US20110125163A1 - Implantable medical device system with fixation member - Google Patents

Abstract

A fixation device for a subcutaneous implantable medical device includes a deformable tip portion that reduces in width when coupled with a fixation tool such that implantation of the implantable medical device through tissue is facilitated. Upon release from the fixation tool, the fixation device returns to its initial shape and stably secures the position of the implantable medical device.

Description

RELATED APPLICATIONS
• This application is a continuation of U.S. patent application Ser. No. 12/038,906, filed Feb. 28, 2008 entitled “IMPLANTABLE MEDICAL DEVICE SYSTEM WITH FIXATION MEMBER”, herein incorporated by reference in its entirety.
• In addition, this application is related to, and claims the benefit of, provisionally-filed U.S. patent application Ser. No. 60/892,048, filed Feb. 28, 2007, and entitled “Implantable Medical Device System with Fixation Member”, which is incorporated herein by reference in its entirety.
TECHNICAL FIELD
• The invention relates generally to implantable medical devices and, in particular, to a fixation member for an implantable medical device.
BACKGROUND
• Implantable medical devices are often provided with a fixation member for maintaining the device at a desired location within a patient's body. For example, elongated medical devices such as catheters and electrical leads may include a fixation member at or near the distal end of the device for maintaining the position of the device at a targeted implant site. Fixation members can include active and/or passive fixation members, for example in the form of hooks, barbs, helices or tines.
• Implantable medical leads are used for deploying electrodes or physiological sensors to a targeted implant site. The lead carries electrical conductors allowing electrical connection of the deployed electrodes or sensors to a medical device such as a pacemaker, implantable cardioverter defibrillator, neurostimulator, or physiological monitor. Fluid delivery catheters may be used for delivering a fluid to a targeted body site to achieve an optimal effect. Fluid delivery catheters are generally coupled to a pump or other fluid dispensing device. A fluid delivered to a targeted site may be a dye used in a monitoring or diagnostic procedure, or a pharmaceutical agent or genetic or biological material for achieving a therapeutic effect. Reliable monitoring and/or therapy delivery by an implanted medical device is typically dependent on proper and stable positioning of the medical device. As such, many medical devices require a fixation member that reliably maintains the position of the device at a targeted body site without causing significant tissue trauma. In some cases, a delivery tool is needed for deploying the device to the targeted site.
• Depending upon the nature of the medical device, fixation may be permanent or temporary. Thus, the fixation mechanisms is selected accordingly. For example, a cardiac pacing/defibrillation lead is implanted for long term use and the fixation mechanism may be rather robust, such as a helical member screwed into tissue. Conversely, many catheters are inserted on a temporary basis. Thus, while important to secure these device in place as needed; it is also important to be able to remove and retract these devices from the human body without adverse consequence.
BRIEF DESCRIPTION OF THE DRAWINGS
• Aspects and features of the present invention will be appreciated as the same becomes better understood by reference to the following detailed description of the embodiments of the invention when considered in connection with the accompanying drawings, wherein:
• FIG. 1 depicts a patient implanted with a subcutaneous implantable cardioverter defibrillator.
• FIG. 2 is a plan view of the lead shown inFIG. 1.
• FIG. 3 is a plan view of a fluid delivery device including a fixation member.
• FIGS. 4A through 4C are plan views of various embodiments of a fixation member for use with an implantable medical device.
• FIG. 5A is a side view of the fixation member shown inFIG. 4A.
• FIG. 5B is a plan view of a fixation member including material for promoting tissue ingrowth.
• FIG. 6A is a cross-sectional view of a fixation member side.
• FIG. 6B is a cross-sectional view of a fixation member side in an alternative embodiment.
• FIGS. 7 and 8 are plan views of alternative embodiments of a fixation member for use with a medical device.
• FIGS. 9 and 10 are perspective views of alternative embodiments of a fixation member.
• FIG. 11 is a top plan view of a medical device having a fixation member.
• FIG. 12 is a side plan view of the medical device shown inFIG. 11.
• FIG. 13 is a side plan view andFIG. 14 is a top plan view of a medical device delivery tool.
• FIGS. 15 and 16 are top plan views of a medical device including a fixation member being mounted on the delivery tool shown inFIGS. 13 and 14.
• FIG. 17 is a top plan view of a distal portion of the fixation member mounted on the delivery tool shown inFIG. 16.
• FIGS. 18 and 19 are side and top views, respectively, of a delivery tool distal portion having an alternative release mechanism used for releasing a fixation member from the delivery tool.
• FIGS. 20 and 21 are side and top views, respectively, of the distal portion of the delivery tool shown inFIGS. 18 and 19 wherein the release mechanism has been actuated to release the fixation member from the delivery tool.
• FIG. 22 is a side sectional view of an alternative embodiment of a delivery tool release mechanism.
• FIGS. 23 and 24 are side and top views, respectively, of an alternative embodiment of a delivery tool.
DETAILED DESCRIPTION
• In the following description, references are made to illustrative embodiments for carrying out the invention. It is understood that other embodiments may be utilized without departing from the scope of the invention. For purposes of clarity, the same reference numbers are used in the drawings to identify similar elements. Unless otherwise noted, drawings referred to herein are not shown to scale.
