Impact of right ventricle-pulmonary artery conduit placement on pulmonary artery development after the Norwood procedure in hypoplastic left heart syndrome

The right ventricle-to-pulmonary artery (RV-PA) shunt in the Norwood procedure (NP) for children with hypoplastic left heart syndrome (HLHS) provides stable haemodynamics and improves interstage survival. The aim of the study was to find the effect of RV-PA placement on pulmonary artery development after the NP. A prospective, randomized study of 60 children with HLHS was carried out between 2008 and 2010. All children underwent the NP in the neonatal period and survivors underwent the hemi-Fontan operation (at a mean age of 4.78 +/- 2.8 months). RV-PA was left side to the neo-aorta in 32 children (the first group) and right side to the neo-aorta in 28 children (the second group). Echocardiography and angiograms were used to asses the pulmonary artery size. There was a significant difference between right pulmonary artery (RPA) and left pulmonary artery (LPA) diameters in both groups before the NP (first: 4.94 +/- 0.27 vs. 4.26 +/- 0.22, P = 0.04; second: 4.97 +/- 0.23 vs. 4.14 +/- 0.17, P = 0.003). This difference was not significant when z-scores were taken into account. The dynamics of the pulmonary artery development was similar in both groups comparing pre-Norwood and pre-hemi-Fontan periods. A slight increase in the LPA and the RPA diameter with a significant decrease in the z-scores was noted. At the pre-hemi-Fontan stage, there was no significant difference in the diameter and the z-score between LPA and RPA in the second group, whereas in the first group, the z-score for LPA was significantly lower compared with RPA (-1.34 +/- 1.6 vs. -0.86 +/- 1.4, P = 0.016). Placement of the RV-PA conduit on the right side to the neo-aorta ensures more equal distribution of the blood to the pulmonary arteries and better development of the LPA.