What are the implications of infrarenal aortic aneurysm (AAA) dilation with an eccentric mural thrombus?

From the Guidelines

Infrarenal aneurysms with eccentric mural thrombus should undergo repair if they measure 5.5 cm or larger to eliminate the risk of rupture, as recommended by the American College of Cardiology Foundation/American Heart Association task force on practice guidelines 1. The presence of an eccentric mural thrombus in an infrarenal aneurysm is particularly concerning due to the increased risk of distal embolization, which can lead to limb ischemia or visceral infarction. Key considerations in the management of these patients include:

• Monitoring aneurysm size with ultrasound or computed tomographic scans every 6 to 12 months to detect expansion, as recommended for aneurysms measuring 4.0 to 5.4 cm in diameter 1
• Controlling blood pressure to reduce the risk of rupture, with a target of less than 130/80 mmHg
• Starting patients on antiplatelet therapy and a statin to stabilize the plaque and reduce the risk of thrombotic events
• Ensuring smoking cessation to reduce the risk of aneurysm growth and rupture The natural history of infrarenal aneurysms involves weakening of the arterial wall with inflammatory processes and extracellular matrix degradation, leading to dilation and subsequent thrombus formation in areas of disturbed flow. Regular surveillance and prompt intervention are essential to prevent the complications associated with aneurysm rupture, embolization, and thrombosis. For aneurysms that meet the criteria for repair, surgical intervention, typically endovascular aneurysm repair (EVAR) or open surgical repair, is recommended to eliminate the risk of rupture and improve patient outcomes.

From the Research

Implications of Infrarenal Aneurysm Dilation with Eccentric Mural Thrombus

• Infrarenal aneurysm dilation with eccentric mural thrombus can lead to increased risk of proximal fixation failure after endovascular aneurysm repair (EVAR) 2
• The use of large-diameter endografts (34-36 mm) is associated with a higher risk of proximal fixation failure, type IA endoleak, and stent graft migration 2
• Aortic mural thrombus can be a source of embolism, and treatment with thrombolytic therapy or surgical exclusion of the thrombus can be effective 3, 4
• Infrarenal endovascular aneurysm repair has evolved with new developments and decision-making strategies, including the use of fenestrated and branched devices, which can extend the proximal and distal landing zones 5
• Abdominal aortic aneurysms, including those with infrarenal dilation, can be asymptomatic but have a high mortality rate if they rupture, emphasizing the importance of prophylactic repair during the asymptomatic period 6

Treatment and Outcomes

• Treatment of symptomatic aortic mural thrombus can involve anticoagulation, surgical exclusion of the thrombus, distal thrombectomy, or distal bypass 4
• Immediate exclusion of the thrombus can achieve the best results and prevent recurrences 4
• Endovascular techniques have become the primary modality for aneurysm repair, with approximately 60% of abdominal aortic aneurysms being confined to the infrarenal portion of the aorta and amenable to repair with off-the-shelf endovascular devices 6

Risk Factors and Considerations

• Large infrarenal necks (≥29 mm) requiring a 34- to 36-mm-diameter endograft are independently associated with an increased rate of proximal fixation failure 2
• The use of certain endografts, such as the Talent endograft, can also increase the risk of proximal fixation failure 2
• Vascular surgeons must select the best EVAR device based on each patient's abdominal aortic aneurysm anatomy, considering factors such as neck diameter and device diameter 5