Patent Description:
The present disclosure relates to medical instruments and systems for removing and exchanging catheters. More particularly, some embodiments relate to removal of drainage catheters comprising a suture.

<CIT> discloses a sheath-like instrument with a retractable, distal cutting blade which may track over and extract an object, such as a catheter or pacemaker lead, embedded in biological tissue, such as a blood vessel or heart chamber.

<CIT> discloses a device for removing an implanted structure from a body vessel. The device comprises an elongated sheath having a proximal end, a distal end, and a passageway extending therethrough. The sheath is sized such that at least a distal portion of the sheath is receivable in the body vessel, and the passageway is sized such that the implanted structure is receivable therein. A handle is configured for engagement with the sheath proximal end. The handle includes an actuator and a drive mechanism responsive to the actuator. The drive mechanism is operable for selectively translating the input of the actuator into rotary movement and/or axial advancement of the sheath.

<CIT> discloses a device for separating an implanted object, such as a pacemaker lead, from surrounding tissue. The device includes a handle, an elongate inner sheath and a circular cutting blade that extends from the distal end of the sheath upon actuating the handle. The cutting blade is configured to engage the tissue surrounding an implanted lead and cut such tissue in a coring fashion as the surgical device translates along the length of the lead, thereby allowing the lead, as well as any tissue remaining attached to the lead, to enter the device's elongate shaft.

<CIT> discloses a system for removing an implanted catheter comprising a rod containing a rod body and a rod handle, wherein the rod body is substantially straight; and a hollow sheath containing a sheath body and a sheath handle, wherein the sheath body is capable of bending to at least <NUM> degrees, and wherein both the rod handle and the sheath handle are made of a non-slip material.

<CIT> discloses a chordal replacement device having a proximal anchor including a flexible patch and a leaflet attachment device. The flexible patch is affixed to an upper surface of a portion of a flailing leaflet with the leaflet attachment device. The device also includes a distal anchor extending and affixed to a distal attachment site in a ventricle; and a flexible tether coupled to and tensioned between the proximal and distal anchors.

<CIT> describes a tunnelling system that has an elongate tunneling member releasably coupled to a connector incorporating a tunneling connector segment adapted for releasable coupling to the one end of the elongate tunneling member and a catheter connector segment adapted for coupling with the catheter in secured relation therewith.

The invention is related to a catheter exchange system as defined in claim <NUM>. Embodiments of the invention are recited in the dependent claims. The embodiments disclosed herein will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. The drawings depict only typical embodiments, which embodiments will be described with additional specificity and detail in connection with the drawings in which:.

Drainage catheters are used in a variety of medical settings for draining fluids from a patient's body. For example, a patient may suffer an injury or have a medical problem where a bodily tissue retains an excess amount of fluid, such as blood or other bodily serum. If the fluid is not removed further complications in the patient can occur such as rupturing or infection of the tissue. Accordingly, drainage catheters may be placed to remove these fluids from the patient, to either relieve pressure or otherwise reduce fluid build-up.

In some embodiments, drainage catheters may comprise a hub, an elongate catheter tube in fluid communication with the hub, and a distal portion that includes a plurality of drainage bores. The drainage bores may be configured to allow communication of fluid from the patient's body through the elongate catheter tube. Some drainage catheters further include a suture disposed within a portion of the drainage lumen extending along a portion of the length of the catheter. The suture may be attached or secured to the tip of the catheter to facilitate deflecting the catheter tip away from a straight configuration into a curved or pig-tail configuration to anchor the catheter within a patient. For example, the practitioner may insert the catheter tube into a patient's body in a straight configuration, then pull on the suture to form a curved loop at the distal end to anchor the catheter within the patient's body.

To remove the catheter, the suture may be released to allow the catheter to return from a pig-tail configuration to a straight configuration. However, in some instances, the suture may become encrusted, which, in turn, may case the catheter to become stuck in a pig-tail configuration. Removing a catheter while in the pig-tail configuration may cause discomfort and/or injury. Described herein are systems, methods, and devices that may be used to remove a catheter even when a suture has become encrusted.

For example, in some embodiments, a drainage catheter exchange system may comprise a sheath, a cutter, and a locking stylet. The locking stylet may be used to hold the catheter in place while the sheath and cutter are slid along the catheter. The sheath may cover the cutter as the sheath and cutter are advanced along the catheter. The cutter may be advanced out of the sheath to sever the suture. After the suture is severed, the catheter may more readily returned to a straight configuration and may be withdrawn from the patient.

