Aneurysm, thoracic aortic
Aneurysm, thoracic aortic: Excerpt from Handbook of Diseases
Thoracic aortic aneurysm is characterized by an abnormal widening of the ascending, transverse, or descending part of the aorta. Aneurysm of the ascending part of the aorta is the most common type — and is usually 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.
Aneurysm of the ascending part of the aorta is usually seen in hypertensive men who are younger than age 60. Aneurysm of the descending part of the aorta, 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, although less often in those with infection. Aneurysm of the transverse part of the aorta 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 part of the aorta around the thorax, from an accident that shears the aorta transversely (acceleration-deceleration injuries)
syphilis, usually of the ascending part of the aorta (uncommon because of antibiotics)
hypertension (in dissecting aneurysm).
Signs and symptoms
Pain most commonly accompanies a thoracic aortic aneurysm. (See Clinical characteristics of thoracic dissection.) With an aneurysm of the ascending part of the aorta, 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.
Other signs include bradycardia, aortic insufficiency, pericardial friction rub caused by a hemopericardium, unequal intensities of the right and left carotid pulses and radial pulses, and a difference in blood pressure between the right and left arms. If dissection involves the carotid arteries, an abrupt onset of neurologic deficits may occur.
With an aneurysm of the descending part of the aorta, pain usually starts suddenly between the shoulder blades and may radiate to the chest; it’s described as sharp and tearing.
With an aneurysm of the transverse part of the aorta, sudden, sharp, tearing pain radiates to the shoulders. It may also cause hoarseness, dyspnea, dysphagia, and dry cough because of compression of surrounding structures.
Diagnosis
Patient history, signs and symptoms, and appropriate tests provide diagnostic information. In an asymptomatic patient, diagnosis may occur accidentally when chest X-rays show widening of the mediastinum. The following other tests help confirm an aneurysm:
Aortography, the definitive test, shows the lumen of the aneurysm, its size and location, and the false lumen in a dissecting aneurysm.
Electrocardiography (ECG) helps distinguish a thoracic aneurysm from a myocardial infarction.
Echocardiography may help identify a dissecting aneurysm of the aortic root.
Hemoglobin level may be normal or low because of blood loss from a leaking aneurysm.
Computed tomography scan can confirm and locate the aneurysm and may be used to monitor its progression.
Magnetic resonance imaging may aid diagnosis.
Transesophageal echocardiography is used to measure the aneurysm in both the ascending and the descending aorta.
Treatment
A dissecting aneurysm is an emergency that requires prompt surgery and stabilizing measures: an antihypertensive such as nitroprusside; a negative inotropic agent that decreases contractility force, such as propranolol; oxygen for respiratory distress; a narcotic for pain; I.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.
Postoperative measures include careful monitoring and continuous assessment in the intensive care unit, an antibiotic, endotracheal (ET) intubation, chest tube insertion, ECG monitoring, and pulmonary artery (PA) catheterization.
Special considerations
Monitor the patient’s blood pressure, pulmonary artery wedge pressure (PAWP), and central venous pressure (CVP). Also, evaluate the patient’s pain, breathing, and carotid, radial, and femoral pulses.
Review laboratory test results, which must include a complete blood count with differential, electrolyte levels, typing and crossmatching for whole blood, arterial blood gas analysis, and urinalysis.
Insert an indwelling urinary catheter. Administer dextrose 5% in water or lactated Ringer’s solution and an antibiotic as needed. Carefully monitor nitroprusside I.V. infusion rate; use a separate I.V. line for infusion. Adjust the dose by slowly increasing the infusion rate. Meanwhile, check blood pressure every 5 minutes until it stabilizes.
If bleeding from an aneurysm is suspected, give a whole blood transfusion.
Explain diagnostic tests. If surgery is scheduled, explain the procedure and expected postoperative care (I.V. lines, ET and drainage tubes, cardiac monitoring, ventilation).
After repair of a thoracic aneurysm:
Evaluate the patient’s level of consciousness. Monitor vital signs; PA pressure, PAWP, and CVP; pulse rate; urine output; and pain.
Check respiratory function. Carefully observe and record type and amount of chest tube drainage, and frequently assess heart and breath sounds.
Monitor I.V. therapy.
Give medications as appropriate.
Watch for signs of infection, especially fever, and excessive wound drainage.
Assist the patient with range-of-motion exercises for the legs, to prevent thromboembolism due to venostasis during prolonged bed rest.
After vital signs and respiration have been stabilized, encourage and assist the patient in turning, coughing, and deep breathing. If necessary, provide intermittent positive-pressure breathing to promote lung expansion.
Help the patient walk as soon as he’s able.
Before discharge, ensure adherence to antihypertensive therapy by explaining the need for such drugs as well as their adverse effects. Teach the patient how to monitor his blood pressure.
CLINICAL TIP: Refer the patient to community agencies for continued support and assistance as needed.
Throughout hospitalization, offer the patient and family psychological support. Pictures
Book Source Details
- Book Title: Handbook of Diseases
- Author(s): Springhouse
- Year of Publication: 2003
- Copyright Details: Handbook of Diseases, Copyright © 2003 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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More About This Book:
Title: Handbook of Diseases
Authors: Springhouse
Publisher: Lippincott Williams & Wilkins
Copyright: 2003
ISBN: 1-58255-266-5
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