Fixation mechanism for implantable medical device

Abstract

One or more examples include an implantable medical device (IMD) including: an elongated housing extending along a longitudinal axis from a proximal housing end to a distal housing end; a tapered header extending distally from the distal housing end, the tapered header defining one or more helical threads extending around an outer surface of the tapered header; and an electrode extending distally from a distal end of the tapered header, wherein the IMD is configured to be implanted within a chamber of a heart of a patient, and wherein the tapered header is configured to at least partially penetrate cardiac tissue of the chamber of the heart as the tapered header is rotated about the longitudinal axis to cause the one or more helical threads to engage with the cardiac tissue, and wherein the tapered header is configured to inhibit unintended rotation of the IMD within the cardiac tissue.

Description

Atty Ref. No. A0013522W001FIXATION MECHANISM FOR IMPLANTABLE MEDICAL DEVICETECHNICAL FIELD

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 746,716, filed January 17, 2025, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

[0002] The disclosure relates to medical devices, and more particularly to fixation mechanisms of medical devices.BACKGROUND

[0003] Various types of implantable medical devices (IMDs) have been implanted for treating or monitoring one or more conditions of a patient. Such IMDs may be adapted to monitor or treat conditions or functions relating to heart, muscle, nerve, brain, stomach, endocrine organs or other organs and their related functions. Such IMDs may be associated with leads that position electrodes at a desired location or may be leadless with electrodes integrated with and / or attached to the device housing. These IMDs may have the ability to wirelessly transmit data either to another device implanted in the patient or to another instrument located externally of the patient, or both.

[0004] A cardiac pacemaker is an IMD configured to deliver cardiac pacing therapy to restore a more normal heart rhythm. Such HMDs sense the electrical activity of the heart, and deliver cardiac pacing based on the sensed electrical activity, via electrodes. Some cardiac pacemakers are implanted a distance from the heart and coupled to one or more leads that intravascularly extend into the heart to position electrodes with respect to cardiac tissue. Some cardiac pacemakers are sized to be completely implanted within one of the chambers of the heart and may include electrodes integrated with or attached to the device housing rather than leads. Some cardiac pacemakers provide dual chamber functionality, by sensing and / or stimulating the activity of both atria and ventricles, or other multi-chamber functionality. A cardiac pacemaker may provide multi-chamber functionality via leads that extend to respective heart chambers, or multiple cardiacAtty Ref. No. A0013522W001pacemakers may provide multi-chamber functionality by being implanted in respective chambers.SUMMARY

[0005] In general, this disclosure is directed to implantable medical devices (IMDs) configured to sense and deliver electrical signals to tissue of a patient via a plurality of electrodes at or near a distal end of an elongated housing of the HMD.

[0006] In some examples, a single IMD is implanted in a chamber of a heart of the patient and is able to sense signals from and / or deliver cardiac pacing to cardiac tissue of a chamber of the heart (e.g., the same chamber the IMD is implanted in, another chamber separate from the chamber the IMD is implanted in). In some examples, such an implantable medical device includes a distal electrode that is configured to penetrate through wall tissue of the heart chamber in which the device is implanted (e.g., and into wall tissue of another heart chamber). The distal electrode may extend to or towards another chamber of the heart. Depending on the position and / or orientation of a target implantation site within the chamber of the heart, the distal electrode may need to be implanted at different depths within the wall tissue, e.g., to position the distal electrode at a specific location and / or orientation within the wall tissue.

[0007] This disclosure describes devices, systems, and techniques for affixing the distal electrode of the IMD at varying depths within the wall tissue of the heart. The IMD include or may be coupled to a tapered header at or around a distal end of the IMD. The tapered header may define one or more helical threads extending around an outer surface of the tapered header. A clinician may rotate the tapered header (e.g., about a longitudinal axis) to cause the tapered header to penetrate the cardiac tissue and to cause the one or more helical threads to engage with the cardiac tissue. The clinician may adjust the position of the distal electrode within the cardiac tissue by rotating the tapered header. The one or more helical threads and / or the outer surface of the tapered header may interface (e.g., interlock) with the cardiac tissue to inhibit unintended movement and / or rotation of the IMD within the tissue.

