IMPLANTABLE MEDICAL LEAD
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional Patent Application 63/593,693 filed 27 October 2023, the entire content of which is incorporated herein by reference.
TECHNICAL FIELD
[0002] This disclosure is related to medical devices such as implantable medical leads.
BACKGROUND
[0003] Various types of implantable medical leads have been implanted for treating or monitoring one or more conditions of a patient. Such implantable medical leads may be adapted to allow medical devices to monitor or treat conditions or functions relating to heart, muscle, nerve, brain, stomach, endocrine organs or other organs and their related functions. Implantable medical leads include electrodes and/or other elements for physiological sensing and/or therapy delivery. Implantable medical leads allow the sensing/therapy elements to be positioned at one or more target locations for those functions, while the medical devices electrically coupled to those elements via the leads are at different locations.
[0004] Implantable medical leads, e.g., distal portions of elongated implantable medical leads, may be implanted at target locations selected to detect a physiological condition of the patient and/or deliver one or more therapies. For example, implantable medical leads may be delivered to locations within an atria or ventricle to sense intrinsic cardiac signals and deliver pacing or antitachyarrhythmia shock therapy from a medical device coupled to the lead. In other examples, implantable medical leads may be tunneled to locations adjacent a spinal cord or other nerves for delivering pain therapy from a medical device coupled to the lead. Implantable medical leads may include fixation components to secure a distal end of the lead at the target location.
SUMMARY
[0005] An implantable medical lead comprises includes a lead body supporting a fixation device (e.g., an auger or a helix) extending distal to the lead body. The lead body further supports a plurality of barbs configured to extend radially outward to engage tissues when the fixation device engages tissues. The lead body and the fixation device comprise biostable materials. The plurality of barbs comprise a biodegradable material. The biodegradable material may be a material configured to degrade when subjected to a fluid and/or biological constituent of the patient (e.g., blood and/or constituents of blood such as water, proteins, electrolytes, amino acids, salts, enzymes, hormones, and/or other constituents). For example, the biodegradable material may be configured to degrade when subjected to the fluids and/or biological constituents of a patient for a period less than about 6 months, in some examples less than 3 months. The biostable material may be configured to substantially maintain its physical and chemical integrity when implanted within tissues of the patient.
[0006] In an example, an implantable medical lead comprises: a lead body comprising a biostable material defining an outer surface and a distal end, wherein the lead body defines a longitudinal axis surrounded by the outer surface and extending through the distal end; a fixation device supported by the lead body and extending distal to the distal end, wherein the fixation device is configured to insert within tissues of a patient; and a plurality of barbs supported by the outer surface and proximal to the fixation device, wherein the plurality of barbs is positioned around the longitudinal axis, wherein the plurality of barbs are configured to extend radially outward from the outer surface, wherein the plurality of barbs are configured to engage the tissues when the plurality of barbs are inserted into the tissues, and wherein the plurality of barbs comprise a biodegradable material configured to degrade in a fluid of the patient.
[0007] In an example, a technique comprises: defining, using a biostable material, an outer surface of a lead body surrounding a longitudinal axis of the lead body and a distal end of the lead body; supporting, using a distal end of the lead body, a fixation element configured to engage tissues; defining, using a biodegradable material, a plurality of barbs supported by the outer surface and proximal to the fixation device; and extending, using a resilient biasing of the plurality of barbs, the plurality of barbs radially outward from the outer surface.
[0008] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a conceptual diagram illustrating an example implantable medical lead implanted at an example target site.
[0010] FIG. 2 is a perspective view illustrating an example lead distal portion.
[0011] FIG. 3 is an schematic end view of the lead distal portion of FIG. 2.
[0012] FIG. 4 is schematic cross-sectional view of a lead body supporting a plurality of barbs in a stowed position.
[0013] FIG. 5 is schematic cross-sectional view of a lead body supporting a plurality of barbs in a deployed position.
[0014] FIG. 6 is schematic cross-sectional view of a lead body supporting a plurality of barbs in a distal position.
[0015] FIG. 7 is a schematic top view of a plurality of barbs supported by a base body.
[0016] FIG. 8 is a schematic cross-sectional view of the plurality of barbs and the base body of FIG. 7 with the plurality of barbs in a stowed position.
[0017] FIG. 9 is a schematic cross-sectional view of the plurality of barbs and the base body of FIG. 7 and FIG. 8 with the plurality of barbs in a deployed position.
[0018] FIG. 10 is a schematic cross-sectional view of a barb defined by a single-angle cut.
[0019] FIG. 11 is a schematic cross-sectional view of a barb defined by a dual-angle cut.
[0020] FIG. 12 is a perspective view illustrating an example lead distal portion.
[0021] FIG. 13 is an schematic end view of the lead distal portion of FIG. 12.
[0022] FIG. 14 is a perspective view illustrating an example lead distal portion.
[0023] FIG. 15 is an schematic end view of the lead distal portion of FIG. 14
[0024] FIG. 16 illustrates an example technique for supporting a plurality of barbs with a lead body.
DETAILED DESCRIPTION
[0025] The disclosure describes an implantable medical lead configured to deliver pacing to a heart of a patient. The implantable medical lead includes a lead body comprising a biostable material. The lead body supports a plurality of barbs comprising a biodegradable material. A fixation device extends distal to a distal end of the lead body. The plurality of barbs are configured to extend radially outward from the lead body to engage tissues when the fixation device engages tissues. The fixation device may support an electrode configured to provide pacing signals to a heart of a patient. For example, the plurality of barbs may be configured to engage tissues when the fixation device positions the electrode in tissues at or near a target site, such as tissues of the left bundle branch (LBB), His bundle (HB), right bundle branch (RBB), and other ventricular and/or cardiac tissues of the patient’s heart.
[0026] For conduction system pacing, positioning and/or maintaining an electrode at a location having sufficient proximity to a conduction pacing system of a heart may promote more effective delivery of pacing to the conduction pacing system. Thus, movement of an implantable lead supporting the electrode relative to a target site (e.g., in a proximal direction of distal direction) during and/or after implantation may alter the position of the electrode and impact the effectiveness of the conduction system pacing. For example, following implantation of the implantable lead, blood flow through the heart may impart fluid forces on the implantable lead, resulting in a proximally directed force on the implantable lead and potential movement of the implantable lead and supported electrode relative to the target site. Similarly, beating of the heart and/or other activity of patient may impart forces to the implantable lead and the supported electrode, causing potential movement of the implantable lead and supported electrode relative to the target site.
[0027] Although the implantable medical lead is described herein primarily in the context of examples in which the implantable medical lead is configured to deliver pacing to a heart of a patient, the assemblies and techniques described herein may be applicable to leads configured to deliver other therapies and/or are configured to be implanted in different locations within a patient.
[0028] The disclosure includes a medical system including an implantable medical lead. The implantable medical lead includes a plurality of barbs configured to mitigate and/or reduce a movement of the implantable medical lead relative to a target site. The implantable medical lead includes a fixation device supporting a fixation device electrode. Mitigating and/or reducing the movement of the implantable medical lead may reduce and/or mitigate movement of the fixation device electrode relative to the target site to, for example, limit alterations in the position of the fixation device electrode which might impact the effectiveness of conduction system pacing. The plurality of barbs are configured to extend radially outward from a lead body of the implantable medical lead to engage tissues within the target site as the fixation device engages tissues within the target site. In examples, the fixation device is a auger.
[0029] The plurality of barbs are defined by a biodegradable material (e.g., a biodegradable polymer) configured to degrade following engagement with the tissues. The biodegradable material may be a material configured to degrade when subjected to a fluid and/or biological constituent of the patient (e.g., blood and/or constituents of blood such as water, proteins, electrolytes, amino acids, salts, enzymes, hormones, and/or other constituents). For example, the biodegradable material may be configured to degrade when subjected to the fluids and/or biological constituents of a patient for a period less than about 6 months, in some examples less than 3 months. The lead body and/or the fixation device comprise a biostable material. The biostable material may be configured to substantially maintain its physical and chemical integrity when implanted within tissues of the patient.
[0030] Hence, the implantable medical lead may be configured such that the plurality of barbs assist in the retention of the lead distal portion during and/or following implantation. The plurality of barbs may degrade as the body of the patient forms scar tissue around the lead distal portion. Further, the degradation of the plurality of barbs may assist in the removal of the implantable medical lead after a period of time of implantation within the patient, should that be necessary.
[0031] The plurality of barbs are resiliently biased to extend radially outward from the lead distal portion to establish a deployed position. In examples, the resilient biasing limits the outward radial extension of the barbs to, for example, limit a potential for thrombosis that might occur with a deeper penetration of the barbs. For example, the lead distal portion may define a body radius extending from a longitudinal axis of the implantable medical lead to an outer surface supporting the plurality of barbs. One or more barbs may define a barb radius extending from the outer surface to a free end of the barb. In examples, the barb radius may be less than about thirty percent of the body radius. In some examples, the implantable medical lead includes two or more pluralities of barbs to assist in limiting movement of the lead distal portion while limiting the outward radial extension of the individual barbs.
[0032] In some examples, the medical system includes a delivery catheter defining a lumen. The implantable medical lead may be configured to translate and/or rotate within the lumen. An inner surface defining the lumen may be configured to impart a force on the plurality of barbs to substantially prevent the resilient biasing from causing the barbs to extend radially outward. The medical system may be configured such that proximal withdrawal of the delivery catheter relative to the implantable medical lead substantially releases the plurality of barbs, such that the plurality of barbs extend radially outward. In examples, the plurality of barbs are configured to flexibly bend distally from the deployed position when the delivery catheter is subsequently moved distally to resheath the plurality of barbs (e.g., should repositioning of the fixation device electrode be desired). The plurality of barbs are resiliently biased to return to the deployed position if the delivery catheter is returned to a position proximal to the plurality of barbs following the resheathing.
[0033] FIG. 1 is a conceptual diagram illustrating a portion of an example medical device system 100 including an implantable medical lead 112 positioned at a target site 114 within a patient 116. Implantable medical lead 112 includes an elongated lead body 118 defining a proximal portion 119 of implantable medical lead 112 (“lead proximal portion 119) and a distal portion 120 of implantable medical lead 112 (“lead distal portion 120”). In some examples, as illustrated in FIG. 1, target site 114 may include a portion of a heart 122, such as an atrioventricular septal wall of a right atrium (RA) of heart 122 or an interventricular septal wall of a right ventricle (RV) of heart 122, or other locations within a body of patient 116. A clinician may maneuver lead distal portion 120 through the vasculature of patient 116 in order to position lead distal portion 120 at or near target site 114. For example, the clinician may guide lead distal portion 120 through the superior vena cava (SVC) and into the RA, in order to access target site 114 on the atrioventricular septal wall, e.g., in the triangle of Koch region. In some examples, other pathways or techniques may be used to guide lead distal portion 120 into other target implant sites within the body of patient 116. Medical device system 100 may include a delivery catheter and/or outer member (not shown), and implantable medical lead 112 may be guided and/or maneuvered within a lumen of the delivery catheter in order to approach target site 114.
