US 20060253179 A1
A tip for engagement with an elongated sheath member for use in extracting an implanted structure, such as a cardiac lead, from an obstruction in a body vessel of a patient. The tip includes a tip body having a smaller diameter proximal end and a larger diameter distal end. The smaller diameter proximal end of the tip is sized for engagement with an inner surface of the distal end of the sheath member. The larger diameter distal end of the tip includes at least one element disposed along at least a portion of the outer surface of the tip body distal end. The element has a shape configured for cutting and/or disrupting the lead from the obstruction.
1. A tip for engagement with an elongated sheath member for extracting an implanted structure from an obstruction in a body vessel of a patient, said sheath member having a proximal end, a distal end, and a passageway for said implanted structure extending therethrough, said tip comprising:
a tip body having a smaller diameter proximal end and a larger diameter distal end, said smaller diameter proximal end sized for engagement with an inner surface of said sheath member distal end, said tip body distal end including at least one element disposed along at least a portion of an outer surface thereof, said element configured for at least one of cutting and disrupting said implanted structure from said obstruction.
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17. A tip for use with an elongated sheath member for extracting an implanted structure from an obstruction in a body vessel of a patient, said sheath member having a proximal end, a distal end, and a passageway for said implanted structure extending therethrough, said tip comprising:
a tip body having a smaller diameter proximal end and a larger diameter distal end, said smaller diameter proximal end sized for engagement with an inner surface of said sheath member distal end, said tip body proximal end including an attachment member for engagement with said sheath member inner surface, and said tip body distal end including at least one element disposed along an outer surface thereof, said element being configured for at least one of cutting and disrupting said obstruction.
18. The tip of
19. A device for extracting an implanted structure from an obstruction in a body vessel of a patient, the device comprising:
an elongated sheath having a proximal end, a distal end, and a passageway extending therethrough sized for receiving said implanted structure, said sheath having a length such that at least a distal portion of said sheath is receivable in said body vessel, said passageway sized such that said implanted structure is receivable therein;
a drive member operationally engaged with said elongated sheath for driving at least one of rotational and axial movement of said sheath; and
a tip engaged with said sheath distal end, said tip including a disruptor element at a distal end thereof for disrupting the obstruction.
20. The tip of
The present patent document claims the benefit of the filing date under 35 U.S.C. §119(e) of Provisional U.S. Patent Application Ser. No. 60/671,858, filed Apr. 15, 2005, which is hereby incorporated by reference.
1. Technical Field
This invention relates generally to devices for use in the medical arts. More particularly, the invention relates to a tip for use with a device for separating an implanted elongated structure, such as an implanted electrical pacemaker or defibrillator lead, from encapsulating biological tissue.
2. Background Information
A variety of medical treatments and surgical methods entail implanting an elongated structure in the body of a human or veterinary patient. Examples of such elongated structures include catheters, sheaths and cardiac electrical leads (such as pacemaker leads and defibrillator leads), as well as a variety of other devices. Over time, it can become necessary or desirable to remove the implanted elongated structure from the body of the patient. However, if the elongated structure has been implanted for an extended period of time, encapsulating biological tissue can grow around the elongated structure, making it difficult to remove the structure from the encapsulating tissue.
A heart pacemaker is typically implanted in a subcutaneous tissue pocket in the chest wall of a patient. A pacemaker lead extends from the pacemaker through a vein into a chamber of the patient's heart. The pacemaker lead commonly includes a conductor, such as an electrical wire coil, for conducting electrical signals (such as stimulating and/or sensing signals) between the pacemaker and the heart. Leads for defibrillators are generally similar to pacemaker leads, and are positioned about the heart. Defibrillator leads may be affixed either internally or externally of the heart.
Some leads include one or more coaxial or lateral helical wire coils having a hollow inner passageway that extends the entire length of the wire coil or coils. Other leads may be made with a cable without a hollow inner passageway. The wire coils are surrounded by an electrically insulating material such as a flexible tube, sheath or coating. The insulating material, generally formed of silicone or polyurethane, serves to simultaneously protect the wire coils from body fluids and insulate the wire coils from one another.
