Anomalous origin of branch pulmonary artery from the aorta: Current challenges in the management

ABSTRACT

Anomalous origin of a branch pulmonary artery from the aorta is a rare congenital anomaly that requires early surgery to prevent pulmonary vascular disease. The rate of reintervention after surgery remains high. Many aspects of the management could be improved such as assessment of operability in late presenters, selection of suitable surgical technique in each case, and prevention of anastomotic complications. We report the series of 10 patients who were operated for this anomaly. We aim to focus on the current challenges in the management of this condition.

INTRODUCTION

Anomalous origin of branch pulmonary artery from the aorta (AOPA) is a very rare condition in which the patients develop severe pulmonary vascular obstructive disease as early as the 3^rd month of life, with an estimated 1-year survival of 30%, if left untreated.[1,2] Nearly 300 cases of AOPA have been reported worldwide in the English literature.[3] The rate of re-intervention after surgery still remains high, and many aspects of management could be refined.

We report the series of 10 cases of AOPA, managed at our institute over a period of 5 years. This series aims to share our experience and focus on the current challenges in the management.

MATERIALS AND METHODS

A retrospective search of the hospital records between January 2017 and December 2022 revealed 10 patients with AOPA who presented to the department of cardiac surgery in our hospital. The patients were evaluated preoperatively using echocardiography [Figure 1], and a computed tomography (CT) scan was done only if additional anatomical information was required [Figure 2].

Figure 1.

Trans-thoracic echocardiogram showing modified parasternal long axis view with anterior sweep; (a) Two-dimensional echocardiographic view showing anomalous right pulmonary artery from aorta, (b) Color Doppler study showing the blood flow in the anomalous right pulmonary artery

Figure 2.

Cardiac computed tomography scan showing anomalous left pulmonary artery from aorta; (a) Three-dimensional reconstruction, (b) Axial view

Median sternotomy, cardiopulmonary bypass (CPB) using distal aortic and bicaval cannulation, and cold blood anterograde cardioplegia were used in all cases. AOPA was clamped using a microvascular clip on CPB and during cardioplegia delivery. AOPA was excised from the aorta and directly reimplanted to the main pulmonary artery (MPA) in all cases but one. The latter had distal origin of the anomalous right pulmonary artery (RPA) and a double-flap technique, consisting of an anteriorly based aortic flap and posteriorly based MPA flap, was used to elongate the RPA before it was anastomosed to MPA in front of the aorta. The defect on the aorta was closed either directly or using a pericardial patch. Concomitant cardiac anomalies were repaired simultaneously.

The patients were followed up at regular intervals with clinical and echocardiographic evaluation, with an emphasis on anastomotic site gradient. Descriptive statistical methods were used for the analysis of study parameters.

RESULTS

The median age of the study group was 3.5 months (1–12 months). The mean weight of the study group at operation was 4.22 ± 1.28 kg. Table 1 shows patient and surgical details. The mean CPB time and the mean cross-clamp time were 80.0 ± 19.54 min and 52.75 ± 16.52 min, respectively, for isolated AOPA, and these were 184.75 ± 61.15 min and 84.25 ± 8.61 min, respectively, for AOPA associated with major other cardiac lesions. The mean duration of ventilator support was 1.90 ± 1.37 days. The mean duration of intensive care unit and hospital stay was 6.10 ± 2.04 days and 8.71 ± 1.48 days, respectively.

Table 1.

Demographic, anatomical, and surgical data and outcomes

Age (months)	Sex	Weight (kg)	Side of anomalous PA and site of origin from aorta	Side of the arch	The side of the ductus	Procedure for anomalous PA	Closure of the aortic defect	Complications	Outcomes
5	Male	4.5	Right Proximal Posterolateral	Left	Left	Direct reimplantation	Direct	Seizure	Alive
1	Female	3	Right Proximal posterolateral	Left	Left	Direct reimplantation	Pericardial patch closure	DIC, pulmonary hemorrhage	Died
9	Female	5.3	Right Proximal posterolateral	Left	Left	Direct reimplantation	Direct	Nil	Alive
3	Female	3.6	Right Proximal Posterolateral	Left	Absent	Direct reimplantation	Direct	Nil	Alive
2	Female	3	Right, distal	Left	Left	Double flap technique	Pericardial patch closure	Sepsis	Died
3	Male	3.4	Left, anterolateral aspect	Right	Right	Direct reimplantation	Pericardial patch closure	Nil	Alive
12	Female	7.2	Left, lateral aspect	Right	Right	Direct reimplantation with anterior pericardial patch augmentation	Pericardial patch closure	Nil	Alive, peak anastomotic gradient - 30 mm of Hg
6	Male	4.5	Left, lateral aspect	Right	Right	Direct reimplantation	Direct	Nil	Alive
4	Male	4.2	Right Proximal Posterolateral	Left	Left	Direct reimplantation	Direct	Nil	Alive
3	Female	3.5	Left, lateral aspect	Left	Absent	Direct reimplantation	Direct	Nil	Alive

