Diagnosis of Inferior Sinus Venosus Atrial Septal Defects Using Transthoracic Three-Dimensional Echocardiography Chun-An Chen, MD, Jou-Kou Wang, MD, PhD, Jui-Yu Hsu, MD, Hsao-Hsun Hsu, MD, Shyh-Jye Chen, MD, PhD, and Mei-Hwan Wu, MD, PhD The authors report the cases of 2 patients with symptoms and signs related to severe pulmonary hypertension. Two-dimensional echocardiography demonstrated defects in the posterior portion of the atrial septum. Trans- thoracic three-dimensional echocardiography clearly showed inferior sinus venosus atrial septal defects and their relationships with the inferior vena cava, the pulmonary vein, and the muscular border of the fossa ovalis. These 2 cases not only elucidate the potential value of transthoracic three-dimensional echocardiography in delineating the structural characteristics of unusual interatrial shunting but also remind clinicians to be aware of this potentially treatable cardiac defect during workup for pulmonary hypertension. (J Am Soc Echocardiogr 2009;23:457.e4-e6.) Keywords: Sinus venosus atrial septal defect, Pulmonary hypertension, Three-dimensional echocardiography CASE 1 A 35-year-old woman with a history of primary pulmonary hyperten- sion was referred to our clinic because of progressive exercise into- lerance. Transthoracic two-dimensional (2D) echocardiography revealed an interruption in the posteroinferior aspect of the atrial sep- tum, but detailed anatomical localization was difficult (Figure 1A, Video 1). Color Doppler echocardiography showed a shunt through this defect (Figure 1B). Transthoracic three-dimensional (3D) echocar- diography was performed (Philips iE33; Philips Medical Systems, Andover, MA) with an X-3 matrix-array transducer. Three-dimen- sional echocardiographic images cropped from the lateral aspect of the right atrium toward the atrial septum showed a large atrial septal defect (ASD) directly communicating with the orifice of the inferior vena cava (IVC); the muscular border of the fossa ovalis remained in- tact (Figure 1C, Video 2). An inferior sinus venosus ASD was diag- nosed. Multidetector computed tomography showed similar findings (Figures 1D and 1E). Right-heart catheterization revealed se- vere pulmonary hypertension (pulmonary arterial pressure, 86/45 mm Hg; mean pressure, 62 mm Hg; pulmonary vascular resistance, 19.2 Wood units). Inhalation with 100% oxygen for 10 minutes failed to decrease pulmonary arterial pressure significantly. The patient was treated with sildenafil and awaits heart-lung transplantation or lung transplantation with concomitant intracardiac repair. CASE 2 A 48-year-old man presented to his local hospital because of progres- sive dyspnea. A systolic murmur was heard during auscultation, and echocardiography showed a large, secundum-type ASD. He was referred to our hospital for attempted transcatheter closure of this de- fect. However, 2D and color Doppler echocardiography before car- diac catheterization showed that the ASD involved the posterior aspect of the atrial septum (Figure 2A). Transthoracic 3D echocardio- graphic images confirmed the diagnosis of an inferior sinus venosus ASD; overriding of the atrial septum by the IVC was clearly demon- strated when viewed from the orifice of the IVC toward the roofs of atria (Figures 2B and 2C, Videos 3 and 4). Furthermore, 3D echocar- diographic images also showed overriding of the orifice of the right lower pulmonary vein across the atrial septum. Multidetector com- puted tomography confirmed the diagnosis of inferior sinus venosus ASD (Figures 2D and 2E); overriding of the right lower pulmonary vein across the atrial septum was also found (Figures 2E and 2F). Right heart catheterization revealed significant left-to-right shunt (Qp/Qs = 2.2) with ulmonary hypertension (pulmonary arterial pressure, 53/21 mm Hg; mean pressure, 37 mm Hg; pulmonary vascular resistance, 4.3 Wood units). Surgical repair of the ASD was recommended. DISCUSSION Sinus venosus ASD accounts for only 10% of ASDs and is commonly associated with partial anomalous pulmonary venous return. 1 The de- fect is posterior to the fossa ovalis area and is called a superior sinus venosus ASD if there is an absence of the superior border or an infe- rior sinus venosus ASD if the inferior border is deficient. 1 The key to diagnosis is the presence of overriding of the IVC across the intact atrial septum and the defect outside the confines of the fossa ovalis area. 2 However, accurate diagnosis by echocardiography remains a challenge. Two-dimensional echocardiography might reveal an ASD with an unusual location, raising the suspicion of sinus venosus From the Departments of Pediatrics (C.-A.C., J.-K.W., M.-H.W.), Surgery (H.-H.H.), and Medical Imaging (S.-J.C.), National Taiwan University Hospital, Taipei, Taiwan; and the Department of Pediatrics, Buddhist Tzu-Chi General Hospital, Taipei Branch, Taipei, Taiwan (J.-Y.H.) Reprint requests: Chun-An Chen, MD, Division of Pediatric Cardiology, Depart- ment of Pediatrics, National Taiwan University Hospital, No 7, Chung-Shan South Road, Taipei 100, Taiwan (E-mail: chenca@ntu.edu.tw). 0894-7317/$36.00 Copyright 2009 by the American Society of Echocardiography. doi:10.1016/j.echo.2009.09.008 457.e4