Thoracic Aortic Aneurysms

Thoracic Aortic Aneurysms

• Location of thoracic aortic aneurysm determines clinical manifestations and natural history
• Medial degeneration is the most common pathology associated with ascending aortic aneurysms
• Atherosclerosis is the condition most frequently associated with aneurysms of the descending thoracic aorta
• Average growth rate of thoracic aneurysms is 0.1–0.2 cm per year
• Thoracic aortic aneurysms associated with Marfan’s syndrome or aortic dissection may expand at a greater rate
• Risk of rupture is related to size of aneurysm and presence of symptoms, ranging from 2–3% per year for aneurysms 6 cm in diameter
• Most thoracic aortic aneurysms are asymptomatic
• Compression or erosion of adjacent tissue by aneurysms may cause symptoms such as chest pain, shortness of breath, cough, hoarseness, and dysphagia

Diagnosis and Management

• Chest x-ray may be the first test that suggests the diagnosis of thoracic aortic aneurysm
• Findings on chest x-ray include widening of mediastinal shadow and displacement or compression of trachea or left main stem bronchus
• Echocardiography, particularly transesophageal echocardiography, can be used to assess proximal ascending aorta and descending thoracic aorta
• Contrast-enhanced CT, magnetic resonance imaging (MRI), and conventional invasive aortography are sensitive and specific tests for assessment of aneurysms of thoracic aorta and involvement of branch vessels
• Noninvasive testing with either contrast-enhanced CT or MRI should be performed at least every 6–12 months to monitor expansion in asymptomatic patients
• β-Adrenergic blockers are recommended for patients with thoracic aortic aneurysms, particularly those with Marfan’s syndrome
• Additional medical therapy should be given as necessary to control hypertension
• Angiotensin receptor antagonists may reduce rate of aortic dilation in patients with Marfan’s syndrome by blocking TGF-β signaling

Surgical Indications

• Operative repair is indicated in patients with symptomatic ascending thoracic aortic aneurysms
• Operative repair is also indicated for most asymptomatic aneurysms, including those associated with bicuspid aortic valves when aortic root or ascending aortic diameter is ≥5.5 cm, or when growth rate is >0.5 cm per year
• Replacement of ascending aorta >4.5 cm is reasonable in patients with bicuspid aortic valves undergoing aortic valve replacement due to severe aortic stenosis or aortic regurgitation
• In patients with Marfan’s syndrome, ascending thoracic aortic aneurysms of 4–5 cm should be considered for surgery

Abdominal Aortic Aneurysms

• Abdominal aortic aneurysms occur more frequently in males than in females and incidence increases with age
• Cigarette smoking is a potent modifiable risk factor
• Abdominal aortic aneurysms ≥4.0 cm may affect 1–2% men aged >50 years
• At least 90% of all abdominal aortic aneurysms >4.0 cm are related to atherosclerotic disease
• Prognosis is related to both size of aneurysm and the symptoms