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 Table of Contents  
FOCUS ISSUE - CONGENITAL HEART DISEASE
Year : 2020  |  Volume : 4  |  Issue : 3  |  Page : 253-259

Echocardiographic Evaluation of Atrial Septal Defect


Department of Paediatric Cardiology, Fortis Escorts Heart Institute, New Delhi, India

Date of Submission16-Aug-2020
Date of Acceptance02-Oct-2020
Date of Web Publication18-Dec-2020

Correspondence Address:
Dr. Sushil Azad
Department of Paediatric Cardiology, Fortis Escorts Heart Institute, New Delhi - 110 025
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jiae.jiae_45_20

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  Abstract 

Atrial septal defect accounts for 8-10% of all congenital heart defects. Echocardiography is method of choice for assessment of patient with a known or suspected atrial septal defect. A Thorough knowledge and understanding of all echocardiographic view is essential for complete assessment of atrial septal defect , associated physiological status and assessment of neighbouring intracardiac structures. Complete evaluation is crucial for planning the modality of treatment whether it is suitable for catheter intervention or needs surgical intervention.

Keywords: Echocardiography, trans esophageal echocardiography, trial septal defect


How to cite this article:
Azad S. Echocardiographic Evaluation of Atrial Septal Defect. J Indian Acad Echocardiogr Cardiovasc Imaging 2020;4:253-9

How to cite this URL:
Azad S. Echocardiographic Evaluation of Atrial Septal Defect. J Indian Acad Echocardiogr Cardiovasc Imaging [serial online] 2020 [cited 2021 Apr 13];4:253-9. Available from: https://www.jiaecho.org/text.asp?2020/4/3/253/303939


  Introduction Top


Atrial septal defects (ASDs) represent nonphysiological communication between two atria with an approximate incidence of 1 in 1500 live births, thus accounting for approximately 8%–10% of congenital heart defects.[1],[2] The evaluation of ASDs requires a systematic approach using imaging modalities such as transthoracic echocardiogram (TTE), transesophageal echocardiogram (TEE), and intracardiac echocardiography (ICE). Defects in the atrial septum are named according to their embryological origin. There are five major types of defects which include ostium secundum type of defect which occurs due to defect in the fossa ovalis region which is the most common variety followed by ostium primum (defect in the endocardial cushions), coronary sinus defect (region of the ostium of coronary sinus), and sinus venosus defects which are not true ASDs, but these defects lead to abnormal shunting at the atrial level and patent foramen ovale (PFO). There is a debate that whether PFO should be included in in this category of true ASDs, as no septal tissue is missing.[3] Understanding the type of ASD, size, location, and association of other congenital defects are important in management of these patients.

With an uneven distribution of resources and widespread use of echocardiography, ASDs can have a varied presentation from completely asymptomatic incidentally picked lesion to an ASD with pulmonary vascular obstructive disease. Hence, evaluating ASDs requires a good knowledge of natural history, clinical examination, and use of echocardiographic (TTE, TEE, and ICE), and in rare instances, cardiac catheterization and advanced imaging options such as magnetic resonance imaging may also be needed. We will limit our discussion to the echocardiographic evaluation of ASD and will focus on two-dimensional (2D) and three-dimensional (3D) imaging techniques for evaluating ASDs.


  Anatomy of Atrial Septal Defects Top


Understanding the anatomy of ASDs requires detailed knowledge of the underlying anatomy of the interatrial septum which is the key factor in deciding the treatment options. The atrial septum has three components: septum primum, septum secundum, and atrioventricular (AV) canal septum. Sinus venosus is not considered a true component of atrial septum but is an adjacent structure through which interatrial communication occurs.[4] Various defects are classified as per the anatomic location in the interatrial septum [Figure 1].
Figure 1: (a and b) anatomical landmarks and various types of atrial septal defect and their locations. ASD: Atrial septal defect, RA: Right atrium, CT: Crista terminalis, Ao: Aorta, SVC: Superior venacava, RUPV: Right upper pulmonary vein, RMPV: Right middle pulmonary vein, RLPV: Right lower pulmonary vein, FO: Fossa ovalis, IVC: Inferior venacava, EV: Eustachian valve, CS: Coronary sinus

