Tissue separating systems and methods

Abstract

Systems and methods for separating an object such as a pacing lead from a patient tissue involve a flexible and torqueable shaft having an internal lumen sized to receive the object, and a hard separating mechanism for separating the object from the tissue. Typically the shaft and separating mechanism are advanced along or toward the object, and the separating mechanism is contacted with the tissue. The shaft is rotated to effect separation between the object and the tissue. The systems and methods are well suited for use in cardiac pacing or defibrillator lead explant procedures.

Description

BACKGROUND OF THE INVENTION

The present application relates generally to systems and methods for separating tissue in a patient, and more specifically, to techniques for separating pacing leads from a patient.

Cardiac pacing systems typically include a pacemaker and a pacing lead, which are placed inside the body of a patient. The pacemaker includes a power source and circuitry configured to send timed electrical pulses to the pacing lead. The pacing lead carries the electrical pulse to the heart to initiate a heartbeat, and transmits information about the heart's electrical activity to the pacemaker. The pacing lead can include a fixation mechanism that holds the lead to the cardiac tissue. In some cases, a pacing lead is inserted through a vein and guided into a heart chamber where it is attached with the heart. In other instances, a pacing lead is attached to the outside of the heart. A common problem associated with pacing leads is the development of scar tissue or adhesions where the pacing lead contacts the patient's body tissue. Patient tissue can become attached with the pacing lead, and thus removal or extraction of the pacing lead may present complications.

Current pacing lead extraction techniques include mechanical traction, mechanical devices, and laser devices. Mechanical traction is often accomplished by inserting a locking stylet into the lead and pulling to remove it. In some cases, for example where mechanical traction is ineffective, dilating telescopic sheaths can be used to strip away the scar tissue adhering the lead to the body. Unfortunately, metal sheaths that are currently used to strip scar tissue from implanted leads often cannot traverse the tortuous lead path, and in many instances can only be used in proximal locations. Currently used plastic sheaths may be able to access certain distal lead locations, but often suffer from poor torque properties, low radiopacity, and ineffective penetration into hard tissue because they have soft tips that deform when in contact with the hard tissue. Dilation techniques often involve pushing tissue away from the lead when the sheath is pushed longitudinally along the lead. However, longitudinal forces can be easily lost during the procedure by tortuousity or curvature in the lead and by friction encountered within the anatomy or over the pacing lead. Longitudinal forces also may require heavy counter traction on the lead-that can result in pacing lead breakage. Some mechanical sheaths have proposed trigger mechanisms for extending a blade from a sheath. At least some of these devices, however, involve complicated activation mechanisms and may not be well suited for negotiating the tortuous paths that exist in certain vascular or physiological environments. Laser devices typically employ laser energy to cut the scar tissue away from the lead thus allowing for removal. Although effective in some circumstances for removing chronic implanted pacing leads, many laser systems can be expensive and unaffordable to many treatment centers.

What is needed are improved mechanical devices and methods for extracting pacing leads as well as other objects. These techniques can provide effective alternatives to currently used dilating lead extraction sheaths and laser systems.

BRIEF SUMMARY OF THE INVENTION

Advantageously, embodiments of the present invention encompass separating devices having improved separating surfaces and shapes that are well suited for freeing pacing leads from adherent scar tissue. For example, a separating tip or element can provide a bevel or angle to enhance contact between a separating tip blade and the patient tissue during rotation of the tip. In some cases, a separating tip provides a separating surface that can be lightly forced against a tissue without separating the tissue, and that can separate the tissue when pressed more forcefully against the tissue or when rotated relative to the tissue. Separating systems can be configured to extract pacing leads primarily by torque. An exemplary separating system involves a torqueable and flexible polymer sheath with a durable, radiopaque tip section that includes hard plastic or metal. The shaft can be composed of a braided composite construction to provide flexibility along with a 1:1 torque response. The system may also include a handle to allow for improved rotation capabilities. When the sheath is rotated, a cutting tip can strip, dilate, or cut adhered tissue from the lead in an axial manner. The configurations provided herein allow pacing lead extraction under reduced force, thereby minimizing the incidence of lead breakage and protecting the safety of the patient. By combining such torque characteristics with distal surface cutting edges, it is possible to effectively penetrate resistant scar tissue when necessary, while maintaining a safe, non-separating profile when the sheath is advanced longitudinally over a pacing lead.

Many of the embodiments described herein refer to cutting elements, cutting assemblies, cutters, and the like, which often include items for cutting tissue, however it is understood that these cutting features can be replaced with or referred to as stripping or dilating elements, stripping or dilating assemblies, or strippers or dilators. Similarly, these cutting features may be referred to as separating elements, separating assemblies, or separators. Stripping features can include items for stripping tissue from pacing leads and other objects within the body of a patient. Relatedly, dilating features can include items for dilating tissue surrounding or near pacing leads and other objects within the body of a patient. Cutting features or procedures can be used or referred to interchangeably with stripping features or procedures, and with dilating features or procedures. Methods that include stripping or dilating tissue may or may not include cutting tissue. In some embodiments, cutting, stripping, or dilating elements or procedures, or any combinations thereof, may be referred to as separating elements or procedures. For example, a separator may refer to or encompass a cutter, a stripper, or a dilator, or any combination thereof. The separating devices, sheath configurations, and other systems and methods described herein are well suited for use with retractable lead extraction techniques disclosed in previously incorporated U.S. patent application Ser. No. 11/605,006, filed Dec. 22, 2006 (Retractable Separating Systems and Methods). Such separating and retractable extraction devices can be used in conjunction with lead locking devices in an explant procedure. In an exemplary method, a lead is disconnected from a pacemaker, and a lead locking device is inserted into or coupled with the lead. A separating or retractable extraction system can be placed over the lead and the lead locking device, and advanced distally so as to separate tissue that is attached with or surrounding the lead. Lead locking devices are often useful in providing traction with a pacing or defibrillator lead without breaking or damaging the lead.

In a first aspect, embodiments of the present invention provide a system for separating an object from a patient tissue. The system can include a sheath having a proximal end and a distal end. The system can also include a cylindrical separator coupled with the distal end of the sheath. The separator can have an internal lumen, a proximal end, and a distal end having a separating mechanism. The separating mechanism can include an abrasive material. In some cases, the abrasive material includes diamond, aluminum carbide, silica carbide, or the like. The distal end of the separator can define a plane, and the internal lumen of the separator can define a central longitudinal axis. An acute angle between the plane and the central longitudinal axis can be within a range from about 10 degrees to about 65 degrees or from about 30 degrees to about 85 degrees. The separator may include a cutting member, a dilating member, a stripping member, or the like.

