CATHETER SYSTEM FOR STENTING BIFURCATED VESSELS
FIELD OF THE INVENTION
The present invention relates generally to catheters and catheter systems for performing angioplasty and vascular stenting. More particularly it relates to a catheter system for stenting a vessel at a bifurcation or sidebranch of the vessel.
BACKGROUND OF THE INVENTION
Numerous patents and patent applications relate to catheters and catheter systems for performing angioplasty and stenting of bifurcated vessels. For instance stent and catheter assembly and method for treating bifurcations are described in the following patents and patent applications:
US 6,579,312, US 6,540,779 US 6,508,836, US 6,428,567, US 6,387,120, US 6,383,213,US 6,361,544, US 6,221,098, US 6,165,195, US 6,013,054,US 4,896,670, US 6,129,738, US 6,544,219,US 5,749,825, US 20020183763A1, WO 9944539A2, WO 9924104,FR 2733689;
An improved catheter system for stenting bifurcated vessels has been described in international patent applications WO2005039681 and PCT/EP2006/061615.
This catheter system includes a first balloon catheter, a second balloon catheter and a linking device for holding the first and second balloon catheters in a side-by-side configuration and aligned with one another along a longitudinal axis. This catheter system also includes a first and second steerable guidewire for guiding the first and second balloon catheters within the patient's blood vessels. The linking device allows the catheter system to be advanced as a unit and helps prevent premature or inadvertent dislodgement of the stent from the catheters.
This catheter system may be arranged with the inflatable balloons in a side-by-side configuration for stenting the bifurcated vessels using a method similar to the "kissing balloons" technique. Alternatively, the catheter system may be arranged with the inflatable balloons in a low-profile staggered or tandem configuration for stenting the bifurcated vessels using a modified "kissing balloons" technique. When arranged in the staggered or tandem configuration,

the second balloon catheter may optionally be constructed with a flexible tubular extension that extends the guidewire lumen distally from the inflatable balloon.
This catheter system may include one or more vascular stents of various configurations mounted on the first and/or second balloon catheters.
In document PCT/EP2006/061615 are described some specific configurations of stents with a strut configuration optimized for stenting bifurcations. In a preferred embodiment, the stent is generally configured with a multiplicity of struts that are joined together along the length of the stent by links in an open cell configuration. The struts are preferably configured as sinuous or undulating rings extending circumferentially around the stent Each strut has a predetermined number of undulations or cells around the circumference of the stent.
According to the teaching of this document, the stent is divided into a distal area, a carina area and a proximal area and the strut configuration in each area is optimized for the portion of the vessel in which it will be placed. In a particularly preferred embodiment, the struts in the carina area have a greater number of cells than the struts in the distal area and the proximal area whereas the struts in the proximal area also have a greater number of cells than the struts in the distal area. It is specified that this configuration allows the carina area to be expanded more than the distal area and the proximal area, and allows the proximal area to be expanded more than the distal area. As a consequence the differential expansion properties of the different areas allow the stent to conform closely to the typical geometry of a bifurcated vessel, where the vessel proximal to the bifurcation typically has a greater diameter than the vessel distal to the bifurcation, and where the vessel in the carina area immediately proximal to the carina of the bifurcation has a diameter greater than the vessels proximal or distal to the bifurcation. This configuration of the stent also allows the crush resistance or hoop strength of the expanded stent to be optimized for each of the areas despite the different stent expansion ratios in each area.
An example of a 3.0 mm (expanded diameter) stent is shown in figure 23 of this document. The stent is shown with the unexpanded tubular stent laid out flat to show the strut configuration of the stent as it is manufactured and prior to crimping. In this example, the stent has six struts in the distal area each having six cells and joined together by two links, except for the most distal strut, which is joined by three links, three struts in the carina area each having eight cells and joined together by four links, and five struts in the proximal area each having seven cells and joined together by two links, except for the most proximal stmt, which is joined