While cardiac electrical leads typically have a useful life of many years, over time such leads may become encapsulated by fibrotic tissue against the heart itself or the wall of the vein, or against other surrounding tissue. Encapsulation is especially encountered in areas where the velocity of the flow of blood is low. The fibrotic tissue can be very tough, which makes it difficult to remove the lead from the area of the heart without causing trauma to the area. When small diameter veins through which a pacemaker lead passes become occluded with fibrotic tissue, separation of the lead from the vein can cause severe damage to the vein, including the possible dissection or perforation of the vein. In such cases, separation of the lead from the vein is usually not possible without restricting or containing movement of the lead, i.e., fixing the lead in position with respect to the patient, in particular, with respect to the patient's vein.
To avoid this and other possible complications, some useless pacemaker or other leads are simply left in the patient when the pacemaker or defibrillator is removed or replaced. However, such a practice can incur the risk of an undetected lead thrombosis, which can result in stroke, heart attack, or pulmonary embolism. Such a practice can also impair heart function, as plural leads can restrict the heart valves through which they pass.
There are many other reasons why removal of a useless lead may be desirable. For example, if there are too many leads positioned in a vein, the vein can be obstructed to the extent that fluid flow through the vein is severely compromised. In addition, multiple leads can be incompatible with one another, thereby interfering with the pacing or defibrillating function. An inoperative lead can migrate during introduction of an adjacent second lead, and mechanically induce ventricular arrhythmia. Other potentially life-threatening complications can require the removal of the lead as well. For example, removal of an infected pacemaker lead may be desirable so as to avoid conditions such as septicemia or endocarditis.
Surgical removal of a heart lead in such circumstances often involves open heart surgery. However, open heart surgery is accompanied by significant risk and cost to the patient, as well as a potential for unintended complications. A variety of methods and apparatuses have been devised as alternatives to open heart surgery for heart lead removal. Several of these methods and apparatuses are described in related patents, such as U.S. Pat. No. 5,697,936, titled “Device for Removing an Elongated Structure Implanted in Biological Tissue”; U.S. Pat. No. 5,507,751, titled “Locally Flexible Dilator Sheath”; U.S. Pat. No. 5,632,749, titled “Apparatus for Removing an Elongated Structure Implanted in Biological Tissue”; U.S. Pat. No. 5,207,683, titled “Apparatus for Removing an Elongated Structure Implanted in Biological Tissue”; U.S. Pat. No. 4,943,289, titled “Apparatus for Removing an Elongated Structure Implanted in Biological Tissue”; U.S. Pat. No. 5,011,482, titled “Apparatus for Removing an Elongated Structure Implanted in Biological Tissue”; U.S. Pat. No. 5,013,310, titled “Method and Apparatus for Removing an Implanted Pacemaker Lead”; U.S. Pat. No. 4,988,347, titled “Method and Apparatus for Separating a Coiled Structure from Biological Tissue”; U.S. Pat. No. 5,423,806, titled “Laser Extractor for an Implanted Object”; U.S. Pat. No. 6,419,974, titled “Radio Frequency Dilator Sheath”, and U.S. Pat. Nos. 6,687,548 and 6,712,826, each titled “Apparatus for Removing an Elongated Structure Implanted in Biological Tissue”, among others. Each of the aforementioned patents is incorporated by reference as if fully set forth herein.
Most of the aforementioned patents describe manual, or mechanical, devices that are used for removing an implanted structure, such as a pacemaker lead. Others describe newer non-mechanical techniques, such as laser extraction and radio frequency extraction. These newer techniques have been effective in many cases when the amount and/or placement of fibrous growth that surrounds the implanted lead renders manual extraction difficult or impossible. One example of an effective device that uses radio frequency extraction to enable the physician to cut away the heavy growth is the PERFECTAŽ electrosurgical dissection sheath, available from Cook Vascular Incorporated, of Leechburg, Pa. The PERFECTAŽ sheath utilizes an intermittent discrete RF dissecting arc between bipolar electrodes located at the sheath's distal end. This sheath enables the physician to separate, with directed precision, a transvenous lead from its fibrous binding attachments.
Although the prior art devices have been found to be reasonably effective in many situations, physicians continue to encounter particularly difficult situations in which existing extraction devices provide unsatisfactory or inconsistent results. Due to the multiplicity of factors that may contribute to the difficulty in extracting an implanted lead, a technique that may be effective in one instance, may not provide similarly successful results in another instance. For example, manual devices normally are provided with single or telescoping flexible sheaths. Such sheaths, generally formed from a polymer, have the flexibility to enable the sheath to traverse tortuous pathways in the vessel. However, such sheaths may lack sufficient strength to cut through particularly tough tissue growth and calcification around the implanted lead. Laser and radio frequency devices normally utilize metallic sheaths. Such sheaths provide a good deal of strength to enable the sheath to cut through fibrous growths. However, some growths are resistant to metallic sheaths, and these sheaths may also lack the flexibility desired to maneuver tortuous pathways.
