(See also Overview of Aortic Aneurysms Overview of Aortic Aneurysms Aneurysms are abnormal dilations of arteries caused by weakening of the arterial wall. Common causes include hypertension, atherosclerosis, infection, trauma, and hereditary or acquired connective... read more .)
Thoracic aortic aneurysms (TAAs) are abnormal dilatations of the aorta above the diaphragm. TAAs account for one fourth of aortic aneurysms. Men and women are affected equally.
Locations of TAAs include
Ascending thoracic aorta (between the aortic root and brachiocephalic, or innominate, artery): 40%
Aortic arch (including the brachiocephalic, carotid, and subclavian arteries): 10%
Descending thoracic aorta (distal to the left subclavian artery): 35%
Upper abdomen—thoracoabdominal aneurysms (TAAAs): 15%
Complications of TAAs include
Compression or erosion into adjacent structures
Leak or rupture
Aneurysms of the ascending aorta sometimes affect the aortic root, causing aortic valve regurgitation Aortic Regurgitation Aortic regurgitation (AR) is incompetency of the aortic valve causing backflow from the aorta into the left ventricle during diastole. Causes include valvular degeneration and aortic root dilation... read more or occlusion of the coronary arterial ostia, causing angina Angina Pectoris Angina pectoris is a clinical syndrome of precordial discomfort or pressure due to transient myocardial ischemia without infarction. It is typically precipitated by exertion or psychologic stress... read more , myocardial infarction Acute Myocardial Infarction (MI) Acute myocardial infarction is myocardial necrosis resulting from acute obstruction of a coronary artery. Symptoms include chest discomfort with or without dyspnea, nausea, and/or diaphoresis... read more , or syncope.
Etiology of Thoracic Aortic Aneurysms
Most thoracic aortic aneurysms result from
Risk factors for both thoracic aortic aneurysms and aortic dissections include prolonged hypertension Hypertension Hypertension is sustained elevation of resting systolic blood pressure (≥ 130 mm Hg), diastolic blood pressure (≥ 80 mm Hg), or both. Hypertension with no known cause (primary; formerly, essential... read more , dyslipidemia Dyslipidemia Dyslipidemia is elevation of plasma cholesterol, triglycerides (TGs), or both, or a low high-density lipoprotein cholesterol level that contributes to the development of atherosclerosis... read more , and smoking. Additional risk factors for TAAs include presence of aneurysms elsewhere in the body, infection, aortitis Aortitis Aortitis is inflammation of the aorta, sometimes causing aneurysm or occlusion. Aortitis is rare, but potentially life threatening. Its reported incidence is 1 to 3 per one million/year. Aortitis... read more , and older age (peak incidence at age 65 to 70).
Congenital connective tissue disorders (eg, Marfan syndrome Marfan Syndrome Marfan syndrome consists of connective tissue anomalies resulting in ocular, skeletal, and cardiovascular abnormalities (eg, dilation of ascending aorta, which can lead to aortic dissection)... read more , Ehlers-Danlos syndrome Ehlers-Danlos Syndrome Ehlers-Danlos syndrome is a hereditary collagen disorder characterized by articular hypermobility, dermal hyperelasticity, and widespread tissue fragility. Diagnosis is clinical. Treatment is... read more , Loeys-Dietz syndrome) cause cystic medial necrosis, a degenerative change that leads to TAAs complicated by aortic dissection Aortic Dissection Aortic dissection is the surging of blood through a tear in the aortic intima with separation of the intima and media and creation of a false lumen (channel). The intimal tear may be a primary... read more and by widening of the proximal aorta and aortic valve (annuloaortic ectasia), which causes aortic regurgitation Aortic Regurgitation Aortic regurgitation (AR) is incompetency of the aortic valve causing backflow from the aorta into the left ventricle during diastole. Causes include valvular degeneration and aortic root dilation... read more . Marfan syndrome causes 50% of cases of annuloaortic ectasia, but cystic medial necrosis and its complications can occur in young people even if no congenital connective tissue disorder is present.
