Types of Carotid Stents
Primary Classification System
Carotid stents are fundamentally classified into three main categories: single-layer (1st generation), dual-layer/'mesh' (2nd generation), and by cell configuration (open-cell vs. closed-cell), with dual-layer/'mesh' stents now recommended as the primary choice due to their superior embolic protection. 1
Visual Classification Table
| Stent Type | Design Features | Key Advantages | Key Disadvantages | Best Clinical Application |
|---|---|---|---|---|
| SINGLE-LAYER STENTS | ||||
| Open-Cell (e.g., Acculink, Precise Pro, Protégé) | Free-cell area ≥5 mm², high flexibility | • Superior conformability to tortuous anatomy [2] • Excellent adaptability to vessel curves [3] • Low bending forces (0.063-0.890 N) [3] |
• Allows plaque prolapse through struts [4] • Permits particle penetration up to 6 mm [3] • Continued post-procedural embolism [4] |
Tortuous carotid anatomy with low embolic risk [5] |
| Closed-Cell (e.g., XACT, Wallstent) | Free-cell area <5 mm², rigid structure | • Better scaffolding against plaque prolapse [3] • Reduced particle penetration [3] • Lower periprocedural stroke in primary lesions (2.2% vs 3.5%) [2] |
• Poor flexibility (bending forces up to 0.890 N) [3] • Limited adaptability to tortuous vessels [6] • Higher kinking risk [1] |
Straight anatomy with high embolic risk plaques [5] |
| Braided Design | Woven nitinol construction | • Shape-memory properties [1] | • Independent risk factor for restenosis (OR=2.71, P<0.001) [4] • Higher recurrent restenosis (OR=3.11) [4] |
Avoid when possible due to restenosis risk [4] |
| DUAL-LAYER/'MESH' STENTS (2nd Generation) | ||||
| Micronet-Covered | Dual-layer with fine mesh overlay | • 50% reduction in cerebral embolization [4] • 80% reduction in total embolic load [4] • 70% reduction in permanent infarcts [4] • Eliminates post-procedural embolism [4] |
• Requires 3 months DAPT vs 4-6 weeks [4] • Design variations affect outcomes (no class effect) [4] |
Primary recommendation for all CAS procedures [1] |
| Hybrid Design (e.g., Cristallo Ideale) | Open-cell flexibility + closed-cell scaffolding | • Combines flexibility with particle resistance [3] • Lowest bending force (0.063 N) [3] • Resists penetration except 1.5 mm particles [3] |
• Limited long-term outcome data [3] | Complex anatomy requiring both flexibility and embolic protection [3] |
| SPECIALIZED DESIGNS | ||||
| Tapered Stents | Variable diameter along length | • Accommodates CCA-ICA diameter mismatch [5] | • Limited availability [5] | Significant vessel size discrepancy [5] |
| Cobalt-Chromium (Elgiloy) | Non-nitinol metal alloy | • Handles diameter mismatch [5] • High radial force [5] |
• Less flexible than nitinol [5] | Vessel diameter mismatch situations [5] |
Cell Configuration Comparison
Open-Cell Stents
- Cell size: 15.10 mm² (Acculink) to variable 3
- Flexibility: Torsion forces as low as 0.032 N 3
- Particle penetration: Allows spheres up to 6 mm diameter 3
- Clinical outcome: 3.5% periprocedural stroke/death in primary lesions 2
- Indication: Tortuous anatomy where conformability is critical 5, 6
Closed-Cell Stents
- Cell size: 1.36 mm² (Wallstent) to <5 mm² 3
- Flexibility: Torsion forces up to 1.071 N 3
- Particle penetration: Resists penetration of particles >4 mm 3
- Clinical outcome: 2.2% periprocedural stroke/death in primary lesions 2
- Indication: High embolic risk plaques in straight anatomy 5, 2
Generation-Based Performance Metrics
1st Generation (Single-Layer) Stents
- Embolic protection: Inadequate plaque sequestration 4
- Post-procedural embolism: Continues after stent deployment 4
- Restenosis mechanism: Intra-stent atherosclerosis progression 4
- DAPT duration: 4-6 weeks 4
- Acceptance criteria: <50% residual stenosis 4
2nd Generation (Dual-Layer/'Mesh') Stents
- Embolic protection: 50-80% reduction in embolization 4, 1
- Post-procedural embolism: Completely eliminated 4
- Restenosis: Design-dependent (no class effect) 4
- DAPT duration: Up to 3 months 4
- Clinical outcomes: May not differ from CEA or be superior 4
Material-Based Classification
Nitinol Stents
- Properties: Shape-memory, thermal responsiveness 1
- Radial force: 9.06-24.09 N depending on design 3
- Restenosis risk: Higher with braided designs (OR=2.71) 4
- Application: Standard choice for most anatomies 5
Cobalt-Chromium (Elgiloy) Stents
- Properties: High radial strength, no shape-memory 5
- Application: Diameter mismatch scenarios 5
- Flexibility: Lower than nitinol 5
Critical Selection Factors
Anatomical Considerations
- Tortuous vessels: Open-cell or hybrid designs mandatory 5, 6
- Straight vessels: Closed-cell acceptable 5
- Diameter mismatch: Tapered or cobalt-chromium stents 5
- Calcified lesions: Nitinol stents preferred 5
Plaque Characteristics
- High embolic risk (hypoechoic, long plaques): Dual-layer/'mesh' stents reduce embolization by 50% 4
- Pre-existing cerebral lesions: Micronet-covered stents show smaller filter load 4
- Calcified plaques: Nitinol stents handle deployment forces better 5
Lesion Type
- Primary atherosclerotic lesions: Closed-cell stents show 1.59× lower stroke risk vs open-cell 2
- Restenotic lesions: Open-cell may perform better (1.2% vs 4.0% events, though not statistically significant) 2
Post-Deployment Surveillance Parameters
Velocity Thresholds (Stented Arteries Only)
- Significant restenosis (≥70%): Peak-systolic velocity ≥3 m/s AND end-diastolic velocity ≥1.4 m/s 4, 1
- Critical error: Never use non-stented artery criteria for stented vessels—causes significant overestimation 4, 1
Design-Specific Monitoring
- Open-cell stents: Higher baseline velocities due to conformability 4
- Closed-cell stents: Lower baseline velocities due to bending stiffness 4
- Braided designs: Increased surveillance frequency due to 2.71× restenosis risk 4
Common Pitfalls in Stent Selection
- Using single-layer stents in high embolic risk lesions: Fails to sequestrate plaque, allows continued embolization 4
- Selecting closed-cell stents for tortuous anatomy: Increases kinking and deployment complications 1, 5
- Assuming all dual-layer stents perform equally: No class effect exists; design variations significantly affect outcomes 4
- Avoiding braided designs: Independent restenosis risk factor (OR=2.71) 4
- Accepting >50% residual stenosis: Principal risk factor for subsequent restenosis 7