by three links. A single link joins the distal area to the carina area, and three links join the proximal area to the carina area.
Another example of a 3.5 mm (expanded diameter) stent is shown in figure 25 of this document. The stent has six struts in the distal area each having eight cells and joined together by two links, except for the most distal strut, which is joined by four links, three struts in the carina area each having ten cells and joined together by five links, and five struts in the proximal area each having nine cells and joined together by three links, except for the most proximal strut, which is joined by five links. As in the example shown in figure 23 a single link joins the distal area to the carina area, and three links join the proximal area to the carina area.
SUMMARY OF THE INVENTION
While there has been considerable progress in methods of treating bifurcation lesions with stents as illustrated by international patent applications WO2005039681 and PCT/EP2006/061615, a need remains in the art to provide an improved system for stenting a vessel at the bifurcation or side branch of the vessel and more specifically a system having a design that allow it to accommodate the particular geometry of a bifurcated vessel.
In its main aspect, the present invention is directed to a stenting system comprising: a stent delivery catheter having a catheter shaft with a step balloon mounted thereon, the step balloon having a proximal portion and a distal portion, wherein the proximal portion is inflatable to a larger expanded diameter than the distal portion;
a two-part stent having a proximal part that is mounted on the proximal portion of the step balloon and a distal part that is mounted on the distal portion of the step balloon and a non-link zone between the proximal part and the distal part of the two-part stent.
The originality of the stenting system according to the invention resides in the fact that due the non-link zone between the proximal part and the distal part of the two-part stent, it is possible to obtain a structure which is a fully flexible in the carina area and which allows an easy access to a sidebranch of the vessel at a bifurcation.
In a preferred embodiment of the invention, the proximal part and the distal part of the two-part stent are each configured with stent struts that interdigitate within the non-link zone.

In another preferred embodiment of the invention, the proximal portion of the step balloon has a conical configuration.
In a further preferred embodiment of the invention, the proximal portion of the step balloon has a conical configuration that increases in diameter from a proximal end of the balloon to a distal end of proximal portion.
According to a second aspect, the present invention is directed to a two-part stent comprising a proximal part and a distal part and a non-link zone between the proximal part and the distal part of the two-part stent, wherein the proximal part and the distal part of the two-part stent are each configured with stent struts that extend like interdigitating fingers into the non-link zone.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 illustrates a two-part stent according to the present invention configured for stenting bifurcated vessels shown with the stent mounted on a stent delivery catheter.
Figure 2 is an enlarged detail drawing showing the non-linked zone of the two-part stent shown in figure 1.
Figure 3 shows the two-part stent of figure 1 in an expanded state.
Figure 4 shows the two-part stent of figure 1 expanded in a bifurcated vessel.
Figure 5 shows the bifurcated vessel after stenting with the two-part stent of Figure 1.
DETAILED DESCRIPTION OF THE INVENTION
Figure 1 illustrates a two-part stent 1 according to the present invention configured for stenting bifurcated vessels.
The two-part stent 1 is shown mounted on a stent delivery catheter 2 in an unexpanded condition.

Preferably, the stent delivery catheter 2 is configured with a step balloon 3 having a proximal portion 31 and a distal portion 32 that expand to different diameters. Typically, the proximal portion 31 will have a larger expanded diameter than the distal portion 32, as shown in figure 3. However, it should be noted that the proportions of the proximal portion 31 and the distal portion 32 can be reversed, for example for stenting a bifurcated vessel using a retrograde approach rather than a standard antegrade approach.
The proximal portion 31 of the step balloon 3 may be cylindrical or conical, as appropriate for the geometry of the bifurcation in the target vessel.
Figure 3 shows an example of a step balloon 3 with a conical proximal portion 31 that increases in diameter from the proximal end of the balloon to the distal end of proximal portion 31 and is largest in diameter adjacent to the step in the balloon.
The balloon catheter according to the invention may be of any known construction for balloon angioplasty or stent delivery catheters, including rapid exchange and over-the-wire catheter constructions.
In a particularly preferred embodiment, the balloon catheter is constructed as rapid exchange catheters, wherein a proximal section of the catheter is constructed of hypodermic tubing, which may be formed from stainless steel, a superelastic nickel-titanium or titanium-molybdenum alloy or the like. The exterior of the proximal section is preferably coated with PTFE or another highly lubricious coating. A proximal connector, such as a luer lock connector or the like, is attached at the proximal end of the proximal section and communicates with a balloon inflation lumen that extends through the hypodermic tubing. The catheter includes a flexible distal section joined to the proximal section. Typically, the flexible distal section has two lumens that extend through most of its length, including a guidewire lumen that extends from a proximal guidewire port to a distal port at the distal end of the catheter, and a balloon inflation lumen that connects from the balloon inflation lumen of the proximal section to the interior of the inflatable balloon, which is mounted near the distal end of the flexible distal section.
The inflatable balloon 3 may be made from a variety of known angioplasty balloon materials, including, but not limited to, PVC, polyethylene, polyolefin, polyamide, polyester, PET, PBT, and blends, alloys, copolymers and composites thereof.
The flexible distal section is typically constructed of flexible polymer tubing and may have a coaxial or multilumen construction.

