TISSUE-REMOVING CATHETHER WITH FLEXIBLE DISTAL TIP

The present disclosure provides a tissue-removing catheter for removing tissue in a body lumen including an elongate drive member, tissue-removing element, and a distal tip. The elongate drive member is sized and shaped to be received in the body lumen. The elongate drive member rotates about an axis. The tissue-removing element is operatively coupled to a distal end portion of the elongate drive member and rotates by the elongate drive member to remove tissue in the body lumen. The distal tip extends distally outward from the tissue-removing element and is more flexible than tissue-removing element. The distal tip has a proximal end portion coupled to the tissue-removing element and a distal end portion spaced distally from the tissue-removing element. The distal tip defines a tip in communication with a liner passage that is configured to receive a guidewire therein.

FIELD

The present disclosure generally relates to a tissue-removing catheter, and more particular, to a tissue-removing catheter including a flexible distal tip.

BACKGROUND

Tissue-removing catheters are used to remove unwanted tissue in body lumens. As an example, atherectomy catheters are used to remove material from a blood vessel to open the blood vessel and improve blood flow through the vessel. This process can be used to prepare lesions within a patient's coronary artery to facilitate percutaneous coronary angioplasty (PTCA) or stent delivery in patients with severely calcified coronary artery lesions. Atherectomy catheters typically employ a rotating element which is used to abrade or otherwise break up the unwanted tissue.

SUMMARY

In one aspect, a tissue-removing catheter for removing tissue in a body lumen generally includes an elongate drive member, tissue-removing element, and a distal tip. The elongate drive member, of the present disclosure, is sized and shaped to be received in the body lumen. Further, the elongate drive member may rotate about a longitudinal axis. The tissue-removing element is operatively coupled to a distal end portion of the elongate drive member. The tissue-removing element rotates by rotation of the elongate drive member to remove tissue in the body lumen. The distal tip extends distally outward from the tissue-removing element and is more flexible than tissue-removing element. The distal tip has a proximal end portion coupled to the tissue-removing element and a distal end portion spaced distally from the tissue-removing element. The distal tip defines a tip opening that extends through the proximal and distal end portions of the distal tip, such that the tip opening is in communication with a liner passage and is configured to receive a guidewire therein.

DETAILED DESCRIPTION

Referring to the drawings, and in particularFIGS.1-2, a tissue-removing catheter for removing tissue T in a body lumen L is generally indicated at reference number10. The illustrated catheter10is a rotational atherectomy device suitable for removing (e.g., abrading, cutting, excising, ablating, etc.) occlusive tissue (e.g., embolic tissue, plaque tissue, atheroma, thrombolytic tissue, stenotic tissue, hyperplastic tissue, neoplastic tissue, etc.) from a vessel wall (e.g., coronary arterial wall, etc.). The catheter10may be used to facilitate percutaneous coronary angioplasty (PTCA) or the subsequent delivery of a stent. Features of the disclosed embodiments may also be suitable for treating chronic total occlusion (CTO) of blood vessels, and stenoses of other body lumens and other hyperplastic and neoplastic conditions in other body lumens, such as the ureter, the biliary duct, respiratory passages, the pancreatic duct, the lymphatic duct, and the like. Neoplastic cell growth will often occur as a result of a tumor surrounding and intruding into a body lumen. Removal of such material can thus be beneficial to maintain patency of the body lumen.

The catheter10is sized for being received in the body lumen L (FIG.2), such as a blood vessel, of a subject. Thus, the catheter10may have a maximum size of 3, 4, 5, 6, 7, 8, 9, 10, or 12 French (1, 1.3, 1.7, 2, 2.3, 2.7, 3, 3.3, or 4 mm) and may have a working length of 20, 30, 40, 60, 80, 100, 120, 150, 180 or 210 cm depending of the body lumen. While the remaining discussion is directed toward a catheter for removing tissue in blood vessels, it will be appreciated that the teachings of the present disclosure also apply to other types of tissue-removing catheters, including, but not limited to, catheters for penetrating and/or removing tissue from a variety of occlusive, stenotic, or hyperplastic material in a variety of body lumens.