[0034] Implantable medical lead 112 may be configured to provide stimulation (e.g., pacing) to a native conduction system 123 of heart 122. For example, in one or more embodiments described herein, target site 114 may be the triangle of Koch region in the atrioventricular septal wall of the patient’s heart or the ventricular septal wall in the basal (e.g., high basal or high septal) region or apical (e.g., low septal or near the apex) region. Implantation in the atrioventricular septal wall or the ventricular septal wall may facilitate pacing of the left bundle branch, right bundle branch, or ventricular myocardium. Implantation in the basal region of the ventricular septal wall may facilitate pacing of the bundle branches. Implantation in the apical region may facilitate pacing of Purkinje fibers.
[0035] Implantable medical lead 112 includes fixation device 124 configured to penetrate cardiac tissue at or near target site 114. For example, fixation device 124 of implantable medical lead 112 may be configured to penetrate to a position at or near the left bundle branch (LBB), right bundle branch (RBB), other specialized conductive tissue, or other ventricular tissue of heart 122. In some examples, fixation device 124 supports a fixation device electrode (e.g., fixation device electrode 130 (FIG. 2)) configured to, for example, provide pacing to heart 122. Fixation device 124 may be electrically connected to a conductor (not shown) extending through implantable medical lead 112 from fixation device 124. In examples, the conductor is electrically connected to therapy delivery circuitry 127 of an implantable medical device (IMD) 126. Therapy delivery circuitry 127 may be configured to provide electrical signals through the conductor via fixation device 124 (e.g., to the fixation device electrode). The fixation device electrode may conduct the electrical signals to the target tissue of heart 122, causing the cardiac muscle, e.g., of the ventricles, to depolarize and, in turn, contract at a regular interval. In examples in which fixation device 124 penetrates to a position at or near the HB, RBB, LBB, or other specialized conductive tissue of heart 122, the cardiac pacing delivered via fixation device 124 (e.g., by the fixation device electrode) may be conduction system pacing (CSP) of heart 122, which may provide more physiologic activation and contraction of heart 122. Fixation device 124 (e.g., the fixation device electrode or another electrode) may also be electrically connected to sensing circuitry 129 of IMD 126 via the conductor. Sensing circuitry 129 may be configured to sense electrical activity of heart 122 via fixation device 124. In examples, IMD 126 includes processing circuitry 131, communication circuitry 133, and/or a memory 135,
[0036] In examples, fixation device 124 defines a auger (e.g., auger member 132 (FIG. 2)) extending distal to a distal end of lead distal portion 120. The auger may support the fixation device electrode. Fixation device 124 may be configured such that the auger engages tissues of target site 114 when the auger rotates about a longitudinal axis defined by lead body 118. For example, lead body 118 may be configured such that a torque on lead body 118 (e.g., on lead proximal portion 119) cause rotation of lead distal portion 120. The rotation of lead distal portion 120 may cause the rotation of the auger about the longitudinal axis. In examples, fixation device 124 (e.g., the auger) is configured to place the fixation device electrode into proximity of conduction system 123, such that such that IMD 126 may provide pacing to heart 122 via implantable medical lead 112.
[0037] For conduction system pacing, positioning and/or maintaining an electrode at a location having sufficient proximity to the conduction pacing system of a heart may promote more effective delivery of pacing to the conduction pacing system. Thus, movement of an implantable lead supporting the electrode relative to a target site (e.g., in a proximal direction of distal direction) during and/or after implantation may alter the position of the electrode and impact the effectiveness of the conduction system pacing. For example, following implantation of the implantable lead, blood flow through the heart may impart fluid forces on the implantable lead, resulting in a proximally directed force on the implantable lead and potential movement of the implantable lead and supported electrode relative to the target site. Similarly, beating of the heart and/or other activity of patient 116 may impart forces to the implantable lead and the supported electrode, causing potential movement of the implantable lead and supported electrode relative to the target site.
[0038] Implantable medical lead 112 includes a plurality of barbs (e.g., barbs 136, 152, 158 (FIG. 2)) configured to mitigate and/or reduce a movement of implantable medical lead 112 (e.g., lead distal portion 120) relative to target site 114. Mitigating and/or reducing the movement of implantable medical lead 112 may reduce and/or mitigate movement of the fixation device electrode relative to target site 114. The plurality of barbs are supported by lead distal portion 120 and configured to extend radially outward from lead body 118. The barbs are configured to engage tissues within target site 114 as fixation device 124 engages tissues within target site 114. For example, lead distal portion 120 may be configured such that, as fixation device 124 (e.g., a auger of fixation device 124) positions the fixation device electrode in proximity to conduction system 123, some portion of lead distal portion 120 may implant within tissues of target site 114 (e.g., within tissues of the ventricular septal wall or the atrioventricular septal wall). Lead distal portion 120 may be configured such that the barbs implant within the tissues when the portion of lead distal portion 120 implants within the tissues. The barbs may be configured to extend radially outward from lead distal portion 120 to engage the tissues and mitigate and/or reduce movement of lead distal portion 120 relative to target site 114, and thus reduce and/or mitigate movement of the fixation device electrode relative to target site 114. The barbs are defined by a biodegradable material configured to degrade following engagement with the tissues. For example, the barbs may be defined by a biodegradable polymer.
[0039] The barbs are resiliently biased to extend radially outward from lead distal portion 120. In examples, the resilient biasing limits the outward radial extension of the barbs from lead distal portion 120. The resilient biasing may limit the outward radial extension to, for example, limit a potential for thrombosis that might occur with a deeper penetration of the barbs. For example, lead distal portion 20 may define a body radius extending from the longitudinal axis of implantable medical lead 112 to an outer surface supporting the barbs. One or more barbs may define a barb radius extending from the outer surface to a free end of a barb the extends radially outward. In some examples, the barb radius may be less than about twenty percent of the body radius.
[0040] In some examples, medical system 100 includes a delivery catheter (e.g., delivery catheter 151 (FIG. 4)) defining a lumen (e.g., catheter lumen 149 (FIG. 4)). Implantable medical lead 112 (e.g., lead distal portion 120) may be configured to translate and/or rotate within the lumen. The delivery catheter (e.g., an inner surface defining the lumen) may be configured to impart a force on the barbs when lead distal portion 120 is within the lumen to substantially prevent the resilient biasing from causing the barbs to extend radially outward. Medical system 100 may be configured such that proximal withdrawal of the delivery catheter relative to lead body 118 substantially releases the barbs, such that the barbs extend radially outward. In examples, the barbs are configured to flexibly bend (e.g., bend distally) in the event the delivery catheter is subsequently moved distally to recover the barbs (e.g., should repositioning of the fixation device electrode be desired).
[0041] FIG. 2 is a perspective diagram illustrating a portion of example implantable medical lead 112. FIG. 3 is an end view of implantable medical lead 112. Implantable medical lead 112 includes lead body 118 defining a longitudinal axis L, lead distal portion 120, and fixation device 124. Distal lead portion 120 includes a distal end 128 of implantable lead 112 (“lead distal end 128”). Longitudinal axis L extends through lead body 118 (e.g., through lead proximal portion 119 and lead distal portion 120) and lead distal end 128. Fixation device 124 extends distal to (e.g., in the distal direction D) lead distal end 128. In examples, longitudinal axis L is substantially parallel to distal direction D and a proximal direction P opposite distal direction D. In FIG. 3, distal direction D extends out of the page and proximal direction P extends into the page. In examples, implantable medical lead 112 defines a radial direction R substantially perpendicular to longitudinal axis L.
[0042] Note that although FIG. 2 (and. E.g., FIGS 3-13) depict radial direction R as a single vector perpendicular to longitudinal axis L for illustration, radial direction R may be defined by any vector perpendicular to longitudinal axis L and extending from longitudinal axis L. For example, in FIG. 2, a first vector R1 extending from and perpendicular to longitudinal axis L extends in radial direction R. A second vector R2 extending from and perpendicular to longitudinal axis L also extends in radial direction R.
[0043] Fixation device 124 includes a body 125 (“fixation device body”) configured to pierce and potentially penetrate into or through target tissue. In examples, fixation device body 125 defines a auger member 132 defining a helical shape (e.g., a helical shape around longitudinal axis L). In examples, fixation device body 125 (e.g., auger member 132) extends distal to lead distal end 128 to a fixation device distal end 134. Fixation device body 125 may decrease in a cross-sectional dimension (e.g., a dimension parallel to radial direction R, such as a diameter) as fixation device body 125 extends distally from lead distal end 128 to fixation distal end 134. In examples, fixation device body 125 is configured to decrease the cross-sectional dimension from a cross-sectional dimension defined by lead distal end 128 (e.g., defined by lead outer surface 140). In examples, fixation device 124 includes a conductor (e.g., an electrically conductive material). In examples, fixation device body 125 is a conductor. The conductor may have a non-conductive coating, such as but not limited to polytetrafluoroethylene (PTFE). The conductor of fixation device 124 is electrically connected to a conductor of implantable medical device 112 (e.g., second conductor 115 (FIG. 4)). In some examples, the conductor of fixation device 124 comprises (e.g., is an extension of) the conductor of implantable medical lead 112. [0044] Fixation device 124 (e.g., fixation device body 125) may support a fixation device electrode 130 (e.g., between lead distal end 128 and fixation device distal end 134. In some examples, fixation device electrode 130 is a portion of fixation device body 125. For example, when fixation device body 125 is substantially covered by the non-conductive coating, fixation device electrode 130 may be a portion of fixation device body 125 uncoated by the non- conductive coating. In some examples, fixation device electrode 130 may comprise a portion of fixation device body 125 between lead distal end 128 and fixation device distal end 134. In some examples, fixation device electrode 130 may be a component supported by but substantially separable from fixation device body 125. Fixation device 124 may be configured such that fixation device electrode 130 is exposed to tissue when fixation device body 125 (e.g., auger member 132) is embedded in tissue (e.g., tissue at or around target site 114 (FIG. 1)). The conductor of fixation device 124 may be configured to electrically connect fixation device electrode 130 with therapy delivery circuitry 127 and/or sensing circuitry 129 (FIG. 1).
