US20050273150A1

US20050273150A1 - Stent introducer system

Info

Publication number: US20050273150A1
Application number: US11095208
Authority: US
Inventors: Douglas Howell; William Gibbons; Matthew Carter; Victor Clark
Original assignee: Cook Endoscopy
Current assignee: Cook Endoscopy
Priority date: 2004-03-31
Filing date: 2005-03-31
Publication date: 2005-12-08
Also published as: JP2007531599A; US8029555B2; WO2005096994B1; EP1732470A1; EP1732470B1; DE602005021473D1; US20100121426A1; WO2005096994A1; JP4714736B2

Abstract

A stent delivery system for positioning a first and second stent the first and second branch lumens of a bifurcation. The stent delivery system includes stent introducers and a sheath or catheter having a frangible wall. A method of delivering stents to anatomies such as bifurcated ducts or vessels.

Description

RELATED APPLICATIONS

[0001]

This claims the benefit of U.S. Provisional Application Ser. No. 60/558,721, filed Mar. 31, 2004, entitled “Stent Introducer System,” which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

[0002]

This invention generally relates to medical devices, and more particularly to devices for delivering stents to a target anatomy.

BACKGROUND

[0003]

Stents are elongate tubes that are used to prop open occluded or narrowed vessels or body lumens. Among other things, stents are often used to maintain the patency of the biliary tree, or common bile duct. FIG. 1 is a partial, cross-sectional view of a biliary system 2 showing the common bile duct 2 a, the left hepatic duct 2 b, the right hepatic duct 2 c, the gall bladder 2 d, the pancreas 2 e and the duodenum 2 f.
[0004]

Strictures or occlusions that develop in the upper common bile duct and/or the left and right hepatic ducts can interfere with the proper drainage of those ducts. FIG. 2 illustrates a partial cross-sectional view of the biliary system 2 having strictures 3 within the common bile duct 2 a, the left hepatic duct 2 b and the right hepatic duct 2 c. One method of establishing proper drainage through the diseased ducts is to prop open the ducts by placing stents, such as self-expanding biliary stents, within the diseased ducts. Because of the branched configuration of the duct anatomy it is often necessary to place two or more stents in an overlying or side-by-side configuration.
[0005]

However, currently available stent and introducer geometries are such that placement of a first stent often impedes placement of a second stent. FIG. 3 illustrates the problems associated with the prior art method of placing stents in the common bile duct 2 a and the left and right hepatic ducts 2 b, 2 c. That is, placing stent 16 within the common bile duct 2 a and the left hepatic duct 2 b impedes subsequent access to the stricture in the right hepatic duct 2 c. This prevents placement of a stent in the right hepatic duct 2 c.
[0006]

FIG. 3A illustrates one problem encountered in the prior art by placing two stents sequentially. That is, once the first stent is deployed, it impedes insertion of the second introducer 20 used to deploy the second stent. An alternative to sequential deployment of the stents is simultaneous deployment. Simultaneous deployment, however, requires the side-by-side arrangement of two stent introducers within the working channel of an endoscope. Depending on the size of the stents to be placed and the limited size of the working channel of the endoscope, this option may be unworkable.
[0007]

Consequently, there is a need for a self-expanding stent delivery system which overcomes the problems associated with prior art delivery systems. Specifically, there is a need for a self-expanding stent delivery system which allows the physician to sequentially place a first and second stent in the side branches and main lumen of a bifurcation.

SUMMARY OF THE INVENTION

[0008]

Accordingly, it is an object of the present invention to provide a medical device, method, and kit having features that resolve or improvoe on one or more of the above-described drawbacks.
[0009]

The foregoing object is obtained by providing a stent delivery system having a first introducer used to deploy a first stent, and a sheath or catheter used to receive a second introducer, which in turn is used to deploy a second stent. The first introducer and the catheter can be simultaneously deployed, for example, in a staggered configuration, through the working channel of an endoscope. Once the first stent is deployed, the catheter facilitates delivery of the second introducer to the target anatomy. The catheter or sheath can be splittable.
[0010]

In another aspect, wire guides are used to guide the placement of the first introducer, the catheter, and the second introducer.
[0011]

