Anomalous right pulmonary artery from aorta, surgical approach case report and literature review

Abstract Background: Anomalous origin of one pulmonary artery from the aorta is a rare congenital anomaly affecting the right pulmonary artery more than the left. These patients are at risk for the early development of significant pulmonary hypertension. Early surgical treatment has been proven safe with excellent results. The surgical approach and technique is challenging and should be decided ahead before the patient to surgery. Different techniques were described including direct reimplantation, conduit interposition, aortic ring flap. Aim: We present a neonate with anomalous origin of the right pulmonary artery from the aorta and discuss the surgical technique and complications in the literature.


| CASE PRESENTATION
Our patient is a newborn female baby, weighing 3.3 kg, who was admitted to our neonatal intensive care unit as a case of anomalous origin of the right pulmonary artery from aorta (AORPA).
She is a product of nonconsanguineous marriage and there is no history of congenital heart disease in the family. She was alert, well-perfused but tachypnoeic. Her oxygen saturation was 94%, her chest X-ray showed bilateral congested lungs. The echocardiogram ( Figure 1) showed anomalous origin of the right pulmonary artery, left pulmonary artery from the main pulmonary artery with moderate size patent ductus arteriosus. No interventricular septal defect with small patent foramen ovale.
Surgery was planned at Day 7 of life. However, the patient de-  almost systemic. The echo showed significant obstruction to the flow across the main pulmonary artery. The pulmonary artery confluence was compressed by the ascending aorta. We went back on bypass and the right pulmonary artery was disconnected from the main pulmonary artery and brought anterior to the aorta (LeCompte maneuver) to avoid repeated ischemic aortic cross-clamp. An autologous pericardial patch was used anteriorly to reconstruct RPA anastomotic site. This time the weaning off bypass was smooth with oxygen saturation of 100%, and pulmonary pressure of one-third systemic. We kept the chest open prophylactically due to long bypass. In the intensive care unit, the patient had a smooth postoperative course. The chest was closed the next day. The patient was extubated on Day 3 postoperatively and discharged on the 8th postoperative day. One month later the patient presented with tachypnea. Echocardiography showed RPA significant osteal stenosis and supra-aortic stenosis. RPA balloon dilatation was successful to reduce the pressure gradient. Aortic balloon dilatation was able to reduce the aortic mean pressure gradient from 90 to 40 mmHg ( Figure 4). The case was discussed and agreed to go for surgical repair of the supra-aortic and right pulmonary artery. During surgery, we found a significant intimal thickening in the supraaortic area at the anastomotic site. A longitudinal incision was made laterally on the ascending aorta extending from the non-  Lesions such as aortopulmonary window, or an anomalous origin of the right pulmonary artery from the aorta, are intrapericardial.
They are best explained on the basis of failure to close the embryonic aortopulmonary foramen, this in turn reflecting inadequate growth of the aortopulmonary septum from the dorsal wall of the aortic sac.
Failure of the latter process explains well why patients with an aortopulmonary window are frequently found with the right pulmonary artery arising from the aortic side of the window. Eccentric growth, but subsequent fusion, of the aortopulmonary septum with the distal ends of the outflow cushions, provides a plausible explanation for the origin of the right pulmonary artery from the ascending aorta. The separate origins of the aortic and pulmonary roots in this lesion point to the inadequacy of using the term ''hemitruncus'' for its description. 3 Anomalous right pulmonary artery from the ascending arota is four to eight times more common than anomalous origin of LPA from aorta. 5 F I G U R E 3 Operative view showing the reconstucted anomalous right pulmonary artery connected to the main pulmonary artery. Ao, aorta; AORPA, anomalous origin of the right pulmonary artery from aorta; PA, pulmonary artery; RA, right atrium; RV, right ventricle F I G U R E 4 Anteroposterior cath view showing supra-aortic stenosis at the site of anastomosis post repair AORPA is classified into two subgroups according to the morphological features: proximal and distal forms. In the proximal form, the anomalous pulmonary artery (PA) arises proximally from the posterior or left posterior aspect of the ascending aorta close to the aortic valve. About 85% AORPA is regarded as the proximal form in the report of Kutsche and Van Mierop. In the distal form, the anomalous PA originates from the ascending aorta just proximal to the innominate artery or from the base of the artery itself. 6 Furthermore, the site of origin of the pulmonary artery can be frequently, ipsilateral (right or left lateral) or less commonly posterior. 7 To diagnosis this anomaly, electrocardiography and chest X-rays are important, but echocardiography is essential because the abnormal vessel pattern can be seen on two-dimensional (2D) and Doppler examination. It is also important to distinguish this anomaly from discontinuous pulmonary arteries in which the blood supply to the left pulmonary artery originates from the major aortopulmonary collaterals or the ductus arteriosus. 8 Computed tomography scan or magnetic resonance imaging can confirm the diagnosis. Many centers have also used catheterization whether to measure the PA pressure or for anatomical delineation (see the table). In our case, the patient was diagnosed by echo. Table 1 shows the diagnostic tools used in different centers across the world. Catheterization was used mainly to measure pulmonary artery pressure and pulmonary vascular resistance.
DiGeorge syndrome is less common with hemitruncus anomalies as compared with other conotruncal malformations such as truncus arteriosus or interrupted aortic arch. 5 The most commonly associated anomaly is PDA. 6 This is evident in Table 1. to be as low as 30%. 2 Moreover, coronary ischemia, (steal syndrome), due to systemic diastolic blood flow to the anomalous pulmonary artery and PDA, has been reported. 10 Amir et al. discussed their experience with this anomaly and compared the pre and postoperative right ventricular pressure in these 12 patients. All but one patient had normal right ventricular pressure postoperatively. That patient had hypoplastic RPA supplied by closed PDA. Blalock-Taussig shunt was done to promote the RPA growth but the patient had a recurrent chest infection and high pulmonary pressure in the LPA and eventually died at 3 months after surgery when he was 5 months old. 12 Many centers have described their experience with this anomaly as case reports or case series. Table 1 summarize some of the published series with a special note on the number of cases, which side of pulmonary artery abnormal branching, the associated defects, the technique of repair, mortality and morbidity, and reintervention.

