The optimization of the pulmonary arteries (PA) size is an important concern after the bidirectional cavopulmonary connection (BDCPC) in patients with functionally univentricular heart as it precedes the completion of the Fontan program. We analyzed the PA growth between the time of the BDCPC and the time of the total cavopulmonary connection (TCPC) in a large monocentric cohort of children, and we explored the factors associated with differential growth profiles.

In total, 118 patients (median age at the BDCPC 8 months (IQR 5–18)) were included. Diameters of the right and the left PA were measured proximally to the first lobar bifurcation on the pulmonary artery angiography obtained before BDCPC and compared to angiographies obtained before TCPC. Nakata index was also calculated using these two measurements. Associations of pertinent covariables with the PA growth were explored.

Both pulmonary artery branches grew between BDCPC and TCPC (9.1mm of diameter (IQR 7.2–12.2) to 12.2mm (IQR 9.9–14.4) for right PA; P<0.0001, 8.5mm of diameter [db1] (IQR 6.5–7.3) to 9.6mm (IQR 8.0–12.4) for left PA; P=0.0001). However, PA branches growth was not proportional to child's growth as we noted a decrease of the Nakata index over this period. The main factor associated with a better PA branch growth was the presence of an additional pulmonary blood flow through a pulsatile antegrade flow (+28.2 mm² of section area for right PA; P=0.020, +16.8 mm² for left PA; P=0.043). No other factor preceding BDCPC or associated procedure performed simultaneously had an impact on PA branch growth.

PA branches growth is reduced after BDCPC and this may hamper the functioning of the future TCPC. Maintaining a pulsatile antegrade blood flow whenever possible could optimize PA growth and prevent deleterious early remodeling of the pulmonary vascular bed.