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Aortic dissection occurs when a tear in the tunica intima of the aorta causes blood to flow between the layers of the wall of the aorta, forcing the layers apart. In most cases this is associated with severe characteristic chest or abdominal pain described as "tearing" in character, and often with other symptoms that result from decreased blood supply to other organs. Aortic dissection is a medical emergency and can quickly lead to death, even with optimal treatment, as a result of decreased blood supply to other organs, heart failure, and sometimes rupture of the aorta. Aortic dissection is more common in those with a history of high blood pressure, a known thoracic aortic aneurysm, and in a number of connective tissue diseases that affect blood vessel wall integrity such as Marfan syndrome and the vascular subtype of Ehlers–Danlos syndrome. The diagnosis is made with medical imaging (computed tomography, magnetic resonance imaging or echocardiography). The treatment of aortic dissection depends on the part of the aorta involved. Surgery is usually required for dissections that involve the aortic arch, while dissections of the part further away from the heart may be treated with blood pressure lowering only. Since the 1990s endovascular aneurysm repair (carried out from inside the blood vessels) has been used in specific cases. Aortic dissection is relatively rare, occurring at an estimated rate of 2–3.5 per 100,000 people every year. It is more common in males for unknown reasons. Mean age at diagnosis is 63, although all age groups may be affected. Many cases of aortic dissection (40%) lead to death so rapidly that the person does not reach a hospital in time. The first case of aortic dissection described was in the post-mortem examination of King George II of Great Britain in 1760. Surgery for aortic dissection was introduced in the 1950s. ==Signs and symptoms== About 96% of individuals with aortic dissection present with severe pain that had a sudden onset. It may be described as tearing, stabbing, or sharp in character. 17% of individuals will feel the pain migrate as the dissection extends down the aorta. The location of pain is associated with the location of the dissection. Anterior chest pain is associated with dissections involving the ascending aorta, while interscapular (back) pain is associated with descending aortic dissections. If the pain is pleuritic in nature, it may suggest acute pericarditis caused by bleeding into the pericardial sac. This is a particularly dangerous eventuality, suggesting that acute pericardial tamponade may be imminent. Pericardial tamponade is the most common cause of death from aortic dissection. While the pain may be confused with the pain of a myocardial infarction (heart attack), aortic dissection is usually not associated with the other signs that suggest myocardial infarction, including heart failure and ECG changes. Individuals with aortic dissection who do not present with pain have chronic dissection. Less common symptoms that may be seen in the setting of aortic dissection include congestive heart failure (7%), fainting (9%), stroke (6%), ischemic peripheral neuropathy, paraplegia, and cardiac arrest. If the individual had a fainting episode, about half the time it is due to bleeding into the pericardium leading to pericardial tamponade. Neurologic complications of aortic dissection (i.e., stroke and paralysis) are due to involvement of one or more arteries supplying portions of the central nervous system. If the aortic dissection involves the abdominal aorta, compromise of the branches of the abdominal aorta is possible. In abdominal aortic dissections, compromise of one or both renal arteries occurs in 5–8% of cases, while mesenteric ischemia (ischemia of the large intestines) occurs 3–5% of the time. 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「Aortic dissection」の詳細全文を読む スポンサード リンク
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