Referring to the drawings, and in particularFIGS.1-2, the tissue-removing catheter10for removing tissue T in a body lumen L generally includes an elongate drive member12, a tissue-removing element14, and a flexible distal tip16. As explained in further detail below, the elongate drive member12is sized and shaped to be received in the body lumen L. As shown best inFIG.1, the elongate drive member12includes proximal and distal end portions18,20and a longitudinal axis LA extending between the proximal and distal end portions. The proximal and distal end portions18,20are spaced apart from one another along the longitudinal axis LA. Further, the elongate drive member12is configured to be rotated about the longitudinal axis LA in accordance with one embodiment. As explained in further detail below, the tissue-removing element14is operatively coupled to the distal end portion20of the elongate drive member12. The tissue-removing element14rotates by the elongate drive member12to remove tissue T (e.g., plaque) in the body lumen L. The flexible distal tip16is coupled to (e.g., directly coupled to) and extends distally outward from the tissue-removing element14. The distal tip16is more flexible than tissue-removing element. This increased flexibility of the flexible distal tip16facilitates, for example, centering the tissue-removing element14in a desired lesion that is to be removed within the body lumen L to effectively deliver of the catheter10into the lesion. As best shown inFIGS.2and3, the distal tip16has a proximal end portion coupled to (e.g., directly coupled to) the tissue-removing element14and a distal end portion spaced distally from the tissue-removing element. Further, the distal tip16defines a tip opening that extends along a length of the distal tip and through the proximal and distal end portions of the distal tip, as best shown inFIG.3.

As best shown inFIGS.2and3, the flexible distal tip16includes a coil28. The coil28is configured to be more flexible than the tissue-removing element14and have variable stiffness during a tissue-removing procedure due to the coil tightening and compressing during rotation with the tissue-removing element14. Further, the coil28provides a tapered transition from a guidewire30to the tissue-removing element14, as shown inFIG.2. The purposes of the increased flexibility of the flexible distal tip16in comparison with the tissue-removing element14and the tapered transition is to mitigate risk of lesion hang ups and guidewire damage when the catheter10is guided through the body lumen L. In one or more embodiments, a diamond grit or other abrasive material can be applied to an exterior surface of the coil28, preferably on a portion of the coil that may contact the lesion. It is believed the diamond grit or other abrasive material on the coil28will aid in loosening a portion of the lesion to center the tissue-removing element in the lesion. Alternatively, the exterior surface of the coil28, in particular the portion that may contact the lesion or other tissue to be removed, may be surface etched to form an abrasive surface on the coil. As shown, in one or more embodiments the flexible distal tip16can further include an annular distal cap32secured to the distal end portion of the coil28. The distal cap32may be atraumatic to inhibit injuring the body lumen with the coil28. The distal cap32may also aid in inhibiting unwinding of the coil28within the body lumen while still allowing the guidewire30to pass through the tip opening. The distal cap32may include relatively soft polymeric material that is applied to the distal end portion of the coil and covers the distalmost end of the coil. The polymeric material may adhere turns of the coil to one another. In other embodiments, the distal cap32may be replaced by other means for preventing unwinding of the coil28, such as welding or crimping the coil.