• Embodiments of the invention include implantable medical device systems wherein an implantable medical device is provided with a fixation member for maintaining a stable implant position. Such systems will typically include an elongated medical device, such as an electrical lead or a fluid delivery catheter, that is tunneled or advanced to a targeted implant site for monitoring physiological signals and/or delivering a therapy. Embodiments of a medical device system include a delivery tool used to deploy the elongated medical device to the target site. Exemplary applications of various embodiments include implantable pacemaker systems, implantable cardioverter defibrillator systems, implantable neurostimulator systems, implantable drug delivery systems, implantable physiological monitoring systems or any other implantable medical device system relying on stable fixation of a medical device at an implant site. Implant sites may be subcutaneous sites, sub- or intramuscular sites, within the brain cavity, thoracic cavity, pleural cavity, within an organ wall, within a lumen of a vessel or organ, or any other internal body site.
• FIG. 1 depicts apatient6 implanted with a subcutaneous implantable cardioverter defibrillator (SubQ ICD)4. SubQ ICD4 is coupled to an implantablemedical lead10.Lead10 includes anelongated lead body12 including acoil electrode20 andlead10 is adapted for subcutaneous implantation.Lead10 includes afixation member22 for maintaining the position ofcoil electrode20 at a desired body site. InFIG. 1, SubQ ICD4 is implanted in an anterior position relative to the patient's heart8. The housing9 of SubQ ICD4 is used in conjunction withsubcutaneous coil electrode20 for delivering high-voltage shocks to the patient's heart. SubQ ICD4 includes electrodes7 that are used for sensing electrical signals from the heart such as, for example, to detect ventricular arrhythmias that need to be shocked. Leadbody12 is passed through a subcutaneous tunnel disposed laterally along the patient's chest wall, toward the patient'sspine5 to positioncoil electrode20 posteriorly, relative to the heart8.Fixation member22 maintains the position ofcoil electrode20 in the posterior position such that appropriate shocking vectors can be established between SubQ ICD4 andcoil electrode20 relative to heart8 to enable successful cardioversion/defibrillation of heart8. SubQ ICD4 and associatedlead10 illustrate one implantable medical device system in which embodiments of the present invention may be implemented.
• FIG. 2 is a plan view of thelead10 shown inFIG. 1.Lead10 includes elongatedlead body12 extending between aproximal end14 and adistal end16. Leadbody12 is typically fabricated from a flexible insulative material including one or more lumens for carrying conductors (not shown) extending betweenproximal end14 anddistal end16. Aconnector assembly18 atproximal end14 facilitates electrical connection oflead10 to an associated medical device, such as SubQ ICD4 shown inFIG. 1. One or more electrodes and/or physiological sensors are positioned alonglead body12, at or near distallead body end16. In the embodiment shown inFIG. 2, acoil electrode20 used in delivering high energy shock pulses for cardioverting or defibrillating the heart is positioned alonglead body12 neardistal end16.
• In other embodiments, lead10 may be adapted for use with other implantable medical devices such as pacemakers, neurostimulators, physiological monitors or the like. As such, it is recognized thatlead10 may be adapted for carrying additional electrodes and/or other physiological sensors.Lead10 may include additional coil electrodes, and/or lead10 may include one or more ring electrodes used for sensing and/or stimulation. Other sensors carried bylead10 may include temperature sensors, motion sensors, pressure sensors, electrodes for measuring impedance, oxygen sensors, etc.
• Afixation member22 is coupled to the lead bodydistal end16 for maintaining a stable position of lead bodydistal end16 upon deployment oflead10 to an implant site.Fixation member22 includes afirst side24 and asecond side26.First side24 andsecond side26 converge to form adistal tip28. Aproximal base30 extends betweenfirst side24 andsecond side26 along aproximal end32 offixation member22.Fixation member22 is generally tapered such that thedistance40 betweenfirst side24 andsecond side26 nearbase30 is greater than thedistance42 betweenfirst side24 andsecond side26 neardistal tip28.Fixation member22 is shown to be generally triangular in shape having substantially straight first andsecond sides24 and26, which converge to formdistal tip28.
• First side24 andsecond side26 form anaperture34 therebetween for receiving a delivery tool used for tunneling and advancinglead10 to a targeted implant site.Fixation member22 further includes areceptacle36 for receiving lead bodydistal end16 to enablefixation member22 to be coupled to lead bodydistal end16.
• FIG. 3 is a plan view of a fluid delivery device including a fixation member.Fluid delivery device50 is embodied as a catheter including anelongated body52 forming alumen54 extending between aproximal end56 anddistal end58 ofbody52. A fitting60 is provided atproximal end56 to enable coupling ofdevice50 to a fluid pump, syringe or other fluid dispensing device.Fixation member62 is provided at catheter bodydistal end58 for maintaining the position ofdistal end58 at a desired body site.
• Fixation member62 includes afirst side64 and asecond side66, which converge to form adistal tip68, forming anaperture74 therebetween for receiving a delivery tool adapted for advancingfluid delivery device50 to a desired body site.Fixation member62 is shown to be generally triangular in shape and includes aproximal base70 extending betweenfirst side64 andsecond side66 at fixation memberproximal end72.Fixation member62 further includes areceptacle76 for receiving catheter bodydistal end58 to facilitate coupling offixation member62 tocatheter body52.Receptacle76 may include alumen78 in communication withlumen54 ofcatheter body52 and aport80 adapted to dispense a fluid flowing throughlumens54 and78 to a targeted body site. Other apertures or ports may be provided alongcatheter body52 in fluid communication withlumen54 for dispensing a fluid.Fluid delivery device50 may be used for delivering dyes, pharmaceutical solutions, or biological or genetic material.
