System and method for delivering a stent to a bifurcated vessel

A stent delivery catheter system for accurately positioning a stent in a bifurcated vessel is disclosed. The system includes a catheter having a terminal portion and distal tip that is placed in a main branch of the vessel proximate the bifurcation. A fixed guidewire is attached to distal tip. A port is defined in the terminal portion of the catheter. The port is aligned with an ostium of a side branch of the bifurcated vessel to allow the passage of a stent delivery device, such as a balloon catheter having a stent crimped thereon, into the side branch. Radiopaque bands are positioned on opposite ends of the port. A positioning balloon is included on a surface of the catheter opposite the port and is selectively inflatable to position the radiopaque bands adjacent the side branch ostium. The radiopaque bands are referenced to place the stent proximate the side branch ostium.

BACKGROUND

1. Technology Field

The present invention generally relates to intravascular stent systems. In particular, the present invention relates to a stent delivery catheter system that facilitates the accurate positioning of a stent with respect to an ostium of a bifurcated body vessel.

2. The Related Technology

Angioplasty and stent implantation procedures are commonly employed to treat lesions or blockages that form within the vascular anatomy of a patient. During an angioplasty, or percutaneous transluminal coronary angioplasty (“PTCA”) procedure, for instance, a guiding catheter is advanced through the vasculature of the patient to a desired point, such as the ostium of a predetermined coronary artery. A guidewire, positioned within a balloon catheter, is extended from a distal end of the guiding catheter into the patient's coronary artery until it penetrates and crosses a lesion to be dilated. The balloon catheter is then advanced through the guiding catheter and over the previously introduced guidewire, until it is properly positioned across the lesion.

Once properly positioned, the balloon is inflated to a predetermined size such that the stenosis of the lesion is compressed against the arterial wall, thereby expanding the passageway of the artery. The balloon is subsequently deflated, blood flow resumes through the dilated artery, and the balloon catheter is removed.

Occasionally, post-procedure restenosis, or reformation of the arterial blockage, occurs after the PTCA procedure has been performed. Or, a dissection in the blood vessel wall caused by the balloon angioplasty procedure may occur. In addition, elastic recoil and remodeling of the vessel wall after the angioplasty procedure can result. To correct these side effects and strengthen the dilated area, physicians frequently implant an intravascular prosthesis, generally called a stent, inside the artery at the site of the lesion. During a stent implantation procedure, a stent is delivered in a contracted state on a balloon catheter to the desired location within a coronary artery.

Once properly positioned, the stent is expanded to a larger diameter via expansion of the balloon, which causes the stent to expand against the arterial wall at the lesion site. The balloon is then deflated and it and the catheter are withdrawn. The expanded stent remains in place within the artery at the site of the dilated lesion, holding the vessel open and improving the flow of blood therethrough. Stents have been successfully implanted in the z urinary tract, the bile duct, the esophagus and the tracheo-bronchial tree to reinforce those body organs, as well as implanted into the neurovascular, peripheral vascular, coronary, cardiac, and renal systems, among others.

Lesions are often located at or near a point of bifurcation in an artery or other body vessel. When treating such bifurcated lesions, it is common to first place a first guidewire in the main branch, then place a second guidewire, extending from the main branch, into the side branch of the vessel bifurcation. This is so because it is generally important to preserve the side branch and the main branch of the bifurcation.

Specifically, in some instances the above-described dilation via PTCA procedure causes plaque to be shifted from the treated main branch of the vessel bifurcation to the non-treated vessel side branch, thereby occluding the side branch. This effect is known as the “snowplow” effect. Prior placement of the second guidewire in the vessel side branch enables treatment of the side branch should it become occluded due to the snowplow effect.

Treatment of the side branch in this case often includes deployment of a stent therein. The stent is desirably placed in the vessel side branch and deployed so that its proximal end is disposed as close to the ostium, or side branch vessel opening, as possible.

Particularly, it is desired for a stent in a side branch to be positioned axially so as to cover the entirety of the side branch ostium. However, care must also be taken so as to avoid placing the stent such that it “overhangs” beyond the side branch ostium into the lumen of the main branch proximate the ostium. If such overhanging occurs, proper placement of a stent subsequently in the main branch could be compromised undesirably causing, among other things, inhibited blood flow through the stented region. At the same time, placing the stent too far distally into the side branch lumen prevents the stent from adequately covering the ostium, which can make the ostium region susceptible to further degradation or formation of stenoses.