Infected (mycotic) TAAs result from hematogenous spread of systemic or local infections (eg, sepsis Sepsis and Septic Shock Sepsis is a clinical syndrome of life-threatening organ dysfunction caused by a dysregulated response to infection. In septic shock, there is critical reduction in tissue perfusion; acute failure... read more , pneumonia Overview of Pneumonia Pneumonia is acute inflammation of the lungs caused by infection. Initial diagnosis is usually based on chest x-ray and clinical findings. Causes, symptoms, treatment, preventive measures, and... read more ), lymphangitic spread (eg, tuberculosis Tuberculosis (TB) Tuberculosis is a chronic, progressive mycobacterial infection, often with an asymptomatic latent period following initial infection. Tuberculosis most commonly affects the lungs. Symptoms include... read more ), or direct extension (eg, in osteomyelitis Osteomyelitis Osteomyelitis is inflammation and destruction of bone caused by bacteria, mycobacteria, or fungi. Common symptoms are localized bone pain and tenderness with constitutional symptoms (in acute... read more or pericarditis Pericarditis Pericarditis is inflammation of the pericardium, often with fluid accumulation in the pericardial space. Pericarditis may be caused by many disorders (eg, infection, myocardial infarction, trauma... read more ). Bacterial endocarditis Infective Endocarditis Infective endocarditis is infection of the endocardium, usually with bacteria (commonly, streptococci or staphylococci) or fungi. It may cause fever, heart murmurs, petechiae, anemia, embolic... read more and tertiary syphilis Late or tertiary syphilis Syphilis is caused by the spirochete Treponema pallidum and is characterized by 3 sequential clinical, symptomatic stages separated by periods of asymptomatic latent infection. Common... read more are uncommon causes. TAAs occur in some vasculitic disorders (eg, giant cell arteritis Giant Cell Arteritis Giant cell arteritis involves predominantly the thoracic aorta, large arteries emerging from the aorta in the neck, and extracranial branches of the carotid arteries. Symptoms of polymyalgia... read more , Takayasu arteritis Takayasu Arteritis Takayasu arteritis is an inflammatory disease affecting the aorta, its branches, and pulmonary arteries. It occurs predominantly in young women. Etiology is unknown. Vascular inflammation may... read more , granulomatosis with polyangiitis Granulomatosis with Polyangiitis (GPA) Granulomatosis with polyangiitis is characterized by necrotizing granulomatous inflammation, small- and medium-sized vessel vasculitis, and focal necrotizing glomerulonephritis, often with crescent... read more ).
Blunt chest trauma can cause a pseudoaneurysm (false aneurysm) due to injury to the aortic wall resulting in a communication between the arterial lumen and overlying connective tissue and blood leaking outside the confines of the aorta; a blood-filled cavity forms outside the vessel wall and seals the leak as it thromboses).
Symptoms and Signs of Thoracic Aortic Aneurysms
Most thoracic abdominal aneurysms are asymptomatic until complications (eg, thromboembolism, rupture, aortic regurgitation, dissection) develop. However, compression of adjacent structures can cause back pain (due to compression of vertebra), cough (due to compression of the trachea), wheezing, dysphagia (due to esophageal compression), hoarseness (due to left recurrent laryngeal or vagus nerve compression), chest pain (due to coronary artery compression), and superior vena cava syndrome Regional spread .
Erosion of aneurysms into the lungs causes hemoptysis or pneumonitis; erosion into the esophagus (aortoesophageal fistula) causes massive hematemesis.
Dissection manifests with tearing chest pain, often radiating to the back between the shoulder blades.
Thromboembolism may cause stroke, abdominal pain (due to mesenteric ischemia), or extremity pain.
Ruptured TAA that is not immediately fatal manifests with severe chest or back pain and hypotension or shock. Exsanguination due to rupture most commonly occurs into the pleural or pericardial space.
Additional signs include Horner syndrome Horner Syndrome Horner syndrome is ptosis, miosis, and anhidrosis due to dysfunction of cervical sympathetic output. (See also Overview of the Autonomic Nervous System.) Horner syndrome results when the cervical... read more (miosis, ptosis, anhidrosis) due to compression of sympathetic ganglia, palpable downward pull of the trachea with each cardiac contraction (tracheal tug), and tracheal deviation. Visible or palpable chest wall pulsations, occasionally more prominent than the left ventricular apical impulse, are unusual but may occur.
Syphilitic aneurysms of the aortic root classically lead to aortic regurgitation Aortic Regurgitation Aortic regurgitation (AR) is incompetency of the aortic valve causing backflow from the aorta into the left ventricle during diastole. Causes include valvular degeneration and aortic root dilation... read more and inflammatory stenosis of the coronary artery ostia, which may manifest as chest pain due to myocardial ischemia. Syphilitic aneurysms do not dissect.
Diagnosis of Thoracic Aortic Aneurysms
Incidental x-ray finding
Confirmation by CT angiography (CTA), magnetic resonance angiography (MRA), or transesophageal echocardiography (TEE)
Thoracic aortic aneurysms are usually first suspected when a chest x-ray incidentally shows a widened mediastinum or enlargement of the aortic knob. However, chest x-ray has poor sensitivity for TAA and is not a reliable diagnostic tool (eg, in patients with chest pain and suspected aortic aneurysm). Chest x-ray abnormalities, or symptoms and signs suggesting an aneurysm, should be followed up with a cross-sectional imaging test; choice among these tests is based on availability and local experience.
If rupture is suspected, TEE (for ascending dissection) or CTA, depending on availability, should be done immediately. Chest CTA can delineate aneurysm size and proximal or distal extent, detect leakage, and identify coincidental pathology. MRA may provide similar detail. Transthoracic echocardiography (TTE) can delineate size and extent and detect leakage of aneurysms of the ascending but not descending aorta. TEE cannot show the entire thoracic aorta, but it can be extremely useful in detecting the entry point in aortic dissection.
Contrast angiography historically has been the standard imaging test. It does provide the best image of the arterial lumen, but it provides no information on extraluminal structures (ie, as an alternative diagnosis). Additionally, angiography is invasive and has a significant risk of renal and extremity atheroembolism and contrast nephropathy Contrast Nephropathy Contrast nephropathy is worsening of renal function after IV administration of radiocontrast and is usually temporary. Diagnosis is based on a progressive rise in serum creatinine 24 to 48 hours... read more .
