Missing a Sub-pulmonary Ventricle: The Fontan Circulation

Abstract

A normal mammal cardiovascular system consists of a double circuit, pulmonary and systemic, connected in series and powered by a double chamber pump. In the absence of congenital heart disease, the right ventricle pumps through the pulmonary circulation and the left ventricle through the systemic circulation (Fig. 8.1a). Many complex cardiac malformations are characterized by the existence of only one functional ventricle (Fig. 8.2). This "single" ventricle has to maintain both the systemic and the pulmonary circulations, which during fetal life and at birth are not connected in series but remain in parallel (Fig. 8.1b). Such a circuit has two major disadvantages: diminished oxygen saturation of the systemic arterial blood and a chronic volume load of the single ventricle. The chronic ventricular volume load leads to a progressive ventricular dysfunction and remodeled pulmonary vascula-ture, causing a gradual attrition due to congestive heart failure and pulmonary hypertension from the third decade of life, with few survivors beyond the fourth decade. In 1971 Francis Fontan [ 1 ] from Bordeaux, France, reported a new approach to the operative treatment of these malformations, separating the systemic and pulmonary circulations. In a "Fontan circulation" the systemic venous return is connected to the pulmonary arteries without the interposition of a pumping chamber (Fig. 8.1c). In this construct, residual post-capillary transit energy is used to push blood through the lungs in a new portal circulation-like system [ 2 ]. Advantages of a Fontan circuit include (near-) normalization of the arterial oxygen saturation and abolishment of the chronic volume load on the single ventricle. However, because the pulmonary