Sinus venosus defects (SVD) are a rare form of congenital heart disease involving an interatrial communication outside the confines of the fossa ovalis. Although SVDs do not involve the atrial septum proper (i.e., the fossa ovalis and its surrounding muscular rim), they are placed in the same physiological category as atrial septal defects (ASD) and account for up to 11% of interatrial communications. SVDs of the inferior vena cava (IVC) type, or inferior SVDs, involve a deficiency in posteroinferior aspects of the atrial septum, resulting in a communication between the right and left atrial chambers through the mouth of the IVC. An intact fossa ovalis and the IVC straddling over the defect are considered additional prerequisites for diagnosing inferior SVDs. Anomalous pulmonary venous drainage to the IVC is a common finding and has been regarded by some investigators as an anatomical criterion for the diagnosis of inferior SVDs, whereas others have not included this feature as a diagnostic criterion because it is not present consistently.

In contrast to the secundum type of ASD, inferior SVDs are not amenable to transcatheter device closure and thus require surgical repair. The presence of an inferior SVD may also influence the specific placement of the IVC cannula prior to cardiopulmonary bypass. Previous studies have reported challenges with accurate preoperative diagnosis of inferior SVDs, with the defects often being mistaken for large secundum ASDs with inferior extension. While combination defects within the atria may be present, defining the posteroinferior rim anatomy itself has profound implications upon treatment strategy and overall hospital course. For example, Banka and colleagues found that misdiagnosis of inferior SVDs was associated with longer hospitalizations, a more complicated hospital course, and poorer technical outcomes.

The importance of presurgical diagnostic precision has resulted in the use of multiple imaging modalities including transesophageal echocardiography (TEE) and magnetic resonance imaging (MRI). Additionally, many studies have described transthoracic echocardiographic (TTE) findings to help facilitate diagnosis of inferior SVDs and their distinction from secundum ASDs. However, in these studies, the focus was upon the absence of an IVC rim in the subcostal sagittal views. Frequently in children, the subcostal coronal and sagittal views and many “in-between” views are obtained, along with methodical sweeping along a stack of planes in each view. This allows the diagnosis of SVDs by creating a mental three-dimensional (3D) picture of the position of the defect with respect to the IVC. However, this method also requires optimal images, which may be lacking in some older children and adults. Moreover, in adult echocardiography laboratories, such multiplanar subcostal imaging of the atrial septum is performed much less frequently. Previous studies have suggested that the parasternal short-axis view may demonstrate a deficiency in the posterior atrial rim.

Our aim was to determine whether an absent posterior atrial rim in the parasternal short-axis view was a consistent and reliable finding in all patients with inferior SVDs. We hypothesize that the identification of a “bald atrial wall,” seen in the absence of a posterior atrial rim in a parasternal short-axis view, is a consistent feature found in inferior SVDs, which will improve diagnostic accuracy.

Methods

We retrospectively reviewed the clinical data, echocardiography, and surgical notes from our surgical database for all patients between ages 0 and 18 years of age with a postoperative diagnosis of an inferior SVD at our institution over an 11-year time period, between January 2004 and February 2015. Subjects diagnosed with a secundum ASD who subsequently underwent surgical closure from the same time period were used as controls.

To be included in the study, patients must have had a full echocardiogram performed prior to surgical intervention. The minimal criterion for an inferior SVD defined for this study was an atrial communication originating at the mouth of the IVC with the IVC straddling the defect. The presence of anomalous pulmonary venous drainage was noted when present but not required to establish a diagnosis of inferior SVD. Our posterior rim criterion was defined as absence of a posterior atrial rim in the standard parasternal short-axis view (giving a “bald” appearance to the posterior atrial wall). This criterion was used to support the diagnosis of inferior SVD, while the presence of a posterior rim, even a rudimentary one, went against this diagnosis ( Figure 1 A–D). In some patients, a slightly modified parasternal short-axis view obtained by 20° counterclockwise rotation of the transducer was also available, as this view is frequently used in our institution to clarify the position of an ASD with respect to the IVC.

Anatomy and corresponding parasternal short-axis views of the atrial structures. (A) The components of the atrial septum are depicted in an en face view, highlighting the posterior and IVC rims. The position of the inferior SVD is shown by the dark shading . (B) Cartoon of the corresponding parasternal short-axis view of TTE. The absent posterior rim of the atrial septum creating the “bald” posterior wall of the left atrium is depicted by the two black arrows . (C) Parasternal short-axis view demonstrating absence of the posterior rim ( white arrow ) in a typical inferior SVD. (D) Similar parasternal short-axis view showing a secundum ASD with the presence of a tiny posterior rim ( white arrow ). FO , Fossa ovalis part of atrial septum is depicted by a circle; LA , left atrium; MPA , main pulmonary artery; RA , right atrium; RV , right ventricle; SVC , superior vena cava; TV , tricuspid valve.

Echocardiograms were reviewed by two investigators (B.S.S., A.B.) to determine the presence or absence of a posterior rim. We then sought to determine whether this particular echocardiographic finding would facilitate the accurate diagnosis of inferior SVDs. Echocardiograms were reviewed blindly by three separate attending physicians who were more than 8 years past their fellowship training and were dedicated echocardiographers. Echocardiograms were also reviewed by two first-year cardiology fellows who were at the end of their first year of training (fellows 1 and 2) and three second-year fellows (fellows 3, 4, and 5). Lastly, we performed a reverse analysis, and all the patients with a surgical diagnosis of secundum ASD who were incorrectly diagnosed as having an inferior SVD in preoperative echocardiographic report were identified and the presence of the posterior rim was determined by the investigators of this study. The study was approved by the Institutional Review Board of the Children’s Hospital of Philadelphia (IRB no. 14-011648).

Statistics

Descriptive statistics of the demographic factors were reported for the two groups of patients separately. Percentage of accurate diagnosis was calculated and reported. Determination of diagnostic accuracy was done by performing a logistic regression analysis and generating receiver operating characteristic (ROC) curve, and the area under the curve (AUC) was calculated as a measure of discriminatory power of the test. The values used for the predictor were either inferior SVD or secundum ASD. McNemars test was used to determine statistical significance of using the posterior rim criterion for inferior SVD diagnosis. A P value of <.05 was considered statistically significant.