[0008] In some examples, this disclosure is directed to an implantable medical device (IMD) comprising: an elongated housing extending along a longitudinal axis from a proximal housing end to a distal housing end; a tapered header extending distally from theAtty Ref. No. A0013522W001distal housing end, the tapered header defining one or more helical threads extending around an outer surface of the tapered header; and an electrode extending distally from a distal end of the tapered header, wherein the IMD is configured to be implanted within a chamber of a heart of a patient, and wherein the tapered header is configured to at least partially penetrate cardiac tissue of the chamber of the heart as the tapered header is rotated about the longitudinal axis to cause the one or more helical threads to engage with the cardiac tissue, and wherein the tapered header is configured to inhibit unintended rotation of the IMD within the cardiac tissue.

[0009] In some examples, this disclosure is directed to a fixation device for an implantable medical device (IMD), the fixation device comprising: a tapered header extending distally from a distal housing end of the IMD, the tapered header defining: one or more helical threads extending around an outer surface of the tapered header, wherein the tapered header is configured to at least partially penetrate tissue of patient as the tapered header is rotated about a longitudinal axis to cause the one or more helical threads to engage with the tissue, and wherein the tapered header is configured to inhibit unintended rotation of the IMD relative to the tissue.

[0010] In some examples, this disclosure is directed to a method comprising: inserting an implantable medical device (IMD) within a chamber of a heart of a patient, the IMD comprising: an elongated housing extending along a longitudinal axis from a proximal housing end to a distal housing end; a tapered header extending distally from the distal housing end of the elongated housing, the tapered header defining one or more helical threads extending around an outer surface of the tapered header; and an electrode extending distally from a distal header end of the tapered header; advancing the tapered header at least partially into cardiac tissue of the chamber of the heart by rotating the tapered header about the longitudinal axis to cause the electrode and the one or more helical threads to engage with the cardiac tissue, wherein the tapered header inhibits unintended rotation of the IMD within the cardiac tissue; and delivering, by the IMD and via the electrode, electrical stimulation signals to the cardiac tissue.

[0011] In some examples, this disclosure is directed to an implantable medical device (IMD) comprising: an elongated housing extending along a longitudinal axis from a proximal housing end to a distal housing end; a tapered header extending distally from the distal housing end; an electrode including an electrode shaft extending distally from aAtly Ref. No. A0013522W001distal end of the tapered header; and the tapered header and / or the electrode shaft defining one or more helical threads extending around an outer surface of the tapered header and / or electrode shaft; wherein the IMD is configured to be implanted within a chamber of a heart of a patient, and wherein the one or more helical threads are configured to at least partially penetrate cardiac tissue of the chamber of the heart as the IMD is rotated about the longitudinal axis to cause the one or more helical threads to engage with the cardiac tissue, and wherein the tapered header and / or the electrode shaft is configured to inhibit unintended rotation of the IMD within the cardiac tissue.

[0012] This summary is intended to provide an overview of the subject matter described in this disclosure. It is not intended to provide an exclusive or exhaustive explanation of the methods and systems described in detail within the accompanying drawings and description below.BRIEF DESCRIPTION OF DRAWINGS

[0013] The details of one or more examples of this disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of this disclosure will be apparent from the description and drawings, and from the claims.

[0014] FIG. l is a conceptual diagram illustrating an example device implanted in the heart of a patient, in accordance with one or more aspects of this disclosure.

[0015] FIG. 2 is a block diagram illustrating an example configuration of an example device of FIG. 1.

[0016] FIG. 3 is a perspective diagram illustrating an example configuration of the device of any of FIGS. 1-2.

[0017] FIG. 4A is a perspective diagram illustrating another example configuration of the device of any of FIGS. 1-3.

[0018] FIG. 4B is a perspective diagram illustrating another example configuration of the device of any of FIGS. 1-3.

[0019] FIG. 5 is a perspective diagram illustrating another example configuration of the device of any of FIGS. 1-3.

[0020] FIG. 6A is a perspective diagram illustrating another example configuration of the device of any of FIGS. 1-3.Atty Ref. No. A0013522W001

[0021] FIG. 6B is a perspective diagram illustrating another example configuration of the device of any of FIGS. 1-3.