It would be desirable to provide a device and tip structure that is effective for removing implanted leads from a vessel, that is easy to operate, and that is versatile enough to overcome many of the obstacles that may be encountered in such operations with existing devices.
The present invention addresses the problems of the prior art extraction devices. In one form thereof, the invention comprises a tip for engagement with an elongated sheath member for use in extracting an implanted structure from an obstruction in a body vessel of a patient. The tip includes a tip body having a smaller diameter proximal end and a larger diameter distal end. The smaller diameter proximal end is sized for engagement with an inner surface of the distal end of the sheath member. The larger diameter distal end includes at least one element disposed along at least a portion of an outer surface of the distal end, and configured for cutting and/or disrupting the implanted structure from the obstruction.
In another form thereof, the invention comprises a tip for use with an elongated sheath member for extracting an implanted structure from an obstruction in a body vessel of a patient. The tip includes a tip body having a smaller diameter proximal end and a larger diameter distal end. The smaller diameter proximal end is sized for engagement with an inner surface of the sheath member distal end, and includes at least one attachment member for engagement with the inner surface of the sheath member. The larger diameter distal end of the tip body includes at least one element disposed along its outer surface. The element disposed along the tip body outer surface is configured for cutting and/or disrupting the obstruction in the body vessel.
In yet another form thereof, the invention comprises a device for extracting an implanted structure from an obstruction in a body vessel of a patient. The device includes an elongated sheath having a proximal end, a distal end, and a passageway extending therethrough sized for receiving the implanted structure. The sheath has a length 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 drive member is operationally engaged with the elongated sheath for establishing rotational and/or axial movement of the sheath. A tip is engaged with the distal end of the sheath, wherein the tip includes a disrupter element at a distal end thereof for disrupting the obstruction from the lead.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings, and specific language will be used to describe the same. It should nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
The present invention relates to an extraction device for extracting an elongated structure that has previously been implanted into a patient, and more particularly, to a tip for use with an extraction device. In the following discussion, the terms “proximal” and “distal” will be used to describe the opposing axial ends of the device, as well as the axial ends of various component features of the device. The term “proximal” is used in its conventional sense to refer to the end of the device (or component thereof) that is closest to the operator during use of the device. The term “distal” is used in its conventional sense to refer to the end of the device (or component) that is at the greatest distance from the operator, or that is initially inserted into the patient.
The implanted elongated structure targeted for removal may comprise a cardiac lead. A cardiac lead, as the term is used herein, refers to a lead that is used in connection with a heart-related device. Non-limiting examples of cardiac leads that may be removed by the inventive device include pacemaker leads, defibrillator leads, coronary sinus leads, and left ventricular pacing leads. When the device is used to remove a cardiac pacemaker lead, the distal end of the cardiac lead will normally be located within the vascular system of the patient, and in particular, within a chamber of the patient's heart (such as in an atrium or ventricle of the heart). When the implanted elongated structure is a defibrillator lead, the distal end of the structure may be located either in or about the heart of the patient. The distal ends of other types of implanted elongated structures targeted for removal may not necessarily be near the heart.
In addition to cardiac leads, the invention may also be used in the removal of other devices or leads, such as neurological pacing and stimulation leads. A non-limiting list of still other structures that can be removed by the inventive device includes implanted catheters, sheaths, cannulae and the like. For convenience, the following discussion will refer to the removal of a cardiac lead, such as a pacemaker or a defibrillator lead. However it should be understood that this is no way intended to be a limitation on the scope of the invention, and that the device may be suitable for removal of at least the other elongated structures referred to above.
Typically, a cardiac lead comprises an inner core, comprising a cable or a coil, surrounded by a layer of insulating material. As explained previously, some cardiac leads have a lumen extending therethrough, while others (i.e., “lumenless” leads) do not. The extraction devices of the present invention are useful for extracting implanted leads having a lumen, as well as lumenless leads. When an inventive device is to be used for removal of a cardiac lead, those skilled in the art will appreciate that the lead should initially be severed from the control device, such as the pacemaker or defibrillator, prior to any attempts to remove the lead. The control device will normally have a much larger diameter than the remainder of the lead, and thus only an unreasonably large dilator sheath could fit over the control device.