In addition to removing a catheter, embodiments described herein may be used to place a new catheter. In some embodiments, a physician may leave the sheath in the patient after a catheter has been removed, and subsequently use the sheath to insert a new catheter. Thus, the sheath may also serve as an introducer.

Embodiments of the disclosure may be understood by reference to the drawings, wherein like parts are designated by like numerals throughout. It will be readily understood by one of ordinary skill in the art having the benefit of this disclosure that the components of the embodiments, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of various embodiments, as represented in the figures, is not intended to limit the scope of the disclosure, but is merely representative of various embodiments.

Various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure. Many of these features may be used alone and/or in combination with one another.

The phrase "coupled to" is broad enough to refer to any suitable coupling or other form of interaction between two or more entities, including mechanical and fluidic interaction. Thus, two components may be coupled to each other even though they are not in direct contact with each other. The phrases "attached to" and "attached directly to" refer to interaction between two or more entities that are in direct contact with each other and/or are separated from each other only by a fastener of any suitable variety (e.g., mounting hardware or an adhesive). The phrase "fluid communication" is used in its ordinary sense, and is broad enough to refer to arrangements in which a fluid (e.g., a gas or a liquid) can flow from one element to another element when the elements are in fluid communication with each other.

The terms "proximal" and "distal" are opposite directional terms. For example, the distal end of a device or component is the end of the component that is furthest from the practitioner during ordinary use. The proximal end refers to the opposite end, or the end nearest the practitioner during ordinary use. With specific application to a drainage catheter exchange system, the proximal end refers to the end that a physician may handle when inserted in a patient, while the distal end is configured for insertion into a patient when in use.

As used herein, the term "suture" is broad enough to include filaments, tethers, wires, cords, straps, or other elongated flexible members configured to deflect a catheter, or maintain the shape of a catheter, when tension is applied to the suture.

<FIG> is a perspective view of a drainage catheter exchange system <NUM>, according to one embodiment. The illustrated drainage catheter exchange system <NUM> comprises a locking stylet <NUM>, a cutting tool <NUM>, and a sheath <NUM>. In some embodiments, the drainage catheter exchange system <NUM> may also comprise a replacement catheter.

The locking stylet <NUM> selectively couples to a catheter. More specifically, a distal portion of the locking stylet <NUM> is configured to selectively couple to a proximal portion of a catheter. In some embodiments, the locking stylet <NUM> engages the outer diameter of the proximal portion of the catheter. In some embodiments, the locking stylet <NUM> engages the inner diameter of the proximal portion of the catheter. Other locations and types of coupling between the locking stylet <NUM> and a catheter are also within the scope of this disclosure. Furthermore, in some instances, prior to coupling the locking stylet <NUM> to a catheter, a practitioner may cut or otherwise remove a hub from the catheter. In embodiments where the catheter has a proximal hub, removal of the hub may facilitate coupling of the locking stylet <NUM> directly to an elongate tube of the catheter.

The locking stylet <NUM> may assist with catheter movement during a procedure to remove or replace a catheter. With the locking stylet <NUM> coupled to a catheter, a physician may grasp a proximal portion of the locking stylet <NUM> to stabilize or secure the catheter, which may minimize undesired catheter movement (e.g., the catheter being pushed further into a patient by the cutting tool <NUM> and the sheath <NUM>). For example, the locking stylet <NUM> may be used by a physician to secure the placement of the catheter while the cutting tool <NUM> and the sheath <NUM> advance along the catheter. Additionally, after the suture is severed, the locking stylet <NUM> may provide the physician with a grip that extends beyond the sheath <NUM> to remove the catheter without removing the sheath <NUM>, thereby allowing the sheath to be used to introduce a replacement catheter. Further, the locking stylet <NUM> may function as a guide for placing the cutting tool <NUM> and the sheath <NUM> over the catheter.

The cutting tool <NUM> may be configured to sever a suture securing a catheter in a pig-tail configuration. The cutting tool <NUM> may be a cylindrical device that can encompass and slide along the locking stylet <NUM> and the catheter. In some embodiments, the cutting tool <NUM> may be a separate component from the sheath <NUM>. In other embodiments, the cutting tool <NUM> may be integrated into the sheath <NUM>. For example, the sheath <NUM> may have a sharpened edge.

