Bifurcation delivery systems and methods

A catheter assembly including a side branch locator that is moveable between a retracted position within a main vessel of a vessel bifurcation, and an extended position wherein a distal end of the side branch locator extends into a branch vessel of the vessel bifurcation. The side branch locator includes a first end fixed relative to a portion of the catheter assembly that remains in the main vessel. A second end of the side branch locator is moveable between the retracted and extended positions. The catheter assembly can include a moveable sheath that holds the side branch locator in the retracted position. The catheter assembly can further include a stent having a lateral branch opening through which the side branch locator extends.

TECHNICAL FIELD

This disclosure generally relates to bifurcation treatment systems and related methods of treating bifurcated lumens in a patient. Preferred arrangements provide for catheter assemblies used to orient the bifurcation treatment system relative to a branch vessel of a vessel bifurcation.

BACKGROUND

Catheters are used with stents and balloon inflatable structures to treat strictures, stenoses, and narrowing in various parts of the body. Various catheter designs have been developed for the dilatation of stenoses and to deliver and deploy stents at treatment sites within the body.

Stents are typically intraluminally placed by a catheter within a vessel or other tubular body organ for treating conditions such as, for example, occlusions, stenoses, aneurysms, dissection, or weakened, diseased, or abnormally dilated vessel or vessel wall, by expanding the vessel or by reinforcing the vessel wall. Stents can improve angioplasty results by preventing elastic recoil and remodeling of the vessel wall, and treating dissections in blood vessel walls caused by balloon angioplasty of coronary arteries.

While conventional stent technology is relatively well developed, stent technologies related to treatment of the region of a vessel bifurcation are still being developed.

SUMMARY OF THE DISCLOSURE

The present disclosure generally relates to a catheter assembly for treatment of a vessel bifurcation. The catheter assembly includes a side branch locator that is moveable between a first position within a main vessel of the vessel bifurcation, and an extended position wherein a distal end of the side branch locator is positioned within a branch vessel of the vessel bifurcation. The side branch locator includes a first end fixed relative to a portion of the catheter assembly that remains in the main vessel. A second end of the side branch locator is moveable between the first position and the extended position.

The side branch locator can be held in the first position using different types of structures and constructions. For example, the catheter assembly can include a sheath that surrounds the side branch locator to hold the side branch locator in the first position. The sheath is moveable between a position surrounding the side branch locator member, and a proximally retracted position wherein a distal end of the sheath is positioned proximally of the locator member.

The catheter assembly can further include a stent positioned around the side branch locator. The stent can include a lateral branch opening in a sidewall of the stent at a location between distal and proximal open ends of the stent. The side branch locator can extend through the lateral branch opening of the stent and into the branch vessel to align the lateral branch opening relative to the branch vessel.

There is no requirement that an arrangement include all features characterized herein to obtain some advantage according to this disclosure.

DETAILED DESCRIPTION

I. General Background

This disclosure relates to bifurcation treatment systems and related methods of treating bifurcations in a patient's body. The term bifurcation means a division location from one unit into two or more units. Generally, two types of bifurcations of a body organ include 1) a main tubular member defining a main lumen and a branch tubular member defining a branch lumen that extends or branches off from the main tubular member, wherein the main and branch lumens are in fluid communication with each other, and 2) a primary or main member defining a primary or main lumen (also referred to as a parent lumen) that splits into first and second branch members defining first and second branch lumens. The term lumen means the cavity or bore of a tubular structure such as a tubular organ (e.g., a blood vessel). The term conduit means a channel (e.g., a pipe or tube) through which something such as a fluid is conveyed. The terms lumen and conduit are used interchangeable throughout this document.

An example bifurcation is a vessel bifurcation that includes a continuous main vessel and a branch vessel, wherein the vessels define a main lumen and a branch lumen, respectively that are in fluid communication with each other. A vessel bifurcation can alternatively include a parent vessel that divides into first and second branch vessels, wherein the vessels define a parent lumen and first and second branch lumens, respectively, which lumens are all in fluid communication with each other. Example applications of the inventive principles disclosed herein include bifurcation treatment systems for use in cardiac, coronary, renal, peripheral vascular, gastrointestinal, pulmonary, urinary, and neurovascular systems.