[0022] FIG. 6C is a perspective diagram illustrating another example configuration of the device of any of FIGS. 1-3.

[0023] FIG. 7A is a is a perspective diagram illustrating an example implantation of the device of any of FIGS. 1-6C within tissue of a patient.

[0024] FIG. 7B is a is a perspective diagram illustrating an example implantation of the device of any of FIGS. 1-6C within tissue of a patient.

[0025] FIG. 7C is a is a perspective diagram illustrating an example implantation of the device of any of FIGS. 1-6C within tissue of a patient.

[0026] FIG. 8 is a flowchart illustrating an example process for sensing a cardiac electrical signal and delivering cardiac pacing therapy to a heart of a patient via an example device of any of FIGS. 1-7C.DETAILED DESCRIPTION

[0027] In general, this disclosure is directed to distal end configurations for implantable medical devices (IMDs). More particularly, this disclosure is directed to HMDs, such as leadless pacemakers (LPs), with an elongated body extending distally from the distal end of the IMD. The IMD may be coupled to a sheath disposed around the distal end of the IMD. The sheath may interface with corresponding features on the IMD to control the distal movement of the IMD during implantation, e.g., thereby controlling an implantation depth of the elongated body within tissue of a patient (e.g., within cardiac tissue of the patient).

[0028] FIG. 1 is a conceptual diagram illustrating an example device 104 implanted in heart 102 of a patient, in accordance with one or more aspects of this disclosure. Device 104 is shown implanted in the right ventricle (RV) of the patient’s heart 102 in a target implant region 106 in heart 102 of the patient with a distal end of device 104 directed toward the left ventricle (LV) of the patient’s heart 102. Although in the example of FIG.1 the distal end of device 104 is directed toward the LV, the distal end may be directed to other targets, such as interventricular septum of heart 102. In some examples, target implant region 106 may be disposed in another position within heart 102, e.g., within a right atrium (RA) of heart 102. In some examples (not pictured in FIG. 1), target implantAty Ref. No. A0013522W001region 106 may be located at or around the Bachmann’s bundle of heart 102 and / or a septal wall of the RA of heart 102. In such examples, the variable implantation depth of device 104, as described in greater detail below, may increase a range of possible target implant regions 106 for device 104. The variable implantation depth of device 104 may also provide for increased adaptability of device 104 to the varying anatomies of hearts 102 of different patients. Device 104 may include, but is not limited to, a transseptal device.

[0029] Device 104 includes a distal end 110 and a proximal end 116. Distal end 110 includes distal electrode 112 and tapered header 114. Distal electrode 112 may be disposed along an elongated body extending to a distal end. In such examples, distal electrode 112 may be disposed along the elongated body at a position proximal to the distal end of the elongated body. The elongated body may define a helical shape, an elongated barb, or any other elongated shape. Distal electrode 112 may define the entire elongated body and an electrically active region of distal electrode 112 may be disposed at or proximal to the distal end of the elongated body.

[0030] The elongated body and distal electrode 112 extends from distal end 110 and may penetrate into the wall tissue of a chamber of heart 102 (e.g., the RV of heart 102). Distal electrode 112 may penetrate through the wall tissue of a first chamber (e.g., RV) and towards wall tissue of a second chamber (e.g., LV). For example, a portion of distal electrode 112 may penetrate through cardiac tissue and be disposed at or around a left bundle branch (LBB) of heart 102. Tapered header 114 can comprise any suitable tapering structure, member or transition, located between distal electrode 112 and proximal portion(s) of device 104, e.g., housing 202. Tapered header 114 can comprise a distal portion of housing 202 and / or a proximal portion of electrode 112. In lieu of tapered header 114, a non-tapered header, structure, member, or transition may be employed when implementing any embodiment of the devices (e.g., device 104) disclosed herein.