In some embodiments, the sheath <NUM> is placed over the cutting tool <NUM> to provide a guard for the cutting tool <NUM>. The cutting tool <NUM> may be longer than the sheath <NUM> and be able to slide longitudinally relative to the sheath <NUM>, such that the distal portion of the cutting tool <NUM> may be disposed within, or exposed by, the sheath <NUM> based on the position of the cutting tool <NUM> relative to the sheath <NUM>. While the cutting tool <NUM> is within the sheath <NUM>, the sheath <NUM> may minimize or prevent the cutting tool <NUM> from causing trauma to the patient while the cutting tool <NUM> and sheath <NUM> advance along the catheter. For example, the sheath <NUM> may cover the cutting tool <NUM> such that the cutting tool <NUM> does not cut into tissue as the cutting tool <NUM> is advanced over the catheter.

<FIG> is an exploded view of the drainage catheter exchange system <NUM> of <FIG>. The drainage catheter exchange system <NUM> comprises the locking stylet <NUM>, the cutting tool <NUM>, and the sheath <NUM>. The locking stylet <NUM> is configured to be nested in the cutting tool <NUM>, and the cutting tool <NUM> is configured to be nested in the sheath <NUM>. Stated another way, the locking stylet <NUM> may be configured to be disposed within a lumen of the cutting tool <NUM> and the cutting tool <NUM> may be configured to be disposed within a lumen of the sheath <NUM>.

The sheath <NUM> may comprise a handle <NUM> and a shaft <NUM>. In some embodiments, the shaft <NUM> is flexible. The flexibility of the shaft <NUM> may facilitates movement along a catheter even if the catheter is bent or curved. The handle <NUM> provides a grip for a physician to advance or retract the sheath <NUM> along the catheter. In some embodiments, the sheath <NUM> is splittable, to allow the sheath <NUM> to be removed from around a replacement catheter comprising a hub (as further discussed below).

In the illustrated embodiment, the cutting tool <NUM> comprises a cannula with a flexible shaft <NUM> and a cutter <NUM>. The cutting tool <NUM> is configured to surround a catheter. The sheath <NUM> may be positioned around at least a portion of the cutting tool <NUM>. For instance, the sheath <NUM> may cover the cutter <NUM> while the cutting tool <NUM> and the sheath <NUM> are advanced along a catheter to a suture of the catheter. The sheath <NUM> includes an aperture at the distal end of the flexible shaft <NUM>, and at least a portion of the cutting tool <NUM> may be selectively extended through the aperture.

In the illustrated embodiment, the cutter <NUM> is at a distal end of the flexible shaft <NUM>. Again, the cutter <NUM> may selectively transition between a first position in which the cutter <NUM> is within the sheath <NUM> and a second position in which the cutter <NUM> is extended beyond the sheath <NUM>. In some embodiments, the cutter <NUM> comprises a circular cutting blade at the distal end of the cutting tool <NUM>. For example, the circular cutting blade may be a sharpened edge around a circumference of the distal end of the flexible shaft <NUM>. In some embodiments, the cutter <NUM> comprises a series of serrations. In some embodiments, the cutter <NUM> comprises a series of notches, including embodiments wherein each of the notches comprises a blunt distal tip and an angled portion that is sharpened. By blunting the distal tip of the notches, the cutter <NUM> may be configured to avoid cutting the patient when the cutter <NUM> is extended from the sheath <NUM>.

As shown, in some embodiments, the cutter <NUM> may include a handle <NUM>. The handle <NUM> provides a grip for a physician to advance or retract the cutting tool <NUM> along a catheter. Additionally, the physician may use the handle <NUM> to move the cutting tool <NUM> longitudinally in relation to the sheath <NUM> to expose the cutter <NUM> or sheath the cutter <NUM>.

In some embodiments, the cutting tool <NUM> may selectively lock into a position relative to the sheath <NUM>. For example, the cutting tool <NUM> may be locked into a sheathed position where the cutter <NUM> is within the sheath <NUM>. In some embodiments, a physician may exert a deliberate force (e.g., a longitudinal force or a rotational force) to remove the cutting tool <NUM> from a locked position.

