Thoracic aortic aneurysm

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-In-Chief: Maheep Singh Sangha, M.B.B.S. Associate Editor(s)-in-Chief: Mohammed Salih, MD. [2]

A thoracic aortic aneurysm (TAA) is defined as an expansion or dilation of the aorta greater than 4.5 cm. Thoracic aortic aneurysms (TAAs) encompass all aneurysms the aorta between the aortic root and the crura of the diaphragm. The aortic root and the ascending thoracic aorta are the most common sites of TAAs (60%), followed by the descending thoracic aorta (40%). Involvement of the aortic arch and/or extension of a TAA into the abdominal aorta (AA) (so called thoracoabdominal aneurysms) are relatively uncommon subsets (each encountered in 10% of cases or less).

An aneurysm occurs when a part or entire circumference of the vessel is pathologically dilated. A true aneurysm involves all three layers of the vessel, whereas pseudoaneurysm is characterized by disruption of the intima and media, and the dilated segment of the aorta is lined by adventitia alone.

Two of the most common causes of thoracic aorta aneurysm are marfan’s syndrome and atherosclerosis. In some centers, a prior history of dissection with aneurysmal dilation is the most common cause of surgical repair.

Thoracic aortic aneurysms are often asymptomatic and as a result can be easily missed. If chest pain is present, it is critical to differentiate a thoracic aortic aneurysm with dissection from other potential life-threatening diseases.

Thoracic aortic aneurysms are relatively uncommon (6 to 10 new ones per 100,000 person years) and are less prevalent than abdominal aortic aneurysm. Thoracic aortic aneurysms are generally diagnosed after the sixth and seventh decades of life. Although men are affected 2 to 4 times as often as women, women are at higher risk of rupture by a factor 6.8.

Hypertension and cigarette smoking are the most important risk factors, though the importance of genetic factors in the development of thoracic aortic aneurysm (such as familial thoracic aortic aneurysm; familial aortic dissection) has been increasingly recognized. Approximately 10% of patients may have other family members who have aortic aneurysms. It is also important to note that individuals with a history of aneurysms in other parts of the body have a higher chance of developing a thoracic aortic aneurysm.^[1]

Thoracic aneurysms enlarge at a more rapid rate than abdominal aneurysms (0.42 vs. 0.28 cm/yr), with aneurysms of the aortic arch growing at ~ 0.56 cm/yr. Aneurysms that are 5-6 cm in diameter have a faster rate of growth and a greater tendency to rupture than smaller ones. Aortic dissection and aortic rupture are the two most feared complications of an aortic aneurysm. The five-year survival of patients with a thoracic aortic aneurysm is 56%. The following are associated with a poorer prognosis: the presence of diastolic dysfunction; trauma as a cause of the aneurysm; the presence of coronary artery disease and the presence of carotid artery disease.

Screening for TAA is not recommended in the general population. However, certain population substrates, such as those with history of marfan’s syndrome, turner’s syndrome, ehlers-danlos type IV syndrome, familial thoracic aortic disease syndromes, bicuspid aortic valve, takayasu arteritis, giant cell arteritis, loeys-dietz syndrome or a confirmed genetic mutation known to predispose to aortic aneurysms and aortic dissections (TGFBR1, TGFBR2, FBN1, ACTA2, or MYH11) should have imaging study to screen for TAAs. First-degree relatives of people with thoracic aortic aneurysm or dissection should have aortic imaging to identify asymptomatic disease. Patients with high risk syndromes such as marfan’s syndrome and loeys-dietz syndrome should undergo complete aortic imaging at initial diagnosis and 6 months thereafter to establish if enlargement is occurring.

Thoracic aortic aneurysms typically expand slowly at a rate of approximately 0.1-0.2 cm/year. Aortic dissection and aortic rupture are the two most feared complications of an aortic aneurysm. The five-year survival of patients with a thoracic aortic aneurysm is 56%. The following are associated with a poorer prognosis: the presence of diastolic dysfunction; trauma as a cause of the aneurysm; the presence of coronary artery disease and the presence of carotid artery disease.

Most thoracic aortic aneurysms are asymptomatic and diagnosed incidentally on imaging studies. The development of symptoms can indicate that the thoracic aortic aneurysm is expanding. When symptoms are present, they are generally due to compression of adjacent structures. These compressive symptoms include dysphagia (compression of the esophagus), dyspnea and chronic cough (compression of the airway), or hoarseness (compression of the recurrent laryngeal nerve).