• Although not shown, it is recognized thatfluid delivery device50 may include electrodes or other sensors positioned alongcatheter body52 and coupled to insulated conductors extending withincatheter body52. Likewise, it is recognized that thelead10 shown inFIG. 2 could include a delivery lumen in communication with delivery port for delivering fluids or other medical devices.
• FIG. 4A is a plan view of afixation member100 for use with an implantable medical device.Fixation member100 is coupled to thedistal end120 of an elongatedmedical device124 to provide stable fixation of the medical devicedistal end120 at a desired body location.Receptacle112 offixation member100 includes abore114 adapted to receive distalmedical device end120. In one embodiment,distal end120 is press fit withinbore114 and may be secured with an adhesive, such as silicone medical adhesive, to fixedly attachdistal end120 withinreceptacle112. In other embodiments, bore114 and medical devicedistal end120 are provided with interlocking members or other features for providing a stable mechanical coupling ofbore114 with medical devicedistal end120. In the embodiment shown inFIG. 4A, bore114 includes agroove116 adapted to mate with aflange122 extending radially from medical devicedistal end120.Flange122 and groove116 are adapted to allow medical devicedistal end120 to be advanced intobore114 untilflange122 and groove116 interlock and thereafter act to retain medical devicedistal end120 withinreceptacle112. Coupling betweenreceptacle112 and medical devicedistal end120 may be further stabilized by using an adhesive, such as a silicone medical adhesive. It is recognized that other interlocking or mating structures may be provided to promote a stable mechanical junction betweenfixation member100 and medical devicedistal end120. In alternative embodiments,fixation member100 may be molded onto medical devicedistal end120.
• Fixation member100 is formed from a resilient, biostable, polymeric material, such as a medical grade silicone rubber. In one embodiment, fixation member is molded from silicone rubber having a70 durometer Shore A hardness. Appropriate silicone rubber materials are available from NuSil Technology, Carpinteria, Calif. As will be further described below,fixation member100 is mounted on a delivery tool which is used to advancefixation member100 to a desired body site.Fixation member100 is configured to withstand tunneling forces required during an implant procedure and stretching that may be applied to mount fixation member on the delivery tool.Fixation member100 is further configured to have a bending flexibility that allows it to wrap around and narrowly conform to the delivery tool during advancement to an implant site. However, the bending flexibility is balanced with a stiffness and resiliency needed to causefixation member100 to resume its previous shape upon release from the delivery tool and to retain that shape during body movement. Various aspects offixation member100 that allowmember100 to be designed with a desired tensile strength, stiffness and bending flexibility for optimal performance will be further described herein.
• Fixation member100 includes adelivery tool aperture106 formed byfirst side102 andsecond side104.Distal tip105 is shown to be a generally rounded, atraumatic tip. However, it is recognized that in alternative embodiments,tip105 may be provided as a sharper or pointed tip to facilitate tunneling through tissue to an implant site. In some embodiments tip105 may be formed having a greater stiffness to withstand tunneling forces. Once positioned at a targeted site, the width offixation member100 alongproximal base108 inhibits retraction or dislodgment offixation member100 away from the target site.
• Base108 may be provided withbarbs117 and118 extending in a generally proximal direction to inhibit retraction offixation member100 from a desired implant site.Barbs117 and118 also inhibit retraction or dislodgment offixation member100 and act to prevent curling or flexing of fixation member, thereby maintaining fixation member in a generally flat configuration.
• Base108 is shown as an arcuate segment, curving slightly inward towarddistal tip105. Body motion, such as movement associated with respiration or activity, may cause tugging onelongated body120. Proximal tension applied tofixation member100, e.g. tugging onelongated body120 that may occur with body motion, will initially cause theproximal end140 of fixation member to widen from anormal width142 to anextended width144. Widening ofproximal end140 is caused by the straightening ofarcuate base108, as indicated by dashedline115, and the resultant outward flexing ofbarbs117 and118 as proximal tension is applied byelongated body120. Adistance146 betweenfirst side102 andsecond side104 in a relaxed state initially increases to agreater distance148 in response to proximal tension. This initial widening offixation member100 in response to applied tension inhibits retraction or dislodgment ofmember100 from the implant site.
• Application of greater proximal tension causesfixation member100 to elongate and narrow. As such, if retraction offixation member100 is required, greater proximal tension may be used to retractfixation member100. In one embodiment,fixation member100 is designed to withstand a retraction force of approximately 2 Newtons prior to becoming dislodged from a subcutaneous implant location.
• Fixation member100 includes support beams110 extending betweenfirst side102 andbase108 and betweensecond side104 andbase108. Support beams110 serve to support first andsecond sides102 and104 andbase108 in a generally flat profile after implantation, i.e. beams110 act to reduce bending or flexing offixation member100 after implantation.
• It is recognized that a fixation member may be provided with alternative base configurations in various embodiments of the invention. InFIG. 4B, a base108′ offixation member100′ is shown having an inverted “V” shape.Base108′ extends inward towarddistal tip105′. In this configuration, proximal tension applied to base108′ will cause initial widening offixation member100′ asbase108′ is straightened in response to the proximal tension.