As seen by the above discussion, therefore, it is sometimes necessary in the treatment of lesions at a bifurcated vessel site to deploy a stent in the side branch of the bifurcation. It is paramount, however, to accurately place the stent axially within the side branch so as to avoid the problems described above.

Yet another challenge relating to the placement of a stent relates to the difficulty encountered in maneuvering the stent during its intraluminal transit to the stent deployment site. Particularly, advancement of the stent via the typically tortuous vessel path is made more difficult by the inability to adequately control the rotation of the stent deployment assembly relative to the main branch and side branch of the bifurcated vessel.

In greater detail, during advancement of a catheter along a predisposed guidewire as described earlier, the bifurcation stent deployment assembly, which is coupled with the catheter to support and transport the bifurcation stent in a collapsed state, is not rotatably controlled. Hence, it is often necessary to rotate and reorient a distal portion of the catheter about its longitudinal axis in order to ensure proper alignment of the stent relative to the side branch before its deployment therein.

Unfortunately, transmitting a controlled rotation to the distal end of the catheter over the length of the flexible catheter shaft, however, had traditionally proven difficult. This difficulty is due in part to the complex anatomy of a coronary artery, which results in the flexible catheter shaft being unable to adequately transfer an imposed rotational torque to a distal portion of the catheter shaft where the stent deployment assembly is positioned. Instead, the elongated, flexible catheter shaft merely rotates at the proximal portion when twisted without transmitting the rotational torque distally to the stent deployment assembly in a consistent or satisfactory manner.

Accordingly, there is a need for a stent delivery system with improved alignment and orientation capabilities for aligning a distally positioned stent for deployment within the lumen of a body vessel. More particularly, a need exists for a stent delivery system capable of enabling precise axial and radial positioning of the stent for placement at a vessel bifurcation, for instance, so as to enable the ostium of such a bifurcation to be adequately covered by the stent while preventing undesirable overhang of the stent into proximate areas of the bifurcation.

BRIEF SUMMARY

The present invention has been developed in response to the above and other needs in the art. Briefly summarized, embodiments of the present invention are directed to a stent delivery catheter system for accurately positioning a stent in a bifurcated vessel. Advantageously, the system enables a proximal end of the stent to be positioned proximate the ostium of a side branch of the bifurcated vessel, an operation traditionally difficult to achieve using known systems.

In one embodiment, the system includes a catheter having a terminal portion and distal tip that is placed in a main branch of the vessel proximate the bifurcation. A fixed guidewire is attached to the distal tip. A port is defined in the terminal portion of the catheter. The port is aligned with an ostium of a side branch of the bifurcated vessel to allow the passage of a stent delivery device, such as a balloon catheter having a stent crimped thereon, into the side branch. Radiopaque bands are positioned on opposite ends of the port. A positioning balloon is included on a surface of the catheter opposite the port and is selectively inflatable to position the radiopaque bands adjacent the side branch ostium. The radiopaque bands are referenced to place the stent proximate the side branch ostium.

These and other features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

DETAILED DESCRIPTION OF SELECTED EMBODIMENTS

Reference will now be made to figures wherein like structures will be provided with like reference designations. It is understood that the drawings are diagrammatic and schematic representations of exemplary embodiments of the invention, and are not limiting of the present invention nor are they necessarily drawn to scale.

FIGS. 1A-8Idepict various features of embodiments of the present invention, which is generally directed to a stent delivery catheter system for use in accurately deploying a stent in a bifurcated body vessel, such as a coronary artery, for instance. The stent delivery catheter system as disclosed herein enables the stent to be accurately positioned in a portion of the bifurcated vessel such that the stent is able to perform its intended function without causing complications related to improper placement.

As described herein, the stent delivery catheter system is employed in placing stents within the lumen of a coronary artery. However, this description is exemplary only, and it should be appreciated that embodiments of the present system can be employed for stent placement in a variety of body lumens, including the urinary tract, bile duct, esophagus and tracheo-bronchial tree, neurovascular, peripheral vascular, cardiac, and renal systems, among others. Also, as used herein, the term “stent” is understood to include a device that is intraluminally implanted within bodily vessels to reinforce collapsing, dissected, partially occluded, weakened, diseased or abnormally dilated or small segments of a vessel wall.

