Aortic aneurysm and dissection for ABIM

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Aortic aneurysm and aortic dissection for the American Board of Internal Medicine (ABIM) Exam

Aortic Aneurysm

An aortic aneurysm is an abnormal dilation of the aorta, typically classified by location as either thoracic aortic aneurysm (TAA) or abdominal aortic aneurysm (AAA).
AAA is more common, with most cases occurring below the renal arteries.

Non-modifiable: Advanced age, male gender, and family history of aneurysms.
Modifiable: Smoking (strongest modifiable risk factor), hypertension, and atherosclerosis.
Associated conditions: Marfan syndrome, Ehlers-Danlos syndrome, and bicuspid aortic valve.

Aneurysms result from the weakening of the aortic wall, primarily due to changes in elastin and collagen integrity.
Inflammatory and proteolytic processes contribute to aortic wall degradation and progressive dilation, especially in AAAs.

Often asymptomatic until rupture, especially with AAA.
Symptomatic AAA: Can present as a pulsatile abdominal mass or with nonspecific symptoms like back or abdominal pain.
TAA symptoms: May involve chest, back, or neck pain; symptoms can vary based on compression of surrounding structures (e.g., hoarseness from recurrent laryngeal nerve compression).

Imaging:
Ultrasound: First-line imaging for screening and diagnosis of AAA.
CT Angiography (CTA): Preferred for detailed assessment of aneurysm size and extent, especially in TAA.
Screening: Recommended one-time screening with abdominal ultrasound for men aged 65-75 who have smoked.

Medical Management: Includes blood pressure control (typically with beta-blockers) and smoking cessation.
Surveillance: Regular imaging for aneurysms below the surgical threshold.
Surgical Intervention:
Indications: AAA >5.5 cm in men or >5.0 cm in women, TAA >5.5-6.0 cm depending on specific factors, or rapid growth (>0.5 cm/year).
Procedures: Open surgical repair or endovascular aneurysm repair (EVAR) for AAA and thoracic endovascular aortic repair (TEVAR) for TAA.

Aortic Dissection

An aortic dissection is a tear in the intima of the aorta, allowing blood to flow between the layers of the aortic wall and creating a true and false lumen.

Stanford Classification:
Type A: Involves the ascending aorta and is a surgical emergency.
Type B: Involves the descending aorta, often managed medically unless complications arise.
DeBakey Classification:
Type I: Involves both ascending and descending aorta.
Type II: Confined to the ascending aorta.
Type III: Involves only the descending aorta, distal to the left subclavian artery.

Similar to aortic aneurysms, with additional emphasis on hypertension (most common risk factor), connective tissue disorders, and a bicuspid aortic valve.
Other factors include prior cardiac surgery, high-intensity weightlifting, and cocaine use.

Begins with an intimal tear, leading to high-pressure blood entry into the aortic wall.
This dissection process can compromise blood flow to branches of the aorta, causing ischemia in various organs.

Classic symptom: Sudden, severe chest or back pain described as “tearing” or “ripping.”
Other symptoms vary based on the site of dissection and compromised structures:
Ascending aorta involvement: Chest pain, possible signs of aortic regurgitation (e.g., diastolic murmur).
Descending aorta involvement: Back pain and symptoms of ischemia in lower limbs or abdominal organs.

Type A: High risk of aortic rupture, cardiac tamponade, acute aortic regurgitation, and myocardial ischemia due to coronary artery involvement.
Type B: May lead to malperfusion syndromes affecting renal, gastrointestinal, or lower extremity circulation.

Imaging:
CT Angiography: Gold standard for rapid diagnosis, allowing visualization of the true and false lumens.
MRI: Alternative when CTA is contraindicated (e.g., renal insufficiency), though it is less available in emergencies.
Transesophageal echocardiography (TEE): Valuable in unstable patients or those in the OR, particularly for ascending dissections.
Lab findings: Elevated D-dimer may be supportive but is nonspecific.

Type A Dissection:
Requires emergent surgical repair to prevent fatal complications (e.g., rupture, tamponade).
Type B Dissection:
Medical Therapy: Blood pressure control is crucial, often with intravenous beta-blockers followed by vasodilators as needed.
Surgical or Endovascular Repair: Indicated for complications such as persistent pain, progression, end-organ ischemia, or rupture.
Blood Pressure Goals: Target systolic blood pressure (SBP) of 100-120 mmHg with beta-blockers (e.g., esmolol) to reduce aortic shear stress.

Key Points

Defined by abnormal aortic dilation; classified as AAA (more common) and TAA.
Risk factors include smoking, hypertension, and connective tissue disorders.
Commonly asymptomatic but may cause abdominal/back pain if symptomatic.
Diagnosed with imaging (e.g., ultrasound, CTA), with screening recommended for older male smokers.
Managed based on size and growth rate, with surgical repair for large or symptomatic aneurysms.

Life-threatening tear in the aortic wall, creating a true and false lumen.
Classified by Stanford (Type A and B) and DeBakey systems.
Sudden, severe chest or back pain is typical; complications vary by dissection type.
Imaging with CTA is essential for diagnosis; TEE is valuable in certain acute settings.
Type A requires emergent surgery; Type B may be managed medically unless complicated.