What is the management of stent migration after Endovascular Aortic Repair (EVAR)?

Management of Stent Migration After EVAR

When stent migration is detected after EVAR, the primary management is deployment of an additional stent graft (either a proximal extension cuff or relining stent) to restore adequate seal and prevent type I or type III endoleak, which are the life-threatening consequences of migration that can lead to aneurysm rupture. 1, 2

Detection and Surveillance

Imaging for Detection:

• CT angiography is the gold standard for detecting stent migration, as duplex ultrasound is limited in its ability to identify this complication despite being excellent for endoleak detection 3
• MRI with accompanying plain abdominal radiograph is an alternative that can detect migration while reducing radiation exposure 3
• Migration is defined as ≥5 mm displacement of the stent graft from its original position 1, 2, 4

Surveillance Protocol:

• Baseline CT at 1 month post-EVAR is critical for establishing the reference position 5
• If initial imaging is normal, transition to duplex ultrasound at 12 months and annually, with cross-sectional imaging (CT or MRI) every 5 years 3, 5
• Any abnormal findings on duplex ultrasound mandate immediate cross-sectional imaging to evaluate for migration 5

Clinical Significance and Risk Assessment

Migration occurs in 3-4% of patients by 4 years postoperatively and is a significant cause of late endograft failure 3

High-Risk Anatomic Features Requiring Intensified Surveillance:

• Large aneurysm diameter (>60 mm) 1
• Dilated or aneurysmal common iliac artery (>18 mm diameter) 1
• Short proximal neck length (<15 mm) 1, 4
• Inadequate length of fixation (<70% engagement) 1
• Low degree of iliac limb oversizing (<10-20%) 1
• Mural thrombus and calcification covering >90% of proximal neck circumference 3
• Reverse-tapered neck anatomy 4

Endovascular Reintervention

Primary Management Strategy:

• Deployment of additional stent graft (proximal extension cuff or relining stent) is the most common and effective reintervention 1, 2
• This approach successfully restores seal and prevents progression to type I or type III endoleak 1
• All patients in contemporary series who underwent additional stent graft placement had successful outcomes without perioperative deaths or complications 1

Indications for Urgent Intervention:

• Type I endoleak associated with migration (occurs in approximately 33% of migration cases) 4
• Type III endoleak from limb disconnection 1
• Aneurysm sac enlargement ≥10 mm 5
• Complete migration with impending or actual rupture 1, 2

Conversion to Open Repair

Late conversion to open surgical repair is reserved for:

• Complete stent graft migration that cannot be salvaged endovascularly 2
• Aneurysm rupture secondary to migration 2
• Failed endovascular reintervention 3

In one series, 8 of 26 patients (31%) with migration required late conversion to open repair, with 2 cases involving aneurysm rupture 2

Prevention Strategies

Technical Considerations:

• Deploy the endograft immediately below the renal arteries to maximize overlap length 4
• Ensure adequate proximal neck length (>15 mm preferred) 1, 4
• Achieve appropriate oversizing (10-20% for iliac limbs) 1
• Consider balloon-expandable stents rather than self-expanding stents in high-risk anatomy, as they demonstrate no migration in some series 6

Common Pitfalls

• Relying solely on duplex ultrasound for surveillance will miss migration, as this modality cannot adequately characterize stent position 3
• Delaying intervention once migration is detected increases risk of type I endoleak and rupture 1, 2
• Underestimating the importance of proximal neck anatomy during initial device selection leads to higher migration rates 1, 4
• Proximal neck dilatation over time is a major cause of late migration, occurring even with initially adequate anatomy 2, 4