PA: Pulmonary artery, DIC: Disseminated intravascular coagulation

Two patients died after surgery (20%). One patient was a neonate with complex congenital heart disease who had anomalous origin of RPA from aorta (AORPA), Type A interrupted aortic arch, aorto-pulmonary window, and a large patent ductus arteriosus (PDA). Complete surgical correction was done with the help of total circulatory arrest. However, the patient developed disseminated intravascular coagulation and pulmonary hemorrhage which caused death on the day of the surgery. The other patient was a case of distal AORPA who expired on day 9 due to sepsis [Table 1].

The median duration of the follow-up was 2.5 years (6 months–5 years). All patients were alive and asymptomatic on follow-up. One patient had left pulmonary artery (LPA)-MPA anastomotic peak gradient of 30 mmHg on echocardiogram at 12 months postsurgery, and CT revealed mild anastomotic narrowing. This patient is asymptomatic and is under close follow-up.

DISCUSSION

AOPA is a rare congenital cardiac anomaly, accounting for only 0.1% of all congenital heart diseases.[1] AORPA is 4–8 times more common than the left anomaly.[4] Fifteen percentage of cases of AORPA arise distally near the origin of the innominate artery [Figure 3].[5] This variant requires more extensive mobilization and utilization of conduits or flaps for reimplantation. Anomalous LPA from aorta (AOLPA) usually has a shared vessel wall with underlying MPA which should be excised during re-implantation [Figure 4].[4]

Figure 3.

Anomalous origin of the right pulmonary artery from distal ascending aorta (arrow)

Figure 4.

(a) Anomalous origin of the left pulmonary artery from the ascending aorta with a shared posterior wall with the main pulmonary artery (arrow), (b) left pulmonary artery disconnected from the ascending aorta and the posterior common wall excised to open the left pulmonary artery widely (arrow); Suction placed inside the left pulmonary artery

Embryologically, proximal AORPA, distal AORPA, and AOLPA are distinct entities.[5] Proximal AORPA develops due to abnormal aorticopulmonary septation or/and incomplete migration of RPA to the left.[2,5] Hence, it is commonly associated with aortopulmonary septal defects. A combination of these two anomalies further promotes the development of interrupted aortic arch or coarctation due to hemodynamic effects.[5] An association of all three above lesions with PDA present as a syndrome rarely [patient 2; Table 2]. The most likely explanation for distal AORPA is the persistence of the right fifth aortic arch and the disappearance of proximal pulmonary artery (PA) and distal right sixth aortic arch.[5] This may explain the distal narrowing containing ductal tissue, sometimes seen in this anomaly. AOLPA is essentially an aortic arch anomaly, and it is commonly associated with tetralogy of Fallot (TOF) and right aortic arch [Table 2]. Failure of development of the left sixth aortic arch with or without the persistence of the left fifth arch is the main cause of this lesion.[5] In the absence of the left sixth aortic arch, LPA fails to connect to the MPA, and the aortic sac connection persists.[6] Such anomalies of aortic arch development and conotruncal septation are often seen in conditions causing derangement of neural crest cell migration such as CATCH 22/DiGeorge syndrome. AOPA rarely associates with the latter and screening for chromosome 22q11.2 deletion may be warranted if corroborative evidence is present.[6]

Table 2.

Associated defects and additional procedures

Patient serial number	Associated defects	Additional procedures for associated defects
1	Nil	Nil
2	Type A interrupted aortic arch, aortopulmonary window, and large PDA	Aortopulmonary window closure, PDA excision and interruption repair under TCA
3	Nil	Nil
4	Nil	Nil
5	Nil	Nil
6	TOF with hypoplastic main and right PA	Repair of TOF with main and right PA augmentation
7	DORV, VSD, PS	Intraventricular tunneling of LV to aorta + infundibular resection + pulmonary valvotomy
8	DORV, VSD, PS Supra-mitral ring	Intraventricular tunneling of LV to aorta + pulmonary valvotomy + supra-mitral ring excision
9	Nil	Nil
10	Nil	Nil

