How should an adult with a fusiform abdominal aortic aneurysm (AAA) be medically managed, surveilled, and when is surgical or endovascular aneurysm repair (EVAR) indicated?

Management of Fusiform Abdominal Aortic Aneurysm

Immediate Assessment and Risk Stratification

For fusiform AAA, management is determined by aneurysm diameter, sex, and growth rate, with elective repair indicated at ≥5.5 cm in men or ≥5.0 cm in women. 1

Initial Diagnostic Approach

• Use duplex ultrasound (DUS) as the primary diagnostic and surveillance modality, with 100% specificity and positive predictive value 1, 2
• Define AAA as infrarenal aortic diameter ≥3.0 cm or >1.5 times the adjacent normal segment 1, 2
• Obtain cardiovascular CT (CCT) or MRI if DUS provides inadequate measurement 1
• Perform complete vascular evaluation including the entire aorta, as 27% of AAA patients have concurrent thoracic aneurysms 2
• Assess femoro-popliteal segment with DUS, as 14% have concomitant peripheral aneurysms 1, 2

Size-Based Surveillance Strategy

The surveillance intervals differ by sex due to women having four-fold higher rupture risk at similar diameters 1, 3:

For Men:

• 25-29 mm: DUS every 4 years 1, 3
• 30-39 mm: DUS every 3 years 1, 2
• 40-49 mm: DUS annually 1, 2
• 50-55 mm: DUS every 6 months 1, 2

For Women:

• 25-29 mm: DUS every 4 years 1, 3
• 30-39 mm: DUS every 3 years 1, 3
• 40-44 mm: DUS annually 1, 2
• 45-50 mm: DUS every 6 months 1, 2

Accelerated Surveillance Triggers:

• Shorten intervals to every 3-6 months if rapid growth occurs: ≥10 mm per year or ≥5 mm per 6 months 1, 3
• Consider repair at these growth rates even below standard size thresholds 1

Medical Management: Cardiovascular Risk Reduction is Primary

The 10-year risk of death from cardiovascular causes is up to 15 times higher than the risk of aorta-related death in AAA patients. 2, 3 Therefore, aggressive cardiovascular risk factor modification takes priority over aneurysm-specific interventions.

Mandatory Medical Interventions:

• Smoking cessation: The single most critical modifiable risk factor for aneurysm growth and rupture 2, 4
• Intensive lipid management: Target LDL-C <1.4 mmol/L (<55 mg/dL); statins reduce cardiovascular mortality and slow AAA growth 2, 5
• Blood pressure control: Use ACE inhibitors or ARBs as indicated for hypertension, though these do not affect AAA growth 5
• Single antiplatelet therapy: Low-dose aspirin if concomitant coronary artery disease (OR 2.99), not associated with higher rupture risk 1, 2

Important Medication Caveat:

• Avoid fluoroquinolones in AAA patients; use only if compelling indication with no alternative 1, 2

Indications for Elective Repair

Size-Based Thresholds (Class I, Level A):

• Men: ≥5.5 cm diameter 1, 2
• Women: ≥5.0 cm diameter 1, 2

These thresholds are based on multiple RCTs (UKSAT, ADAM, CAESAR, PIVOTAL) showing no survival benefit from early repair of smaller aneurysms, as annual rupture risk for AAA <5 cm is only 0.5-5% 2, 6

Additional Repair Indications:

• Symptomatic AAA: Repair regardless of diameter (abdominal or back pain attributable to aneurysm) 1, 2, 7
• Rapid expansion: ≥10 mm per year or ≥5 mm per 6 months 1, 3
• Saccular morphology: Consider repair at ≥4.5 cm due to higher rupture risk 1, 7

Contraindication to Elective Repair:

• Do not repair in patients with limited life expectancy <2 years (Class III, Level B) 1, 7

Choice of Repair Technique

For patients with suitable anatomy and reasonable life expectancy >2 years, endovascular aneurysm repair (EVAR) should be preferred over open repair based on shared decision-making. 1, 3

EVAR Advantages:

• Reduces perioperative mortality to <1% compared to 4-5% with open repair 1, 3
• Lower 30-day morbidity and mortality (OR 0.36; 95% CI 0.2-0.66) 1
• Shorter hospital stay and faster recovery 8
• Preferred for high perioperative risk patients 1

EVAR Disadvantages and Long-Term Considerations:

• Higher rate of secondary interventions (hazard ratio 2.1; 95% CI 1.7-2.7) 1
• After 8 years, increased risk of aneurysm-related death (hazard ratio 5.12), rupture (OR 5), and rupture-related death (OR 3.6) compared to open repair 1
• Requires lifelong surveillance due to endoleak risk 1
• Must adhere to manufacturer's instructions for use (Class I, Level B-NR) 1

Open Repair Indications:

• Unsuitable anatomy for EVAR 1
• Patient preference after shared decision-making 1
• Younger patients with long life expectancy where durability is paramount 6

Post-EVAR Surveillance Protocol

Lifelong surveillance is mandatory after EVAR due to ongoing risk of endoleaks, migration, and late rupture. 1, 7

Surveillance Schedule:

• 30 days post-EVAR: CCT plus DUS/contrast-enhanced ultrasound to assess intervention success 7, 3
• 12 months post-EVAR: Repeat imaging 2, 7
• Years 1-5: Annual DUS/contrast-enhanced ultrasound 7
• After 5 years: Consider CCT or MRI every 5 years if DUS used for routine surveillance 1, 2

Endoleak Management:

• Type I and III endoleaks: Prompt reintervention required to achieve seal 7, 3
• Type II endoleaks: May seal spontaneously; intervene only if associated with aneurysm sac growth ≥10 mm 7
• DUS is 95% accurate for measuring sac diameter and 100% specific for detecting Type I and III endoleaks 2

Post-Open Repair Surveillance

• 1 month post-operatively: Initial follow-up imaging 7
• If stable: Imaging every 5 years thereafter 7

Emergency Management of Ruptured AAA

For ruptured AAA with suitable anatomy, endovascular repair is recommended over open repair to reduce perioperative morbidity and mortality (Class I, Level B). 1

• Mortality risk from rupture is 75-90% 1, 2, 3
• Immediate surgical evaluation required for clinical triad: abdominal/back pain, pulsatile mass, hypotension 7
• EVAR reduces perioperative mortality compared to open repair in rupture setting 1

Common Pitfalls to Avoid

• Do not perform routine coronary angiography and systematic revascularization prior to AAA repair in patients with chronic coronary syndromes (Class III, Level C) 1, 7
• Do not use different size thresholds for EVAR versus open repair; indications are the same 6
• Do not neglect cardiovascular risk management focusing only on aneurysm size, as cardiovascular death risk far exceeds rupture risk 2, 3
• Do not discontinue surveillance after EVAR, as late complications and rupture can occur years later 1