The example bifurcation treatment systems disclosed herein are useful for aligning features of the bifurcation treatment system relative to a branch vessel of the vessel bifurcation. For example, the example bifurcation treatment systems can be used for alignment of a stent relative to a branch vessel when the stent is positioned in the main vessel of the vessel bifurcation. An example bifurcation treatment system includes a catheter shaft, an inflatable member mounted to the catheter shaft, and a side branch locator positioned on the inflatable member. The example system can also include a sheath. The sheath is moveable relative to the balloon expandable member to enclose and release the distal end of the side branch locator relative to an interior of the sheath.

The example treatment systems can be used with a guidewire that extends within the main vessel to the vessel bifurcation. The catheter shaft of the bifurcation treatment system typically includes a guidewire lumen sized to receive the guidewire. The catheter shaft also includes an inflation lumen adapted to provide inflation fluid to the inflatable member. The guidewire lumen and inflation lumen can extend co-linearly (e.g., side-by-side) or coaxially.

The bifurcation treatment systems disclosed herein can further include a stent. The bifurcation treatment systems can be adapted to position the stent at a bifurcation treatment site. A variety of stents can be used with the bifurcation treatment systems disclosed herein. Examples of such stents can be found in, for example, in U.S. Pat. Nos. 6,210,429 and 6,325,826 to Vardi et al., co-pending U.S. patent application Ser. No. 10/644,550, filed on Aug. 21, 2003, and titled STENT WITH A PROTRUDING BRANCH PORTION FOR BIFURCATED VESSELS, and U.S. Published Patent Application No. 2004/0176837 titled SELF-EXPANDING STENT AND CATHETER ASSEMBLY AND METHOD FOR TREATING BIFURCATIONS, the entire contents of which are incorporated herein by reference. In general, the aforementioned stents include a lateral branch opening located on a sidewall of the stent at a location between distal and proximal open ends of the stent. The lateral branch opening defines a path between an inner lumen of the stent and an area outside of the stent. The stent lateral branch opening is distinct from the cell openings defined between strut structures from which the stent sidewall is constructed. In some stents, the lateral branch opening can be surrounded by expandable structure. The expandable structure can be configured to extend radially into the branch lumen of the bifurcation upon expansion of, for example, an inflatable portion of the bifurcation treatment system. Typically, the stent is expanded after being positioned in the main vessel of the vessel bifurcation with the lateral branch opening aligned with an opening into the branch vessel. Alignment of the lateral branch opening with the opening into the branch vessel includes requires radial and axial alignment. The stent, including the expandable structure surrounding the lateral branch opening, can be expanded with a single expansion or multiple expansions using one or more inflatable balloons.

The stents can alternatively include a branch extension that extends away from a main body of the stent. The branch extension can extend at an angle relative to the main body. The stent can include a slot that extends from a distal end of the main body proximally to an intersection point between the branch extension and the main body of the stent, and from the intersection point to a distal end of the branch extension. The first and second portions are aligned to provide a continuous opening in the stent between the distal end of the branch extension and the distal end of the main body of the stent. The slot permits the stent to advance over the side branch locator when the side branch locator is extended into the branch vessel of the vessel bifurcation.

Typically, the stent is expanded once it is properly positioned in the main vessel with the sidewall opening of the stent or the branch extension of the stent aligned with the branch vessel. The stent can be expanded with a single expansion. Alternatively, multiple expansions can be used to expand the stent. In some embodiments, more than one expandable balloon member can be used to expand the stent.

In general, a wide variety of stents, balloon expandable members, sheaths, guidewires, and branch locator configurations can be used with the bifurcation treatment system embodiments of the present disclosure and should not be limited to any particular design or configuration.

One aspect of the examples disclosed herein relates to the anchoring and resistance to torsion provided by the side branch locator during inflation of the inflatable balloons of the bifurcation delivery system. An inflation balloon in a deflated stated is typically folded over itself to reduce the outer profile of the balloon for purposes of passing through a vessel. Typically, the balloon tends to rotate during inflation of the balloon. The example side branch locators disclosed herein, when positioned at least partially within a branch vessel, help maintain radial alignment of the bifurcation delivery system relative to the branch vessel as the balloon inflates. The locator counters the torque forces applied by the inflating balloon to maintain the relative alignment with the branch vessel. If a side opening of the stent being expanded by the inflation balloon is positioned encircling the side branch locator, the anchoring of the side branch locator will improve alignment of the side opening of the stent with the ostium of the branch vessel.

