ESSENTIALS OF DIAGNOSIS
Sudden searing chest pain with radiation to the back, abdomen, or neck in a hypertensive patient.
Widened mediastinum on chest radiograph.
Pulse discrepancy in the extremities.
Acute aortic regurgitation may develop.
Aortic dissection occurs when a spontaneous intimal tear develops and blood dissects into the media of the aorta (eFigure 12–15). The tear probably results from the repetitive torque applied to the ascending and proximal descending aorta during the cardiac cycle; hypertension is an important component of this disease process. Type A dissection involves the arch proximal to the left subclavian artery, and type B dissection occurs in the proximal descending thoracic aorta typically just beyond the left subclavian artery (eFigure 12–16). Dissections may occur in the absence of hypertension but abnormalities of smooth muscle, elastic tissue, or collagen are more common in these patients. Pregnancy, bicuspid aortic valve, and coarctation also are associated with increased risk of dissection.
CT scan of the thorax obtained through the level of the aortic arch. The ascending aorta (A) is dilated, but the lumen is filled with contrast material. Aortic dissection is present, seen when the descending portion of the aortic arch is examined (D). Here, the false lumen occupies 90% of the dilated aorta, and the true lumen carrying contrast material occupies only about 10%. (Used, with permission, from H Goldberg.)
DeBakey and Stanford Classifications of aortic dissection. (Reproduced, with permission, from Doherty G (ed): Current Diagnosis & Treatment: Surgery, 13e. McGraw-Hill, 2010.)
Blood entering the intimal tear may extend the dissection into the abdominal aorta, the lower extremities, the carotid arteries or, less commonly, the subclavian arteries. Both absolute pressure levels and the pulse pressure are important in propagation of dissection. Aortic dissection is a true emergency and requires immediate control of blood pressure to limit the extent of the dissection. With type A dissection, which has the worse prognosis, death may occur within hours due to rupture of the dissection into the pericardial sac or dissection into the coronary arteries, resulting in myocardial infarction. Rupture into the pleural cavity is also possible. The intimal/medial flap of the aortic wall created by the dissection may occlude major aortic branches, resulting in ischemia of the brain, intestines, kidney, or extremities.
Severe persistent chest pain of sudden onset radiating down the back or possibly into the anterior chest is characteristic. Radiation of the pain into the neck may also occur. The patient is usually hypertensive. Syncope, hemiplegia, or paralysis of the lower extremities may occur. Mesenteric ischemia or kidney injury may develop. Peripheral pulses may be diminished or unequal. ...