Occasionally, in an aorta diseased by arteriosclerosis, a tear de-velops in the intima or the media degenerates, resulting in a dis-section (see Fig. 31-11).
Arterial dissections (separations) are commonly associated with poorly controlled hypertension; they are three times more com-mon in men than in women and occur most commonly in the 50- to 70-year-old age group (Rutherford, 1999). Dissection is caused by rupture in the intimal layer. A rupture may occur through adventitia or into the lumen through the intima, allow-ing blood to reenter the main channel and resulting in chronic dissection or occlusion of branches of the aorta.
As the separation progresses, the arteries branching from the in-volved area of the aorta shear and occlude. The tear occurs most commonly in the region of the aortic arch, with the highest mor-tality rate associated with ascending aortic dissection. The dissec-tion of the aorta may progress backward in the direction of the heart, obstructing the openings to the coronary arteries or produc-ing hemopericardium (effusion of blood into the pericardial sac) or aortic insufficiency, or it may extend in the opposite direction, causing occlusion of the arteries supplying the gastrointestinal tract, kidneys, spinal cord, and legs.
Onset of symptoms is usually sudden. Severe and persistent pain, described as tearing or ripping, may be reported. The pain is in the anterior chest or back and extends to shoulders, epigastric area, or abdomen. Aortic dissection may be mistaken for an acute myo-cardial infarction, which could confuse the clinical picture and ini-tial treatment. Cardiovascular, neurologic, and gastrointestinal symptoms are responsible for other clinical manifestations, de-pending on the location and extent of the dissection. The patient may appear pale. Sweating and tachycardia may be detected. Blood pressure may be elevated or markedly different from one arm to the other if dissection involves the orifice of the subcla-vian artery on one side. Because of the variable clinical picture associated with this condition, early diagnosis is usually difficult.
Arteriography, CT, transesophageal echocardiography, duplex ultrasonography, and magnetic resonance imaging aid in the diagnosis.
Medical or surgical treatment of a dissecting aneurysm depends on the type of dissection present and follows the general princi-ples outlined for the treatment of thoracic aortic aneurysms.
A patient with a dissecting aorta requires the same nursing care as a patient with an aortic aneurysm requiring surgical intervention, as described earlier. Interventions described in the Plan of Nursing Care are also appropriate.
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