Thoracic Aortic Aneurysms

Thoracic aortic aneurysm (TAA) is the abnormal dilation of a segment of the thoracic aorta, usually the ascending aorta. Most TAAs are due to degenerative aortic disorders, commonly in patients > 65 years of age. Genetic TAAs account for 20% of cases and are frequently found in younger patients. Most TAAs are asymptomatic (incidentally found in imaging) but could present with symptoms from its effects on surrounding structures. Aortic rupture is a life-threatening emergency. Among diagnostic imaging studies, computed tomography (CT) angiography is the most widely utilized. In asymptomatic cases, aortic expansion is monitored. Operative repair is recommended for symptomatic TAAs and increasing aortic diameter (criteria varies with location and underlying condition).

Last update:

Table of Contents

Share this concept:

Share on facebook
Share on twitter
Share on linkedin
Share on reddit
Share on email
Share on whatsapp

Overview

Definitions

Thoracic aortic aneurysm (TAA)

  • Dilation of the thoracic aorta by > 50% of its normal diameter
  • Diameter affected by age, sex, and body surface area
  • Ascending aortic aneurysm: approximately > 5 cm
  • Descending aortic aneurysm: approximately > 4 cm

Types

  • True aneurysm: dilation of the aorta by > 50% of normal diameter, involving all 3 layers (intima, media, adventitia)
    • Fusiform-shaped: bulges on all sides of the aorta (more common)
    • Saccular-shaped: bulges on one side 
  • Pseudoaneurysm:
    • Dilation caused by a disruption of the aortic wall
    • Extravasated blood contained by periarterial connective tissue, not by all wall layers
    • Extravascular hematoma communicates with intravascular space.

Location

  • Ascending aorta: area from aortic annulus to the innominate artery/brachiocephalic trunk 
  • Aortic arch: area where innominate artery, left carotid, and left subclavian artery originate
  • Descending aorta: beyond left subclavian artery
  • Thoracoabdominal aortic aneurysms: most descending TAAs are contiguous with abdominal aortic aneurysms (AAAs).

Epidemiology

  • TAA: 15th-leading cause of death for patients > 65 years old
  • TAAs are less common than AAAs.
  • 60% of TAAs are localized in the ascending aorta
  • Majority of TAAs are degenerative, so risk factors include smoking, hypertension, and hypercholesterolemia.
  • More common in men and in those of advanced age

Etiology

  • Degenerative disorders:
    • Most common cause of AAA and TAA
    • Risk factors:
      • Atherosclerosis
      • Hypertension
      • Advanced age
      • Hypercholesterolemia
      • Cigarette smoking
  • Genetic or developmental disorders:
    • Most common cause of TAA in patients < 65 years old
    • Disorders:
      • Marfan’s syndrome
      • Turner’s syndrome
      • Ehlers-Danlos syndrome
      • Bicuspid aortic valve
      • Loeys-Dietz syndrome
      • Familial thoracic aortic aneurysm and dissection (TAAD) 
  • Vasculitis
    • Giant cell arteritis (most common inflammatory cause of TAA)
    • Takayasu’s arteritis
    • Rheumatoid arthritis
    • Spondyloarthritides
    • Behcet’s disease
  • Infection
    • Syphilis (tertiary)
    • Tuberculosis
    • Mycotic aneurysm (Salmonella, staphylococcal, streptococcal, fungal infection)
  • Trauma

Pathophysiology

Contributing factors

  • Embryology:
    • Embryologic origin can affect response of aorta to stimuli (growth factors and cytokines).
    • Ascending aorta and aortic arch: derived from neural crest cells
    • Descending aorta: derived from mesoderm
  • Genetics:
    • 20% from genetic syndromes (Marfan’s syndrome, Ehlers-Danlos syndrome)
  • Structure and growth of artery:
    • Wall thickness of aorta decreases from the thoracic area to the distal aorta
    • Thoracic aorta:
      • Greater elastin and collagen content than AAA
      • Has avascular and vascular zones in media
      • Grows by ↑ number of lamellar units (elastin, collagen, vascular smooth muscle cells): more lamellar units
  • Atherosclerosis:
    • TAA can occur without plaque deposition.
    • In TAA: low likelihood of progression of fatty streak to atheroma
  • Inflammation
    • Affects both TAA and AAA
    • Predominantly T cells and macrophages; TAA noted to have proinflammatory cytokines
  • Proteolysis by matrix metalloproteinases (MMPs): 
    • ↑ breakdown of extracellular matrix
    • In TAA: MMP-9 (from fibroblasts and smooth muscle cells)

