How to identify stent fracture in Optical Coherence Tomography (OCT)?

Identifying Stent Fracture in Optical Coherence Tomography (OCT)

Stent fracture in OCT can be identified by observing discontinuities in stent strut patterns, including single or multiple stacked struts, deformation without gaps, or complete transection of the stent structure. 1

Key OCT Features of Stent Fracture

Primary Diagnostic Patterns

• Single stacked strut (41% of cases) - Isolated discontinuity in the expected circular pattern of stent struts 1
• Multiple stacked struts (23% of cases) - Two or more stacked struts appearing in unexpected positions 1
• Deformation without gap (27% of cases) - Distortion of normal stent architecture without complete separation 1
• Transection (9% of cases) - Complete separation of stent segments with visible gap 1

Technical Considerations for OCT Assessment

• Metal stent struts appear as bright, highly reflective structures with shadowing behind them 2
• Only the first (leading) surface of individual struts is visible due to the opacity of metal to light 2
• Careful longitudinal and cross-sectional examination is required to detect subtle discontinuities

Associated OCT Findings That Suggest Stent Fracture

• Stent strut dissociation - Disappearance of stent struts in cross-sectional images that were previously visualized 3
• Abnormal stent geometry - Device eccentricity and asymmetry are associated with stent fracture 1
• Impaired strut healing - Areas with incomplete endothelialization or delayed healing 1
• Malapposition - Increased distance between strut surface and vessel wall (>strut thickness) 2

Risk Factors for Stent Fracture Visible on OCT

• Calcified lesions - Heavy calcification increases fracture risk (OR: 3.5) 1
• Bifurcation lesions - Higher risk of fracture (OR: 4.0) 1
• Stent design - Open-cell designs may be more prone to deformation than closed-cell designs 4

Clinical Significance and Complications

• Stent fractures are associated with increased risk of device failure:
  • Restenosis (OR: 24.9 for drug-eluting stents) 1
  • Thrombosis (OR: 6.0 for bioresorbable scaffolds) 1
• May lead to acute myocardial infarction due to plaque rupture at fracture sites 5

Diagnostic Algorithm

1. Perform systematic OCT assessment:

   • Evaluate full stent length in both cross-sectional and longitudinal views
   • Compare with baseline post-implantation OCT if available

2. Look for specific fracture patterns:

   • Discontinuity in the circular pattern of struts
   • Stacked struts in abnormal positions
   • Deformation of expected stent geometry
   • Complete separation of stent segments

3. Assess surrounding tissue:

   • Check for thrombus formation at fracture sites
   • Evaluate for restenosis or neointimal proliferation
   • Look for plaque rupture or dissection near fracture points

4. Compare with other imaging modalities when available:

   • IVUS is less sensitive than OCT for detecting stent fracture 3
   • Fluoroscopy may miss fractures that OCT can detect 3

Pitfalls and Caveats

• Tissue coverage - Very thick tissue coverage (>0.3mm) can obscure stent struts and make fracture detection challenging 6
• Multiple stents - Overlapping stents require careful assessment to distinguish between normal overlap and fracture 6
• Artifacts - Guide wire artifacts, blood artifacts, and suboptimal flushing can mimic stent discontinuity
• False negatives - Angiography alone may miss stent fractures that are detectable by OCT 3

OCT remains the most sensitive imaging modality for detecting stent fracture due to its high resolution and ability to visualize individual stent struts, even when covered by tissue.