A challenging technical scenario frequently encountered in a percutaneous coronary intervention of a coronary bifurcation lesion (CBL) is stent implantation of only the stenosed segment without compromising the other two normal segments in non-true bifurcation lesions. Another is precise stent implantation covering the side branch ostium without leaving excessive stent metal at the other two segments of a bifurcation lesion in complex true bifurcation lesions. The aim of this study was to describe a novel stenting technique for both non-true and true CBLs by using a guide extension catheter (GuideLiner). With the assistance of a guide extension catheter mounted on both the main and the side-branch guidewires and with its intubation down to the bifurcation carina, a stent can be implanted in the side branch segment or distal main segment of the bifurcation lesion appropriately without compromising the other two segments of the coronary bifurcation. Stent implantation is described in three bifurcation lesions in three cases and shown in detail with illustrative figures. The technique facilitates side-branch only stenting in side-branch mono-ostial (medina 0, 0, 1) CBL or only the distal main segment in distal mono-ostial (medina 0, 1, 0) CBL without compromising the other two remaining segments when using the one-stent technique in non-true CBLs without leaving unnecessary excessive stent metal at the bifurcation site and when using a two-stent technique in complex true bifurcation lesions (tri-ostial or medina 1, 1, 1). Consequently, through optimizing stent deployment, the technique may have the potential to reduce the risk of subacute stent thrombosis and future in-stent restenosis. The most appropriate lesions suitable for the technique, and some other practical tips are also described.

Percutaneous coronary intervention (PCI) of a coronary bifurcation lesion (CBL) is a challenging procedure for interventionists[1]. The short- and long-term outcomes are closely related to the procedural success and optimization of the bifurcation stenting technique[2,3]. Several one- or two-stent techniques for PCI of CBLs have been described, depending on the type and location of the bifurcation lesions[1,4]. Stenting of the side branch in side-branch mono-ostial[5] (medina 0, 0, 1)[6] bifurcation stenoses is associated with difficulties in stent placement at the proper site with the risk of missing the side branch ostium or of excessive stent protrusion in the main branch. The same applies to stenting only the distal main segment in distal mono-ostial (medina 0, 1, 0) bifurcation stenoses. Consequently, the provisional stenting technique is typically employed in treating a distal mono-ostial stenosis (medina 0, 1, 0) but this requires “unnecessary” stenting of the normal proximal main segment of the bifurcation and the risk of compromising the side branch[1].

The provisional stenting technique is also recommended as the default strategy by most interventionists in tri-ostial (medina 1, 1, 1) or true bifurcation lesions[1]. However, this technique may lead to side-branch occlusion during stenting of the main branch and acute peri-procedural myocardial infarction. Improvements in the protection of the side branch have been reported with the jailed balloon protection of the side branch[7] or modified jailed balloon techniques[8]. The risk of side-branch occlusion is increased in complex tri-ostial (medina 1, 1, 1) bifurcation lesions where a two-stent technique should always be considered. However, the current two-stent techniques for the CBLs, such as crush[9] and culotte[10] stenting, leave multiple layers of stent struts at the bifurcation site causing difficulties in rewiring, balloon re-crossing, and the performance of sequential post-dilatation and final kissing balloon inflation. This may result in stent under expansion, and/or malapposition at the bifurcation site predisposing to acute and sub-acute stent thrombosis. Suboptimal stent implantation is also associated with an increased risk of future in-stent restenosis[1]. To overcome these challenges, the crush technique has evolved to mini-crush and double kissing (DK)-crush techniques[1]. The DK-crush stenting technique facilitates final kissing balloon inflation, but the technique has complex procedural steps and is time consuming. Other two-stent techniques include simultaneous kissing stenting, T-stenting and V-stenting techniques. The T-stenting technique does not leave multiple layers of stent struts, which facilitates final kissing balloon inflation, but has the potential of geographical miss at the side branch. These technical shortcomings highlight the need for a stent implantation technique that avoids unnecessary stenting of the normal segments and not leaving multiple layers of stent struts at the bifurcation site. A guide extension catheter can intubate the coronary arteries down to the carina of the bifurcation site. This may facilitate precise stent implantation at the ostium of the side branch or the distal main segment and thus enhance rewiring, balloon re-crossing and final kissing balloon inflation in two-stent techniques.

