What are the signs that endovascular aortic repair (EVAR) has failed?

Signs of Endovascular Aortic Repair (EVAR) Failure

EVAR failure manifests through specific imaging findings and clinical presentations that demand immediate recognition: endoleaks with sac enlargement ≥10 mm, stent graft migration, limb occlusion, and pelvic/visceral ischemia are the primary indicators requiring urgent intervention. 1, 2, 3

Imaging-Based Signs of Failure

Endoleaks (Most Common Complication)

• Type I and Type III endoleaks are high-pressure leaks that most commonly lead to rupture and mandate immediate correction with endovascular reintervention 4, 2
• Aneurysm sac enlargement ≥10 mm is an absolute indication for urgent intervention regardless of endoleak type 1
• Type II endoleaks occur in approximately 25% of patients but may seal spontaneously in 50% of cases; intervention is only needed if associated with sac growth 4
• CT angiography is the gold standard for detecting these complications, as duplex ultrasound cannot adequately characterize stent position or migration despite being excellent for endoleak detection 1, 5

Stent Graft Migration

• Migration occurs in 3-4% of patients by 4 years postoperatively and represents a significant cause of late endograft failure 1
• Baseline CT at 1 month post-EVAR is critical for establishing reference position to detect subsequent migration 1, 5
• Mural thrombus and calcification covering >90% of proximal neck circumference is a high-risk anatomic feature requiring intensified surveillance 1

Device-Related Failures

• Stent graft kinking or occlusion indicates structural failure requiring reintervention 6
• Improper endograft placement detected on immediate post-operative imaging necessitates early correction 6

Clinical Presentations of EVAR Failure

Lower Extremity Ischemia (9% Incidence)

• Limb occlusion occurs in 71.4% of ischemic complications, presenting as severe acute arterial ischemia, rest pain, intermittent claudication, or decreased femoral pulse 3
• Acute presentation with severe ischemia requires immediate thrombectomy and stent placement or femorofemoral bypass 3
• Embolization (14.7%) and common femoral artery thrombosis (14.7%) present acutely and require urgent embolectomy 3

Pelvic Ischemia (High Morbidity/Mortality)

• Colonic ischemia presents immediately postoperatively or within the first week with abdominal pain; requires urgent colectomy if severe, with perioperative mortality up to 50% in cases requiring urgent surgery 3
• Spinal cord ischemia manifests immediately after surgery as paraplegia and is often irreversible 3
• Buttock ischemia may progress to gluteal compartment syndrome requiring fasciotomy 3

Systemic Complications

• Postimplantation syndrome with fever and systemic inflammatory response indicates device-related complications 6
• Endograft infection presents with fever, elevated inflammatory markers, and perigraft fluid on imaging 6

Surveillance Protocol to Detect Failure

Initial Surveillance (First Year)

• CT angiography at 1 month is mandatory to establish baseline anatomy and detect early complications including migration, endoleaks, and improper positioning 1, 5, 4
• Follow-up imaging at 12 months using CT or MRI combined with duplex ultrasound 5

Long-Term Surveillance

• Annual duplex ultrasound if no abnormalities documented in first year 5
• Cross-sectional imaging (CT or MRI) every 5 years after initial stable period to reduce radiation exposure 1, 5
• Any abnormal duplex ultrasound findings mandate immediate cross-sectional imaging to evaluate for migration or endoleak 1

Critical Pitfalls to Avoid

• Never rely solely on duplex ultrasound for surveillance, as this modality cannot adequately characterize stent position and will miss migration 1
• Do not skip the 1-month CT scan, as it is critical for establishing baseline post-intervention anatomy and detecting early complications 5
• Recognize that EVAR requires lifelong imaging surveillance due to higher rates of complications requiring reintervention compared to open repair; patients unable to comply with follow-up are poor EVAR candidates 4, 7
• Annual rupture rate of 1% and conversion to open repair rate of 2% occur with EVAR, with conversion carrying 24% perioperative mortality 8

When to Convert to Open Repair

• Failed endovascular reintervention for endoleaks or migration 1
• Persistent high-pressure endoleaks (Type I or III) not amenable to endovascular correction 2
• Endograft infection requires explantation and open repair 6
• Bleeding complications or pseudoaneurysms of access vessels refractory to endovascular management 6