What is the technique for performing preventive stenting of visceral vessels and fenestrations?

Technique for Preventive Stenting of Visceral Vessels and Fenestrations

Preventive stenting of visceral vessels during fenestrated/branched endovascular aortic repair (FEVAR/BEVAR) involves pre-emptively placing bridging stents through fenestrations or branches to maintain perfusion before deploying the main aortic graft, with the goal of preventing malperfusion and ensuring target vessel patency. 1

Pre-Procedural Planning and Imaging

• Obtain high-quality CT angiography with contrast to create a detailed map showing which visceral vessels originate from the true versus false lumen in dissection cases, and to measure vessel diameters, angulations, and distances 2
• Measure aortic neck angulation, aneurysm diameter, and angulation of target visceral vessels from preoperative CT scans to identify anatomically challenging vessels that may require preventive stenting 3
• Plan stent sizing with 10-20% oversizing relative to the target vessel diameter, as smaller stent diameters are significant predictors of failure 3

Access and Equipment Setup

Standard FEVAR Approach

• Use an 18-22Fr contralateral introducer for 3-4 vessel FEVAR to accommodate parallel 6-7Fr guiding sheaths into each visceral vessel during main graft deployment 4
• The right femoral artery is the common site for surgical insertion of the 22-27F systems for stent graft delivery, leaving the left side for percutaneous access for angiography and intravascular ultrasound (IVUS) 1

Alternative Simplified Technique

• The SMART (Simplified Bare-Wire Target Vessel) technique uses only a 12-16Fr contralateral introducer, avoiding guiding sheaths into visceral arteries during main graft deployment, which reduces limb ischemia risk 4

Sequential Catheterization and Stenting Technique

Fenestration Catheterization

• Sequentially catheterize each fenestration using a steerable sheath for directional control 4
• Use subtraction angiography to verify wire position in the true lumen before any stent deployment to avoid catastrophic false lumen stenting 2
• Maintain a Rosen wire in each fenestration after catheterization, with a single sheath parked in the final target vessel while releasing the fenestrated graft 4

Stent Selection and Deployment

• For precise deployment just cephalad to critical branch arteries (superior mesenteric artery or renal arteries), use balloon-expandable Palmaz stents to avoid compromising flow to distal branches 1
• For more flexible deployment in tortuous anatomy, 14mm diameter self-expanding Wallstents are an alternative 1
• Deploy bridging stents with sufficient length of coverage into the target vessel—shorter stent lengths are significant predictors of failure and should be avoided 3
• Ensure at least 3-5cm of stent coverage both proximal and distal to any fenestration or branch junction 1

Timing of Stent Deployment

• In dissection cases where visceral vessels are perfused from the false lumen, stent vessels at risk from the true lumen BEFORE or concurrent with proximal entry tear coverage to maintain perfusion 2
• In standard FEVAR without dissection, stents can be deployed sequentially through fenestrations after main graft positioning but before final deployment 4

Critical Technical Considerations

Avoiding Malperfusion

• Recognize that inadvertent stent graft placement from true to false lumen causes acute visceral malperfusion requiring urgent revision with fenestration and distal extension 2
• Perform completion angiography after each stent deployment to confirm all visceral vessels are still perfusing before proceeding 2
• In dynamic obstruction patterns (where the dissection flap moves), perform percutaneous balloon fenestration with or without stents in the aortic true lumen, rather than just branch vessel stenting 1

Stent Positioning Precision

• Deploy stents to buttress the dissection flap in a stable position remote from branch artery origins when treating dissection 1
• Avoid stent placement across the superior mesenteric and renal artery origins when possible to preserve collateral flow 1
• Use a balloon incorporated in the delivery system to achieve further apposition of stent struts to the vessel wall after deployment 1

Hemodynamic Management During Deployment

• Perform the procedure under general anesthesia 1
• Lower blood pressure to 50-60 mmHg using sodium nitroprusside during stent expansion to reduce wall stress 1
• Recognize that aortic pressure increases instantaneously during stent expansion because antegrade flow is blocked, then becomes free after complete stent graft delivery 1

Special Situations

Inner Branch Technique

• For vessels unsuitable for fenestrations or directional side branches, inner branches (as used in arch branched devices) provide an alternative option 5
• Stent grafts combining fenestrations with inner branches show better catheterization times (<1 minute) compared to inner branch-only grafts (which may take >3 minutes) 5
• Inner branches achieve 91.9% target vessel patency at 1 year but require careful patient selection 5

Chronic Dissection with Fibrosed Membrane

• In chronic dissection where fenestration of a fibrosed dissecting membrane may result in collapse of the connection between true and false lumen, deploy a stent to keep the fenestration open 1

Creating Reentry Fenestrations

• When creating a reentry tear for a dead-end false lumen, avoid making the fenestration too large, as this keeps the false lumen pressurized long-term and promotes aneurysm formation and eventual rupture 2
• The more sensible method is creating a large reentry tear where needed, followed by stent placement between the tear and the compromised branch 1

Post-Deployment Verification

• Perform immediate completion angiography to confirm all visceral vessels are perfusing and no endoleaks are present at fenestration sites 2
• Obtain immediate post-procedure CTA before hospital discharge to confirm target vessel patency and aneurysm exclusion 2
• Duplex ultrasound is useful for surveillance of target branch vessels after FEVAR, though complex EVAR involving stenting of ≥1 renovisceral vessels benefits from routine cross-sectional imaging for surveillance of fenestration sites and branch junctions 1

Common Pitfalls and How to Avoid Them

Stent Undersizing and Insufficient Length

• Smaller stent diameter and shorter length are the most significant predictors of visceral stent failure, particularly in renal arteries 3
• Plan for adequate oversizing (10-20%) and ensure sufficient length extending well into the target vessel 3

Failure to Recognize Perfusion Patterns

• Failure to recognize which lumen supplies visceral vessels in dissection leads to inappropriate intervention strategy 2
• Always map perfusion patterns pre-procedurally and verify with selective angiography 2

Premature Main Graft Deployment

• Deploying the main fenestrated graft before securing all target vessels with wires risks losing access to fenestrations 4
• Maintain wire access in all fenestrations until the main graft is fully deployed and positioned 4

Surveillance Protocol

• Perform follow-up imaging at 1 month, 6 months, 12 months, then annually to monitor for favorable remodeling, stent patency, and endoleaks 2
• Renal stents have the highest failure rate (86% of reinterventions) and require particularly close surveillance 3
• Most reinterventions occur within the first year (5.4% at 1 year), with decreasing frequency thereafter 3