Follow-up Protocol for Dilated Ascending Aorta
The recommended follow-up for a dilated ascending aorta should be based on aortic diameter, growth rate, and underlying etiology, with imaging intervals ranging from 6 months to 3 years depending on these factors. 1, 2, 3
Initial Assessment
- Transthoracic echocardiography (TTE) is recommended at diagnosis to assess aortic valve anatomy, function, aortic root, and ascending aorta diameters 1
- Cardiovascular computed tomography (CCT) or cardiovascular magnetic resonance (CMR) is recommended to confirm TTE measurements, rule out aortic asymmetry, and determine baseline diameters for follow-up 1, 3
- CMR or CCT is required for surveillance of aneurysms at the distal ascending aorta, aortic arch, or descending thoracic aorta, as TTE is not recommended for these locations 1
Follow-up Intervals Based on Aortic Diameter (Non-Heritable Disease)
Root or Proximal Ascending Aorta:
- 40-44 mm: Baseline CCT/CMR and reimaging in one year 1, 3
- 45-49 mm: Confirm by CCT or CMR, then annual imaging 1, 3
- 50-54 mm: Imaging every 6 months until threshold for intervention is reached 1
- ≥55 mm: Consider surgical intervention 1, 3
Distal Ascending Aorta, Aortic Arch, or Descending Thoracic Aorta:
- Follow the same criteria as for 40-49 mm range above 1
- For 50-55 mm range: Reimage every 6 months until threshold for intervention is reached 1
Special Considerations Affecting Follow-up Frequency
- Growth rate ≥3 mm/year: More frequent monitoring (every 6 months) and consider earlier intervention 1, 3
- Stability in aortic diameters over years may allow lengthening of follow-up intervals, especially in non-genetic aneurysms <45 mm 1, 4
- Lower thresholds for intervention and more frequent monitoring should be considered with: 1, 3
Imaging Modality Selection
- TTE can be used for follow-up of aortic root and proximal ascending aorta if there is agreement between TTE and CCT/CMR measurements 1
- If there is a difference of ≥3 mm between TTE and CCT/CMR measurements, surveillance must be performed by CMR or CCT 1
- CMR is preferred over CCT for long-term follow-up in young patients to minimize radiation exposure 2, 3
Research Evidence on Growth Rates
- For moderately dilated ascending aorta (40-49 mm), the mean growth rate is approximately 0.3 ± 0.5 mm/year 4
- For ascending aorta ≥50 mm, the mean growth rate increases to 0.7 ± 0.9 mm/year 4
- Significant progression (diameter increase by ≥5 mm) occurs in only 3.4% of patients with 40-44 mm aortas and 5.6% of patients with 45-49 mm aortas over a mean follow-up of 4.3 years 4
- For a moderately dilated ascending aorta not exceeding 45 mm and stable in the first annual follow-up image, a 3- to 4-year interval may be reasonable before subsequent imaging 4
Post-Intervention Follow-up
- After open repair for thoracic aortic aneurysm, imaging is recommended within 1 month, then yearly for first 2 years, then every 5 years if stable 2
- After endovascular repair (TEVAR), follow-up imaging is recommended at 1 and 12 months post-operatively, then yearly until the fifth post-operative year if no abnormalities are documented 1
Pitfalls and Caveats
- Failure to use the same imaging technique and center for follow-up can lead to measurement inconsistencies 1
- Acute aortic dissection can occur before the maximal diameter reaches 55 mm or significant progression is observed (1% risk in one study) 4, 5
- Patients with bicuspid aortic valve require special attention due to associated aortopathy and potentially higher risk of complications 3, 6
- Patient compliance with follow-up programs is essential, as non-compliance is associated with higher rupture rates 2
By following these evidence-based recommendations for surveillance of dilated ascending aorta, clinicians can optimize patient outcomes while minimizing unnecessary imaging.