Atrial situs may be solitus, inversus, or ambiguus with bilateral right or left morphology. The type of atrioventricular (AV) connection is, by definition, univentricular. The mode of connection may be double-inlet, absent left, or absent right AV connection. In double-inlet connection, the two atria may be connected to the ventricle by two separate AV valves or via a common valve. Usually, the two AV valves do not have typical characteristics of mitral and tricuspid valves and therefore are termed right and left on the basis of the anatomic location of the atrium to which they are connected.

In descriptive morphologic terms, a complete ventricle may have inlet, apical trabecular, and outlet components. Usually, the apical trabecular portion can be used to classify a chamber as being of right or left morphology. In the morphologically right ventricle, the apical component has characteristic coarse trabeculations. In contrast, the apical component of the morphologically left ventricle has much finer crisscrossing trabeculations and a smooth septal surface.

When two chambers are found within the ventricular mass, one has a right and the other a left ventricular apical trabecular component. Usually, the ventricle receiving the AV valve or valves is larger and is termed the dominant ventricle. The other ventricle is described as nondominant, or rudimentary. Usually, the nondominant ventricle is small, but size varies. Outlet chamber and trabecular pouch describe a nondominant ventricle with and without an outlet component, respectively.

The spatial relation of the two ventricles is an important variable and must be specified. It has been designated by various authors as D– or L-loop, right– or left-hand ventricular architecture, and noninverted or inverted ventricles. When two ventricles are present, the communication between them properly is termed a ventricular septal defect (VSD). The terms outlet foramen and bulboventricular foramen also have been used to describe the VSD.

If two great vessels are present, the ventriculoarterial connection may be concordant, discordant, or double-outlet. A single-outlet connection may be present with a common arterial trunk or with aortic or pulmonary atresia.