Aortic aneurysm

aortic-aneurysm

Definition: Aortic aneurysm is an abnormal dilatation of aortic wall. An aortic aneurysm is a general term for an enlargement (dilation) of the aorta  to greater than 1.5 times normal size. While the cause of an aneurysm may be multifactorial, the end result is an underlying weakness in the wall of the aorta at that location. The aneurysm may occasionally cause pain, which is a sign of impending rupture. When rupture occurs, massive internal hemorrhage results, and, unless treated immediately, shock and death can occur within minutes to hours.

Classification:

Aortic aneurysms are classified by their location on the aorta.

  • An aortic root aneurysm, or aneurysm of the sinus of Valsalva.
  •  Thoracic aortic aneurysms  are found within the chest; these are further classified as ascending, aortic arch, or descending aneurysms.
  • Abdominal aortic aneurysms, “AAA” or “Triple A,” the most common form of aortic aneurysm, involve that segment of the aorta within the abdominal cavity. Thoracoabdominal aortic aneurysms involve both the thoracic and abdominal aorta. There are other classifications that might help treatment.

Aetiology & types of aneurysm:

  1. Non-specific aneurysms-Affects
  • Infrarenal abdominal aorta. (common site)
  • Suprarenal abdominal aorta.
  • Descending thoracic aorta.
  • Ascending aorta.
  1. Collagen vascular diseases:
  • Marfan’s syndrome.
  • Ehlers-Danlos syndrome.
  • Cystic medial necrosis.
  1. Aortitis:
  • Takayasu’s disease.
  • Rieter’s syndrome.
  • Giant cell arteritis and
  • Ankylosing spondylitis.
  1. Thoracic aneurysms.
  2. Abdominal aortic aneurysms.

Clinical features: Abdominal aortic aneurysm 3 times more commonly occurs in men than women, particularly those over 60 years of age.

Symptoms:

  1. Commonly asymptomatic (esp small aneurysms <5 cm in diameter).
  2. May present with central abdominal pain, backache, loin, iliac fossa or groin pain.
  3. May present acutely, with pain and hypotension form rupture.

Signs:

  1. Aneurysm may be palpable in abdominal aorta.
  2. Evidence of widespread vascular disease.
  3. Stigmata of distal embolisation.
  4. Haemodynamic collapse (hypotension, tachycardia, shock) with rupture of aneurysm.

Risk factors:

  1. CAD
  2. Hypertension
  3. Hypercholesterolemia
  4. Hyperhomocysteinemia
  5. Elevated C-reactive protein
  6. Tobacco  use
  7.  Peripheral vascular disease
  8.  Marfan syndrome
  9.  Ehlers Danlos type IV
  10. Bicuspid Aortic Valve

Pathophysiology: An aortic aneurysm can occur as a result of trauma, infection, or, most commonly, from an intrinsic abnormality in the elastin and collagen  components of the aortic wall.

Prevention: The risk of aneurysm enlargement may be diminished with attention to the patient’s blood pressure, smoking and cholesterol  levels. There have been proposals to introduce ultrasound scans  as a screening tool for those most at risk: men over the age of 65.The tetracycline  antibiotic  doxycycline  is currently being investigated for use as a potential drug in the prevention of aortic aneurysm due to its metalloproteinase  inhibitor and collagen stabilizing properties.

Management of abdominal aortic aneurysm:

  1. Symptoms of rupture:
  • Emergency surgical repair.
  1. Backache or abdominal pain:
  • Ultrasound, CT or angiography; consider surgery.
  1. Asymptomatic: Ultrasound
  • If < 4 cm,serial ultrasound + follow up.
  • If > 4 cm, consider surgery.

Treatment of choice: Open AAA repair is the established treatment of choice in both the elective and emergency setting and entails replacing the aneurismal segment with a prosthetic (usually Dacron)

The 30-days mortality (approximately)-

  • For elective asymptomatic AAA=5-8%
  • For emergency symptomatic AAA=10-20%
  • For rupture AAA=50%

Reference:

  1. Davidson’s Principles and Practice of Medicine, 21st edition.
  2. Wikipedia the free encyclopedia.

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