Back
ditki Logo
medical & biological sciences

Aortic aneurysm and dissection for USMLE 2

Start your One-Week Free Trial
Already subscribed? Log in »
Aortic aneurysm and aortic dissection for the USMLE Step 2 Exam
Aortic Aneurysm
  • Definition:
    • An aortic aneurysm is a focal dilation of the aorta, typically categorized by location as thoracic aortic aneurysm (TAA) or abdominal aortic aneurysm (AAA).
    • AAA is most common and usually occurs below the renal arteries.
  • Risk Factors:
    • Major Risk Factors: Age, male sex, smoking (most significant modifiable risk), and hypertension.
    • Associated Conditions: Marfan syndrome, Ehlers-Danlos syndrome, and bicuspid aortic valve.
  • Pathophysiology:
    • Aneurysms develop from the degeneration of the aortic wall, primarily due to the loss of elastin and collagen.
    • Chronic inflammation and atherosclerosis contribute to wall weakening, especially in AAAs.
  • Clinical Presentation:
    • Asymptomatic: Common until the aneurysm is large or ruptures.
    • Symptoms (if present): Back or abdominal pain; a pulsatile mass may be felt in the abdomen with AAA.
  • Diagnosis:
    • Imaging:
    • Ultrasound: First-line for AAA screening and diagnosis.
    • CT Angiography (CTA): Preferred for preoperative evaluation and assessing rupture risk, especially in symptomatic cases.
    • Screening: Recommended one-time ultrasound for men aged 65-75 who have ever smoked.
  • Management:
    • Medical Management: Smoking cessation, blood pressure control (often with beta-blockers).
    • Surveillance: Serial imaging for aneurysms under the surgical threshold.
    • Surgical Indications:
    • AAA: Repair indicated for aneurysms >5.5 cm in men, >5.0 cm in women, or rapidly expanding (>0.5 cm/year).
    • TAA: Intervention considered for aneurysms >5.5-6.0 cm, depending on factors like family history or connective tissue disorders.
    • Procedures: Open surgical repair or endovascular aneurysm repair (EVAR) for AAA, and thoracic endovascular aortic repair (TEVAR) for TAA.
Aortic Dissection
  • Definition:
    • Aortic dissection is a tear in the intima of the aorta, creating a false lumen through which blood flows, separating the layers of the vessel wall.
  • Classification:
    • Stanford Classification:
    • Type A: Involves the ascending aorta and is a surgical emergency.
    • Type B: Limited to the descending aorta, often managed medically unless complications occur.
Types of aortic dissection
  • Pathophysiology:
    • Dissections arise from an intimal tear that permits blood to enter and expand between layers of the aortic wall.
    • Risk Factors:
    • Hypertension: Most common predisposing factor.
    • Genetic Conditions: Marfan syndrome, Ehlers-Danlos syndrome.
    • Other Factors: Bicuspid aortic valve, prior cardiac surgery, and stimulant drug use (e.g., cocaine).
  • Clinical Presentation:
    • Classic Symptom: Sudden, severe “tearing” chest or back pain.
    • Type A Complications: Can lead to aortic regurgitation, myocardial ischemia, or cardiac tamponade.
    • Type B Complications: Possible ischemia of abdominal organs or lower limbs.
  • Diagnosis:
    • Imaging:
    • CT Angiography (CTA): Gold standard for diagnosis, showing the true and false lumens.
    • Transesophageal Echocardiography (TEE): Useful in unstable patients or in cases requiring rapid intraoperative assessment.
  • Management:
    • Type A Dissection: Requires emergent surgical repair to prevent fatal complications.
    • Type B Dissection:
    • Medical Management: Blood pressure control (target SBP <120 mmHg) with beta-blockers and vasodilators to reduce shear stress.
    • Endovascular Repair: Indicated if complications develop, such as persistent pain, malperfusion, or rupture.
Key Points
  • Aortic Aneurysm:
    • Commonly involves the abdominal aorta (AAA) and often remains asymptomatic until complications arise.
    • Major risk factors include smoking, age, and genetic conditions.
    • Managed based on size and growth rate; larger aneurysms require surgical intervention.
  • Aortic Dissection:
    • A life-threatening emergency with a tear in the aortic wall, classified as Stanford Type A (ascending aorta) or Type B (descending aorta).
    • Symptoms include acute, tearing chest or back pain, with CTA as the preferred diagnostic tool.
    • Type A dissections require immediate surgery, while Type B dissections are often managed with blood pressure control unless complications develop.

Related Tutorials