In some embodiments, the sheath <NUM> may prevent the cutting tool <NUM> from extending past a target distance. For example, the handle <NUM> of the sheath <NUM> limits the longitudinal position of the handle <NUM> of the cutting tool <NUM>. As the handle <NUM> of the cutting tool <NUM> may not advance through the handle <NUM> of the sheath, the cutter <NUM> is limited in its distance to advance beyond the sheath <NUM>. Thus, the length of the flexible shaft <NUM> of the cutting tool <NUM> in relation to the length of the shaft <NUM> of the sheath <NUM> may determine the distance that the cutter <NUM> may advance beyond the sheath <NUM>.

In some embodiments, the sheath <NUM> may be used to sever a suture of a catheter. For example, a cutting portion may be integrated into the sheath <NUM>. The sheath <NUM> may have a sharpened edge, serrations, or notches with a blunt distal tip and sharpened interior edges. In these embodiments, the cutting tool <NUM> may not be included in the drainage catheter exchange system <NUM>.

Embodiments where the drainage catheter exchange system <NUM> does not include a cutter <NUM>, cutting tool <NUM>, or cutting portion of the sheath <NUM> are also within the scope of this disclosure. Without a cutting mechanism the drainage catheter exchange system <NUM> could still be used to exchange a catheter. The locking stylet <NUM> may be used to secure the old catheter while the sheath <NUM> is placed and to remove the old catheter through the sheath <NUM>. The sheath <NUM> could be left in place and serve as an introducer for a new catheter. Such systems may be used when the suture is released from the hub (such as when the suture is not encrusted) or the sheath <NUM> may be pushed against the suture to displace or break the suture without the use of a cutting portion.

In the illustrated embodiment, the locking stylet <NUM> comprises a shaft <NUM>, a locking mechanism <NUM>, and a handle <NUM>. The locking mechanism <NUM> is at a distal portion of the shaft <NUM>, and the handle <NUM> is at a proximal end of the shaft <NUM>.

The locking mechanism <NUM> couples the distal portion of the shaft <NUM> of the locking stylet <NUM> to a proximal portion of a catheter. For example, a physician may remove a hub of a catheter and use the locking mechanism <NUM> to couple the locking stylet <NUM> to the inner diameter or outer diameter of the catheter. The locking mechanism <NUM> may include one or more of a screw thread, fingers, or barbs.

In the illustrated embodiment, the locking mechanism <NUM> may comprise a screw thread to secure the locking stylet <NUM> to the catheter. The handle <NUM> of the locking stylet <NUM> may be used to apply a rotational force to the locking mechanism <NUM>. The rotational force can cause the screw thread to engage an inner surface of the catheter when the locking mechanism <NUM> is inserted into a proximal opening of the catheter.

The locking stylet <NUM> may be configured to be used on a variety of catheters of different sizes. For example, catheters may range from <NUM> French (Fr) to <NUM> Fr. In some embodiments, the locking stylet <NUM> may be sized for a specific catheter size. In some embodiments, the locking stylet <NUM> could couple to a range of sizes of catheters. For example, the locking mechanism <NUM> in the illustrated embodiment has a conical shape. The conical shape may have a tip with a diameter sized for a <NUM> Fr size catheter and widen to a diameter sized for a <NUM> Fr size catheter, for example.

In some embodiments, the locking stylet <NUM> may include a lumen. The lumen would allow the locking stylet <NUM> to be placed over a guidewire, including a guidewire previously disposed within the catheter.

In some embodiments, the locking stylet <NUM> may not include the handle <NUM>. Without the handle <NUM>, the sheath <NUM> and the cutting tool <NUM> may be placed over the locking stylet <NUM> after the locking stylet <NUM> has been coupled to the catheter. In some embodiments, the locking stylet <NUM> may be tapered on one or both ends.

<FIG> is a detail view of the locking mechanism <NUM> of the locking stylet <NUM> of the drainage catheter exchange system <NUM> of <FIG>. In the illustrated embodiment, the locking mechanism <NUM> comprises a helical thread around a conical tip.

The helical thread is configured to engage an inner surface of a catheter when the conical tip is inserted into a proximal opening of the catheter and rotated. The rotated locking mechanism <NUM> may form a friction fit with the inner surface of the catheter. A physician may rotate the locking stylet <NUM> in an opposite direction (opposite the rotational direction used to couple the locking mechanism <NUM> to the catheter) to release the locking mechanism <NUM> from the catheter. The helical thread may be rounded to prevent tearing the catheter.

