New Insights into Sinus Venosus Defects from Cross-Sectional Imaging

Sinus venosus defects include two varieties, superior and inferior sinus venosus defects. The superior sinus venosus defect is characterized by abnormal communication between two closely related venoatrial structures: 1) the normally positioned superior vena cava-right atrium complex and 2) the right pulmonary vein-left atrium complex that is displaced leftward, forward and upward. Inferior sinus venosus defects primarily involve the inferior vena cava-right atrial junction while the right pulmonary vein-left atrial junction can also be affected. Because of the rarity and wide variation of the defects, the morphological characterization of sinus venosus defects is inconsistent among investigators and often inaccurate. Modern imaging technologies with high spatial and temporal resolutions have allowed accurate and detailed assessment of the pathological anatomy in larger numbers of cases. In this pictorial essay, we revisit the established and controversial features of the sinus venous defects using twodimensional (2D) and three-dimensional (3D) images obtained by magnetic resonance (MR) or computed tomography (CT) with brief discussion on imaging and treatment strategies.