• InFIG. 4C, a base108″ offixation member100″ is shown having a “V” shape. Proximal tension applied to base108″ will cause narrowing offixation member100″ as it is stretched over a delivery tool for advancement to an implant site.Barbs117″ and118″ may be provided which flex slightly outward in response to proximal tension causing an initial widening offixation member100″.
• FIG. 5A is a side view offixation member100 shown inFIG. 4A.Fixation member100 has a generally flat profile. As described above,fixation member100 includes first side102 (not visible in the side view ofFIG. 5),second side104,distal tip105,proximal base108 havingbarb118 and areceptacle112 forming abore114 for receiving a medical device distal end. The flat profile allows stable fixation of a medical device in a subcutaneous position while minimizing patient discomfort. To reduce bending or flexing offirst side102,second side104 andbase108 after implantation,base108 is provided with agreater thickness130 than thethickness132 ofsides102 and104. A greater stiffness ofbase108, corresponding to its greater thickness, helps to maintain the flat, generally triangular shape offixation member100. As will be described in greater detail below, the greater stiffness ofbase108 also supports expansion of fixation member from a stretched and rolled or wrapped configuration when mounted on a delivery tool to an expanded, generally flat configuration upon release from the delivery tool. Relativelythinner sides102 and104 facilitate easier mounting and releasing from the delivery tool and allow for an overall smaller size offixation member100 and an associated delivery tool. A smaller sized fixation member and smaller delivery tool will generally cause less tissue trauma. The thickness and stiffness ofbase108 relative tosides102 and104 may be designed according to a particular application for achieving desired tensile strength and bending stiffness offixation member100.
• Fixation member100 is shown havingmaterial134 coupled alongside104.Material134 is provided to promote tissue adhesions to further promote stable fixation ofmember100.Material134 may be provided as a mesh or porous material that encourages tissue ingrowth. In one embodiment,material134 is provided as polyethylene terephthalate fiber material (Dacron®, available from DuPont).
• FIG. 5B is a plan view of a fixation member including additional material for promoting tissue ingrowth. In addition to, or alternatively to, providing a material covering a portion of the fixation member for promoting tissue adhesion,material136 may be provided extending between any offirst side137,second side138,base139 and/or supportbeams141 of afixation member135.Material136 increases the stiffness offixation member135 which will improve the stable fixation ofmember135 at an implant site acutely. By promoting tissue ingrowth,material136 improves chronic stability of the fixation member at the implant site.
• FIG. 6A is a cross-section of fixation memberfirst side102 along view A-A shown inFIG. 4A. The cross-sectional shape ofsides102 and104 andbase108 may be generally quadrilateral as shown, for example, inFIG. 6A. In particular,side102 is shown having a rectangular cross-section withsquared corners154.Squared corners154 are expected to reduce slippage offixation member100 after implantation in comparison to rounded corners. Moreover, providing first andsecond sides102 and104 with a quadrilateral cross-section allowsfixation member100 to be designed with a desired balance between tensile strength and bending stiffness. The balance between tensile strength and bending stiffness is controlled by adjusting thethickness150 and thewidth152 of side102 (andsecond side104 and base108). A rectangular cross-section allows better control over the balance of tensile strength and flexibility than a circular cross-section. For example the flexibility ofside102 can be increased by reducingthickness150 while the tensile strength can be increased by increasingwidth152. However, it is recognized that the cross-sectional shape ofsides102 and104 as well asbase108 may include one or more rounded corners. For example,side102′ is shown to be generally D-shaped inFIG. 6B. In still other embodiments,sides102 and104 andbase108 may be generally circular or oval in cross-section.
• It is contemplated that numerous configurations for a fixation member having first and second sides converging to form a distal tip and forming a delivery tool aperture there between may be conceived. In alternative embodiments the first and second sides may include curved (concave or convex) and parallel segments, or any combination of thereof. For example, as shown inFIG. 7,fixation member200 includessides202 and204 each having generally straight,parallel segments206 and210, respectively, and generally curvedsegments208 and212, respectively.Curved segments208 and212 converge to formdistal tip214.
• In some embodimentsdistal tip214 may include a rigid plastic or metal material.Distal tip214 is shown inFIG. 7 having a rigidpointed cap216 for facilitating tunneling offixation member200 to an implant site.Rigid cap216 may be formed of a relatively stiffer silicone rubber, a rigid polymer, or a metal. In some embodiments, a rigid material is coupled to first andsecond sides202 and204 as they converge to form a rigid distal tip.
• Support beams extending between the first and second sides and the proximal base may also be provided in a variety of configurations. InFIG. 7, a “Y” shapedsupport beam222 extends between each ofsides202 and204 andbase218. Anaperture230 is formed bysides202 and204 andsupport beam222 for receiving a delivery tool.
• The shape and size of barbs provided on the proximal base may also vary.Base218 is provided withrounded barbs220 extending in a generally proximal direction.
• InFIG. 8,fixation member250 includes convex first andsecond sides252 and254 which converge to formdistal tip256. Asupport beam262 extends betweendistal tip256 andbase258.Base258 includes pointedbarbs260 extending in a generally proximal direction for inhibiting retraction offixation member250.Apertures264 and265 are formed bysupport beam262 andside252 andside254, respectively. One or bothapertures264 and265 may be adapted to receive a delivery tool.
