Notwithstanding the controversies evoked by the term “single ventricle”, most patients with this condition would undergo the Fontan procedure. In addition, there is a large group of patients in whom a biventricular repair would be abandoned in favour of a univentricular one because of the presence of unfavourable morphologic features. There is a need for a uniformly acceptable system of nomenclature that would permit precise description and classification of hearts with complex malformations to facilitate reporting and help in understanding the reasons for choosing a univentricular repair.

Echocardiographic, angiographic and operative records of 240 patients undergoing the Fontan procedure were analysed.

Out of the 104 patients with univentricular atrioventricular connections, 2 ventricles were discernible in all but 3 patients. A Fontan repair was performed in 136 patients with biventricular atrioventricular connections because of the presence of a hypoplastic ventricle in 52 patients and a non-committed ventricular septal defect in the remaining 84.

The Fontan operation is probably the only definitive treatment option for patients with univentricular atrioventricular connections. The decision to perform a univentricular repair in preference to a biventricular one in hearts with biventricular atrioventricular connections is based on the presence of a hypoplastic ventricle or a non-reroutable ventricular septal defect. This decision is subjective. In hearts with discordant atrioventricular connections and pulmonary stenosis, we prefer the Fontan operation to the classical repair.