What is the relationship between stent length and the risk of in-stent restenosis (ISR)?

Relationship Between Stent Length and In-Stent Restenosis (ISR)

Longer stent length is an independent risk factor for in-stent restenosis, with stents ≥31.5 mm having significantly higher rates of restenosis and adverse cardiac events compared to shorter stents. 1

Mechanism and Evidence

Stent length affects restenosis risk through several mechanisms:

• Intimal Hyperplasia: Longer stents expose more vessel wall to injury, promoting greater neointimal proliferation 2
• Mechanical Factors: Longer stents may experience:
  • More areas of suboptimal expansion
  • Higher rates of stent edge dissection
  • Greater likelihood of geographic miss at stent margins

Key Evidence on Stent Length and ISR

The ACC/AHA/SCAI guidelines identify stent length as one of the key factors associated with the propensity to develop stent restenosis 2. Multiple studies have quantified this relationship:

• For bare-metal stents (BMS), each 10 mm of stented lesion length increases percent diameter stenosis by 7.7% 3
• Each 10 mm of excess stent length beyond the lesion independently increases percent diameter stenosis by 4.0% 3
• Stent lengths ≥31.5 mm are associated with significantly higher rates of stent thrombosis (4.0% vs 0.7%), death (5.2% vs 3.0%), and myocardial infarction (2.4% vs 0.7%) at 3 years compared to shorter stents 1

Clinical Implications

Stent Selection Principles

1. Match stent length to lesion length:

   • Avoid excessive stent length beyond the lesion boundaries 3
   • Longer stent-to-lesion length strategies should only be used when shorter stents might result in incomplete lesion coverage 4

2. Consider drug-eluting stents (DES) for longer lesions:

   • DES significantly reduce the restenosis penalty associated with longer stent lengths compared to BMS 5, 4
   • For stents >23 mm, DES are associated with lower hazard of target vessel revascularization (HR 0.34) and nonfatal MI or death (HR 0.60) compared to BMS 5

3. Minimize number of stents and avoid overlapping stents:

   • Multiple and overlapping stents independently increase restenosis risk 6
   • When possible, use a single longer stent rather than multiple overlapping shorter stents

Intravascular Imaging Guidance

For longer stents, intravascular imaging (IVUS or OCT) is particularly valuable to:

• Ensure complete lesion coverage from normal distal to normal proximal segments 2
• Avoid stenting into reference segments with plaque burden >50% 2
• Confirm adequate stent expansion, which is critical for preventing restenosis 2
• Detect and address edge dissections, which are more common with longer stents 2

Special Considerations

Femoropopliteal Stenting

In peripheral artery disease, the relationship between stent length and restenosis follows similar patterns:

• Longer stents in the superficial femoral artery have higher restenosis rates 2
• However, with newer-generation nitinol stents (up to 20 cm), endovascular therapy has become viable even for longer and more complex lesions 2
• In-stent restenosis remains the major drawback of stent implantation in this territory 2

Practical Approach to Minimize ISR Risk Related to Stent Length

1. Accurate lesion assessment:

   • Use intravascular imaging to precisely measure lesion length
   • Identify healthy landing zones for stent edges

2. Optimal stent selection:

   • Choose DES over BMS for longer lesions (>15 mm)
   • Select stent length that covers the entire lesion but minimizes excess stent length beyond lesion boundaries

3. Procedural optimization:

   • Ensure adequate lesion preparation, especially for longer lesions
   • Confirm optimal stent expansion throughout the entire stent length
   • Verify absence of edge dissections or geographic miss

By carefully considering stent length and optimizing stent deployment techniques, the risk of in-stent restenosis can be significantly reduced, particularly when using drug-eluting stents for longer lesions.