In another aspect, embodiments of the present invention provide a system for separating an object from a patient tissue, where the system includes an internal sheath having a proximal end and a distal end, an external sheath having a proximal end and a distal end, an internal separator coupled with the distal end of the internal sheath, the internal separator having a first separating mechanism, and an external separator coupled with the distal end of the external sheath, the external separator having a second separating mechanism. The internal separator can be disposed at least partially within the external separator, and the internal and external separators can be configured for relative rotational movement that brings the first separating mechanism and the second separating mechanism together. In some cases, the internal separator includes an internal cutting member, an internal stripping member, an internal dilating member, or the like, and the external separator includes an external cutting member, an external stripping member, an external dilating member, or the like. In some aspects, the first separating mechanism includes a first cutting blade, a first stripping blade, a first dilating blade, or the like, and the second separating mechanism includes a second cutting blade, a second stripping blade, a second dilating blade, or the like. In another aspect, embodiments provide a separating system that includes a sheath having a distal end, and a cylindrical separator. The separator can include a distal end having a separating mechanism, and a proximal end coupled with the sheath distal end. The distal end of the cylindrical separator can define a plane that is substantially perpendicular to a central longitudinal axis of the cylindrical separator. In some cases, the sheath includes a proximal end that is less flexible than the distal end of the sheath. The distal end of the sheath can have bending stiffness less than about 6 lb/in. The sheath can have a torsional transmission of greater than about 0.177 pound-inch. In some embodiments, the sheath includes a braid. The separator can include a cutting member, a stripping member, a dilating member, or the like. The separating mechanism can include a cutting blade, a stripping blade, a dilating blade, or the like.

In another aspect, embodiments of the present invention provide a system for separating an object from a patient tissue that includes a sheath having a proximal end and a distal end, and a cylindrical separator coupled with the distal end of the sheath. The separator can have an internal lumen, a proximal end, and a distal end. The distal end of the separator can define a plane, and can include plurality of teeth having separating means in perpendicular alignment with the plane or in alignment with a central longitudinal axis of the sheath. The internal lumen of the separator can define a central longitudinal axis, and an acute angle between the plane and the central longitudinal axis can be within a range from about 30 degrees to about 85 degrees.

In another aspect, embodiments of the present invention provide a system for separating an object from a patient tissue. The system can include a sheath having a distal end, and a cylindrical separator having a proximal end, a distal end, and an internal lumen that defines a central longitudinal axis. The proximal end of the separator can be coupled to the distal end of the sheath, and the distal end of the separator can include a rim that defines a plane which is not perpendicular to the central longitudinal axis of the separator, a separating mechanism disposed along a first portion of the rim, and a blunt edge disposed along a second portion of the rim. In some cases, the separating mechanism can be configured to separate the object from the tissue when the separator is rotated in one direction, but not when the separator is rotated in an opposite direction. The separating mechanism can be a cutting blade, a stripping blade, a dilating blade, or the like. In another aspect, embodiments of the present invention provide a system for separating an object from a patient tissue. The system can include a flexible shaft having a proximal end and a distal end, and a metal separator having a proximal end, a distal end, and an internal lumen that defines a central longitudinal axis. The proximal end of the separator can be coupled to the distal end of the sheath, and the distal end of the separator can include a separating means and can define a plane which is not perpendicular to the central longitudinal axis of the separator. The proximal end of the flexible shaft may be less or more flexible than the distal end of the shaft. In some cases, the distal end of the flexible shaft has a bending stiffness less than about 6 lb/in. In some cases, the flexible shaft has a torsional transmission of greater than about 0.177 pound-inch. In some cases, the flexible shaft includes a braid. In many cases, the separating mechanism is configured to separate the object from the patient tissue when the separator is rotated.

In still another aspect, embodiments of the present invention provide a system for separating an object from a patient tissue. The system includes a flexible shaft having a proximal end, a distal end, and an internal lumen having an inner diameter greater than about 0.130 inch. The shaft can have a bending stiffness of less than about 6 lb/in and a torsional transmission of greater than about 0.177 pound-inch. The system may also include a separator having a proximal end and a distal end. The proximal end of the separator can be coupled to the distal end of the sheath, the distal end of the separator can include a separating mechanism, and the separating mechanism can have a hardness greater than about B65 Rockwell. In yet another aspect, embodiments of the present invention provide a method for separating a patient tissue from an object. The method can include providing a tool that has a sheath having a proximal end and a distal end, and a separator operably coupled to the distal end of the sheath. The separator can have a proximal end, a distal end that includes a rim, a separating mechanism disposed along a first portion of the rim, a blunt edge disposed along a second portion of the rim, and an internal lumen that defines a central longitudinal axis. The method can include contacting the separating mechanism with patient tissue that is attached to the object. The method can also include rotating the separator so as to separate the tissue from the object with the separating mechanism. In some cases, the rim defines a plane that is not perpendicular to the central longitudinal axis of the separator. In some cases, the rim defines a plane that is perpendicular to the central longitudinal axis of the separator. In some cases, the separating mechanism can be configured to separate the tissue from the object when the separator is rotated in one direction, but not when the separator is rotated in an opposite direction.

In still another aspect, embodiments of the present invention provide a system for separating an object from a patient tissue. The system can include a sheath having a distal end. The system can also include a cylindrical separator having a proximal end, a distal end, and an internal lumen that defines a central longitudinal axis. The proximal end of the separator can be coupled to the distal end of the sheath, and the distal end of the separator can include a rim that defines a plane, a separating mechanism disposed along a first portion of the rim, and a blunt edge disposed along a second portion of the rim. In some cases, the plane is substantially perpendicular to the central longitudinal axis of the separator. In some cases, the plane is not substantially perpendicular to the central longitudinal axis of the separator. Optionally, an acute angle between the plane and the central longitudinal axis can be within a range from about 30 degrees to about 85 degrees.

For a fuller understanding of the nature and advantages of the present invention, reference should be had to the ensuing detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a system for separating an object from a patient tissue according to embodiments of the present invention.

FIG. 1A illustrates a cross section of a handle according to embodiments of the present invention.

