PA26.1-2 | Atherosclerosis & Aneurysms — Summary & Reflection

REFLECT

Revisit the case from the opening hook: the 62-year-old smoker with Type A dissection.

1. Which of his risk factors (smoking, hypertension, age) contributed to the cystic medial degeneration and intimal tear? Could atherosclerosis have played a direct role in the dissection itself?
2. The woman with the ruptured AAA had a 6-month warning but the family declined surgery. Using Laplace's Law, explain why the rupture was almost inevitable if the AAA continued to grow untreated.
3. If you were counselling a 55-year-old male ex-smoker attending your clinic, what screening test would you recommend, at what diameter threshold would you refer for surgery, and what medical measures would you prescribe to slow aneurysm progression?

Write your answers in your notebook before checking the summary — this active retrieval step is the most effective memory consolidation strategy known.

KEY TAKEAWAYS

Arteriosclerosis is the umbrella term (three types: atherosclerosis, arteriolosclerosis, Mönckeberg). Arteriolosclerosis has two patterns — hyaline (benign HTN/DM) and hyperplastic/onion-skin (malignant HTN).

Atherosclerosis is driven by endothelial injury (HTN, smoking, dyslipidaemia, diabetes) → LDL entry and oxidation → macrophage foam cell formation → fatty streak → SMC migration/proliferation → fibrous atheromatous plaque. Risk factors: dyslipidaemia (esp. ↑LDL), HTN, smoking, DM (modifiable); age, sex, genetics (non-modifiable).

The atheromatous plaque has a fibrous cap (SMCs, collagen) + lipid/necrotic core. Vulnerable plaques have thin caps and large cores. Distribution: infrarenal aorta > coronary > popliteal > carotid > circle of Willis.

Complications of atherosclerosis: plaque rupture/thrombosis (→ MI, stroke), intraplaque haemorrhage, calcification, atheroembolism, aneurysm, progressive stenosis.

Aneurysm = ≥1.5× normal diameter dilation. True (all three layers) vs false (pseudoaneurysm, adventitia/haematoma only). Fusiform = circumferential (AAA); saccular = one-sided (berry, syphilitic).

Laplace's Law: T = Pr/w → dilation is self-reinforcing; rupture risk rises exponentially with radius.

AAA: infrarenal, fusiform, atherosclerotic, male>65+smoker. Complications: rupture (fatal triad: back pain + pulsatile mass + hypotension), embolism, compression.

Aortic dissection: intimal tear → blood in media → false lumen. Substrate: cystic medial degeneration (Marfan/HTN). Stanford A (ascending) = surgical emergency; Type B (descending) = medical. Complications: tamponade, AR, MI, stroke.

Other aneurysms: Syphilitic (thoracic, vasa vasorum endarteritis, AR); Berry (circle of Willis, SAH); Charcot-Bouchard (brain, HTN, ICH); Mycotic (septic emboli, any artery).