggest a venous gradient. Imaging from additional planes would be needed to confirm baffle patency. Again, the pulmonary venous pathway appears widely patent. A, anterior; S, superior.
Coronary Sinus ASD (Unroofed Coronary Sinus)
Surgical repair of CS ASD incorporates patch closure of the roof of the CS, excluding it from the LA, and baffling of the left SVC to the CS. If the left SVC is very small and there is an adequate bridging innominate vein, this left SVC may be surgically ligated. Alternatively, a very large left SVC may be directly connected to the left pulmonary artery (left bidirectional cavopulmonary anastomosis) if there appears to be risk of obstruction with a long baffle to the CS. Using TEE in the operating room, the echocardiographer should no longer see flow from the LA to the CS. Agitated saline injection from an intravenous line in the left arm may aid in imaging of the surgical repair to ensure the absence of residual shunt. Follow-up of the patient with repaired CS ASD should reveal no detectable gradient within the CS if the left SVC is baffled to the RA through this pathway. Imaging of a left bidirectional cavopulmonary anastomosis can be accomplished from a suprasternal or high left parasternal window.
Cor triatriatum, an unusual form of abnormal atrial septation, occurs within the LA. Cor triatriatum may result from abnormal incorporation of the common pulmonary vein into the LA, causing obstruction between the pulmonary vein confluence and the LA; however, not all variants of this rare lesion are consistent with this embryologically.
Cor triatriatum may produce signs and symptoms of pulmonary venous obstruction. Timing of presentation depends on the size of the communication between the proximal venous chamber and the distal LA, as well as the location and size of associated communicating ASDs to the RA. The volume of left-to-right shunting from the proximal LA chamber to the RA is proportional to both the size of the ASD between this chamber and the RA, and to the size of the opening within the cor triatriatum membrane to the distal LA.
In the absence of a proximal ASD, a severely obstructed cor triatriatum membrane produces early signs of severe pulmonary venous obstruction. The clinical presentation is similar to the infant with obstructed total anomalous pulmonary venous connection. Cardiovascular collapse, due to RV failure and low cardiac output, may result from unrecognized critical obstruction. On physical examination, there are signs of severe pulmonary hypertension and poor perfusion.
Less severe obstruction may produce signs of tachypnea, feeding difficulties, poor weight gain, and a predisposition to respiratory illnesses. In the patient with a large communication between the proximal chamber and the RA, the clinical presentation resembles a patient with unobstructed total anomalous pulmonary venous connection (with an additional defect providing “right-to-left” communication between the RA and distal LA). Untreated, severely obstructed cor triatriatum will lead to progressive pulmonary vascular disease due to pulmonary venous and arterial hypertension, RV failure, and possible death.
Two-Dimensional Echo Anatomy and Imaging
A membrane is seen within the LA as a linear echo, located above the mitral valve in orthogonal views. As the membrane is somewhat curvilinear, it should be visualized from multiple imaging planes. It is important to note that the left atrial appendage is located between the obstructive membrane and the mitral valve, in contrast to a supravalvular mitral ring, where the left atrial appendage is above the obstructive tissue. In classic cor triatriatum, the proximal chamber communicates only with the LA and not with the RA. There may be a PFO or an ASD between the lower LA chamber and the RA. Another variant of cor triatriatum exists in which all of the pulmonary veins return to the proximal chamber, which does not communicate with the distal LA directly. In this setting, an ASD provides egress to the RA, and a separate more inferior PFO/septal defect allows flow from the RA back to the LA.
Right-sided cardiac structural enlargement is characteristic of cor triatriatum. The RV is typically hypertrophied. RV function may be severely reduced if cardiac decompensation is present with severe membrane obstruction and little atrial communication for decompression of the proximal LA chamber. Quantification of pulmonary artery pressure can be obtained from tricuspid regurgitant velocity measurement using the modified Bernoulli equation.
Subcostal Coronal Views
In the subcostal “coronal” view, an abnormal line of tissue is visualized within the LA. The pulmonary veins connect proximal to this line of tissue, and may be distended. When the membrane is patent, and communicates with the distal LA, color Doppler interrogation will reveal turbulent continuous flow across the obstructed membrane within the LA. Imaging of the atrial septum should be carefully performed to evaluate the presence and location of any interatrial communication, including a Doppler determination of shunt direction and potential gradients. In the absence of a communication between the proximal chamber and the LA, there may be a large ASD between the proximal chamber and the RA with a large left-to-right shunt; a PFO communication between the RA and the distal LA is necessary for maintaining cardiac output and consequently shunts from right to left.
