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Cardiovascular Imaging In-a-Month

●Chest Roentogenogram Mimicking Double Aortic Arch in a 30-Year-Old Female With Effort Dyspnea and Dysphagia

Shie OHGI, MD

Hisao ITO, MD, FJCC

Katsuhiko ISOGAMI, MD＊1

Takayuki KANNO, MD＊2

──────────────────────────────────────────────宮城県立循環器・呼吸器病センター 放射線科〔黄木詩恵，伊藤久雄〕，＊1呼吸器外科〔磯上勝彦〕，＊2循環器科〔菅野孝幸〕:〒989－4501 宮城県栗原郡瀬峰町大里字富根岸55－2Departments of Diagnostic Radiology, ＊1Respiratory Surgery and ＊2Cardiology, Miyagi Cardiovascular and Respiratory Center, MiyagiAddress of correspondence : ITO H, MD, FJCC, Department of Diagnostic Radiology, Miyagi Cardiovascular and Respiratory Center,Tominegishi 55－2, Osato, Semine-machi, Kurihara-gun, Miyagi 989－4501Manuscript received September 5, 2003 ; revised September 29, 2003 ; accepted October 11, 2003

Fig. 1 Fig. 2

CASEA 30-year-old female was generally healthy, but sometimes experienced low grade

intermittent effort dyspnea with wheezing and mild dysphagia when swallowing alarge piece of solid food. Physical examination revealed no abnormalities, and herblood pressure was 130/82 mmHg. Electrocardiography and echocardiographyrevealed no abnormalities. Chest roentgenography（Fig. 1）and swallow esophagogra-phy（Fig. 2）were performed.

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Chest roentogenography（Fig. 1）suggested mildenlargement of the right lower cardiac margin, andshowed two nodular shadows in the bilateral uppermediastinum, which were considered to be aorticknobs. In addition, the margin of the right aorticknob was apparently connected to the longitudinalstripe line parallel to the right border of the thoracicspine, which suggested the margin of the descend-ing thoracic aorta on the right. However, no intra-cardiac defects were revealed by echocardiography.We thought that chest roentogenography showedthe silhouette of a double aortic arch, and that vas-cular ring in association with double aortic arch hadcaused the esophago-respiratory symptoms,although we could not confirm tracheal or esoph-ageal narrowing on the chest roentogenogram.Furthermore, we found right and left esophagealimpressions on swallow esophagography（Fig. 2）in association with the double aortic arch, whereasthe right esophageal impression was located at theaortic knob（short arrow）and just inferior to theright aortic knob（middle arrow）.

In contrast, cross-sectional and coronal spiralcomputed tomography（CT）with contrast mediumimage disclosed unanticipated radiological featuresof right aortic knob and left mediastinal round nod-ule of 3 cm in diameter（Figs. 3, 4）.

Three-dimensional CT angiography（Fig. 5）demonstrated the nature of the thoracic vascularanomalies prior to angiographic examination, asright aortic arch with mirror image branching, andaortic diverticulum（asterisk）which was located atthe proximal portion of the descending thoracicaorta. Digital subtraction angiography of the pos-teroanterior projection（Fig. 6）confirmed right aor-tic arch with mirror image branching, but we couldsee only a small part of the aortic diverticulum,because of overlapping by the ascending thoracicaorta and left common carotid artery.

Right aortic arch with mirror image branchinghas been classified into two types（Type A andType B）1）caused by the different breaking point of

the left aortic arch of the“hypothetical double aor-tic arch”2）. The break of the aortic arch is intimate-ly associated with the origin of the ductus arterio-sus and intracardiac anatomy. Interruption of theleft arch posterior to the left ductus arteriosus leadsto a right aortic arch with mirror image branchingand ductus arteriosus originating from the leftinnominate or left subclavian artery. This type ofthoracic vascular anomaly（Type A）is commonlyencountered, and is not associated with vascularring, but cardiac anomalies such as tetralogy ofFallot or truncus arteriosus. On the other hand,interruption of the left arch between the left subcla-vian artery and left ductus arteriosus leads to a rightaortic arch with mirror image branching and ductusarteriosus derived from the aortic diverticulum ofthe proximal descending thoracic aorta. This typeof thoracic vascular anomaly（Type B）is rarelyencountered and is not associated with intracardiacdefects, but vascular ring.