Preferably, one, two or more radiopaque markers are mounted on the flexible distal section to indicate the location of the inflatable balloon under fluoroscopic imaging.
A transition element may be included to create a gradual transition in stiffness between the proximal section and the flexible distal section, and to avoid a stress concentration at the juncture between the two sections. The transition element may be constructed as a tapered or spiral wound element that is formed as an extension of the hypodermic tubing or from a separate piece of wire or tubing.
The two-part stent 1 has a proximal part 11 and a distal part 12 and a non-linked zone 13 between the proximal part 11 and the distal part 12.
The stent may be fabricated from a seamless metal tube, for example by laser cutting, annealing and electropolishing. The stent may be formed, for example, from a seamless tube with nominal dimensions of approximately 1.60 mm diameter, with a wall thickness of approximately 0.11 mm.
In a particularly preferred embodiment, the stent is made from a high-strength biocompatible chromium-cobalt alloy, such as alloy L605 (ASTM F90-01).Alternatively, the stent may be made from other biocompatible metals or alloys, including, but not limited to, 316 stainless steel, Elgiloy or Carpenter MP35.
Figure 2 is an enlarged detail drawing showing the non-linked zone 13 of the two-part stent 1.
The proximal part 11 and the distal part 12 of the two-part stent 1 are typically formed by cutting a metallic tube to form zigzag or undulating stent struts 14. Alternatively, the stent struts 14 can be formed from wire. In the embodiment shown, the cells are shown as simple sinusoidal undulations; however other configurations of cells including open cells and closed cells are also possible.
Optionally, the proximal part 11 and the distal part 12 of the two-part stent 1 can be made with different strut configurations, according to the principles described in PCT/EP2006/061615, to accommodate expansion to different diameters in the portions of the vessel proximal and distal to the carina region.
In a preferred configuration, the stent struts 14 form circumferential rings that are joined to one another by one or more links similar to the stent embodiments described in PCT/EP2006/061615.

