Anomalous origin of right pulmonary artery from innominate artery: Repair using pulmonary artery pedicled flap plasty.

Origin of the right pulmonary artery from innominate artery is an exceedingly rare anomaly. We report two cases with this anomaly that underwent surgical repair. The surgical technique described achieves tissue-to-tissue anastomosis using a pedicled flap from the main pulmonary artery.

INTRODUCTION

Anomalous right pulmonary artery (RPA) from innominate artery in the presence of normal origin of the left pulmonary artery is exceedingly rare. This report focuses on a novel surgical technique employed in two cases with this anomaly.

PATIENT 1

A 12-day-old male child weighing 2.8 kg presented with DiGeorge syndrome confirmed by the fluorescence in situ hybridization test. Echocardiography confirmed Type B aortic interruption and a perimembranous ventricular septal defect. Further, the RPA was found to arise from the innominate artery through a stenotic orifice measuring approximately 2 mm at origin and 4 mm at the hilum. The infant was scheduled for surgical repair. Through median sternotomy, an 8 F DLP cannula inserted through a 3.5 mm tube graft of polytetrafluoroethylene (PTFE) anastomosed to the innominate artery and another DLP cannula of similar diameter inserted through the ductus arteriosus were used to perfuse the upper and lower body, respectively. Cardiopulmonary bypass (CPB) was commenced using bicaval venous cannulae. During the cooling process, the RPA was disconnected from its origin at the innominate artery. It was dissected into the hilar portion to achieve the area with the widest diameter. The left pulmonary artery was also mobilized widely into the hilar portion. At deep hypothermia, cardioplegic arrest was achieved. The aortic interruption was first repaired by direct anastomosis of distal segment to proximal aorta. Antegrade cerebral perfusion was maintained for the duration of the repair, thereby avoiding circulatory arrest. The ventricular septal defect was then closed through the right atrial approach using a patch of expanded PTFE of appropriate dimensions. Following this, attention was directed to the RPA. The proximal three quarters of this vessel was of poor caliber and had to be excised. This left only the portion immediately proximal to the branching portion of satisfactory quality to include in the repair. The vessel was found to be of inadequate length to reach the main pulmonary artery. The aorta was transected to gain better exposure. A posteriorly based transverse pedicled flap was created from the anterior wall of the main pulmonary artery. This flap of pulmonary artery wall when turned medially and to the right reached the RPA without tension. The flap was sutured to the RPA using 7 0’ polypropylene, thereby creating the posterior wall of the neo RPA. The anterior wall of the distal RPA was then incised longitudinally into the hilar portion to gain the widest caliber. A previously harvested and glutaraldehyde-treated (0.625% for 5 min) patch of autologous pericardium was then used to reconstruct the anterior wall of the neo RPA. This created a wide stoma of the RPA from the main pulmonary artery. The transected aorta was reanastomosed. The perfusate was rewarmed and the child was weaned off CPB uneventfully. CPB and aortic cross clamp (ACC) times were 280 and 180 min respectively. The antegrade cerebral perfusion time was similar to the CPB time since the cannula in the innominate artery was used for arterial perfusion for the entire duration of the procedure. Irradiated blood was not used despite the child having proven DiGeorge syndrome due to restrictions in blood bank resources. Needle pressures were checked along the pulmonary arterial pathway, and significant gradients were excluded.

PATIENT 2

A 3-month-old female child weighing 2.3 kg was admitted with failure to thrive. Investigations revealed discontinuous RPA in the presence of normal main and left pulmonary arteries. In addition, there was a moderate-sized persistent ductus arteriosus shunting right to left signifying severe pulmonary arterial hypertension. A small interatrial communication (patent foramen ovale) was also present shunting bidirectionally. There were no other intracardiac anomalies. Cardiac catheterization revealed suprasystemic pulmonary arterial pressures in the left pulmonary artery. Anatomic details were confirmed by computed tomography [Figure 1]. Through median sternotomy, a similar repair strategy as described above was performed for the anomalous RPA with the exception that a single aortic cannula was inserted through the distal aorta and a single venous cannula was used for venous drainage [Figures 2 and 3]. CPB and ACC times were 168 and 94 min, respectively. Needle pressures measured at the completion of the repair showed significant lowering of pulmonary arterial pressures and pulsatile flows in the reconstructed RPA. The child made an uneventful recovery. Postoperative echocardiography showed good flows in the RPA [Figure 4].

Figure 1

Three-dimensional reconstructed computed tomography image of anomalous right pulmonary artery arising from innominate artery

Figure 2

Operative photograph showing anomalous origin of the right pulmonary artery from the innominate artery

Figure 3

Operative photograph showing pedicled flap of main pulmonary artery turned medially to reach the right pulmonary artery

Figure 4

Postoperative color Doppler echocardiogram showing flows in the reconstructed right pulmonary artery

Patient 1, on his first follow-up at 2 months, was found to have significant narrowing at the midsegment of the reconstructed RPA, posterior to the ascending aorta. This was corrected by a transcatheter stent deployment. He is currently on follow-up 1½ years after the procedure and has normal flows in the reconstructed RPA on echocardiography.

COMMENT

Anomalous origin of RPA from innominate artery is extremely rare. Isolated case reports have been published without details of surgical repair.[12] We first published the technique of pulmonary artery flap plasty that was employed in the first of these two patients.[3]

Early absorption of the proximal right sixth arch with persistence of the distal right sixth arch and its connection to the right dorsal aorta forms the embryological basis of this anomaly.

The proximal portion at the origin of the RPA is usually stenotic and resembles ductal tissue. It is imperative to excise all these abnormal tissues to achieve satisfactory flows into the RPA following reconstruction. Wide mobilization of the RPA and left pulmonary artery is required to achieve a tension-free anastomosis. It is also necessary to divide the ductus arteriosus in the process. The main pulmonary artery is usually enlarged in these patients. Hence, it permits creation of a wide flap with adequate length to reach the hilum of the right lung. Transecting the aorta will facilitate the anastomosis of the flap to the distal RPA. Once the posterior wall has been reconstructed with autologous living tissue, growth potential can be assured. Tissue-to-tissue anastomosis may promote growth potential and decrease the chances of thrombotic occlusion following other interventions in the future. The autologous-treated pericardium can then be used to reconstruct the anterior walls of both the RPA and the main pulmonary artery from which the flap was raised. Pulmonary homograft tissue may also be a material of choice for this reconstruction. However, the author prefers autologous-treated pericardium due to its better handling properties and satisfactory results for similar reconstructions.

In the second patient, pulmonary arterial pressures dropped significantly following the repair due to redistribution and resumption of adequate flows into the reconstructed RPA.

The first patient developed narrowing at the mid-portion of the reconstructed RPA. This was probably due to a larger pericardial patch used to reconstruct the anterior wall of the vessel, causing the patch to buckle into the lumen. However, since there was native tissue in continuity, it was possible to stent the vessel and reestablish normal flows.

CONCLUSION

Pulmonary artery pedicled flap plasty is an easily reproducible and effective surgical technique for repair of anomalous origin of RPA from innominate artery. Establishing native tissue anastomosis permits future interventions should the need arise.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.