What is the ideal landing zone for a Thoracic Endovascular Aortic Repair (TEVAR) procedure?

Ideal Landing Zone for Thoracic Endovascular Aortic Repair (TEVAR)

A sufficient proximal and distal landing zone of at least 2 cm is recommended for the safe deployment and durable fixation of TEVAR. 1

Landing Zone Requirements

Proximal Landing Zone

• Length: Minimum 2 cm of healthy aorta 1, 2
• Diameter: <40 mm 1
• Stent-graft sizing: Should exceed the reference aortic diameter at landing zones by 10-15% 1
• Quality: Should be free of significant disease (thrombus, calcification, ulceration)

Distal Landing Zone

• Length: Minimum 2 cm of healthy aorta 1
• Diameter: <40 mm 1
• Stent-graft sizing: Same 10-15% oversizing principle applies 1

Anatomical Considerations

Landing Zone Classification

The aorta is divided into landing zones (0-11) to standardize TEVAR planning:

• Zone 0: Ascending aorta to distal end of innominate artery origin
• Zone 1: Between innominate and left carotid artery
• Zone 2: Between left carotid and left subclavian artery
• Zone 3: First 2 cm distal to left subclavian artery
• Zone 4: From end of Zone 3 to mid-descending aorta (T6)
• Zone 5-11: Continuing distally 1

Optimal Zone Selection

Recent evidence suggests that more proximal landing zones may provide better outcomes:

• Zone 0 landing shows fewer bird-beak configurations, shorter and less angulated bird-beaks, and lower rates of type Ia endoleaks compared to Zones 1-2 3
• Zone 2 landing (with left subclavian artery revascularization) demonstrates lower rates of aortic reintervention and adverse events compared to Zone 3 in acute type B aortic dissections 4

Clinical Implications of Inadequate Landing Zones

Consequences of <2 cm Landing Zone

• Significantly higher rates of type IA endoleaks (22.2% vs 0%) 2
• Increased risk of graft migration (14.1% vs 2.3% when comparing Zones 1-2 vs Zone 0) 3
• Higher risk of retrograde dissection 2
• Increased need for reintervention 4

Special Considerations for Compromised Landing Zones

• In cases where the native aorta provides inadequate landing zones, landing in previously placed Dacron grafts (with >4-5 cm overlap) can provide excellent durability with very low endoleak rates 5
• For compromised distal landing zones, adjunctive techniques (visceral snorkel grafts, EndoAnchors) may help limit progressive degeneration 6

Technical Considerations During Deployment

• Blood pressure control: Invasive blood pressure monitoring and control (either pharmacologically or by rapid pacing) is essential during stent graft placement 1
• Avoid spinal cord ischemia: Vessels supplying the major spinal cord should not be covered in the elective setting (i.e., no overstenting of the left subclavian artery without revascularization) 1
• Preventive cerebrospinal fluid drainage: Should be considered in high-risk patients 1

Pitfalls to Avoid

1. Inadequate planning: Contrast-enhanced CT with 3 mm slices from supra-aortic branches to femoral arteries is essential for proper landing zone assessment 1
2. Insufficient landing zone length: Using <2 cm landing zones significantly increases adverse outcomes 2
3. Excessive oversizing: While 10-15% oversizing is recommended for aneurysms, almost no oversizing should be applied in type B dissections 1
4. Ignoring landing zone quality: Thrombus >50%, calcification >25%, or tortuosity index ≥1.1 can compromise landing zone integrity 6
5. Inadequate blood pressure control during deployment: Can lead to stent-graft displacement 1

In summary, meticulous attention to landing zone selection and preparation is critical for successful TEVAR outcomes, with a minimum of 2 cm of healthy aorta required for both proximal and distal landing zones, and appropriate oversizing based on the underlying pathology.