In yet another aspect, the foregoing object is obtained by providing a method of placing at stents in the branches of a bifurcated target anatomy. The method includes placing a first and a second wire guide in a working channel of an endoscope. The first wire guide is inserted into the first branch lumen of the bifurcation. The second wire guide is inserted into the second branch lumen of the bifurcation. A first introducer and splittable catheter can then be advanced over the respective wire guides to the respective target anatomies. Once in place, the first stent can be deployed. A second introducer can then be introduced over the second guide wire, through the splittable catheter and to the proper target anatomy. Once the second introducer is in place, the second stent can be deployed.
[0012]

The method of the invention may further include any of the following steps: disposing the first introducer and the splittable catheter within the working channel of the endoscope such that the first introducer proximal portion is disposed adjacent to the splittable catheter and the first introducer distal portion is disposed distal to the splittable catheter while inside the working channel of the endoscope; deploying the first stent within the first branch lumen and the main lumen of the bifurcation and withdrawing the first introducer from the bifurcation; and/or splitting the splittable catheter and withdrawing the splittable catheter from the bifurcation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013]

FIG. 1 is a partial, cross-sectional view of a biliary system showing the common bile duct, the left hepatic duct, the right hepatic duct, the gall bladder, the pancreas and the duodenum.
[0014]

FIG. 2 is a partial, cross-sectional view of the biliary system of FIG. 1 showing strictures within the common bile duct, the left hepatic duct and the right hepatic duct.
[0015]

FIG. 3 is a partial, cross-sectional view of the biliary system of FIG. 2 illustrating a stent that has been placed in the common bile duct and the left hepatic duct.
[0016]

FIG. 3A is a partial, cross-sectional view of the biliary system of FIG. 1 illustrating a first stent previously placed by a first introducer in the right hepatic duct and the common bile duct that obscures the access of a second introducer attempting to place a second stent in the left hepatic duct and common bile duct.
[0017]

FIG. 4 is a partial, cross-sectional view of the biliary system of FIG. 2 illustrating the placement of first and second stents in the left and right hepatic ducts, respectively, and the common bile duct according to a preferred method of the present invention.
[0018]

FIG. 5 is a partial, cross-sectional view of a preferred embodiment of the stent delivery system of the present invention illustrating a first introducer placed within the right hepatic duct and the common bile duct and a splittable catheter placed in the right hepatic duct and the common bile duct.
[0019]

FIG. 6 is a partial, cross-sectional view of the preferred embodiment of the stent delivery system of FIG. 5 illustrating a first stent deployed in the right hepatic duct and common bile duct after the first introducer has been removed and the splittable catheter placed in the right hepatic duct and the common bile duct.
[0020]

FIG. 7 is a partial, cross-sectional view of the preferred embodiment of the stent delivery system of FIG. 6 illustrating a first stent deployed in the right hepatic duct and common bile duct and the splittable catheter shielding a second introducer as the second introducer is advanced over a second wire guide into the common bile duct and the left hepatic duct.
[0021]

FIG. 8 is a cross-sectional, end view of the stent delivery system of the present invention showing the first introducer and the splittable catheter within the working channel of an endoscope.
[0022]

FIG. 9 is a partial, cross sectional, side-view of a preferred embodiment of the stent delivery system of the present invention showing the first introducer and the splittable catheter within the working channel of an endoscope.
[0023]

FIG. 10 is a cross-sectional view of an embodiment of the first introducer of the stent delivery system of the present invention.
[0024]

FIG. 11 is a partial, cross-sectional view of a distal portion of the first introducer of FIG. 5.
[0025]

FIG. 12 is a partial, cross-sectional view of an alternate embodiment of the distal portion of the first introducer of FIG. 5.
[0026]

FIG. 13 is a partial, cross-sectional view of the distal portion of the first introducer of FIG. 5 showing the wire guide and wire guide lumen.
[0027]

FIG. 14 is a partial, cross-sectional view of the distal portion of the first introducer of FIG. 5 showing an alternate embodiment of the wire guide and the wire guide lumen.
[0028]

FIG. 15 is a partial, cross-sectional view of the distal portion of the first introducer of FIG. 5 showing an alternate embodiment of the wire guide and the wire guide lumen.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029]