Pathogenesis

  • Regular vascular remodeling (synthesis, degradation, and repair) of extracellular matrix (ECM) components maintain the functional and structural integrity of the artery.
  • Above factors, in combination with age and environment (i.e., smoking, infection, trauma) → result in breakdown of ECM → arterial medial degeneration → weakened vascular wall → dilation
  • The dilation + rapid expansion of aorta: ↑ risk of rupture or aortic dissection
  • Widening of the vessel disrupts laminar blood flow → turbulence + inflammation→ possible thrombus formation within the vessel (with risk of embolism)

Clinical Presentation

Symptoms

  • Commonly asymptomatic (due to slow expansion rate)
  • Often discovered on echocardiography or computed tomography (CT) scan
  • Symptoms indicate expansion of the aneurysm → ↑ rupture or dissection risk
  • Ascending aortic aneurysm:
    • Left recurrent laryngeal nerve compression: hoarse voice
    • Phrenic nerve compression: hemidiaphragmatic paralysis → shortness of breath 
    • Tracheobronchial tree compression: cough, wheezing, dyspnea, and hemoptysis
    • Esophageal compression: dysphagia
    • Compression of central veins or superior vena cava (SVC): thromboembolism or SVC syndrome 
    • Aortic regurgitation due to aortic root dilatation, annulus distortion: heart failure
    • Coronary compression: chest pain (myocardial infarction)
    • Aortic arch branch vessel compression: neurologic symptoms from cerebrovascular thromboembolism 
  • Descending aortic aneurysm: 
    • Symptoms occur when dilation is large.
    • Erosion of the spine: upper back pain 
    • Dissection of aneurysm: back pain or epigastric pain
  • Aneurysmal rupture:
    • Life-threatening emergency!
    • TAA rupture, often into left chest or pericardium: severe chest pain, hypotension, shock

Signs

  • Vital signs: 
    • Normal blood pressure if TAA not enlarged
    • Tachycardia, hypotension in rupture or dissection
  • SVC syndrome: facial, neck, or upper extremity swelling (for vein distention)
  • Can have aortic regurgitation murmur (early diastolic decrescendo murmur)
  • Pulse deficit; peripheral pulses diminished in aneurysmal rupture
  • Focal neurologic deficits in cerebrovascular thromboembolic event

Diagnosis

History

  • Family history of aortic pathology
  • Risk factors (hypertension, smoking, hypercholesterolemia)
  • Known history of aneurysm in other areas (e.g., cerebral aneurysm)
  • Prior aortic dissection
  • Aortic valve disease, bicuspid aortic valve
  • Other conditions: Marfan’s syndrome, Loeys-Dietz syndrome, Ehlers-Danlos syndrome, and other connective tissue disease
  • Chest trauma

Diagnostic tests

  • Chest X-ray:
    • Widened mediastinum
    • Large aortic knob
    • Deviation or compression of trachea or left mainstem bronchus
    • Note: cannot distinguish TAA from a tortuous aorta
  • CT or magnetic resonance angiography (CTA/MRA):
    • CT: most widely used test for TAA
    • For diagnosis and preoperative planning
    • Detects aortic diameter, vessel anatomy, dissection, rupture, thrombus
    • In acutely symptomatic patients, CT is used.
    • MRA: no ionizing radiation and contrast, but not readily available in some centers
  • Transesophageal (TEE) or transthoracic echocardiography (TTE):
    • Evaluates aortic valve/other cardiac disease as cardiac motion affects CT/MRA
    • TTE for initial study but TEE preferred in acute symptoms with hypotension
  • Arteriography:
    • Shows extent and branch involvement of aneurysm; cannot define size
    • Has risk of contrast adverse reaction/s and radiation