In some embodiments, the conical tip can couple to a drainage catheter with a range of sizes. The conical tip tapers out from the vertex of the tip. The conical tip features a diameter that progressively expands as the tip tapers away from the vertex of the tip. Thus, a smaller drainage catheter may be secured with the first and second revolutions of the helical thread, while a larger drainage catheter may be secured with the last several revolutions of the helical thread. For example, a conical tip may be tapered to fit a catheter with a size between <NUM> Fr and <NUM> Fr.

In some embodiments, the conical tip may not be configured to taper to couple to a range of catheter sizes. The conical tip may still comprise a taper, but the tip geometry may be configured to couple to a single catheter size. In such embodiments, the physician selects an appropriate-sized locking stylet <NUM> for the drainage catheter. A kit may include multiple locking stylets to accommodate different-sized catheters.

<FIG> is detail view of a locking mechanism <NUM> of a locking stylet <NUM>, according to a second embodiment. The locking mechanism <NUM> comprises a plurality of barbs <NUM> (which may also be referred to as push-in fingers) to engage an inner surface of the catheter when the locking stylet <NUM> is inserted into a proximal opening of the catheter.

The plurality of barbs <NUM> are positioned around a distal portion of the locking stylet <NUM>. Each of the plurality of barbs <NUM> extends proximally and away from a center of the locking stylet <NUM>. Because the plurality of barbs <NUM> are sloped away from the distal end of the locking stylet <NUM>, the locking mechanism <NUM> may be configured to be inserted into a proximal opening of the catheter without catching on an edge of the catheter.

Each of the plurality of barbs <NUM> is connected to the locking stylet <NUM> along a single edge. Each of the plurality of barbs <NUM> may be able to flex inward toward the center of the locking stylet <NUM>. When the plurality of barbs <NUM> are deflected inward, they may exert an outward spring force.

When the locking mechanism <NUM> is inserted into a proximal opening of the catheter with a longitudinal force, the inner surface of the catheter deflects the plurality of barbs <NUM> inwardly. The plurality of barbs <NUM> may exert an outward spring force, causing the plurality of barbs <NUM> to engage with the inner surface of the catheter. The spring force may secure the locking mechanism <NUM> within the catheter.

The plurality of barbs <NUM> may be formed in a variety of ways. In some embodiments, the plurality of barbs <NUM> may be formed from the distal portion of the locking stylet <NUM>. For example, a portion of the locking stylet <NUM> may be removed to form integrated barbs. In other embodiments, a cap comprising the plurality of barbs <NUM> may be coupled to the distal portion of the locking stylet <NUM>.

In the illustrated embodiment, the diameter of the distal portion of the locking stylet <NUM> is smaller than the diameter of the proximal portion of the locking stylet <NUM>. The smaller diameter of the distal portion provides space for the plurality of barbs <NUM> to flex inwardly toward the center of the locking stylet <NUM>.

In some embodiments, the locking mechanism <NUM> can couple to a drainage catheter with a range of sizes. The plurality of barbs <NUM> may flair out from the center of the locking stylet <NUM>. The outward extension of the plurality of barbs <NUM> may allow the locking mechanism <NUM> to couple to multiple diameters of catheter or may be configured to couple to a specific diameter catheter. In embodiments configured to couple to a variety of catheter sizes, a smaller diameter catheter would cause the plurality of barbs <NUM> to flex inwardly more than a larger diameter catheter; however, the spring force exerted by the plurality of barbs <NUM> on the larger diameter catheter may still be sufficient to couple the locking stylet <NUM> to the catheter.

In some embodiments, the plurality of barbs <NUM> are not configured to deflect to couple to a range of catheter sizes. In these embodiments, the physician selects an appropriate-sized locking stylet <NUM>. A kit may include multiple locking stylets to accommodate different catheter sizes.

<FIG> is detail view of a locking mechanism <NUM> of a locking stylet <NUM>, according to a third embodiment, which is in accordance with the claimed invention. The locking mechanism <NUM> comprises a plurality of barbs (i.e., first set of barbs <NUM> and second set of barbs <NUM>) to engage an inner surface of the catheter when the locking stylet <NUM> is inserted into a proximal opening of the catheter. The barbs <NUM>, <NUM> may also be referred to as push-in fingers.

