What is the management approach for a patient with an abdominal aortic aneurysm (AAA)?

Management of Abdominal Aortic Aneurysm

Elective repair is recommended when AAA diameter reaches ≥55 mm in men or ≥50 mm in women, with surveillance using duplex ultrasound at size-specific intervals for smaller aneurysms, combined with aggressive cardiovascular risk factor modification to reduce the substantially higher risk of death from cardiovascular causes compared to aneurysm rupture. 1

Initial Diagnosis and Assessment

Duplex ultrasound (DUS) is the primary screening and surveillance modality for AAA detection, with 100% specificity and positive predictive value. 1, 2 An AAA is defined as infrarenal aortic diameter ≥3.0 cm or >1.5 times the adjacent normal segment. 1, 2

When an AAA is identified at any location:

• Assess the entire aorta at baseline and during follow-up, as up to 27% of AAA patients have concurrent thoracic aneurysms 2
• Evaluate for femoro-popliteal aneurysms, present in up to 14% of AAA patients 2
• Obtain contrast-enhanced CT angiography (CTA) when repair thresholds are approached for preoperative planning, measuring diameter perpendicular to the longitudinal axis using 3D multiplanar reformatted images 1, 2

Surveillance Strategy Based on Size and Sex

The 2024 ESC guidelines provide a clear size-based surveillance algorithm that differs by sex due to women having a four-fold higher rupture risk at similar diameters: 1

For men:

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

For women:

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

Use CT or MRI if DUS does not allow adequate measurement of AAA diameter. 1

Shorten surveillance intervals if rapid growth occurs: ≥10 mm per year or ≥5 mm per 6 months, as this may trigger intervention even below size thresholds. 1, 2

Indications for Elective Repair

Size-based thresholds (Class I, Level A evidence):

• Men: ≥55 mm 1
• Women: ≥50 mm 1

These thresholds are based on multiple randomized trials (UKSAT, ADAM, CAESAR, PIVOTAL) demonstrating no survival benefit from early repair of AAAs <5.5 cm, as the annual rupture risk for aneurysms <5 cm is only 0.5-5%, making operative risk exceed rupture risk below these thresholds. 2

Additional repair indications:

• Rapid expansion: ≥0.5 cm in 6 months or ≥1 cm per year 2
• Symptomatic AAA (abdominal or back pain attributable to aneurysm): repair indicated regardless of diameter 1, 2
• Saccular morphology: consider repair at ≥45 mm due to higher rupture risk 3

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

Choice of Repair Technique

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

For elective repair, both open and endovascular approaches are acceptable (Class I, Level A), with EVAR reducing peri-operative mortality to <1% compared to open repair. 1, 3 Consider EVAR as preferred therapy based on shared decision-making for patients with suitable anatomy and reasonable life expectancy. 3

Open repair is reasonable for patients who cannot comply with the periodic long-term surveillance required after EVAR (Class IIa, Level C). 1

Technical considerations for EVAR:

• Stent-graft diameter should be oversized by 10-20% relative to proximal neck diameter 3
• Extensive mural thrombus (>90% circumference) in the proximal neck increases risk of type I endoleak and migration 3
• Completion angiography must confirm absence of endoleak and patency of all components 3

Medical Management: The Primary Focus

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 Therefore, optimal cardiovascular risk management is recommended for all AAA patients (Class I, Level C). 1, 2

Smoking cessation is the most critical intervention:

• Offer behavior modification, nicotine replacement, or bupropion 1
• Smoking is the most important modifiable risk factor for aneurysm growth and rupture 2

Blood pressure control:

• Perioperative beta-blockers are indicated to reduce adverse cardiac events and mortality in patients with coronary artery disease undergoing AAA repair (Class I, Level A) 1
• Beta-blockers may be considered to reduce aneurysm expansion rate (Class IIb, Level B) 1

Antiplatelet therapy:

• Consider single antiplatelet therapy (low-dose aspirin) if concomitant coronary artery disease is present (odds ratio 2.99) 2
• Low-dose aspirin is not associated with higher AAA rupture risk but could worsen prognosis if rupture occurs 1, 2

Lipid management:

• Intensive lipid management to LDL-C target <1.4 mmol/L (<55 mg/dL) is recommended 1

Avoid fluoroquinolones unless there is a compelling clinical indication with no reasonable alternative (Class IIb, Level B). 1, 2

Post-EVAR Surveillance

Perform 30-day imaging with CT plus DUS/contrast-enhanced ultrasound (CEUS) to assess intervention success. 1, 3

Follow-up schedule:

• 1 month and 12 months post-operatively 1, 3
• Then yearly until fifth post-operative year 3
• DUS is 95% accurate for measuring sac diameter and 100% specific for detecting type I and III endoleaks 2
• CT or MRI every 5 years is reasonable when DUS is used for routine surveillance 2

Re-intervene for type I or type III endoleaks to achieve seal. 3

Emergency Management

For patients presenting with the clinical triad of abdominal/back pain, pulsatile abdominal mass, and hypotension, immediate surgical evaluation is indicated (Class I, Level B). 1 This represents suspected ruptured AAA with 75-90% mortality risk. 1

Screening Recommendations

Men 60 years or older who are siblings or offspring of AAA patients should undergo physical examination and ultrasound screening (Class I, Level B). 1 The U.S. Preventive Services Task Force recommends men aged 65-75 years who have ever smoked should be screened at least once. 4