However, there are no links in the non-linked zone 13 between the proximal part 11 and the distal part 12. The absence of links in the non-linked zone 13 allows greater freedom of movement between the proximal part 11 and the distal part 12 of the two-part stent 1. This effectively eliminates any difficulties in alignment of the two parts relative to one another during placement of the two-part stent 1 in a bifurcated vessel.
In one particularly preferred embodiment, the undulations of the stent struts 14 extend like fingers 16 from the distal end of the proximal part 11 and the proximal end of the distal part 12. The fingers 16, interdigitate with one another to create an overlap of the proximal part 11 and the distal part 12 in the non-linked zone 13, as shown in figure 2, in order to provide strut coverage in the carina region of the bifurcated vessel equivalent to or greater than a typical one-part stent.
The stent delivery catheter 2 with the two-part stent 1 can be used as a stand-alone catheter for stenting bifurcated vessels. Alternatively, it can be used as the first balloon catheter in PCT/EP2006/061615 in a two-catheter stenting system for bifurcated vessels similar to those shown in figures 1-5, 18 and 20-22 in PCT/EP2006/061615 for ease and simplicity in performing a kissing-balloon technique. The tandem balloon configurations shown in figures 5, 18 and 20-22 in PCT/EP2006/061615 would provide the additional benefit of a lower crossing profile, as compared to the side-by-side balloon configurations shown in figures 1-4 of this document (or two-catheter system)
When used as a stand-alone catheter, the stent delivery catheter 2 with the step balloon 3 and the two-part stent 1 allow simple stenting of a bifurcation using a provisional stenting technique. The stent delivery catheter 2 is introduced into the patient's vascular system and navigated with the aid of a guidewire to the vessel bifurcation to be stented. The step balloon 3 is maneuvered so that the non-linked zone 13 of the two-part stent 1 is positioned at the carina region of the bifurcation just proximal to the takeoff of the sidebranch vessel. Optionally, a second guidewire (not shown) may be introduced into the sidebranch vessel to maintain access to the sidebranch vessel using the "jailed wire" technique. The step balloon 3 is inflated with fluid to expand the two-part stent 1.
Figure 4 shows the two-part stent 1 of figure 1 expanded in a bifurcated vessel.
The proximal portion 31 of the step balloon 3 expands the proximal part 11 of the two-part stent 1 to larger diameter appropriate to the size of the vessel proximal to the bifurcation,

and the distal portion 32 of the step balloon 3 expands the distal part 12 of the two-part stent 1 to smaller diameter appropriate to the size of the vessel distal to the bifurcation.
It may be preferable to overdilate the vessel slightly, as shown in figure 4, because there will be some elastic recovery of the vessel wall and the stent 1 when the balloon 3 is deflated.
After deflating and withdrawing the step balloon 3 the proximal part 11 of the two-part stent 1 will shift into the ostium of the side branch 304 creating an access to the side branch 7.
Figure 5 shows the bifurcated vessel after stenting with the two-part stent 1 of figure 1.
According to the provisional stenting technique, the procedure may be terminated with a kissing balloon inflation and/or by deploying a stent within the sidebranch vessel. A third guidewire is now crossed from within the proximal part 11 of the two-part stent 1 through the non-linked zone 13 at the distal end of the proximal part 11 of the two-part stent 1 into the lumen of the sidebranch vessel. The edges of the expanded stent are designed to facilitate guidewire crossing. After withdrawing the jailed wire, the procedure can be completed with classical kissing balloons technique.
While the present invention has been described herein with respect to the exemplary embodiments and the best mode for practicing the invention, it will be apparent to one of ordinary skill in the art that many modifications, improvements and subcombinations of the various embodiments, adaptations and variations can be made to the invention without departing from the spirit and scope thereof. Although the present invention has been primarily described in relation to angioplasty and stenting of bifurcated blood vessels, the apparatus and methods of the invention can also be used for other applications as well. For example, the catheter system can be used for stenting bifurcated lumens in other organ systems of the body.

CLAIM
1. A stenting system comprising:
a stent delivery catheter having a catheter shaft with a step balloon mounted thereon, the step balloon having a proximal portion and a distal portion, wherein the proximal portion is inflatable to a larger expanded diameter than the distal portion;
a two-part stent having a proximal part that is mounted on the proximal portion of the step balloon and a distal part that is mounted on the distal portion of the step balloon and a non-link zone between the proximal part and the distal part of the two-part stent.
2. The stenting system of claim 1, wherein the proximal part and the distal part of the two-part stent are each configured with stent struts that interdigitate within the non-link zone.
3. The stenting system of claim 1, wherein the proximal portion of the step balloon has a conical configuration.
4. The stenting system of claim 1, wherein the proximal portion of the step balloon has a conical configuration that increases in diameter from a proximal end of the balloon to a distal end of proximal portion.
5. A two-part stent comprising a proximal part and a distal part and a non-link zone between the proximal part and the distal part of the two-part stent, wherein the proximal part and the distal part of the two-part stent are each configured with stent struts that extend like interdigitating fingers into the non-link zone.