In the illustrated embodiment, the shaft is hollow and the barbs <NUM>, <NUM> comprise strips cut from the distal portion of the locking stylet <NUM>. The barbs <NUM>, <NUM> are bent outward from the locking stylet <NUM> and remain coupled to the locking stylet <NUM> along one edge. Each of the first set of barbs <NUM> remains attached to the locking stylet <NUM> along an edge of the barb closest to the distal end of the locking stylet <NUM>. Each of the second set of barbs <NUM> remains attached to the locking stylet <NUM> along an edge of the barb closest to the proximal end of the locking stylet <NUM>. The space between the first set of barbs <NUM> and the second set of barbs <NUM> may be left as an open slot <NUM>.

The first set of barbs <NUM> is positioned around the distal portion of the locking stylet <NUM> nearer the distal end than the second set of barbs <NUM>. Each barb of the first set of barbs <NUM> extends proximally and away from a center of the locking stylet <NUM>. Because the first set of barbs <NUM> is sloped away from the distal end of the locking stylet <NUM>, the locking mechanism <NUM> may be inserted into a proximal opening of the catheter without catching on an edge of the catheter.

Each barb of the first set of barbs <NUM> is connected to the locking stylet <NUM> along a single edge. Each of the plurality of barbs <NUM> may be able to flex inward toward the center of the locking stylet <NUM>. When the plurality of barbs <NUM> are deflected inward, they may exert an outward spring force.

When the locking mechanism <NUM> is inserted into a proximal opening of the catheter with a longitudinal force, the inner surface of the catheter deflects the first set of barbs <NUM> inwardly. The first set of barbs <NUM> may exert an outward spring force, causing the first set of barbs <NUM> to engage with the inner surface of the catheter. The spring force may secure the locking mechanism <NUM> within the catheter.

The second set of barbs <NUM> is positioned around a distal portion of the locking stylet <NUM> nearer the proximal end than the first set of barbs <NUM>. Each barb of the second set of barbs <NUM> extends distally and away from a center of the locking stylet <NUM>. Because the second set of barbs <NUM> is sloped away from the proximal end of the locking stylet <NUM>, the locking mechanism <NUM> may be used to secure an elongate cover to the locking stylet <NUM> as illustrated in <FIG>. Additionally or alternatively, the locking mechanism <NUM> can stop advancement of the catheter over the locking stylet <NUM>.

<FIG> is a perspective view of the locking stylet <NUM> of <FIG> with an elongate cover <NUM>, according to one embodiment. The elongate cover <NUM> may comprise an extruded member and may be secured in place via a set of barbs as shown in <FIG>. The elongate cover <NUM> may be flexible and surround a shaft of the locking stylet <NUM>.

The locking stylet <NUM> may include a tapered proximal portion <NUM>. As shown, the locking stylet <NUM> may not include a handle. Instead, in some embodiments, the locking stylet <NUM> may be tapered on one or both ends (e.g., tapered proximal portion <NUM>). The tapered proximal portion <NUM> may allow the locking stylet <NUM> to be easily inserted into a sheath even if the locking stylet <NUM> is already secured to a catheter.

<FIG> is a side view of a cutting tool <NUM> of the drainage catheter exchange system <NUM> of <FIG>. The cutting tool <NUM> includes a hollow cannula with a cutter <NUM> on a distal edge.

The the cutting tool <NUM> may be a hollow cannula and may comprise an single integral piece, such as a integral metal cannula. In the illustrated embodiment, the cutter <NUM> is a sharpened distal edge of a hollow cannula. In other embodiments, the cutter <NUM> may be separate from the cannula. For example, the cutter <NUM> may be embedded, glued, or otherwise coupled to the distal edge of the cannula.

In some embodiments, the cutting tool <NUM> includes one or more laser cut spirals along the hollow cannula. Spiral cuts, or other features may be disposed along the cutting tool <NUM> to increase the flexibility of the cutting tool <NUM> to traverse along a catheter and follow the path of the catheter. In some embodiments, one or more spiral cuts on the cutting tool <NUM> may have equal distance between rotations. In some embodiments, one or more spiral cuts along the cutting tool <NUM> may vary in pitch or density. In other words, the distance between rotations of one or more spiral cuts may vary across the length of the cutting tool <NUM>. Variation in spiral cut density provides the cutting tool <NUM> with a flexibility profile that varies along a length of the cutting tool <NUM>.

