Discussion:
There are several techniques to create confluence and enlarge the branch PAs. These include enlargement with autologous pericardium (fresh / pre-treated), bovine pericardium, Gore-Tex patch / tube, Dacron grafts, homografts and resection with direct end to end anastomosis1. However, all of these techniques have a high rate of restenosis which is largely attributed to extension of ductal tissue into the branch PAs, scarring, fibrosis and cicatrization of autologous pericardium2,3,4.
Our patient had an unusual presentation. Though the pulmonary arterial supply was sparse, the size of both the branch PAs at the hilum was generous. It is likely that the ductal flow during infancy and early childhood helped the growth of the branch PAs. Subsequently, the PDA gradually constricted along with the constriction of LPA origin resulting in progressive reduction of the pulmonary blood flow causing decreased effort tolerance and worsening cyanosis. Such late presentations are not uncommon in our part of the world.
The resection and end-to-end anastomosis or pericardial patch augmentation would have been conventional wisdom. Instead, we thought of recruiting the normal sized MPA which was lying in close proximity and had no clinical value. The pulmonary end of the transected MPA was turned down as an extension to create a tension free, tissue-tissue anastomosis between the branch PAs with the confluence. This was made possible due to the presence of a normal MPA above the atretic pulmonary valve. In order to avoid torsion while turning down the transected MPA towards the left hilum, two marker sutures were placed in opposing directions for identification after transection of MPA. Being native autologous tissue, it is resistant to infection and calcification, is free from autoimmune responses and has distensibility and potential for growth unlike other biological or prosthetic materials. However, the use of MPA to create a confluence is possible only in a select subset of patients with univentricular hearts or pulmonary atresia where it can be safely sacrificed as was the case in our patient.