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Aortic Aneurysm for USMLE Step 1 & COMLEX-USA Level 1

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Overview of Aortic Aneurysm
    • Definition: Aortic aneurysm refers to a segmental, full-thickness dilation of the aorta, exceeding 50% of its normal diameter due to weakening of the vessel wall.
    • Types:
    • Abdominal Aortic Aneurysm (AAA)
    • Thoracic Aortic Aneurysm (TAA)
    • Most Common Site: Abdominal aorta, particularly below the renal arteries (infrarenal aneurysm).
    • Pathogenesis:
    • Atherosclerosis is the most common cause of AAA.
    • Cystic medial necrosis (connective tissue disease) is a cause of TAA.
    • Risk Factors:
    • Smoking (strongest risk factor for AAA)
    • Hypertension
    • Advanced age
    • Male gender
    • Family history of aneurysms
    • Genetic disorders (e.g., Marfan syndrome, Ehlers-Danlos syndrome for TAA)
Clinical Features
    • Asymptomatic: Often found incidentally on imaging.
    • Symptomatic:
    • AAA: Abdominal or back pain, pulsatile abdominal mass.
    • TAA: Chest pain, shortness of breath, hoarseness (due to compression of the recurrent laryngeal nerve).
    • Complications:
    • Rupture: Life-threatening condition causing severe pain and hemorrhagic shock.
    • Compression of nearby structures: May lead to symptoms like hoarseness, difficulty swallowing, or back pain.
    • Thromboembolism: Aneurysms can cause distal embolization.
Diagnostic Approach
    • Imaging:
    • Ultrasound: Screening tool for AAA, especially in men aged 65-75 who have smoked.
    • CT angiography: Provides detailed information about the size and extent of both AAA and TAA.
    • MRI: Occasionally used but less common than CT.
    • Physical Exam:
    • Pulsatile abdominal mass: Seen in AAA but often difficult to detect in overweight individuals.
Treatment
    • Small Aneurysms (<5.5 cm):
    • Conservative management with risk factor modification (e.g., smoking cessation, blood pressure control).
    • Regular imaging follow-up.
    • Large Aneurysms (>5.5 cm) or Rapidly Expanding:
    • Surgical intervention is recommended.
    • Open repair vs. endovascular aneurysm repair (EVAR) for AAA.
    • Open surgery or stent-grafting for TAA.
Essential Points
    • Smoking cessation is the most important modifiable risk factor for preventing progression of AAA.
    • Screening for AAA is recommended in men aged 65-75 years who have a history of smoking.
    • Surgical repair is indicated for aneurysms larger than 5.5 cm or those that are rapidly expanding.
    • Rupture risk increases with aneurysm size, and AAA rupture is a medical emergency with a high mortality rate.
    • Genetic syndromes like Marfan and Ehlers-Danlos are important to recognize as they predispose to TAA.