II. The Example Illustrated in FIGS.1-9

An illustrated view of an example bifurcation treatment system10is shown with reference toFIGS. 1-9.FIG. 1illustrates the system10positioned within a main vessel2adjacent to the ostium of a branch vessel4. The general area of separation of branch vessel4from main vessel2is defined as a vessel bifurcation6. In accordance with an alternative definition, that portion of main vessel2proximal of bifurcation6can be referred to as a parent or first vessel, that portion of main vessel2distal of the bifurcation6can be referred to as a first branch vessel, and the branch vessel4can be referred to as a second branch vessel. The bifurcation delivery system10generally comprises a catheter shaft12, an inflatable balloon14, a sheath16, a side branch locator18, and a guidewire20. The main catheter member can define or include other structure that defines one or more internal lumens for passage of the guidewire20(e.g., a guidewire lumen (not shown)) and for delivery of inflation fluid to the inflatable balloon14.

The inflatable balloon14is positioned at a distal end13of the catheter shaft12(seeFIG. 1A). Inflatable balloon14includes distal and proximal ends22,24and an inflatable body26. The proximal end24of the inflatable balloon14is secured to an inflation lumen15of the catheter shaft12. The distal end22is secured to a guidewire lumen17of the catheter shaft. The guidewire20extends through the guidewire lumen17. The inflation lumen15is used to inflate and deflate the inflatable body26of the inflation lumen. Prior to inflation, the inflatable balloon14is arranged with a plurality of folds26a,26b,26c(seeFIG. 1B) that reduce the outer profile of the bifurcation delivery system10for purposes of passing the bifurcation delivery system through a vessel.

The side branch locator18is mounted to the inflatable body26between the distal and proximal ends22,24. The side branch locator18is shown positioned on an outer surface of the inflatable body26at an axial location between ends22,24. The side branch locator18includes a base30, a radially moveable arm32, and a distal tip34. The base30is secured to the inflatable body26while the moveable arm32and distal tip34are not directly secured to the inflatable body26. The moveable arm32and distal tip34are moveable relative to the inflatable body26. Example types and direction of movement of the moveable arm32and distal tip34are described below.

In the illustrated example, the sheath16is axially moveable relative to the inflatable balloon14. The sheath16can move at least between a first position covering the side branch locator18(seeFIG. 1) and a second position wherein the side branch locator18is released and able to move into an extended position (seeFIG. 2). The sheath16can also be moveable between the second position shown inFIG. 2and the first position shown inFIG. 1to recapture the side branch locator18within the sheath16. When the side branch locator18is released as shown inFIG. 2, the side branch locator18can be used to orient the system10relative to the branch vessel4as will be described in further detail below.

The sheath16can be structured as a continuous elongate tubular member between a distal end28and a proximal end (not shown) positioned outside of the patient. The proximal end of the sheath16can be pushed and pulled to change a position of the distal end28relative to the side branch locator18. The cross-sectional size and shape of the sheath16can vary between the proximal and distal ends. For example, the cross-sectional size of the sheath16can be sized at the distal end28to pass over the inflatable balloon when in a deflated state and the side branch locator18when in a first position (also referred to as a restrained position) as shown inFIG. 1, while other portions of the sheath16proximal of the distal end28have a smaller cross-sectional size.

In alternative examples, the sheath16includes a tubular portion at a distal end and a pull wire connected to the tubular portion that is exposed at a proximal end for axial adjustment of the sheath by the physician. The tubular portion in this example typically has a length greater than a length of the side branch locator18and less than a total length of the sheath16. The tubular portion can alternatively have a length less than a length of the inflatable balloon14and greater than a length of the moveable arm32. A proximal end of the pull wire extends proximally outside of the patient. The guidewire can be pushed and pulled to change a position of the sheath16relative to the side branch locator18.