In the embodiment of the handle shown in
An external spur gear 40, having a plurality of teeth 41, is aligned with rack 38 such that spur gear teeth 41 mesh with rack teeth 39. Linear movement of rack teeth 29 therefore causes spur gear 40, and thus teeth 41, to rotate in the direction shown. A pawl 37 may be provided to inhibit undesired (counter-clockwise) rotation of the gear. Pawl 37 may also be configured to create ratcheting action upon movement of rack 38 and spur gear 40, and to provide an audible confirmation of the rotation of the spur gear. A stabilizing arm 42 extending in a proximal direction from rack 38 may be provided to maintain proper orientation of rack 38 in handle 12, and to ensure smooth movement of the trigger without bending or flexing when pulled under a load. Preferably, a spring 44 is affixed at one end to rack 38 and at the other end to housing wall peg 26 (distal of rack 38), for urging trigger 36 back to the position shown in
Spur gear 40 is affixed to large bevel gear 46, in a manner such that rotation of spur gear 40 causes a corresponding rotation of large bevel gear 46. Large bevel gear 46 includes a plurality of teeth 47 on a side of large bevel gear 46 opposite spur gear 40. Small bevel gear 48 is rotationally aligned with large bevel gear 46 in conventional fashion, such that large bevel gear teeth 47 mesh with small bevel gear teeth 49 as illustrated. Teeth 47 and 49 are aligned in conventional fashion for such bevel gears, in this case at an angle of about 90 degrees. As a result, the direction of rotation is translated via said gears along the 90 degree angle. Hub 50 is affixed to the side of small bevel gear 48 opposite teeth 49 for rotation in accordance with the rotation of small bevel gear 48. Hub 50 is sized and shaped to securely receive a proximal end of sheath 14, by conventional means such as adhesion, friction and/or threading.
Preferably, sheath 14 is removably affixed in lead extraction device 10 in a manner such that it may be selectively affixed to, or removed from, device 10.
Thus, as has been shown, sheath 14 may be selectively attached to, and detached from, handle 12. In this manner, sheath 14 and tip 16 may be simply removed from handle 12 following a lead extraction procedure, and replaced with another sheath and tip for use in a subsequent operation. Similarly, by utilizing detachable components, sheath 14 and tip 16 may be removed and replaced with a sheath and tip of a larger, or smaller, size as may be appropriate for removal of the particular lead involved in the procedure. Typically, lead extraction device 10 may also include a conventional free floating outer sheath (not shown) that telescopes over sheath 14 in well known fashion. Those skilled in the art are well aware of the use of telescoping outer sheaths for such purposes, and further discussion of this free floating outer sheath is not necessary for an understanding of the features of the present invention.
During manual operation of device 10 shown in
As illustrated in
Another feature of the invention comprises a device 80 for removing or otherwise extracting an elongated implanted structure, such as a lead, from a body vessel. Device 80 is illustrated in
One preferred manner of retaining sheath assembly 84 in handle 82 is shown in
Sheath assembly 84 also includes an element for providing spring action for inner sheath 88, such as flexible boot 96. As best shown in
Boot 96 should, of course, be flexible enough to permit relatively free and easy axial and/or rotational “free floating” movement of the inner sheath 88 and boot proximal end 107 when the lead extraction device encounters an obstruction during a lead extraction procedure. The boot should also have sufficient memory to enable it to return to its original, or neutral, position shown in the figures when no obstruction is present, or when the obstruction has been successfully cut. Preferably, the boot is formed from, e.g., a silicone or a polymeric composition having the requisite capabilities for spring action as described. Alternatively, the boot may comprise other known elastic or spring means, such as a stainless steel extension spring that is sized to fit the respective proximal ends of both the inner and outer sheaths. Those skilled in the art can readily select an appropriate composition and/or arrangement to provide the flexible feature of the boot.
In the preferred embodiment shown, the outer sheath 92 is not affixed to the device, but rather, works in a telescopic manner as it rides on the inner and intermediate sheaths 88, 90. Outer sheath 92 can be advanced beyond the distal end of cutting tip 98 in a distal direction if desired. The length of outer sheath 92, and the point at which it seats on the device when in its most proximal position, controls the degree of exposure of the inner sheath beyond the distal end of cutting tip 98.