Click here to view



  Fossa Ovalis Atrial Septal Defects Top


A fossa ovalis ASD is the most common form of a true ASD occurring as the result of a true deficiency of septum primum tissue. These defects can vary in shape and can be elliptical or round. With large ostium secundum defects, the septum primum is often nearly or completely absent. In some cases, persistent strands of the septum primum will be present and will cross the defect, resulting in multiple communications and creating multiple fenestrations. The size of secundum ASDs is variable from small defects to very large defects and these can enlarge over time with age and cardiac growth.[5] A rare form of ostium secundum ASD occurs when the superior limbic band of the septum secundum is absent. In such cases, the atrial communication is “high” in the septum in close proximity to the superior vena cava (SVC) and is typically called as a high type of secundum ASDs and they are not to be confused with the sinus venosus defect of the SVC type as it is not associated with anomalous pulmonary venous return.


  Sinus Venosus Defects Top


Sinus venosus defects, as discussed, are not true ASDs. They are less common than ostium secundum ASDs. These defects occur as a result of a partial or complete absence of the sinus venosus septum between the SVC and the right upper pulmonary vein (SVC type) which is more common or the right lower and middle pulmonary veins and the right atrial (RA) (inferior vena cava [IVC] type) which is more unusual.


  Coronary Sinus Type of Defects Top


It is also called as “unroofed coronary sinus” and is one of the rare forms of atrial communication. In this defect, the wall of the coronary sinus within the left atrium is deficient or completely absent; thus, left atrial blood enters the coronary sinus and drains into the RA through the coronary sinus opening. Association of left SVC with a coronary sinus septal defect is termed “Raghib syndrome.”

Contrast injection with agitated saline is particularly useful in establishing the diagnosis.


  Common Atrium Top


Absence of all components of atrial septum including septum primum, septum secundum and AV septum results in Common atrium. It is typically seen in association with heterotaxy syndrome. Some remnants of tissue might still be present in these patients.


  Echocardiographic Evaluation Top


The most widely used ultrasound modality to evaluate the interatrial septum is transthoracic echocardiogram (TTE), especially useful in small children in whom the ultrasound image quality will typically permit a full diagnostic study. It can also be used for complete patient selection for transcatheter ASD closure and procedural guidance in pediatric patients.

However, in adults, transesophageal echocardiogram (TEE) is required to further characterize the atrial septal abnormalities because the TTE image quality will not always permit a comprehensive evaluation of the interatrial septum. 2D and 3D TEE provides significant additional anatomic information compared with TTE and should be performed in all adult patients being evaluated for percutaneous transcatheter closure or surgical therapy.

3D TEE significantly improves the visualization of ASD and its relation to surrounding tissue rims and structures and allows for en face viewing of the ASD and surrounding fossa providing an accurate determination of the ASD size and shape and is now extensively used for guidance during percutaneous transcatheter closure.[6],[7] In addition, it has the potential to clearly and comprehensively define the dynamic morphology of the defect which changes with each cardiac cycle.


  Transthoracic Echocardiography for Atrial Septum Top


The atrial septum can be evaluated fully using TTE. For defining the type of defect and its relationship to other structures, multiple views should be used. Subcostal sagittal and coronal views are best to define the ASDs[8],[9] but may not be adequate in adults and in them other views should be. Apical four-chamber view is not recommended for ASD assessment as the beam of ultrasound in parallel to the septum, so dropouts may appear and give a false impression of an ASD.


