TOC | Cardiology   

Aneurysm of Aorta                                        See also Abdominal Aortic Aneurysms

• 4. Descending Thoracic Aortic Aneurysm
• 5. Ascending Aortic Aneurysms                                                                                                                 
• 6. Transverse Aortic Arch Aneurysms
• 7. Aortic Transection

Morphologically, aneurysms are classified into three types:

1. fusiform (spindle shaped), which involve the entire circumference of the aorta;
2. sacciform, which are characterized by a pouchlike protrusion from a narrow opening in the aortic wall; and
3. dissecting aortic, which are characterized by intramural separation, usually within the medial layer.

Descending Thoracic Aortic Aneurysm

Aneurysms of the descending thoracic aorta develop distal to the left subclavian artery and extend distally for varying lengths to the diaphragm. Most aneurysms in this area are due to atherosclerosis or medial degenerative disease. Other causes may be trauma, infection, and aortitis. The most common morphologic type is fusiform, although sacciform and dissecting aneurysms may also occur at this site. These aneurysms are seen most often in men in the sixth to eighth decades of life. About 25% of patients with an aneurysm of the descending thoracic aorta also have aneurysms of the infrarenal abdominal aorta.

Etiology of Thoracic aortic aneurysms

• Atherosclerosis
• Infection (mycotic)
• Trauma
• Syphilis
• Marfan's syndrome
• Aortic stenosis
• Coarctation of the aorta
• Patent ductus arteriosus
• Relapsing polychondritis

Symptoms of Thoracic aneurysms

• Anterior or posterior chest pain
• Dysphagia (esophageal compression)
• Hoarseness (vocal chord paralysis secondary to compression of the recurrent laryngeal nerve)
• Superior vena caval syndrome (compression of the superior vena cava)
• Cough, dyspnea, or both (pulmonary arterial or tracheal compression)
• Hemoptysis (erosion of aneurysm into pulmonary parenchyma or rupture of aneurysm into a bronchus)
• Shock (rupture of aneurysm into pleural space)
• Angina (ostial lesions of syphilitic aortitis)

Approximately one third of the patients with an aneurysm of the descending thoracic aorta are asymptomatic, the disease being diagnosed by plain radiography of the chest. Pain, which is due to compression or erosion of surrounding structures, is the most common symptom. Patients may complain of cough, hemoptysis, dysphagia, or hematemesis.

Physical findings in patients with Thoracic aneurysms

• Tracheal tug (pulsation)
• Tracheal deviation
• Vocal cord paralysis
• Superior vena caval syndrome
• Pulsation of right sternoclavicular joint
• Visible and palpable pulsation of anterior chest wall (usually second or third intercostal space on the right or higher up on the left)
• Inequality of upper extremity pulses or blood pressure (or both)

DX:
Plain chest x-ray, CT or MRI is exceedingly useful in identifying the characteristics of the aneurysm of the descending thoracic aorta, but contrast aortography remains an essential diagnostic tool in providing information regarding the precise site and extent of the disease.

RX:
Surgical repair of these aneurysms should be considered if the patient is symptomatic or if the transverse diameter of the aneurysm is more than two times that of the medial descending thoracic aorta. Treatment consists of excision of the diseased segment of the aorta and replacement with the proper size of woven or albumin-coated Dacron graft.

The use of atrial femoral bypass, which provides distal profusion, minimizes the risk of ischemia to the spinal cord and renal failure. Paraplegia or paralysis occurs in about 3 to 5% of the patients. The long-term results of surgical resection are excellent.

Ascending Aortic Aneurysms

Acquired aneurysms of the ascending aorta may be due to medial degeneration, atherosclerosis, or aortic dissection. Although syphilis used to be a major cause of aortic aneurysms, this cause is seldom seen today.

SX:
These aneurysms may be asymptomatic, or symptoms may develop as a result of compression of the tracheobronchial tree, the esophagus, or the superior vena cava. Patients with associated aortic valvular insufficiency may have heart failure. Any aneurysm larger than 5 cm in diameter should be considered for surgical resection.

DX:
A plain radiograph of the chest often suggests aneurysm of the ascending aorta, and CT or MRI is extremely useful in identifying the extent of the aneurysm. Contrast aortography-ascending coronary arteriography is usually performed.

RX:
Treatment is surgical, consisting of resection of the aneurysm and replacement with a woven or albumin-coated Dacron graft. If the patient also has aortic insufficiency or a sinus of Valsalva aneurysm, a composite valve graft, requiring reattachment of the coronary arteries, is used. Cardiopulmonary bypass, cardioplegia, and hypothermia are used. The long-term results of this operation have been gratifying.

Transverse Aortic Arch Aneurysms

Aneurysms of the transverse aortic arch are usually fusiform, but occasionally a sacciform aneurysm may occur along the lesser curvature of the aorta. The cause of these aneurysms is related to medial degeneration, atherosclerosis, or aortic dissection.

DX:
An abnormal mediastinal mass on routine radiography may initiate a diagnostic work-up. Ultimately, CT, MRI, or contrast aortography is required to completely evaluate the aorta and the brachiocephalic arteries.

RX:
Surgical treatment consists of resection of the involved aorta and reattachment with an island of aorta to the brachiocephalic arteries. Cardiopulmonary bypass, profound hypothermia, retrograde cerebral perfusion, and circulatory arrest are mandatory in the surgical treatment of these difficult surgical cases. If the descending thoracic aorta is concomitantly involved, the "elephant trunk" technique is used to facilitate the subsequent staged repair of the descending thoracic aorta. Close cooperation between the anesthesiologist and perfusionist is imperative in maintaining the body temperature, blood volume, and coagulation factors. This operation can be done with astonishingly good results and long-term survival.

Traumatic injuries of the aorta are increasing in frequency and recognition. Most patients with this injury die immediately. Only a small number tamponade sufficiently to reach medical facilities. Transection usually occurs just distal to the left subclavian artery after deceleration injuries from high-speed motor vehicle accidents or falls from heights.

DX:
The diagnosis may be suspected if the radiograph shows widening of the mediastinum or deviation of the esophagus, trachea, or superior vena cava. Contrast aortography confirms the diagnosis. CT, MRI, or transesophagram ultrasonography may also provide information.

RX:
Immediate surgical repair is mandatory. The operation consists of primary repair of a localized tear or limited segmental resection of the injured aorta and replacement with a woven or albumin-coated Dacron graft. In the care of the patient with acute aortic transection, the method for minimizing spinal cord ischemia is controversial. The use of an atrial-femoral bypass is recommended. In patients with acute aortic transection who survive, a chronic false aneurysm may develop many years later manifested as a posterior mediastinal mass.

Treatment of these chronic post-traumatic thoracic aneurysms is the same as that for descending thoracic aortic aneurysms.

Ref:
Rakel: Conn's Current Therapy 1998, 50th ed., Copyright © 1998 W. B. Saunders Company
Joseph Alpert: Manual of Cardiovascular Diagnosis & Therapy
Braunwald : : Heart Disease 1997,  5th Ed

02172000