The inflatable balloon14can have varied shapes and sizes and can be constructed of any suitable material. The inflatable balloon14and all other balloons disclosed herein can be made of any suitable balloon material including compliant and non-compliant materials and combinations thereof. The catheter shaft12and other catheter portions disclosed herein can also comprise any suitable material. Some example materials for the inflatable balloon and catheters disclosed herein include thermoplastic polymers, polyethylene (high density, low density, intermediate density, linear low density), various co-polymers and blends of polyethylene, ionomers, polyesters, polycarbonates, polyamides, poly-vinyl chloride, acrylonitrile-butadiene-styrene copolymers, polyether-polyester copolymers, and polyetherpolyamide copolymers. One suitable material is Surlyn®, a copolymer polyolefin material (DuPont de Nemours, Wilmington, Del.). Still further suitable materials include thermoplastic polymers and thermoset polymeric materials, poly(ethylene terephthalate) (commonly referred to as PET), thermoplastic polyamide, polyphenylene sulfides, polypropylene. Some other example materials include polyurethanes and block copolymers, such as polyamide-polyether block copolymers or amide-tetramethylene glycol copolymers. Additional examples include the PEBAX® (a polyamide/polyether/polyester block copolymer) family of polymers, e.g., PEBAX® 70D, 72D, 2533, 5533, 6333, 7033, or 7233 (available from Elf AtoChem, Philadelphia, Pa.). Other examples include nylons, such as aliphatic nylons, for example, Vestamid L21011F, Nylon 11 (Elf Atochem), Nylon 6 (Allied Signal), Nylon 6/10 (BASF), Nylon 6/12 (Ashley Polymers), or Nylon 12. Additional examples of nylons include aromatic nylons, such as Grivory (EMS) and Nylon MXD-6. Other nylons and/or combinations of nylons can also be used. Still further examples include polybutylene terephthalate (PBT), such as CELANEX® (available from Ticona, Summit, N.J.), polyester/ether block copolymers such as ARNITEL® (available from DSM, Erionspilla, Ind.), e.g., ARNITEL® EM740, aromatic amides such as Trogamid (PA6-3-T, Degussa), and thermoplastic elastomers such as HYTREL® (Dupont de Nemours, Wilmington, Del.). In some embodiments, the PEBAX®, HYTREL®, and ARNITEL® materials have a Shore D hardness of about 45D to about 82D. The balloon materials can be used pure or as blends. For example, a blend may include a PBT and one or more PBT thermoplastic elastomers, such as RITEFLEX® (available from Ticona), ARNITEL®, or HYTREL®, or polyethylene terephthalate (PET) and a thermoplastic elastomer, such as a PBT thermoplastic elastomer. Additional examples of balloon material can be found in U.S. Pat. No. 6,146,356, which is incorporated herein by reference.

The catheter shaft12includes an inflation lumen15(seeFIG. 1A) adapted to supply pressurized inflation fluid to the balloon14for inflation of the balloon14. The inflation lumen can also be used to drain inflation fluid from the balloon14when deflation of the balloon14is required. The balloon14is initially deflated when the bifurcation delivery system10is advanced along the guidewire20to the vessel bifurcation6. After the bifurcation delivery system10has been properly oriented radially and axially relative to the branch vessel4using, for example, the side branch locator18as described below, the inflatable balloon14is expanded from a deflated state (e.g., see deflated state of balloon14shown inFIG. 1B) to an inflated state (e.g., see partially inflated balloon14inFIG. 1A). The balloon14can be used alone or in combination with other inflatable balloons. The balloon14can be inflated sequentially or simultaneously with other balloons. The balloon14can also include additional inflation portions such as a separate inflation lumen that is in fluid communication with a separate balloon portion of the bifurcation delivery system10. The balloon14can also include an inflatable bulge- or blister-type structure that extends radially outward from the body26of the balloon14, such as the alternative inflatable portions disclosed in co-pending U.S. Published Patent Application Nos. 2005/0015108 and 2004/0138737, which applications are incorporated herein by reference.

Referring toFIGS. 1-5, the side branch locator18is shown mounted to an exterior surface of the inflatable balloon14. In an alternative arrangement, the side branch locator18is mounted to the sheath16. In this alternative arrangement, the inflatable balloon runs along a rail structure within the sheath to fix the relative rotated position of the balloon14to the sheath16while permitting axial movement of the sheath16relative to the balloon14. Once the locator18is positioned in the branch vessel4of the vessel bifurcation6, the sheath16can be retracted proximally while holding fixed the rotated position of the balloon14.

The base30of the locator can include a contact surface for mounting to the balloon14(seeFIG. 4). The contact surface is typically shaped to match the shape of an outer surface of that portion of the inflatable balloon14to which the base30is secured. The cross sectional shape and size of the locator18can be the same or change along a length of the locator18between the base30and the distal tip34.FIG. 5Aillustrates the moveable arm32having a circular cross section at a point along the length of arm32between the base30and distal tip34.FIG. 5Billustrates an alternative rectangular cross sectional shape for the moveable arm32.

