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Coarctation of the aorta, or aortic narrowing (abbreviated as CoA〔(【引用サイトリンク】title=Coarctation of the Aorta (CoA) )〕), is a congenital condition whereby the aorta narrows in the area where the ductus arteriosus (ligamentum arteriosum after regression) inserts. Aortic coarctation is considered when a section of the aorta is narrowed to an abnormal width. The word “coarctation” means narrowing. Coarctations are most common where the aorta—the major artery leading away from the heart—arches toward the abdomen and legs. The aortic arch may be small in babies with coarctations. Other heart defects may also occur when coarctation is present, typically occurring on the left side of the heart. When a patient has a coarctation, the left ventricle has to work harder. Since the aorta is narrowed, the left ventricle must generate a much higher pressure than normal in order to force enough blood through the aorta to deliver blood to the lower part of the body. If the narrowing is severe enough, the left ventricle may not be strong enough to push blood through the coarctation, thus resulting in lack of blood to the lower half of the body. Physiologically its complete form is manifested as interrupted aortic arch. ==Classification== There are three types of aortic coarctations: # Preductal coarctation: The narrowing is proximal to the ductus arteriosus. Blood flow to the aorta that is distal to the narrowing is dependent on the ductus arteriosus; therefore severe coarctation can be life-threatening. Preductal coarctation results when an intracardiac anomaly during fetal life decreases blood flow through the left side of the heart, leading to hypoplastic development of the aorta. This is the type seen in approximately 5% of infants with Turner Syndrome. # Ductal coarctation: The narrowing occurs at the insertion of the ductus arteriosus. This kind usually appears when the ductus arteriosus closes. # Postductal coarctation: The narrowing is distal to the insertion of the ductus arteriosus. Even with an open ductus arteriosus, blood flow to the lower body can be impaired. This type is most common in adults. It is associated with notching of the ribs (because of collateral circulation), hypertension in the upper extremities, and weak pulses in the lower extremities. Postductal coarctation is most likely the result of the extension of a muscular artery (ductus arteriosus) into an elastic artery (aorta) during fetal life, where the contraction and fibrosis of the ductus arteriosus upon birth subsequently narrows the aortic lumen. 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「Coarctation of the aorta」の詳細全文を読む スポンサード リンク
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