A cutting tip 98 is affixed at the distal end of intermediate sheath 90. Preferably, cutting tip 98 is affixed to the inner surface of the distal end of intermediate sheath 90, as best shown in
Although thermal bonding is a preferred manner for affixing cutting tip 98 to sheath 90, those skilled in the art will appreciate that other known ways of bonding or otherwise affixing a tip to a substrate may be substituted. For example, the cutting tip can be provided with attachment members, such as barbs, along the proximal length of the cutting tip. As another alternative, the cutting tip can be provided with a roughened outer surface for facilitating attachment with the inner surface of the sheath. Those skilled in the art can readily determine other appropriate attachment mechanisms for a particular case.
Cutting tip 98 is preferably formed of a metal or a metal alloy. Non-limiting examples of tip compositions include stainless steel (preferably SAE No. 303-304), titanium and nitinol. In a preferred embodiment, the length of the metal cutting tip does not exceed about 0.375 inch (9.5 mm), however, those skilled in the art will appreciate that cutting tips of other sizes may be substituted in a particular case. In the preferred embodiment of
During use of the device, axial movement of the inner sheath in the proximal direction is limited by stop member 104. Preferably, stop member 104 is made from plastic, and is molded, machined, bonded, snapped, etc. into the handle of the lead extraction device. Stop member 104 is best shown in
The length of gap 103 also represents the distance that the tip of the inner sheath extends distally beyond the cutting tip when the inner sheath is in a neutral position (no obstruction encountered). Thus, as shown in the figures, distal end 89 of inner sheath 88 normally extends in the distal direction beyond the respective distal ends of intermediate sheath 90 and outer sheath 92, as well as beyond the distal end of the respective cutting teeth 87. As stated, the respective sheaths, and the stop, are dimensioned and arranged such that the distal tip 89 of inner sheath 88 cannot retract beyond the distal end of the intermediate sheath 90 when an obstruction is encountered. When this occurs, the inner sheath distal tip 89 slides in the proximal direction until it is flush with the distal end of intermediate sheath 90.
The lengths of the respective sheaths in sheath assembly 84 are thus arranged such that when the assembly is in the neutral position, the distal end of outer sheath 92 preferably shields inner sheath 88 and the cutting tip 98 of intermediate sheath 90. When the device is used to remove an implanted elongated structure, such as a cardiac lead, the device initially rails along the lead until an obstruction is encountered by the distal, or leading, end 89 of the inner sheath. At this time, the flexibility of boot 96 allows the inner sheath 88 to slide in the proximal direction in response to the obstruction. At the same time, lead extraction device 80 may be manually urged by the operator in the forward (distal) direction through the obstruction by pushing and/or twisting the device. The stop member 104 limits movement of the inner sheath 88 in the proximal direction, such that the distal tips of the cutting teeth are substantially flush with, or extend incrementally distal to, distal end 89 of inner sheath 88. During the retreat of inner sheath 88 in the proximal direction, intermediate sheath 90 and outer sheath 92 remain in a generally fixed position. Since the boot communicates with the respective proximal ends of both the intermediate and inner sheaths when the inner sheath is pushed in the proximal direction, the elastic or spring property of the boot causes a spring action at the proximal end of the inner sheath, thereby urging inner sheath 88 back to its extended position shown in the figures once the obstruction has been overcome.