The cross sectional shape and size of the moveable arm32can vary to alter the amount of flexibility of the moveable arm32, which can be helpful in positioning the locator18within the branch vessel4. The moveable arm32can have different cross-sectional shapes such as rectangular, circular, or oval shapes. The cross-sectional size of the moveable arm can vary depending on the cross sectional shape. In one example of a rectangular cross sectional shape, the moveable arm32has a thickness of about 50 to about 150 micrometers and a width that is about twice the thickness value. The length of the moveable arm can be, for example, about 1 to about 5 mm from the connection point of base30to the distal tip34. The length can be determined based on the diameter of the main vessel and the diameter of the assembly10when the balloon14is deflated.

The base30can also have different shapes and sized. In one example, the base30has a generally rectangular shape with a width of about 200 to 400 micrometers and a thickness of about 50 to about 150 micrometers. The base30can have a contoured surface that matches a contoured shape of the balloon14exterior surface to which the locator18is mounted when the balloon14is inflated.

The illustrated example shows the locator14constructed with a preformed bend angle βR(seeFIG. 3) when the side branch locator is in a rest state. The angle βRis usually defined between the moveable arm32and the contact surface of the base30that faces that portion of the inflatable balloon14to which the locator18is secured. Alternatively, the angle βRis defined between the outer surface of the inflatable balloon14to which the locator is secured and the moveable arm32. The bend angle βRcan be chosen to be substantially the same as an angle α at which the branch vessel4extends from the main vessel2. For example, the angle βRcan be in the range of about 50% to about 150% of the angle α.

The restrained position of the moveable arm32is generally parallel to an outer surface of the balloon body26of the inflatable balloon14.FIG. 1illustrates the moveable arm32in the restrained position. The restrained position can vary depending on, for example, an internal size of the sheath16, the inflated state of the inflatable balloon14, and the flexibility of the sheath material.

The movement of moveable arm32between the restrained orientation shown inFIG. 1and the extended position at the angle βRshown inFIG. 3can occur automatically upon proximal retraction of the sheath16. Automatic movement of the moveable arm32into the extended position can result from, for example, stored potential energy in the locator18. The potential energy can be stored by forcing the locator into a shape different from its rest shape. When the locator is released from the different shape, the locator biases towards the rest shape. The embodiment ofFIGS. 1-3illustrates an example stored potential energy embodiment wherein the sheath16holds the moveable arm32in a restrained position different from the extended rest position shown inFIG. 3. Other example configurations that provide automatic movement of the moveable arm32are described in further detail below.

In some embodiments, movement of the moveable arm32can occur in response to a physical change or stimulus that does not occur automatically upon retraction of the sheath proximally from the locator18. For example, the locator18can comprise a thermal shape memory material that returns to a preformed extended configuration upon heating above a threshold temperature. Example heat sources for heating of the thermal shape memory material include the patient's body and an electrical resistor. A bimetal material is another example material that could have shape memory properties when heated.

In another embodiment, the moveable arm32can move between the restrained and extended position using a current induced pseudo elastic material in the locator18. A current induced material can change shape when stimulated with an electrical current. When a current induced pseudo-elastic material is included in, for example, the moveable arm of the locator18, administering a small current to the pseudo-elastic material of the locator can change the shape of the locator to create movement of the moveable arm between the retained position ofFIG. 1to the extended position ofFIG. 3. A potential benefit of using pseudo-elastic material is that the material can change back and forth between different shapes by changing the amount of current applied. Another potential benefit of using pseudo-elastic material is that it can be used without the sheath16.

The side branch locator can include a thermal shape memory material such as Nitinol (Nickel Titanium Naval Ordnance Laboratory) that provides bimodal actuation. Thermal shape memory material provides for a change in shape of the object that includes the material. The change in shape includes a change from a new shape into an original shape by heating the material above a transition temperature. The transition temperature for thermal shape memory materials such as Flexinol® made by Dynalloy of Costa Mesa, Calif., is about 70° C. The transition temperature of other thermal shape memory materials can be higher or lower depending on the specific material composition. When a thermal shape memory material is cooled, it can be stretched or otherwise formed into a new shape different from the original shape. By including thermal shape memory material in the construction of the side branch locator18, the original shape can be the extended configuration shown inFIG. 3, and the shape maintained when below the transition temperature is the retained configuration shown inFIG. 1. Using a thermal shape memory material can eliminate the need for the sheath16described herein. Alternatively, a thermal shape memory material can be used in combination with the sheath16. A thermal shape memory material can also be used in combination with a fastener or a current induced material.