Reference is first made toFIGS. 1A-2B, which depict various aspects of a stent delivery catheter system (“system”), generally designated at10, according to one embodiment. The system10includes a catheter12configured for intraluminal passage via a body vessel, and as such is sized for such passage, depending on the particular vessel dimensions. For example, for use in a coronary artery, the catheter has an outside diameter of approximately 1.3 to 1.7 mm, with a range of about 0.5 mm to about 10 mm, and an inside diameter of approximately 0.8 to 1.2 mm, with a range of about 0.4 mm to about 9.9 mm, though these dimensions are merely exemplary. For example, the stenting of non-coronary vessels may require catheter dimensions of a significantly larger magnitude than what would be required for stenting a coronary artery. Though the catheter12is cylindrical, other cross sectional shapes can also define the catheter shape.

The catheter12includes a distal terminal portion14and a distal tip16. The terminal portion14has a peripheral sidewall15. The distal tip16is tapered and includes a fixed guidewire26to assist in tracking the system12intraluminally toward the stent deployment location during use. In one embodiment, the fixed guidewire26extends a distance of approximately 20 to 40 mm from the distal tip16, though this distance can be altered as needed for a particular application.

The terminal portion14of the catheter12includes a positioning balloon18longitudinally attached along the terminal portion. So attached, the positioning balloon18is disposed off-center, i.e., non-concentrically with respect to a longitudinal axis36(FIG. 4) of the system10and is selectively inflatable so as to expand as shown inFIGS. 1B and 2B. When not inflated, the positioning balloon18appears as shown inFIGS. 1A and 2A. In the depicted embodiment, no portion of the positioning balloon18completely encircles the terminal portion14of the catheter12about the longitudinal axis36(FIG. 4) whether inflated or not.

As best seen inFIG. 1B, when expanded the positioning balloon18has a kidney-bean cross sectional shape such that its dimensions in radially extending directions from the catheter12increase from its deflated state. This expansion in volume assists the positioning balloon18in securing the position of the system10within a vessel when used intraluminally, as will be described. Other cross sectional shapes of the positioning balloon18are also possible, as appreciated by one skilled in the art.

A cutout20is included in the terminal portion14of the catheter12so as to define a port22. The cutout20comprises a through surface21extending through the peripheral sidewall15on a first lateral side23of the catheter opposite the point of attachment of the positioning balloon18on a second lateral side25of the catheter. As such, the through surface21defines the port22. The port22defines an outlet from the interior of the catheter12for enabling the delivery of a stent delivery device, such as a balloon catheter, as will be described. The cutout20includes angled end portions and horizontally parallel side portions to define the port22, though other shapes are also possible. In the present embodiment, the port22has a greater length of approximately 1.3 mm, a lesser length of approximately 0.9 mm, a depth from the catheter outer surface of approximately 0.5 mm, and a width of approximately 1.0 to 1.3 mm, though these dimensions can be varied according to catheter dimensions and the size of the stent delivery device to be passed therethrough.

Disposed adjacent the longitudinal ends of the port22are port position indicators, or markers, that indicate the position of the port22within the lumen of a vessel when viewed radiographically. In the present embodiment, the position indicators are implemented as annular, radiopaque (“RO”) bands24that are disposed about the outer surface of the catheter12on either end of the port22. Note that other suitable port position indicators could alternatively be implemented in other embodiments. The RO bands24are composed at least partially of a radiopaque material, including metals such as platinum, gold, and alloys thereof, plastics, polymers, other synthetic materials, etc.

Together withFIGS. 1A-2B, reference is now made toFIGS. 3A-4B, which respectively show radial and axial cross sectional views of the system10, according to one embodiment. In particular, a lumen28of the catheter12is shown bounded by the peripheral sidewall15. The lumen28is sized according to particular need so as to both be able to travel intraluminally to the vessel bifurcation where the stent is to be placed and to enable passage therethrough of a stent delivery device. Again, though the cross sectional shape of the catheter lumen28is round, other shapes could be used according to need. As shown inFIGS. 3A and 3B, the port22communicates with the lumen28and faces outward from the longitudinal axis36of the catheter12in a radial direction denoted by arrow29.