Management

Non-surgical management of aortic aneurysms

  • Reduce cardiovascular risk:
    • Smoking cessation
    • Hypertension control:
      • Blood pressure control recommended in all aortic aneurysms
      • In TAA: beta blockers/angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs)
      • In Marfan’s syndrome: 
        • Should be on beta blockers (to ↓ aortic root dilatation) unless contraindicated 
        • Other option: ARBs 
    • Lipid control with statins (target low-density lipoproteins (LDL) < 70 mg/dL)
  • Avoid fluoroquinolones (may ↑ risk of dissection or rupture)
  • Surveillance (see table)
    • TAA: asymptomatic ascending aortic aneurysm < 5.5 cm or descending aortic aneurysm < 6 cm: aortic imaging (CTA/MRA) periodically
Management of asymptomatic patientsDegenerative ascending or aortic root aneurysmDescending aortic aneurysm
Annual CTA/MRA
(echocardiography to follow valvular disease if needed)
3.5–4.4 cm4–4.9 cm
Biannual (every 6 months) CTA/MRA
(echocardiography to follow valvular disease if needed)
4–4.9 cm5–6 cm
Consider elective repair ≥ 5.5 cm
Rapid expansion (> 0.5 cm/year)
≥ 4.5 cm if aortic valve surgery or coronary bypass needed
≥ 5.5 cm, consider thoracic endovascular repair (TEVAR);
≥ 6 cm (TEVAR not technically possible) for open surgery;
Rapid expansion (> 0.5 cm/year)

Surgical management

Indications for operative repair

  • TAA rupture: emergency repair
  • Symptomatic TAA
  • Asymptomatic ascending TAA
    • Aortic (ascending and aortic arch) diameter is ≥ 5.5 cm
    • Patients undergoing aortic valve repair/replacement or coronary artery bypass: aortic diameter > 4.5 cm
    • Patients with Marfan’s syndrome or other genetically mediated disorders with ascending TAA 4–5 cm (depending on condition) should undergo elective operation.
  • Asymptomatic descending TAA:
    • TEVAR should be considered when surgically possible. 
    • When diameter is ≥ 5.5 cm, TEVAR is considered.
    •  If TEVAR not possible, open surgery considered when diameter is ≥ 6 cm
    • When intervention is indicated in cases of Marfan’s syndrome or other elastopathies (4–6 cm depending on condition), open surgery is considered.
  • Aneurysm growth rate of > 0.5 cm/year, in an aorta < 5 cm

Operative options

  • Open surgical repair
    • Surgery depends on location (ascending TAA involves full cardiopulmonary bypass and cardioplegia) 
    • General indications: 
      • Genetically mediated syndromes
      • Aneurysms in aortic arch and ascending aorta; chronic dissection/intramural hematoma in ascending aorta
      • Bicuspid aortic valve
      • For descending aortic aneurysms when TEVAR is not technically possible
    • Not for patients with high operative risk
    • Complications: postoperative bleeding, reduced perfusion (stroke, paraplegia/paresis, visceral/renal/limb ischemia)
    • Surveillance: before discharge, obtain CTA/MRA; repeat at 1-, 6-, and 12-month intervals
  • TEVAR:
    • Placement of graft via iliac or femoral arteries
    • Requires normal aortic areas for graft attachment (proximal and distal landing zones for the stent graft) 
    • Indication(s): degenerative descending aortic aneurysm; also for blunt thoracic aortic injury, aortic dissection, penetrating ulcer
    • Lower perioperative morbidity and mortality; majority discharged 24 hours post-surgery
    • Possible complications: 
      • Spinal/cerebral/limb/visceral ischemia 
      • Late outcomes related to the device (endoleak, migration, malposition, injury to other structures)
    • Requires endograft surveillance (CTA) at 1 month, 6 months post-surgery, then annually (more frequently as indicated)

Differential Diagnosis

Differential diagnoses of TAA include the following conditions:

  • Aortic dissection: occurs when the inner coat (tunica intima) of the aortic wall develops a fissure that causes blood to enter the media layer of the wall to form a channel of blood. The pressure causes the layers to be forced apart and causes severe pain, characteristically known as a tearing pain. Computed tomography angiogram will differentiate dissection from rupture of the aorta.
  • Acute pericarditis: an inflammation of the pericardium that may be idiopathic or caused by infection, autoimmune disease, radiation, surgery, myocardial infarction, neoplasms, or drugs. Acute pericarditis is the most common type and manifests as fever, pleuritic chest pain that increases with lying supine, and an audible pericardial rub.
  • Heart failure: the inability of the heart to supply the body with normal cardiac output to meet metabolic needs. Risk factors include hypertension, diabetes mellitus, and coronary artery disease. Echocardiography can confirm the reduced ejection fraction (EF). 
  • Infective endocarditis: an inflammatory disease of the interior heart lining usually caused by Staphylococci, Streptococci, and Enterococci. Most commonly affects the cardiac valves. Diagnosis is by history, blood cultures, and echocardiography.
  • Myocardial infarction: ischemia of the myocardial tissue due to a complete obstruction or drastic constriction of the coronary artery. This is usually accompanied by an increase in cardiac enzymes, typical electrocardiogram (ECG) changes, and chest pain. 
  • Pulmonary embolism: a potentially fatal clinical condition that occurs as a result of mechanical obstruction of the pulmonary artery or its branches by a thrombus, air, or fat. Diagnosis established by CT pulmonary angiogram.
  • SVC syndrome: a condition caused by the obstruction of blood flow through the SVC. Most often manifests in patients with a thoracic malignancy that produces compression over the vessel or a thrombus.

