The Role of Optical Coherence Tomography in the Bioresorbable Vascular Scaffold Era

Abstract

Everolimus-eluting bioresorbable vascular scaffolds (BVS) represent a novel treatment option for coronary artery disease (CAD). Initial and recent clinical results have been promising, although late lumen loss seems to be somewhat higher with BVS compared to everolimus-eluting cobalt chromium stents.1,2 In stable patients free of complex coronary lesions, clinical events reported for BVS at six and 12 months resemble those seen with modern drug-eluting stents (DES).3,4 Thus, while the short-term efficacy and safety of BVS seem to be comparable with modern DES, they may ultimately prove safer. More physiologic vessel healing may translate into decreased rates of late complications such as neoatherosclerosis, late acquired malapposition or very late stent thrombosis due to uncovered stent struts. Undoubtedly, BVS have different handling and mechanical properties than current DES. Advanced intravascular imaging modalities such as optical coherence tomography (OCT) can provide important insights into the specific properties of BVS, and thus facilitate their use. The use of OCT pre- and post-implantation of BVS as well as in long-term follow-up will be reviewed in this paper.

Support
The publication of this information was supported by St Jude Medical.
Received date
11 September 2014
Accepted date
01 August 2014
Citation
RadcliffeCardiology.com, September 2014

Pages

Introduction
Everolimus-eluting bioresorbable vascular scaffolds (BVS) represent a novel treatment option for coronary artery disease (CAD). Initial and recent clinical results have been promising, although late lumen loss seems to be somewhat higher with BVS compared to everolimus-eluting cobalt chromium stents.1,2 In stable patients free of complex coronary lesions, clinical events reported for BVS at six and 12 months resemble those seen with modern drug-eluting stents (DES).3,4 Thus, while the short-term efficacy and safety of BVS seem to be comparable with modern DES, they may ultimately prove safer. More physiologic vessel healing may translate into decreased rates of late complications such as neoatherosclerosis, late acquired malapposition or very late stent thrombosis due to uncovered stent struts. Undoubtedly, BVS have different handling and mechanical properties than current DES. Advanced intravascular imaging modalities such as optical coherence tomography (OCT) can provide important insights into the specific properties of BVS, and thus facilitate their use. The use of OCT pre- and post-implantation of BVS as well as in long-term follow-up will be reviewed in this paper.

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).


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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.


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References
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