[0031] Depending on the location of target implantation region 106 and / or a position of target cardiac tissue, the implantation depth for distal electrode 112 may vary. Tapered header 114 may define one or more helical threads extending around an outer surface of tapered header 114. The clinician may rotate tapered header 114 (e.g., about a longitudinal axis) to advance at least a portion of the one or more helical threads and / or a body of tapered header 114 into the cardiac tissue. The clinician may control the implantationAtly Ref. No. A0013522W001depth of distal electrode by advancing and / or retracting tapered header 114 from within the cardiac tissue. For example, the clinician may rotate tapered header 114 in a first direction to further advance distal electrode 112 into the cardiac tissue and rotate tapered header 114 in an opposite direction to retract distal electrode 112 from within the cardiac tissue. The one or more helical threads and / or an outer surface of tapered header 114 may interface with the cardiac tissue to inhibit unintended movement and / or rotation of device 104 from within the cardiac tissue.

[0032] The configuration of distal electrode 112 illustrated in FIG. 1 allows device 104 to sense cardiac signals and / or deliver cardiac pacing to one or more chambers of heart 102, e.g., the RV, LV, and / or the conduction system of either or both in the illustrated example. In this manner, the configuration of distal electrode 112 may facilitate the delivery of pacing by single device 104 implanted within the single chamber, e.g., the RV. While device 104 is implanted at target implant region 106 to sense in and / or pace the ventricle(s) in the example shown in FIG. 1, a device having an electrode configuration in accordance with the examples of this disclosure may be implanted at any of a variety of locations to sense in and / or pace any one, two or more chambers of heart 102. For example, device 104 may be implanted at region 106 or another region, and distal electrode 112 may extend into tissue, e.g., myocardial tissue, of the LV or interventricular septum. Furthermore, a device having an electrode configuration in accordance with the examples of this disclosure may be implanted at any of a variety of locations within a patient for sensing and / or delivery of therapy to other patient tissue, e.g., outside of heart 102.

[0033] FIG. 2 is a block diagram illustrating an example configuration of an example device 104 of FIG. 1. Device 104 may include one or more components disposed within housing 202. The one or more components may include, but is not limited to, switch circuitry 206, sensing circuitry 208, signal generation circuitry 210, sensor(s) 212, processing circuitry 214, telemetry circuitry 216, memory 218, and power source 220. The various circuitry may be, or include, programmable or fixed function circuitry configured to perform the functions attributed to respective circuitry. Memory 218 may store computer-readable instructions that, when executed by processing circuitry 214, cause device 104 to perform various functions. Memory 218 may be a storage device or other non-transitory medium.Atly Ref. No. A0013522W001

[0034] Signal generation circuitry 210 generates electrical stimulation signals, e.g., cardiac pacing pulses. Switch circuitry 206 is coupled to electrode 112 and reference electrode 204. Switch circuitry 206 may include one or more switch arrays, one or more multiplexers, one or more switches (e.g., a switch matrix or other collection of switches), one or more transistors, or other electrical circuitry. Switch circuitry 206 is configured to direct stimulation signals from signal generation circuitry 210 to electrodes 112 and 204, having selected polarities, e.g., to selectively deliver pacing pulses to one or more positions within heart 102. For example, in order to pace one or both of the ventricles, switch circuitry 206 may couple distal electrode 112, which has penetrated to wall tissue of a ventricle or the intraventricular septum, to signal generation circuitry 210 as a cathode, and electrode 204 to signal generation circuitry 210 as an anode.

[0035] Each of electrodes 112, 204 may be coupled to switch circuitry 206 via a corresponding feedthrough assembly. In some examples, each feedthrough assembly is substantially straight (e.g., along longitudinal axis 201). In some examples, such as tapered header 114 is removable from housing, the feedthrough assemblies are offset to allow for removal of tapered header 114. For example, when tapered header 114 is removably secured to housing 202 (e.g., via a turn-lock mechanism), the feedthrough assemblies are offset from a longitudinal axis of device 104 to allow tapered header 114 to turn relative to housing 202.