FIG. 1B depicts a cross section of a sheath according to embodiments of the present invention.

FIG. 1C shows a cross section of a distal portion of a separating system according to embodiments of the present invention.

FIG. 2A shows a system for separating an object from a patient tissue according to embodiments of the present invention.

FIG. 2B shows a cross section of a sheath combination according to embodiments of the present invention.

FIG. 3 illustrates a distal portion of a separating system according to embodiments of the present invention.

FIG. 4 illustrates a distal portion of a separating system according to embodiments of the present invention.

FIG. 5 illustrates a distal portion of a separating system according to embodiments of the present invention.

FIG. 6 depicts a distal portion of a separating system according to embodiments of the present invention.

FIG. 6A depicts a distal portion of a separating system according to embodiments of the present invention.

FIGS. 7A-7D show aspects of a separator according to embodiments of a present invention.

FIG. 7E shows a distal portion of a separating system in a method of use according to embodiments of the present invention.

FIGS. 8A and 8B show aspects of a separator according to embodiments of a present invention.

FIGS. 9A and 9B show aspects of a separator according to embodiments of a present invention.

FIGS. 10A and 10B show aspects of a separator according to embodiments of a present invention.

FIGS. 11A and 11B show aspects of a separator according to embodiments of a present invention.

FIG. 12 illustrates a cross section of a sheath according to embodiments of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention provide a mechanical sheath and cutting tip that can be safely deployed within the vascular system of a patient. Such systems include a flexible and torqueable sheath and a hard separating mechanism. A separating system can include, for example, a flexible sheath coupled with a tip, which may include a separating surface or shape. The cutting or separating surface or shape can be contacted with patient tissue, and the sheath can be rotated to effect cutting or separating of the tissue. Although the sheath may be flexible, it can also be pushable in the sense that a force applied to the proximal end of the sheath is in large part transferred to the distal end of the sheath. The sheath may also exhibit a high resistance to kinking or crushing. For example, it is possible to force the sheath into a severe bend or tortuous path without causing permanent deformation or damage to the sheath. Moreover, the sheath maintains a desired amount of torqueability, in that the a rotational force applied to a proximal end of the sheath is effectively translated to a distal end of the sheath.

A separating system can be used as an intra-operative device to free or explant a chronically implanted pacing or defibrillator lead. The system can include an inner lumen designed to allow a pacing lead and lead locking device to pass through it, as the system slides over the lead toward the distal tip of the lead in the heart. Often the system includes an outer sheath or shaft that can be used during the extraction procedure as an introducer and to support and align an inner sheath or shaft. The outer sheath can also be used as a conduit to remove the inner shaft with the extracted lead or object, and can be used as a conduit to implant a new lead or object.

Turning now to the drawings, FIG. 1 shows a system 100 for separating an object from a patient tissue according to embodiments of the present invention. System 100 can have a length A′ within a range from about 25 cm to about 75 cm. In some cases, length A′ is about 50 cm. System 100 includes a sheath 110 having a proximal end 112 and a distal end 114. Sheath 110 may be, for example, a braided shaft. System 110 also includes a handle 120 coupled with the proximal end 112 of sheath 110. Handle 120 can have a length B′ within a range from about 4 cm to about 15 cm. In some cases, length B′ is about 10 cm. System 100 also includes a cutting member or separator 130 coupled with the distal end 114 or sheath 110. In some embodiments, sheath 110 may include or be coupled with a flared exit port 140 or a similar configuration that facilitates the introduction of leads through sheath 110. In some cases, a proximal end of sheath 110 may include or be coupled with a hemostasis valve or connection to inhibit or control bleeding at the sheath proximal end. Features such as flared exit port 140 or the hemostasis valve may also be incorporated into handle 120. In use, an operator may advance sheath 110 into a patient, and while sheath is disposed within the patient, remove pacing leads or other objects from the patient. The operator may also insert new or replacement pacing leads or other objects into the patient by placing them through flared exit port 140 and into sheath 110. Thus, flared exit port 140 and sheath 110 can facilitate the implantation of a pacing lead or other object. Optionally, system 100 may include a pull wire for deflecting the distal end of the sheath. In some embodiments, a pull wire may be housed within a separate lumen of the sheath, and attached with the tip or other proximally located feature. When an operator causes the pull wire to be retracted, the pull wire causes deflection of the tip or other proximally located feature. In many cases, it is desirable to deflect a sheath top or other proximally located feature away from the wall of a vein or other body lumen. In some embodiments, sheath 110 or a portion thereof may include a braid or braiding 111. A braid may include, for example, a woven metallic or fiber layer. Often, a braid includes a group of filaments that are interwoven in a specific form, such as a cylinder or a tubular structure. A braid can be applied to the interior of sheath 110, the exterior of sheath 110, or both. In some cases, a braid may be incorporated into or integral with a sheath material. In some embodiments, a braid feature confers additional robustness to a sheath or shaft. For example, a braid may prevent or inhibit a sheath from being kinked or crushed during use.

As shown in FIG. 1A, handle 120 can have an outer diameter C′ within a range from about 0.25 to about 0.95 inches. In some cases, outer diameter C′ is about 0.75 inches. As shown in FIG. 1B, sheath 110 can have an inner diameter D′ within a range from about 0.090 to about 0.170 inch, and an outer diameter E′ within a range from about 0.140 to about 0.250 inch. In some cases, inner diameter D′ is about 0.130 inch and outer diameter E′ is about 0.155 inch. Sheath 110 can have an inner surface 116 and an outer surface 118. In some cases, inner surface 116, outer surface 118, or both, are coated with or include a slippery, smooth, or lubricious material. Exemplary hydrophilic polymer coatings or materials that may be used are produced by Surmodics, Inc. of Eden Prairie, Minn. Thus, for example, when using system 100 to remove a pacing lead from a patient, outer surface 118 passes easily through the patient's anatomy, and inner surface 116 passes easily over the pacing lead, without creating unwanted or excessive friction.