• Fixation member250 may be provided as a splittable member having one or more break points indicated bylines272 and270.Fixation member250 is designed to have a tensile strength that withstands the pushing forces needed totunnel fixation member250 to a desired implant site when mounted on a delivery tool. In some situations, retraction of the medical device andfixation member250 is required. In order to facilitate retraction offixation member250,fixation member250 is provided with a relativelyweaker break point272 or270. Upon applying a retraction force exceeding the tensile strength offixation member250 across thebreak point272 or270,fixation member250 will split along thebreak point270 or272. Abreak point272 provided alongdistal tip256, or along eitherside252 and254, will allowfixation member250 to split, then elongate and collapse inward as it is retracted through a tissue tunnel.
• Alternatively, abreak point270 may be provided alongreceptacle274, at a point distal to the coupling betweenfixation member256 and a medical device.Break point270 would allow thereceptacle274 to split from the remaining portion offixation member250. Upon retraction of the medical device,fixation member250 would be left behind at the implant site.Fixation member250 could then be removed from a subcutaneous position via a small incision if desired.Break points270 and272 may be formed, for example, as splittable seams, perforated lines, or as a narrowed outer diameter to create a weakened tensile strength across the break point relative to the remaining portions offixation member250.
• In some embodiments,fixation member250 is provided with radio-opaque markers280 to allow visualization offixation member250 after implantation. Radio-opaque markers280 may be used to verify the location offixation member250 during the implant procedure. Iffixation member250 is provide with abreak point272 alongreceptacle274 and is left behind after retracting the associated medical device, radio-opaque markers280 may be used to locatefixation member250 for surgical removal.
• Depending on the specific application,fixation member100 may alternatively be formed having a more three-dimensional geometry rather than the substantially planar, low-profile geometries described above.FIG. 9 illustrates a fixation member300 having a generally pyramidal shape, includingmultiple sides302,304,306 and308 converging to formdistal tip310. Fixation member300 includesmultiple base segments312,314,316,318 and320 extending between respective pairs ofsides302,304,306 and308.Sides304 and306 form anaperture322 for receiving a delivery tool.Sides304 and306 are not joined by a base segment to allow more room for a delivery tool to be inserted intoaperture322. Areceptacle324 extends proximally from the intersection ofbase segments316 and318 for receiving a medical device distal end.
• FIG. 10 is a perspective view of an alternative embodiment of afixation member350.Fixation member350 is formed having first andsecond sides352 and354 which converge to fromdistal tip356.Sides352 and354 form a portion of a hemisphere and are narrower neardistal tip356 and wider nearproximal base358.Sides352 and354 form anaperture362 there between for receiving a delivery tool. Areceptacle360 extends proximally frombase358 for receiving a medical device distal end to allow coupling offixation member350 to the medical device. It is recognized that a variety of geometries for a fixation member may be conceived, including generally conical, pyramidal, or hemispherical shapes.
• FIG. 11 is a top plan view of amedical device400 having afixation member410. Fixation members provided according to various embodiments of the invention will generally be coupled to a distal end of an elongated medical device. However, according to an embodiment of the present invention, afixation member410 may be coupled at other points along an elongated body, or along other features of a medical device. For example, as illustrated inFIG. 11, amedical device400 includes anelongated body402 having adistal end404.Fixation member410 includes afirst side412 andsecond side414, which converge to form adistal tip420, and form adelivery tool aperture422 there between. Aproximal base418 extends between first andsecond sides412 and414. Areceptacle416 extends proximally frombase418 and is coupled tomedical device body402 at a location proximal todistal end404.
• FIG. 12 is a side plan view of themedical device400 shown inFIG. 11 havingfixation member410.Receptacle416 is offset from the plane ofbase418 andsecond side414 such thatfixation member410 can be coupled alongelongated body402, proximal todistal end404.Fixation member410 is offset from and extends substantially parallel toelongated body402. It is recognized thatfixation member410 may alternatively be offset from and oriented at other angles with respect toelongated body402.
• The various embodiments of a fixation member described herein include an aperture for receiving a delivery tool.FIG. 13 is a side plan view andFIG. 14 is a top plan view of a medicaldevice delivery tool500.Delivery tool500 may be used for deploying a medical device having a fixation member as described above.Delivery tool500 includes ashaft502 which may be provided as a malleable shaft formed of stainless steel.Shaft502 extends between aproximal end504 and adistal end506. Ahandle510 is provided atproximal end504 for maneuveringshaft502 during an implant procedure. Adelivery tool head520 is provided at shaftdistal end506 for carrying a medical device during an implant procedure. In particular,delivery tool head520 is adapted for carrying a fixation member coupled to an elongated medical device.
• Delivery tool head520 includes adistal tunneling tip522 that is generally pointed for facilitating tunneling oftool500 through body tissues to an implant site.Tunneling tip522 may be rounded to reduce tissue trauma or more pointed to cut more easily through tissues thereby reducing the pushing force needed to advancedelivery tool500.
• Delivery tool head520 includes a mountingportion525 for carrying a fixation member of a medical device. Mountingportion525 is provided with agroove524 extending along each side of mountingportion525 and aroundtunneling tip522.Groove524 receives a medical device fixation member as will be further described below.Delivery tool head520 includes a narrowedneck portion527 extending proximally from mountingportion525.Narrowed neck portion527 allows a medical device fixation member to wrap arounddelivery tool head520 such that the fixation member andhead520 become approximately isodiametric during advancement to an implant site.
