Thoracic aortic aneurysm pathophysiology

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Thoracic aortic aneurysm Microchapters

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Patient Information

Overview

Historical Perspective

Classification

Pathophysiology

Causes

Differentiating Thoracic Aortic Aneurysm from other Diseases

Epidemiology and Demographics

Risk Factors

Screening

Natural History, Complications and Prognosis

Diagnosis

Diagnostic Study of Choice

History and Symptoms

Physical Examination

Laboratory Findings

Electrocardiogram

General Approach to Imaging in Thoracic Aortic Aneurysm

Chest X Ray

MRI

CT

Echocardiography

Other Imaging Findings

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Treatment

Medical Therapy

Surgery

Primary Prevention

Secondary Prevention

Endovascular Stent Grafting

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Management during Pregnancy

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

Overview

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.

Genetics

FBN1

This is one of the genes involved in Marfan's syndrome.

TGFBR1

This is one of the genes involved in Loeys-Dietz syndrome.

TGFBR2

This is one of the genes involved in Loeys-Dietz syndrome.

COL3A1

This is one of the genes involved in Ehlers Danlos syndrome.

ACTA2

This is one of the genes involved in familial thoracic aortic aneurysm and dissection (FTAAD).

Pathophysiology

  • 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.

Elastin and collagen

  • 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.
  • 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.
  • 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.

Hemodynamic factors

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

Gross Pathology

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






















References

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