Subcostal Sagittal View
Short-axis imaging demonstrates an abnormal horizontal line of tissue separating the LA into two functional chambers. The atrial septum should be evaluated from both orthogonal subcostal views, to determine the presence or absence of communication between the RA and either the proximal or distal chambers. The RVOT can be easily visualized in the short-axis view, typically showing a dilated main pulmonary artery. If pulmonary regurgitation is present, the end-diastolic velocity can be used to predict pulmonary artery diastolic pressure.
The enlarged right ventricle can be seen in both the parasternal long-axis and short-axis views. Septal motion is abnormal, depending on the degree of pressure overload, again directly related to the degree of obstruction and to the presence of a decompressing atrial communication between the proximal pulmonary venous chamber and the RA. In the long-axis view, there is a linear membrane visualized in the mid-portion of the LA, again seen above the appendage and below the pulmonary veins (Fig. 6.21) (Video 6.15). Color Doppler may be used to demonstrate the communication with the distal chamber.
Imaging of the left atrial membrane from the apical view will show a linear echo appearing above the base of the left atrial appendage and the mitral valve. From this view, the membrane may have a funnel-like appearance and be somewhat mobile. Color Doppler is used to evaluate the communication between the proximal and distal portions of the LA and to visualize fenestrations (Fig. 6.22A–B). This view usually provides the best alignment of the Doppler beam parallel with the opening in the left atrial membrane to the distal LA chamber and allows an estimate of the venous gradient (Fig. 6.22C) [Video 6.16]. If there is a large ASD communicating with the proximal LA chamber, the majority of flow will enter the RA, rather than the distal LA, and may reduce the measured gradient. If there is no communication between this proximal chamber and the LA, an ASD will be seen decompressing from left to right into the RA. In addition, an inferiorly located PFO will be seen with right-to-left shunting. The mitral valve should appear normal, in contrast to supramitral ring, where leaflet mobility is affected.
Figure 6.21. Parasternal long-axis images in a patient with cor triatriatum. A: Diastolic frame showing membrane within the left atrium (LA). The opening in the membrane is seen anteriorly (double arrow). B: Systolic frame with mitral valve closed; there is distance between the membrane (double arrow) and the mitral valve, which suggests cor triatriatum rather than supramitral ring. Ao, aorta; LV, left ventricle; RV, right ventricle.
Figure 6.22. Apical four-chamber images in cor triatriatum. A: Characteristic linear shadow (arrow) is seen within the left atrium (LA), separating the pulmonary vein (PV) entrance from the base of the left atrial appendage (double asterisk). There is a suggestion of septal dropout (single asterisk) between the proximal left atrial chamber and the right atrium (RA). Orthogonal plane imaging is suggested for confirmation. Shadowing within the RA prevents visualization of the tricuspid valve; the right ventricle (RV) is enlarged. B: The addition of color Doppler shows flow convergence medially, with turbulence extending into the distal LA chamber and through the mitral valve into the left ventricle (LV). C: Pulsed-Doppler tracing demonstrating a mean gradient of approximately 10 mm Hg between the proximal chamber and the distal chamber, consistent with significant obstruction. The gradient will depend on the size of the proximal communication with the RA, which provides decompression.
Suprasternal Notch Views
Confirmation of pulmonary venous return to the proximal left atrial chamber should be performed from the suprasternal notch view. A high parasternal short-axis view may be used to evaluate for the presence of a patent ductus arteriosus.
Postoperative Assessment of Cor Triatriatum
Surgical repair of this lesion involves resection of the obstructing membrane within the LA, with pericardial patch repair of any associated ASDs. Postoperative evaluation should include a full assessment of left atrial anatomy and visualization of unobstructed pulmonary venous return. There should be no Doppler gradient at the level of membrane resection and no evidence of atrial level shunt. RV hemodynamics should improve immediately, although pulmonary hypertension and RVH may take some time to resolve, depending on the age of the infant and preoperative course. It is unlikely that there will be long-term cardiac sequelae/residua following successful neonatal repair of cor triatriatum.