• Delivery tool head520 further includesrestraint526 for retaining a portion of the medical device fixation member carried bytool head520.Restraint526 is designed to releasably hold a portion of the medical device fixation member. As will be further described below, a fixation member is stretched over mountingportion525 with the fixation member proximal base held byrestraint526.Restraint526 is designed to function as both a retaining and release mechanism.Proximal handle510 includes amechanical switch512 for controllingrestraint526. In one embodiment, activation ofswitch512 from a first position514 (as shown) to a second position516 (indicated by dashed line) actuatesrestraint526 from a retaining position540 (as shown) to a release position542 (indicated by dashed line). Activation ofswitch512 causes a rotation ofrestraint526 via a pull wire (not shown). The rotation ofrestraint526 pushes the fixation member proximal base up and away fromdelivery tool head520. In alternative embodiments,delivery tool head520 may include separate restraint and release mechanisms.
• Switch512 is a bistable switch in some embodiments in which a firststable position514 corresponds to retaining a fixation member ondelivery tool head520 and a secondstable position516 corresponds to releasing the fixation member from the delivery tool head.Switch512 may alternatively be provided as a monostable switch having a stable position corresponding to retaining the fixation member and provides tactile or audible feedback corresponding to the release of the fixation member from the delivery tool head. The circumferential position ofswitch512 onhandle510 can also serve as an indicator of the orientation ofdelivery tool head520.
• Shaft502 may be formed with a contoured outer surface, e.g. aconcave surface530, for accommodating an elongated body of the medical device. The length and cross-sectional contour ofshaft502 may vary depending on the particular application.Shaft502 further includes one ormore flanges532 and534 for maintaining the position of the elongated body alongshaft502 and inhibiting rotation or twisting of the elongated body of a medical device extending alongshaft502.Flanges532 and534 do not limit longitudinal movement (along the tool axis) of the elongated body relative to theshaft502. As such,flanges532 and534 do not form a tight fit with the elongated body and provide a space therebetween so as to readily release the elongated body fromtool500 upon release of the fixation member fromdelivery tool head520. However, it is contemplated that in some embodiments,flanges532 and534 may retain the elongated body for inhibiting longitudinal movement (along the tool axis) of the elongated body relative toshaft502 as well as rotational movement.Shaft502 further includes astop surface528 for interfacing with a surface of the medical device to prevent over-stretching of the fixation member carried bydelivery tool head520 as will be further described below.
• FIGS. 15 and 16 are top plan views of amedical device550 including afixation member560 being mounted on thedelivery tool500 shown inFIGS. 13 and 14.Delivery tool shaft502 is shown inFIG. 15 having a pre-shaped curve or bend518.Shaft502 may be provided having one or more pre-shaped bends or curves to facilitate advancement ofdelivery tool500 to an implant site. The particular configuration ofshaft502 may be selected according to the intended application.
• InFIG. 15,fixation member560 is shown in an unstretched, normal state.Fixation member560 includes afirst side562 and asecond side564 which converge to form adistal tip566.First side562 andsecond side564 form adelivery tool aperture572 for receivingdelivery tool head520.Fixation member560 includesproximal base568 extending betweenfirst side562 andsecond side564.Base568 is provided withbarbs580. Areceptacle570 extends proximally frombase568. Adistal end554 of medical device elongatedbody552 is coupled toreceptacle570.
• Delivery tool head520 is inserted throughfixation member aperture572, and fixation memberdistal tip566 is positioned in the groove524 (shown inFIG. 13) of mountingportion525. Medical device elongatedbody552 extends alongdelivery tool shaft502, resting alongconcave surface530.Flanges532 and534 inhibit rotation or twisting ofelongated body552 relative toshaft502.
• InFIG. 16,fixation member560 is shown in a stretched state, positioned ondelivery tool head520 for advancement to an implant site.Base568 is stretched proximally by pullingmedical device550 back towardproximal end504 ofshaft502 withdistal tip566 positioned withingroove524 of mountingportion525 and held in the stretched position byrestraint526. In the stretched position,fixation member560 becomes elongated and narrower to facilitate tunneling through tissue to an implant site. A distance590 (FIG. 15) between first andsecond sides562 and564 alongbase568 in relaxed state is reduced to a shorter distance592 (FIG. 16) upon stretchingfixation member560 overdelivery tool head520. First andsecond sides562 and564 reside ingroove524 of mountingportion525. Fixation memberdistal tip566 andsides562 and564 protrude slightly fromgroove524 of mountingportion525. It is recognized that in some embodiments, fixation memberdistal tip566 and first andsecond sides562 and564 may reside entirely withingroove524 of mountingportion525.Groove524 is sized to form a snug fit withfixation member560 to preventfixation member560 from falling offdelivery tool head520 and to prevent tissue from becoming pinched betweendelivery tool head520 andfixation member560 during advancement to an implant site. Fixation memberdistal tip566 andsides562 and564 are protected withingroove524 during advancement to a tissue site.
