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Describing congenital heart disease by using three-part segmental notation.

The segmental classification of congenital heart disease, first conceptualized nearly 50 years ago, is now well established. The Van Praagh classification system, in particular, is commonly used throughout North America to facilitate communication between physicians from various specialties who are involved in diagnosing and managing congenital cardiovascular abnormalities. In the Van Praagh system, a three-part notation consisting of letters separated by commas and encompassed by a set of braces is used to succinctly describe the visceroatrial situs, the orientation of the ventricular loop, and the position and relation of the great vessels. For example, the notation "{S, D, S}" describes the normal anatomic configuration, in which the morphologic right atrium and largest hepatic lobe are on the patient's right side and the morphologic left atrium, stomach, and spleen are on the left side (situs solitus); the ventricular loop is curved rightward (dextro- or d-loop); and the aorta is posterior to and rightward of the main pulmonary artery (situs solitus). Because the Van Praagh notation imposes on its users a systematic approach to anatomic description, it is a helpful device for structuring the interpretation of imaging studies as well as the reporting of results: First, the morphologic right and left atria and ventricles must be identified; next, the visceroatrial situs and ventricular loop orientation may be determined from the positions of the cardiac chambers; and last, the position and relation of the great vessels (normal, inverted, transposed, or malpositioned) can be established. The article provides concise, step-by-step guidance for applying the Van Praagh system in the radiology reading room.