ABSTRACT
Stent expansion post-deployment can show different patterns: adequate expansion, incomplete or underexpansion, asymmetric expansion or overexpansion.
Incomplete expansion occurs when a portion of the stent is fully pressed into the vessel wall but inadequately expanded compared with the distal and proximal reference dimensions. Incomplete expansion occurs most frequently in areas of the vessel where dense fibrocalcific or calcified plaque is present. A number of studies have shown that stent expansion as measured by IVUS is a powerful predictor of angiographic or clinical restenosis following stenting16,17. In the Multicenter Ultrasound Guidance of Stents in Coronaries (MUSIC) trial, strict adherence to IVUS optimization criteria led to a very low target vessel revascularization rate of 9%18. In MUSIC, the following IVUS criteria of optimal stent expansion were used: (1) complete apposition of the stent over its entire length against the vessel wall; (2a) in-stent minimal lumen area of ≥90% of the average reference lumen area or ≥100% of the smallest reference area (in case the in-stent luminal area was < 9.0 mm2); (2b) in-stent minimal lumen area of ≥ 80% of the average reference lumen area or ≥ 90% of the smallest reference area (in case the instent luminal area was >9.0 mm2); (3) symmetric stent expansion with minimal/maximal lumen diameter of ≥ 0.7. Several other studies14,19,20 using those criteria have confirmed their safety and that some of them could show reduction in target vessel revascularization14,20.