[0045] Lead distal portion 120 includes a plurality of barbs 136 (“barbs 136”) configured to mitigate and/or reduce a movement of fixation device 124 (e.g., fixation device electrode 130) relative to tissue when fixation device 124 is engaged with the tissue. Barbs 136 may include, for example, barb 137, barb 138, barb 139, barb 141, and/or others. Barbs 136 are configured to mitigate and/or reduce a movement of lead distal portion 120 (e.g., in the distal direction D) when fixation device 124 is engaged with tissue. Barbs 136 are configured to engage tissues within target site 114 as fixation device 124 engages tissues within target site 114. For example, lead distal portion 120 may be configured such that, as fixation device 124 (e.g., auger member 132) engages tissue and positions fixation device electrode 130 in proximity to conduction system 123 of heart 122 (FIG. 1), a portion of lead distal portion 120 supporting barbs 136 also implants within the tissues. Barbs 136 may engage the tissues to mitigate and/or reduce movement of fixation device electrode 130 relative to target site 114. For example, barbs 136 may be configured to engage tissues such that, when a proximally directed force is imparted to lead body 118 (e.g., due to blood flow through heart 122, beating of heart 122, and/or other activity of patient 116), barbs 136 impart a distally directed force on lead body 118 to mitigate and/or reduce movement of fixation device electrode 130 relative to target site 114.
[0046] Barbs 136 are defined by a biodegradable material configured to degrade following engagement with the tissues. The biodegradable material may be a material configured to degrade when subjected to a fluid and/or biological constituent of patient 116 (e.g., blood and/or constituents of blood such as water, proteins, electrolytes, amino acids, salts, enzymes, hormones, and/or other constituents). For example, the biodegradable material may be configured to degrade when subjected to the fluids and/or biological constituents of patient 116 for a period less than about 6 months, in some examples less than 3 months. In examples, the biodegradable material is configured to dissolve within the fluids and/or biological constituents of patient 116. In some examples, the biodegradable material is a material configured to be metabolized (e.g., to undergo a biotransformation) by patient 116. In some examples, the biodegradable material is a biodegradable polymer. The biodegradable polymer may comprise, for example, glycolic acid, lactic acid, and/or trimethelyene carbonate. In examples, the biodegradable polymer comprises collagen and/or poly (a-esters). In examples, the biodegradable material
[0047] Lead body 118 and/or fixation device 124 comprise a biostable material. The biostable material may be configured to substantially maintain its physical and chemical integrity when implanted within tissues of patient 116. The biostable material may be a material configured to substantially resist degrading effects that might otherwise occur to a material when subject to the fluids and/or biological constituents of patient 116. For example, the biostable material may be configured to substantially resist degrading effects when subjected to blood and/or constituents of blood such as water, proteins, electrolytes, amino acids, salts, enzymes, hormones, and/or other constituents. For example, the biostable material may be configured to substantially resist degrading effects when subjected to the fluids of patient 116 for a period greater than 3 months, a period greater than 6 months, or a longer period. In examples, the biostable material comprises a polyeurothane. In examples, the polyurethane comprises a polycarbonate, a poly ether, and/or a polyester.
[0048] Hence, implantable medical lead 112 may be configured to engage tissues of patient 116 using fixation device 124 and barbs 136. Implantable medical lead 112 may be configured to engage the tissues to position fixation device electrode 130 at a location having sufficient proximity to conduction system 123 to deliver conduction system pacing to heart 122. Fixation device 124 and barbs 136 may resist movement of implantable medical lead 112 (e.g., lead distal portion 120) to limit and/or reduce movement of fixation device electrode 130 relative to target site 114. Lead body 118 and/or fixation device 124 comprise a biostable material while barbs 136 comprise a biodegradable material. Thus, implantable medical lead 112 is configured such that barbs 136 may assist in the retention of lead distal portion 120 during and/or following implantation. Barbs 136 may degrade as the body of patient 116 forms scar tissue around lead distal portion 120 (which, e.g., may anchor lead distal portion 120 more firmly). Further, degradation of barbs 136 may assist in the removal of implantable medical lead 112 after a period of time of implantation within patient 116, should that be necessary. For example, degradation of barbs 136 may limit and/or substantially prevent a growth of scar tissue around barbs 136 following implantation.
[0049] Lead body 118 defines an outer surface 140 of lead distal portion 120 (“lead outer surface 140”). Lead outer surface 140 is configured to support barbs 136. Lead distal portion 120 is configured such that lead outer surface 140 supports barbs 136 at a location proximal (e.g., displaced in the proximal direction P) to fixation device 124 and lead distal end 128. In examples, barbs 136 are arranged around (e.g., substantially surrounding) longitudinal axis L. For example, barbs 136 may define a perimeter PB surrounding longitudinal axis L. In examples, perimeter PB is a perimeter on lead outer surface 140. Perimeter PB may be, for example, a closed curve, an open curve such as a helical curve, or some other curve surrounding longitudinal axis L. In some examples, perimeter PB defines a curved shape (e.g., circular or oval-shaped), a curvilinear shape (e.g., containing curved portions and linear portions) or a polygonal shape surrounding longitudinal axis L.
[0050] In some examples, lead outer surface 140 may be defined by a single component of implantable medical lead 112, such as an outer layer or other surface comprising some portion of lead body 118. In some examples, lead outer surface 140 may be defined by a two or more components comprising lead body 118, such as a first surface defined by a first component of lead body 118 and a second surface defined by a second component of lead body 118. In examples, lead body 118 includes a plurality of components, such as first conductor 111, an insulating material 113, a second conductor 115 (FIGS. 4-6), and/or other components.
Insulating material 113 may be configured to electrically isolate first conductor 111 from second conductor 115. In examples, lead body 118 may include a torque coil (e.g., extending around longitudinal axis L) configured to transfer a torque around longitudinal axis L from lead proximal portion 119 to lead distal portion 120 (FIG. 1). The torque coil may comprise at least some portion of second conductor 115. In some examples, lead body 118 is configured such that implantable medical lead 112 is a lumenless lead. For example, lead body 118 may be configured such that implantable medical lead lacks an internal lumen extending from lead proximal portion 119 to lead distal portion 120.
[0051] In examples, outer surface 140 is configured to surround longitudinal axis L. Outer surface 140 may be configured such that a cross-sectional area of lead body 118 defines a closed curve (e.g., perimeter PS) around longitudinal axis L. In examples, the cross-sectional area is perpendicular to longitudinal axis L. In some examples, perimeter PS defines a curved shape (e.g., circular or oval-shaped), a curvilinear shape (e.g., containing curved portions and linear portions), or a polygonal shape surrounding longitudinal axis L. In some examples, lead body 118 defines perimeter PS in a geometric plane (e.g., a plane perpendicular to longitudinal axis L) and barbs 136 define perimeter PB in the geometric plane, and perimeter PS is substantially coincident with perimeter PB. In some examples, lead body 118 defines perimeter PS in the geometric plane and barbs 136 define perimeter PB in the geometric plane, and perimeter PS surrounds and/or intersects perimeter PB. In some examples, lead body 118 defines perimeter PS in the geometric plane and barbs 136 define perimeter PB in the geometric plane, and perimeter PB surrounds and/or intersects perimeter PS.
[0052] In some examples, lead body 118 is configured such that perimeter PS is substantially circular (e.g., circular or nearly circular to the extent permitted by manufacturing tolerances). Lead body 118 may be configured such that perimeter PS defines a substantially circular cross- sectional area of lead body 118 (e.g., lead distal portion 120) surrounding (e.g., centered on) longitudinal axis L. In some examples, the substantially circular cross-sectional area defines a diameter of less than seven French (Fr), such as about five Fr.
[0053] Barbs 136 may be positioned in a substantially symmetric pattern around longitudinal axis L. In examples, barbs 136 may be arranged such that an individual barb (e.g., barb 137) and an adjacent barb (e.g., barb 138) defines a first central angle of perimeter P and the individual barb (e.g., barb 137) and another adjacent barb (e.g., barb 141) defines a second central angle of perimeter P substantially equal to the first central angle (e.g., equal or nearly equal to the extent permitted by manufacturing tolerances). In examples, the first central angle and the second central angle define vertices intersected by longitudinal axis L. In examples, the first central angle subtends an angle within 30 degrees, in some examples within 15 degrees, and/or in some examples within 5 degrees of an angle subtended by the second central angle.
[0054] For example, barb 137 may define a free end 144 and an axis SI extending from longitudinal axis L to free end 144. Barb 138 may define a free end 146 and an axis S2 extending from longitudinal axis L to free end 146. Barb 141 may define a free end 148 and an axis S3 extending from longitudinal axis L to free end 148. Barb 137, 138, 141 may be positioned (e.g., by lead outer surface 140) in a substantially symmetric manner around longitudinal axis L such that axis SI and axis S2 define a central angle Al and axis SI and axis S3 define a central angle A2 substantially equal to central angle Al. In examples, Barb 139 may define a free end 150 and an axis S4 extending from longitudinal axis L to free end 150. Axis S3 and axis S4 may define a central angle A3 substantially equal to central angle Al and/or central angle A2. Axis S2 and axis S4 may define a central angle A4 substantially equal to central angle Al, central angle A2, and/or central angle A3. Barbs 136 may include other barbs defining similar central angles substantially equal to central angle Al, central angle A2, central angle A3, and/or central angle A4.
[0055] In some examples, lead body 118 supports an electrode 142 (“body electrode 142”). In some examples, implantable medical lead 112 is configured such that body electrode 142 is exposed to tissue when fixation device body 125 and barbs 136 are embedded in tissue (e.g., tissue at or around target site 114 (FIG. 1)). In some examples, implantable medical lead 112 is configured such that body electrode 142 is outside of tissue when fixation device body 125 and barbs 136 are embedded in tissue. For example, implantable medical lead 112 may be configured such that body electrode 142 positions in a chamber of heart 122 when fixation device body 125 and barbs 136 are embedded in tissue. A position of body electrode 142 relative to tissues comprising target site 114 when fixation device body 125 and barbs 136 engage the tissues may be dependent on the anatomy of patient 116. In examples, electrode 142 surrounds longitudinal axis at least partially. Electrode 142 may have various shapes such as tines, helices, screws, rings, and so on. In some examples, electrode 142 is a ring electrode configured to surround longitudinal axis L. Implantable medical lead 112 may include a conductor (e.g., first conductor 111 (FIG. 4)) configured to electrically connect body electrode 142 with therapy delivery circuitry 127 and/or sensing circuitry 129
[0056] Barbs 136 may be configured to limit their radial extension relative to lead outer surface 140. For example, barbs 136 may limit their radial extension to reduce and/or limit penetration into the tissues of patient 116 when fixation device 124 engages the tissues of patient 116. Limiting the radial extension of barbs 136 may mitigate and/or eliminate scar tissue growth and/or other impacts such as thrombosis which might develop in the absence of the limited radial extension. In examples, barbs 136 are configured such that a radial extension from lead outer surface 140 to free end 144, 146, 148, 150 is less than about thirty percent, in some examples less than about twenty percent, of a radial extension from longitudinal axis L to outer surface [0057] For example, lead distal portion 120 may define a body radius RL extending in radial direction R from longitudinal axis L to outer surface 140. Barb 137 may define a barb radius RB extending in radial direction R from outer surface 140 to free end 144 (e.g., when free end 144 is displaced from outer surface 140). In some examples, barb radius RB is less than about thirty percent of body radius RL. In some examples, barb radius RB is less than about twenty percent of body radius RL. In some examples, perimeter PB is a substantially circular perimeter defined by at least three of free end 144, free end 146, free end 148, and/or free end 150 and defining a first diameter. Perimeter PS is a circular perimeter defined by outer surface 140 and defining a second diameter. The first diameter may greater than the second diameter by less than about thirty percent of the second diameter, in some examples less than about twenty percent of the second diameter. For example, when outer surface 140 is configured such that the second diameter is about 5 Fr (e.g., about 1.667 millimeter (mm)), barbs 136 may define the first diameter to be less than about 5.3 Fr (e.g., less than about 2.167 mm) in some examples, and/or less than about 5.2 Fr (e.g., less than about 2.000 mm) in some examples. Barb radius RB may be substantially parallel to body radius RL.