Referring toFIGS.4-6, another embodiment of a catheter10′ includes a different embodiment of a flexible distal tip, generally indicated at reference numeral16′. The other components of the catheter10′ may be identical to the first embodiment other than the distal tip16′, and therefore, the same components of the catheters10,10′ are indicated by the same reference numerals in both embodiments. In the present embodiment, the distal tip16′ includes (e.g., may be formed from) a polymeric material. For example, but not limiting to, the polymeric material may be a biocompatible material such as polyethylene or polyetheretherketone, Generally, the polymeric material may have at least some amorphous material, relatively high molecular weight, include backbone chemistry that allows energy to be stored elastically, or include plasticizers as known in the art, which provide a more flexible material than the tissue-removing element14. The polymeric material forms the distal tip as an integrally formed, one-piece component having an external surface and a wall thickness. In one embodiment, as shown best inFIG.6, the wall thickness of the distal tip16′ may be non-uniform to promote flexing of the distal tip. Change in wall thickness defines an outer diameter of the distal tip16′ which tapers distally toward its distalmost end. The tapering segments of polymeric material provides a tapered transition from the guidewire30to the tissue-removing element14, best shown inFIG.4. The increased flexibility of the flexible distal tip16′ in comparison with the tissue-removing element14and the tapered transition mitigates risk of lesion hang ups and guidewire damage when the catheter10′ is guided through the body lumen. In one or more embodiments, diamond grit or other abrasive material may be applied to an exterior surface of the polymeric distal tip16′, such as on portions of the distal tip that may contact the lesion or other tissue to be removed. The diamond grit of the distal tip16can similarity aid in loosening a portion of the lesion to center the tissue-removing element in the lesion. Alternatively, surface etching on the exterior surface of the distal tip16′, in particular the portion that may contact the lesion or other tissue to be removed, may be surface etched to form an abrasive surface on the distal tip.

In accordance with the present disclosure, the flexible distal tip16,16′ is atraumatic, such that it is designed and constructed to inhibit damaging (e.g. perforating, dissecting, scraping, cutting, etc.) the body lumen L (e.g., vessel) during delivery of the catheter10to the lesion. With reference to the distal tip16including the coil28, the geometry of the coil may be rounded and free from sharp edges that may injure the body lumen. As previously described, the distalmost end of the distal tip16may include the atraumatic cap to further mitigate risk of damaging the body lumen L. Turning to the polymeric distal tip16′, its geometry includes the tapering segments such that it is also free from sharp edges that may injure the body lumen L. Moreover, the polymeric material itself may be relatively soft to inhibit puncturing of the body lumen L.

As shown best inFIGS.3,5and6, in one or more embodiments the catheter10,10′ including the flexible distal tip16,16′ coupled to the tissue-removing element14may include an inner liner38. In one embodiment, the inner liner38extends axially within the elongate drive member12, the tissue-removing-element14, and the distal tip16. A distalmost end of the inner liner38may terminate at the distalmost end of the distal tip16,16′, as best shown inFIG.6, or proximal to the distalmost end of the distal tip, as best shown inFIGS.3and5. In another embodiment, the inner liner38may extend axially within the elongate drive member12, the tissue-removing-element14, but terminate before the distal tip16,16′ such that the inner liner is not received in the distal tip, as shown inFIGS.3and5. The inner liner38is a low friction material to reduce friction imparted on the guidewire30when the guidewire is received in the inner liner. An inner layer of the inner liner38may include a polymeric material, such as polytetrafluoroethylene, perfluoroalkoxy, fluorinated ethylene propylene, and/or combination thereof as the low friction material. In other embodiments, the catheter10,10′ may not include the inner liner38.

As best shown inFIG.4, the elongate drive member12in the illustrated embodiment comprises a drive coil. The elongate drive member12may be another drive member other than the drive coil, such as a drive shaft, a drive lumen, or other type of elongate drive member. As best shown inFIGS.3,5, and7, the elongate drive member12in the illustrated embodiment is disposed around the inner liner38to define a liner passage42. The elongate drive member12and inner liner38extend along the longitudinal axis LA of the catheter10from the proximal end portion18to the distal end portion20, as best shown inFIGS.1and3. An isolation sheath44is disposed around the drive coil of the elongate drive member12, as shown inFIGS.1,2,7, and8. The drive coil and the inner liner38are both configured to translate relative to the isolation sheath44. The isolation sheath44isolates the body lumen L from at least a portion of the drive coil and inner liner38.