PA: Pulmonary artery, PDA: Patent ductus arteriosus, TCA: Total circulatory arrest, TOF: Tetralogy of Fallot, DORV: Double-outlet right ventricle, VSD: Ventricular septal defect, PS: Pulmonary stenosis, LV: Left ventricle

In AOPA, the ipsilateral lung has pressure overload, and the contralateral lung has volume overload.[6] Those with reduced blood flow to the contralateral lung (associated with TOF physiology) might be at an advantage as at least one lung is protected. In patients presenting beyond 6 months of age, one may encounter a subset in whom pulmonary vascular disease has already set in. Currently, there are no guidelines to assess operability in this subset. In the past, conventional cardiac catheterization was used to check pulmonary vascular resistance (PVR), but its role is doubtful as the application of Fick’s principle can be erroneous in the scenario of admixture to the affected lung.[7] The use of phase contrast sequences on cardiac magnetic resonance imaging (MRI) provides accurate estimates of pulmonary blood flow to each lung.[7] In doubtful cases, this can be done to assess the flows with immediate pressure measurement in the cardiac catheterization lab to derive PVR in each lung bed.[8] It may be assumed that the surgical re-implantation would then reduce the overall PVR, based on Ohm’s law (Total PVR = 1/[1/PVR_Right + 1/PVR_Left]).[8] Due to the complexity of shifting these sick patients between the cardiac catheterization and MRI suite to obtain near-simultaneous measurements, such an exercise is not routinely carried out.

A comprehensive evaluation using clinical features of a high output state and detailed echocardiographic assessment would help in deciding the operability in most cases. Echocardiographic features which favour operability include an increased pulmonary venous return to the left atrium, flow reversal in the descending aorta, sub-systemic mean and diastolic PA pressures, and the presence of a predominant left to right shunt across a patent foramen ovale. A cardiac CT scan may be done if additional anatomical information is required about any associated cardiac anomaly or to define a distal AORPA. We had two patients in our series who presented toward the end of infancy. Among these, one had pulmonary stenosis and the other had favorable echocardiographic findings and both were operated successfully. It should be noted that despite these precautions, long-term follow-up is mandatory and there has been an incidence of reduced perfusion to the affected lung several years after the surgery.[2]

Appropriate surgical techniques should be chosen based on the site of origin of AOPA.[3] When it arises close to the MPA, like in postero-lateral or posterior aortic origin, direct reimplantation is the procedure of choice.[3] Although the most commonly employed technique worldwide, direct reimplantation is still associated with a high incidence of reinterventions (12.5%–36%), and the majority of these are for anastomotic stenosis.[3,9] We practice the following steps to ensure an adequate, wide, tension-free anastomosis. The anomalous PA is mobilized extensively up to the hilar branches, and it is harvested from aorta with a generous cuff. The ascending aorta is adequately mobilized from the root to the innominate artery, MPA and the normal branch PA are mobilized up to the hilar branches, and PDA is ligated and divided. If there is any tension during reconstruction, pericardial augmentation of the anastomosis is done anteriorly. The ascending aorta is transected in difficult cases to improve visualization. While re-anastomosing the aorta, if the reconstructed RPA is getting compressed, the Lecompte maneuver is performed. The aortic defect, after harvesting AOPA, is closed with a pericardial or prosthetic patch if tension is present, as direct closure in this scenario may rarely cause compression on the reconstructed RPA or may rarely result in supra-aortic stenosis.[9]

Although direct reimplantation is almost always feasible in AOLPA, alternate techniques may be required in some cases of AORPA (anterolateral or distal origin) due to length discrepancy. Most of these techniques are based on raising flaps of native tissues such as the single aortic flap technique or the double flap technique.[9,10] When the length discrepancy is very significant, an interposition graft may be employed, but the patient may require reintervention soon, as he/she outgrows the conduit fast.

The patients require timely and detailed echocardiographic follow-up after surgery to detect the development of any anastomotic complication. Most of the complications can be tackled by catheter interventions such as balloon dilatation or stenting and redo surgery is rarely required.

CONCLUSIONS

AOPA is a rare and potentially correctable anomaly. Early diagnosis and surgery, confirming operability in late presenters before the intervention, ensuring all necessary measures to prevent anastomotic stenosis, and timely follow-up after surgery are essential to achieve the best surgical outcomes.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form, the guardians have given their consent for images and other clinical information to be reported in the journal. The guardians understand that names and initials will not be published and due efforts will be made to conceal the identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.