[0036] Switch circuitry 206 may also selectively couple sensing circuitry 208 to selected combinations of electrodes 112, 204, e.g., to selectively sense the electrical activity of one or more chambers of heart 102. Sensing circuitry 208 may include filters, amplifiers, analog-to-digital converters, or other circuitry configured to sense cardiac electrical signals via electrodes 112, 204. For example, switch circuitry 206 may couple distal electrode 112 (in combination with electrode 204) to a respective sensing channel provided by sensing circuitry 208 to sense ventricular cardiac electrical signals. In some examples, sensing circuitry 208 is configured to detect events, e.g., depolarizations, within the cardiac electrical signals, and provide indications thereof to processing circuitry 214. In this manner, processing circuitry 214 may determine the timing of atrial and ventricular depolarizations, and control the delivery of cardiac pacing based thereon. Processing circuitry 214 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-Atly Ref. No. A0013522W001programmable gate array (FPGA), discrete logic circuitry, or any other processing circuitry configured to provide the functions attributed to processing circuitry 214 herein may be embodied as firmware, hardware, software or any combination thereof.

[0037] Sensor(s) 212 may include one or more sensing elements that transduce patient physiological activity to an electrical signal to sense values of a respective patient parameter. Sensor(s) 212 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other types of sensors. Sensor(s) 212 may output patient parameter values that may be used as feedback to control sensing and delivery of therapy by device 104.

[0038] Telemetry circuitry 216 supports wireless communication between device 104 and an external programmer (not shown in FIG. 2) or another computing device under the control of processing circuitry 214. Processing circuitry 214 of device 104 may receive, as updates to operational parameters from the computing device, and provide collected data, e.g., sensed heart activity or other patient parameters, via telemetry circuitry 216.Telemetry circuitry 216 may accomplish communication by radiofrequency (RF) communication techniques, e.g., via an antenna (not shown).

[0039] Power source 220 delivers operating power to various components of device 104. Power source 220 may include a rechargeable or non-rechargeable battery and a power generation circuit to produce the operating power. Recharging may be accomplished through proximal inductive interaction between an external charger and an inductive charging coil within device 104.

[0040] FIG. 3 is a perspective diagram illustrating an example configuration of device 104 of any of FIGS. 1-2. Device 104 may include housing 202 extending from proximal end 305 (alternatively referred to herein as “proximal housing end 305”) to distal end 303 (alternatively referred to herein as “distal housing end 303”) along longitudinal axis 301. Housing 202 may optionally be elongated; however, any other suitable form or shape may be employed for housing 202. Tapered header 114 may be affixed to distal end 303 of housing 202 and may extend from proximal end 306 (alternatively referred to herein as “proximal header end 306”) to distal end 304 (alternatively referred to herein as “distal header end 304”). Distal end 303 of housing 202 may be the same as proximal end 306 of tapered header 114. Stylet 302 (alternatively referred to herein as “shaft 302”)may extend distally from distal end 304 of tapered header 114 and along longitudinal axis 301. DistalAtly Ref. No. A0013522W001electrode 112 may be disposed on or around a distal end of stylet 302. Distal electrode 112 may be an elongated helix, an elongated barb, a button electrode, or the like.

[0041] Housing 202 may define a hermetically sealed internal cavity. Housing 202 may be formed from a conductive material including titanium or titanium alloy, stainless steel, MP35N (a non-magnetic nickel-cobalt-chromium -molybdenum alloy), platinum alloy or other bio-compatible metal or metal alloy, or other suitable conductive material. In some examples, housing 202 is formed from a non-conductive material including ceramic, glass, sapphire, silicone, polyurethane, epoxy, acetyl co-polymer plastics, polyether ether ketone (PEEK), a liquid crystal polymer, other biocompatible polymer, or other suitable non-conductive material.

[0042] Housing 202 extends between distal end 303 and proximal end 305 along longitudinal axis 301. Housing 202 may be cylindrical or substantially cylindrical but may be other shapes, e.g., prismatic, or other geometric shapes. Housing 202 may include a delivery tool interface member 310, e.g., at proximal end 305, for engaging with a delivery tool during implantation of device 104.

[0043] Tapered header 114 may extend from proximal end 306 to distal end 304. An outer diameter of tapered header 114 may reduce along longitudinal axis 301 from proximal end 306 to distal end 304. Tapered header 114 may define an uniform or a varied reduction in the outer diameter. In some examples, as illustrated in FIG. 3, an outer diameter of tapered header 114 at or around proximal end 306 is the same as or substantially similar to an outer diameter of housing 202 at or around distal end 303. In such examples, at least a portion of housing 202 (e.g., at or around distal end 303) may be inserted into the cardiac tissue, e.g., after the entirety of tapered header 114 is inserted into the cardiac tissue.