A large thoracic aortic aneurysm may be associated with findings on physical examination secondary to aortic insufficiency (wide pulse pressure, diastolic murmur, heart failure) and compression of adjacent structures such as the recurrent laryngeal nerve (hoarseness), superior vena cava obstruction (selling of the face and neck), and the airway (stridor and wheezing).

The diagnosis of a thoracic aortic aneurysm is often made as an incidental finding on either chest x-ray (widening of the mediastinum), on transthoracic echocardiography (dilated aortic root) or on trans esophageal echocardiography (enlarged ascending aorta or aortic arch). The definitive diagnosis is made using CT angiography but MRA is also an excellent test. Once diagnosed, serial CTA (or MRA) are recommended every 6-12 months. The frequency of surveillance imaging should be increased if the aneurysm is larger at baseline, if there is a recent history of accelerating expansion, if the patient is pregnant, and if the patient has marfan syndrome, loeys-dietz syndrome or a confirmed genetic mutation known to predispose to aortic aneurysms and aortic dissections (TGFBR1, TGFBR2, FBN1, ACTA2, or MYH11). Indeed in these high risk syndromes, the patient should undergo complete aortic imaging at the time of the initial diagnosis and then every 6 months to determine if enlargement is occurring. Bicuspid aortic valve, coarctation of the aorta, and/or dilatation of the ascending thoracic aorta should be excluded in a patient with turner’s syndrome. Follow-up imaging should be obtained every 5 to 10 years in the patient with turner’s syndrome if the initial imaging is normal, and yearly if any abnormalities are present. Patients with bicuspid aortic valve disease and first-degree relatives of patients with bicuspid aortic valve disease should undergo imaging to rule out the presence of the thoracic aortic aneurysm.

Thoracic aortic aneurysm is associated with a abnormality on chest x-ray in 80 to 90% of patients. Smaller aneurysms (saccular aneurysms) may not be apparent on a chest x ray.

The definitive diagnosis of thoracic aortic aneurysm can be made using magnetic resonance angiography (MRA). Once the diagnosis is made, serial MRAs (or CT) are recommended every 6-12 months.

Computed tomography is the most effective method for measuring and monitoring the maximum outer diameter of a thoracic aortic aneurysm over long periods of time.

The diagnosis of a thoracic aortic aneurysm is often made as an incidental finding on transthoracic echocardiography (dilated aortic root) or on trans esophageal echocardiography (enlarged ascending aorta or aortic arch). The definitive diagnosis is made using CT angiography but MRA is also an excellent test. Once diagonosed, serial CTA (or MRA) are recommended every 6-12 months.

Medical therapy for patients with a thoracic aortic aneurysm includes aggressive blood pressure control, smoking cessation, and aggressive lipid management.

Indications for surgical repair of a thoracic aortic aneurysm include rupture; symptoms such as pain consistent with impending rupture; aortic regurgitation; growth ≥ 0.5 – 1 cm/year; bicuspid aortic valve; asymptomatic patients with degenerative thoracic aneurysm, chronic aortic dissection, intramural hematoma, penetrating atherosclerotic ulcer, mycotic aneurysm, or pseudoaneurysm, who are otherwise suitable candidates once a TAA reaches a pre-specified size (>5 cm in the ascending aorta, >6 cm in the descending segment) referral for surgical or endovascular repair sholuld be initiated. Most patients undergo repair once they reach >5.5 cm diameter in the ascending aorta and > 6.5 cm in the descending thoracic aorta, respectively. Patients with marfan syndrome or other genetically mediated disorders (vascular ehlers-danlos syndrome, turner syndrome, bicuspid aortic valve, or familial thoracic aortic aneurysm and dissection) should undergo elective operation at smaller diameters (4.0 to 5.0 cm depending on the condition. To avoid acute dissection or rupture, adult patients with loeys-dietz syndrome should undergo surgery for an aortic diameter of >4.4 to 4.6 cm. If a marfan syndrome patient is contemplating pregnancy, they should undergo aortic root replacement if the diameter is greater than 4 cm, and patients undergoing aortic valve repair or replacement and who have an ascending aorta or aortic root of greater than 4.5 cm should be considered for concomitant repair of the aortic root or replacement of the ascending aorta. A woven dacron tube graft is most commonly used in the repair of thoracic aortic aneurysms.

