Aortic Aneurysms

Intro & Classification - Aorta's Big Bulge

• Aortic Aneurysm: Permanent localized dilatation of aorta; diameter > 1.5x normal expected diameter.
  • Normal aorta: Thoracic ≈ 3 cm, Abdominal ≈ 2 cm.
• Classification by Location:
  • Abdominal Aortic Aneurysm (AAA): Most common, typically infrarenal.
  • Thoracic Aortic Aneurysm (TAA).
• Classification by Morphology:
  • Fusiform: Symmetrical, spindle-shaped (common).
  • Saccular: Asymmetrical, berry-like outpouching.
• Wall Involvement:
  • True Aneurysm: Involves all three layers (intima, media, adventitia).
  • Pseudoaneurysm (False): Contained rupture; wall not all 3 layers.

⭐ Majority (≈90%) of AAAs are infrarenal.

Etiology & Risks - Weak Wall Woes

• Primary: Atherosclerotic degeneration (most common).
  • Wall weakening: Elastin/collagen breakdown in media.
  • Enzymatic degradation: ↑ Matrix Metalloproteinases (MMPs).
  • Inflammation & oxidative stress contribute.
• Key Risk Factors:
  • Advanced age (>60-65 years).
  • Male sex (M:F ≈ 4:1).
  • 📌 Smoking: Strongest modifiable risk; dose-dependent.
  • Hypertension.
  • Family history of AAA.
  • Hyperlipidemia.
• Genetic Links:
  • Marfan (FBN1), Ehlers-Danlos Type IV (COL3A1), Loeys-Dietz (TGFBR1/2).
• Less Common:
  • Infections (mycotic aneurysms).
  • Vasculitis (e.g., Takayasu).
  • Trauma.

⭐ Smokers have up to 5x increased risk of developing AAA and faster expansion.

Clinical Features - Silent Threats Scream

• Often asymptomatic, discovered incidentally.
• Thoracic Aortic Aneurysm (TAA):
  • Chest/back pain (most common).
  • Dyspnea, cough, hoarseness (recurrent laryngeal nerve).
  • Dysphagia (esophageal compression).
  • Superior Vena Cava (SVC) syndrome.
• Abdominal Aortic Aneurysm (AAA):
  • Most are asymptomatic until rupture.
  • Pulsatile abdominal mass (often found on routine exam).
  • Abdominal or back pain (constant, gnawing; suggests expansion/impending rupture).
  • Limb ischemia (embolic phenomena).

• Rupture Triad (AAA):
  • Sudden severe pain (abdominal/back/flank).
  • Hypotension.
  • Pulsatile abdominal mass.

⭐ Most AAAs are infrarenal. Rupture into the retroperitoneum is more common than free intraperitoneal rupture, leading to a contained hematoma initially before potential free rupture and rapid exsanguination. 📌 RUPTURE = Renal colic-like pain, Unstable vitals, Pulsatile mass, Tender abdomen, Urge to defecate, Radiating pain to back/groin, Ecchymosis (Grey Turner's/Cullen's sign - late).

Diagnosis & Screening - Spotting the Swell

• Clinical: Often asymptomatic. Pulsatile abdominal mass.
• Imaging:
  • Ultrasound (USG): Primary for diagnosis & screening; measures diameter accurately.
  • CT Angiography (CTA): Gold standard for pre-operative planning; details anatomy, extent, vessel involvement.
  • MRA: CTA alternative (e.g., renal issues, contrast allergy).
  • AXR: Incidental finding (calcified aortic outline).
• Screening (USPSTF):

⭐ AAA Definition: Focal aortic dilation ≥ 3.0 cm OR > 1.5 times normal diameter (normal aorta ≈ 2.0 cm).

Management - Repair & Rescue

• Indications for Repair (AAA):
  • Symptomatic (pain, embolism)
  • Diameter >5.5 cm (men), >5.0 cm (women)
  • Rapid expansion: >0.5 cm in 6 months or >1 cm/year
  • Complications: dissection, pseudoaneurysm
• Repair Options:
  • Endovascular Aneurysm Repair (EVAR): Preferred for suitable anatomy; lower perioperative mortality.
  • Open Surgical Repair: For complex anatomy, younger patients, connective tissue disorders.
• Ruptured AAA (Rescue):
  • Emergency surgery (EVAR or open)
  • Permissive hypotension (SBP 70-90 mmHg) until aortic control.
  • ABCDE, IV access, cross-match blood.

⭐ Post-EVAR, endoleaks are a common complication requiring surveillance and potential re-intervention. Type II endoleak (branch vessel backflow) is the most frequent.

High‑Yield Points - ⚡ Biggest Takeaways

• Abdominal Aortic Aneurysms (AAA) are most common, typically infrarenal.
• Atherosclerosis is the primary cause; smoking is a major risk factor.
• Often asymptomatic; rupture triad: pain, hypotension, pulsatile mass.
• Ultrasound for screening (men 65-75 with smoking history) & surveillance.
• CT angiography for pre-operative planning.
• Repair (open or EVAR) if diameter > 5.5 cm, rapidly expanding, or symptomatic.
• Law of Laplace links size to ↑rupture risk.