[0044] In some examples, housing 202 and / or tapered header 114 defines a shoulder and / or step around proximal end 306 of tapered header 114. The shoulder and / or step may define a stepped difference between the outer diameter of tapered header 114 at or around proximal end 306 and the outer diameter of housing 202 at or around distal end 306. The shoulder and / or step may inhibit insertion of housing 202 into the cardiac tissue, e.g., after the entirety of tapered header 114 is inserted into the cardiac tissue.

[0045] Tapered header 114 may define an outer diameter at or around distal end 304 greater than or equal to an outer diameter of stylet 302. Tapered header 114 and / or styletAtly Ref. No. A0013522W001302 may be formed from an electrically insulating material and / or may be coated with an electrically insulating material, e.g., to control an electrically active surface area of electrode 112. Stylet 302 may define a longitudinal length of about 4-8millimeters (mm) from a base of stylet 302 to a distal end of electrode 112. Tapered header 114 may define a longitudinal length between proximal end 306 and distal end 304 of about 4-8 mm. An overall longitudinal length between distal end 303 of housing 202 and electrode 112 may be about 12 mm.

[0046] In some examples, tapered header 114 is formed from an electrically conductive material (e.g., a metallic alloy such as, but is not limited to Titanium), a biocompatible polymer (e.g., Poly ether etherketone (PEEK)). In some examples, tapered header 114 is formed from a polymeric or metallic substrate. At least a portion of an outer surface tapered header 114 may be coated with or disposed with an electrically active material, e.g., to define one or more second electrodes on tapered header 114. The second electrode(s) may form a complete electrical circuit with electrode 112, e.g., instead of or in addition to electrode 204. Forming an electrical circuit between electrode 112 and second electrode(s) may provide improved sensing performance (e.g., compared to other IMDs or implantable leads), e.g., by reducing the effect of far-field P-waves and T-waves on the sensed signals. Electrode 112 may be integral to stylet 302. For example, stylet 302 may be formed from a biocompatible polymer and may electrically insulate a proximal portion of electrode 112 disposed within stylet 302. Stylet 302 may not define an inner lumen.

[0047] Tapered header 114 define helical thread(s) 308 around an outer surface of tapered header 114. In some examples, helical thread(s) 308 may be disposed over stylet 302 and / or electrode 112 in addition to or instead of on tapered header 114.

[0048] Helical thread(s) 308 may extend along a portion of or an entirety of the longitudinal length of tapered header 114. Helical thread(s) 308 may extend radially away from the outer surface of tapered header 114. Helical thread(s) 308 may define a uniform or varied pitch. For example, the pitch of helical thread(s) 308 may increase or decrease as helical thread(s) 308 progress towards distal end 304 of tapered header 114. Helical thread(s) 308 may define a uniform or varied depth. For example, the depth of helicalAty Ref. No. A0013522W001thread(s) 308 may increase or decrease as helical thread(s) 308 progress towards distal end 304 of tapered header 114.

[0049] Helical thread(s) 308 may complete less than one, one, or more than one complete revolutions around an outer perimeter of tapered header 114. Helical thread(s) 308 may be wound in a same or difference direction as an elongated helix defining electrode 112. Fixation feature(s) may be disposed on tapered header 114. Fixation feature(s) may include, but are not limited to, tines, barbs, protrusions, cutouts, recesses, texturing, or the like. Fixation feature(s) may be disposed on helical thread(s) 308, between longitudinally adjacent helical threads 308, or otherwise on the outer surface of tapered header 114. Helical thread(s) 308 and / or fixation feature(s) may interface with the cardiac tissue to inhibit unintended movement and / or rotation of device 104 within the cardiac tissue. In some examples, helical thread(s) 308 and / or fixation features (s) may be angled and / or shaped to permit rotation of device 104 within the cardiac tissue in a first direction and inhibit rotation of device 104 within the cardiac tissue in a second, opposite direction.

