Rare case report of a type-B interrupted aortic arch with aberrant right subcl avian artery

INTRODUCTION

Interrupted aortic arch (IAA) is extremely rare, representing 3 per million live births.^[1] IAA is defined as a complete luminal and anatomical interruption between ascending and descending aorta.^[2] In simple IAA, only ventricular septal defect (VSD) and persistent ductus arteriosus (PDA) are associated. The simple form is more common than the complex form, in which cardiovascular anomalies other than VSD and PDA, such as truncus arteriosus, transposition of the great arteries, double outlet right ventricle, aortopulmonary window, and functional single ventricle, are combined with IAA.^[3-5]

To the best of our knowledge, only a limited number of cases describing the co-existence of IAA and an ARSA have been documented.

CASE REPORT

An 8-month-old male child, born through lower segment cesarean section after an uneventful pregnancy at an external hospital, was diagnosed with congenital heart disease and required 3-day admission in neonatal intensive care unit for initial stabilization and monitoring.

The infant was presented to our facility with a history of cyanosis, hurried breathing, and failure to thrive since early infancy. The parents reported poor weight gain and feeding difficulties, with frequent episodes of respiratory distress. Chest radiograph was performed which revealed cardiomegaly with apparent superior mediastinal widening and peri-hilar congestive changes [Figure 1a]. Echocardiographic evaluation revealed an IAA [Figure 1b] accompanied by a mid-muscular VSD, a fenestrated secundum atrial septal defect (ASD) and a PDA. The type of interruption could not be made out with confidence.

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Figure 1:

(a) Frontal radiograph showing prominent vascular markings (red arrow) and apparent mediastinal widening (yellow dashed arrow). (b) Echocardiography showing main pulmonary artery (yellow arrow), interrupted aorta (orange arrow), patent ductus arteriosus (green arrow), and superior vena cava (blue arrow).

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Computed tomography (CT) angiography showed left aortic arch with luminal disruption distal to the origin of the left common carotid artery. Ductal arch was continued as descending aorta. Left subclavian artery originated from ductal arch and aberrant right subclavian artery was noted arising from proximal descending thoracic aorta distal to the origin of the left subclavian artery with a retro-esophageal course [Figure 2]. Absence of Kommerell diverticulum was noted. The inter-segmental distance between interrupted arch was 1.6 cm. Other findings included intra-mediastinal bifurcation of RPA and LPA [Figure 3a], muscular VSD, secundum ASD and dilated right heart chambers [Figure 3b].

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Figure 2:

(a) Axial computed tomography image showing interrupted arch with patent ductus arteriosus (PDA) giving rise to aberrant right subclavian artery (ARSA) and left subclavian artery. (b) Axial section at the level of clavicles showing different vessels of the neck and their relation to each other. Note the retroesophageal course of the ARSA. (c) Snapshot volume rendered (VR) image showing PDA continuing as descending aorta and with ascending aorta giving the bilateral common carotid artery. Asc Ao: Ascending, aorta; MPA: Main pulmonary artery, PDA: Patent ductus arteriosus, ARSA: Aberrant right subclavian artery, LSCA: Left subclavian artery, RCCA: Right common carotid artery, LCCA: Left common carotid artery, Eso: Esophagus, RPA: Right pulmonary artery, LPA: Left pulmonary artery, RVA: Right vertebral artery, LVA: Left vertebral artery, DA: Descending aorta.

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Figure 3:

Additional findings (a) coronal computed tomography image showing intra-mediastinal branching of both pulmonary arteries, (b) axial image showing atrial and ventral septal defects, and (c) volume rendered (VR) image showing different vessels and their relations to each other. Asc Ao: Ascending aorta; MPA: Main pulmonary artery, PDA: Patent ductus arteriosus, ARSA: Aberrant right subclavian artery, LSCA: Left subclavian artery, RCCA: Right common carotid artery, LCCA: Left common carotid artery, Eso: Esophagus, RPA: Right pulmonary artery, LPA: Left pulmonary artery, RVA: Right vertebral artery, LVA: Left vertebral artery, VSD: ventricular septal defect, ASD: Atrial septal defect. Red stars (3c): Intra-mediastinal branching of pulmonary arteries, DA: Descending aorta.

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DISCUSSION

A rare type of congenital heart disease is an IAA, which affects approximately 1.5% of congenital heart disease patients.^[6] Based on location of the interruption, IAA is classified into three groups. Type-A interruption is positioned distal to the left subclavian artery; Type B interruption is positioned distal to the origin of the left common carotid artery; and Type C interruption is positioned proximal to the origin of the left common carotid artery.^[7] In neonates, 53% of the cases are type B, followed by types A (43%) and C (4%).^[8]

These three types of IAA can be sub-classified according to the origin of the subclavian artery: Type 1: Normal origin of the subclavian artery. Type 2: Aberrant right subclavian artery found distal to the left subclavian artery. Type 3: Isolated right subclavian artery; found originating from a right patent ductus arteriosus.

