OCT in Pre-implantation Planning
BVS struts (e.g.,156 μm) are approximately two thirds thicker than those of modern DES. The ring structure of a BVS stent is also up to 30 % tighter. These differences make deliverability and side branch management more challenging. In addition, the possibility to overexpand BVS is limited,5 necessitating more precise device sizing compared with DES. Therefore, a special focus should be placed on the assessment of vessel calcification with BVS procedures.5 The presence of circumferential calcium but also focal calcium spots usually deserves special consideration with regard to vessel preparation (e.g., the use of rotational atherectomy, scoring balloons). The use of metal stents should also be considered, especially if OCT reveals significant remaining calcium bridges after vessel preparation. In the presence of larger calcium deposits, pronounced recoil or inadequate device expansion is more common in BVS compared with DES (see Figure 1). In some cases these problems can only be fixed with the use of an additional metallic stent (stent in BVS).
With its ability to provide exact and automatic measurement of lesion length and vessel size, OCT can aid in optimising the use of BVS.6 Overexpansion of BVS is limited compared with modern DES. Based on the authors’ experience, it is possible to dilate a modern DES stent 1.0–1.5 mm over the specified diameter. However, a BVS can only be dilated 0.5–0.8 mm over the specified diameter. Exceeding these limits increases the risk of ring fractures with consecutive strut protrusion and reduced radial strength, potentially triggering late complications such as stent thrombosis or target vessel restenosis.5,7 In regards to the choice of stent length, BVS provides a new rationale for more complete plaque sealing especially in the presence of a thin-cap fibroatheroma at the site or edges of haemodynamically significant lesions (see Figure 2). More precise knowledge of the lesion length can aid in the process.
OCT can also be used to compensate for difficulties in accessing side branches when using BVS.5 When using BVS, it seems advisable to have a closer look at the plaque characteristics near the origin of important side branches and to consider additional preparation or strategy adjustments. OCT, which enables near histologic plaque characterisation,8 can be used to assess side branches prior to BVS placement.
The publication of this information was supported by St Jude Medical.