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Double aortic arch (DAA) is a relatively rare congenital cardiovascular malformation. DAA is an anomaly of the aortic arch in which two aortic arches form a complete vascular ring that can compress the trachea and/or esophagus.〔Jonas RA. Comprehensive Surgical Management of Congenital Heart Disease, London, Arnold, 2004, p. 497〕〔Kirklin JW, Barratt-Boyes BG. Cardiac Surgery, 3rd ed., New York, Churchill Livingstone, 2003, p. 1415〕 Most commonly there is a larger (dominant) right arch behind and a smaller (hypoplastic) left aortic arch in front of the trachea/esophagus. The two arches join to form the descending aorta which is usually on the left side (but may be right-sided or in the midline). In some cases the end of the smaller left aortic arch closes (left atretic arch) and the vascular tissue becomes a fibrous cord. Although in these cases a complete ring of two patent aortic arches is not present, the term ‘vascular ring’ is the accepted generic term even in these anomalies. The symptoms are related to the compression of the trachea, esophagus or both by the complete vascular ring. Diagnosis can often be suspected or made by chest x-ray, barium esophagram, or echocardiography. Computed tomography (CT) or magnetic resonance imaging (MRI) show the relationship of the aortic arches to the trachea and esophagus and also the degree of tracheal narrowing. Bronchoscopy can be useful in internally assessing the degree of tracheomalacia. Treatment is surgical and is indicated in all symptomatic patients. In the current era the risk of mortality or significant morbidity after surgical division of the lesser arch is low. However, the preoperative degree of tracheomalacia has an important impact on postoperative recovery. In certain patients it may take several months (up to 1–2 years) for the obstructive respiratory symptoms (wheezing) to disappear. == Classification == Double aortic arch is a subtype of complete vascular ring. There are three types of double aortic arch: * ''Right dominant'' arch (about 70% of surgical cases) * ''Balanced'' or codominant (about 5%): both arches are of equal size * ''Left dominant'' (about 25%) ''Double aortic arch with right dominant arch:'' Normally there is only one (left) aortic arch. In patients with double aortic arch the ascending aorta arises normally from the left ventricle but then divides into two arches, a left and a right aortic arch which join posteriorly to become the descending aorta. The smaller left arch passes anteriorly and to the left of the trachea in the usual position. It is often joined by the ligamentum arteriosum (or patent ductus arteriosus) where it forms the descending aorta. The left arch gives first origin to the left common carotid artery and then the left subclavian artery. The right aortic arch is completing the vascular ring by passing to the right and then behind the esophagus and trachea to join the usually left-sided descending aorta. The first vessel coming off the right arch is usually the right common carotid artery followed by the right subclavian artery. ''Double aortic arch with left dominant arch:'' In this less common condition, as the name indicates, the left arch is the larger of the two aortic arches. The origins of the arm and head vessels are identical to the anatomy of double aortic arch with right dominant arch ''Balanced or codominant double aortic arch:'' In this rare condition both aortic arches are of the same diameter. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Double aortic arch」の詳細全文を読む スポンサード リンク
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