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.
2.
Collagen vascular diseases:
·
Marfan’s syndrome.
·
Ehlers-Danlos syndrome.
·
Cystic medial necrosis.
3.
Aortitis:
·
Takayasu’s disease.
·
Rieter’s syndrome.
·
Giant cell arteritis and
·
Ankylosing spondylitis.
4.
Thoracic aneurysms.
5.
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.
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.
2.
Backache or abdominal pain:
·
Ultrasound, CT or angiography; consider
surgery.
3.
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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