In the embodiment shown, tip 118 is provided with a plurality of fingers 137 that project in the distal direction. If desired, tip 118 can be structured such that the respective distal ends of fingers 137 are slightly movable in conjunction with movement of knob 122 from an open position having a diameter that slightly exceeds the diameter of the lead to be extracted, to a closed position wherein the fingers wrap around and grip the lead. In addition to the configuration shown, tip 118 may have any of the tip configurations illustrated in
Further details of device 110, as well as its preferred mode of operation, may be readily observed in
Striker 121 is provided for manual operation of device 110. Striker 121 comprises a striker knob 122 at its proximal end, a bias means such as striker spring 124 distal of knob 122, a stop collar 126 distal of spring 124, and a striker leading edge 125. Leading edge 125 is sized such that it extends through an opening 131 at the distal end of housing 112. Distal movement of leading edge 125 is limited by stop collar 126. A striker flange 128 is positioned for selective contact with striker leading edge 125. Preferably, striker flange 128 includes a larger diameter proximal portion 134 and a smaller diameter distal portion 136, as best shown in
To operate device 110 manually, striker knob 122 is initially withdrawn in the proximal direction, as illustrated in
In a preferred embodiment, device 110 is also provided with a power supply 130 to enable powered operation of the device. Power supply 130 may comprise any conventional source of power suitable for such use, such as electrical, battery or pneumatic power. For powered operation, an activation switch 132 may be provided for activating the power supply, and/or for selectively converting device 110 between manual and power operation. Activation of the power supply causes rotation of drive gear 129. Due to the splined or like interconnection of drive gear 129 and striker flange 128, rotation of the drive gear causes rotation of the striker flange, which in turn, causes rotation of drive coil 116 and tip 118. Thus, those skilled in the art will appreciate that cutting tip 118, drive coil 116, flange retainer 127, flange 128 and drive gear 129 are rotationally engaged to one another in a manner such that they are axially and rotationally movable as a unit, which unit is freely movable within housing 112, outer sheath 117 and restrictor sleeve 119. As a result, when power supply 130 is activated, this inner assembly will rotate from the drive gear to the tip.
Thus, as described, device 110 is capable of selectively utilizing either manual or powered operation. Manual operation provides a hammer-like action wherein the tip is incrementally urged forwardly, and then withdrawn, in linear fashion. This action may be repeated as many times as desired. Powered operation provides rotary action to the tip. Depending upon the nature of the encapsulation of the lead encountered, some obstructions may respond better to the hammer-like action of the tip provided by manual operation, while others may respond better to the rotary tip action provided by the powered operation. In still other instances, the encapsulation may respond better to a sequential operation of, e.g., manual, and then power, operation, or vice versa. As a result, device 110 provides sufficient versatility to address numerous different encapsulation situations that may be encountered.
Although the embodiment of lead extraction device 110 described hereinabove includes the option of utilizing either manual or powered operation, or both, the device need not include both options. Thus, the device can be structured to provide only manual hammer-like operation, or only powered operation. When only manual operation is desired, power supply 130 may be eliminated, along with drive gear 129. In this event, only minimal structural modifications will be required to compensate for the lack of a drive gear. On the other hand, when only power operation is desired, the striker mechanism 121 may be eliminated.
A device for removing an implanted elongated structure, such as a cardiac lead, according to the present invention should have a length and flexibility such that it is capable of extending through enough of the body vessel to at least partially free the cardiac lead from the surrounding endothelial growth. For best results, the device will be structured such that torque can be transmitted by the operator from the proximal end to the “tipped” distal end of the device. In this manner, the operator need merely insert the sheath into the vessel, and thereafter direct, or torque, the sheath to the desired site to enable the teeth or other structure on the tip to cut or otherwise disrupt the growth surrounding the lead.
Distal tips for lead extraction devices are known in the art, and those skilled in the art can readily select a tip for use with the extraction devices described herein. Although many such tips are effective in some instances, such prior art tips often do not have the versatility to be used with a wide variety of devices, and often provide less effective cutting and/or disrupting action than desired. Accordingly, another feature of the present invention comprises novel tip structures that are intended for use in the inventive extraction devices described, as well as with other extraction and/or cutting devices that may utilize such tips.
When present, rings 56 are preferably aligned in order of increasing width of said ring body in the direction of the distal tip portion. Providing rings having a smaller width in the proximal direction minimizes the stresses in the sheath at the area of joinder of the sheath and the tip. At the area of joinder, stresses resulting from tension, torsion, and bending tend to be the highest. If desired, rings 56 may be provided with one or more cut-outs 58. Cut-outs 58 serve to hinder rotation of the tip when the proximal tip portion is positioned inside the distal portion of the sheath.
Although the preferred embodiment illustrated above comprises rings 56 for engagement with the inner surface of sheath 14, those skilled in the art will appreciate that other conventional attachment mechanisms may be substituted in a particular case. For example, rather than rings, the proximal end of tip 60 can be provided with one or more barbs along the proximal length of the tip, which barbs are configured to attach to the inner surface of the sheath. As another alternative, the proximal end of tip 60 can be provided with a roughened outer surface for facilitating attachment with the inner surface of the sheath by well-known means, such as adhesion. In this case, the outer surface of the cutting tip may be roughened by any conventional process, such as bead blasting and etching. As is well known, the use of a roughened outer surface enables an improved connection to be formed between the cutting tip and the sheath.
