What are the steps for modifying an endograft for a patient with a patent left subclavian artery undergoing a Fenestrated Thoracic Endovascular Aortic Repair (TEVAR) procedure?

Physician-Modified Endograft (PMEG) Step-by-Step Guide for Fenestrated TEVAR with Patent Left Subclavian Artery

For patients requiring zone 2 TEVAR with left subclavian artery (LSA) preservation, physician-modified endografts with fenestration or scalloping represent a feasible off-label technique with 94% technical success and excellent midterm patency when commercial fenestrated devices are unavailable. 1

Preoperative Planning and Patient Selection

Critical Imaging Requirements

• Obtain high-quality CTA with thin-section acquisition (≤1.5mm) covering chest, abdomen, and pelvis to measure landing zones, assess vessel alignment, and evaluate iliofemoral access 2
• Measure precise distances between LSA ostium and intended proximal landing zone, LSA diameter at ostium, and aortic diameter at planned seal zones 2
• Calculate aortic tortuosity index at the proximal landing zone, as high tortuosity significantly increases risk of type III endoleak, stroke, and mortality 2
• Assess for bird-beak configuration risk in highly angulated aortic arch anatomy, which predicts type Ia endoleak 2

Determine Need for LSA Revascularization

• Verify patency of contralateral right subclavian and vertebral arteries using CTA, MRA, or invasive angiography 2
• Confirm vertebral arteries communicate at the basilar artery via transcranial Doppler or angiography 2
• Mandatory LSA preservation if: patient has patent left internal mammary artery to left anterior descending coronary bypass graft, relies on LSA for dialysis access, or has dominant left vertebral artery 2, 3

Assess Spinal Cord Ischemia Risk

• Place prophylactic lumbar drain if: extensive aortic coverage planned (>15cm or left subclavian to celiac), prior abdominal aortic repair (10-12% paraplegia risk vs 2% without), or LSA coverage without revascularization 2, 4
• Target cerebrospinal fluid pressure <10 mmHg while optimizing mean arterial pressure 4

Endograft Modification Techniques

Option 1: Pre-deployment Fenestration (Most Common)

Steps:

1. Select appropriately sized thoracic endograft (typically Gore TAG, Medtronic Valiant, or Cook TX2) based on proximal landing zone diameter with 10-15% oversizing 1
2. On back table in sterile field, mark LSA ostium location on graft fabric using preoperative CTA measurements 1
3. Create fenestration using one of three methods:
   • Cutting technique: Use electrocautery or sharp dissection to create 8-10mm circular opening in graft fabric 1
   • Laser technique (if available): Provides more precise fabric edges 5
   • Scallop technique: Create semicircular cutout at graft edge if LSA is at proximal margin 1
4. Reinforce fenestration edges with running 5-0 or 6-0 polypropylene suture to prevent fabric tear propagation 1
5. Repack modified graft into delivery system under sterile conditions 1

Option 2: In Situ Fenestration (Alternative Approach)

Steps:

1. Deploy standard thoracic endograft covering LSA ostium 6, 5
2. Via retrograde left brachial artery access (6-7Fr sheath), advance 0.035" guidewire through graft fabric at LSA ostium location using fluoroscopic guidance 6
3. Advance laser catheter (if available) or serial cutting balloons (4mm, 6mm, 8mm) over wire to create fenestration 6, 5
4. Proceed immediately to stent deployment (see below) 5

Caveat: In situ technique has theoretical concern for long-term fabric tear propagation, though midterm data shows 100% patency 5

Intraoperative Deployment Protocol

Access and Setup

• Primary access: Percutaneous or open femoral access for main endograft delivery (requires 20-25Fr sheath compatibility) 2
• Secondary access: Left brachial artery cutdown or percutaneous access (6-7Fr) for LSA catheterization 1, 5
• Verify adequate iliofemoral vessel diameter (>7mm) and assess calcification/tortuosity on preoperative CTA 2
• If iliofemoral access inadequate, use iliac conduit or direct aortic/iliac exposure 2