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1.A defect in the primum septum usually results in the following type of atrial septal defect:
2.The septal rim (arrow) depicted in this parasternal short-axis image is:
3.The most likely diagnosis in the accompanying video is which of the following:
[Insert Video Question 3 Chapter 6]
B.Coronary sinus ASD
C.Sinus venosus ASD
4.In this patient with the following echo image, you would most likely suspect:
A.Pulmonary valve stenosis
B.Anomalous right pulmonary venous return
C.Anomalous left pulmonary venous return
D.Mitral valve stenosis
5.Which of the following would be the most important contraindication to device closure of an atrial septal defect?
A.Mild tricuspid regurgitation
B.Mild pulmonary valve stenosis
C.Absent posterior/inferior rim
D.Absent anterior rim
6.Review the video provided. Agitated saline was most likely injected from which location?
[Insert Video Question 6 Chapter 6]
A.Right brachial vein
B.Left brachial vein
C.Right saphenous vein
D.Left saphenous vein
7.Infants with the findings seen in this video usually present with which of the following when the atrial septal communication is severely restrictive?
[Insert Video Question 7 Chapter 6]
B.Mild pulmonary hypertension
8.Which of the following defects can be safely closed with catheter-based treatment?
A.Sinus venosus ASD
D.Coronary sinus ASD
9.A patient with a coronary sinus ASD is evaluated following patch closure of the defect. The patient now complains of cyanosis that worsens with exertion. You are most suspicious for the following issue:
A.Right ventricular dysfunction
B.Coronary sinus obstruction
C.Left superior vena cava to left atrium
D.Anomalous left pulmonary vein
10.Typical echocardiographic findings in a patient with ASD include which of the following:
A.Left atrial enlargement
C.Right atrial enlargement
D.Dilated coronary arteries
1.Answer: C. A defect in the atrial septum results in a direct communication between the left atrium (LA) and right atrium (RA). During embryologic development, the primitive atrium undergoes a complex septation process. The septum primum extends inferiorly from the middle of the atrium toward the region of the endocardial cushions, initially leaving an opening called the ostium primum. The inferior portion of the septum primum subsequently fuses with the developing endocardial cushions to close the inferiorly located ostium primum. Tissue reabsorption (or programmed cell death) in the middle of the septum primum leads to a second central opening, or ostium secundum. Concurrently, development of the septum secundum occurs, and once joined with the endocardial cushions, the inferior portions of the two atria are separated. The remaining defect in the septum secundum is the foramen ovale, which allows flow from the fetal RA to LA during gestation. Once birth occurs, fusion of these two septa should occur, functionally closing the foramen ovale; however, probe patency is present in approximately 25% to 30% of the population. Secundum ASDs, typically occurring in the central or secundum portion of the atrial septum, actually result from a true deficiency in the septum primum.
2.Answer: A. The figure depicts a parasternal short-axis image with the aorta in the center. The rim indicated by the arrow immediately posterior to the aorta is an anterior rim. The superior and inferior portions of the atrial septum are not typically seen in a short-axis image. The posterior rim is also well-visualized in the image, but is not the rim indicated by the arrow.
3.Answer: B. In this apical four-chamber view, there is evidence of right-sided enlargement consistent with an atrial level shunt. At the beginning of the clip, the ostium of the coronary sinus appears very enlarged, and when scanning posteriorly one can see a significant amount of dropout in the area where the normal roof of the coronary sinus would be. Since this tissue plane is relatively perpendicular to the plane of imaging, one would typically see the roof of the coronary sinus well in this view. The appearance of both the enlarged coronary sinus entry into the right atrium and the large amount of dropout in the roof of the coronary sinus is most consistent with a coronary sinus ASD. Cor triatriatum should appear as a linear membrane in the left atrium, separating the proximal and distal portions of the LA. Sinus venosus ASD will be seen in subcostal images as dropout immediately below the superior vena cava entry to the atrium. The atrial septum above the entry of the coronary sinus, as seen in this apical view, appears intact, which is not consistent with the appearance of a secundum ASD.
4.Answer: B. The subcostal short-axis (sagittal) image shows a sinus venosus ASD with dropout immediately below the SVC as it enters the right atrium. A sinus venosus ASD is located in the superior/posterior region of the atrial septum and will be seen directly adjacent to the SVC without an intervening superior rim. Sinus venosus ASD is typically associated with anomalous drainage of the right upper and/or middle lobe pulmonary veins to the SVC–RA junction. The lower right pulmonary vein is rarely involved. Although the connection of the anomalous pulmonary vein(s) may be “high” in the SVC, their connection is not typically present above the entry of the azygous vein to the SVC. The left pulmonary veins are typically normal in sinus venosus defects. Pulmonary or mitral valve stenosis is rare.