[0058] Lead distal portion 120 may be configured to increase a distally directed force imparted to lead distal portion 120 when a proximally directed force is imparted to lead body 118 (e.g., due to blood flow through heart 122, beating of heart 122, and/or other activity of patient 116). In examples, lead distal portion 120 may be configured to increase the distally directed using one or more pluralities of barbs in addition to barbs 136. Lead distal portion 120 may be configured to increase the distally directed force while limiting the outward radial extension of individual barbs to, for example, mitigate and/or eliminate scar tissue growth and/or other impacts such as thrombosis which might develop in the absence of the limited radial extension. For example, each individual barb may be configured to define a barb radius similar to barb radius RB, such that the barb radius is less than about thirty percent of body radius RL.
[0059] For example, lead distal portion 120 may include a second plurality of barbs 152 (“barbs 152”) configured to mitigate and/or reduce a movement of fixation device 124 (e.g., fixation device electrode 130) relative to tissue when fixation device 124 is engaged with the tissue. Barbs 152 may include, for example, barb 153, barb 154, barb 155, barb 156, and/or others. Lead distal portion 120 may include a third plurality of barbs 158 (“barbs 158”) configured to mitigate and/or reduce a movement of fixation device 124 (e.g., fixation device electrode 130) relative to tissue when fixation device 124 is engaged with the tissue. Barbs 158 may include, for example, barb 159, barb 160, barb 161, barb 162, and/or others. Barb 156 and barb 162 are hidden by lead distal portion 120 in FIG. 2. Barbs 152, 158 are hidden by lead distal portion 120 in FIG. 3. In examples, barbs 136 are configured to position distal to barbs 152. Barbs 152 may be configured to position distal to barbs 158.
[0060] Barbs 152, 158 and the individual barbs therein may be configured similarly to barbs 136. For example, individual barbs within barbs 152, 158 may be configured to define a barb radius similar to barb radius RB. Barbs 152, 158 may be configured to engage tissues such that, when a proximally directed force is imparted to lead body 118, barbs 152, 158 impart additional distally directed forces on lead body 118 (e.g., additional to that imparted by barbs 136) to, for example, mitigate and/or reduce movement of fixation device electrode 130 relative to target site 114. Barbs 152, 158 may be configured such that the additional distally directed forces are additive with the distally directed force of barbs 136.
[0061] In examples, barbs 136, 152, 158 are resiliently biased to extend radially outward (e.g., in radial direction R) from lead distal portion 120. In examples, barbs 136, 152, 158 are configured such that the resilient biasing limits the outward radial extension from lead distal portion 120 (e.g., limits barb radius RB to less than about thirty percent, in some examples less than about twenty percent, of body radius RL). In some examples, medical system 100 includes a delivery catheter configured to deliver implantable medical lead 112 to target site 114 (FIG. 1). The delivery catheter may be configured to impart one or more forces on barbs 136, 152, 158 to substantially prevent the resilient biasing from causing barbs 136, 152, 158 to extend radially outward when the deliver catheter surrounds lead distal portion 120.
[0062] For example, FIG. 4 is a schematic illustration depicting lead distal portion 120 within a lumen 149 of a delivery catheter 151 (“catheter lumen 149”). Catheter lumen 149 is defined by a body 147 of delivery catheter 151 (“catheter body 147”). Catheter body 147 defines an inner surface 157 (“catheter inner surface 157”) surrounding catheter lumen 149. FIG. 4 depicts catheter inner surface 157 imparting a force on barbs 136 (e.g., force FBI on barb 137), a force on barbs 152 (e.g., force FB2 on barb 153), and a force on barbs 159 (e.g., force FB3 on barb 159). Delivery catheter 151 may be configured such that force FBI on barbs 136, force FB2 on barbs 152, and/or force FB3 on barbs 158 substantially prevent the resilient biasing from causing barbs 136, 152, 158 to extend radially outward. [0063] Catheter inner surface 157 may impart similar forces on barb 138, 139, 141, 154, 155, 156, 160, 161, 162. Although catheter inner surface 157 is depicted with a small displacement from barbs 137, 153, 159, 139, 155, 161 in FIG. 5 for clarity, delivery catheter 151 and/or barbs 136, 152, 158 may be configured such that catheter inner surface 157 contacts one or more of barbs 136, 152, 158 when barbs 136, 152, 158 are positioned within catheter lumen 149. Delivery catheter 151 may be configured to define a lumen diameter LD of catheter lumen 149 such that catheter inner surface 157 imparts a force on barbs 136, 152, 158 when barbs 136, 152, 158 are within catheter lumen 149 to substantially prevent barbs 136, 152, 158 from fully extending radially outward.
[0064] In some examples, barb 137 defines a length from a free end 144 to a fixed end 145 of from about 1 millimeter (mm) to about 3 mm. In examples, the length is substantially parallel to longitudinal axis L when barb 137 is in the stowed position. Barb 137 may define a width of from about 0.5 mm to about 1.5 mm. The width may be perpendicular to the length. In examples, the width is substantially perpendicular to radial direction R and substantially perpendicular to longitudinal axis L when barb 137 is in the stowed position. Barb 137 may define a depth of from about 0.5 mm to about 1.5 mm. The depth may be perpendicular to the length and the width. In examples, the depth is substantially parallel to radial direction R and substantially perpendicular to longitudinal axis L when barb 137 is in the stowed position.
[0065] FIG. 5 is a schematic illustration depicting lead distal portion 120 positioned relative to delivery catheter 151 such that barbs 136, 152, 158 are distal to an opening 163 defined by catheter body 147 (“catheter lumen opening 163”). Catheter lumen opening 163 opens into catheter lumen 149. In examples, catheter body 147 defines catheter lumen opening 163 at a distal end 165 of delivery catheter 151 (“catheter distal end 165”). In FIG. 5, barbs 136, 152, 158 are positioned distal to catheter inner surface 157, such that the resilient biasing of barbs 136, 152, 158 causes barbs 136, 152, 158 to extend radially outward (e.g., in radial direction R) from lead outer surface 140. Delivery catheter 151 is depicted as a cross-section in FIG. 4 and FIG. 5, with a cutting plane taken in a plane defined by longitudinal axis L and radial direction R.
[0066] Lead distal portion 120 may be configured to translate in the distal direction D and/or the proximal direction P relative to catheter body 147 (e.g., catheter inner surface 157) when lead distal portion 120 is positioned within catheter lumen 149. Lead distal portion 120 may be configured to rotate about longitudinal axis L relative to catheter body 147 (e.g., catheter inner surface 157) when lead distal portion 120 is positioned within catheter lumen 149. Catheter lumen opening 163 may be configured to allow lead distal portion 120 to pass therethrough. In examples, implantable medical lead 112 (e.g., lead proximal portion 119 (FIG. 1)) is configured to cause lead distal portion 120 to move in the distal direction D relative to catheter body 147, move in the proximal direction P relative to catheter body 147, and/or rotate about longitudinal axis L relative to catheter body 147. In examples, delivery catheter 151 is configured to move in the proximal direction P relative to lead body 118 to cause lead distal portion 120 to move in the distal direction D relative to catheter body 147. Delivery catheter 151 may be configured to move in the distal direction D relative to lead body 118 to cause lead distal portion 120 to move in the proximal direction P relative to catheter body 147.
[0067] Medical system 100 may be configured such that a proximal withdrawal of delivery catheter 151 relative to lead body 118 substantially releases barb 137 and/or other barbs of barbs 136, 152, 158, such that barbs 136, 152, 158 extend radially outward to engage tissues of patient 116. Although the discussion below and elsewhere refers mainly to barb 137, the discussion may apply to any of barb 138, 139, 141, 153, 154, 155, 156, 159, 160, 161, 162 and/or other barbs of implantable medical lead 112.
[0068] In examples, barb 137 is configured to transition from a stowed position when lead distal portion 120 is positioned within catheter lumen 149 to a deployed position when lead distal portion 120 is positioned distal to catheter lumen 149 (e.g., distal to catheter lumen opening 163). In examples, barb 137 is configured to define a first displacement from lead outer surface 140 in the stowed position and define a second displacement from lead outer surface 140 in the deployed position, with the second displacement greater than the first displacement. In examples, the first displacement and the second displacement are substantially perpendicular to longitudinal axis L. The first displacement may be substantially parallel to the second displacement. In some examples, the first displacement and the second displacement are substantially parallel to a vector VI extend from and normal to lead outer surface 140.
[0069] For example, FIG. 4 depicts barb 137 in the stowed position, with free end 144 defining a first displacement DI from lead outer surface 140. FIG. 5 depicts barb 137 in the deployed position, with free end 144 defining a second displacement D2 from lead outer surface 140. Second displacement D2 is greater than first displacement DI. Barb 137 may be configured to substantially displace free end 144 (e.g., relative to lead outer surface 140 and/or longitudinal axis L) in the radial direction R when barb 137 transitions from the stowed position to the deployed position.
[0070] In examples, barb 137 includes a fixed end 145 configured to be substantially stationary with respect to lead outer surface 140. Barb 137 may be configured such that fixed end 145 remains substantially stationary with respect to lead outer surface 140 as free end 144 displaces relative to lead outer surface 140 (e.g., when barb 137 transitions from the stowed position to the fixed position). In examples, barb 137 is configured such that at least some portion of barb 137 (e.g., a portion including free end 144) substantially rotates around fixed end 145 when free end 144 displaces relative to lead outer surface 140. For example, barb 137 may include a body 164 (“barb body 164”) defining free end 144 and fixed end 145. Barb 137 may be configured such that at least some portion of barb body 164 substantially rotates around fixed end 145 (e.g., by bending or flexing) to displace free end 144 from first displacement DI (e.g., in the stowed position) to second displacement D2 (e.g., in the deployed position). Barb 137 may be configured such that fixed end 145 substantially acts as a fixed pivot point for barb body 164 when barb body 164 substantially rotates around fixed end 145 to displace free end 144 from first displacement DI to second displacement D2. In examples, free end 144 is proximal to fixed end 145 when barb 137 is in the stowed position. Free end 144 may be proximal to fixed end 145 when barb 137 is in the deployed position.
