Cardiac connections: the segmental approach to radiologic diagnosis in congenital heart disease.

The segmental approach to the diagnosis and classification of congenital heart disease, which emphasizes the importance of the connections (proximal-to-distal relationships) of cardiac chambers and great vessels, is presented. The radiologic identification of great vessels and cardiac chambers and their connections is described, considering, in turn, three major segments: the atria together with the systemic and pulmonary veins, the ventricles with their atrioventricular valves and the great arteries with their outflow tracts. Cardiac and great vascular connections can be described with greatest clarity by using the atria as the starting point. The atrial situs is defined as solitus, inversus or ambiguus, the great veins connecting to the atria normally or anomalously. The ventricles may be connected to the atria in concordant or discordant fashion or a double inlet ventricle may be present. The ventriculo-arterial connections can be classified as normal, transposition, double outlet right ventricle or double outlet left ventricle. The angiocardiographic techniques and criteria that differentiate these connection disorders and identify the transitional cases between them are discussed and illustrated. A complete diagnosis must indicate not only the connections of the three major segments but also the malformations and abnormalities of spatial position that may be present. Certain associations are of value in predicting the positions and connections of the cardiac chambers and great vessels, making it possible to formulate helpful rules to aid the progress of a diagnostic study. The fallibility of such rules is discussed, emphasizing the need to define connection disorders in terms of the connections rather than in terms of malformations or of abnormalities in spatial position of the individual parts.