The introduction of the ABSORB bioresorbable vascular scaffold (BVS) provides a new tool for stenting in interventional cardiology. Initially, relatively simple coronary artery lesions were treated with this novel device; nowadays, we are gaining clinical experience when treating a wide variety of lesions with the ABSORB BVS, including bifurcation lesions. Unfortunately, data are limited in terms of the use of the ABSORB BVS in coronary bifurcation lesions, so little is known about the safety and feasibility of these procedures. Bench testing and case reports showed that single provisional scaffold placement is feasible with fenestration of the scaffold towards the side branch and sequential non-compliant balloon inflation in the side and main branches. However, no prospective randomised clinical data with optical coherence tomography (OCT) imaging for different bifurcation stenting techniques are available. Based on the available data and our own experience we would recommend the use of the provisional single scaffold technique and only to fenestrate the scaffold if a severely pinched ostium combined with impaired flow seen on angiogram.
In the past three decades, significant progress has been made in the treatment of coronary artery disease. From the introduction of balloon angioplasty by Andreas Grüntzig in 19771 to metallic drugeluting stents with thin stent struts coated with cytotoxic or cytostatic drugs,2,3 with biocompatible/biodegradable polymers,4 with or without endothelial progenitor cell-capturing technology.5 However, current standard treatment with metallic stents has its shortcomings, such as late in-stent restenosis, late and very late stent thrombosis, impaired vasomotion in the stented segment6–8 and hindrance of repeat revascularisations. To potentially overcome the shortcomings of metallic stents, fully bioabsorbable stents (i.e. scaffolds) were developed.9 After preclinical testing and clinical evaluation in relatively simple coronary artery lesions,10–12 the ABSORB everolimus-eluting bioresorbable vascular scaffold (BVS) received CE-mark approval on 14 December 2010 and is since then increasingly being used in clinical practice across Europe and the rest of the world. This adoption in clinical practice led to a broad extension of, officially offlabel, indications in which the ABSORB BVS is being used, such as ST-segment elevation myocardial infarction (STEMI),13 chronic totally occluded (CTO) arteries and bifurcation lesions.
The use of bioresorbable technology in coronary bifurcation lesions may have potential benefits compared with metallic stents. For example, bioresorbable scaffolds could prevent permanent obstruction of a side branch (SB) after full absorption of the struts in front of this SB, leading to increased blood flow in the SB. Another potential benefit of the ABSORB BVS in bifurcation lesions might be a lower risk of late stent thrombosis, due to the absorption of non-apposed SB (NASB) struts at long term. These NASB struts are known to be often uncovered and thus a potential nidus for stent thrombosis.14 However, in all preclinical and clinical trials on the BVS, patients with SB ≥2 mm were excluded from enrolment, so limited data are available about the use of the BVS in bifurcation lesions. Therefore, the ‘Instructions for use’ of the ABSORB BVS does not indicate the use of the device in lesions involving a SB >2.5 mm. This led to some practical concerns about the use of the ABSORB BVS in coronary bifurcation lesions. For example, does the ABSORB BVS, with a strut thickness of 150 μm, allow for the same bifurcation techniques being used in metallic stent? Is the BVS, due to the lactic acid material, easier to fracture? This article will focus on data provided from in vitro and in vivo assessment of the ABSORB BVS in coronary bifurcation lesions and will provide practical recommendations based on these data and our own experience.
in vitro evaluation
Džavík and Colombo recently reported several bifurcation bench tests in which the ABSORB BVS is evaluated in a synthetic arterial model.15 Bifurcation stenting techniques tested included provisional stenting with final kissing balloon inflation (FKBI), modified T-stenting with a FKBI, double or two-step crush technique, mini-crush technique and culotte technique. The investigators used non-compliant (NC) balloons only, to prevent overexpansion of the scaffold due to increased balloon diameters. All procedures were assessed visually and by scanning electron microscopy (single scaffold techniques) and by microcomputed tomography (two scaffold techniques).
<>The investigators did not see any malapposition or strut fractures after FKBI in provisional stenting of a 3.0x18 mm BVS. FKBI in the provisional stenting technique was performed with a 2.5x20 mm balloon in the SB and 3.0x20 mm balloon in the main branch, both inflated at 8 atmospheres. Strut fractures were observed when FKBI was performed after T-stenting technique using a 3.0x18 mm BVS in the main branch (MB) and a 2.5x18 mm BVS in the SB and 3.0x20 mm (MB) and 2.5x20 mm (SB) balloons inflated at 10 atmospheres. The double- and mini-crush techniques both resulted in mild protrusions of BVS struts in the main branch. Even so, the double-crush technique showed a small area of malapposition between the carina and the two overlying scaffolds (see Figure 1). Likewise, a small area of malapposition was seen if the culotte technique was used, this technique also led to a thick circumferential two-layer scaffold wall in the proximal segment of the MB as well as a bulky BVS neocarina.
Based on their observations, the authors recommended to use provisional stenting in the majority of cases, with sequential noncompliant balloon inflation in the SB and the MB and reserving FKBI only if absolutely necessary. Restricted use of planned two-stent techniques, like crush or culotte, was recommended as more bench testing is needed to evaluate the feasibility of these techniques. These recommendations are supported by other bench test studies, performed by White et al. presented at Transcatheter Cardiovascular Therapeutics (TCT) 2013.sup>16
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