FIGS. 3A and 3Bshow the expansion of a volume30of the positioning balloon18that is achieved when the balloon is inflated in a manner to be described below. Though the inflated and deflated dimensions of the balloon can be varied according to the particular application, they are sufficient to enable intraluminal passage of the catheter12when deflated and securing of the catheter position within the vessel when inflated, as will be discussed further below. In the depicted embodiment, no portion of the expandable means (i.e., the positioning balloon18) extends beyond any portion of the port22in the radial direction29during expansion of the expandable means. Note that the particular shape, length, width, etc., of the balloon18can be modified from what is shown in the accompanying figures while still residing within the scope of the present invention.

FIG. 4Ashows that the fixed guidewire26is indeed affixed to an interior portion of the distal tip16. In one embodiment, the length of portion of the fixed guidewire26extending from the distal tip16is approximately 20 to 40 mm. As its name implies, the fixed guidewire26is employed to assist in guiding the system10to a vessel location, where a stent is to be deployed. In one embodiment, the distal end of the fixed guidewire26is flexible and can include an atraumatic tip that aids in guiding the system10during intraluminal passage. Such atraumatic tips typically include a flexible coil (not shown) disposed about a distal portion of the fixed guidewire, which terminates with a solder ball or other atraumatic feature (not shown) at the tip of the fixed guidewire. The fixed guidewire26is composed of a suitable material, such as stainless steel, NiTiNOL, plastics, polymers, and suitable combinations of these materials, for instance.

Though not used in the presently discussed system configuration,FIG. 4Billustrates another possible configuration for the fixed guidewire26, wherein the distal tip16defines an open end and a hollow interior so as to define a lumen17therethrough that is in communication with the lumen28of the catheter12. In this configuration, the system could be configured such that an additional guidewire (not shown) is passed through the lumen17of the distal tip16and the lumen28of the catheter12to further guide the system10during intraluminal transit. In such a case, the fixed guidewire could be retained or omitted, according to need.

An inflation lumen32is shown disposed within the catheter lumen28and is in fluid communication with a conduit34, which serves as an inlet/outlet for the positioning balloon18. Via the conduit34, the inflation lumen32can supply to or remove from the balloon18a fluid—suitable gas or liquid—useful for inflating/deflating the balloon during system operation. Note that the inflation arrangement shown and described herein, however, is merely exemplary; various other inflation/deflation configurations can be used with the present system. For example, the inflation lumen can be external to the catheter12or integrated with the catheter wall. Also, separate inlet and outlet conduits can be defined with the balloon. In the present embodiment, the inflation lumen is crescent-shaped defined so as to minimize it cross sectional catheter profile. These and other modifications are therefore considered part of the present invention.

Reference is now made toFIGS. 5A-5Hin describing operation of the stent delivery catheter system10in facilitating the accurate placement of a stent at a bifurcated vessel location, such as the vessel40shown inFIG. 5A, including a main branch42and side branch44that branch at a point of bifurcation45. The vessel side branch44defines an opening, or ostium,46at the bifurcation45. Note that the particular size and shape of the vessel branches, bifurcation, and ostium are dependent on the particular type and structure of vessel being stented. As such, the vessel and respective branches shown here are merely exemplary of the broader range of vessel configurations that can benefit from the present invention. By way of example here, the vessel40shown here is a coronary artery.

As shown inFIG. 5A, a first guidewire47is first inserted into the main branch42of the vessel40past the bifurcation45to ensure that the main branch can be accessed and stented, if necessary, after stenting of the side branch is complete. InFIG. 5B, the system10is introduced into the patient and intraluminally advanced through the vasculature until the distal tip16has passed the bifurcation45. Note that the positioning balloon18is deflated during this phase of system advancement through the vasculature.

As shown inFIG. 5B, the terminal portion14of the catheter12can be adjusted until the RO bands24indicate (via remote radiographic imaging or the like) that the port22is aligned with the ostium46of the vessel side branch44. The alignment achieved by the port22is both a radial and an axial, i.e., longitudinal, alignment with the side branch ostium46, so as to enable delivery of a stent delivery device into the vessel side branch44. Note that, because alignment with the vessel side branch ostium46is performed by the system10, radial and axial alignment of the stent delivery device (FIG. 5D) itself is minimized. To assist with alignment of the port22with the side branch ostium46, an additional RO marker (not shown) could be included in a longitudinal direction on a surface of the catheter12opposite the port. This marker could then be radiographically detected (e.g. via fluoroscopy) so as to determined when the port is properly aligned with the ostium.