  Views Top


Subcostal coronal view

This is the preferred view for visualization of ASDs like fossa ovalis and sinus venosus defects, as in this view, septum is aligned perpendicular to the ultrasound beam. Fossa ovalis defects are visualized in the central part of the atrial septum [Figure 2]. It may be difficult to visualize the SVC type of sinus venosus defect in this view because of its posterosuperior location, but IVC type of sinus venous defect can be visualized by tilting the transducer posterior and inferiorly [Figure 3]. In addition to the type of defect, it is a good view to assess the drainage of pulmonary veins.
Figure 2: Subcostal Coronal view with fossa ovalis defect seen in the middle of atrial septum with atrial and atrioventricular valve rims seen. LA- Left atrium, RA- Right atrium, ASD- Atrial septal defect, AV- Atrioventricular valve

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Figure 3: Subcostal coronal view with posterior and inferior tilt showing (a) two dimensional echocardiographic image showing the defect with overriding of the IVC (b) Colour flow mapping showing left to right shunting across the defect. IVC- inferior vena cava, SV- sinus venosus

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Subcostal sagittal view

In this view, septum is profiled along its superior–inferior axis and also anteroposterior axis, thus permitting good visualization of SVC type of sinus venosus defect [Figure 4] which is visualized in the superior portion of the atrial septum. Furthermore, in this view, IVC type of sinus venous defect can be visualized in the posterior and lower portion of the atrial septum [Figure 5]. Fossa ovalis defect is seen in the middle part of the septum with good visualization of SVC and IVC rims [Figure 6].
Figure 4: Subcostal view of a patient with SVC type of Sinus venosus ASD. (a) Subcostal coronal view showing the defect in the superior portion of the septum with overriding f the SVC. (b) Subcostal sagittal view in two dimensional showing the defect in the superior portion of the septum(arrow), with intact fossa ovalis. (c) on colour flow mapping showing left to right shunt across the defect (arrow)

Click here to view
Figure 5: Subcostal sagittal view showing IVC type sinus venous ASD on (a) two dimensional echocardiography and (b) on colour flow mapping showing left to right shunt with anomalous drainage of right lower pulmonary vein. PAPVC- partial anomalous pulmonary venous connection. RLPV: Right lower pulmonary vein, IVC: Inferior venacava, LA: Left atrium, RA: Right atrium

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Figure 6: Subcostal sagittal view showing fossa ovalis defect (a) on two dimensional echocardiography with good visualisation of the SVC and IVC rims, (b) on colour flow mapping showing left to right shunt. SVC: Superior venacava, IVC: Inferior venacava

Click here to view


Subxiphoid windows typically allow the best visualization of the atrial septum and its related structures. Assessment of the amount of the surrounding rims of tissue present is crucial. A deficiency of rim tissue between the defect and pulmonary veins, AV valve, or IVC will preclude transcatheter closure, and a deficiency of aortic rim can increase the risk of device erosion in certain circumstances.

In adolescence and adulthood, the subxiphoid window is often inadequate because of the distance from the probe to the atrial septum. Thus, other views such as the parasternal short axis modified four-chamber or right parasternal views should be used to assess the atrial septum.

Apical four-chamber view

In this view, the ultrasound beam is parallel to the atrial septal plane; thus, artificial dropouts are commonly seen so not a preferred view. Fossa ovalis defect is usually seen in the mid-portion of the septum [Figure 7]. By tilting the transducer posteriorly, IVC type of sinus venosus defect can be visualized. When all components of the atrial septum are absent, it results in common atrium [Figure 8].
Figure 7: Apical four chamber view showing a fossa ovalis defect in the middle part of the septum with atrial and atrioventricular valve septal rim. Also seen dilatation of right atrium and ventricle. RV: Right ventricle, LV: Left ventricle, LA: Left atrium, RA: Right atrium, FO-ASD: Fossa ovalis atrial septal defect, AV: Atrio-ventricular

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Figure 8: Apical four chamber view showing complete absence of all components of the atrial septum, including the septum primum, septum secundum, and AV canal septum are absent thus resulting in a common atrium (arrow). AV: Atrio-ventricular

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Parasternal short-axis view [Figure 9] and long-axis view along with four chamber view provide additional information by visualization of other structures such as the ventricles and great arteries are necessary to assess for secondary findings related to the hemodynamic consequences of an ASD such as RA, right ventricular (RV) and pulmonary artery (PA) dilatation. [Table 1] summarizes the different views for ASD assessment. In some cases, a full assessment of the atrial septum might not be possible with TTE. Thus, TEE could be required. In certain special situations, a contrast injection with agitated saline is particularly helpful in establishing the diagnosis of coronary sinus type of ASD [Figure 10].
Figure 9: Parasternal short axis view at the level of aorta showing fossa ovalis defect. Also seen are the atrial and aortic rims of the defect. LA: Left atrium, RA: Right atrium, FO-ASD: Fossa ovalis atrial septal defect

