Overview
This lecture explains the definition, types, causes, locations, risk factors, complications, and diagnosis of aneurysms, emphasizing their clinical importance and potential consequences.
Definition and Classification of Aneurysms
- "Aneurysm" means abnormal dilation of a blood vessel, usually when the diameter increases by 1.5 times the normal size.
- Aneurysms can occur in any artery (e.g., aorta, femoral, iliac, popliteal, cerebral) and less commonly in veins.
- Two main types: true aneurysms (involve all vessel wall layers) and pseudoaneurysms (blood escapes vessel and pools, contained by tissue).
- True aneurysms subtypes: fusiform (symmetrical bulge), saccular and berry (asymmetrical bulge).
Causes and Risk Factors
- Weakness in vessel walls leads to aneurysm formation; high pressure worsens dilation due to Laplace’s law.
- Causes of wall weakness include atherosclerosis (plaque buildup), hypertension, and genetic connective tissue disorders.
- Vasa vasorum ischemia (often from hypertension or tertiary syphilis) can weaken large arterial walls.
- Mycotic aneurysms result from bacterial or fungal infections damaging vessel walls.
- Common risk factors: male sex, age over 60, smoking, hypertension, and genetic syndromes (Marfan, Ehlers-Danlos).
Common Locations
- Most arterial aneurysms occur in the aorta, especially the abdominal section (60% abdominal, 40% thoracic).
- 95% of abdominal aortic aneurysms are between the renal arteries and the aortic bifurcation.
Clinical Features and Complications
- Intact aneurysms are often asymptomatic but can compress nearby structures, causing symptoms.
- Main danger is rupture, leading to severe internal bleeding and downstream tissue ischemia.
- Thoracic aneurysms can cause aortic insufficiency (valve dysfunction, possible brassy cough) if near the aortic valve.
- Ruptured cerebral aneurysms cause subarachnoid hemorrhage, sudden headache, and stiff neck.
- Blood clots can form within aneurysms, potentially leading to embolism and ischemia.
- Classic signs of ruptured abdominal aneurysm: severe flank/chest/abdominal pain, pulsating mass, and hypotension.
Diagnosis and Treatment
- Many aneurysms are found incidentally with imaging studies like ultrasound, CT, or MRI.
- Large or symptomatic aneurysms may require surgical intervention to prevent rupture.
Key Terms & Definitions
- Aneurysm — abnormal localized dilation of a blood vessel.
- True aneurysm — dilation involving all vessel wall layers.
- Pseudoaneurysm — blood collection outside vessel wall, contained by tissue.
- Fusiform aneurysm — symmetrical aneurysm bulging on all sides.
- Saccular/Berry aneurysm — asymmetrical bulge on one side of the vessel.
- Vasa vasorum — small blood vessels supplying thick arteries.
- Mycotic aneurysm — aneurysm due to infection.
- Laplace's law — tension on vessel wall increases as diameter increases.
- Aortic insufficiency — improper closure of aortic valve due to aortic dilation.
Action Items / Next Steps
- Review lecture slides and assigned readings on vascular pathology.
- Practice identifying aneurysm types and complications on imaging examples if provided.
- Prepare for quiz questions on aneurysm definitions, causes, locations, and clinical presentations.