Template:WH Template:WS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2] Mohammed Salih, MD. [3]

An aneurysm occurs when a part or entire circumference of the vessel is pathologically dilated. A true aneurysm involves all three layers of the vessel, whereas pseudoaneurysm is characterized by disruption of the intima and media, and the dilated segment of the aorta is lined by adventitia alone. Thoracic aortic aneurysm (TAA) is a clinically silent and potentially fatal disease whose pathophysiology is poorly understood. Application of data derived from animal models and human tissue analysis of abdominal aortic aneurysms may prove misleading given current evidence of structural and biochemical aortic heterogeneity above and below the diaphragm. Genetic predisposition is more common in TAA and includes multi-faceted syndromes such as Marfan, Loeys-Dietz, and type IV Ehlers-Danlos as well as autosomal-dominant familial patterns of inheritance. Investigation into the consequences of these known mutations has provided insight into the cell signaling cascades leading to degenerative remodeling of the aortic medial extracellular matrix (ECM) with TGF-β playing a major role. Targeted research into modifying the upstream regulation or downstream effects of the TGF-β1 pathway may provide opportunities for intervention to attenuate TAA progression.

• The clinical manifestations of thoracic aortic aneurysms depends on hemo-dynamic factors as well as factors intrinsic to individual arterial components.
• Cystic medial necrosis is the most common pathology associated with ascending aortic aneurysms, whereas atherosclerosis is most frequently involved in the arch and descending aorta.
• The aortic aneurysms associated with marfan syndrome grow at a faster rate and are more prone to rupture.
• Most thoracic aneurysms are asymptomatic. However, the enlarging aorta can compress adjacent organs and cause symptoms like chest pain, dyspnea, hoarseness of voice, cough and dysphagia. Also symptoms of congestive heart failure can occur from severe aortic regurgitation and congestion of head, neck and upper extremities from superior vena cava compression.^[1][2]

• Increased activity of certain enzymes causes degradation of elastin and collagen in the arteries. This leads to loss of elasticity, weakens the aortic wall and causes it to dilate.^[3]
• Moreover, the part of aorta below the origin of renal arteries has less amount of elastin compared to collagen, accounting for increased frequency of aneurysms in this area^[4].
• In patients with marfan’s syndrome there is a defect on chromosome 15 that is associated with impaired fibrillin synthesis, which is the core protein of microfibrils. Frequently among patients with marfan’s syndrome there is cystic medial degeneration^[5].

• The aorta being a low resistance circuit, repeated trauma from a reflected wave results in dilatation^[6].
• Systemic hypertension accelerates the process of dilatation of aorta and contributes to the formation of aneurysms^[7][8][9].

• FBN1: This is one of the genes involved in marfan’s syndrome^[10][11][12].

• TGFBR1: This is one of the genes involved in loeys-dietz syndrome^[13].

• TGFBR2: This is one of the genes involved in loeys-dietz syndrome^[14].

• COL3A1: This is one of the genes involved in ehlers danlos syndrome^[15].

• ACTA2: This is one of the genes involved in familial thoracic aortic aneurysm and dissection (FTAAD)^[16].

• During embryologic development, the ascending and arch aorta to the ligamentum arteriosum formed by cells from the neural crest, and the media^[17].
• It grows by assembling sequential lamellar units to reach a total of 55-60 by adulthood^[18].
• It always maintaining a constant ratio of aortic diameter to medial thickness^[19].
• Interestingly, that ratio remains consistent during abdominal aortic growth as well, but in that region the precursor cells originate in the mesoderm and the number of lamellar units remains constant while the thickness of each unit is expanded during maturation^[20].
• This disparity in aortic cellular origin and segmental growth patterns contributes to differences in and extracellular matrix (ECM) microfibril density and VSMC reactivity to vasoactive growth factors , with downstream effects on susceptibility to aneurysmal degeneration^[21].

Images shown below are courtesy of Professor Peter Anderson DVM PhD and published with permission © PEIR, University of Alabama at Birmingham, Department of Pathology

On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Template:WH Template:WS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2] Mohammed Salih, MD. [3]

Two of the most common causes of thoracic aorta aneurysm are Marfan’s syndrome and atherosclerosis. In some centers, a prior history of dissection with aneurysmal dilation is the most common cause of surgical repair.

