British Journal of Radiology (2006) 79, e71-e74
© 2006 British Institute of Radiology
doi: 10.1259/bjr/28729845
Double aortic arch with atresia, tapering and aneurysm of the left arch
H Ito, MD, PhD1,
A Konishi, MD, PhD2,
T Kon-Nai, MD, PhD2,
T Ishibashi, MD, PhD3 and
S Takahashi, MD, PhD3
Departments of 1Diagnostic Radiology and 2Cardiovascular Surgery, Miyagi Cardiovascular and Respiratory Center, Semine, Miyagi and 3Department of Diagnostic Radiology, Graduate School of Medicine, Tohoku University, Sendai, Japan
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Abstract
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An adult male underwent chest radiography for a health check-up. This disclosed both thoracic vascular anomalies and a small nodular shadow in the left side of the superior mediastinum. Axial MRI and three-dimensional volume-rendering MR angiography revealed both a double aortic arch with left atretic arch proximal to the left common carotid artery (subtype 4), and also tapering and aneurysm of the left arch distal to the left subclavian artery. To the authors' knowledge, this report describes the first case of subtype 4 of atretic double arch with left arch atresia. Such thoracic vascular anomalies have been a theoretical possibility, but no cases have been reported to date.
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Introduction
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Double aortic arch is formed from the splitting of the ascending aorta into two limbs that pass to either side of the trachea and oesophagus, and join as a single descending aorta. Anatomic variations of the double aortic arch relate to the relative size of the two arches, partial atresia of one arch and the side of the ductus and descending aorta. Partial obstruction of an arch in an anomalous double aortic arch usually occurs in the left arch; the atretic arch persists as a fibrotic cord [1, 2]. MRI can reveal the vascular anatomic details of congenital anomalies of the aortic arch including a double aortic arch [1, 3].
We report an adult male who has both a double aortic arch with atretic left arch (subtype 4), and also tapering and aneurysm of the left arch, and discuss the differential diagnoses of thoracic vascular anomalies of the present case.
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Case report
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A 39-year-old man underwent chest radiography during a regular health check-up. It revealed a thoracic vascular anomaly and nodular shadow in the left side of the superior mediastinum (Figure 1
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Figure 1. Chest radiograph indicates an abnormal thoracic aortic arch with right-sided tracheal impression (large arrow). In addition, it demonstrates a small nodular shadow (small arrow) the left of the superior mediastinum.
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He had been healthy since birth with no history of cardiac disease or hypertension. He had no significant history of shortness of breath or dysphagia. Echocardiography revealed no intracardiac defects. Laboratory data such as leukocyte count, serum c-reactive protein and immunoreactive protein, such as rheumatic factor, were all within normal limits.
He underwent MRI examination on a 1.5-Tesla system (Gyroscan Intera 1.5 T Power; Philips Medical Systems, The Netherlands). T1 weighted spin-echo (SE) axial, coronal images were obtained (repetition time (TR)/echo time (TE) 1091/16, slice thickness 5 mm) (Figure 2). Gadolinium-enhanced MR angiography of the thoracic vessels was also performed with spoiled gradient echo sequence. The following sequence parameters were used: TR/TE 4.8/1.5, flip angle 30°, slice thickness 1.4 mm, pitch 0.5, matrix 205 x 256. Three-dimensional (3D) volume-rendering MR angiography was reconstructed using 3D software (Zio M900 Quadra; Amin, Tokyo, Japan) (Figure 3).
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Figure 2. (a) Axial T1 weighted spin-echo image shows a "four artery sign", which comprises the anterior common carotid (large black arrows) and posterior subclavian (small black arrows) arteries in the symmetrical position. Moreover, the small left arch (small white arrow) transforms into an aneurysm (large white arrow) via the narrow lumen. (T, trachea; E, oesophagus). (b) Axial T1 weighted spin-echo image 2.5 cm inferior to (a) demonstrates proximal right aortic arch (RA) with a retro-oesophageal segment, anterior common carotid arteries (large black arrows), posterior right superior vena cava (large white arrow) and posteroinferior distal aortic arch (small black arrow). The proximal and middle aortic arch compresses the right lateral and posterior wall of the trachea (T) with resultant narrowing of the lumen. Displaced azygos vein (large white arrow), which separates the azygos lobe from right upper lobe, drains into the superior vena cava. Double white arrows show the position of the oesophagus.
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Figure 3. (a) Anteroposterior image of 3D volume-rendering MR angiography shows the right-sided aortic arch (RA), which divides the first two branches of the right common carotid (RC) and the right subclavian artery (RS). Then, the left subclavian (LS) and left common carotid arteries (LC) are derived from the third branch of the left innominate artery (arrow), which is eventually considered the small left arch (PA, pulmonary artery). (b) Deep left anterior oblique image of 3D volume-rendering MR angiography shows that the left subclavian (LS) and left common carotid artery (LC) are derived from the left arch (black arrow) locating proximal to the aneurysm (white arrow) (RC, right common carotid artery; RS, right subclavian artery; PA, pulmonary artery). (c) Deep right posterior oblique image of 3D volume-rendering MR angiography shows tapering and aneurysm (arrow) of the left arch (RA, right arch; PA, pulmonary artery; RC, right common carotid artery; RS, right subclavian artery; LC, left common carotid artery; LS, left subclavian artery).
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The MR images demonstrated a double aortic arch. The first branch arising from the right aortic arch was the right common carotid artery, followed by the right subclavian artery and the left innominate artery.
The left innominate artery derived from the distal portion of the aortic arch; it coursed upward and showed a gradual tapering of the lumen, then transforming into an aneurysm. Thereafter, the innominate artery distal to the aneurysm descended anteriorly and inwardly, taking a course parallel to the right arch and dividing into an upward angled left subclavian artery. It then continued descending further in the same direction, before subsequently bending abruptly upward into the left common carotid artery.
