A wide variety of congenital cardiac lesions lack two well-developed ventricles; from a functional standpoint, they are characterized by a single ventricular chamber that supports both systemic and pulmonary circulations. It is well established that the definitive palliation for these univentricular hearts is the Fontan circulation, whereby the pulmonary and systemic blood flow are placed in series with the single ventricle connected to the systemic circulation. To achieve the Fontan state, many patients need preliminary procedures, either to reduce or to augment pulmonary blood flow.
Definitions and Anatomic Considerations
A truly morphologic univentricular heart is rare; more often there is an additional rudimentary chamber. The most common type of single ventricle is tricuspid atresia, with an incidence of 1 to 3 percent of all congenital heart lesions. In tricuspid atresia there is no direct communication between the right atrium and the right ventricle, and often a dimple or localized fibrous thickening is found at the expected site of the tricuspid valve. The right atrium is large and an interatrial communication is always present. The right ventricle is hypoplastic and lacks an inflow portion, but its trabecular and outflow portions may be well developed. Tricuspid atresia is uniformly associated with other cardiac malformations. A ventricular septal defect (VSD) is usually present. The ventriculoarterial connection can be concordant or, less commonly, discordant (transposition of the great arteries); rarely, there is double-outlet right or left ventricle. Infundibular obstruction to pulmonary blood flow is often present, but this can also be observed at ...