Dedicated Bifurcation Stents Strategy

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Abstract

Coronary bifurcation lesions represent an area of ongoing challenges in interventional cardiology, mainly due to the higher rate of residual stenosis and restenosis at the side branch ostium. Multiple two-stent bifurcation strategies, including T-stenting, V-stenting, simultaneuos kissing stenting, culotte stenting and classic crush techniques, have no advantages over one-stent techniques. This led to provisional stenting being considered as a mainstream approach, based on the results of numerous randomised trials. Dedicated bifurcation stents have been designed specifically to treat coronary bifurcations with the aim of addressing some of the shortcomings of the conventional percutaneous approach and facilitating the provisional approach. The development of more drug-eluting platforms and larger studies with control groups demonstrating their clinical applicability, efficacy and safety are required before these stents are widely incorporated into daily practice.

Disclosure
The authors have no conflicts of interest to declare.
Correspondence
Shao-Liang Chen, Nanjing First Hospital, Nanjing Medical University, Nanjing, Jiangsu, China. E: chmengx@126.com
Received date
07 July 2009
Accepted date
10 August 2009
Citation
ICR - Volume 4 Issue 1;2009:4(1):70-72
DOI
http://dx.doi.org/10.15420/icr.2009.4.1.70

Bifurcation lesions account for approximately 20–30% of all percutaneous coronary interventions (PCIs). Coronary bifurcation sites are prone to developing obstructive atherosclerotic disease due to turbulent blood flow and change of shear stress. With the complexity of bifurcation lesions, several classification systems have been advocated in order to extablish percutaneous strategies.1–3 In fact, dedicated quantitative coronary angiography (QCA) software is still needed to overcome the shortcomings of conventional QCA.4 Most importantly, a suboptimal result in the side branch (SB) due to residual stenosis at the SB may not be physiologically significant, even in the modern era of drug-eluting stents (DES).5–7 As a result, optimised provisional stenting is the treatment of choice.8–10 However, in some situations where bifurcation lesions have certain anatomical configurations or bifurcation angles, two-stent techniques are critically needed. This article will summarise the recent development of dedicated bifurcation stents.11–29

Abbott Frontier™

The Abbott Frontier™ (Abbott Vascular Devices, Redwood City, CA, US/Guidant Corporation, Santa Clara, CA, US) coronary stent (see Figure 1B) system is a balloon-expandable stainless-steel stent pre-mounted on a dedicated delivery system with two balloons (monorail for the main branch [MB] vessel and an over-the-wire inner lumen for the SB vessel) and two guidewire lumens. To assist tracking and avoid guidewire crossing, the Abbott Frontier has an integrated tip design that allows single tip delivery; the MB balloon tip includes a pocket on the distal sleeve for joining the MB and SB balloon tips with a mandrel. The Abbott Frontier is advanced into the MB over a conventional wire. The joining mandrel is then retracted, releasing the over-the-wire SB tip, and a 300cm wire is inserted into the SB balloon lumen and into the SB. The system is advanced to the carina and simultaneous kissing inflation of the two balloons is performed, using a single indeflator, to expand the stent on the MB and SB. The next generation of the Abbott Frontier will be a chromium–cobalt stent using the Xience DES platform.

AST SLK View™

The AST SLK-View™ (Advanced Stent Technologies, Pleasanton, CA, US) is a stainless-steel flexible slotted tube stent with a side aperture located between the proximal and distal sections to facilitate access to the SB after deployment of the stent in the MB. The delivery system has a dual over-the-wire design with a proximal dual lumen shaft that separates into two catheters (a balloon and a side sheath) at its distal segment. The stent is pre-mounted in the distal segment of the delivery system with the side sheath running under the proximal segment of the stent and exiting through the side hole. There are a total of three radio-opaque markers on the balloon, located at the centre, proximal and distal edges. The AST SLK-View system is placed over two wires simultaneously and advanced to the bifurcation until the centre marker band is aligned to the SB and the side sheath marker separates from the centre marker. The AST SLK-View stent is then deployed in the MB, leaving the pre-formed side hole positioned at the ostium. However, this stent has been removed from the market as the manufacturer has been acquired by Boston Scientific, who slightly modified the stent to create the Petal™ stent system.