FIG. 1C illustrates cylindrical cutting member 130 and distal end 114 of sheath 110. Cylindrical cutting member 130 can include an internal lumen 132, a proximal end 134, and a distal end 136. In some cases, distal end 136 of cutting member 130 defines a plane 137. As shown here, cutting member 130 has a central longitudinal axis 133, which can be defined by, for example, internal lumen 132 of the cutting member, inner surface 116 of the shaft, or the inner or outer surface of cutting member 130. An acute angle a between plane 137 and central longitudinal axis 133 can be within a range from about 30 degrees to about 85 degrees. In some cases, angle α is about 45 degrees. Distal end 136 of cutting member 130 can include a cutting edge or surface on part of the distal end 136. In some cases, distal end 136 includes a cutting edge or surface circumscribing the entire distal end of a bevel. A cutting edge or surface can include, for example, a blade or wedge for severing tissue or for separating tissue from an object or from adjacent tissue. In some cases, a cutting edge or surface includes an abrasive substance for abrading tissue or other material. Distal end 136 may include a metal or metal alloy such as titanium, stainless steel, or a metal or alloy coated with a hard coating such as titanium oxide. Advantageously, the use of a flexible and torqueable sheath as described elsewhere herein allows an operator to advance a hard distal end 136 along an entire or substantial portion of a pacing lead, or object to be removed or separated from a patient's body, which may be located in a tortuous or labyrinthine vessel or lumen.

Sheath 110 may be motorized to rotate or coupled with a motor that induces rotation in or applies torque to the sheath. In some embodiments, sheath 110 may be motorized to move in a reciprocating motion back and forth like a clothes washer cylinder or drum. Sheath 110 can be constructed to have varying degrees of stiffness along the length of the sheath. In some cases, a distal portion or end is more flexible relative to a proximal portion or end of the sheath. For example, distal end 114 of sheath 110 may include a flexible portion approximately 5 to 15 cm in length. In some cases, sheath 110 or sections or portions thereof may be fabricated via multi-durometer construction or multi-diameter construction techniques. For example, a sheath may include a series of one or more tubes or tube-like elements of progressively reduced durometer material fused together to form a sheath of varying stiffness. Accordingly, a sheath may have one portion that exhibits a first stiffness, and a second portion that exhibits a second stiffness. In one embodiment, the hardness of the tubes or tube-like structures become progressively softer or more flexible when going from the proximal end of the sheath to the distal end of the sheath. In some embodiments, tubes or tube-like structures may have progressively smaller diameters or thicknesses when going from the proximal end of the sheath to the distal end of the sheath. Relatedly, sheath 110 can present any of a variety of braid angles. For example, a sheath or components thereof may have sections, portions, or layers having a higher angle braid angle that imparts more flexibility. Similarly, a sheath or components thereof may have sections, portions, or layers having a lower braid angle that imparts less flexibility. Sheath 110 can be configured to provide a desired torque response. For example, in some embodiments sheath 110 provides close to 1:1 torque response. Torque response can refer to the ratio of proximal rotations to distal rotations. In some embodiments, a sheath can have a torque response within a range from about 1:0.6 to about 1:1. In similar embodiments, a sheath can have a torque response within a range from about 1:0.7 to about 1:1. A sheath may also have a torque response within a range from about 1:0.8 to about 1:1. In some cases, a sheath has a torque response within a range from about 1:0.9 to about 1:1. Sheath embodiments of the present invention can advantageously provide an optimum or high torque response while retaining a high degree of flexibility, which combination is often not available with current sheath or lead removal products.

System 100 may also include a positive fixation assembly 150 or configuration for handle 120. In this way, handle 120 can be fixed or is fixable at any desired location along the length of sheath 110. In use, when sheath 110 is inserted into a patient, an operator can therefore adjust the position of handle 120 along the length of sheath 110. For example, the operator may fix handle 120 at a location that is close to the patient or near a sheath insertion point. In this way, the operator can reduce or otherwise modulate or select the amount of sheath that is present between the handle and the patient's body or insertion point. The ability to control the position of handle 120 along the length of sheath 110 allows the operator to have more easily maneuver the system 110. If the distance between handle 120 and the patient's body or insertion point is too great, for example, the system may exhibit undesirable flexing or movement as the operator maneuvers the system. The positive fixation feature allows the handle to be moveable to more proximal positions along the sheath as a lead extraction progresses.

FIG. 2A shows a system 200 for separating an object from a patient tissue according to embodiments of the present invention. System 200 includes a sheath 210 having a proximal end 212 and a distal end 214. Sheath 210 may be include from, for example, a braided shaft. System 210 also includes a handle 220 coupled with the proximal end 212 of sheath 210. System 200 also includes a cutting member or separator 230 coupled with the distal end 214 or sheath 210, and an outer sheath 240 encompassing at least a portion of sheath 210. Outer sheath 240 can have a length A′ within a range from about 25 cm to about 50 cm. In some cases, length A′ is about 40 cm. As shown in FIG. 2B, outer sheath 240 can have an inner diameter B′ within a range from about 0.130 inch to about 0.220 inch. In some cases, inner diameter B′ is about 0.170 inch. Often the outer sheath or shaft can be used during an extraction procedure as an introducer and to support and align the inner sheath or shaft. The outer sheath can also be used as a conduit to remove the inner shaft with the extracted lead or object, and can be used as a conduit to implant a new lead or object. In some embodiments, an outer sheath is left in place during a lead extraction procedure once the inner sheath and lead are removed from the patient. The outer sheath can be used as a conduit for a guidewire to facilitate the implantation of a new lead. The outer sheath distal tip can be disposed into the atrium, or retracted into the brachiocephalic vein. In some embodiments, an inner sheath and an outer sheath are advanced over a lead in an alternating “inchworm” technique. An operator may determine that a tissue obstruction is met if the inner sheath will not advance into the vessel or vein, if the inner sheath bows outward slightly when longitudinal pressure is applied, if fluoroscopy indicates that the inner sheath distal end does not advance relative to the lead body, or if fluoroscopy indicates that the inner sheath distal end is not caught on a lead electrode, a lead bend, or another lead. If an obstruction such as scar tissue is met and the inner sheath cannot be advanced, the operator may consult orthogonal fluoroscopic views to ensure that the distal tip of the inner sheath is aligned with the longitudinal axis of the lead. The operator may retract the outer sheath so that its distal end does not overlap the distal tip of the inner sheath. The operator can press the inner sheath into or against the obstruction and rotate the sheath to separate the tissue or obstruction from the lead. The outer sheath can then be advanced to a new position along the inner sheath. In some embodiments, when the lead or object is free, it is drawn into the inner sheath before the lead, the inner sheath, and the outer sheath are removed from the body. Separating systems according to the present invention are also well suited for use with lead locking devices. In some embodiments containing an inner sheath and an outer sheath, the sheaths can each have distal tips configured for a scissoring cutting action as described herein with reference to FIG. 5. In some embodiments, system 200 includes a single sheath.