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

• Aortic dissection

• Aortic dissection^[1]
• Atherosclerosis
• Marfan’s syndrome

• Ankylosing spondylitis
• Aortic dissection
• Aortic stenosis
• Aortitis
• Aortic valve replacement
• Arterial tortuosity syndrome
• Atherosclerosis
• Bacterial infection, often following valvular endocarditis

1. Salmonella
2. Staphylococcus aureus
3. Staphylococcus epidermidis
4. Streptococcus
5. Tuberculosis

• Behcet’s disease
• Bicuspid aortic valve
• Ehlers-Danlos syndrome
• Familial thoracic aortic aneurysms and dissections
• Giant cell arteritis
• Loeys-Dietz syndrome
• Marfan’s syndrome
• Quaternary syphilis
• Reactive arthritis
• Rheumatoid arthritis
• Rheumatoid vasculitis
• Septic embolism
• Systemic hypertension
• Takayasu’s arteritis
• Temporal arteritis
• Traumatic – Sudden deceleration
• Turner’s syndrome
• Wegener’s granulomatosis

• Ankylosing spondylitis
• Atherosclerosis
• Bacterial infection, often following valvular endocarditis

1. Staphylococcus aureus^[2]
2. Staphylococcus epidermidis
3. Salmonella
4. Streptococcus
5. Tuberculosis^[3]

• Behcet’s disease^[4]
• Giant cell arteritis^[5]
• Previous injury to the aorta such as an aortic dissection
• Syphilis^[6]
• Takayasu’s arteritis^[7]
• Traumatic – sudden deceleration

• Familial thoracic aortic aneurysms and dissections^[8]
• Bicuspid aortic valve with post-stenotic dilation due to turbulence^[9]

• Marfan’s syndrome: Aortic root dilation with or without associated aortic regurgitation occurs in 75%-80% of marfan’s patients^[10].
• Loeys-Dietz syndrome^[11]
• Ehlers-Danlos syndrome
• Turner’s syndrome^[12]

Template:WH Template:WS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2] Associate Editor(s)-in-Chief: Mohammed Salih, MD. [3]

Thoracic aortic aneurysms are often asymptomatic and as a result can be easily missed. If chest pain is present, it is critical to differentiate a thoracic aortic aneurysm with dissection from other potential life-threatening diseases.

• Abdominal aortic aneurysms ^[1]
• Acute myocardial infarction ^[2]
• Congestive heart failure
• Aortic regurgitation
• Blunt chest trauma
• Hypertensive emergency
• Hemothorax
• Pneumothorax
• Pericarditis
• Pulmonary embolism
• Cardiac tamponade
• Superior vena cava syndrome

Thoracic aortic aneurysm should be differentiated from other diseases presenting with chest pain, shortness of breath and tachypnea. The differentials include the following:^{[3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22]}

Template:WH Template:WS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2] Mohammed Salih, MD. [3]

Thoracic aortic aneurysms are relatively uncommon (6 to 10 new ones per 100,000 person years) and are less prevalent than abdominal aortic aneurysm. Thoracic aortic aneurysms are generally diagnosed after the sixth and seventh decades of life. Although men are affected 2 to 4 times as often as women, women are at higher risk of rupture by a factor 6.8.

• TAAs are relatively uncommon with an estimated incidence between 6 and 10 new aneurysms per 100,000 person-years. According to a study by Beckerstaff et al.,^[1] the incidence of thoracic aortic aneurysms was reported to be 5.3 per 100,000 per year. Another study done by Clouse et al. showed the incidence to be 10.4 per 100,000 per year.^[2]
• However, the incidence and prevalence of TAD has been increasing in the past years. The annual number of surgeries performed on the aorta have increased, along with improved post- surgical and long term survival.^[3][2]

• TAAs are usually diagnosed after the sixth and seventh decade of life.

• Males are affected approximately two to four times more often than females.

• Thoracic aortic aneurysm is more common in caucasians.

Template:WH Template:WS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Mohammed Salih, MD. [2]

Hypertension and cigarette smoking are the most important risk factors, though the importance of genetic factors in the development of thoracic aortic aneurysm (such as familial thoracic aortic aneurysm; familial aortic dissection) has been increasingly recognized. Approximately 10% of patients may have other family members who have aortic aneurysms. It is also important to note that individuals with a history of aneurysms in other parts of the body have a higher chance of developing a thoracic aortic aneurysm.