Referring now to the Figures wherein like numerals indicate the same element throughout the views, there is shown in FIGS. 1-2 and 4 a bifurcation having a main lumen, a first branch lumen and a second branch lumen. In particular, these figures illustrate a bifurcation in the biliary system, wherein the main lumen comprises the common bile duct 2 a and the first and second branch lumens comprise the left and right hepatic ducts 2 b, 2 c respectively. FIG. 1 shows a normal, or healthy, biliary system without strictures. FIG. 2 shows the biliary system with strictures 3 residing in the main lumen and in both branch lumens of the bifurcation. FIG. 4 shows a pair of stents placed in the left and right hepatic ducts 2 b, 2 c, respectively, and the common bile duct 2 a according to a method of the present invention.
[0030]

Referring now to FIGS. 5-9, a stent delivery system made in accordance with the present disclosure is shown. The stent delivery system includes a first and second introducers configured to deliver two stents to a target anatomy, as well as a catheter used to facilitate delivery of the second introducer to a target anatomy. The first introducer 10 and the splittable catheter 50 are adapted to be disposed within the working channel 8 a of an endoscope 8 as shown in FIGS. 5, 8 and 9. As illustrated in FIG. 7, the splittable catheter 50 includes an interior passageway through which the second introducer can be advanced.
[0031]

As illustrated in FIG. 7, the splittable catheter 50 is an elongate, flexible tube adapted to allow the second introducer 20 to advance unobstructed into the target anatomy. The splittable catheter 50 can be formed from a frangible material, for example, a material that readily tears in a longitudinal direction along the length of the sheath. A non-limiting example of a splittable material is a molecularly oriented (non-isotropic) polytetrafluoroethylene (PTFE) such as that used in the PEEL-AWAY™ Sheath (Cook Incorporated, Bloomington, Ind.). Alternatively, splittable catheter 50 can be formed from any suitable material known in the art including, but not limited to, PTFE, polyamide, polyurethane, polyethylene and nylon including multi-layer or single layer structures. The splittable catheter 50 can also be provided with a groove, pre-score, a weakened area or a pre-slit end to facilitate splitting.
[0032]

Splittable catheter 50 can ranges in size from about 5 Fr. to about 9 Fr. These sizes are provided for illustrative purposes only and are not intended to be construed as a limitation of the present invention. As one of ordinary skill in the art would appreciate in view of the present disclosure, the size of the splittable catheter 50 is related to the size of the second introducer 20 that is advanced through it, which in turn is related to the size of the second stent 26 in its compressed or unexpanded configuration. Thus, splittable catheters smaller than about 5 Fr. that may become available in the future are contemplated as being within the scope of the claims of the invention.
[0033]

With respect to the introducers used with the stent delivery system of the present disclosure, any introducer capable of introducing and deploying stents is contemplated. Non-limiting examples include biliary stent deployment delivery systems as well as the introducers described in co-pending provisional application Ser. No. 10/728,589 (Attorney docket number 10000/218), which is incorporated by reference in its entirety. The introducers can be of the same or different type and size.
[0034]

FIGS. 10-15 illustrate several, non-limiting, exemplary embodiments of introducer 10. In one exemplary embodiment, illustrated in FIG. 10, introducer 10 has a proximal end and a distal end having inner and outer coaxial tubes. The outer coaxial tube forms an outer sheath or catheter 11. The inner coaxial tube forms a shaft 13. Shaft 13 has a proximal end 13 a, a distal end 13 b and a stent retaining area 15. Optionally, shaft 13 may include a pusher band 17 attached to the stent retaining area 15, a distal tip 18 attached to the shaft distal end 13 b and a wire guide lumen 19. Shaft 13 can be made from any suitable material known in the art including, but not limited to, polyethylene ether ketone (PEEK), polytetra-fluoroethylene (PTFE), polyamide, polyurethane, polyethylene and nylon, including multi-layer or single layer structures and may also include reinforcement wires, braid wires, coils and or filaments. Preferably, shaft 13 comprises a proximal portion made of a relatively rigid material such as stainless steel or any other suitable material known in the art.
[0035]

Stent retaining area 15 is preferably located on a distal portion of the shaft 13. The stent retaining area 15 retains a stent 16 to be deployed in the bifurcation. Optionally, stent 16 is a self-expanding stent.
[0036]