FIG. 3 shows a portion of a separating system according to embodiments of the present invention. System 300 includes a shaft or sheath 310 having a distal end 312. System 300 also includes a cutting member or separator 320 coupled with distal end 312. Cutting member includes an internal lumen 332, a proximal end 334, and a distal end 336. System 300 can also include an abrasive materia1340 or a separating mechanism or means disposed on or encrusted in distal end 336 of cutting member 320. In some embodiments, abrasive material 340 includes diamond chips, aluminum carbide chips, silica carbide chips, and the like. Abrasive material can be attached with distal end 336 via any of a variety of methods, including gluing, vapor deposition, embedding, and the like. In some cases, distal end or rim 336 of cutting member 320 defines a plane 337, and internal lumen 332 of the cutting member 320 defines a central longitudinal axis 333. An acute angle α between plane 337 and central longitudinal axis 333 can be about 45 degrees. In some cases, angle α is within a range from about 30 degrees to about 85 degrees. System 300 can be configured such that when distal end 336 is pressed onto patient tissue, abrasive material 340 does not cut or sever the tissue, but when distal end is pressed onto patient tissue and sheath 310 or cutting member 320 is rotated about central longitudinal axis 333, abrasive material 340 acts to cut or sever the tissue.

FIG. 4 shows a portion of a separating system according to embodiments of the present invention. System 400 includes a sheath 410 having a distal end 412. System 400 also includes a cutting member or separator 420 coupled with distal end 412. Cutting member includes an internal lumen 422, a proximal end 424, and a distal end or rim 426. Internal lumen 422 defines a central longitudinal axis 423. Distal end 426 of cutting member 420 includes a separating means or mechanism such as a cutting edge 426a aligned with central longitudinal axis 423, and cutting edge or blade 426a has a proximal end 426b and a distal end 426c. Distal end 426 of cutting member 420 also includes a distal edge 426d having a proximal end 426e that joins or meets with the cutting edge proximal end 426b, and a distal end 426f that joins or meets with cutting edge distal end 426c. Separating mechanism 426a can present any desired profile for separating tissue. As shown here, separating mechanism 426a defines a substantially straight edge profile that extends between cutting edge distal end 426c and cutting edge proximal end 426b. In some embodiments, the profile provided by separating mechanism 426a between cutting edge distal end 426c and cutting edge proximal end 426b presents an arc, or a convex or concave contour. In some cases, the profile may have an irregular contour. In addition, leading edge 426c can have a rounded profile to prevent tissue penetration when the sheath is advanced longitudinally. Relatedly, separating mechanism 426a may also provide a beveled edge, similar to blade 814 as described with reference to FIG. SB. Distal edge 426d often presents or includes a spiral or helical contoured portion or shape. Any of a variety of materials can be used in the manufacture of a cutting element. For example, a cutting element may include a metal or metal alloy such as titanium, stainless steel, or a metal coated with a hard coating such as titanium oxide. In some embodiments, cutting member 420 is configured to cut only when rotated one direction, when blade 426a presents a leading edge, as indicated by arrow A.

FIG. 5 shows a portion of a separating system according to embodiments of the present invention. System 500 includes an internal sheath 510 having a distal end 512, and an external sheath 520 having a distal end 522. System 500 also includes an internal cutting member or separator 530 coupled with distal end 512. Internal cutting member 530 includes an internal lumen 532, a proximal end 534, and a distal end or rim 536. In some cases, internal cutting member is cylindrical in shape. Distal end 536 of internal cutting member 530 can include one or more cutting blades 538a,b. System 500 also includes an external cutting member or separator 540 coupled with distal end 522. External cutting member 540 includes an internal lumen 542, a proximal end 544, and a distal end 546. In some cases, external cutting member is cylindrical in shape. Distal end 546 of external cutting member 540 can include one or more cutting blades or separating means or mechanism 548a,b. As shown here, internal cutting member 530 is disposed at least partially within external cutting member 540, and internal and external cutting members 530, 540 are configured for relative rotational movement so that blade pairs can form scissors or clippers. For example, blade 538a and blade 548a can be brought together or toward each other in a shearing or clipping fashion. In some embodiments, each of the internal and external sheaths have distal metal bands. Each band can be serrated in such a way that each band forms one or more blades of one or more scissor pairs, where one blade of each scissor pair is located on each band. In use, the internal and external sheaths can be rotated relative to one another to close the scissor pairs and produce a cutting action. In addition to or instead of the cutting action, rotation or advancement of one or both of the sheaths can operate to perform a dilating or stripping action. In many cases, however, the actuation of the distal end of the system provides a primarily cutting or clipping action.

FIG. 6 shows a system 600 for cutting tissue in a patient according to embodiments of the present invention. System 600 includes a sheath 610 having a distal end 612, and a cutting member 620 coupled with distal end 612. In some cases, cutting member 620 provides a cylindrical shape. Cutting member 620 includes an internal lumen 622, a proximal end 624, and a distal end or rim 626. In some cases, distal end 626 of cutting member 620 defines a plane 630, and internal lumen 622 of the cutting member 620 defines a central longitudinal axis 640, wherein an acute angle α between plane 630 and central longitudinal axis 640 is within a range from about 45 degrees to about 90 degrees. In some cases, angle α is within a range from about 60 degrees to about 85 degrees. In embodiments where there is such an angle, distal end 626 of cutting member 620 may present a leading edge 660 and a trailing edge 650. For example, leading edge 660 can be disposed toward the cutting member distal end 626 and trailing edge 670 can be disposed toward the cutting member proximal end 624. In some cases, distal end 626 of cutting member 620 includes a plurality of teeth or serrations 650. Teeth 650 can have cutting edges or blades 652 along the side walls of the teeth. The top surface or peripheral lateral surfaces 651 of the teeth can be rounded or smooth. The inner diameter 653 of each tooth may present a sharp edge. In some cases, cutting edges 652 are in perpendicular alignment with plane 630 or with a plane defined by face 628. In some cases, cutting edges 652 are in directional alignment with a central longitudinal axis defined by the cutting member or separator. In some cases, cutting or separating edges 652 are in directional alignment with a central longitudinal axis defined by the sheath. As shown in FIG. 6A, distal end 626 of cutting member 620 may present a circular face 628, and a plurality of teeth or crests 650 are disposed circumferentially around the face. There is a substantially equivalent or equivalent arc spacing 628a between each tooth 650, and each tooth presents a similar or equivalent width arc width 650a along inner diameter edge 653. In some embodiments, the arc spacing 628a between teeth 650 may be unequal. In some embodiments, the arc width 650a may vary among different teeth 650. In some cases, teeth may be present at one portion of the face 628, and absent from another portion of the face 628. For example, in some embodiments, leading edge 660 may include one or more teeth, whereas trailing edge 670 may contain no teeth. Relatedly, in some embodiments one portion of the face may contain more teeth than another similar-sized portion of the face.

