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Thoracic Aortic Aneurysm

Alternative names:- Aortic aneurysm - thoracic; Syphilitic aneurysm; Aneurysm - thoracic aortic

Thoracic aortic aneurysm is characterized by an abnormal widening of the ascending, transverse, or descending part of the aorta. Aneurysm of the ascending aorta is most common and most often fatal.

The aneurysm may be dissecting, a hemorrhagic separation in the aortic wall, usually within the medial layer; saccular, an outpouching of the arterial wall, with a narrow neck; or fusiform, a spindle-shaped enlargement encompassing the entire aortic circumference.

Some aneurysms progress to serious and, eventually, lethal complications, such as rupture of an untreated thoracic dissecting aneurysm into the pericardium, with resulting tamponade.

Causes

Commonly, a thoracic aortic aneurysm results from atherosclerosis, which weakens the aortic wall and gradually distends the lumen. An intimal tear in the ascending aorta initiates a dissecting aneurysm in about 60% of patients.

An ascending aortic aneurysm, the most common type, is usually seen in hypertensive men under age 60. A descending aortic aneurysm, usually found just below the origin of the subclavian artery, is most common in elderly hypertensive men. It's also seen in younger patients with a history of traumatic chest injury; less often in those with infection. A transverse aortic aneurysm is the least common.

Other causes include:

• fungal infection (mycotic aneurysms) of the aortic arch and descending segments
• congenital disorders, such as coarctation of the aorta
• trauma, usually of the descending thoracic aorta, from an accident that shears the aorta transversely (acceleration-deceleration injuries)
• syphilis, usually of the ascending aorta (uncommon because of antibiotics) . hypertension (in dissecting aneurysm).

Signs and symptoms

Most patients have no symptoms until the aneurysm begins to leak or expand. Most non-leaking thoracic aortic aneurysms are detected by tests -- usually a chest X-ray or a chest CT scan -- run for other reasons. Chest or back pain may indicate acute expansion or leakage of the aneurysm. In an ascending aneurysm, the pain is described as severe, boring, and ripping and extends to the neck, shoulders, lower back, and abdomen but rarely radiates to the jaw and arms. Pain is more severe on the right side. In a descending aneurysm, pain usually starts suddenly between the shoulder blades and may radiate to the chest; it's described as sharp and tearing.

Treatment

A dissecting aortic aneurysm is an emergency that requires prompt surgery and stabilizing measures: antihypertensives such as nitroprusside; negative inotropic agents that decrease contractility force, such as propranolol; oxygen for respiratory distress; narcotics for pain; and L V. fluids and, possibly, whole-blood transfusions.

Surgery consists of resecting the aneurysm, restoring normal blood flow through a Dacron or Teflon graft replacement and, with aortic valve insufficiency, replacing the aortic valve.

Prevention

Prevention measures for atherosclerosis, in general, include not smoking, controlling blood pressure and blood lipid levels, and exercising routinely.