[0071] Barb body 164 may be configured to flex and/or bend when barb 137 transitions from the deployed position to the stowed position. For example, barb body 164 may configured to flex and/or bend when free end 144 transitions from defining first displacement D2 (e.g., in the deployed position) to defining second displacement DI (e.g., in the stowed position). In examples, barb body 164 is a substantially elastically deforming element which exhibits a change in shape when an external force (e.g., force FBI) is applied to barb body 164, and which substantially reverses the change in shape when the external force is removed.
[0072] Lead distal portion 120 may be configured such that, when barbs 136, 152, 158 engage tissue, lead distal portion 120 provides a first resistance when lead body 118 moves in a first direction and provides a second resistance different from the first resistance when lead body 118 moves in a second direction. In examples, barb 137 is configured to provide the first resistance greater than the second resistance. For example, barb 137 may be configured to provide the first resistance by exerting a force FP in the proximal direction P on lead body 118 when a given magnitude of force is imparted to lead body 118 in the distal direction D (e.g., by a clinician). Barb 137 may be configured to provide the second resistance by exerting a force FD in the distal direction D on lead body 118 when the given magnitude of force is imparted to lead body 118 in the proximal direction P (e.g., by a clinician). Barb 137 may be configured such that the force FP is greater than the force FD, such that barb 137 resists motion of lead body 118 in the proximal direction P to a greater extent than a resistance to motion of lead body 118 in the distal direction. In some examples, barb 137 may be configured to substantially flatten (e.g., decrease the distance D2) when barb 137 is engaged when tissue and lead body 118 moves in the proximal direction P relative to the tissue.
[0073] In examples, barb 137 is resiliently biased to extend outward (e.g., in radial direction R) from lead outer surface 140. The resilient biasing of barb 137 may result in a tendency of barb 137 to return or attempt to return to the deployed position when barb 137 is displaced from (e.g., departs from) the deployed position (e.g., by force FBI (FIG. 4)). For example, the resilient biasing may cause barb 137 to substantially establish the deployed position in the absence of an external force (e.g., force FBI) acting on barb 137. Barb 137 may be configured such that the resilient biasing causes barb 137 to transition from the stowed position to the deployed position when the external force is removed (e.g., when delivery catheter 151 is moved proximally relative to lead body 118 such that barb 137 is distal to catheter lumen opening 163).
[0074] Barb 137 may be resiliently biased such that, when an external force such as force FBI acts on the barb body 164 (e.g., free end 144) to hold barb 137 in the stowed position, the resilient biasing causes barb body 164 (e.g., free end 144) to exert a reaction force FR opposing the external force (e.g., opposing force FBI). For example, when catheter inner surface 157 exerts force FBI on barb body 164, the resilient biasing of barb body 164 may cause barb body 164 to impart force FR on catheter inner surface 157.
[0075] Although free end 144 is depicted as being displaced from lead outer surface 140 in the radial direction R when free end 144 and lead outer surface 140 define displacement DI, this is not required. In some examples, displacement DI may define a displacement from lead outer surface 140 extending in a direction opposite radial direction R. For example, barb 137 may be configured such that, in the stowed position, free end 144 is displaced from lead outer surface 140 in the direction opposite radial direction R (e.g., in the stowed position, free end 144 may be nearer to longitudinal axis L than lead outer surface 140). In some examples, displacement DI may be substantially zero. For example, barb 137 may be configured such that, in the stowed position, free end 144 is substantially flush with lead outer surface 140 (e.g., flush or nearly flush to the extent permitted by manufacturing tolerances).
[0076] In some examples, barb 137 is configured to insert within a recess 166 defined by lead body 118 (e.g., lead outer surface 140) when lead outer surface 140 supports barb 137. For example, barb 137 (e.g., fixed end 145) may be coupled to a base body 168 configured to insert within recess 166. Recess 166 and portions of base body 168 are depicted with dashed lines in FIG. 4 and FIG. 5. Base body 168 may support barb 137. Barb 137 may be configured such that base body 168 and barb body 164 define a substantially contiguous, unified body. In some examples, base body 168 supports at least one barb from two or more of barbs 136, barbs 152, and/or barbs 158. Base body 168 may extend in the proximal direction P or the distal direction D from fixed end 145 to enable the support of the at least one barb from two or more of barbs 136, barbs 152, and/or barbs 158. For example, as depicted in FIG. 5, base body 168 may be configured to support barb 137 (e.g., fixed end 145) and extend in the proximal direction P from fixed end 145 to support a barb of barbs 152 (e.g., barb 153) and/or a barb of barbs 158 (e.g., barb 159). Base body 168 may be defined by a biodegradable material configured to degrade following engagement with tissues of patient 116 (e.g., a biodegradable polymer). In examples, barb 137, 153, 159 comprises a biodegradable material and base body 168 comprises the biodegradable material.
[0077] In examples, base body 168 is configured to support each of the barbs within two or more of barbs 136, barbs 152, and/or barbs 158 at a fixed end of the each of the barbs. For example, barb 153 (e.g., a body of barb 153) may define include a free end 170 configured to extend radially outward from lead outer surface 140 and a fixed end 172 configured to be substantially stationary with respect to lead outer surface 140. Barb 159 (e.g., a body of barb 159) may define include a free end 174 configured to extend radially outward from lead outer surface 140 and a fixed end 176 configured to be substantially stationary with respect to lead outer surface 140. Base body 168 may be configured to support at least two of barb 137 at fixed end 145, barb 153 at fixed end 172, and/or barb 159 at fixed end 176. In examples, base body 168 is configured to support barb 137 (e.g., at fixed end 145) , barb 153 (e.g., at fixed end 172), and barb 159 (e.g., at fixed end 176). 1 [0078] In some examples, outer surface 140 supports a second base body 169 (FIG. 2) supporting at least one barb from two or more of barbs 136, barbs 152, and/or barbs 158. Lead distal portion 120 may include any number of base bodies supporting at least one barb from two or more of barbs 136, barbs 152, and/or barbs 158. Lead distal portion 120 may support second base body 169 and/or other base bodies in a recess configured similarly to recess 166.
[0079] In examples, lead body 118 is configured to define one or more rounded boundaries of recess 166. Rounded boundaries may, for example, may assist in the removal of implantable medical lead 112 once barbs 136, 152, 158 have degraded within patient 116, should that be necessary. For example, recess 166 may extends from a first end 182 (“first recess end 182”) defined by lead body 118 (e.g., outer surface 140) to a second end 184 (second recess end 184”) defined by lead body 118 (e.g., outer surface 140). In examples, first recess end 182 is proximal to second recess end 184. At least one of first recess end 182 and/or second recess end 184 may be configured to define a curvature (e.g., a smooth curve). For example, first recess end 182 may define a curvature Cl in a geometric plane including longitudinal axis L and radial direction R. Second recess end 184 may define a curvature C2 in the geometric plane including longitudinal axis L and radial direction R.
[0080] In examples, a support surface 186 may define at least some portion of a boundary of recess 166. Support surface 186 is a portion of lead outer surface 140. Base body 168 may be configured to contact support surface 186 when base body 168 inserts within recess 166. In examples, support surface extends substantially from first recess end 182 to second recess end 184. Curvature Cl and/or curvature C2 may extend in radial direction R from support surface 186, such that. For example, lead body 118 defines a curved boundary over at least some portion of first recess end 182 and/or second recess end 184. In examples, curvature Cl and/or curvature C2 define a concavity which is concave up with respect to support surface 186. In examples, curvature Cl and/or curvature C2 define a negative curvature with respect to a vector normal to support surface 186.
[0081] In some examples, lead body 118 is configured to define one or more rounded boundaries of support surface 186 (e.g., similar to curvature Cl and/or curvature C2) which substantially extend at least partially from first recess end 182 to second recess end 184. The one or more rounded boundaries may define a curvature in a geometric plane substantially perpendicular to longitudinal axis L. In some examples, lead body 118 defines recess 166 such that a rounded boundary surrounds substantially the entirety of support surface 186.
[0082] In examples, barb 137 is configured to flexibly bend (e.g., bend distally) from the deployed position of FIG. 5 (e.g., where free end 144 is proximal to fixed end 145), to a distal position where free end 144 is distal to fixed end 145. Barb 137 may be configured to assume the distal position when delivery catheter 151 is moved from a first position proximal to barb 137 to a second position distal to barb 137. The distal bending of barb 137 may allow substantially resheathing barb 137 (e.g., and other barbs of barbs 136, 152, 158) with delivery catheter 151 to assist in, for example, moving lead distal portion 120 to a new location in patient 116, should that be necessary (e.g., moving lead distal portion 120 during pace mapping to locate target site 114).
[0083] For example, FIG. 6 is a schematic illustration depicting barb 137 in the distal position. Free end 144 is distal to fixed end 145 in the distal position. Barb 139, barb 153, and barb 155 are similarly depicted. Delivery catheter 151 is depicted as a cross-section in FIG. 4 and FIG. 5, with a cutting plane taken in a plane defined by longitudinal axis L and radial direction R. Portions of barb 137 and/or base body 168 (e.g., portions within recess 166) are depicted with dashed lines.
[0084] Barb 137 may be configured to move from the deployed position (depicted in FIG. 5) to the distal position when a distally directed force is imparted on barb body 164. For example, barb body 164 may be configured to move from the deployed position to the distal position when delivery catheter 151 imparts the distally directed force. In examples, delivery catheter 151 (e.g., catheter distal end 165) is configured to impart the distally directed force on barb body 164 when delivery catheter 151 moves from the first position proximal to barb 137 (e.g., as depicted in FIG. 5) to the second position distal to barb 137 (e.g., as depicted in FIG. 6). In examples, delivery catheter 151 is configured such that lumen diameter LD causes catheter distal end 165 to impart the distally directed force on barb body 164 when catheter distal end 165 moves from a position proximal to barb 137 to a position distal to barb 137.
[0085] Barb 137 (e.g., barb body 164) may be configured such that fixed end 145 is substantially stationary relative to lead body 118 when free end 144 moves from the deployed position to the distal position. Catheter inner surface 157 may be configured to impart a force on barb body 164 (e.g., a force toward longitudinal axis L) to substantially hold barb 137 in the distal position. For example, catheter inner surface 157 may be configured to impart the force holding barb 137 in the distal position when catheter distal end 165 is distal to barb 137.