FIGS. 7A-7D illustrate a cutting member or separator 700 according to embodiments of the present invention. As shown in the side view provided by FIG. 7A, cutting member 700 includes a distal end or rim 710 and a proximal end 720. Distal end 710 is beveled and defines a plane 715. In some embodiments, plane 715 may be skew or not perpendicular to central longitudinal axis 711. For example, there may be an acute angle α between plane 715 and axis 711 within a range from about 30 degrees to about 85 degrees. Axis 711 can be a central longitudinal axis defined by an internal lumen of cutting member 700. Distal end 710 also includes a recess 712 having a blade or separating mechanism 714. As shown in the perspective view provided by FIG. 7B, distal end 710 also includes a rounded or smooth surface 716. Distal end 710 can also include a distal tip 718 that is rounded or smooth. Often, distal tip 718 is somewhat blunted, and does not present a sharp point or a leading cutting edge when cutting member 700 is advanced. In use, distal tip 718 of cutting member 700 can be pressed lightly against a patient tissue without severing the tissue. Cutting member 700 can be rotated in the direction indicated by the arrow A shown in FIG. 7C to advance the leading edge of blade 714. In contrast to rounded or smooth surface 716, recess 712 can present a scooped or beveled surface that presents a sharp, acute, or knifelike blade 714. Outer diameter 713 of recess 712 can be disposed proximal relative to inner diameter 719 of recess 712. Blade 714 can be disposed along the outer diameter 713 of recess 712. As shown in FIG. 7D, blade 714 may also be disposed along inner diameter 719, or between outer diameter 713 and inner diameter 719, and may define any suitable combination of convex, concave, or curved bevel surface 717. FIG. 7E provides a side view of cutting member 700 in use, where cutting member 700 is rotated in the direction indicated by arrow B, so that blade 714 presses against and cuts patient tissue 730. In this manner, tissue 730 can be severed or separated from an object such as a pacing lead 750.

FIGS. 8A and 8B illustrate a cutting member or separator 800 according to embodiments of the present invention. As shown in the side view provided by FIG. 8A, cutting member 800 includes a distal end or rim 810 and a proximal end 820. Distal end 810 is beveled and defines a plane 815. In some embodiments, plane 815 may be skew or not perpendicular to central longitudinal axis 811. For example, there may be an acute angle α between plane 815 and axis 811 within a range from about 30 degrees to about 85 degrees. Axis 811 can be a central longitudinal axis defined by an internal lumen of cutting member 800. Distal end 810 also includes a notch 812 and a blade or separating means or mechanism 814. As shown in the perspective view provided by FIG. 8B, distal end 810 also includes a rounded or smooth surface 816. Often, distal tip 818 is somewhat blunted, and does not present a sharp point or a leading cutting edge when cutting member 800 is advanced. In use, a distal tip 818 of cutting member 800 can be pressed lightly against a patient tissue without severing the tissue. In a manner similar to that described with reference to cutting member 700, cutting member 800 can be rotated so as to cut patient tissue. Cutting member 800 can be rotated in the direction indicated by the arrow A shown in FIG. 8B to advance the leading edge of blade 814. In some embodiments, cutting member 800 is configured to cut only when rotated one direction, when blade 814 presents a leading edge. In contrast to rounded or smooth surface 816, notch 812 can present a scooped or beveled surface that presents a sharp, acute, or knifelike blade 814. Outer diameter 813 of notch 812 can be disposed proximal relative to inner diameter 819 of recess 812. Blade 814 can be disposed along the outer diameter 813 of notch 812. In a manner similar to that described above with reference to blade 714, blade 814 may also be disposed along inner diameter 819, or between outer diameter 813 and inner diameter 819, and may define any suitable combination of convex, concave, or curved bevel surface 817.

FIGS. 9A and 9B show a cutting member or separator 900 according to further embodiments of the present invention. As shown in the side view provided by FIG. 9A, cutting member 900 includes a distal end or rim 910 and a proximal end 920. Distal end 910 is beveled and defines a plane 915. In some embodiments, plane 915 may be skew or not perpendicular to central longitudinal axis 911. For example, there may be an acute angle α between plane 915 and axis 911 within a range from about 30 degrees to about 85 degrees. Axis 911 can be a central longitudinal axis defined by an internal lumen of cutting member 900. As shown in the perspective view provided by FIG. 9B, distal end 910 also includes a rounded or smooth surface 916, and a depression 912 in an interior surface 913 of cutting member 900. Depression 912 presents a blade or separating means or mechanism 914 for use in cutting or separating patient tissue. In use, a distal tip 918 of cutting member 900 can be pressed lightly against a patient tissue without severing the tissue. In a manner similar to that described with reference to cutting member 700, cutting member 900 can be rotated so as to cut patient tissue. Cutting member 900 can be rotated in the direction indicated by the arrow A shown in FIG. 9A to advance the leading edge of blade 914. In contrast to rounded or smooth surface 916, depression 912 can present a scooped or beveled surface that presents a sharp, acute, or knifelike blade 914. Outer diameter 917 of depression 912 can be disposed proximal relative to inner diameter 919 of depression 912. Blade 914 can be disposed along the outer diameter 913 of depression 912, or blade 914 may be at least partially disposed between outer diameter 913 and inner diameter 919. In a manner similar to that described above with reference to blade 714, blade 914 may also be disposed along inner diameter 919.

