Effect of pulmonary conduit oversizing on hemodynamics in children

Implanting the largest valved conduit possible - oversizing - to reconstruct an absent connection from the right ventricle to the pulmonary artery in certain types of congenital heart defects has been suggested as a compensating measure for somatic outgrowth of the patient. However, one effect that has not been investigated yet is the hemodynamic consequence. For this purpose, virtual implantation and flow simulations were conducted in this study.

To isolate the effects of conduit oversizing on the hemodynamics observed after conduit implantation and outgrowth, calculated wall shear stresses (WSS) of image-based computational fluid dynamic (CFD) simulations were used as indicators. Three different sizes of valved conduits (20 mm, 22 mm, and 24 mm), including the largest possible conduit size, virtually implanted in a child-sized healthy pulmonary artery and the corresponding adult-sized model were investigated.

The child and adult models show a decrease of the mean WSS (approx. 26%) in the whole domain with an increase of the conduit size. When looking at the mean WSS at the anastomosis, for the child model the WSS is significantly increased (approx. 40%) when oversizing (Z-score +3.21). In contrast, the stresses are decreased for the adult model (34%) when using the largest conduit (Z-score +0.25).

Based on the results of this study, it must be considered that choosing a prosthesis size that will lead to high WSS and an associated intimal reaction, possibly leading to stenosis, can defeat the benefit of having a nominally larger orifice area directly after implantation.