The radially outer projections, such as helices 59, on the distal portion of tip 60 function as disrupters of the body tissue encountered during insertion and rotation of the lead extraction device. Although the disruptors are shown in the figure as helices, this is only one example of a type of disrupter element that may be present on the tip portion. As alternatives, the disruptor may comprise linear, or non-linear segments, which segments may or may not be continuous, and may have any cross-sectional dimension. Similarly, the disruptor elements may point in any direction, or in no direction, in which the disrupter element can have a configuration such as a dot or a circle.
While disrupting the tissue, the disrupter elements urge the tissue to move in a direction which may be different from the direction of motion of the disrupter element. For example, a clockwise rotation of the tip, as viewed from the proximal end, would urge the tissue inside the tip to move in a distal direction, and the tissue at the tip to move outward (radially), for the embodiments shown in
Preferably sleeve 144 includes a serrated outer surface as shown in the figure. Sleeve 144 is preferably sized such that it has a slightly larger outer diameter than that of the (inner) sheath that receives proximal portion 146. This better accommodates a telescoping outer sheath, when present, and eases the advancement of the telescoping outer sheath through the area that has been opened by the tip. Advancement of the sleeve also obliterates the threaded pathway formed by the threads, thereby facilitating advancement of the device in the vessel. In addition, when the threaded pathway is obliterated in this manner, removal of the device is facilitated, since it is not necessary to reverse the threaded pathway to achieve removal.
Tip 150 in
Tip 160 in
The tips illustrated in
Those skilled in the art will appreciate that other compatible materials may be used in place of metal or metal alloys. For example, a fiber-reinforced polymer, such as fiber-reinforced polypropylene, may be used. Non-limiting examples of suitable fiber reinforcements include glass and carbon fibers. In an embodiment wherein the tip is formed as an integral portion of the sheath, the tip may conveniently be formed of a polymer, such as polypropylene, and may be molded onto the end of a sheath formed from a polymer that is compatible to the polymer of the tip material.
The inventive device may also include, or be used in combination with, other known features of medical devices. One non-limiting example is the use of the lead extraction device in combination with a tip-deflecting mechanism. As well known by those of skill in the art, a tip-deflecting mechanism is normally operated by activating a control at the proximal portion of the mechanism. Activation of the control causes the distal portion of the mechanism to deflect in a desired manner, thereby allowing the operator to preferentially curve certain areas of the device, or to change the orientation of the tip, or a portion of the tip, of the device. Thus, one possible use of the inventive device is to position the sheath and tip portion of the device inside a tip-deflecting mechanism. The sheath portion of the cutting tip rails the lead, and is deflected in accordance with the deflection of the tip-deflecting mechanism. As a variation of this embodiment, the tip-deflecting capability can simply be built into the cutting tip device, thereby eliminating the necessity to use a separate tip-deflecting mechanism.
The various sheaths described herein may be formed from conventional biocompatible materials well known for such purposes in the medical arts. Polymeric materials such polypropylene, polyurethane, polyethylene, nylon, PTFE, and the like, are believed to be particularly appropriate. Typically, such sheaths comprise an inner sheath and a telescoping outer sheath, and the inventive devices are readily adapted for use with such sheaths. If desired, a sheath can be reinforced with a coil or with a braided material. Such reinforcements are well known in the medical arts, and are typically formed from a metal or metal alloy. Preferably the striker flange and the sheath assembly flanges described hereinabove are formed from a biocompatible metal or metal alloy, such as titanium or stainless steel, or alternatively, a high impact plastic composite material. The outer housing is preferably formed from an acetal compound, or a polycarbonate material. The compositions described hereinabove are exemplary, and those skilled in the art will appreciate that other compositions may be substituted, such substitutions being within the scope of the invention.
If desired, selected portions of the lead extraction devices described herein, such as the tip portion, can be provided with means for x-ray or fluoroscopic vision. Such means are well known in the art, and may include, for example, the incorporation of a radiopaque band, or the inclusion of radiopaque particles in the selected portion. As still another alternative, the tip can be formed (in whole or in part) of a metal or metallic alloy to provide such visibility. In general, increased visibility of the tip is beneficial because it allows the operator to determine the location of the tip at a particular point in time, and also provides the operator with the ability to track the position and orientation of the tip with reference to the lead body.
Those skilled in that art will appreciate that the foregoing detailed description should be regarded as illustrative rather than limiting, and that it should be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.