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Thoracic aortic aneurysm

 
, medical expert
Last reviewed: 12.07.2025
 
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Thoracic aortic aneurysms account for a quarter of aortic aneurysms. Men and women are affected equally.

Approximately 40% of thoracic aortic aneurysms develop in the ascending thoracic aorta (between the aortic valve and the brachiocephalic trunk), 10% in the aortic arch (including the brachiocephalic trunk, carotid, and subclavian arteries), 35% in the descending thoracic aorta (distal to the left subclavian artery), and 15% in the upper abdomen (as thoracoabdominal aneurysms).

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Causes of thoracic aortic aneurysms

Most thoracic aortic aneurysms are due to atherosclerosis. Risk factors for both conditions include long-standing hypertension, dyslipidemia, and smoking. Additional risk factors for thoracic aortic aneurysms include the presence of aneurysms elsewhere and older age (peak incidence is 65–70 years).

Congenital connective tissue disorders (eg, Marfan syndrome, Ehlers-Danlos syndrome) cause cystic necrosis of the media, a degenerative change that leads to thoracic aortic aneurysm complicated by aortic dissection and dilation of the proximal aorta and aortic valve causing aortic regurgitation. Marfan syndrome accounts for 50% of cases of such dilation, but cystic necrosis of the media and its complications can develop in young people even in the absence of congenital connective tissue disorders.

Infected (mycotic) thoracic aortic aneurysms occur as a result of hematogenous spread of the pathogen in systemic or local infections (e.g., sepsis, pneumonia), lymphatic penetration (e.g., tuberculosis), and direct spread from a nearby focus (e.g., osteomyelitis or pericarditis). Infective endocarditis and tertiary syphilis are rare causes. Thoracic aortic aneurysms develop in some connective tissue diseases (e.g., giant cell arteritis, Takayasu's arteritis, Wegener's granulomatosis).

Blunt chest trauma causes pseudoaneurysms (extramural hematomas that form as a result of rupture of the aortic wall).

Thoracic aortic aneurysms may dissect, collapse, destroy adjacent structures, lead to thromboembolism or rupture.

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Symptoms of thoracic aortic aneurysms

Most thoracic aortic aneurysms remain asymptomatic until complications develop (eg, aortic regurgitation, dissection). Compression of adjacent structures may cause chest or low back pain, cough, wheezing, dysphagia, hoarseness (due to compression of the left recurrent laryngeal or vagus nerve), chest pain (due to coronary artery compression), and superior vena cava syndrome. Erosive rupture of the aneurysm into the lungs causes hemoptysis or pneumonia. Thromboembolism may cause stroke, abdominal pain (due to mesenteric embolism), or extremity pain. Rupture of a thoracic aortic aneurysm, if not immediately fatal, causes severe chest or low back pain, hypotension, or shock. Bleeding usually occurs into the pleural or pericardial space. If there is an aortoesophageal fistula before the rupture, massive vomiting of blood is possible.

Additional signs include Horner's syndrome due to compression of sympathetic ganglia, palpable tracheal tension with each heartbeat (tracheal jerk), and tracheal deviation. Visible or palpable chest wall pulsations, sometimes more prominent than the left ventricular apex beat, are unusual but possible.

Syphilitic aortic root aneurysms classically result in aortic regurgitation and inflammatory stenosis of the coronary artery orifices, which may manifest as chest pain due to myocardial ischemia. Syphilitic aneurysms do not dissect.

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Diagnosis of thoracic aortic aneurysms

A thoracic aortic aneurysm is usually suspected when chest radiography reveals a widened mediastinum or a widened aortic shadow. These findings or clinical manifestations that raise suspicion of an aneurysm are confirmed by three-dimensional imaging studies. CTA can determine the size of the aneurysm, its proximal and distal extent, detect blood leaks, and identify other pathology. MRA provides similar data. Transesophageal echocardiography (TEE) can determine the size and extent and detect blood leaks in the ascending (but not descending) aorta.

TEE is particularly important for the detection of aortic dissection. Contrast angiography provides better visualization of the arterial lumen but does not provide information regarding extraluminal structures, is invasive, and carries a significant risk of renal embolism from atheromatous plaque, embolism to the lower extremities, and contrast-induced nephropathy. The choice of imaging study is based on availability and physician experience, but if rupture is suspected, immediate TEE or CTA is indicated (depending on availability).

Aortic root dilation or unexplained ascending aortic aneurysms are indications for serologic testing for syphilis. If a mycotic aneurysm is suspected, bacterial and fungal blood cultures are obtained.

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Treatment of thoracic aortic aneurysms

Treatment includes surgical replacement and control of hypertension, if present.

Ruptured thoracic aortic aneurysms are always fatal if left untreated. They require immediate surgical intervention, as do leaking aneurysms and those in acute dissection or acute valvular regurgitation. Surgery involves median sternotomy (for ascending and aortic arch aneurysms) or left thoracotomy (for descending and thoracoabdominal aneurysms), followed by excision of the aneurysm and placement of a synthetic graft. Catheter-based endovascular stenting (endograft placement) in the descending aorta is being studied as a less invasive alternative to open surgery. With emergency surgical treatment, the 1-month mortality rate is approximately 40-50%. Surviving patients have a high incidence of serious complications (eg, renal failure, respiratory failure, severe nervous system pathology).

Surgical treatment is preferable for large (diameter > 5-6 cm in the ascending part, > 6-7 cm in the descending part of the aorta, and for patients with Marfan syndrome > 5 cm at any location) and rapidly enlarging (> 1 cm/year) aneurysms. Surgical treatment is also prescribed for aneurysms accompanied by clinical symptoms, post-traumatic or syphilitic aneurysms. For syphilitic aneurysms, benzylpenicillin is prescribed intramuscularly after surgery at 2.4 million units per week for 3 weeks. If the patient is allergic to penicillin, tetracycline or erythromycin is used at 500 mg 4 times a day for 30 days.

Although surgical treatment of intact thoracic aortic aneurysms has good results, mortality may still exceed 5-10% within 30 days and 40-50% over the next 10 years. The risk of death is greatly increased in complicated aneurysms (eg, located in the aortic arch or thoracoabdominal region) and in patients with coronary artery disease, advanced age, symptomatic aneurysms, or renal failure. Perioperative complications (eg, stroke, spinal cord injury, renal failure) occur in approximately 10-20% of cases.

In asymptomatic aneurysms and the absence of indications for surgical treatment, the patient is monitored, blood pressure is carefully controlled, beta-blockers and other antihypertensive drugs are prescribed as needed. CT scans are required every 6-12 months and frequent medical examinations are necessary to detect symptoms. Smoking cessation is mandatory.

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Prognosis for thoracic aortic aneurysm

Thoracic aortic aneurysms enlarge by an average of 5 mm per year. Risk factors for rapid enlargement include large aneurysm size, location in the descending aorta, and the presence of organ thrombi. On average, when an aneurysm ruptures, its diameter is 6 cm for ascending aneurysms and 7 cm for descending aneurysms, but in patients with Marfan syndrome, rupture may occur at smaller sizes. The untreated survival rate for patients with large thoracic aortic aneurysms is 65% at 1 year and 20% at 5 years.

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