What is the step-by-step plan for deploying a flow diverting stent across a posterior communicating artery (Pcomm) aneurysm?

Step-by-Step Plan for Flow Diverting Stent Deployment Across a Posterior Communicating Artery Aneurysm

Flow diverting stents are an effective and safe treatment option for posterior communicating artery (PComm) aneurysms, with complete occlusion rates of 73.7% at 12 months based on recent clinical trials. 1

Pre-Procedure Planning

1. Imaging and Assessment

   • Obtain high-quality vascular imaging (CT angiography, MR angiography, or DSA)
   • Evaluate aneurysm characteristics:
     • Size and neck width
     • Relationship to PComm origin
     • Presence of fetal PComm variant (affects occlusion rates) 2
   • Assess parent vessel diameter and curvature
   • Determine if antiplatelet therapy can be safely administered

2. Patient Preparation

   • Initiate dual antiplatelet therapy (DAPT) at least 5-7 days before procedure
   • Verify platelet function testing to ensure adequate response
   • Obtain informed consent discussing risks including:
     • PComm occlusion (occurs in ~54.5% of cases but typically clinically silent) 1
     • Thromboembolic complications (5.6% risk of in-stent thrombosis) 3

Procedural Steps

1. Anesthesia and Access

   • Perform procedure under general anesthesia
   • Lower blood pressure to 50-60 mmHg during stent deployment 4
   • Obtain femoral arterial access using standard Seldinger technique

2. Catheterization and Angiography

   • Place guiding catheter in internal carotid artery
   • Perform baseline angiography to:
     • Confirm aneurysm dimensions
     • Measure parent vessel diameter
     • Document PComm patency and size
     • Assess collateral circulation

3. Device Selection

   • Choose appropriate flow diverter size:
     • Diameter: Match to parent vessel (typically 3-5mm for ICA)
     • Length: Cover 3-5cm proximal and distal to aneurysm neck 4
   • Select delivery microcatheter compatible with chosen flow diverter

4. Microcatheter Navigation

   • Navigate microcatheter past the aneurysm
   • Position distal tip at least 2-3cm beyond aneurysm neck
   • Confirm position with roadmap imaging
   • Maintain stable position during device preparation

5. Flow Diverter Deployment

   • Load flow diverter into microcatheter
   • Begin deployment by:
     • Retracting microcatheter while maintaining stable wire position
     • Monitoring for device opening and wall apposition
   • Position proximal end to extend 5-10mm proximal to aneurysm neck
   • Ensure complete coverage of aneurysm neck
   • Avoid covering critical perforators when possible

6. Device Optimization

   • Perform angioplasty if needed to ensure full wall apposition:
     • Use compliant balloon sized to parent vessel
     • Apply gentle pressure to optimize stent expansion
   • Verify flow diverter position and wall apposition with angiography
   • Confirm adequate inflow reduction to aneurysm

7. Final Assessment

   • Perform final angiography to:
     • Document flow diverter position
     • Assess aneurysm filling characteristics
     • Evaluate PComm patency
     • Confirm no parent vessel stenosis or thrombosis
   • Document baseline appearance for comparison during follow-up

Post-Procedure Management

1. Immediate Care

   • Monitor neurological status closely
   • Maintain blood pressure control
   • Continue dual antiplatelet therapy

2. Follow-up Protocol

   • MRI at 3 months to assess for aneurysm thrombosis 3
   • Angiographic follow-up at 6 months 3
   • Final angiographic assessment at 12 months 1
   • Continue DAPT for at least 3-6 months, then consider transitioning to single antiplatelet therapy

Technical Considerations and Pitfalls

1. Managing the PComm Artery

   • Be aware that PComm occlusion occurs in approximately 54.5% of cases after flow diverter placement but is typically clinically silent 1
   • For fetal PComm variants, consider alternative treatments as flow diversion has lower efficacy (43.7% vs 81.8% occlusion rate) 2

2. Avoiding Complications

   • Prevent foreshortening by maintaining forward pressure during deployment
   • Avoid excessive manipulation to prevent vessel injury
   • Be prepared for rescue strategies if thrombosis occurs:
     • Have glycoprotein IIb/IIIa inhibitors available
     • Consider balloon angioplasty for in-stent stenosis

3. Special Considerations

   • For wide-necked aneurysms, ensure adequate coverage of entire neck
   • For large/giant aneurysms, consider adjunctive coiling to accelerate thrombosis
   • For ruptured aneurysms, carefully weigh risks of antiplatelet therapy against benefits of flow diversion 4

By following this systematic approach, flow diverting stents can be safely and effectively deployed across PComm aneurysms with high technical success rates and favorable long-term outcomes.