Pusher band 17 helps to prevent the stent from proximally migrating as the outer catheter 11 is withdrawn proximally to deploy the stent. The pusher band 17 is located proximal to the stent 16 such that the proximal end of the stent 16 abuts the pusher band 17 as shown in FIGS. 10-15.
[0037]

Distal tip 18 helps prevent fluids from entering the outer catheter 11 as the introducer 10 is navigated through the body lumens. As shown in FIGS. 10-15, distal tip 18 has a proximal end 18 a and a distal end 18 b. The distal tip proximal end 18 a has a diameter that is less than the diameter of the distal outer catheter distal end 14 b and is received therein. Optionally, the distal tip 18 tapers to a smaller diameter towards its distal end 18 b as shown in FIG. 12. Distal tip 18 can be made from any suitable material known in the art including, but not limited to, PEEK, PTFE, polyamide, polyurethane, polyethylene and nylon, including multi-layer or single layer structures.
[0038]

In the embodiment shown in FIGS. 10 and 13, wire guide lumen 19 extends through the shaft 13, from the shaft distal end 13 b to the shaft proximal end 13 a. In this embodiment, the shaft proximal end 13 a optionally includes a luer-lock fitting 31 for releaseably fixing a wire guide 32 relative to shaft 13 as shown in FIG. 10. In the embodiments shown in FIGS. 10 and 13, the stent delivery system 1 of the present invention includes an over-the-wire type wire guide. Such wire guides are known in the art.
[0039]

Alternatively, the wire guide lumen 19 may extend through the shaft 13 from the shaft distal end 13 b to the shaft proximal end 13 a but the wire guide 32 exits through an aperture positioned along the length of the introducer 10. For example, as shown in FIG. 14, the wire guide 32 extends through a portion of the distal tip 18 and exits through an aperture 30 positioned along the length of the distal tip 18. In this embodiment, the wire guide 32 extends through the distal tip 18 and exits the introducer 10 without passing through stent 16. For example, wire guide 32 may extend proximally through distal tip 18 for a distance of about 1 cm.
[0040]

In the alternate embodiment shown in FIG. 15, the wire guide lumen 19 extends through the length of the shaft 13 but the wire guide 32 extends through a portion of the shaft 13 and exits through an aperture 30 positioned along the length of outer catheter 11. In this embodiment, wire guide 32 extends through the distal tip 18, through a portion of the shaft 13 and passes through stent 16 before exiting introducer 10. For example, wire guide 32 may extend through the distal tip 18 and through the stent retaining area 15 for a distance of about 20 cm.
[0041]

In yet other alternative embodiments, the wire guide lumen 19 may extend through a portion of shaft 13 and may exit through an aperture 30 positioned along the length of the introducer 10. Any number of apertures 30 positioned at any location along the length of the introducer 10 is contemplated. In addition, the wire guide lumen 19 may also comprise a channel or split.
[0042]

Aperture 30 provides the stent delivery system of the present invention with rapid-exchange capabilities. In particular, by extending the wire guide 32 through only a distal portion of the wire guide lumen 19, the delivery system can be removed from a wire guide 32 having a length substantially shorter than the length necessary if the wire guide 32 were extended through the entire length of the wire guide lumen 19.
[0043]

Referring to FIG. 10, the sheath or outer catheter 11 has a proximal end 11 a and a distal end 11 b. Preferably, at least the distal portion of outer catheter 11 is made of any optically clear or imageable material. This allows the stent 16 mounted on the stent retaining area 15 of the shaft 13 to be viewed.
[0044]

The outer catheter 11 further includes a proximal outer catheter 12 having proximal and distal ends, 12 a and 12 b, respectively, and a distal outer catheter 14 having proximal and distal ends, 14 a and 14 b, respectively. The distal end 12 b of the proximal outer catheter 12 is attached to the proximal end 14 a of the distal outer catheter 14 to form outer catheter 11. The distal end 12 b of proximal outer catheter 12 can be attached to the proximal end 14 a of distal outer catheter 14 by any method known in the art including, but not limited to, heat fusing, adhesive bonding, chemical bonding or mechanical fitting. Alternatively, the proximal outer catheter 12, and the distal outer catheter 14 can be formed from of a single catheter or sheath.
[0045]