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Figure 10: Subcostal coronal view showing (a) deficient wall of the coronary sinus (CS) within the left atrium thus left atrial blood enters the coronary sinus and drains into the RA through the coronary sinus opening on colour flow mapping (b) (arrow), (c) with agitated saline contrast filling the left atrium completely (Blue arrow). LA: Left atrium, RA: Right atrium, ASD: Atrial septal defect

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Table 1: Transthoracic echocardiography views for atrial septal defect anatomical assessment

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  Transesophgeal Echocardiogram for Atrial Septal Defects Top


Multiple and sequential TEE views should be used to completely and systematically evaluate the interatrial septum. The size, shape, and location of interatrial communication present should be assessed as is its relationship with its surrounding structures. [Table 2] summarizes various views' ASD assessment.
Table 2: Transesophageal echocardiography views for atrial septal defect assessment

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Views which are most useful for the evaluation of ASDs on TEE are:

  1. Basal short-axis view
  2. Four-chamber view
  3. Bicaval view.


Basal short-axis view

Fossa ovalis defect is seen in the mid-portion of the septum with good visualization of atrial and aortic rim [Figure 11].
Figure 11: Basal short axis view of two dimensional TEE showing atrial septal defect in the middle part of the septum. Atrial and aortic rims are also seen. TEE: Tanseophageal echocardiogram. LA: Left atrium, RA: Right atrium, FO-ASD: Fossa ovalis atrial septal defect, RV: Right ventricle

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Four-chamber view

In this view, the fossa ovalis defect can be seen in the mid-portion of the septum [Figure 12]. It also provides good visualization of the atrial and AV valve septal rim of the defect. In this view, pulmonary veins can also be visualized by rotating the transducer probe.
Figure 12: Transesophageal Echocardiography: Four chamber view showing fossa ovalis defect with dilated right atrium and right ventricle. LA: Left atrium, RA: Right atrium, FO-ASD: Fossa ovalis atrial septal defect, RV: Right ventricle, LV: Left ventricle

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Bicaval view

In this view, atrial septum is profiled along with its relation with the SVC and IVC. Fossa ovalis defects are seen in the middle portion of the septum, while sinus venosus defects are seen in relation with the SVC (SVC type of sinus venosus defect) or IVC (IVC type of sinus venosus defect [Figure 13].
Figure 13: Transesophageal echocardiogram: Bicaval view showing SVC type of sinus venosus defect (a) in two dimensional with overriding of SVC (b) on colour flow mapping showing left to right shunt. LA: Left atrium, RA: Right atrium, SV ASD: Sinusos venosus atrial septal defect

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The American Society of Echocardiography currently recommends 2D TEE during transcatheter closure of ASDs. 3D TEE offer a clearer view of the defect, allows for en face viewing of ASD, leading to more accurate measurements, its relationship to the surrounding cardiac structures thus increased closure rates, and better identification of patients at higher risk of complications, prompting closer follow up. It is especially helpful in cases with two or more ASDs when contemplating device closure with two devices it helps in better anatomic orientation of the defect [Figure 14].
Figure 14: Transesophageal echocardiogram (a) in patient showing two defects in the fossa ovalis area (arrow). 3D reconstruction done in the same patient shows three defects (arrow) (b). LA: Left atrium, RA: Right atrium

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For detection of sinus venosus ASDs, especially in adults, 3D TEE-reconstructed images can correctly visualize the defect in relation to the SVC and the anomalously draining right superior pulmonary vein, whereas 2D imaging has been inferior in this regard.

A thorough echocardiographic evaluation of ASD includes the detection of

  1. Type of defect/number of defects/quantification of the size and shape of the septal defects
  2. Hemodynamic assessment


    • Shunt direction
    • Impact of shunting-RA/RV dilatation/PA pressure assessment, RV, and left ventricular function.


