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    Drugs & Diseases > Cardiology

    Atrial Septal Defect Workup

    Updated: May 01, 2017
    • Author: David H Adler, MD, FACC; Chief Editor: Yasmine S Ali, MD, FACC, FACP, MSCI  more...
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    Workup

    Laboratory Studies

    No specific laboratory blood tests are indicated in the workup of atrial septal defects (ASDs).

    Routine laboratory studies should be performed in patients undergoing intervention for ASD, such as the following:

    • Complete blood cell (CBC) count

    • Type and screen

    • Metabolic profile or chemistry panel

    • Coagulation studies (prothrombin time [PT] and activated partial thromboplastin time [aPTT])

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    Imaging Studies

    Chest radiography

    In the presence of a clinically significant left-to-right shunt, chest radiographs most often show cardiomegaly because of dilatation of the right atrium and right ventricular chamber.

    The pulmonary artery is prominent, and pulmonary vascular markings are increased in the lung fields.

    Left atrial enlargement is rare only if clinically significant mitral regurgitation. On occasion, proximal dilatation of the superior vena cava can be seen in sinus venosus defect.

    Transthoracic echocardiography

    An uncertain diagnosis can be clarified with transthoracic 2-dimensional (2-D) echocardiography, which provides direct noninvasive visualization of most types of atrial septal defects (ASDs), including evaluation of the right atrium, right ventricle, and pulmonary arteries, as well as other associated abnormalities. The view most beneficial is often the subcostal view. One exception is the diagnosis of a sinus venosus defect, for which transesophageal echocardiography (TEE) may be needed to image the defect, but this still may not be able to visualize the pulmonary venous return. TEEs and an echocardiogram are shown below:

    Parasternal short axis: RV dilation with RV pressu Parasternal short axis: RV dilation with RV pressure overload as evidenced by flattening of the interventricular septum in systole.
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    Transesophageal echocardiogram: Moderate-large ASD Transesophageal echocardiogram: Moderate-large ASD with left-to-right shunt across the interatrial septum.
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    Apical 4-chamber view. Apical 4-chamber view.
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    In any patient with an ASD, particularly a sinus venosus defect, anomalies of systemic venous connection should be sought. These can be clearly identified by 2-D imaging. Right atrial and right ventricular enlargement without identification of the cause should prompt consideration for a TEE.

    Doppler echocardiography may be helpful in demonstrating flow across the atrial septum. It typically shows a biphasic (systolic and diastolic) pattern with a small right-to-left shunt at the beginning of systole. Real-time (RT) 3-dimensional (3D) Doppler TEE can also provide detailed and precise information regarding the selection of the appropriate occluder device as well as facilitate the transcatheter occlusion by guiding the catheter through the often challenging patient anatomy. [8]

    Transthoracic echocardiography (TTE) may be suboptimal in some patients with poor echocardiographic windows. In such patients, TEE can provide excellent definition of the atrial septum. TEE is also useful in guiding device placement during catheter ASD occlusion procedures and in providing immediate intraoperative assurance that defect closure is accomplished.

    Continuous-wave Doppler echocardiography is valuable for estimating right ventricular (and pulmonary arterial when there is no associated right ventricular outflow tract obstruction) systolic pressure when a tricuspid regurgitant jet is present. This technique is also useful in evaluating patients for obstruction to pulmonary venous return.

    Contrast echocardiography can provide additional confirmation. A right-to-left shunt can be detected by visualizing microcavitation bubbles in the left atrium and the left ventricle. A left-to-right shunt can be detected as a negative contrast washout effect in the right atrium.

    Magnetic resonance imaging (MRI)

    MRI has successfully been used to identify the size and position of ASD. However, utility is limited for small defects. A major advantage of MRI is the ability to quantify right ventricular size, volume, and function along with the ability to identify the systemic and pulmonary venous return.

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    Other Tests

    Electrocardiography

    Characteristic findings in patients with secundum atrial septal defect (ASD) are a normal sinus rhythm, right-axis deviation, and an rSR' pattern in V1, an interventricular conduction delay or right bundle branch block (which represents delayed posterobasal activation of the ventricular septum and enlargement of the right ventricular outflow tract).

    Left-axis deviation and an rSR' pattern in V1, an interventricular conduction delay or right bundle branch block suggests an ostium primum defect. Left-axis deviation and negative P wave in lead III suggest sinus venosus defect.

    Increasing pulmonary hypertension can cause loss of the rSR' pattern in V1 and a tall monophasic R wave with a deeply inverted T wave.

    A prolonged P-R interval can be seen in familial ASD or ostium primum secondary to left atrial enlargement and an increased distance for internodal conduction produced by the defect itself. Displacement of the AV node in a posteroinferior direction in some patients or an enlarged right atrium has also been reported.

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    Diagnostic Procedures

    When noninvasive techniques demonstrate the presence of an uncomplicated atrial septal defect (ASD) in a child, routine cardiac catheterization for diagnosis is unnecessary.

    However, cardiac catheterization may be useful if the clinical data are inconsistent, if clinically significant pulmonary arterial hypertension is suspected, or if concurrent coronary artery disease must be assessed in patients older than 40 years. Catheterization is also a viable alternative for intervention for secundum ASD.

    The diagnosis of ASD may be confirmed by directly passing the catheter through the defect. Note the following:

    • Serial oxygen saturation measurements can be used to estimate the magnitude of the shunt

    • In young patients, right heart pressures are often normal despite a large shunt.

    • If high oxygen saturation is present in the superior vena cava or if the catheter enters a pulmonary vein directly from the right atrium, sinus venosus type is likely.

    • Partial anomalous pulmonary venous return is usually associated with sinus venosus defect, but it may also accompany the ostium secundum type.

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