Is a partially visualized aortobiiliac (aortobifemoral iliac) stent graft indicative of a patent graft to an infrarenal abdominal aortic aneurysm?

Interpretation of Partially Visualized Aortobiiliac Stent Graft

A partially visualized aortobiiliac stent graft on imaging does not necessarily indicate patency of the graft to an infrarenal abdominal aortic aneurysm, and additional imaging is required to definitively determine graft status. 1

Understanding Stent Graft Visualization and Patency

Stent grafts are commonly used for endovascular repair (EVAR) of infrarenal abdominal aortic aneurysms (AAAs). When a stent graft appears "partially visualized" on imaging, this finding alone is insufficient to determine:

1. Complete patency of the graft
2. Presence or absence of endoleaks
3. Stability of the aneurysm sac
4. Proper positioning of the graft components

Why Further Evaluation Is Necessary

• Incomplete visualization: Partial visualization may miss critical areas where complications could be present
• Potential complications: Endoleaks, graft migration, kinking, or thrombosis may not be apparent on limited views 1
• Surveillance requirements: Guidelines mandate comprehensive imaging for proper follow-up 1

Recommended Imaging Approach

The American College of Cardiology Foundation/American Heart Association (ACCF/AHA) guidelines recommend:

1. Complete CT angiography (CTA) as the gold standard for post-EVAR surveillance 1

   • Provides comprehensive assessment of:
     • Graft position and integrity
     • Presence of endoleaks
     • Aneurysm sac size (expansion or shrinkage)
     • Patency of all graft components

2. Alternative imaging options if CTA is contraindicated:

   • MR angiography (MRA) for patients with renal insufficiency
   • Duplex ultrasound with arterial and venous phase imaging (less sensitive for some endoleaks)

Clinical Implications and Management

For Asymptomatic Patients with Partial Visualization:

1. Obtain complete imaging to fully assess the stent graft 1

   • CTA with arterial and delayed phases is preferred
   • Evaluate all components of the bifurcated graft

2. Look specifically for:

   • Type I endoleaks (inadequate seal at proximal or distal attachment sites)
   • Type II endoleaks (retrograde flow from branch vessels)
   • Type III endoleaks (graft defects or component separation)
   • Graft limb thrombosis or stenosis
   • Aneurysm sac enlargement

For Symptomatic Patients:

If a patient with a partially visualized stent graft presents with:

• Abdominal/back pain
• Hypotension
• Pulsatile mass

Immediate complete CTA is mandatory to rule out:

• Rupture
• Endoleak with sac expansion
• Graft migration or failure 1

Long-term Surveillance Protocol

The European Society of Cardiology (ESC) and ACCF/AHA recommend:

• CTA at 1 month post-procedure
• CTA at 6 months
• CTA at 12 months
• Annual imaging thereafter if stable 1

If any abnormality is detected on surveillance imaging, more frequent follow-up may be required.

Common Pitfalls in Stent Graft Assessment

1. Assuming patency from partial visualization: Complete assessment is required
2. Missing delayed endoleaks: Some endoleaks only appear on delayed imaging phases
3. Overlooking graft migration: Subtle changes in position can lead to future complications
4. Neglecting sac measurements: Stable or shrinking sac size is the best indicator of successful aneurysm exclusion 1

Conclusion

When an aortobiiliac stent graft is only partially visualized on imaging, complete assessment with dedicated CTA is necessary to determine patency, position, and effectiveness in treating the infrarenal AAA. Partial visualization alone is insufficient to make clinical decisions about the status of the repair.