The thoracic vascular anomalies of the presentpatient are eventually considered to be Type B rightaortic arch with mirror image branching. This com-bination of Type B right aortic arch with mirrorimage branching and mediastinal nodule isextremely rare.

Diagnosis : Right aortic arch with mirror imagebranching（Type B）causing vascular ring, and leftupper mediastinal nodule

Key Words : Aorta（right aortic arch, vascular ring）;Computed tomography（three-dimensional CT angiogra-phy）; Neoplasms

References

1）Garti IJ, Aygen MM, Vidne B, Levy MJ : Right aortic archwith mirror-image branching causing vascular ring : A newclassification of the right aortic arch patterns. Br J Radiol1973 ; 46 : 115－119

2）Edwards JE : Anomalies of derivatives of aortic arch sys-tem. Med Clin North Am 1948 ; 32 : 925－949

Points for Diagnosis

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Fig. 3

Fig. 4 Fig. 5

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astinal nodule（arrow）, aortic diverticulum（asterisk）and the left brachiocephalic artery（arrowhead）arevisible. The esophagus（small black circle）is sur-rounded by trachea, aortic diverticulum and mediasti-nal nodule. SVC＝ superior vena cava ; AA＝ascending thoracicaorta ; DA＝descending thoracic aorta ; T＝ trachea.

Fig. 4 Coronal computed tomographic scan, multiplanarreconstruction, at the level of the posterior medi-astinumThe round mediastinal nodule（arrowheads）is locatedjust above the left main pulmonary artery. The aorticdiverticulum（asterisk）is seen. P＝ pulmonary artery ; B＝ left main bronchus.Other abbreviation as in Fig. 3.

Fig. 5 Three-dimensional computed tomographyangiogram, left posterocranial projection, demon-strating right aortic arch with mirror imagebranchingThe aortic diverticulum（asterisk）is situated at theproximal portion of the right-sided descending tho-racic aorta. The ligamentum arteriosus, which is acomponent of the vascular ring, is supposed to belocated between the aortic diverticulum and the pul-monary artery. LCCA＝ left common carotid artery ; LSA＝ leftsubclavian artery ; LBCA＝ left brachiocephalicartery ; RCCA＝ right common carotid artery ;RSA＝ right subclavian artery ; PA＝ pulmonaryartery ; LA＝ left atrium. Other abbreviations as inFig. 3.

Fig. 6 Digital subtraction angiogram, posteroanteriorprojection, showing right aortic arch with mirrorimage branchingThe first branch of the thoracic aorta is the left bra-chiocephalic artery, which is divided into two branch-es of the left common carotid artery and left subcla-vian artery. The second and third branches are theright common carotid artery and right subclavianartery, respectively. Opacification of the medistinalnodule is barely visible, whereas the outer margin（arrowheads）is noted. The aortic diverticulum（arrow）overlaps the ascending thoracic aorta and leftbrachiocephalic artery, but a small part of the aorticdiverticulum without overlapping is visible. Abbreviations as in Figs. 3, 5.

Fig. 6

Fig. 1 Chest radiogram demonstrating two nodularshadows in the bilateral upper mediastinumThe right nodular shadow（arrow）is a right aorticknob, whereas the left nodular shadow（arrowhead）isa left upper mediastinal nodule.

Fig. 2 Swallow esophagogram, posteroanterior projec-tion, showing esophageal impressionsThe esophageal impressions located on the right（short and middle arrows）are caused by right aorticknob and aortic diverticulum, and on the left（longarrow）by left mediastinal nodule, respectively.

Fig. 3 Cross-sectional computed tomographic scan at theupper mediastinal levelThe right aortic arch compresses the trachea withresultant narrowing of the lumen. The round medi-