Deployment Sequence

1. Advance main endograft to proximal landing zone via femoral access under fluoroscopic guidance 1
2. Catheterize LSA from brachial access: advance 0.035" hydrophilic guidewire and 5Fr catheter through fenestration into LSA 1, 5
3. Deploy thoracic endograft at intended landing zone, ensuring fenestration aligns with LSA ostium 1
4. Immediately deploy covered stent (8-10mm balloon-expandable covered stent, typically Atrium Advanta V12 or Gore Viabahn) from brachial access through fenestration into LSA 1, 5
5. Extend covered stent proximally to traverse endograft fabric and distally 1-2cm into LSA 5
6. Perform kissing balloon technique: Simultaneously inflate balloon in covered stent and molding balloon in main endograft to ensure apposition 7
7. Completion angiography to confirm LSA patency, exclude endoleak, and verify aneurysm/dissection exclusion 1, 5

Technical Success Criteria

• LSA remains patent with brisk antegrade flow 1
• No type I or III endoleak at fenestration site 1
• Adequate proximal and distal seal zones (≥2cm) 2
• Equal bilateral arm blood pressures 6

Critical Intraoperative Pitfalls

Fenestration Misalignment

• Problem: Fenestration does not align with LSA ostium after deployment 1
• Prevention: Use precise measurements from CTA, deploy graft slowly under fluoroscopy, and have brachial wire through fenestration before full deployment 1
• Management: If misalignment occurs, consider in situ fenestration at correct location or accept LSA coverage if revascularization not mandatory 1

Covered Stent Complications

• Stent migration: Size covered stent 1-2mm larger than LSA diameter at landing zone to prevent migration 7
• Type II endoleak from LSA: Occurs in ~4% of cases; treat with coil embolization if persistent 5
• Stent occlusion: Rare (0-6% in series); ensure adequate stent diameter and avoid kinking 1, 7

Postoperative Management

Immediate Monitoring

• Monitor bilateral arm blood pressures and pulses to detect LSA flow compromise 3
• Maintain mean arterial pressure >80-90 mmHg for first 48-72 hours to optimize spinal cord perfusion if lumbar drain placed 4
• Continue CSF drainage with target pressure <10 mmHg for 48-72 hours in high-risk patients 4

Surveillance Protocol

• CTA at 1 month: Assess LSA covered stent patency, detect endoleak (type I, II, or III), evaluate for stent migration or fabric tear 3
• CTA at 12 months, then annually: Monitor for late complications including endoleak (11% at 30 days, 6% at 1 year), stent fracture, retrograde type A dissection, and progressive aortic dilation 3
• Reintervention rate: Expect 4-7% reintervention rate, primarily for type II endoleaks from LSA requiring coil embolization 1, 5

Delayed Complications

• New left arm symptoms (claudication, weakness, coolness) warrant urgent CTA to evaluate covered stent patency 3
• Delayed paraplegia: If occurs despite patent LSA fenestration, emergently place lumbar drain if not already present and optimize hemodynamics 3
• Vertebrobasilar insufficiency: Rare with patent LSA fenestration, but if occurs consider angiography to assess vertebral artery flow 2

Expected Outcomes

Technical Success and Patency

• Technical success: 94-100% in published series 1, 5, 7
• LSA covered stent primary patency: 93-100% at 2 years 1, 5, 7
• Mean follow-up data available to 26-37 months shows durable results 1, 5, 7

Perioperative Complications

• Spinal cord ischemia: 2% (significantly lower than 10-12% with LSA coverage and prior abdominal repair) 2, 1
• Stroke: 6% (minor strokes with full recovery) 1
• Perioperative mortality: 4-7% (primarily in ruptured cases) 1, 5
• Type II endoleak requiring treatment: 4% 1, 5

Long-term Considerations

• No fenestration-related type I or III endoleaks reported in midterm follow-up 1, 5
• No stent fractures, migrations, or conversions to open repair in published series 1
• All LSA stents remain clinically and radiologically patent at available follow-up 1