Three different types of CBLs in three cases that were successfully treated with PCI using a GuideLiner-assisted stenting technique. Two cases had non-true CBLs and one had a true CBL. The first case had left main stem/LCx/LAD bifurcation stenosis of a side-branch type mono-ostial (medina 0, 0, 1) bifurcation lesion. With a GuideLiner advanced to the carina of the bifurcation, the side branch (LAD) was stented successfully (Figure 2). The stent covered the ostium of the LAD without leaving stent struts in the left main stem or LCx, confirmed by StentBoost imaging (Figure 2F). The bifurcation lesion in the second case treated with this novel technique was a LAD/ diagonal bifurcation stenosis type distal mono-ostial (medina 0, 1, 0) where the stenosis was restricted to the distal main segment of the bifurcation. It is worth mentioning that visualization of the angle between the diagonal branch and the distal segment of the main branch (LAD) was ambiguous, making it especially suitable for this novel technique. With a GuideLiner intubated down to the carina of the bifurcation, the distal main segment was stented successfully (Figure 3). The stent covered the ostium of the distal main segment without leaving stent struts in proximal main segment or the side branch and this was confirmed by OCT (Figure 3E and F), which also showed a well-apposed stent to the vessel wall. The bifurcation lesion in the third case was a complex LAD/diagonal bifurcation stenosis of type tri-ostial (medina 1, 1, 1) (Figure 4). The side branch was stented by this novel technique after extending the GuideLiner to the carina of bifurcation. The stent covered the side-branch ostium without leaving stent struts at the bifurcation site. The main branch is then stented in the conventional way without leaving multiple layers of stent struts at the bifurcation site. Consequently, the procedure enhanced rewiring, balloon re-crossing and the performance of sequential post-dilatation and final kissing balloon inflations. StentBoost and optical coherence tomography confirmed well-apposed stents at the bifurcation site with no stent struts covering the ostium of the diagonal branch (Figure 4H and I)

The main advantage of the guide extension-assisted stenting technique is precise positioning of the stent at the side branch of a CBL especially in lesions where the side-branch ostium is challenging to visualize or ambiguous. The most appropriate CBLs suitable for this technique are the side-branch mono-ostial (medina 0, 0, 1), distal mono-ostial (medina 0, 1, 0), and potentially distal bi-ostial (medina 0, 1, 1) CBLs. In such lesions, the guide extension-assisted technique avoids stenting of the normal proximal segment of the bifurcation with its subsequent risk of compromising the other branch of the bifurcation, and the subsequent need for re-crossing the stent struts for final kissing balloon inflation. The guide extension assisted technique can also be utilized for stenting the side-branch lesion in complex tri-ostial (medina 1, 1, 1) bifurcation lesions as demonstrated Figure 4.

The bifurcation PCI principle of “keep it open” for the side branch and the provisional side-branch stenting, is currently regarded as the default procedure in the majority of bifurcation lesions, in part attributable to the fact that the two-stent techniques (crush and culotte) are more complex and may leave stent struts under expanded or malapposed, with increased risk of acute or subacute stent thrombosis and future in-stent-restenosis. However, in complex bifurcation lesions, the risk of compromising the side branch is substantial with a provisional approach. The incidence of side-branch occlusion was 13.4% for true bifurcation and 4.0% for non-true bifurcation lesions in a bifurcation stenting registry enrolling 2227 cases of bifurcation PCIs treated by the one-stent approach[14]. For this reason, a two-stent technique is frequently necessary for complex true bifurcation lesions. The DK-crush technique has been shown to be superior to the provisional side-branch stenting as well as to culotte techniques in terms of efficacy and safety[1,3]. Nonetheless, it must be recognized that the DK-crush technique is technically demanding and time consuming.

A simplified two-stent technique, which does not leave excess layers of stent struts at the bifurcation site, is thus highly desirable. The guide extension-assisted stenting technique for the side branch does not leave unnecessary stent metal in the main branch as may occur with crush and culotte techniques and consequently avoids the subsequent risks of subacute stent thrombosis and difficulties in performing rewiring, balloon re-crossing the stent strut toward the side branch, sequential balloon dilatation, and final kissing balloon inflation.

A novel guide extension-assisted stenting technique for selected CBLs is described. This technique facilitates stenting only the diseased side branch or distal main segment in non-true bifurcation lesions without compromising the other branches. It may also facilitate precise stenting implantation in the side branch when using two-stent techniques in complex true bifurcation stenoses without leaving excess stent struts at the bifurcation site, which facilitates easier rewiring, balloon re-crossing, and performing final kissing balloon inflation. The technique may potentially reduce the risks of acute and subacute stent thrombosis as well as future in-stent restenosis and is worthy of further investigation.