Sequential segmental analysis in complex fetal cardiac abnormalities: a logical approach to diagnosis.

Cardiac abnormalities are common. A wide spectrum of lesions can be encountered in the child and fetus. Complex abnormalities are over-represented in prenatal series as these may be more readily recognized during routine anatomical surveys. While the diagnosis of ‘simple’ defects such as pulmonary stenosis or an isolated ventricular septal defect in an otherwise normally connected heart is usually considered straightforward, the description and understanding of the infinite variety of ‘complex’ cardiac abnormalities may be perceived as a difficult task. It need not be so. Sequential segmental analysis offers a step-by-step approach to describing the cardiac anatomy in different malformations and leads to a thorough appreciation of its pathophysiology. This approach was developed and disseminated in the late 1970s and early 1980s1–3 and is based on the concept that all heart malformations can be readily analyzed with reference to three basic segments4–6. ‘Complex’ congenital heart anomalies become simple when approached in a logical fashion. Knowledge of cardiac embryogenesis is unnecessary to describe the anatomy of the heart after 8 weeks’ gestation. All hearts, normal or malformed, are made up of three segments: atria, ventricles and great arteries (Figure 1). In sequential segmental analysis, the cardiac segments (i.e. the morphologically right and left atria, the morphologically right and left ventricles and the great arteries) are identified separately based on their most consistent anatomical features, not their spatial orientation. The atria are separated from the ventricles at the level of the fibrous tissue plane of the valves at the atrioventricular (AV) junction. The ventriculoarterial junction is marked by the attachment of the arterial valves to the ventricular mass. Atrial situs is established first by determining the position of each atrium in relation to each other within the chest and the AV and ventriculo-arterial connections ascertained. Atria Arterial trunks