FIGS. 10A and 10B show a cutting member or separator 1000 according to embodiments of the present invention. As shown in the side view provided by FIG. 10A, cutting member 1000 includes a distal end or rim 1010 and a proximal end 1020. Distal end 1010 is beveled and defines a plane 1015. In some embodiments, plane 1015 may be skew or not perpendicular to central longitudinal axis 1011. For example, there may be an acute angle α between plane 1015 and axis 1011 within a range from about 30 degrees to about 85 degrees. Axis 1011 can be a central longitudinal axis defined by an internal lumen of cutting member 1000. As shown in the perspective view provided by FIG. 10B, distal end 1010 also includes rounded or smooth surface 1016, and a blade or sharp surface 1014 that extends at least partially around the periphery of distal end 1010, where blade or separating mechanism or means 1014 can be used for cutting or separating patient tissue. Often, blade 1014 is disposed at or near an inner surface 1013 of cutting member 1000. In some cases, blade 1014 can include an edge of inner surface 1013. In use, a distal tip 1018 of cutting member 1000 can be pressed lightly against a patient tissue without severing the tissue. In a manner similar to that described with reference to cutting member 700, cutting member 1000 can be rotated so as to cut patient tissue. Cutting member 1000 can be rotated in the direction indicated by the arrow A shown in FIG. 10A, or in the direction indicated by arrow B, to advance the leading edge of blade 1014. As shown here, rounded or smooth surface 1016 may be continuous with a sharp, acute, or knifelike blade 1014. Surface 1016 may be disposed at or toward outer diameter 917 of cutting member 1000, and blade 1014 may be disposed at or toward inner diameter 1019 of cutting member 1000. In some cases, blade 1014 may be disposed distal to smooth surface 1016, and in some cases blade 1014 may be disposed proximal to smooth surface 1016. In some embodiments, cutting or separating mechanism 1014 can be disposed along the inner diameter 1019 of separator 1000. Thus, in use the cutting or separating mechanism 1014 can be kept away from a vessel wall or other portion of the patient's body. Separating mechanism 1014 can also extend circumferentially about the distal end of separator 1000, and thus can provide a cutting or separating action when separator 1000 is advanced longitudinally, as well as when separator 1000 is rotated in either direction.

FIGS. 11A and 11B show a cutting member or separator 1100 according to embodiments of the present invention. As shown in the side view provided by FIG. 11A, cutting member 1100 includes a distal end or rim 1110 and a proximal end 1120. Distal end 1110 defines a plane 1115 that is substantially perpendicular or perpendicular to a central longitudinal axis 1111 of cutting member 1100, and thus angle α is 90 degrees or about 90 degrees. In some embodiments, plane 1115 may be skew or not perpendicular to central longitudinal axis 1111. For example, there may be an acute angle between plane 1115 and axis 1111 within a range from about 30 degrees to about 85 degrees. As shown in the perspective view provided by FIG. 11B, distal end 1110 also includes at least one rounded or smooth surface 1116, and at least one recess 1112, where recess 1112 can provide a blade or separating mechanism or means 1114. In use, a distal tip 1118 of cutting member 1100 can be pressed lightly against a patient tissue without severing the tissue. In a manner similar to that described with reference to cutting member 700, cutting member 1100 can be rotated so as to cut patient tissue. Cutting member 1100 can be rotated in the direction indicated by the arrow A shown in FIG. 11B to advance the leading edge of blade 1114. In contrast to rounded or smooth surface 1016, recess 1112 can present a scooped or beveled surface that presents a sharp, acute, or knifelike blade 1114. Outer diameter 1117 of recess 1112 can be disposed proximal relative to inner diameter 1119 of recess 1112. Blade 1114 can be disposed along the outer diameter 1117 of recess 1112. In a manner similar to that described above with reference to blade 714, blade 1114 may also be disposed along inner diameter 1119, or between inner diameter 1119 and outer diameter 1117.

FIG. 12 illustrates a cross section of a flexible sheath or shaft according to embodiments of the present invention. Shaft 1200 includes an inner lumen 1210, an inner layer 1220, a central layer 1230, a braid layer 1240, and an outer layer 1250. In some embodiments, an inner diameter ID of shaft 1200 is within a range from about 0.147 inch to about 0.187 inch. Optionally, inner diameter ID can be about 0.167 inch. In some embodiments, an outer diameter OD of shaft 1200 is within a range from about 0.175 inch to about 0.215 inch. Optionally, outer diameter OD can be about 0.195 inch. Shaft 1200 may have a total wall thickness WT within a range from about 0.011 inch to about 0.068 inch. Inner layer 1220 may include a fluoropolymer such as fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE). Inner layer 1220 can have a wall thickness of about 0.002 inch. Central layer 1230 may include a thermoplastic elastomer such as Pebax•• (polyether bloc amide), with a durometer of about 25. Central layer 1230 can have a wall thickness of about 0.002 inch. Braid layer 1240 can include a 304 stainless steel ribbon having a thickness of about 0.001 inch and a width of about 0.004 inch. Braillayer 1240 can have a wall thickness of about 0.002 inch, due to two overlapping layers of the 0.001 inch thick ribbon. Outer layer 1250 can include a thermoplastic elastomer such as Pebax® with a durometer of about 69. In some embodiments, the braid is a 16 strand braid having a 35 Pic count (crossings per inch). The braid may present 28 percent coverage (surface area) and a braid angle of about 67.8 degrees. Such sheath configurations provide for a very flexible construction that retains effective torque properties.

In some embodiments, shaft 1200, in combination with a separator, can be dimensioned to remove pacing leads up to 13 French (0.170 inch) in diameter. The shaft can have a bending stiffness of less than about 6 pounds per inch (lb/in), and a torsional stiffness greater than about 0.177 pound inch (lb-in). The separator can include a separating mechanism having a hardness greater than about B65 Rockwell. The separating mechanism hardness can be measured by the Rockwell scale, a standard scale used to grade metals. Table 1 provides a comparison between an exemplary shaft embodiment and other commonly used lead extraction shafts.

TABLE 1
		Bending	Torsional Transmission
	Test	Stiffness	(lb-in)
	Number	(lbf/in)	90°	180°
Shaft	1	3.674	0.266	0.434
0.195 inch OD	2	3.681
0.169 inch ID	3	3.81
Commercial sheath 1	1	13.643	0.637	0.708
0.18 inch OD	2	15.19
0.151 inch ID	3	14.626
Commercial sheath 2	1	6.662	0.531	0.903
0.205 inch OD	2	7.071
0.169 inch ID	3	7.006
Commercial sheath 3	1	6.965	0.363	0.531
0.136 inch OD	2	6.998
0.109 inch ID	3	6.729
Commercial sheath 4	1	3.31	0.150	0.186
0.153 inch OD	2	3.292
0.112 inch ID	3	3.284
Commercial sheath 5	1	13.009
0.205 inch OD	2	13.457
0.168 inch ID	3	13.932
Commercial sheath 6	1	2.983
0.153 inch OD	2	3.014
0.112 inch ID	3	3.012

Table 1 indicates that embodiments of the present invention provide a sheath having bending properties similar to a smaller commonly available sheath. However, the present sheath can be sized to accommodate a lead or other object having a large diameter, while still retaining desirable torque properties. Moreover, embodiments of the present invention provide a system that includes a flexible and torqueable sheath and a hard separating mechanism.

