Aneurysms and Dissection

Aneurysms Basics - Ballooning Blood Vessels

• Definition: Permanent, localized abnormal dilation of blood vessel or heart.
• Classification:
  • True: All 3 wall layers (intima, media, adventitia) or thinned heart wall involved.
    • E.g., Atherosclerotic, congenital, syphilitic, ventricular.
  • False (Pseudoaneurysm): Wall defect → extravascular hematoma; outer wall is compressed perivascular tissue.
    • E.g., Post-MI rupture (contained), anastomotic site leak.
• Shapes:
  • Saccular: Spherical outpouching (e.g., berry).
  • Fusiform: Diffuse, circumferential dilation.
• Pathogenesis: Weakened wall + ↑stress.
  • Intrinsic: Marfan (FBN1), Loeys-Dietz (TGF-βR), Ehlers-Danlos (collagen).
  • Acquired: Atherosclerosis (commonest), HTN, syphilis, trauma, mycotic infections.

⭐ Laplace’s Law ($T \propto P \times r / w$): ↑radius ($r$) → ↑wall tension ($T$) → ↑rupture risk.

Key Aneurysm Types - Notable Nasty Nebulae

• Abdominal Aortic Aneurysm (AAA)
  • Location: Infrarenal aorta (most common).
  • Etiology: Atherosclerosis. Risks: Smoking, male >50y, family Hx, HTN.
  • Clinical: Often asymptomatic; pulsatile abdominal mass. Rupture triad: severe pain, hypotension, pulsatile mass.
  • Screen: US for men 65-75y (ever smoked). Intervention: >5.5 cm or rapid growth (>0.5 cm/6mo).
• Thoracic Aortic Aneurysm (TAA)
  • Etiology: HTN (descending), cystic medial degeneration (ascending; Marfan, Ehlers-Danlos), atherosclerosis, syphilis (obliterative endarteritis → tree-bark aorta).
  • Clinical: Chest/back pain, dyspnea, cough, dysphagia, hoarseness (recurrent laryngeal nerve).
• Berry (Saccular) Aneurysm
  • Location: Circle of Willis, arterial bifurcations (e.g., AComA). 📌 Berries hang in Circles.
  • Assoc: ADPKD, Ehlers-Danlos IV, Marfan syndrome.
  • Rupture → Subarachnoid Hemorrhage (SAH) - "thunderclap headache".

  ⭐ Most common cause of spontaneous (non-traumatic) subarachnoid hemorrhage.

• Mycotic Aneurysm
  • Definition: Localized arterial dilation from vessel wall infection (bacterial/fungal).
  • Pathogenesis: Septic emboli (e.g., Infective Endocarditis), Salmonella in atheromatous plaques.

Aortic Dissection - The Great Divide

• Patho: Intimal tear → blood dissects into aortic media → false lumen formation.
• Risks: Hypertension (>70%, primary), Marfan/Ehlers-Danlos syndromes, bicuspid aortic valve, cocaine, trauma, pregnancy.
• Clinical: Sudden, severe "tearing" or "ripping" chest/back pain (often interscapular). Asymmetric BP/pulses. Neurological deficits.
• Dx: CT Angiography (CTA) is gold standard. CXR may show widened mediastinum.
• Rx:
  • Immediate BP & HR control (IV β-blockers: e.g., labetalol, esmolol; target SBP 100-120 mmHg, HR <60 bpm).
  • Vasodilators (e.g., nitroprusside) after β-blockade if SBP remains high.

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

• Classification (Stanford):
  • Type A: Involves ascending aorta. Surgical emergency.
  • Type B: Descending aorta only. Medical management if uncomplicated.
• (DeBakey Classification):
  • Type I: Ascending aorta, arch, & descending.
  • Type II: Ascending aorta only.
  • Type III: Descending aorta only (IIIa thoracic, IIIb thoracoabdominal).

Clinical Approach - Spot, Sort, Solve

• Spot (Suspect):
  • Aneurysm: Often silent; pulsatile abdominal mass (AAA); rupture → severe pain, shock.
  • Dissection: Sudden, severe tearing chest/back pain; unequal pulses/BP; neuro deficits.
• Sort (Diagnose):
  • Imaging: CTA (gold standard for both); US (AAA screen); TEE (dissection, if unstable).
  • Aneurysm: Size & location critical.
  • Dissection: Stanford A (ascending aorta) vs B (descending).
• Solve (Manage):
  • Priorities: Airway, Breathing, Circulation (ABCs); IV access.
  • General: Aggressive BP control (target SBP 100-120 mmHg in dissection).
  • Specifics: See flowchart for key decisions.

⭐ Aortic dissection: Immediate goal is ↓dP/dt & ↓BP; IV beta-blockers (e.g., Labetalol) first-line, target HR <60 bpm.

High‑Yield Points - ⚡ Biggest Takeaways

• AAA, most common, linked to atherosclerosis; typically infrarenal, rupture risk ↑ with size.
• Syphilitic aneurysms: ascending aorta, vasa vasorum damage, "tree barking" appearance.
• Berry aneurysms (Circle of Willis): associated with ADPKD, Ehlers-Danlos; risk SAH.
• Aortic dissection: intimal tear, blood splits media; hypertension is the major risk.
• Marfan & Ehlers-Danlos predispose via cystic medial degeneration (weakened media).
• Stanford Type A (ascending aorta) is surgical emergency; Type B (descending) often medical.