Aortic root dilation or unexplained ascending aorta aneurysms warrant serologic testing for syphilis. If a mycotic aneurysm is suspected, bacterial and fungal blood cultures are done.
Prognosis for Thoracic Aortic Aneurysms
Thoracic abdominal aneurysms enlarge an average of 3 to 5 mm/year. Risk factors for rapid enlargement include larger size of aneurysm, location in the descending aorta, and presence of mural thrombi.
Annual rupture risk is
2% for aneurysms < 5 cm
3% for aneurysms of 5 to 5.9 cm
8 to 10% for aneurysms > 6 cm
The risk appears to rise abruptly as TAAs reach 6 cm in diameter. Median diameter at aneurysm rupture is 6 cm for ascending aneurysms and 7 cm for descending aneurysms; smaller aneurysms also may rupture, especially in patients with connective tissue disorders or saccular aneurysms.
Survival rate of patients with untreated large TAAs is 65% at 1 year and 20% at 5 years. TAAA rupture has a mortality of 97%.
Treatment of Thoracic Aortic Aneurysms
Endovascular stent grafting or open surgical repair
Control of hypertension and other comorbidities
Immediate control of hypertension is essential.
Medical management with optimal control of hypertension, dyslipidemia, diabetes, and respiratory disease is the appropriate treatment until surgery is indicated. Treatment is endovascular stent grafting when anatomically possible and open surgical repair for more complex aneurysms.
Ruptured TAAs, if untreated, are universally fatal. They require immediate intervention, as do leaking aneurysms and those that cause acute dissection or acute valvular regurgitation.
Transcatheter-placed endovascular stent grafts (endografts) for descending TAAs and TAAAs are a less invasive alternative to open surgery.
Surgery involves a median sternotomy (for ascending and aortic arch aneurysms) or left thoracotomy or thoraco-retroperitoneal exposure (for descending and thoracoabdominal aneurysms) and replacement with a synthetic graft. With emergency open surgery, the mortality rate at 1 month is about 40 to 50%. Patients who survive have a high incidence of serious complications (eg, renal failure, respiratory failure, severe neurologic damage).
Elective surgery is indicated for aneurysms that are
Rapidly enlarging (> 0.5 cm/year)
Causing bronchial compression
Causing aortobronchial or aortoesophageal fistulas
Aneurysms of the ascending aorta are generally considered large if the diameter is > 5.5 cm or twice the native size of the ascending aorta or if the aortic size index (aortic diameter in relation to body surface area) is ≥ 2.75 cm/m2. In the descending aorta, aneurysms are generally considered large if they are > 6 cm. In patients with Marfan syndrome, large aneurysms are those that are ≥ 4.5 to 5 cm in any location.
Treatment of mycotic aneurysms is aggressive antibiotic therapy directed at the specific pathogen. Generally, these aneurysms must also be surgically repaired.
Although open surgical repair of an intact TAA improves outcome, mortality rate may still exceed 5 to 10% at 30 days and is 40 to 50% at 10 years. The mortality rate is lower with endovascular stent grafts. Risk of death increases greatly if aneurysms are complicated (eg, located in the aortic arch or thoracoabdominal aorta) or if patients are older or have coronary artery disease, symptoms, or preexisting renal insufficiency. Perioperative complications (eg, stroke, spinal injury, renal failure) occur in about 10 to 20%.
Asymptomatic aneurysms that do not meet criteria for elective surgical or endovascular repair are treated with aggressive blood pressure control Treatment Hypertension is sustained elevation of resting systolic blood pressure (≥ 130 mm Hg), diastolic blood pressure (≥ 80 mm Hg), or both. Hypertension with no known cause (primary; formerly, essential... read more using a beta-blocker and other antihypertensives if necessary. Smoking cessation Smoking Cessation Most smokers want to quit and have tried doing so with limited success. Effective interventions include cessation counseling and drug treatment, such as varenicline, bupropion, or a nicotine... read more is essential. Dyslipidemia, diabetes, and respiratory diseases should all be treated. Patients require frequent follow-ups to check for symptoms and serial CT or ultrasonography every 6 to 12 months. Imaging frequency depends on aneurysm size.
Thoracic aortic aneurysm (TAA) is a ≥ 50% increase in diameter of the thoracic aorta.
TAAs may dissect, compress, or erode into adjacent structures, cause thromboembolism, leak, or rupture.
Median diameter at aneurysm rupture is 6 cm for ascending aneurysms and 7 cm for descending aneurysms.
Diagnosis is often first suspected based on an incidental x-ray or CT finding, and confirmed using CT angiography, magnetic resonance angiography, or transthoracic echocardiography.
Treat small, asymptomatic TAAs with aggressive management of blood pressure and dyslipidemia and smoking cessation.
Treat larger or symptomatic TAAs with endovascular stent grafting when anatomically possible and open surgical repair for more complex aneurysms.