5.Answer: C. Absence of the posterior/inferior rim is a significant issue in placement of a closure device in the setting of secundum ASD. Absence of this rim is a risk factor for device embolization at the time of, or shortly after, device placement due to instability of the device. Oversizing to accommodate lack of posterior/inferior rim is not recommended to overcome this limitation. Device closure of ASD is considered when there is an appropriate size secundum ASD with appropriate rims. Absent anterior rim is not a contraindication to device closure although it may have some bearing on the size and type of device that is selected. Mild tricuspid regurgitation is common and is not a contraindication to device closure; this will typically resolve following closure. Pulmonary valve stenosis (PS) can be associated with ASD and can be treated with balloon valvuloplasty during the cardiac catheterization procedure if felt to be moderate; mild PS generally would not require treatment and the gradient may be less following closure of the ASD with reduction of shunt volume.
6.Answer: B. The video is a parasternal long-axis view depicting an enlarged coronary sinus with dropout in the coronary sinus roof, consistent with a coronary sinus ASD. Injection of agitated saline into the left brachial vein causes immediate appearance of contrast into the coronary sinus and left atrium (almost simultaneously), then filling the left-sided cardiac structures; this is most consistent with the presence of a left superior vena cava, which is nearly always present in coronary sinus ASD. Injection of saline through the left brachial vein first enters the left superior vena cava, causing this classic appearance in coronary sinus ASD. A CS ASD is almost always associated with connection of the left SVC to the roof of the LA. It is important to identify the drainage of the left SVC for purposes of surgical intervention. As an adjunct to imaging, an agitated saline injection through an intravenous line in the left arm will demonstrate bubbles appearing initially in the LA and subsequently the RA. Injection of saline through the right brachial vein would first appear in the right-sided cardiac structures, as would injection in either of the peripheral leg veins (right saphenous, left saphenous). IV saline injection through the leg veins may be useful in the diagnosis of preferential shunt from the right atrium to the left atrium through a patent foramen ovale, such as in the clinical setting of orthodeoxia.
7.Answer: A. The video shows an apical four-chamber view with a severely enlarged right ventricle and reduced systolic function. The left ventricle is underfilled and there is a clear horizontal membrane in the left atrium consistent with cor triatriatum. In the absence of a proximal ASD, a severely obstructed cor triatriatum membrane produces early signs of severe pulmonary venous obstruction. The clinical presentation is similar to the infant with obstructed total anomalous pulmonary venous connection. Cardiovascular collapse, due to RV failure and low cardiac output, may result from unrecognized critical obstruction. Severe pulmonary hypertension is the rule in this situation. In the neonate with severe left atrial obstruction due to this lesion, atrial flutter is very uncommon. Although respiratory symptoms such as tachypnea and respiratory distress are present, these symptoms are due to the obstruction of pulmonary venous return through the restricted membrane rather than pneumonia.
8.Answer: B. A secundum ASD produces characteristic dropout in the central-most portion of the atrial septum. Most defects are relatively elliptical in shape. Assessment from multiple views is needed to fully evaluate the maximum ASD dimensions, septal rims, and relationship of the ASD to surrounding cardiac structures. With the widespread availability of transcatheter device closure of secundum ASD, the echocardiographer plays a critical role in assessment and patient selection for catheter-based therapy. One must also exclude the presence of fenestrations or aneurysmal septal tissue in association with a secundum ASD, although these often remain amenable to device closure. It is very important to rule out any defects that would require surgical attention: 1) primum ASD is typically associated with cleft anterior mitral valve leaflet;, 2) sinus venosus ASD is associated with anomalies of right pulmonary venous return; and 3) coronary sinus ASD is associated with left superior vena cava to the left atrium. None of these are appropriate for consideration of device closure.
9.Answer: C. A CS ASD is almost always associated with connection of the left SVC to the roof of the LA. It is important to identify the drainage of the left SVC for purposes of surgical intervention. As an adjunct to imaging, an agitated saline injection through an intravenous line in the left arm will demonstrate bubbles appearing initially in the LA and subsequently the RA. If the left SVC is missed or is allowed to remain anomalously connected to the LA following surgical repair of the CS ASD, the patient will have persistent cyanosis due to systemic venous return to the LA.
10.Answer: C. Right-sided chamber enlargement is the hallmark of an atrial level shunt. When seen on echocardiographic imaging, this should prompt a comprehensive evaluation of the atrial septum and definition of pulmonary venous return.