[0086] Barb 137 (e.g., barb body 164) may be configured to move from the distal position to the deployed position when catheter inner surface 157 (and/or another object or body) ceases to impart the force holding barb 137 in the distal position. In examples, barb 137 is resiliently biased to move from the distal position to the deployed position. The resilient biasing of barb 137 may result in a tendency of barb 137 to return or attempt to return to the deployed position when is in the distal position. Barb 137 may be configured such that the resilient biasing causes barb 137 to transition from the distal position to the deployed position when delivery catheter 151 is moved proximally relative to lead body 118 such that barb 137 is distal to catheter lumen opening 163.
[0087] For example, barb 137 may be resiliently biased such that, when an external force acts on barb body 164 to hold barb 137 in the distal position, the resilient biasing causes barb body 164 to exert a reaction force opposing the external force. For example, when catheter inner surface 157 exerts a force FB4 on barb body 164 to hold barb body 164 in the distal position, the resilient biasing of barb body 164 may cause barb body 164 to impart a reaction force FR2 on catheter inner surface 157.
[0088] Barb 137 may comprise a unified body defining barb body 164 and base body 168. In examples, the unified body further comprises at least a body of barb 153 and/or a body of barb 159. Barb 137, 153, 159 may be defined by a cut substantially separating barb 137, 153, 159 and base body 168.
[0089] For example, FIG. 7 is a schematic top view of a structure body 188 defining barb base 168 and defining one or more barbs such as barb 137, barb 153, and barb 159. FIG. 8 is a cross-section of structure body 188 with barb 137, 153, 159 in the stowed position. FIG. 9 is a cross-section of structure body 188 with barb 137, 153, 159 in the deployed position. Structure body 188 is a unified body, such that a first portion of a material comprising barb base 168 is contiguous with a second portion of the material defining barb 137, 153, 159. For example, structure body 188 may be configured such that a boundary between barb body 164 (e.g., a first portion) and base body 168 (e.g., a second portion) may be contiguous such that structure body 188 lacks a defined material interface between barb body 164 and base body 168. In FIG. 8 and FIG. 9, the cross-section is taken in a plane which includes body axis LS and a structure radial direction RS perpendicular to body axis LS.
[0090] Structure body 188 defines a body axis LS extending through a first end 190 of structure body 188 (“first body end 190”) and a second end 192 of structure body 188 (“second body end 192”). Structure body 188 is configured to insert into recess 166 (FIG. 5, FIG. 6). First body end 190 may be configured to contact first recess end 178 when structure body 188 inserts into recess 166. Second body end 192 may be configured to contact second recess end 180 when structure body 188 inserts into recess 166. In examples, structure body 188 is configured such that body axis LS is substantially parallel to longitudinal axis L and/or structure radial direction RS is substantially parallel to radial direction R when structure body 188 is inserted into recess 166.
[0091] Barb 137 is defined by a cut CT1 in structure body 188 substantially separating barb 137 and base body 168. Barb 153 is defined by a cut CT2 in structure body 188 substantially separating barb 153 and base body 168. Barb 159 is defined by a cut CT3 in structure body 188 substantially separating barb 159 and base body 168. In examples, cut CT1 is configured to cause free end 144 of barb 137 to be displaced from fixed end 145 in the proximal direction P when barb 137 is in the stowed position or the deployed position. Cut CT2 may be configured to cause free end 170 of barb 153 to be displaced from fixed end 172 in the proximal direction P when barb 153 is in the stowed position or the deployed position. Cut CT3 may be configured to cause free end 174 of barb 159 to be displaced from fixed end 176 in the proximal direction P when barb 159 is in the stowed position or the deployed position.
[0092] Structure body 188 (e.g., barb 137) may be configured to define a separation G1 (e.g., between base body 168 and barb 137), define a separation G2 (e.g., between base body 168 and barb 153), and/or define a separation G3 (e.g., between base body 168 and barb 159) when barb 137, 153, 159 is in the deployed configuration. In examples, cut CT1 is configured to enable free end 144 to be displaced from fixed end 145 in structure radial direction RS (e.g., to define separation Gl) when barb 137 is in the deployed position. Cut CT2 may be configured to enable free end 170 to be displaced from fixed end 172 in structure radial direction RS (e.g., to define separation G2) when barb 153 is in the deployed position. Cut CT3 may be configured to enable free end 174 to be displaced from fixed end 176 in structure radial direction RS (e.g., to define separation G3) when barb 159 is in the deployed position. In examples, structure body 188 may be fabricated by cutting structure body 188 to generate cut CT1 to define barb 137, generate cut CT2 to define barb 153, and/or cut CT3 to generate barb 159. Subsequent to generating cut CT1, barb 137 may be resiliently biased such that barb 137 tends to assume a deployed position (e.g., in the absence of an externally imparted force on barb 137). Subsequent to generating cut CT2, barb 153 may be resiliently biased such that barb 153 tends to assume a deployed position (e.g., in the absence of an externally imparted force on barb 153). Subsequent to generating cut CT3, barb 159 may be resiliently biased such that barb 159 tends to assume a deployed position (e.g., in the absence of an externally imparted force on barb 159).
[0093] In some examples, cut CT1, cut CT2, and/or cut CT3 may be a single angle cut defining a substantially constant angle with body axis LS (e.g., constant or nearly constant to the extent permitted by manufacturing tolerances). In some examples, cut CT1, cut CT2, and/or cut CT3 may define two or more angles with body axis LS. For example, FIG. 10 depicts an example barb 194 defined by a cut CT4 defining a substantially constant angle AG1 with body axis LS. FIG. 11 depicts an example barb 196 defined by a cut CT5 defining a two angles AG2 and AG3 with body axis LS (e.g., cut CT5 may be a dual-angle cut). In examples, cut CT5 defines a free end 198 of barb 196 using angle AG2. In examples, angle AG2 is greater than angle AG3. Cut CT5 may define any number of angles with respect to body axis LS. Barb 194 and barb 196 are examples of barb 137.
[0094] In examples, a lead distal portion of implantable lead 112 includes a plurality of barbs arranged around lead outer surface in a substantially spiraled and/or helical pattern. In some examples, the plurality of barbs may be arranged to define the spiraled and/or helical shape around longitudinal axis L. For example, FIG. 12 is a perspective diagram illustrating a portion of example implantable medical lead 112 including a lead distal portion 202. FIG. 13 is an end view of distal portion 202. In FIG. 13, distal direction D proceeds out of the page and proximal direction P proceeds into the page. Lead distal portion 202 is an example of lead distal portion 120.
[0095] Lead distal portion 202 supports a plurality of barbs 204 (“barbs 204”). Barbs 204 may include, for example, barb 206, barb 208, barb 210, barb 212, barb 214, barb 216, barb 218, barb 220, barb 222, and/or others similarly depicted. In examples, barbs 204 are configured to extend radially outward from a barb base 226 having a base body 228. Base body 228 defines a body axis LS2 extending from a first body end 230 defined by base body 228 to a second body end 232 defined by base body 228. One or more of barbs 204 (e.g., substantially all) may extend radially outward (e.g., in radial direction R) from base body 228 between first body end 230 and second body end 232. In examples, lead outer surface 140 supports barb base 228. Barbs 204 are an example of barbs 136, 152, 158. Base body 228 is an example of base body 168. First body end 230 is an example of first body end 190. Second body end 232 is an example of second body end 192.
[0096] In examples, barb 206 includes a barb body 234 defining a free end 236 and a fixed end 238. Barb 206 is an example of barb 137. For example, lead distal portion 202 may define body radius RL extending in radial direction R from longitudinal axis L to outer surface 140. Barb 206 may define barb radius RB extending in radial direction R from outer surface 140 to free end 236 (e.g., when free end 236 is displaced from outer surface 140). In examples, barb 206 is configured to transition from the stowed position (e.g., when lead distal portion 202 is positioned within catheter lumen 149) to a deployed position when lead distal portion 202 is positioned distal to catheter lumen 149 (e.g., distal to catheter lumen opening 163).
[0097] For example, barb 206 (e.g., barb body 234) may be configured such that free end 236 defines first displacement DI (FIG. 4) in the stowed position. Barb 206 (e.g., barb body 234) may be configured such that free end 236 defines second displacement D2 (FIG. 5) in the deployed position. Barb 206 may be configured to substantially displace free end 236 (e.g., relative to lead outer surface 140 and/or longitudinal axis L) in the radial direction R when barb 206 transitions from the stowed position to the deployed position.
[0098] Barb body 234 may be configured such that body axis LS2 defines a helical shape surrounding longitudinal axis L. For example, barb body 234 may be configured such that first body end 230 is proximal to second body end 232 when barb body 234 extends around longitudinal access L. In examples, barbs 204 and/or base body 228 is configured to insert within a recess 240 defined by lead body 118 (e.g., lead outer surface 140) when lead outer surface 140 supports barbs 204. In examples, recess 240 extends from a first recess end 242 to a second recess end 244. Recess 240 is an example of recess 166. First recess end 242 is an example of first recess end 182. Second recess end 244 is an example of second recess end 184. In examples, support surface 186 (FIG. 5, FIG. 6) extends from first recess end 244 to second recess end 244. Recess 240 and second recess end 244 are depicted with dashed lines in FIG. 13. [0099] Lead distal portion 202 may be configured such that, when barbs 204 (e.g., barb 206) engage tissue, lead distal portion 202 provides a first rotational resistance when lead body 118 moves in a first rotational direction and provides a second rotational resistance different from the first rotational resistance when lead body 118 moves in a second rotational direction. Barb 206 may be configured to provide the first resistance greater than the second resistance. For example, barb 206 may be configured to provide the first rotational resistance when a torque is imparted on lead body 118 in a rotational direction RT1 around longitudinal axis L. Barb 206 may be configured to provide the second rotational resistance when a torque is imparted on lead body 118 in a rotational direction RT2 around longitudinal axis L opposite rotational direction RT1. Hence, lead distal potion 202 may be configured such that barb 206 resists rotation lead body 118 in the first rotational direction to a greater extent than a resistance to rotation of lead body 118 in the second rotational direction. In examples, fixation device 124 (e.g., auger member 132) is configured to increase its engagement with tissue as the torque is imparted in rotational direction RT2.
[0100] Barb 206 may be configured to provide the first rotational resistance by exerting a torque T1 in rotational direction RT1 when a given magnitude of torque is imparted to lead body 118 in rotational direction RT2 (e.g., by a clinician). Barb 206 may be configured to provide the second rotational resistance by exerting a torque T2 in rotational direction RT2 on lead body 118 when the given magnitude of torque is imparted to lead body 118 in rotational direction RT1 (e.g., by a clinician). In some examples, barb 206 is configured such that the torque T1 is greater than the torque T2, such that barb 206 resists rotation of lead body 118 in rotational direction RT2 to a greater extent than a resistance to rotation of lead body 118 in rotational direction RT1. Barb 206 may be configured to substantially flatten (e.g., decrease the distance D2 (FIG. 5)) when barb 206 is engaged with tissue and lead body 118 rotates in rotational direction RT1. In some examples, barb 206 is configured such that the torque T2 is greater than the torque Tl, such that barb 206 resists rotation of lead body 118 in rotational direction RT1 to a greater extent than a resistance to rotation of lead body 118 in rotational direction RT2. Barb 206 may be configured to substantially flatten (e.g., decrease the distance D2 (FIG. 5)) when barb 206 is engaged with tissue and lead body 118 rotates in rotational direction RT2.
