How can I accurately measure coronary lesion length and correctly position a stent during percutaneous coronary intervention (PCI)?

Accurate Measurement and Positioning of Coronary Stents During PCI

Use intravascular imaging (IVUS or OCT) to measure lesion length and guide stent positioning—this approach reduces major adverse cardiac events by approximately 50% compared to angiography alone. 1

Why Intravascular Imaging is Essential

Angiography alone systematically underestimates lesion length due to vessel foreshortening, leading to geographic miss and edge complications. 1 The 2023 ACC/AHA/SCAI guidelines assign a Class 2a recommendation to intravascular imaging for procedural guidance in complex coronary PCI, specifically to reduce ischemic events. 1

Clinical Impact of Imaging-Guided PCI

• IVUS-XPL trial (long lesions ≥28 mm): MACE reduced from 5.8% to 2.9% at 1 year (HR 0.48, P=0.007) with IVUS guidance. 1
• ULTIMATE trial (all-comers, average lesion >30 mm): Target vessel failure reduced from 5.4% to 2.9% (HR 0.530, P=0.019) with IVUS guidance. 1
• CTO-IVUS trial: MACE reduced from 7.1% to 2.6% (HR 0.35, P=0.035) with IVUS guidance. 1

Step-by-Step Protocol for Lesion Measurement

Pre-Intervention Assessment

1. Administer intracoronary nitroglycerin before any measurements to eliminate vasospasm and obtain true vessel dimensions. 1

2. Position the imaging catheter 20 mm distal to the area of interest and perform automated pullback to the left main or right coronary ostium. 1

3. Identify reference segments as cross-sectional images adjacent to the lesion with minimal disease. 1

4. Measure lesion length as the distance between distal and proximal reference segments using the imaging console's automated measurement tools. 1

Choosing Between IVUS and OCT

IVUS is preferred for:

• Aorto-ostial lesions (no contrast needed, avoiding blood admixture artifact) 1, 2
• Left main disease (deeper penetration 5-6 mm captures larger vessels) 1
• Chronic total occlusions (contrast pressurization could be harmful) 1
• Heavily calcified lesions (ultrasound penetrates calcium) 1

OCT is preferred for:

• Precise side-branch location identification (10× higher resolution than IVUS) 1
• Detecting edge dissections (superior sensitivity for intimal/medial tears) 1
• Automated lesion length measurement with high accuracy 1

Critical Measurement Parameters

Lesion length: Distance from proximal to distal reference segment where plaque burden becomes <50%. 1

Reference vessel diameter: Measure at both proximal and distal reference segments; use the smaller value for stent sizing to avoid oversizing. 1

Minimum lumen area (MLA): Identify the slice with the smallest lumen area within the lesion. 1

Stent Positioning Algorithm

Step 1: Select Stent Length

Add 3-5 mm margin proximally and distally beyond the measured lesion length to ensure complete plaque coverage and avoid edge dissection. 3

Common pitfall: Angiography underestimates length by 2-3 mm on average compared to 3D reconstruction or IVUS. 4, 5 Standard 2D QCA measurements are consistently shorter than marker guidewire measurements (by 1.9 ± 2.8 mm). 5

Step 2: Position Stent Markers

Use imaging to identify exact landing zones:

• Proximal edge: 3-5 mm proximal to lesion start, in a segment with plaque burden <50% 3
• Distal edge: 3-5 mm distal to lesion end, in a segment with plaque burden <50% 3

For ostial lesions (e.g., ostial LAD): Deploy stent extending 1-2 mm into the left main body to ensure complete ostial coverage. 2

Step 3: Deploy and Optimize

Deploy at nominal pressure based on manufacturer specifications for the reference vessel diameter measured by imaging. 1

Perform high-pressure post-dilation (83.7% of IVUS-guided cases vs 75.4% angiography-guided). 1 Target stent-to-reference vessel diameter ratio ≥1.1. 1

For bifurcation lesions: Perform mandatory kissing-balloon inflation in both branches after stent deployment to prevent side-branch compromise. 2

Post-Deployment Verification

Mandatory IVUS/OCT Assessment Criteria

Minimum stent area (MSA): Must be >5.0 mm² OR ≥90% of distal reference segment area. 3

Stent expansion: Stent-to-reference vessel diameter ratio should be ≥1.1 to <1.3. 1

Edge assessment:

• No dissection involving media with length >3 mm 3
• Plaque burden <50% within 5 mm of stent edges 3
• No residual stenosis >50% at stent edges 3

Stent apposition: No malapposition (gap between stent struts and vessel wall). 3

Managing Edge Dissections

Dissections requiring correction (all must be met): 3

• Circumference >60 degrees (120 degrees significantly exceeds safe threshold)
• Length >2 mm (4 mm requires immediate correction)
• Involvement of media or adventitia

Correction method: Implant additional stent covering dissection zone with 3-5 mm margins proximally and distally. 3

Common Pitfalls to Avoid

Do not rely on angiography alone for length measurement—foreshortening causes systematic underestimation, leading to geographic miss in 20-30% of cases. 1, 4, 5

Do not stent segments with plaque burden >50%—this is associated with edge dissection and restenosis. 3

Do not leave edge dissections uncorrected if they meet intervention criteria—extensive dissections significantly increase acute thrombosis risk. 3

Do not skip post-deployment imaging—residual stent edge dissections occur in 4.6% of IVUS-guided cases but are often invisible on angiography. 1

Avoid undersizing—33.1% of angiography-guided lesions had stent-to-vessel ratio <1.0, associated with worse outcomes. 1

Alternative When Imaging Unavailable

If intravascular imaging is truly unavailable, use 3D quantitative coronary angiography (3D-QCA) rather than standard 2D QCA:

• 3D-QCA measurements are 2.3 ± 2.5 mm longer than 2D QCA (P<0.001) 4
• 3D-QCA correlates better with marker guidewire measurements (gold standard) 5
• Accuracy maintained even with foreshortened projections 4, 6

However, this remains inferior to direct intravascular imaging for clinical outcomes. 1