Some types of thermal shape memory material can be heated to its transition temperature with the body heat of the patient into which the stent delivery system is introduced. Using the body as the heating source, it is possible to estimate a range of time required to reach the transition temperature beginning with introduction of the stent delivery system into the patient. Reducing the initial temperature of the side branch locator before introducing the side branch locator into the patient (e.g., by refrigerating portions of the bifurcation delivery system) can help extend the time period required for reaching the transition temperature after the side branch locator has been introduced into the patient. The thermal shape memory material can also be heated using an electric current or other heat source besides the patient's body.

A sheath16is shown in the Figures as the structure used to hold the side branch locator in the restrained position. In alternative examples, other structure can be used to provide a similar function of holding the locator18in a restrained position. For example, a releasable fastener can be used to hold the locator in the restrained position, whereupon release of the fastener results in the locator18being permitted to move into the extended position.

In the illustrated example, at least some portions of the locator18, such as the distal tip34, preferably include a material that is visible under X-ray or in fluoroscopy procedures. A typical fluoroscopy procedure is operable by differentiating the absorption of X-rays by different material. Body materials such as carbon, oxygen and water typically have low X-ray absorption properties. Materials with high X-ray absorption are sometimes referred to as radiopaque materials. Some example radiopaque materials include gold, platinum, tantalum, and tungsten. Including a radiopaque material in the distal tip34can be particularly useful for tracking a position of the locator relative to the ostium of the branch vessel within a patient. Viewability of the side branch locator features can assist the physician operating the system10in more easily locating the branch vessel4. An alternative to including radiopaque material in the features of locator18is to position radiopaque markers on the locator18. In some embodiments, radiopaque markers can be secured to the distal tip34, along a length of the moveable arm32, to the base30, or at any desired position on the expandable balloon14or catheter shaft12.

An example of markers and marker arrangements for use with the example bifurcation treatment systems disclosed herein are described in U.S. Pat. No. 6,692,483 to Vardi, et al., and co-pending U.S. provisional patent application Ser. No. 60/776,149, filed on Feb. 22, 2006, and titled MARKER ARRANGEMENT FOR BIFURCATION CATHETER, which patent matters are incorporated herein by reference.

Another example side branch locator (not shown) includes more than one moveable arm each having a distinct distal tip34. Alternatively, a single side branch locator with at least two moveable arms can include a common distal tip. In still further examples, multiple side branch locators can be used on with a single bifurcation treatment system, wherein each locator has at least one moveable arm. Each of the moveable arms in these examples can have a different size and shape and be positioned at different locations on the bifurcation treatment system. These and other example side branch locators can be useful for aligning the bifurcation treatment system relative to a branch vessel of a vessel bifurcation.

An exemplary manner of practicing aspects of the example system10and related methods will now be discussed with reference toFIGS. 1-9. First, the guidewire20is advanced within main vessel2to a position wherein a distal end of the guidewire20is positioned distally of the bifurcation6. The catheter shaft12and inflatable balloon14along with the sheath16positioned over the locator18are advanced over the guidewire20into a position adjacent to the bifurcation6(seeFIG. 1). Typically, the distal end28of the sheath16is first positioned distally of the side branch locator18in a first position prior to advancing the system10to the bifurcation6. The sheath16, when in the first position, retains the locator18in a non-deployed state within an interior of the sheath16. The catheter shaft12is then adjusted both axially and radially to position the distal tip34of the side branch locator18distally of the bifurcation6.

Referring now toFIG. 2, the sheath16is then retracted proximally to a position wherein the distal end28is proximal of at least the moveable arm32of the side branch locator18. Retracting the sheath16allows the moveable arm32and distal tip34to extend radially outward from the inflatable balloon14into a deployed state. The moveable arm32extends radially outward either automatically or in response to a stimulus depending on the configuration of the locator18. In the example ofFIGS. 1-6, the locator16is adapted for automatic extension into an extended position upon being released from the sheath16. When the moveable arm32extends away from the inflatable balloon14, as shown inFIG. 2, the distal tip34engages an interior wall of the main vessel2. Because the locator14has been positioned distally beyond the ostium of branch vessel4, the distal tip34engages the sidewall of main vessel2at a location distally of the ostium of branch vessel4(seeFIG. 2). The angle β at which the moveable arm32extends relative to the balloon14when the moveable arm32is in contact with main vessel2is less than a rest angle βR(seeFIG. 3). When the angle β is less than βR, the moveable arm32and distal tip34exert a biasing force radially outward upon the interior wall of the main vessel2.