As shown inFIG. 5C, a second guidewire48is passed through the catheter12and terminal portion14of the system10, exiting the port22and extending into the vessel side branch44. InFIG. 5D, the second guidewire is used to position a stent delivery device, such as a balloon catheter50, having a balloon52with a stent54crimped thereon, into the vessel side branch44. Again, the catheter12and port22are sized and configured to enable the stent-equipped balloon catheter50to pass through the catheter and port22, past the ostium46, and into the vessel side branch44. Because the port22is already aligned radially and axially with the ostium46, passage of the balloon catheter50is readily performed.

Note that placement of the second guidewire48into the vessel side branch44can alternatively be performed before the system10is inserted into the main branch42, if desired, so as to assist in aligning the port22of the system with the side branch ostium46. Also note that the balloon catheter passes through the port22and enters the vessel side branch44at an angle with respect to the longitudinal axis36(FIG. 4) of the catheter12.

As shown inFIG. 5E, once the balloon catheter50has been inserted into the vessel side branch44, the positioning balloon18of the system10is inflated, which causes the terminal portion14of the catheter12to be pressed against the inner wall of the vessel main branch42and the RO bands24to be brought into proximate position with the side branch ostium46. With the RO bands24proximately positioned with respect to the side branch ostium46—in some cases being in proximity so as to touch the ostium—the balloon catheter50can be axially maneuvered within the vessel side branch44, as shown inFIG. 5F, so that a proximal end56of the stent56is positioned in proximity with the ostium46, as desired. Note that the RO bands in one embodiment can be encapsulated, if desired, so as to avoid their directly pressing against a portion of the vessel wall.

Because the vessel side branch ostium46is not readily identifiable radiographically, the RO bands24—which are readily identifiable radiographically and which are placed proximate the ostium—are used to accurately position the stent proximal end56with respect to the ostium. Once positioned as desired, the stent54is deployed by inflating the balloon52of the balloon catheter50within the vessel side branch44, as shown inFIG. 5G.

Upon deployment of the stent54, the balloon catheter50is removed via the port22and catheter12of the system10. The positioning balloon18is then deflated and the system10is removed from the main branch42of the vessel40. The first guidewire47can then be removed or used to position another stent (not shown) in the main branch42.

As can be seen from the above discussion, therefore, the positioning balloon described above serves as one exemplary expandable means for selectively positioning a position indicator, such as an RO band, proximate an ostium of a bifurcated vessel, in connection with deploying a stent therein. Note, however, that the positioning balloon serves as only one example of such a means. Indeed, various other devices, such as a mechanically expandable device, may be acceptably employed as a means for selectively positioning a position indicator in accordance with the principles of the present invention. The present invention should therefore not be limited to any one embodiment.

In addition to the advantages described above, embodiments of the present invention further reduce the risk of snowplow effects as a result of treating the vessel side branch as the system10substantially occupies the entirety of the vessel main branch lumen proximate the bifurcation during the stenting procedure.

Reference is now made toFIGS. 6-7Bin describing use of the present system10to deploy a stent having a contoured proximal end.FIG. 6shows such a contoured stent, generally indicated at120, which is deployable for use with an ostium of a side branch having a curvilinear profile, e.g. a saddle-shaped profile—typical of many side branches of bifurcated vessels.

As shown, the contoured stent120includes a generally cylindrical body122defining a distal end124and a proximal end126. The body122of the stent is composed in the present embodiment of an interlocking lattice of small strand wire composed of a suitable material, such as stainless steel. The interlocking lattice of the stent body22is expandable for deployment within the lumen of a bifurcated vessel side branch, as will be described. Notwithstanding its characterization herein, it is appreciated that the stent body can be configured in other ways from what is described herein while still residing within the scope of the claims.

