What is the recommended screening protocol for a widening aorta (aortic dilatation)?

Recommended Screening Protocol for Aortic Dilatation

The recommended screening protocol for a widening aorta (aortic dilatation) should be based on the location of the dilatation, initial aortic diameter, and patient risk factors, with imaging frequency increasing as the aortic diameter enlarges. 1

Initial Evaluation

• For initial diagnosis of thoracic aortic dilatation, transthoracic echocardiography (TTE) is recommended to assess aortic valve anatomy and function, aortic root, and ascending aorta diameters 1
• CT or MRI of the thoracic aorta is indicated when the diameter and morphology of the aortic root, ascending aorta, or both cannot be assessed accurately or completely by TTE 1
• A baseline assessment of all segments of thoracic aorta, aortic valve anatomy, and aortic valve function is essential for establishing proper follow-up 1

Surveillance Protocols by Aortic Location

Thoracic Aortic Aneurysm (TAA) Surveillance

• After initial diagnosis, imaging is required at 6-12 months to determine the rate of aortic enlargement 1
• If stable, subsequent imaging frequency depends on location and diameter:
  • For aortic diameters <45 mm with stability over time: annual imaging 1
  • For aortic diameters 45-49 mm: imaging every 6-12 months 1
  • For aortic diameters 50-55 mm: imaging every 6 months 1
• If rapid expansion (≥3 mm per year) is observed or the aorta approaches surgical threshold, more frequent evaluation every 6 months is recommended 1

Abdominal Aortic Aneurysm (AAA) Surveillance

• For AAA of 3.0-3.9 cm: surveillance ultrasound every 3 years 1
• For men with AAA of 4.0-4.9 cm and women with AAA of 4.0-4.4 cm: annual surveillance ultrasound 1
• For men with AAA ≥5.0 cm and women with AAA ≥4.5 cm: surveillance ultrasound every 6 months 1
• If AAA is inadequately defined with ultrasound, surveillance CT is recommended 1

Imaging Modality Selection

• Thoracic aorta:

  • TTE is appropriate for aortic root and proximal ascending aorta surveillance 1
  • CMR or CT is recommended for surveillance of aneurysms at the distal ascending aorta, aortic arch, descending thoracic aorta, or thoracoabdominal aortic aneurysm 1
  • For patients with stable aortic dimensions, CMR rather than CT is reasonable to minimize radiation exposure for long-term surveillance 1

• Abdominal aorta:

  • Ultrasound is the standard for surveillance imaging of the abdominal aorta 1
  • CT provides superior visualization when ultrasound is inadequate or when the AAA meets criteria for repair 1
  • MRI is a reasonable alternative when there is a contraindication to CT or to lower cumulative radiation risk 1

Special Considerations

Genetic Disorders

• Marfan Syndrome:

  • More frequent surveillance may be needed, with surgical intervention reasonable at aortic diameter ≥5.0 cm 1

• Loeys-Dietz Syndrome:

  • Baseline TTE followed by repeat imaging at 6 months, then annual surveillance if stable 1
  • Annual surveillance imaging of the affected aorta and arteries with MRI or CT 1
  • Baseline MRI or CT from head to pelvis to evaluate the entire aorta and its branches 1

• Bicuspid Aortic Valve (BAV):

  • Surveillance serial imaging by TTE is recommended in BAV patients with aortic diameter >40 mm 1
  • If stable, imaging every 2-3 years is appropriate 1
  • Screening of all first-degree relatives by TTE is recommended 1

Common Pitfalls and Caveats

• TTE is not recommended for surveillance of aneurysms in the distal ascending aorta, aortic arch, or descending thoracic aorta due to limited visualization 1
• Small stature patients (e.g., Turner syndrome) may have significant dilatation at smaller absolute diameters; using aortic size index (diameter/body surface area) is preferred in these cases 2, 3
• Risk factors that may accelerate aortic growth include smoking, hypertension, and diabetes, which may warrant more frequent surveillance 1
• Follow-up should be conducted with the same imaging technique and at the same center to ensure measurement consistency 1

By following these evidence-based screening protocols, clinicians can effectively monitor aortic dilatation and intervene appropriately to prevent catastrophic complications such as aortic dissection or rupture.