Referring now toFIG. 3, the locator18is then adjusted axially and radially until the distal tip34moves into the branch vessel4. When the moveable arm32and distal tip34are exerting the radially outward directed biasing force described above, the side branch locator18tends to more actively move into the branch vessel4when the distal tip34is positioned in close proximity to the ostium of branch vessel4.

The axial and radial movement of the catheter shaft12and inflatable balloon14can be done simultaneously or sequentially. In an example of sequential movement, a small axial movement can occur in the proximal direction followed by radial rotation, followed by a repeated sequence of these steps until the branch vessel4is located. In simultaneous movement, axial and radial adjustments are made at the same time until the locator18is positioned in branch vessel4. Further axial movement of the sheath16in the proximal direction can be performed in order to ensure that the moveable arm32remains free from the sheath16when attempting to locate the locator18in the branch vessel4.

In the event the physician is unable to position the distal tip34of the branch locator within the branch vessel4using the sequential or simultaneous movements described above, the sheath can be advanced in the distal direction relative to the inflatable balloon14to recapture the side branch locator18within the sheath16(see the arrangement ofFIG. 1). The capability to reposition the locator18in a restrained position against the balloon14using the sheath16in the illustrated example, provides the physician with the ability to restart the procedure. The procedure is restarted after capturing the locator18within the sheath16by again advancing the bifurcation delivery system10distally to a position where the distal tip34of the locator18is positioned distally of the bifurcation6. After proper repositioning of the locator18relative to the bifurcation6, the sheath is retracted proximally to release the locator18. The locator18can be moved axially and radially as necessary until the distal tip34of the locator is located in the branch vessel4(seeFIGS. 1-3).

In another exemplary method of positioning locator18within the vessel branch4, the guidewire20is advanced within main vessel2to a position wherein a distal end of the guidewire20is positioned distally of the vessel bifurcation6, and the bifurcation delivery system is advanced over the guidewire20to a position where the locator18is positioned near the vessel bifurcation6but proximal of the ostium into branch vessel4. The sheath16is then retracted proximally to permit the locator to move into a deployed state extending radially outward. The system10is then advanced distally and rotated until the locator18is positioned in the branch vessel4.

After the side branch locator18is positioned with the distal tip34advanced into branch vessel4, the bifurcation treatment system10can be used to perform treatment of the bifurcation6. In one example treatment, the sheath16is removed and a stent40is advanced over the catheter shaft12and inflatable balloon14into alignment with the branch vessel4(seeFIG. 6). The stent40includes a main body42having an access slot46, and a branch extension44having an access slot48. The slots46,48together define a continuous open path through which the side branch locator18can pass as the stent40is advanced in the distal direction. Aligning the locator18within the slots46,48typically results in alignment of the branch extension44with the branch vessel4.FIGS. 7-9further illustrate the features of stent40.

The stent40can be adjusted both axially and radially in order to align the side branch locator18within the slots46,48. When the stent40is aligned with the branch vessel4, the inflatable balloon14can be inflated to expand the main body42of the stent40for treatment of the main vessel2. The inflatable balloon14can include additional inflatable portions such as balloons and inflation lumens to expand the stent40and treat the vessel bifurcation6.

Additional inflation members (e.g., inflatable balloons) and expansion members (e.g., stent structures) can be advanced through the branch extension44and into the branch vessel4, wherein the additional inflation and expansion members are used to further treat the branch vessel4. For example, a specially shaped balloon catheter can be advanced through the stent40and into the branch vessel4for use in aligning the branch extension44relative to the side branch4. In another example, the distal tip34of the locator18includes an inflatable balloon that can be inflated after locating the distal tip34within the branch vessel4(e.g., see inflated balloon tip34inFIG. 11).

Alternative bifurcation delivery system embodiments are configured for use with stents that include self-expanding features. Such alternative delivery systems typically do not require the same type of expandable balloons described above for expansion of the stent40. Further, such alternative delivery systems can include side branch locators that are positioned directly on the catheter shaft rather than on an expandable balloon.