| Timing of surgery
Surgery should be offered as soon as the diagnosis is established.
Congestive heart failure, the development of progressive pulmonary vascular disease and early death can start as early as 3 months of age. Gupta et al. 17 reported a successful attempt to restore fetal circulation by the use of prostaglandin (PgE1), aiming to open the ductus and decompress the right ventricle as a temporary bridge to preparation for corrective surgery. Surgical correction in the neonatal period provides excellent short-and long-term outcomes. The neonatal correction has increased dramatically over the past two decades. 4,9 Moreover, repair in a preterm 1.6 kg, 34-week-gestation baby has been reported. 18 Adults presentation has been reported and surgery was abandoned due to the high risk related to the severe pulmonary hypertension. Yet, successful repair has been reported in adults. [19][20][21] The presence of associated complex cardiac defect increases the risk of surgery and should be assessed individually.

| Surgical technique
Historically PA banding, PDA ligation alone, or PDA ligation with ligation of the RPA were described and were unsuccessful. 22 Penkoske and associates reported that the mortality of this malformation with palliative operation including ligation of the anomalous RPA, ligation of the patent ductus arteriosus, or PA banding reached 82%. 23

| Cardiopulmonary bypass conduct
Aortic cannulation should be done as distal as possible, some surgeons advise doing it in the aortic arch to give enough length in the ascending aorta for cross-clamp and aortic reconstruction. Although there is no technical reason to use deep hypothermia with either low flow cardiopulmonary bypass (CPB) or circulatory arrest, some surgeons prefer it. The branch pulmonary arteries are exposed and temporarily occluded with either nontraumatic microvascular clips or Silastic snares immediately after CPB is established to prevent flooding the lungs. 24 If an aortic cross-clamp is applied the anomalous pulmonary artery is kept occluded while giving the cardioplegic solution to arrest the heart. Many methods have been described depending on the site of origin of the anomalous pulmonary artery.   Table 1 shows that this was the most common method used in different centers. The technique is to use a graft conduit (e.g., Dacron Woven conduit) to fill the space between the RPA and MPA. 22 The drawback is that the patient will outgrow the conduit and will need reintervention.
3. Use of aortic ring to elongate the RPA (single aortic flap technique) (Figure 7): The ascending aorta is transected just above and below the origin of the AORPA to form an aortic ring, which is used to elongate the anomalous RPA. The RPA, aorta, and branches should be adequately mobilized. The aorta is then reconstructed anterior to the RPA as an end-to-end anastomosis. 29 There is always a risk of compression of the aorta on the pulmonary artery especially if it originates laterally. In that case, LeCompte maneuver with generous dissection of the ascending aorta and its neck branches in addition to the branch pulmonary arteries bilaterally might be useful. making the RPA away from the MPA. However, we did not use the LeCompte maneuver initially until we had to go back on bypass as we found the right ventricular pressure is almost systemic due to obstruction in the main pulmonary artery flow related to the ascending aortic compression. After the LeCompte maneuver, the right ventricular pressure went down dramatically after that with smooth weaning off bypass. This could be related to the amount of tissue resected from the ascending aorta which can shorten it, and make it easy to compress the underneath right pulmonary artery to pulmonary artery anastomosis.
Hospital mortality has been reported as anywhere from 0% to 21%, and the need for reintervention, 12.5% to 36%. 2,10,32,33 Table 1 shows the mortality in different centers experience with the cause of death detailed.
Echocardiography is useful in the postoperative follow-up. Catheterization can be performed to further diagnose or treat any residual lesion when needed.
Our patient developed RPA osteal stenosis and needed balloon dilatation at 1 month of age. This could be related to the fact that the anastomosis was repeated to do the LeCompte maneuver. She also developed stenosis at the site of aortic anastomosis. The Balloon dilatation was not successful enough for that and the patient was sent for surgical repair when she was 5 months old.
Nathan et al. reported the complication of supra-aortic stenosis postoperatively. 2 Kajihara et al. recommended the augmentation of the aortic root defect with a patch whenever even slight supra-aortic stenosis is suspected. 6 In our patient, the ascending aorta was small and due to some tension, we have added extra stitches to control the bleeding. This could be the cause of supra-aortic stenosis in our patient. During surgery, we found a significant intimal thickening from within although the anastomosis did not show any hourglass appearance from outside.

| CONCLUSION
We conclude that the anomalous origin of one pulmonary artery is a dismal but surgically correctable disease. Careful diagnosis and timing of the operation is of utmost importance as pulmonary hypertension can start early in life. The surgical technique has to be planned preoperatively depending on the site of origin of the branch pulmonary artery from the aorta. Direct implantation is the commonest method used in the literature unless there is a lateral origin of the branch PA, which mandate different technique like patch augmentation or aortic ring. The use of an aortic ring with pulmonary artery anterior flap, flipping it as a posterior wall of the anastomosis, is a useful technique when the RPA originate from the right anterolateral aspect of the ascending aorta. LeCompte maneuver, with good branch pulmonary arteries peripheral dissection to the second bifurcation, is a useful technique to avoid direct compression of the ascending aorta on the anastomosis when using this technique.