Imaging Studies
General laboratory studies are rarely helpful in sinus venosus atrial septal defect (ASD). However, imaging studies help in the evaluation and diagnosis of suspected sinus venosus ASD.
Chest radiography
Findings on chest radiography may include the following:
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Prominent right atrium
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Prominent main pulmonary artery
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Increased heart size and pulmonary vascularity
Echocardiography
Echocardiography (ECHO) reveals ASD and most of the pulmonary vein connections in most patients and is the diagnostic modality of choice. [4]
Two-dimensional ECHO with color flow Doppler reveals the position and size of the defect and the presence of anomalous pulmonary venous drainage (in many of these cases). It also helps identify associated anomalies and reveals the left-to-right (or right-to-left) direction of flow and the degree of right ventricular overload.
In a retrospective study, Snarr et al found that the absence of the posterior rim ("bald" posterior wall) is a consistent finding in patients with an inferior sinus venosus defect (SVD) and that it distinguishes an inferior SVD from a large secundum ASD with inferior extension. In transthoracic echocardiograms, the posterior rim was absent in all 15 patients with a surgical diagnosis of inferior SVD, but it was present in all 14 patients with a secundum ASD. For all observers, the diagnostic accuracy of inferior SVDs showed a statistically significant increase with the use of the rim criterion (P< 0.0001). [5]
In children with difficult transthoracic windows, or in older or larger patients, transesophageal echocardiography may be helpful in imaging the defect and pulmonary vein connections. [6] In the current era, cardiac magnetic resonance angiography (MRA)/magnetic resonance imaging (MRI) may be alternatively used to complete the diagnostic information needed prior to surgery.
Cardiac MRI/MRA
Features that may be seen with MRI/MRA include the following:
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Atrial septal defect size and location are shown.
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Excellent delineation of individual pulmonary vein connections can be identified.
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Right ventricle enlargement and indexing to body surface area (BSA) is available if helpful.
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Flow-quantification may also be performed.
Electrocardiography
Note the following:
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Right ventricular hypertrophy predominates, with a lengthened PR interval and incomplete right bundle branch block secondary to right ventricular dilation (small rSR').
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Peaked P waves in lead II may demonstrate right atrial enlargement.
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Abnormal P-wave axis (negative in lead AVF) would indicate a displaced sinus node inferiorly (non sinus atrial rhythm).
Procedures
Cardiac catheterization
Cardiac catheterization is usually not required in the preoperative assessment of patients with sinus venosus atrial septal defect, but it may be considered in the following circumstances:
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In any child in whom associated lesions are suspected or in whom pulmonary hypertension is suspected, catheterization is performed to measure pulmonary artery pressure and, if pulmonary resistance is elevated, the response to pulmonary vasodilators.
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Adults who have the potential for associated coronary atherosclerotic lesions should undergo catheterization to exclude these abnormalities before surgical repair of the sinus venosus atrial septal defect.
Histologic Findings
Patients with pulmonary hypertension and advanced pulmonary vascular obstructive disease may exhibit histologic changes similar to those seen in pulmonary vascular disease. Specifically, these include intimal and medial hypertrophy and, in more advanced lesions, luminal occlusion.
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Panel A. Transesophageal echocardiogram (transverse view) of a patient with a sinus venosus defect of the superior vena cava (SVC) type. The original defect (white star burst) has been repaired by placing a baffle (arrows), which directs blood from the anomalously connected right upper pulmonary vein into the left atrium (LA). In this patient, the baffle was redundant so at a more rostral level (Panel B), it could be seen (black open arrows) to bulge into the superior vena cava (SVC)–right atrial (RA) junction (trio of white arrows). The remainder of the atrial septum is denoted by the duo of white open arrows. Panel C is a transesophageal echocardiogram, sagittal view. Doppler color flow mapping verifies that the protruding baffle (white closed arrows) results in a narrowing of the pathway from the SVC to the RA. The quartet of white open arrows points to the remainder of the atrial septum.
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Panel A is a transesophageal echocardiogram, transverse view. The white star burst shows the sinus venosus defect of the inferior vena cava (IVC) type, lying adjacent to the IVC junction with the right atrium (RA). The remainder of the atrial septum is just out of the view of this sector but is represented by the white open arrowheads. The leaflets of the closed tricuspid valve (TV) are visible. RV = right ventricle. Panel B is a transesophageal echocardiogram, sagittal view. This is the same patient as in Panel A. This view proves that the rostral portion of the atrial septum (which would be missing in a patient with a sinus venosus defect of the SVC type) is intact. ct = crista terminalis; svc = superior vena cava.