The introducer proximal outer diameter is between about 5 Fr. and about 6 Fr. The first introducer distal outer diameter is between about 6 Fr. and about 6.5 Fr. This allows placement of a stent having a compressed diameter between about 0.077 inches and about 0.78 inches. These sizes are provided for illustrative purposes only and are not intended to be construed as a limitation of the present invention. As one of ordinary skill in the art would appreciate, the size of the introducer required to place a stent is related to the size of the stent to be placed, and more particularly, to the size of the compressed configuration of the stent. Thus, introducers having distal outer diameters less than about 6 Fr. used to place stents having compressed configurations less than about 0.078 inches that may become available in the future are contemplated as being within the scope of the present disclosure.
[0046]

The first introducer 10 and the splittable catheter 50 are sized to be disposed next to each other in the working channel 8 a of an endoscope 8. More particularly, the sum of the first introducer 10 outer diameter, i.e. either the proximal outer diameter or the distal outer diameter, and the splittable catheter outer diameter is less than the inner diameter of the working channel 8 a of the endoscope 8. For example, referring to the embodiment shown in FIG. 9, the first introducer 10 and the splittable catheter 50 are disposed next to each other in a staggered configuration within the working channel 8 a of an endoscope 8. That is, the introducer has an increased diameter portion (the stent retaining area) and a decreased diameter portion (the proximal outer catheter). When the introducer and catheter are positioned in an endoscope adjacent to one another and staggered the respective increased and decreased diameter portions are nested together. As can be seen in FIG. 9, the sum of the first introducer proximal outer diameter and the splittable catheter 50 is less than the inner diameter of the working channel 8 a of the endoscope 8.
[0047]

In yet another alternate embodiment of the stent delivery system 1 of the present invention, the first introducer 10 and the splittable catheter 50 are sized to also accommodate at least one wire guide 32 or 42 within the working channel 8 a of the endoscope 8. For this embodiment, the sum of the first introducer proximal outer diameter, the splittable catheter outer diameter and at least one of the first and second wire guides 32, 42 is less than the inner diameter of the working channel 8 a of the endoscope 8.
[0048]

The stent delivery system 1 of the present invention is used to place first and second stents 16, 26 into a bifurcation having strictures 3 in the main lumen 2 a and the first and second branch lumens 2 b, 2 c as follows. Using an endoscope, a distal end of a first wire guide is advanced into the first branch lumen of the bifurcation. A distal end of a second wire guide is then advanced into the second branch lumen of the bifurcation. The first introducer 10 and the splittable catheter 50 are advanced over the wire guide into the working channel 8 a of the endoscope 8. Thus, the first introducer 10 is positioned within the first branch of the bifurcation and the splittable catheter 50 is positioned within the second branch lumen of the bifurcation, as shown in FIG. 5. The first introducer 10 and splittable catheter 50 may be positioned sequentially or simultaneously. The first introducer 10 is positioned such that the first stent 16 is at least partially aligned within any occlusion of narrowing of the first branch of the bifurcation. Once aligned, the first stent is deployed within the first branch of the bifurcation and the first introducer is withdrawn as shown in FIG. 6. After the first introducer 10 is removed, a second introducer 20 is passed through the working channel 8 a of the endoscope 8 and advanced over the second wire guide 42 through the splittable catheter 50. FIG. 7 shows that the splittable catheter 50 acts as a shield to protect the second introducer 20 from being snagged, or otherwise blocked, by the deployed first stent 16. FIG. 7 also shows the splittable catheter 50 splitting, or peeling away, as the second introducer 20 is advanced through it and into the second branch lumen 26. Once the second introducer 20 is positioned in the second branch lumen 2 b, the splittable catheter 50 is removed and the second stent 26 is deployed within the second branch lumen 2 b and the main lumen 2 a. The resulting connfiguration is shown at FIG. 4.
[0049]

The above Figures and disclosure are intended to be illustrative and not exhaustive. This description will suggest many variations and alternatives to one of ordinary skill in the art. All such variations and alternatives are intended to be encompassed within the scope of the attached claims. Those familiar with the art may recognize other equivalents to the specific embodiments described herein which equivalents are also intended to be encompassed by the attached claims. For example, the invention has been described in the context of the biliary system for illustrative purposes only. Application of the principles of the invention to any other bifurcated lumens or vessels within the body of a patient, including areas within the digestive tract such as the pancreatic system, as well as areas outside the digestive tract such as other vascular systems, by way of non-limiting examples, are within the ordinary skill in the art and are intended to be encompassed within the scope of the attached claims.