FIG. 6shows that the proximal end126of the stent120includes an inset portion128. The inset portion128generally defines a parabolic shape that extends toward the distal end124of the stent120a predetermined distance. As such, the inset portion128represents the most distal portion of the proximal end126of the stent120. In greater detail, the outermost portions of the interlocking wire lattice of the stent body122body located at the proximal end126thereof generally define a three-dimensionally contoured profile130. The contoured profile130is configured to at least approximately match the three-dimensionally curvilinear profile of the exemplary ostium of the vessel side branch so as to acceptably cover all portions of the ostium.

Note that the particular contour of the proximal end of the stent can be altered in shape and configuration from what is described herein so as to acceptably match ostiums of other vessels, both bifurcated and non-bifurcated, having other curvilinear shapes. For example, the profile of the stent proximal end in one embodiment can include two or more inset portions to acceptably match a similarly contoured vessel ostium when the stent is deployed in the lumen of the vessel. As such, the presently described embodiments should not be construed to limit the present invention in any manner. Further details regarding the contoured stent120can be found in the U.S. patent application entitled, “STENT HAVING CONTOURED PROXIMAL END,” filed Mar. 8, 2007, (attorney docket no. 17066.33.1), which is incorporated herein by reference in its entirety.

FIG. 7Ashows that, as before, the system10includes a terminal portion14having a catheter lumen138and an inflation lumen142. However, in this embodiment, the catheter lumen138has an oblong cross sectional shape for receiving therein a similarly cross sectionally shaped stent delivery device, such as a balloon catheter150shown inFIG. 7B. In particular, the balloon catheter150includes a guidewire lumen152for guiding the catheter via a guidewire, and an inflation lumen154for selectively inflating a balloon156. The balloon catheter150is oblong-shaped such that when the contoured stent120is crimped about the balloon156as shown inFIG. 7B, it also assumes an oblong cross sectional shape. The cross sectional shape of both the catheter lumen138and balloon catheter150can be varied to have other shapes, as may be appreciated by one skilled in the art. Also, other stent delivery devices, apart from that shown at150inFIG. 7B, can alternatively be used with the system10shown inFIG. 7A.

Note that, as shown inFIG. 7B, the contoured stent120is loaded on to the balloon156of the balloon catheter150such that the inset portion128is disposed at the bottom of the balloon, as seen in the view given inFIG. 7B. This positioning ensures that the stent120is properly oriented with respect to the ostium of the side branch vessel when deployed.

Reference is now made toFIG. 8A-8I. Deployment of the contoured stent in the vessel side branch44according to one embodiment proceeds by first inserting the first and second guidewires47and48into the main branch42and side branch44, respectively (FIG. 8A). The system10is then moved into position such that the port22is aligned with the ostium46of the side branch44(FIG. 8B). The positioning balloon18of the terminal portion is then inflated. The balloon catheter150is advanced on the second guidewire48via the catheter lumen138of the catheter12and terminal portion14in the orientation shown inFIG. 7Buntil it passes through the port22and into side branch44(FIG. 8C).

The balloon catheter150is adjusted distally as in previous embodiments to axially align the proximal end126of the stent120with the ostium46. Note that substantial to complete coverage of the ostium46by the stent proximal end126is possible because of the curvilinear profile defined by the proximal end that matches the curvilinear profile of the ostium. Radial alignment of the inset portion128of the stent proximal end126with a corresponding inset portion118of the curvilinear ostium46is achieved ensured by virtue of the predetermined alignment of both the port22of the system10with the ostium46as well as the orientation of the inset portion of the stent as crimped on the balloon156in the manner shown inFIG. 7B.

Once properly aligned, the contoured stent120is deployed against the walls of the vessel side branch44by inflating the balloon156via the inflation lumen142(FIG. 7B) of the balloon catheter (FIG. 8D). As a result, the contoured stent120is positioned as shown inFIG. 8E. The system10is then withdrawn from the vessel main branch42(FIG. 8F), as is the second guidewire48from the side branch44.

As shown inFIG. 8G, another balloon catheter200is then inserted into the vessel main branch42, having a standard stent220crimped thereon. After proper alignment, the stent220is deployed against the main branch vessel wall proximate the ostium46of the vessel side branch44(FIG. 8H). The balloon catheter200is then withdrawn. As a result the bifurcated vessel is stented such that the ostium46of the vessel side branch44is substantially covered by the contoured stent120without the contoured stent extending into the lumen of the main branch44so as to interfere with placement of the stent220.