Petal

The Petal stent (Boston Scientific, Natick, MA, US) (see Figure 1A), with a side aperture located mid-stent and deployable struts, may be an attractive solution to prevent SB occlusion after MB stenting. A guidewire is placed in the MB and another in the SB. The dual side exchange (double-balloon) delivery system has a main lumen that guides the catheter to the primary lesion over the main vessel guidewire. The secondary lumen (side sheath) facilitates proper alignment of the aperture to the SB ostium as it tracks over the SB guidewire. In addition to a conventional cylindrical balloon, there is a secondary elliptical balloon adjacent to the main balloon and connected to the same inflation lumen so that a single inflation device is needed. The Petal stent is crimped over both balloons such that the elliptical balloon is under the side aperture and petal elements. Upon inflation, the main balloon deploys the stent into the MB, while the elliptical balloon deploys the petal elements into the SB ostium The purpose of the petal aperture is to retain access to the SB during and after deployment and to scaffold the SB with outwardly deploying strut elements that extend up to 2mm into the branch during deployment. The Petal stent was acquired by Boston Scientific in 2004 and modified into the Taxus Petal™ stent, which is currently under investigation.

Cappella Sideguard™

The Cappella Sideguard™ (Capella Inc., MA, US) ostium protection device (see Figure 2A) is a self-expanding trumpet-shaped nitinol stent that is deployed using a special balloon-release sheath system. It is currently a bare-metal stent, but the next generation will be drug-eluting. The Cappella Sideguard’s trumpet-shaped design helps the stent conform to the ostium, allowing for complete stent-to-wall apposition. Its short length, self-expandable nitinol system and low-profile delivery system allow greater navigability even in very tortuous anatomy. Radio-opaque markers located at the distal and proximal ends of the delivery system facilitate positioning of the stent at the SB ostium. The stent is deployed using a nominal pressure balloon, which helps tear a protective sheath that keeps the Cappella Sideguard in place until deployment. Once released, the Cappella Sideguard self-expands into place. The delivery system and the guidewire are then removed from the SB. A conventional stent is then placed in the MB, the SB is re-accessed with a guidewire and the procedure is completed with a standard kissing inflation. The new device has undergone minor changes to the stent delivery system and a major change to the stent design.

Devax Axxess Plus™

The Devax Axxess Plus™ stent (Devax, Irvine, CA, US) (see Figure 2B) was the first of these dedicated bifurcation stents designed to elute an antirestenotic drug. It delivers Biolimus-A9, a sirolimus derivative, via polymer carrier. The Devax Axxess Plus is a self-expanding, nickel– titanium, conical stent that is placed at the level of the carina. It has a rapid-exchange delivery system with hydrophilic coating and controlled deployment upon withdrawal of a cover sheath using the actuator. However, the Devax Axxess stent may be limited by the fact that it needs to be precisely nested at the carina to be effective and in the majority of cases will need another stent to fully treat the bifurcation.

Invatec Twin-Rail™

The Invatec Twin-Rail™ (invatec S.r.l, Brescia, Italy) (see Figure 1C) is a slotted-tube, stainless-steel stent pre-mounted on double balloons in its proximal portion, and only on the MB balloon in its distal portion. The stent has a closed-cell design with variable stent geometry. This 6F-compatible system consists of a single dual-lumen catheter splitting into two distal balloons with a central stopper that prevents further advancement of the stent delivery system when the carina is reached. The stent is deployed by simultaneous kissing inflation with a single indeflator.

Minvasys Nile Croco™

The Minvasys Nile Croco™ (Minvasys, Genevilliers, France) (see Figure 1D) is a double-balloon stent delivery system with two independent yet joined catheters that require independent manipulation and pressure monitoring. The two rapid-exchange parallel catheters are pre-mounted with a chromium–cobalt stent crimped on the MB balloon and the tip of the SB branch balloon. The MB balloon has three markers, with the central marker indicating the position of the SB branch aperture. After the stent is deployed into the MB, the SB balloon is advanced into the SB and a final kissing inflation is performed.