[0101] In examples, fixation device 124 (e.g., auger member 132) is configured to increase its engagement with tissue as the torque is imparted in rotational direction RT2. For example, auger member 132 may be a right-handed auger when viewed in the distal direction D along longitudinal axis L. Barb 206 may be configured to provide a greater resistance to rotation of lead body 118 and auger member 132 when the magnitude of torque is imparted on lead body 118 in a counter-clockwise direction compared to the clockwise direction when viewed in the distal direction D along longitudinal axis L. In examples, fixation device 124 (e.g., auger member 132) is configured to increase its engagement with tissue as the torque is imparted in rotational direction RT1. For example, auger member 132 may be a left-handed auger when viewed in the distal direction D along longitudinal axis L. Barb 206 may be configured to provide a greater resistance to rotation of lead body 118 and auger member 132 when the magnitude of torque is imparted on lead body 118 in a clockwise direction compared to a counter-clockwise direction when viewed in the distal direction D along longitudinal axis L. [0102] Barb 206 may be configured to flexibly bend in the distal direction D when a distally directed force is imparted on barb body 234. For example, barb body 234 may be configured to move from the deployed position (depicted in FIG. 12 and FIG. 13) to the distal position when delivery catheter 151 imparts the distally directed force. In examples, when barb 206 transitions from the deployed position to the distal position, free end 236 displaces from fixed end 238 in the distal direction D. For example, barb body 234 may be configured such that free end 236 is proximal to, substantially even with, or distal to fixed end 238 when barb 206 is in the deployed position. When barb 206 transitions from the deployed position to the distal position, barb body 234 may be configured to displace free end 236 from fixed end 238 in the distal direction D and/or increase a displacement of free end 236 from fixed end 238 in the distal direction D. [0103] In examples, delivery catheter 151 (e.g., catheter distal end 165) is configured to impart the distally directed force on barb body 234 when delivery catheter 151 (e.g., catheter lumen opening 163) moves from a first position proximal to barb 206 to the second position distal to barb 206. In examples, delivery catheter 151 is configured such that lumen diameter LD causes catheter distal end 165 to impart the distally directed force on barb body 206 when catheter distal end 165 moves from a position proximal to barb 137 to a position distal to barb 137. Barb 206 (e.g., barb body 234) may be configured such that fixed end 238 is substantially stationary relative to lead body 118 when free end 236 moves from the deployed position to the distal position. Catheter inner surface 157 may be configured to impart a force on barb body 234 (e.g., a force toward longitudinal axis L) to substantially hold barb 234 in the distal position. For example, catheter inner surface 157 may be configured to impart the force holding barb 234 in the distal position when catheter distal end 165 is distal to barb 234.
[0104] In examples, fixation device 124 defines a helix. For example, FIG. 14 is a perspective diagram illustrating a portion of example implantable medical lead 112 including a lead distal portion 260 including a fixation device 261. FIG. 15 is an end view of distal portion 260. In FIG. 15, distal direction D proceeds out of the page and proximal direction P proceeds into the page. Fixation device 261 includes a fixation device body 262 defining a helix member 264 defining a helical shape (e.g., a helical shape around longitudinal axis L). Lead distal portion 202 is an example of lead distal portion 120, 202.
[0105] Fixation device body 262 (e.g., helix member 264) may extend distal to lead distal end 128 to a fixation device distal end 266. In examples, fixation device 261 includes a conductor (e.g., an electrically conductive material). In examples, fixation device body 262 is a conductor. The conductor may have a non-conductive coating, such as but not limited to polytetrafluoroethylene (PTFE). The conductor of fixation device 261 is electrically connected to a conductor of implantable medical device 112 (e.g., second conductor 115 (FIG. 4)). In some examples, the conductor of fixation device 261 comprises (e.g., is an extension of) the conductor of implantable medical lead 112. Fixation device 261 (e.g., fixation device body 262) may support fixation device electrode 130 (e.g., between lead distal end 128 and fixation device distal end 266. In some examples, fixation device electrode 130 is a portion of fixation device body 262. For example, when fixation device body 262 is substantially covered by the non-conductive coating, fixation device electrode 130 may be a portion of fixation device body 262 uncoated by the non-conductive coating. In some examples, fixation device electrode 130 may comprise a portion of fixation device body 262 between lead distal end 128 and fixation device distal end 266. In some examples, fixation device electrode 130 may be a component supported by but substantially separable from fixation device body 266. Fixation device 261 may be configured such that fixation device electrode 130 is exposed to tissue when fixation device body 262 (e.g., helix member 264) is embedded in tissue (e.g., tissue at or around target site 114 (FIG. 1)). The conductor of fixation device 261 may be configured to electrically connect fixation device electrode 130 with therapy delivery circuitry 127 and/or sensing circuitry 129 (FIG. 1)
[0106] Helix member 264 may be a right-handed helix when viewed in the distal direction D along longitudinal axis L (e.g., when barb 206 (FIG 12) is configured to provide a greater resistance to rotation of lead body 118 when torque is imparted in rotational direction RT1). In examples, helix member 264 may be a left-handed helix when viewed in the distal direction D along longitudinal axis L (e.g., when barb 206 (FIG 12) is configured to provide a greater resistance to rotation of lead body 118 when torque is imparted in rotational direction RT2). [0107] As used here, when a first portion of a system (e.g. medical system 12) is substantially parallel to a second portion of or an axis defined by the system, this may mean the first portion is parallel or nearly parallel to the second portion or the axis to the extent permitted by manufacturing tolerances. In some examples, when the first portion is substantially parallel to the second portion or the axis, this may mean a first vector defined by the first component of the system defines an angle of less than 10 degrees, in some examples less than 5 degrees, and in some examples less than 1 degree, with a second vector defined by the second component or the axis. When a first portion of the system is substantially perpendicular to a second portion of or an axis defined by the system, this may mean the first portion is perpendicular or nearly perpendicular to the second portion or the axis to the extent permitted by manufacturing tolerances. In some examples, when the first portion is substantially perpendicular to the second portion or the axis, this may mean that the first vector defined by the first component of the system defines an angle of at least 80 degrees, in some examples at least 85 degrees, and in some examples at least 89 degrees, with the second vector defined by the second component.
[0108] As used here, when a first portion of a system (e.g. medical system 12) supports a second portion of the system, this means that when the second portion causes a first force to be exerted on the first portion, the first portion causes a second force to be exerted on the second portion in response to the first force. The first force and/or second force may be a contact driving force and/or an action-at-a-distance driving force. For example, first force and/or second force may be mechanical driving force, a magnetic driving force, a gravitational driving force, or some other type of driving force. The first portion of the system may be a portion of the system or a portion of a component of the system. The second portion of the system may be another portion of the system or another portion of the same component or a different component. In some examples, when the first portion of the system supports the second portion of the system, this may mean the second portion is mechanically supported by and/or mechanically connected to the first portion. [0109] IMD 126 may include therapy delivery circuitry 127, sensing circuitry 129, processing circuitry 131, communication circuitry 133, memory 135, sensors, and/or other components. In some examples, memory 135 includes computer- readable instructions that, when executed by processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, communication circuitry 133, and/or other circuitry, cause IMD 126 and processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, communication circuitry 133, and/or other circuitry to perform various functions attributed to IMD 126 and processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, communication circuitry 133, and/or other circuitry herein. Memory 135 may include any volatile, non-volatile, magnetic, optical, or electrical media, such as a random access memory (RAM), read-only memory (ROM), nonvolatile RAM (NVRAM), electrically-erasable programmable ROM (EEPROM), ferroelectric RAM (FRAM), flash memory, or any other digital media.
[0110] Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, communication circuitry 133, and/or other circuitry may include fixed function circuitry and/or programmable processing circuitry. Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, communication circuitry 133, and/or other circuitry may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or equivalent discrete or analog logic circuitry. In some examples, Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, communication circuitry 133, and/or other circuitry may include multiple components, such as any combination of one or more microprocessors, one or more controllers, one or more DSPs, one or more ASICs, or one or more FPGAs, as well as other discrete or integrated logic circuitry. The functions attributed to Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, communication circuitry 133, and/or other circuitry herein may be embodied as software, firmware, hardware or any combination thereof.
[0111] In some examples, processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, and/or other circuitry may receive (e.g., from an external device), via communication circuitry 133, a respective value for each of a plurality of cardiac sensing parameters, cardiac therapy parameters (e.g., cardiac pacing parameters), and/or electrode vectors. Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, and/or other circuitry may store such parameters and/or electrode vectors in memory 135. Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, and/or other circuitry may be electrically coupled to electrode 130, 142. Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, and/or other circuitry may generate and deliver electrical therapy to heart 122 via electrode 130, 142. Electrical therapy may include, for example, pacing pulses, or any other suitable electrical stimulation. Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, and/or other circuitry may deliver electrical stimulation therapy via electrode 130, 142 according to one or more therapy parameter values, which may be stored in memory 135. Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, and/or other circuitry may include capacitors, current sources, and/or regulators, in some examples.
[0112] Processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, and/or other circuitry may be configured to monitor signals from electrodes 130, 142 in order to monitor electrical activity of heart 122. Sensing circuitry 129 may include circuits that acquire electrical signals, such as filters, amplifiers, and analog-to-digital circuitry. Electrical signals acquired by sensing circuitry 129 may include intrinsic and/or paced cardiac electrical activity, such as atrial depolarizations and/or ventricular depolarizations. Sensing circuitry 129 may filter, amplify, and digitize the acquired electrical signals to generate raw digital data. Processing circuitry 131 may receive the digitized data generated by sensing circuitry 129. In some examples, processing circuitry 131 may perform various digital signal processing operations on the raw data, such as digital filtering. Communication circuitry 133 may include any suitable hardware (e.g., an antenna), firmware, software, or any combination thereof for communicating with another device, e.g., external to the patient.
[0113] IMD 126 may include a housing 121 configured to enclose processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, communication circuitry 133, memory 135, and/or other circuitry within medical system 100. Housing 121 may be configured to fluidly isolate processing circuitry 131, therapy delivery circuitry 127, sensing circuitry 129, communication circuitry 133, memory 135, and/or other circuitry from an environment in contact with an exterior surface of housing 121.