Thoracic aortic aneurysm risk factors include:^{[1][2][3][4][5][6][7][8]}

• Smoking or chewing tobacco
• High blood pressure
• Bicuspid aortic valves
• Atherosclerosis (buildup of plaque in the arteries that can damage the lining)
• Gender: Aortic aneurysms are three times more prevalent in males versus females.
• Race: Aortic aneurysms are more frequent in Caucasian individuals versus other races.
• Individuals who have a family history of aortic aneurysms have a much higher risk of rupture and tend to develop aneurysms at a younger age.
• Chronic obstructive pulmonary disease
• Previous repair of a thoracic aorta aneurysm^[9]
• Turners syndrome^[10]

Template:WH Template:WS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2]; Raviteja Guddeti, M.B.B.S. [3] Mohammed Salih, MD. [4]

Screening for TAA is not recommended in the general population. However, certain population substrates, such as those with history of marfan’s syndrome, turner’s syndrome, ehlers-danlos type IV syndrome, familial thoracic aortic disease syndromes, bicuspid aortic valve, takayasu arteritis, giant cell arteritis, loeys-dietz syndrome or a confirmed genetic mutation known to predispose to aortic aneurysms and aortic dissections (TGFBR1, TGFBR2, FBN1, ACTA2, or MYH11) should have imaging study to screen for TAAs. First-degree relatives of people with thoracic aortic aneurysm or dissection should have aortic imaging to identify asymptomatic disease. Patients with high risk syndromes such as marfan’s syndrome and loeys-dietz syndrome should undergo complete aortic imaging at initial diagnosis and 6 months thereafter to establish if enlargement is occurring.

People diagnosed with marfan syndrome should immediately have an echocardiogram to measure the aorta, and followed up 6 months later to check for aortic enlargement.^[1] Annual imaging is recommended for patients with marfan syndrome if stability of the aortic diameter is documented. If the maximal aortic diameter is 4.5 cm or greater, or if the aortic diameter shows significant growth from baseline, more frequent imaging should be considered (Level of Evidence: C).

Patients with loeys-dietz syndrome or a confirmed genetic mutation known to predispose to aortic aneurysms and aortic dissections (TGFBR1, TGFBR2, FBN1, ACTA2, or MYH11) should undergo complete aortic imaging at initial diagnosis and 6 months thereafter to establish if enlargement is occurring.

Patients with turner syndrome should undergo imaging of the heart and aorta for evidence of bicuspid aortic valve, coarctation of the aorta, or dilatation of the ascending thoracic aorta. If initial imaging is normal and there are no risk factors for aortic dissection, repeat imaging should be performed every 5 to 10 years or if otherwise clinically indicated. If abnormalities exist, annual imaging or follow-up imaging should be done.

Template:WH Template:WS

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aarti Narayan, M.B.B.S [2] Mohammed Salih, MD. [3]

Thoracic aortic aneurysms typically expand slowly at a rate of approximately 0.1-0.2 cm/year. Aortic dissection and aortic rupture are the two most feared complications of an aortic aneurysm. The five-year survival of patients with a thoracic aortic aneurysm is 56%. The following are associated with a poorer prognosis: the presence of diastolic dysfunction; trauma as a cause of the aneurysm; the presence of coronary artery disease and the presence of carotid artery disease.

Thoracic aneurysms enlarge at a more rapid rate than abdominal aneurysms (0.42 vs 0.28 cm/yr), with aneurysms of the aortic arch growing at ~ 0.56 cm/yr. Aneurysms that are 5-6 cm in diameter have a faster rate of growth and a greater tendency to rupture than smaller ones.^[1]

• Aortic dissection and aortic rupture are the two most feared complications of an aortic aneurysm. Patients who have a prior dissection as a cause of an aneurysm are at increased risk of rapid expansion and re-dissection of the aneurysm.^{[2][3][4][5][6][7]}
• Aortic regurgitation
• Congestive heart failure

Shown below is the annual risk of thoracic aortic rupture, dissection or death for different diameters of thoracic aortic aneurysms. This draft forms the basis for performing surgery when the aorta is 5.0 to 6 cm in diameter depending upon whether the patient has Marfan syndrome or not.

The five-year survival of patients with a thoracic aortic aneurysm is 56%. The principal causes of death due to thoracic aneurysmal disease are dissection and rupture. Women face a 6.8 fold higher risk of aortic rupture. Once rupture occurs, the mortality rate is 50–80%. Most deaths in patients with the Marfan syndrome are the result of aortic disease. It is estimated that up to 47,000 people die each year from all types of aortic disease (thoracic and abdominal aortic aneurysms combined)^[8][9].

Factors associated with a worse prognosis are:

• Diastolic dysfunction
• Traumatic aneurysm
• Associated coronary artery disease
• Carotid artery disease

Template:WH Template:WS