Stentys™

The Stentys™ (Stentys S.A.S., Clichy, France) bifurcated drug-eluting stent is the first of the next-generation bifurcation stents. The Stentys is a self-expanding nitinol stent made of Z-shaped mesh linked by small interconnections. The stent is coated with paclitaxel on a polymer matrix that permits controlled drug elution.
The unique feature of this stent is the ability to disconnect the stent struts with an angioplasty balloon. Thus, an opening for the SB can be created anywhere in the stent after it is implanted in the vessel while at the same time the disconnected struts scaffold the SB ostium. The implantation procedure is performed in three steps. First, Stentys is implanted in the MB with an approximate positioning, just like a standard stent. Second, the optimal location for the SB opening is chosen by inserting a balloon through the stent mesh. Third, the balloon inflation disconnects the mesh and creates the opening. It is hoped that the self-expanding property of the stent will allow in situ modelling of the stent to fit the patient’s unique arterial anatomy. However, it is not known whether the Stentys is more prone to stent fracture due to its disconnectable strut design.

Trireme Antares SAS™

The Triereme Antares Sidebranch Adaptive Stent™ (SAS™) (Trireme Medical Inc., CA, US) with automatic SB support deployment consists of a single balloon-expandable stainless-steel stent. It has an SB support structure in the centre of the stent with radio-opaque tantalum markers for positioning and orientating at the bifurcation site. The original Trireme Antares SAS system had four radio-opaque tantalum markers, but the current system has only two markers.

Stent deployment is achieved using a single rapid-exchange balloon catheter and a SB branch stabilising wire encased in a peel-away lumen to minimise wire crossing. As the stent approaches the targeted bifurcation, the catheter is torqued to align the stent central opening with the SB ostium. The SB wire is advanced into the ostium, thus assisting with accurate placement and facilitating access after MB stent deployment. Upon expansion of the main stent body, the ostial crown is automatically deployed with elements protruding approximately 2mm into the SB to scaffold the ostium.

Tryton™

The Tryton™ ISB stent (Tryton Medical, MA, US) is a slotted-tube cobalt–chromium balloon-expandable stent designed to be implanted in the SB of a bifurcation. The stent consists of three zones: a distal SB zone, which treats the disease in the SB; a transition zone, which is positioned at the SB ostium; and an MB zone. The central transition zone has a specific geometry that contains three panels, each of which can be deformed in an independent fashion. The proximal MB zone is composed of three fronds that are connected proximally to the transitional panel and terminate in a circumferential band; the distal zone has the design characteristics of a standard slotted-tube workhorse stent. Treatment of a bifurcation with the Tryton stent generally commits the operator to implanting two stents in the bifurcation, and the technique is identical in approach when performing the culotte technique (see Figure 3B–G). The Tryton™ stent is deployed across the SB ostium first.

Y-Med SideKick™

The Y-Med Sidekick™ (Y-med Inc., San Diego, CA, US) is a low-profile stent delivery system that integrates an MB fixed-wire platform with a rapid-exchange steerable SB guidewire designed to preserve SB access during bifurcation stenting. There are three models with different exit ports (proximal, mid and distal); the selection is made depending on the location of the disease in the bifurcation. When the device is close to the carina, a guidewire is passed through the SB exit port and MB stent struts into the SB branch, thus avoiding re-crossing into the SB.

BIGUARD™

The BIGUARD™ stent (Lepu Medical Ltd, Beijing, China) (see Figure 3A) is a novel drug-eluting stent platform that is specifically designed for the treatment of ostial SB stenosis,as it provides enough space for exchange of devices in the main vessel (see Figure 3). This stent is expected to facilitate the use of different single- or double-stenting techniques for the treatment of coronary bifurcation lesions. It has a crossing profile of 0.038 inches and a maximum profile of 0.053 inches. This stainless-steel stent is tailored for drug elution with 100micrometers of stent strut thickness and is comparable to a 6Fr guiding catheter. Geographically, three stent struts at the proximal segment (usually 3mm in length) are separated at every 120°, with the encircled space being large enough to allow the advancement of all kinds of devices, including guidewires, balloons and stents. The final stent diameter depends on the balloon diameter used. For example, a 4.0mm diameter balloon can open the 2.5mm stent up to a 4.0mm diameter. Interestingly, one need not advance another guidewire to the parent vessel immediately after stenting of the SB with the BIGUARD stent system. There are three golden markers on the stent, allowing precise positioning of the SB ostium. Moving the SB wire directly into the main vessel negates the need for guidewire recrossing. The geographical characteristics of the BIGUARD stent facilitate the performance of double-kissing crush stenting and culotte techniques. Ôûá

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