The Parasternal Short-Axis View Improves Diagnostic Accuracy for Inferior Sinus Venosus Type of Atrial Septal Defects by Transthoracic Echocardiography

Background: Sinus venosus defects (SVD) of the inferior vena cava (IVC) type, or inferior SVDs, are an uncommon form of atrial communication located outside the confines of the fossa ovalis and involve override of the IVC. Despite numerous studies describing the anatomical and echocardiographic features of the inferior SVD, distinguishing this defect from a large secundum atrial septal defect (ASD) by echocardiography is often challenging. Accurate diagnosis of an inferior SVD and correct differentiation from a secundum ASD is essential for appropriate presurgical planning. Absence of the posterior rim in the parasternal short-axis views may serve as a useful clue in diagnosing inferior SVDs. We sought to determine the utility of using the presence or absence of a posterior atrial rim in the parasternal short-axis view to help distinguish an inferior SVD from a secundum ASD. This sign may help clinch the diagnosis when subcostal imaging is suboptimal. Methods: We retrospectively reviewed transthoracic echocardiograms from 15 patients with a known surgical diagnosis of an inferior SVD between 2004 and 2015. The presence or absence of a posterior rim in the parasternal short-axis view was determined by two primary investigators. The posterior rim was also evaluated in 14 patients with a secundum ASD repair as controls. Echocardiograms were then reviewed blindly by attending-level echocardiographers and cardiology fellows in training. Diagnostic accuracy was assessed both with and without the use of the posterior rim criterion. Statistical analysis was used to determine the effect of using the rim criterion on inferior SVD diagnosis. We also reviewed all surgically diagnosed secundum ASDs that were incorrectly diagnosed as inferior SVD by preoperative imaging and determined whether use of the posterior rim criterion would have resulted in the correct diagnosis. Results: The posterior rim was absent in all 15 patients with a surgical diagnosis of inferior SVD and present in all 14 patients with a secundum ASD. For all observers, there was a statistically significant increase in diagnostic accuracy of inferior SVDs with the use of the rim criterion (P < .0001). We noted that secundum ASDs with inferior extension also have persistent posterior rims. The rim criterion correctly classified all large secundum ASDs with inferior extension that were previously misdiagnosed by echocardiogram preoperatively. Conclusions: Absence of the posterior rim ('' bald '' posterior wall) is a consistent finding in patients with an inferior SVD and distinguishes an inferior SVD from a large secundum ASD with inferior extension. Parasternal short-axis evaluation of the posterior atrial rim is a helpful tool for all levels of physician training in improving diagnostic accuracy for detecting inferior SVDs and in distinguishing them from secundum ASDs. (J Am Soc Echocardiogr 2017; 30: 209-15.)