Referring now toFIGS. 7-9, the branch portion44of the stent40can be integrally formed as a single piece with main body42. In other embodiments, the branch extension44can be a separate member that is connected to the main body42at a connection point or seam45. The connection point or seam45can include, for example, a weld connection, an adhesive connection, or a fastener connection for securing the branch extension44to the main body42.

III. The Example Illustrated in FIGS.10-11

Referring now toFIGS. 10-11, an example bifurcation delivery system10having an alternative stent240is shown and described. The stent240has a generally tubular, cylindrical shape. A side opening250is defined in a sidewall of the stent between distal and proximal ends241,242of the stent240. The system10is assembled with the locator18positioned on the inflatable balloon14, and the moveable arm32and distal tip34extending through the opening250. The moveable arm32is shown inFIG. 11in a non-deployed state in a generally restrained position maintained by the sheath16. The sheath16is advanced distally over the stent240and locator18until the distal end28of the sheath16is positioned distally of the distal tip34of the locator18. In other configurations, the moveable arm32can be held in the restrained position as a result of the materials used in the locator18rather than being restrained by stent16. For example, the locator18can comprises thermal shape memory material that returns to a preformed extended configuration upon heating above a threshold temperature. Alternatively, the locator18can include a current-induced pseudo elastic material that upon stimulated with a current causes the moveable arm32to move into an extended position.

FIG. 10illustrates the sheath16retracted proximally to permit the moveable arm32to extend radially outward into a deployed state. After the locator18released and extended radially outward, the catheter shaft12and inflatable balloon14can be adjusted axially and radially until the distal tip34of the locator18is positioned in the branch vessel4as shown inFIG. 10.

IV. The Example Illustrated in FIG.12

Referring now toFIG. 12, an example bifurcation delivery system10having an alternative features for the side branch locator18is shown and described. The locator18includes a distal tip34having inflation capabilities. The distal tip34is shown coupled to an inflation lumen31via the base30and moveable arm32of the locator18. Alternatively, the inflation lumen31can extend to the distal tip34independent of the base30and moveable arm32. The inflation lumen31is typically in fluid communication with a source of inflation fluid that can be used to inflate the distal tip34after the distal tip34has been positioned within the branch vessel4. When the distal tip34is inflated sufficiently to engage the internal walls of the branch vessel4, the locator18can align the system10relative to the branch vessel4.

While the example illustrated inFIG. 12does not include a stent, a stent having, for example, the configurations described above with reference to the examples shown inFIGS. 1-12can be used with the inflatable distal tip34.

IV. Summary and Conclusion

One aspect of the present disclosure relates to a catheter assembly that includes a catheter having a distal end, an inflatable balloon member positioned at the distal end of the catheter shaft, and a locator member. The locator member has a first end secured to the inflatable balloon member and a second end that is moveable from a retracted position adjacent to the inflatable balloon member to an extended position spaced apart from the inflatable balloon member.

Another aspect of the present disclosure relates to a medical stent delivery system. The system includes a catheter shaft, a locator member, and a stent. The locator member has a fixed end and a moveable end, and is configured to move between a retracted position and an extended position. The stent includes a lateral branch opening located at a position between distal and proximal open ends of the stent. The second end of the locator member extends through the lateral branch opening.

A further aspect of the present disclosure relates to a method of locating a branch vessel of a vessel bifurcation. The method includes positioning a guidewire in a main vessel of the vessel bifurcation, the guidewire having a distal end positioned distally of the vessel bifurcation. The method also includes advancing a catheter assembly over the guidewire to the vessel bifurcation. The catheter assembly includes a catheter shaft having a distal end portion, an inflatable balloon member extending from the distal end portion of the catheter shaft, and a branch locator. The branch locator has a first end secured to the inflatable balloon member and a second end moveable relative to the inflatable balloon member. The method further includes moving the second end of the branch locator from a retracted position arranged adjacent to the inflatable balloon member to an extended position spaced apart from the inflatable balloon member and extending toward the branch vessel. The method can also include adjusting radial and axial positions of the catheter assembly relative to the branch vessel until the second end of the branch locator extends into the branch vessel.

It is noted that not all of the features characterized herein need to be incorporated within a given arrangement, for the arrangement to include improvements according to the present disclosure.