Can the right atrium function as a hydraulic pump in Fontan circulation?

Can the right atrium function as a hydraulic pump in Fontan circulation?

Initially it was thought that right atrium can function as a hydraulic pump to drive the pulmonary circulation when an atriopulmonary anastomosis is made in Fontan surgery for tricuspid atresia. Later it became evident that the contractile function of the distended right atrium ceases at high pressures which are needed to drive the pulmonary circulation. This situation also increases the reservoir effect, causes blood stasis and creates the potential for atrial arrhythmias as a response to stretch. It was then that a cavopulmonary connection from the inferior vena cava to the pulmonary artery by an intra atrial conduit (lateral tunnel) or a totally extracardiac conduit were thought of and is now part of the total cavopulmonary connection (TCPC) [1].

TCPC is now an integral part of the Fontan type of univentricular repair for a whole lot of complex congenital cardiac lesions for which a biventricular repair is not feasible. The other component is a bidirectional Glenn shunt with end to side anastomosis of the superior vena cava to right pulmonary artery so that flow to both lungs is maintained. Earlier, when classical Glenn connected the superior vena cava to right pulmonary artery and an atriopulmonary anastomosis connected the inferior vena cava to left pulmonary artery (via the main pulmonary artery), 60% of the total blood flow used to go to the left lung with only 40% capacity.

Reference

1. J C Laschinger, J M Redmond, D E Cameron, J S Kan, R E Ringel. Intermediate results of the extracardiac Fontan procedure. Ann Thorac Surg. 1996 Nov;62(5):1261-7; discussion 1266-7.