Segmental approach to imaging of congenital heart disease.

The segmental approach, which is widely used in the imaging work-up of congenital heart disease, consists of a three-step evaluation of the cardiac anatomy. In step 1, the visceroatrial situs is determined. Visceroatrial situs refers to the position of the atria in relation to the nearby anatomy (including the stomach, liver, spleen, and bronchi). Three different anatomic configurations may be observed: situs solitus (normal), situs inversus (inverted), or situs ambiguus (ambiguous). In step 2, the left- or rightward orientation of the ventricular loop is evaluated, and the positions of the ventricles are identified on the basis of their internal morphologic features. In step 3, the position of the great vessels is determined first, and any abnormalities are noted. Abnormalities in the origin of the great vessels, or conotruncal anomalies, are predominantly of three types: D-transposition (dextrotransposition), L-transposition (levotransposition), and D-malposition with double outlet right ventricle. Next, the relationships between the atria and ventricles and the ventricles and great vessels are determined at two levels: atrioventricular (concordant, discordant, ambiguous, double inlet, absence of right or left connection) and ventriculoarterial (concordant, discordant, double outlet). Last, a search is performed for any associated abnormalities of the cardiac chambers, septa, outflow tract, and great vessels. By executing these steps sequentially during image review, the radiologist can achieve a more accurate interpretation. Multiplanar reconstructions of cross-sectional image data obtained with computed tomography or magnetic resonance imaging are particularly useful for evaluating congenital heart disease.