In the illustrated embodiment, the cutting tool <NUM> features two flexible sections (i.e., distal flexible section <NUM> and proximal flexible section <NUM>). The distal flexible section <NUM> includes more rotations per length of the spiral cut than the proximal flexible section <NUM>. The closer spiral cuts of the distal flexible section <NUM> may have a higher pitch than the further apart spiral cuts of the proximal flexible section <NUM>. The greater density of the spiral cut along the distal flexible section <NUM> provides the distal flexible section <NUM> with a greater flexibility than the proximal flexible section <NUM>. The greater flexibility of the distal flexible section <NUM> allows the tip of the cutting tool <NUM> to track the path of the catheter more readily. The distal flexible section <NUM> may be configured to track the catheter around a tight radius and may be configured to transition and lead proximal flexible section <NUM> over such a path. In other words, the distal flexible section <NUM> can guide the proximal flexible section <NUM> around such tight turns. After the distal flexible section <NUM> follows a radius the rest of the cannula will follow even if the rest of cannula may distort that radius (or tend to straighten the catheter). Further, the cutting tool <NUM> may be configured such that the distal flexible section <NUM> is configured to be disposed over more tortuous curvature than other portions of the cutting tool <NUM>.

In the illustrated embodiment, the distal flexible section <NUM> features a first spiral cut and the proximal flexible section <NUM> features a second spiral cut. The first spiral cut has a pitch in the opposite direction of the second spiral cut. In some embodiments, the two spiral cuts are joined. In other embodiments, the spiral cuts are discrete. In some embodiments, the pitch of the spiral cuts may be in the same direction.

In some embodiments, the one or more spiral cuts may be cut uniformly to create a flexibility profile of the cutting tool <NUM> with the same flexibility throughout.

In some embodiments, the cutting tool <NUM> may feature three or more sections with varying flexibility.

In some embodiments, the density of the one or more spiral cuts may gradually change from one end of the cutting tool <NUM> to another end of the cutting tool <NUM>. For example, the spiral cut may be dense at a distal portion of the cutting tool and gradually the rotations of the cutting tool <NUM> may widen as the spiral cut approaches a proximal portion of the cutting tool <NUM>.

<FIG> is a cross-sectional view of a distal portion of the cutter <NUM> of <FIG>. As shown, the cutter <NUM> includes a first bevel <NUM> extending from the outer diameter of the cutting tool sidewall to the inner diameter of the cutting tool sidewall, and a second bevel <NUM> extending from the inner diameter of the cutting tool sidewall to the outer diameter of the cutting tool sidewall. The angles shown on <FIG> are exemplary and may be changed to any suitable angle. The first bevel <NUM> and the second bevel <NUM> meet at a vertex that forms the sharpened edge of the cutter <NUM>. The vertex is in between the outer diameter of the cutting tool sidewall and the inner diameter of the cutting tool sidewall to avoid damaging a sheath outside of the cutter <NUM> or a catheter inside the cutter <NUM>. In other words, the first bevel <NUM> may displace the cutting edge away from an outer sheath and the second bevel <NUM> may displace the cutting edge away from the catheter, to reduce or avoid skiving of the catheter and the cutter <NUM> is advanced along the catheter.

<FIG> and <FIG> illustrate the drainage catheter exchange system <NUM> of <FIG> in use. Specifically, <FIG> is a schematic representation of the drainage catheter exchange system <NUM> of <FIG> being inserted into a patient to remove a drainage catheter <NUM>. <FIG> is a schematic representation of the drainage catheter exchange system <NUM> of <FIG> severing a suture <NUM> of the drainage catheter <NUM>. The drainage catheter exchange system <NUM> may facilitate removal of the drainage catheter <NUM> even when the suture <NUM> has become encrusted.

As shown in <FIG>, in some procedures, the sheath <NUM> and the cutting tool <NUM> are inserted into a patient over a previously placed drainage catheter <NUM>. To prevent the drainage catheter <NUM> from moving as the sheath <NUM> and the cutting tool <NUM> move along the drainage catheter <NUM>, the locking stylet <NUM> may couple to the proximal end of the drainage catheter <NUM>. A physician may hold onto a shaft of the drainage catheter <NUM> or a handle of the drainage catheter <NUM> to limit movement of the drainage catheter <NUM>. In some instances, practitioner may cut or otherwise remove a hub from the drainage catheter <NUM> to facilitate advancing the sheath <NUM> over the drainage catheter <NUM> and to facilitate coupling of the locking stylet <NUM> to the drainage catheter.