Claims

1. A stent delivery system comprising:
a first introducer comprising a first stent;

a second introducer comprising a second stent; and

a catheter having a passageway adapted to receive the second introducer.
2. The stent delivery system of claim 1 wherein the first introducer and the catheter are adapted to be disposed in a partly staggered configuration within the working channel of an endoscope.
3. The stent delivery system of claim 2, wherein the first introducer and the catheter have a combined outside diameter between about 3 mm and 4.5 mm.
4. The stent delivery system of claim 1, wherein the catheter further comprises a side wall having a frangible portion.
5. The stent delivery system of claim 4, wherein the first introducer comprises a distal portion having a stent retaining portion.
6. The stent delivery system of claim 4, wherein the second introducer comprises a distal portion having a stent retaining portion.
7. The stent delivery system of claim 4, wherein a proximal portion of the first introducer is positioned adjacent to the catheter and a distal portion of the first introducer is distal to the catheter when the first introducer and catheter are inside the working channel of the endoscope.
8. The stent delivery system of claim 1 further comprising a first wire guide, wherein the first introducer further comprises a wire guide lumen adapted to receive the first wire guide.
9. The stent delivery system of claim 8, wherein the wire guide lumen extends through at least a distal portion of the first introducer.
10. The stent delivery system of claim 8 further comprising a second wire guide, wherein the second introducer further comprises a second wire guide lumen adapted to receive the second wire guide.
11. The stent delivery system of claim 10, wherein the wire guide lumen of the second introducer extends through at least a distal portion of the second introducer introducer.
12. A kit for delivering first and second stents to a branched target anatomy, the kit comprising:
a first introducer comprising:
a tubular body having a proximal end, a distal end, and a stent carrying portion therebetween;

a second introducer comprising:
a tubular body having a proximal end, a distal end, and a stent carrying portion therebetween;

a catheter adapted to receive the second introducer, the catheter having a frangible wall; and

a sterile package adapted to receive the first introducer, the second introducer and the catheter.
13. The kit of claim 12, further comprising:
a first self-expanding stent positioned within the stent carrying portion of the first introducer; and

a second self-expanding stent positioned within the stent carrying portion of the second introducer.
14. The kit of claim 13, further comprising:
a first wire guide wherein the first wire guide is configured to receive the first introducer; and

a second wire guide wherein the second wire guide is configured to receive the second introducer; and

wherein the sterile package is adapted to receive the first and second wire guides.
15. The kit of claim 12, wherein the first introducer further comprises:
a passageway extending between the distal end and a port positioned proximal to the stent carrying portion, wherein the port is adapted to receive a wire guide.
16. The kit of claim 12, wherein the second introducer further comprises:
a passageway extending between the distal end and a port positioned proximal to the stent carrying portion, wherein the port is adapted to receive a wire guide.
17. The kit of claim 12, wherein the first introducer further comprises:
a passageway extending between the distal end and a port positioned distal to the stent carrying portion, wherein the port is adapted to receive a wire guide.
18. The kit of claim 12, wherein the second introducer further comprises:
a passageway extending between the distal end and a port positioned distal to the stent carrying portion, wherein the port is adapted to receive a wire guide.
19. A method for propping open a narrowed bifurcated anatomy having a main lumen and first and second branch lumens, the method comprising the steps of:
a) providing the kit of claim 19;

b) providing an endoscope having a working channel;

c) positioning the endoscope adjacent the bifurcated anatomy;

d) advancing the first wire guide through the working channel to the first branch lumen;

e) advancing the second wire guide through the working channel to the second branch lumen;

f) advancing the first introducer over the first wire guide to the first branch lumen of the bifurcation;

g) advancing the catheter over the second wire guide to the second branch lumen of the of the bifurcation; and

h) deploying the first stent within the first branch lumen.
20. The method of claim 19, wherein steps f) and g) further comprise advancing the first introducer and the catheter through the working channel in a staggered configuration; and further comprising the steps of:
i) advancing the second introducer over the second wire guide and through the catheter to the second branch lumen;

j) removing the catheter, thereby splitting the frangible wall;

k) deploying the second stent; and

l) withdrawing the second introducer.