As shown inFIG.2, the tissue-removing element14engages and removes tissue T in the body lumen L when centered in the lesion. Any suitable tissue-removing element14for removing tissue T in the body lumen L as it is rotated may be used in one or more embodiments. In the illustrated embodiment, the tissue-removing element14comprises an abrasive burr configured to abrade tissue in the body lumen L when a motor48, as best shown inFIG.1, rotates the abrasive burr. The abrasive burr has an abrasive outer surface formed, for example, by a diamond grit coating, surface etching, or the like. In other embodiments, the tissue-removing element can comprise one or more cutting elements having smooth or serrated cutting edges, a macerator, a thrombectomy wire, etc. In the illustrated embodiment, as best shown inFIGS.3,4, and5, a coupler50couples the tissue-removing element14to a distal end portion of a drive member, such as the elongate drive member12. The coupler50transfers rotation from the drive member to the tissue-removing element14. Together, the coupler50and the tissue-removing element14define an internal cavity56extending axially along the longitudinal axis LA. The coupler50may be formed from metal or other material, and may be welded and/or crimped to the drive coil and the tissue-removing element14. The coupler50may be fixedly coupled to the drive coil12and the tissue-removing element14in other ways. In one or more embodiments, the catheter10,10′ may not include the coupler, but instead, the drive coil12may be fixedly coupled directly to the tissue-removing element14, such as by welding or in other ways.

The illustrated catheter10,10′, best shown inFIGS.3and5, also includes an internal bearing assembly, generally indicated at58, received in the tissue-removing element14and the coupler50. The internal bearing assembly58is configured to facilitate rotation of the tissue-removing element14without damaging the inner liner38. The internal bearing assembly58may include a bushing60through which the inner liner38extends, and one or more bearings62coupled to the tissue-removing element14and/or the coupler50to facilitate rotation about the bushing.

To remove tissue T in the body lumen L of a subject, a practitioner inserts the guidewire30into the body lumen of the subject, to a location distal of the tissue that is to be removed, as best shown inFIG.2. Subsequently, the practitioner inserts the proximal end portion of the guidewire30through a guidewire lumen64of the inner liner38and through a handle66so that the guidewire extends through a proximal port68in the handle, as best shown inFIGS.1,7, and8. With the catheter10,10′ loaded onto the guidewire30, the practitioner advances the catheter along the guidewire until the tissue-removing element14is positioned proximal and adjacent the tissue, as best shown inFIG.2. When the tissue-removing element14is positioned proximal and adjacent the tissue, the practitioner actuates the motor48using an actuator70to rotate the drive coil12and the tissue-removing element. The tissue-removing element14abrades (or otherwise removes) the tissue T in the body lumen L as it rotates. While the tissue-removing element14is rotating, the practitioner may selectively move the drive coil and inner liner38distally along the guidewire30to abrade the tissue and, for example, increase the size of the passage through the body lumen L. The practitioner may also move the drive coil12and inner liner38proximally along the guidewire30, and may repetitively move the components in distal and proximal directions to obtain a back-and-forth motion of the tissue-removing element14across the tissue by sliding an advancer72back and forth within a slot74in the handle66, as best shown inFIGS.1and8. During the abrading process, the inner liner38isolates the guidewire30from the rotating drive coil12and tissue-removing element14to protect the guidewire from being damaged by the rotating components. As such, the inner liner38is configured to withstand the torsional and frictional effects of the rotating drive coil and tissue-removing element14without transferring those effects to the guidewire30. When the practitioner is finished using the catheter10,10′, the catheter can be withdrawn from the body lumen Land unloaded from the guidewire30by sliding the catheter proximally along the guidewire. The guidewire30used for the abrading process may remain in the body lumen L for use in a subsequent procedure.

As various changes could be made in the above apparatuses, systems, and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.