[0114] A technique for supporting a plurality of barbs is illustrated in FIG. 16. Although the technique is described mainly with reference to medical system 100 of FIGS. 1-15, the technique may be applied to other medical systems in other examples. [0115] The technique includes defining, using a biostable material, an outer surface 140 of a lead body 118 of a lead distal portion 120, 202, 260 of an implantable medical lead 112 (1402). Lead body 118 may support a fixation device 124, 261. In examples, lead body 118 supports fixation device 124, 261 such that fixation device 124, 261 extends distal to a lead distal end 128. Fixation device 124, 261 may support a fixation device electrode 130 electrically coupled to processing circuitry 131, therapy delivery circuitry 127, and/or other circuitry of an implantable medical device 112.
[0116] The technique includes supporting, using outer surface 140, barbs 136, 152, 158, 204 comprising a biodegradable material (1404). Outer surface 140 may support barbs 136, 152, 158, 204 at a position proximal to fixation device 124, 261. In examples, outer surface 140 supports barbs 136, 152, 158, 204 at a position proximal to fixation device 124, 261 and distal to a body electrode 142 of lead distal portion 120, 202, 260. In examples, the technique includes extending, using a resilient biasing, barbs 136, 152, 158, 204 in a direction radially outward from outer surface 140. In examples, barbs 136, 152, 158, 204 extend in a radial direction R from a longitudinal axis L extending through a lead body 118 and lead distal end 128.
[0117] Lead body 118 may define a body radius RL extending in radial direction R from longitudinal axis L to outer surface 140. Barb 137 may define a barb radius RB extending in radial direction R from outer surface 140 to a free end 144 of barb 137. Barb radius RB may be less than about thirty percent of body radius RL. In examples, the resilient biasing causes barb 137 to transition from a stowed position defining a distance DI to a deployed position defining a distance D2 greater than distance DI. In some examples, a catheter inner surface 157 holds barb 137 in the stowed position. The resilient biasing may cause barb 137 to transition to the deployed position when barb 137 is moved relative to a catheter body 147 to a position distal to a catheter lumen opening 163. In examples, barb 137 transitions from the deployment position to a distal position when barb 137 is moved relative to a catheter body 147 from the position distal to a position proximal to a catheter lumen opening 163.
[0118] Outer surface 140 may support barbs 136, 152, 158, 205 within a recess 166, 240 defined by outer surface 140. In examples, base body 168, 228 supports barbs 136, 152, 158, 204 and outer surface 140 supports base body 168, 228. In some examples, base body 168, 228 is inserted within recess 166, 240. Base body 168, 228 may defines a body axis LS, LS2 extending from a first body end 190, 230 to a second body end 192, 232. In some examples, body axis LS, LS2 is parallel to longitudinal axis L when base body 168, 228 inserts into recess 166, 240. In some examples, body axis LS, LS2 defines a spiral and/or helical shape surrounding longitudinal axis L when base body 168, 228 inserts into recess 166, 240.
[0119] Various examples of the disclosure have been described. Any combination of the described systems, operations, or functions is contemplated. These and other examples are within the scope of the following claims.
[0120] The following are illustrative of the techniques described herein.
[0121]
[0121] Example 1 : An implantable medical lead configured to implant within tissues of a patient, the comprising; a lead body comprising a biostable material defining an outer surface and a distal end, wherein the lead body defines a longitudinal axis surrounded by the outer surface and extending through the distal end; a fixation device supported by the lead body and extending distal to the distal end, wherein the fixation device is configured to insert within tissues of a patient; and a plurality of barbs supported by the outer surface and proximal to the fixation device, wherein the plurality of barbs is positioned around the longitudinal axis, wherein the plurality of barbs are configured to extend radially outward from the outer surface, wherein the plurality of barbs are configured to engage the tissues when the plurality of barbs are inserted into the tissues, and wherein the plurality of barbs comprise a biodegradable material configured to degrade in a fluid of the patient.
[0122] Example 2: The implantable medical lead of example 1, further comprising an electrode supported by the lead body, wherein the electrode is proximal to the plurality of barbs.
[0123] Example 3: The implantable medical lead of example 1 or example 2, wherein a barb in the plurality of barbs includes a barb body defining a fixed end supported by the lead body and defining a free end opposite the fixed end, wherein the barb body is resiliently biased to extend radially outward from the outer surface.
[0124] Example 4: The implantable medical lead of example 1 or example 2, wherein a barb in the plurality of barbs includes a barb body defining a fixed end supported by the lead body and defining a free end opposite the fixed end, and wherein the barb body is resiliently biased to transition from a stowed position wherein the free end defines a first displacement from the outer surface to a deployed position wherein the free end defines a second displacement from the free end to the outer surface, wherein the second displacement is greater than the first displacement.
[0125] Example 5: The implantable medical lead of example 4, wherein the barb body is configured to bend from the deployed position to a distal position, and wherein the barb body is configured to increase a distal displacement between the free end and the fixed end when the barb body transitions from the deployed position to the distal position.
[0126] Example 6: The implantable medical lead of example 5, wherein the barb body is resiliently biased to transition from the distal position to the deployed position.
[0127] Example 7: The implantable medical lead of any of examples 4-6, further comprising a catheter including a catheter body defining a lumen and defining a lumen opening which opens to the lumen at a distal end of the catheter body, wherein the fixation device, the plurality of barbs, and the lead body are configured to translate within the lumen and through the lumen opening, and wherein the catheter body is configured to trap the barb body to overcome the resilient biasing when the plurality of barbs is within the lumen and proximal to the lumen opening.
[0128] Example 8: The implantable medical lead of any of examples 3-7, wherein the barb body is configured to position the free end proximal to the fixed end in the stowed position and in the deployed position.
[0129] Example 9: The implantable medical lead of any of examples 3-8, wherein: the lead body defines a body radius extending substantially perpendicularly from the longitudinal axis to the outer surface, the barb body defines a barb radius substantially parallel to the body radius and extending from outer surface to the free end when the barb body is in the deployed position, and the barb radius is less than thirty percent of the body radius. [0130] Example 10: The implantable medical lead of any of examples 3-9, wherein the fixed end is coupled to a barb base, and wherein the barb base is inserted into a recess defined by the lead body.
[0131] Example 11 : The implantable medical lead of any of example 10, wherein the barb base, the fixed end, and the free end define a unified body.
[0132] Example 12: The implantable medical lead of example 11, wherein the unified body defines a cut extending radially inward toward the longitudinal axis, and wherein the cut separates the free end and the barb base.
[0133] Example 13: The implantable medical lead of any of examples 10-12, wherein the unified body defines a plane passing through the longitudinal axis and the recess, wherein the recess is configured to define at least one curvature within the plane.
[0134] Example 14: The implantable medical lead of any of examples 1-13, wherein the fixation device defines a auger surrounding the longitudinal axis and configured to engage the tissues of the patient when the fixation device is inserted within the tissues of the patient.
[0135] Example 15: The implantable medical lead of any of example 1-14, wherein the biostable material has a first solubility in an aqueous environment and the biodegradable material has a second solubility greater than the first solubility in the aqueous environment.
[0136] Example 16: The implantable medical lead of any of examples 1-15, further comprising a second plurality of barbs supported by the outer surface and proximal to the plurality of barbs, wherein the second plurality of barbs is positioned around the longitudinal axis, wherein the second plurality of barbs are resiliently biased to extend radially outward from the outer surface, wherein the second plurality of barbs are configured to engage the tissues when the second plurality of barbs are inserted into the tissues, and wherein the second plurality of barbs comprise a biodegradable material configured to degrade in the fluid of the patient. [0137] Example 17: The implantable medical lead of any of examples 1-16, wherein the plurality of barbs are positioned along a closed perimeter surrounding the longitudinal axis.
[0138] Example 18: The implantable medical lead of any of examples 1-17, wherein the plurality of barbs are positioned along a auger surrounding the longitudinal axis.
[0139] Example 19: The implantable medical lead of any of examples 1-18, wherein the biodegradable material is a biodegradable polymer.
[0140] Example 20: The implantable medical lead of example 19, wherein the biodegradable polymer is a copolymer of glycolic acid and trimethylene carbonate.
[0141] Example 21: The implantable medical lead of any of examples 1-20, wherein the biodegradable material is configured to be metabolized by the patient.
[0142] Example 22: The implantable medical lead of any of examples 1-21, wherein: the plurality of barbs are configured to impart a distally directed force on the lead body when the plurality of barbs engage the tissues and a force having a magnitude is imparted on the lead body in a proximal direction, the plurality of barbs are configured to impart a proximally directed force on the lead body when the plurality of barbs engage the tissues and the force having the magnitude is imparted on the lead body in a distal direction, and the plurality of barbs are configured such that the distally directed force is greater than the proximally directed force.
[0143] Example 23: A method, comprising: defining, using a biostable material, an outer surface of a lead body surrounding a longitudinal axis of the lead body and a distal end of the lead body;supporting, using a distal end of the lead body, a fixation device configured to engage tissues; defining, using a biodegradable material, a plurality of barbs supported by the outer surface and proximal to the fixation device; and extending, using a resilient biasing of the plurality of barbs, the plurality of barbs radially outward from the outer surface. [0144] Example 24: The method of example 23 further comprising supporting, using the lead body, an electrode in a position proximal to the plurality of barbs.
[0145] Example 25: The method of example 23 or example 24, further comprising: supporting, using the lead body, a fixed end of a barb of the plurality of barbs; and transitioning, using the resilient biasing, the barb from a stowed position wherein a free end opposite the fixed end defines a first displacement from the outer surface to a deployed position wherein the free end defines a second displacement from the outer surface, wherein the second displacement is greater than the first displacement.
[0146] Example 26: The method of example 25, further comprising increasing, using a distal end of a delivery catheter, a distal displacement between the free end and the fixed end.
[0147] Example 27: The method of example 26, further comprising decreasing, using the resilient biasing, the distal displacement between the free end and the fixed end.
[0148] Example 28: The method of any of examples 25-27, further comprising positioning, using the resilient biasing, the free end distal to the fixed end.
[0149] Example 29: The method of any of examples 25-28, further comprising: defining, using the lead body, a body radius extending substantially perpendicularly from the longitudinal axis to the outer surface, defining, using the resilient biasing, a barb radius substantially parallel to the body radius and extending from outer surface to the free end, wherein the barb radius is less than thirty percent of the body radius.
[0150] Example 30: The method of any of examples 25-29, further comprising supporting, using a recess of the outer surface, a barb base supporting the fixed end.
[0151] Example 31 : The method of any of examples 23-30, further comprising: engaging, using the fixation device, the tissues of a patient; and engaging, using the plurality of barbs, the tissue of the patient as the fixation device engages the tissues of the patient.
[0152] Example 32: The method of any of examples 23-31, further comprising trapping, using a catheter body of a catheter, the plurality of barbs to overcome the resilient biasing when the plurality of barbs is within a lumen defined by the catheter body.
[0153] Example 33: The method of any of examples 23-32, further comprising extending, using a resilient biasing of a second plurality of barbs, the second plurality of barbs radially outward from the outer surface.