Bending stiffness can be defined as the slope of the force/deflection curve pursuant to a flexural test such as ASTM D790 (e.g. 3 point bend test with 3 inch span length). Embodiments of the present invention provide sheaths having a bending stiffness of less than about 6 pound force per inch. Torsional transmission can be defined as the resulting torque load (e.g. in Newton-centimeters) transmitted to a distal end of a sheath while rotating a proximal end of the sheath a given amount (e.g. 90 degrees). The torsional transmission values provided in Table 1 correspond to a span (tube) length of 12 inches. An exemplary separating system may therefore include a flexible shaft having an inner diameter greater than about 0.130 inch and a bending stiffness of less than about 6 lb/in. The shaft can have a torsional transmission of greater than about 0.177 lb-in. The system can also include a separating mechanism having a hardness greater than about B65 Rockwell.

In addition to being well suited for the removal or detachment of pacing leads from a patient, embodiments of the present invention are well suited for detaching or removing any of a variety of objects from a patient, such as catheters, wires, implants, or other foreign bodies. Such objects may be disposed in veins, arteries, or any body lumen, cavity, or tissue.

Embodiments of the invention have now been described in detail. However, it will be appreciated that the invention may be carried out in ways other than those illustrated in the aforesaid discussion, and that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the scope of this invention is not intended to be limited by those specific examples, but rather is to be accorded the scope represented in the following claims.

Claims

1. A system for separating a pacing lead from patient tissue, comprising: a flexible sheath having a distal end;a handle coupled with the flexible sheath at a position proximal to the distal end of the flexible sheath; anda cylindrical separator having a proximal end, a distal end, and an internal lumen,wherein the proximal end of the cylindrical separator is coupled to the distal end of the flexible sheath, and the distal end of the cylindrical separator comprises: a rim;a separating mechanism disposed in a recess formed in at least a portion of a leading edge of a first portion of the rim, wherein the leading edge faces at least partially in a first direction to separate the patient tissue when the cylindrical separator is in contact with the patient tissue and rotated in the first direction, wherein the first direction is opposite a second direction; anda blunt edge having a beveled shape and disposed along a second portion of the rim, wherein the second portion of the rim is distal to the separating mechanism, wherein when the cylindrical separator is in contact with the patient tissue and rotated in the second direction, the blunt edge contacts the patient tissue and the leading edge does not separate the patient tissue;wherein the flexible sheath and the cylindrical separator are configured for placement over the pacing lead.

2. The system according to claim 1, wherein the separating mechanism comprises a member selected from the group consisting of a cutting blade, a stripping blade, and a dilating blade.

3. The system according to claim 1, wherein the separating mechanism is configured to not sever the patient tissue when the cylindrical separator is pressed lightly against the patient tissue.

4. The system according to claim 1, wherein the separating mechanism comprises a sharp surface on at least a portion of an outer diameter of the recess.

5. The system according to claim 1, wherein the recess comprises a beveled surface.

6. The system according to claim 1, wherein the separating mechanism comprises a sharp surface on at least a portion of an inner diameter of the recess.

7. The system according to claim 1, wherein the recess comprises a notch type shape.

8. The system according to claim 1, wherein the flexible sheath comprises a braid.

9. A system for separating a pacing lead from a patient tissue, comprising: a flexible sheath having a distal end;a handle coupled with the flexible sheath at a position proximal to the distal end of the flexible sheath; anda cylindrical separator having a proximal end, a distal end, and an internal lumen that defines a central longitudinal axis,wherein the proximal end of the cylindrical separator is coupled to the distal end of the flexible sheath, and the distal end of the cylindrical separator comprises:a leading edge that defines a plane, wherein the plane is non-perpendicular to the central longitudinal axis of the cylindrical separator; a blunt edge disposed on a first portion of the leading edge and in the plane, the blunt edge comprising a non-cutting edge when rotated in a first direction; anda recess disposed on a second portion of the leading edge, wherein the recess comprises a cutting edge when rotated in a second direction, wherein the second direction is opposite the first direction;wherein the flexible sheath and the cylindrical separator are configured for placement over the pacing lead.

10. The system according to claim 9, wherein the recess comprises a beveled surface.

11. The system according to claim 9, wherein the recess comprises a sharp surface on at least one of an inner and outer diameter.

12. The system according to claim 9, wherein an acute angle between the plane and the central longitudinal axis is within a range from about 30 degrees to about 85 degrees.

13. A system for separating a pacing lead from patient tissue, comprising: a sheath having a distal end;a handle coupled to the sheath at a position proximal to the distal end of the sheath;a cylindrical separator having a proximal end, a distal end, and an internal lumen, wherein the proximal end of the cylindrical separator is coupled to the distal end of the sheath, and the distal end of the cylindrical separator comprises: a separating mechanism disposed in at least one recess of a distal leading edge, wherein the distal leading edge faces at least partially in a first direction to separate the patient tissue when the cylindrical separator is in contact with the patient tissue and rotated in the first direction, wherein the first direction is opposite a second direction; anda blunt edge having a beveled shape and disposed distal to the separating mechanism, wherein when the cylindrical separator is in contact with the patient tissue and rotated in the second direction, the blunt edge contacts the patient tissue and the leading edge does not separate the patient tissue, and wherein the sheath and the cylindrical separator are configured for placement over the pacing lead.

14. The system according to claim 13, wherein a portion of an inside diameter of the recess is sharp.

15. The system according to claim 13, wherein the at least one recess comprises a scoop type shape.

16. The system according to claim 13, wherein the at least one recess comprises four recesses equally spaced around the leading edge.

17. The system according to claim 13, wherein the at least one recess comprises a notch type shape.

18. The system according to claim 13, wherein the at least one recess comprises a blade disposed along an outer diameter of the at least one recess.