based on the revolutionary concept of the dispensable right ventricle, the fontan operation stands as the extreme example of physiologic repair in pediatric cardiac surgery, serving as the common surgical denominator for the entire spectrum of functionally univentricular conditions. also called ortho-terminal repair, it makes allowance for a circulatory arrangement that is in-series by effectively driving the pumpless systemic venous return directly through the pulmonary circulation. if this arrangement is to work, then two conditions must be fulfilled. first, there must not be any anatomical or functional hindrance along the whole fontan pathway, from the caval venous inflows to the aortic outflow. second, there must be a well-suited systemic pump, essentially recruited to the dual function of drawing blood from and, simultaneously, driving blood through, the lungs. this latter function, driving the blood through the lungs, takes place during the venous phase of the systemic output.