The physician advances the sheath <NUM> and the cutting tool <NUM> along the drainage catheter <NUM> to near the suture <NUM>. The physician may apply a longitudinal force to the handle <NUM> of the sheath <NUM> and the handle <NUM> of the cutting tool <NUM> to advance the sheath <NUM> and the cutting tool <NUM>. The physician may track the position of the sheath <NUM> and the cutting tool <NUM> relative to the suture <NUM> using fluoroscopy, ultrasound, or measurement.

As shown in <FIG>, the cutting tool <NUM> may be advanced from the sheath <NUM> to sever the suture <NUM>. The physician may withdraw the drainage catheter <NUM> by pulling the locking stylet <NUM> away from the sheath <NUM> and the handle <NUM>. The physician may also remove the cutting tool <NUM> and leave the sheath <NUM> in the patient to serve as an introducer for a new drainage catheter. In some embodiments, the sheath <NUM> is splittable, so that once the new drainage catheter is in place, the physician may split the sheath <NUM> to remove it from the patient if the new drainage catheter comprises a hub.

<FIG> is a flow chart of a method <NUM> for removing a catheter using a drainage catheter exchange system. The method includes coupling <NUM> the catheter to a stylet. The stylet includes a shaft and a locking mechanism at a distal portion of the shaft. The locking mechanism may be any of the locking mechanisms described herein or any other suitable securement means. To couple <NUM> the catheter and the stylet, a physician may remove a hub of the catheter and couple the locking mechanism to the distal portion of the shaft to a proximal portion of a catheter. The physician may secure <NUM> the position of the catheter via the shaft of the stylet by holding the stylet in place. The physician may advance <NUM> a sheath along a length of the catheter and sever <NUM> a suture on a distal portion of the catheter. The physician may remove <NUM> the catheter through the sheath by pulling on the locking stylet.

In some embodiments, severing <NUM> the suture comprises applying a force to the suture via the sheath.

In some embodiments, severing <NUM> the suture comprises extending a cutting tool beyond the sheath.

In some embodiments, the method may further comprise placing a new catheter through the sheath, and removing the sheath and the cutter. The sheath may be removed by splitting the sheath away from a hub of the new catheter.

Any methods disclosed herein include one or more steps or actions for performing the described method. The method steps and/or actions may be interchanged with one another. In other words, unless a specific order of steps or actions is required for proper operation of the embodiment, the order and/or use of specific steps and/or actions may be modified. Moreover, sub-routines or only a portion of a method described herein may be a separate method within the scope of this disclosure. Stated otherwise, some methods may include only a portion of the steps described in a more detailed method.

Similarly, it should be appreciated by one of skill in the art with the benefit of this disclosure that in the above description of embodiments, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure. This method of disclosure, however, is not to be interpreted as reflecting an intention that any claim requires more features than those expressly recited in that claim.

Claim 1:
A catheter exchange system (<NUM>) comprising:
a cannula, the cannula comprising a flexible shaft (<NUM>) and a cutter (<NUM>) at a distal end of the flexible shaft; and
a sheath (<NUM>) positioned around at least a portion of the cannula;
wherein the cutter (<NUM>) may selectively transition between a first position in which the cutter is within the sheath and a second position in which the cutter is extended beyond the sheath, characterised in that the system (<NUM>) further comprises
a stylet (<NUM>) comprising:
a shaft, and
a locking mechanism (<NUM>) at a distal portion of the shaft;
wherein the locking mechanism comprises one or more barbs (<NUM>, <NUM>) formed in a wall of the shaft;
wherein the one or more barbs are biased outward from the shaft;
wherein the locking mechanism is configured to couple the distal portion of the shaft to a proximal portion of a catheter;
wherein the one or more barbs includes a first set of barbs (<NUM>) and a second set of barbs (<NUM>);
wherein the first set of barbs are oriented distally and the second set of barbs are oriented proximally;
wherein each of the first set of barbs (<NUM>) is configured to remain attached to the stylet along an edge of the barb closest to the distal end of the stylet, and
wherein each of the second set of barbs (<NUM>) is configured to remain attached to the stylet along an edge of the barb closest to the proximal end of the stylet.