There are two measurement methods used to determine stent diameter sizing:

• External Elastic Lamina
• Luminal Measurement

External Elastic Lamina

Benefits of using External Elastic Lamina to determine stent diameter:

• Luminal OCT guided measurement PCI may lead to stent under-sizing, when compared to intravascular ultrasound (IVUS) likely due to incomplete vessel wall visualization.
• Stent sizing based on pre-intervention OCT measurements of the external elastic lamina (EEL) overcomes the problem of stent undersizing.¹
• EEL based stent size decision can be made only if the EEL can be visualized in more than 180 degrees at the reference sites.
• After making multiple measurements at the distal and proximal reference segments, the mean external elastic lamina is obtained for the two reference segments. Use of the smaller of these two diameters rounded to the nearest 0.25 mm is recommended to determine stent diameter.
• For post-stenting balloon dilatation use a non-compliant balloon diameter no larger than the reference vessel external elastic lamina.¹

¹Lancet 2016; 388: 2618–28.

Figure I. External Elastic Lamina. The white arrow below indicates the external elastic lamina (EEL) which is situated directly between the media and adventitia layers.

Luminal Measurement

How to use Luminal measurement to determine stent diameter:

• Stent diameter is determined by measuring lumen diameter at the proximal and distal reference sites. In general, lumen diameter at the distal reference site is smaller than that at proximal reference site.
• Stent diameter is determined as 0–0.25 mm greater than mean lumen diameter at the distal reference site.¹
• For post-stent dilatation, a non-compliant balloon diameter up to 0.5 mm larger than the post-PCI mean reference lumen diameter is recommended.²

¹European Heart Journal, Volume 38, Issue 42, 7 November 2017, Pages 3139–3147.

²Lancet 2016; 388: 2618–28.