  3. Suitability for device closure.


    • Adequacy of rims
    • Assessment of coronary artery anatomy.



  Hemodynamic Assessment-Shunt Direction/Right Atrial/Right Ventricular Dilatation/Pulmonary Artery Pressure Top


Hemodynamic assessment is important to decide whether to intervene or not and when to intervene. Indication for closing an ASD is a documented evidence of RV volume overload without evidence of irreversible pulmonary vascular disease.[10] Apical four-chamber views are used for assessing RA/RV dilatation and M-mode in parasternal long-axis view for quantification of RV dimensions and septal motion. PA pressure assessment is done using Doppler interrogation of TR or PR jet. Assessment of mitral valve is important before any intervention on ASDs.


  Suitability for Device Closure Top


Assessment of rims

Assessment of rims is important in deciding the intervention and also anticipating complications in high-risk interventions. A deficiency of rim tissue between the ASD and IVC or AV valve will preclude transcatheter closure; on the other hand, a deficient of aortic rim increases the risk of device erosion, so these have to be documented. [Table 3] shows various TTE and TEE views for assessment of SVC, IVC, and aortic and atrial rims, respectively. Nomenclature of rims is done according to the structures forming the rims and is essential in conforming uniformity in description of defects.[11] Device closure is not advised for secundum ASD with deficient rims (<5 mm).
Table 3: Transthoracic echocardiography and transesophageal echocardiography views for atrial septal defect rims' assessment

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Coronary anatomy

Assessment for coronary artery anatomy is required before device closure of ASD is contemplated, as the anomalous coronary artery may get compressed between ASD device and aortic rim. This could be avoided by thoroughly examining coronary artery anatomy on TTE and TEE.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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van der Linde D, Konings EE, Slager MA, Witsenburg M, Helbing WA, Takkenberg JJ, et al. Birth prevalence of congenital heart disease worldwide: A systematic review and meta-analysis. J Am Coll Cardiol 2011;58:2241-7.  Back to cited text no. 1
    
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Taniguchi M, Akagi T, Watanabe N, Okamoto Y, Nakagawa K, Kijima Y, et al. Application of real-time three-dimensional transesophageal echocardiography using a matrix array probe for transcatheter closure of atrial septal defect. J Am Soc Echocardiogr 2009;22:1114-20.  Back to cited text no. 7
    
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Silvestry FE, Cohen MS, Armsby LB, Burkule NJ, Fleishman CE, Hijazi ZM, et al. Guidelines for the echocardiographic assessment of atrial septal defect and patent foramen ovale: From the American Society of Echocardiography and Society for Cardiac Angiography and Interventions. J Am Soc Echocardiogr 2015;28:910-58.  Back to cited text no. 8
    
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Puchalski MD, Lui GK, Miller-Hance WC, Brook MM, Young LT, Bhat A, et al. Guidelines for performing a comprehensive transesophageal echocardiographic: Examination in children and all patients with congenital heart disease: Recommendations from the American Society of Echocardiography. J Am Soc Echocardiogr 2019;32:173-215.  Back to cited text no. 9
    
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Saxena A, Relan J, Agarwal R, Awasthy N, Azad S, Chakrabarty M, et al. Indian guidelines for indications and timing of intervention for common congenital heart diseases: Revised and updated consensus statement of the Working group on management of congenital heart diseases. Ann Pediatr Cardiol 2019;12:254-86.  Back to cited text no. 10
    
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Shrivastava S, Radhakrishnan S. Echocardiographic anatomy of atrial septal defect: “Nomenclature of the rims”. Indian Heart J 2003;55:88-9.  Back to cited text no. 11
    


    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11], [Figure 12], [Figure 13], [Figure 14]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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  In this article
Abstract
Introduction
Anatomy of Atria...
Fossa Ovalis Atr...
Sinus Venosus De...
Coronary Sinus T...
Common Atrium
Echocardiographi...
Transthoracic Ec...
Views
Transesophgeal E...
Hemodynamic Asse...
Suitability for ...
References
Article Figures
Article Tables

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