• Fixation member560, being stretched over delivery tool head, becomes narrower to facilitate tunneling to an implant site.Restraint526 maintains the tension offixation member560 to keepmember560 from falling off the delivery tool head. In one embodiment,fixation member560 is stretched to approximately 120% to 200% of its normal length when mounted ondelivery tool head520. In the stretched position, aproximal face574 ofreceptacle570 interfaces withstop surface528 to prevent overstretching offixation member560. In some embodiments,restraint526 is optional and stretching offixation member560 may be accomplished by an implanting clinician maintaining tension on the proximal end of the elongatedmedical device550. Thestop surface528 prevents the clinician from overstretchingfixation member560.
• FIG. 17 is a top plan view of a distal portion of thefixation member560 mounted on thedelivery tool500 shown inFIG. 16. As thetunneling tip522 ofdelivery tool500 is tunneled through tissue to a desired implant site, sides562 and564 offixation member560 fold in around narrowedneck portion527 ofdelivery tool head520.Fixation member560 thus becomes substantially isodiametric withdelivery tool head520. Asdelivery tool head520 andfixation member560 are tunneled to an implant site a relatively narrow passage through the tissue is formed. A smaller diameter of the delivery tool head with a mounted fixation member will generally require lower tunneling forces. Upon release offixation member560 fromdelivery tool head520,fixation member520 regains its normal shape. As described previously,fixation member base568 is formed with a greater stiffness thansides562 and564 such thatbase568 will straighten upon release fromtool500 and thereby act to restore the generally triangular shape offixation member560. Thewide base568 offixation member560 andbarbs580 will inhibit the retraction ofmember560 back through the narrow tissue tunnel formed bydelivery device500.
• FIGS. 18 and 19 are side and top views, respectively, of a delivery tool distal portion having an alternative release mechanism used for releasing a fixation member from the delivery tool. Amedical device620 is shown mounted ondelivery tool600.Medical device620 includes anelongated body622 coupled to areceptacle632 offixation member630. First and second sides offixation member630 are not shown for the sake of clarity in illustrating therelease mechanism604.Delivery tool600 includes ashaft610 anddelivery tool head601.Delivery tool head601 includes arestraint602 for retaining thebase634 offixation member630 in a stretched position.
• Release mechanism604 is embodied as a lever coupled to anactuation member606, embodied as a push-pull rod.Actuation member606 extends to a proximal handle ofdelivery tool600 where it is attached to a mechanical switch (not shown) used to actuaterelease mechanism604 viaactuation member606.Restraint602 includes a groove603 (FIG. 19) to allow longitudinal movement (along the tool axis) ofrelease mechanism604, toward and away frombase634.
• FIGS. 20 and 21 are side and top views, respectively, of the distal portion of thedelivery tool600 shown inFIGS. 18 and 19 wherein the release mechanism has been actuated to releasefixation member630 fromdelivery tool600. Actuation ofrelease mechanism604 by a switch coupled toactuation member606 causesrelease mechanism604 to slide proximally towardbase634.Base634 will be stretched slightly further byrelease mechanism604 and pushed upward, as indicated by the arrow inFIG. 20, untilbase634 is released fromrestraint602.Fixation member630 will then slip offdelivery tool head601 allowing tool head to be retracted and removed and leavingfixation member630 at the implant site.
• FIG. 22 is a side sectional view of an alternative embodiment of a delivery tool release mechanism. An actuation member may alternatively be provided in the form of apull wire652 andspring member654 instead of a push-pull rod as shown inFIGS. 18-21A. Tension applied to pullwire652 by way of a proximal switch will pullrelease mechanism650 proximally to releasefixation member630 from restraint660.Spring member654 will returnrelease mechanism650 back, distally, to its normal position corresponding to retaining a fixation member by restraint660.Spring member654 may be formed as a metal or polymer spring or an elastic element. In some embodiments,release member650 may be designed having elastic properties that causerelease member650 to return to a normal position when not activated bypull wire652.
• While particular embodiments of release mechanisms have been shown and described herein, it is recognized that numerous delivery tool configurations may be conceived which enable restraint and release of a fixation member. Such arrangements may include a lever, spring, rod, or other member actuated by a mechanical switch for longitudinal or rotational movement that causes release of a medical device fixation member from the delivery tool. The particular details of such mechanisms may vary widely but such variations are considered within the scope of the present invention.
• FIGS. 23 and 24 are side and top views, respectively, of an alternative embodiment of a delivery tool.Delivery tool700 includes a mountingportion725 positioned proximal totunneling tip722.Delivery tool700 includes ashaft702 having a contouredsurface730 for accommodating an elongated body of a medical device (not shown inFIGS. 23 and 24).Shaft702 includesflanges732 and734 for inhibiting rotation and lateral movement of the medical device relative toshaft702 and astop surface728 to prevent over-stretching of a fixation member mounted ondelivery tool700.
• Delivery tool700 further includes adelivery tool head720 having adistal tunneling tip722, a mountingportion725 spaced proximally from tunnelingtip722 and a narrowedneck portion727 extending towardshaft702. Arestraint726 is provided for maintaining a fixation member in a stretched position when the fixation member is mounted alonggroove724 of mountingportion725 as described previously. A fixation member mounted ondelivery tool head720 is not exposed to the tunneling forces met by tunnelingtip722.
• Thus, a medical device system including an implantable medical device having a fixation member and a delivery tool used for deploying the device have been presented in the foregoing description with reference to specific embodiments. It is appreciated that various modifications to the referenced embodiments may be made without departing from the scope of the invention as set forth in the following claims.