The aberrant subclavian artery is more prevalent in Type B interruption (30%) than in Type A interruption of aorta, a fact that may be explained by the same developmental origin (cardiac neural crest) of the distal arch and the proximal portion of the subclavian artery contralateral to the aortic arch.^[9] Clinically, these patients with aberrant subclavian artery do not have an upper extremity to lower extremity blood pressure gradient as both the subclavian arteries arise distal to the interrupted segment.^[10]

There is a close relationship between 22q11 deletion and Type B IAA^[11] In over half of cases, Type B IAA is found in the context of specific syndromes such as Di-George syndrome and has a high association rate (98%) with various congenital heart diseases.^[8]

IAA is a duct dependent circulation, where the PDA reforms the descending thoracic aorta distal to interrupted segment. This is completely excised to prevent the residual ductal tissue provoking stenosis of adjacent vessels. Bilateral PDAs are rare and may be observed in IAA in association with double aortic arch or isolated subclavian artery.

Patients with IAA usually become critically ill during the neonatal period and almost all patients undergo cardiac surgery during the 1^st year of life to prevent a fatal outcome.^[12] The distance between interrupted segments differs according to type of IAA (called the inter-segmental distance), being greater in type B than type A.^[13] When the distance is small, direct anastomosis is possible provided that additional arch hypoplasia is not present. When it is longer (as in our case), additional surgeries such as mobilization of proximal descending aorta and interposition graft may be necessary to prevent post-operative complications.

About 95% of the patients with IAA have VSD.^[14] Perimembranous VSD is the most common type accounting for 70% of the cases.^[6,14] VSD in IAA is due to posterior deviation of the outlet septum that may cause obstruction of the left ventricular outflow tract. This is more prevalent in IAA (93%) than coarctation (47%).^[6]

Magnetic resonance angiography (MRA) avoids radiation which, therefore, is more suitable, especially for the pediatric patients. It also suits long term serial follow-up. However, longer acquisition times, potential need for anesthesia in infants, small children, and claustrophobia are some of the drawbacks of MRA. CT angiography is therefore ideal with good spatial resolution.

This case highlights the importance of CT imaging in IAA for surgical planning, to analyze associated cardiac and extra-cardiac anomalies.

This patient was advised to undergo immediate surgery to restore normal physiological circulation; however, the parents declined further management and hence the child was managed conservatively.

DIFFERENTIAL DIAGNOSIS

1. Severe aortic coarctation

2. Patent ductus arteriosus with ductal-dependent circulation

3. Hypoplastic aortic arch atresia

4. Right arch with mirror image branching.

CONCLUSION

The rare coexistence of Type B Interrupted Aortic Arch (IAA) and Aberrant Right Subclavian Artery (ARSA) demands heightened clinical awareness and suspicion. This case emphasizes the critical need for an early diagnosis and detailed multimodality imaging , such as CT angiography, for precise surgical planning. Prompt surgical intervention is necessary to restore normal physiological circulation and ensure patient survival.

TEACHING POINTS

1. Type B interrupted aortic arch is a duct-dependent congenital heart defect that requires surgical correction in infancy to prevent fatal outcomes due to the reliance on PDA for systemic circulation.

2. The presence of ARSA with retroesophageal course should prompt thorough evaluation for feeding difficulties or respiratory compromise due to its anatomical location.

3. Interrupted aortic arch is frequently associated with chromosome 22q11 deletion (DiGeorge syndrome) and other congenital heart diseases, highlighting the need for genetic assessment and multisystem evaluation

MCQs

1. Which of the following congenital anomalies is most frequently associated with Type B interrupted aortic arch?

   1. Coarctation of the aorta

   2. Total anomalous pulmonary venous return

   3. Ventricular septal defect (VSD)

   4. Bicuspid aortic valve

   Answer Key: c

2. In Type B interrupted aortic arch, the interruption typically occurs between which two arteries?

   1. Brachiocephalic and left common carotid artery

   2. Left common carotid and left subclavian artery

   3. Left subclavian and descending thoracic aorta

   4. Ascending aorta and pulmonary artery

   Answer Key: b

3. What is the primary role of patent ductus arteriosus (PDA) in neonates with interrupted aortic arch?

   1. Provides pulmonary venous drainage

   2. Prevents cyanosis by shunting blood

   3. Reduces pulmonary hypertension

   4. Maintains aortic continuity for systemic circulation

   Answer Key: d