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KEY FACTS

Terminology
- Rare congenital vascular anomaly
- May be isolated or associated with other abnormalities - Complex congenital cardiac heart disease - Vascular anomalies - Skeletal anomalies
- 2 distinct forms - Systemic-to-systemic connection: 5th arch arises at brachiocephalic trunk and reconnects at descending aorta - Systemic-to-pulmonary connection: 5th arch connects with embryologic remnant of 6th aortic arch, which is usually left pulmonary artery
Imaging
- Contrast-enhanced MRA most appropriate in children with suspected persistent 5th arch
- Short segment of duplication aortic arch with 2 parallel distinct lumina in systemic-to-systemic connection
- Abnormal vessel connecting aorta with isolated pulmonary artery in systemic-to-pulmonary connection
Clinical Issues
- Presentation depends on which type of connections exists and on associated cardiac and vascular anomalies
- Associated cardiovascular anomalies - Ventricular septal defect (most common) - Pulmonic valve or artery stenosis/atresia - Interruption of aortic arch - Coarctation of aorta - Transposition of great arteries - Pentalogy of Fallot - Patent ductus arteriosus - Tricuspid atresia
- In case of coarctation/obstruction, surgical patching or conduit interposition may be indicated

TERMINOLOGY

Synonyms
- Ipsilateral double aortic arch
- Double lumen aortic arch
Definitions
- Rare congenital vascular anomaly of aortic arch - May be isolated - Often associated with other congenital cardiac, vascular, or skeletal anomalies
- 2 distinct forms - Systemic-to-systemic connection - 5th arch arises at brachiocephalic trunk and reconnects at descending aorta - Systemic-to-pulmonary connection - 5th arch connects with embryologic remnant of 6th aortic arch, which is usually left pulmonary artery

IMAGING

General Features

Best diagnostic clue

- Short segment of duplication of aortic arch with 2 parallel distinct lumina
        - May have interrupted arch
- Abnormal vessel connecting aorta with pulmonary artery

Location

- Aortic arch
        - Cephalad of arches is 4th arch, which gives rise to arch vessels
        - Lower arch is persistent 5th arch

Radiographic Findings

Radiography

- May demonstrate associated findings, such as vertebral anomalies

CT Findings

CTA

- 2 distinct left aortic arches with what may appear as septation separating them
- Double-barrel appearance on coronal oblique short-axis views
- May have interrupted arch
- May show anomalous connection between aorta and isolated left pulmonary artery
- May demonstrate associated cardiovascular and skeletal abnormalities

MR Findings
- Same as CTA findings
- Superior to echocardiography due to acoustic window restrictions near aortic arch

Imaging Recommendations

Best imaging tool
```
- CTA or MRA
```

Protocol advice

- Contrast-enhanced MRA most appropriate in children with suspected persistent 5th arch

DIFFERENTIAL DIAGNOSIS

Aortic Dissection
- Easily differentiated by double-barrel appearance of persistent 5th arch: 2 round lumina form "figure of 8" on arch short-axis views
Patent Ductus Arteriosus
- Systemic-to-pulmonary connection may mimic large PDA
- PDA would communicate distally to arch arteries
Aortopulmonary Window
- Abnormal connection between proximal aorta and pulmonary trunk

CLINICAL ISSUES

Presentation

Most common signs/symptoms

- Often presents soon after birth due to associated cardiac or vascular defects
        - Ventricular septal defect
        - Pulmonic valve or artery stenosis/atresia
        - Interruption of aortic arch
        - Complex congenital heart disease
- Often present after birth due to associated cardiac or vascular defects
        - Ventricular septal defect (most common), pulmonic valve or artery stenosis/atresia, tricuspid atresia
        - Interruption of aortic arch, coarctation of aorta, transposition of great arteries, persistent truncus arteriosus, PDA
- Could be hemodynamically beneficial
        - Systemic-to-systemic connection; if associated with coarctation of aorta or interrupted aortic arch
        - Systemic-to-pulmonic connection; when associated with pulmonary or tricuspid atresia

Clinical profile

- Association with intrauterine thalidomide exposure and chromosomal disorders
- Weinberg classification defines 3 types (A,B,C)
        - Type A: Double-lumen aortic arch (arch vessels arise from upper 4th; lower is 5th arch)
        - Type B: Single-lumen arch; 4th arch is interrupted; 5th arch originates from ascending and connects to descending aorta
        - Type C: 5th originates from proximal brachiocephalic artery off of ascending aorta and connecting to pulmonary artery via 6th arch
- Associated cardiovascular anomalies include
        - Coarctation
        - Pulmonary atresia or stenosis
        - Transposition of great arteries
        - Truncus arteriosus
        - Pentalogy of Fallot
        - PDA, ventricular septal defect
        - Tricuspid atresia

Demographics

Epidemiology

- Extremely rare congenital malformation

Treatment
- In case of coarctation/obstruction, surgical patching or conduit interposition may be indicated

DIAGNOSTIC CHECKLIST

Consider
- May have obstruction due to associated coarctation - Check BP difference between upper and lower extremities (BP in both arms)

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References

Selected References

Cases

{'cases': [{'authors': [{'key': 'b00d2bdb-66e1-41ed-90b4-c52904f4d598', 'value': 'Seth Kligerman, MD, MS'}], 'caseVersionId': '33e370c1-f5d0-4136-8a26-f4f065378eab', 'description': "Coronal CT angiograms through the chest (Figs. 1-3) and sagittal oblique volume-rendered image (Fig. 4) with a posterior view of the aorta show the transverse aorta bifurcating into the superior and inferior channels just proximal to the level of the left brachiocephalic artery (, Fig. 4) and again merging just distal to the left subclavian artery (, Figs. 3-4). The more inferior arch is the persistent 5th arch. All of the arch vessels, including the left common carotid artery (, Figs. 1, 4,), arise from the true arch. Volume-rendered 3-D cine clip (Vid. 1) again shows the bifurcation.", 'history': 'Patient with multiple congenital bony anomalies and a history of intrauterine thalidomide exposure undergoes preoperative CT.', 'imagePoolId': '8123c1a9-ea90-4684-985e-d9c873cc0c2d', 'name': 'Persistent Fifth Arch', 'teachingPoint': 'Persistence of the 5th aortic arch is an exceedingly rare anomaly. There are 2 mains forms. In the systemic to systemic form, the arch connects the ascending and descending aorta. In the systemic to pulmonary form, the 5th arch connects to a pulmonary artery, usually the left.', 'demographics': '45 Years old male'}], 'caseType': 'typical', 'name': 'TYPICAL'}

Images

Selected Images

Aortic arch "candy cane" view of CTA shows separation of the aortic arch into 2 distinct vessels (). The superior is the normal 4th aortic arch giving rise to the arch vessels. The inferior is the persistent 5th aortic arch.*

Coronal CTA in the same patient shows the short axis of aortic arches with a double-barrel appearance (). The 4th and persistent 5th arch have a figure of 8 configuration in the short axis, which allows differentiation from dissection.*

Oblique 3D volume-rendered reconstruction shows the relationship of the 4th arch with the arch vessels. Note the abnormal persistent 5th arch arising from the aorta at the level of the brachiocephalic trunk and reentering into the descending thoracic aorta at its isthmus.

Oblique 3D reconstruction of the skull in the same patient shows a cleft palate . Other skeletal anomalies in this patient include fused ribs and hemi vertebra (not shown).

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