Claims (24)

1. An implantable medical device system, comprising:

an elongated implantable medical device;

means for fixing a distal end of the medical device at a targeted implant site, and

means for advancing the distal end of the medical device to the targeted implant site;

wherein the advancing means includes means for mounting the fixing means, the fixing means being releasably coupled to the mounting means in a stretched position; and

wherein the advancing means comprises an elongated shaft extending exterior to and alongside the elongated medical device.

2. The implantable medical device system ofclaim 1, wherein the advancing means further includes restraining means for retaining the fixing means on the mounting means.

4. The implantable medical device system ofclaim 1 further including means for preventing overstretching of the fixing means when mounted on the advancing means.

5. The implantable medical device system ofclaim 1, wherein the mounting means includes means for tunneling through tissue.

6. The implantable medical device system ofclaim 1, wherein the fixing means includes an aperture for receiving the advancing means.

7. The implantable medical device system ofclaim 1, wherein the elongated shaft has at least one preformed curve.

8. The implantable medical device system ofclaim 1, wherein the mounting portion includes means for tunneling through tissue.

9. The implantable medical device system ofclaim 1, wherein the mounting portion includes a groove adapted to receive the fixation member.

10. The implantable medical device system ofclaim 1, wherein the delivery tool further includes a release mechanism for releasing the fixation member from the delivery tool head.

11. The implantable medical device system ofclaim 10, wherein the delivery tool includes a handle at the shaft proximal end having a mechanical switch for actuating the release mechanism.

12. The implantable medical device system ofclaim 11, wherein the release mechanism includes a pulling member extending along the shaft for actuating the release mechanism.

13. The implantable medical device system ofclaim 12, wherein the release mechanism further includes a spring member for returning the release mechanism to a normal position after releasing the fixation member.

14. The implantable medical device system ofclaim 13, wherein the mechanical switch is adapted to have a first stable position corresponding to retaining the fixation member by the restraint and a second stable position corresponding to releasing the fixation member from the restraint.

15. The implantable medical device system ofclaim 1 wherein the delivery tool includes a head and a narrowed neck portion and wherein the fixation member is adapted to wrap around the narrowed neck portion to cause the fixation member to become approximately isodiametric with the delivery tool head.

16. The implantable medical device system ofclaim 1 wherein the delivery tool shaft includes a stop surface, and the fixation member includes a proximal face for interfacing with the stop surface to prevent overstretching of the fixation member when mounted on the delivery tool.

17. An implantable medical device system, comprising:

an elongated implantable medical device;

means for fixing a distal end of the medical device at a targeted implant site, and

means for advancing the distal end of the medical device to the targeted implant site;

wherein the advancing means and the fixing means are approximately isodiametric when the fixing means is coupled with the advancing means; and

wherein the advancing means comprises an elongated shaft extending exterior to and alongside the elongated medical device.

18. The implantable medical device system ofclaim 17, wherein the advancing means further includes restraining means for retaining the fixing means on the mounting means.

19. The implantable medical device system ofclaim 17, wherein the fixing means includes an aperture for receiving the advancing means.

20. The implantable medical device system ofclaim 17, wherein the mounting portion includes a groove adapted to receive the fixation member.

21. The implantable medical device system ofclaim 17, wherein the delivery tool further includes a release mechanism for releasing the fixation member from the delivery tool head.

22. The implantable medical device system ofclaim 21, wherein the delivery tool includes a handle at the shaft proximal end having a mechanical switch for actuating the release mechanism.

23. The implantable medical device system ofclaim 22, wherein the release mechanism includes a pulling member extending along the shaft for actuating the release mechanism.

24. The implantable medical device system ofclaim 23, wherein the release mechanism further includes a spring member for returning the release mechanism to a normal position after releasing the fixation member.

25. The implantable medical device system ofclaim 24, wherein the mechanical switch is adapted to have a first stable position corresponding to retaining the fixation member by the restraint and a second stable position corresponding to releasing the fixation member from the restraint.

Images