References

  1. Black, J., Burke, C., Hoekstra, J. , Aldea, G. & Collins, K. (Eds.). (2020). Epidemiology, risk factors, pathogenesis and natural history of thoracic aortic aneurysm. UpToDate. Retrieved 28 Aug 2020, from https://www.uptodate.com/contents/epidemiology-risk-factors-pathogenesis-and-natural-history-of-thoracic-aortic-aneurysm
  2. Burke, C., Hoekstra, J., Connolly, H., Aldea, G., Verrier, E., Collins, K. (Eds). (2020). Management of thoracic aortic aneurysm. UpToDate. Retrieved 30 Aug 2020, from https://www.uptodate.com/contents/management-of-thoracic-aortic-aneurysm-in-adults
  3. Erbel R, Aboyans V, Boileau C, et al. (2014). ESC Guidelines on the diagnosis and treatment of aortic diseases: Document covering acute and chronic aortic diseases of the thoracic and abdominal aorta of the adult. The Task Force for the Diagnosis and Treatment of Aortic Diseases of the European Society of Cardiology (ESC). Eur Heart J .35:2873. https://www.escardio.org/Guidelines/Clinical-Practice-Guidelines/Aortic-Diseases
  4. Guoledge, J, Guo-Ping, S., Norman, P., Fitridge, R., Thompson, M. (2011). Pathogenesis of aortic aneurysm in Mechanisms of Vascular disease: A Reference Book for Vascular Specialists. Adelaide (AU): University of Adelaide Press. https://www.ncbi.nlm.nih.gov/books/NBK534278/
  5. Hiratzka LF, Bakris GL, Beckman JA, Bersin RM, Carr VF, Casey DE Jr, Eagle KA, Hermann LK, Isselbacher EM, Kazerooni EA, Kouchoukos NT, Lytle BW, Milewicz DM, Reich DL, Sen S, Shinn JA, Svensson LG, Williams, DM. (2010) ACCF/AHA/AATS/ACR/ASA/SCA/SCAI/SIR/STS/SVM Guidelines for the Diagnosis and Management of Patients With Thoracic Aortic Disease.  Circulation.121:e266. https://www.ahajournals.org/doi/10.1161/CIR.0b013e3181d4739e
  6. Mitchell, R., Halushka, M. (2020). In Kumar, V.; Abbas, A.; Aster, J.; Turner, J. (Eds.) Robbins and Cotran Pathologic Basis of Disease. (10th ed., pp.485-525). Elsevier, Inc.
  7. Munden, R., Carter, B., Chiles, C., MacMahon, H., Black, W., Ko, J., McAdams, H., Rossi, S., Leung, A., Boiselle, P., Kent, M., Brown, K., Dyer, D., Hatman, T., Goodman, E., Naidich, D., Kazerooni, E., Berland, L., Pandharipande, P. (2018). Managing Incidental findings on Thoracic CT: Mediastinal and Cardiovascular findings. Journal of the American College of Radiology; JACR. https://www.jacr.org/article/S1546-1440(18)30530-1/fulltext#secsectitle0080
  8. Ruddy, J., Jones, J., Ikonomidis, J. (2013). Pathophysiology of Thoracic Aortic Aneurysm. Prog Cardiovasc Dis.  56(1): 68–73. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3759819/
  9. Ruddy, J., Jones, J., Spinale, F., Ikonomidis, J.(2008). Regional Heterogeneity within the Aorta: relevance to Aneurysm disease. J Thorac Cardiovasc Surg. 136(5): 1123–1130. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2679174/
  10. Tseng, E., Mancini, M. (Ed.).(2019). Thoracic Aortic aneurysm. Medscape. https://emedicine.medscape.com/article/424904-overview
  11. Tseng, E., Bush, E., Talavers, F., Karwande, S. & Mancini, M. (Eds.). (2019). What are the guidelines for surgery for thoracic aortic aneurysm? Medscape. https://www.medscape.com/answers/424904-68907/what-are-the-guidelines-for-surgery-in-thoracic-aortic-aneurysm-taa

🍪 Lecturio is using cookies to improve your user experience. By continuing use of our service you agree upon our Data Privacy Statement.

Details