Aneurysms and dissections

Basics - The Great Dilations

• Aneurysm: Localized abnormal dilation of a blood vessel.
  • True Aneurysm: Involves all three layers of the vessel wall (intima, media, adventitia).
    • Saccular: Spherical outpouching (e.g., berry aneurysm).
    • Fusiform: Circumferential, spindle-shaped dilation.
  • False Aneurysm (Pseudoaneurysm): A breach in the vessel wall leading to an extravascular hematoma that communicates with the lumen.

• Dissection: Blood enters the arterial wall itself, splitting the laminar planes of the media to form a blood-filled channel.

⭐ Hypertension is the single most important predisposing factor for aortic dissection.

📌 Primary Pathogenesis: Aneurysm → Atherosclerosis-induced wall weakening. Dissection → Chronic hypertension causing medial degeneration.

Abdominal Aortic Aneurysm (AAA) - Belly's Ballooning Bomb

• Patho: Atherosclerosis-driven chronic inflammation → ↑ Matrix Metalloproteinases (MMPs) → elastin/collagen degradation → aortic wall weakening & dilation.
• Risks: 📌 Smoking, Male, Age >60, Strong family hx, Hypertension. Smoking is the #1 modifiable risk factor.
• Presentation: Mostly asymptomatic. Classic triad for rupture: hypotension, pulsatile abdominal mass, and severe back/flank pain.
• Dx: Ultrasound for screening, initial diagnosis, and monitoring size. CT angiography for surgical planning.
• Rx:
  • Monitor if < 5.5 cm.
  • Elective repair if > 5.5 cm, growing > 0.5 cm/6 mo, or symptomatic.

⭐ Exam Favorite: Most AAAs occur infrarenally (below the renal arteries).

Aortic Dissection - The Great Divide

• Pathophysiology: A tear in the aortic intima allows blood to dissect through the media, creating a false lumen. Primarily driven by hypertension.
• Risk Factors: Chronic hypertension (most common), Marfan syndrome, Ehlers-Danlos, bicuspid aortic valve, trauma.
• Clinical Presentation: Sudden, severe "tearing" or "ripping" chest pain radiating to the back. May present with syncope, stroke, or MI.
  • Asymmetric BP (>20 mmHg difference) or pulses between arms.

⭐ A blood pressure differential of >20 mmHg between arms is a highly specific sign for aortic dissection.

• Management:
  • Stanford A (Proximal): Surgical emergency.
  • Stanford B (Distal): Medical management (IV beta-blockers, e.g., labetalol) unless complicated (malperfusion, rupture).

Other Aneurysms - Thoracic & Berry Tales

• Thoracic Aortic Aneurysm (TAA)

  • Etiology: Atherosclerosis, cystic medial degeneration (e.g., Marfan syndrome), or tertiary syphilis (obliterative endarteritis of vasa vasorum → "tree bark" aorta).
  • Clinical: Often asymptomatic; may cause respiratory or esophageal symptoms.

• Berry (Saccular) Aneurysm

  • Location: Occur at arterial branch points in the Circle of Willis; anterior communicating artery is most common.
  • Associations: ADPKD, Ehlers-Danlos, Marfan syndrome.
  • Rupture: Leads to subarachnoid hemorrhage (SAH).

⭐ A ruptured berry aneurysm classically presents as a sudden, severe "worst headache of my life."

High‑Yield Points - ⚡ Biggest Takeaways

• Abdominal Aortic Aneurysm (AAA), the most common true aneurysm, is linked to atherosclerosis and is typically infrarenal. Rupture triad: hypotension, pulsatile mass, flank pain.
• Aortic dissection is driven by hypertension and presents as tearing chest pain radiating to the back. Marfan syndrome is a key risk factor in the young.
• Tertiary syphilis classically causes Thoracic Aortic Aneurysm (TAA) by disrupting the vasa vasorum.
• Berry aneurysms are associated with ADPKD and risk subarachnoid hemorrhage.