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Discussion
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Axial MRI and 3D volume-rendering MR angiography demonstrate that the right common carotid artery is the first branch and that the right subclavian artery is the second. They originate from the right-sided arch. Because the right-sided arch is associated with a left-side descending thoracic aorta, the aortic arch passes behind the oesophagus. Therefore, the third branch of the left innominate artery originating from the distal part of the aortic arch would not be expected to further indent the oesophagus. Indeed, it courses upward without crossing the midline.
Moreover, the third branch distal to the aneurysm is parallel to the right-sided arch: it divides into an upward left subclavian artery, and then into an upward left common carotid artery. Although the segment distal to the left common carotid artery is not visible, the left common carotid artery and the right-sided aortic arch are in close approximation. We infer that this results from an atretic segment of the left arch.
From our patient, we have concluded that the thoracic vascular anomalies of the present case are manifested by atresia of the left arch during embryonic development. Therefore, the third branch, which is described as the left innominate artery, is identical to the left arch.
The most likely diagnosis of the present case is a double aortic arch with atretic left arch proximal to the left common carotid artery [1, 4].
A double aortic arch is the most common cause of a symptomatic vascular ring in infants and young children [1]. However, patients with a vascular ring in association with a double aortic arch rarely have accompanying symptoms even in adulthood, as in our patient [5, 6]. Barium oesophagography may suggest a vascular ring, but does not allow definition of the exact configuration of the anomaly.
Four subtypes of double aortic arch with left arch atresia exist, according to the site of atresia of the left arch [1]. The hypothetical double aortic arch (Figure 4a) was proposed by Edwards [7]. The zones of the left arch are lettered from back to front as A–D, as first described by Garti et al [9].
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Figure 4. (a) The hypothetical double aortic arch system proposed by Edwards, showing zones of the left arch labelled A–D (RC, right common carotid artery; RS, right subclavian artery; LC, left common carotid artery; LS, left subclavian artery; AA, ascending aorta; PA, pulmonary artery; rda, right ductus arteriosus; lda, left ductus arteriosus). (b) Atresia of left arch (LAA) along the zone D in hypothetical double aortic arch demonstrates subtype 4 of the double aortic arch with left atretic arch. Moreover, tapering (Tap) and aneurysm (An) are probably located, respectively, in the A and B zones, but the correct origin of the left ductus arteriosus (lda) from the left arch is uncertain (RC, right common carotid artery; RS, right subclavian artery; LC, left common carotid artery; LS, left subclavian artery; AA, ascending aorta; PA, pulmonary artery; rda, right ductus arteriosus; lda, left ductus arteriosus). Illustrations are modified from those by B Singh et al [8].
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A double aortic arch with left arch atresia is classified into subtype 1 if atresia occurs between the ligamentum arteriosum or left ductus and the descending aorta (Zone A). Atresia between the left subclavian artery and the ligamentum arteriosum or left ductus (Zone B), or between the left common carotid artery and the left subclavian artery (Zone C), respectively, forms subtype 2 or 3. Subtype 4 is designated by atresia proximal to the left common carotid artery (Zone D).
In the present case, subtype 3 is first excluded from the differential diagnosis. In subtypes 1 and 2, the left innominate artery arises as the first branch from the ascending aorta. For that reason, these two subtypes are excluded. In subtype 4, the left innominate artery would arise as the third branch from descending aorta: this latter subtype is the most likely diagnosis in our case. No such cases have been documented to date [1]. Atresia of the left arch (Zone D) with tapering and aneurysm (Zones A and B) is illustrated in Figure 4b
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Most aortic arch anomalies with an atretic left arch (Zone D) tend not to be associated with complex congenital heart disease [1, 2, 5]. This rule applies to the present case. This observation is also in agreement with descriptions in other cases of isolated left subclavian and left carotid arteries where there is atresia of zone D in association also with zones A, B and C [10–12].
However, the pattern of branching in our patient is identical to that seen in right aortic arch with an aberrant left innominate artery and ligamentum arteriosum. Therefore, a right aortic arch with a left aberrant innominate artery can not be excluded from the differential diagnosis [1, 4], whereas a left aberrant innominate artery in association with a right aortic arch usually derives from a right-sided aortic arch and courses across the midline behind the oesophagus [4].
An additional nodular radio-opacity in the superior mediastinum is commonly seen in patients with thoracic vascular anomalies [13, 14]. In the present case, the nodular shadow adjacent to the left side of the superior mediatinum is caused by the aneurysm of the left aortic arch, distal to the origin of the left subclavian artery.
Arterial tapering and aneurysm are irreversible changes. They occur in association with various aetiologies such as degenerative disease, trauma, infective or inflammatory aortitis, connective tissue disorders and congenital abnormalities [15]. Laboratory data and the clinical history in our patient were normal. We suggest that the arterial changes we have reported are congenital.
In summary, we report an extremely rare case of not only a double aortic arch with an atretic left arch (subtype 4), but also anomalous tapering and aneurysm of the left arch distal to the origin of the left subclavian artery. To our knowledge, the present report describes the first case with subtype 4 of a double aortic arch with a left atretic arch, although such a thoracic vascular anomaly has previously been suggested as theoretically possible.
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Acknowledgments
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We thank Mr Takahiro Chiba (Radiological Technologist of Kurihara Chuo Hospital, Tsukidate, Miyagi, Japan) for his skilful assistance with the MRI examination.
Received for publication July 20, 2004.
Revision received March 17, 2005.
Accepted for publication September 19, 2005.
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Abstract
Introduction