[0050] Each helical thread 308 may extend radially outwards from an outer surface of tapered header 114 to define an outer thread edge. Helical thread(s) 308 (e.g., outer thread edge(s) of helical thread(s) 308) may promote interlock between cardiac tissue (e.g., around helical thread(s) 308) and helical thread(s) 308, e.g., to inhibit unintended movement and / or rotation of device 104 within the cardiac tissue. Helical thread(s) 308 may interlock with cardiac tissue (e.g., in a region around the outer thread edge(s) along less than one full wind, one full wind, or more than one full wind (e.g., more than two full winds) of helical thread(s) 308 around an outer perimeter of tapered header 308. Helical thread(s) 308 may depart from a helical form in one or more locations along helical thread(s) 308, e.g., to define fixation features (e.g., cutouts), second electrodes, or the like. Each outer thread edge may be continuous or discontinuous. In some examples, each outer thread edge may defines a roughened or textured edge.

[0051] Distal electrode 112 may be formed of an electrically conductive material, such as titanium, platinum, iridium, tantalum, stainless steel or alloys thereof. Distal electrode 112 may be coated with an electrically insulating coating, e.g., a parylene, polyurethane, silicone, epoxy, or other insulating coating, to reduce the electrically conductive active surface area of distal electrode 112, and thereby define a corresponding electrically activeAtty Ref. No. A0013522W001region. Defining the electrically active region of distal electrode 112 by covering portions of distal electrode 112 with an insulating coating may increase the electrical impedance of distal electrode 112 and thereby reduce the current delivered during a pacing pulse that captures the cardiac tissue. A lower current drain conserves power source 220, e.g., one or more rechargeable or non-rechargeable batteries, of device 104. In some examples, distal electrode 112 includes an electrically conducting material coating to define the electrically active region. For example, the electrically active region may be coated with titanium nitride (TiN).

[0052] The distal end of distal electrode 112 can pierce through one or more tissue layers to position the electrically active region within a desired tissue layer, e.g., the ventricular myocardium 108 or interventricular septum. The depth of the desired tissue layer may vary, e.g., based on the position of target implantation region 106 within heart 102. The clinician may rotate device 104 control the penetration of the cardiac tissue by distal electrode 112 and a depth of distal electrode 112 (e.g., of the electrically active region) within the cardiac tissue to place the electrically active region within the desired tissue layer. Distal electrode 112 may extend a distance from distal end 303 of housing 202 less than or equal to the expected pacing site depth and may have a relatively high compressive strength along its longitudinal axis, which may be substantially similar to or coincident with longitudinal axis 301, to resist bending in a lateral or radial direction when a longitudinal, axial, and / or rotational force is applied, e.g., to proximal end 305 of housing 202 to advance device 104 into the tissue at target implant region 106. By resisting bending in a lateral or radial direction, distal electrode 112 can maintain a spacing between a plurality of windings of distal electrode 112 when distal electrode 112 is a helix electrode. The spacing may be a pre-determined pitch of distal electrode 112 and may vary along a longitudinal length of distal electrode 112. Distal electrode 112 may be longitudinally non-compressible. Distal electrode 112 may also be elastically deformable in lateral or radial directions when subjected to lateral or radial forces, however, to allow temporary flexing, e.g., with tissue motion, but returns to its normally straight position when lateral forces diminish. In some examples, when distal electrode 112 is not exposed to any external force, or to only a force along its longitudinal axis (substantially similar toAty Ref. No. A0013522W001or coincident with longitudinal axis 301), distal electrode 112 retains a straight, linear configuration as shown.

[0053] All, substantially all, or a portion of housing 202 may function as an electrode 204, e.g., an anode, during pacing and / or sensing. In some examples, electrode 204 circumscribes a portion of housing 202 at or near proximal end 305. Electrode 204 can fully or partially circumscribe housing 202. FIG. 3 shows electrode 204 extending as a singular band around the outer perimeter of housing 202. Electrode 204 can also include multiple segments spaced a distance apart along a longitudinal axis 301 of housing 202 and / or around a perimeter of housing 202.

[0054] When housing 202 is formed from a conductive material, such as a titanium alloy, portions of housing 202 may be electrically insulated by a non-conductive material, such as a coating of parylene, polyurethane, silicone, epoxy or other biocompatible polymer, or other suitable material. For the portions of housing 202 without the non-conductive material, one or more discrete areas of housing 202 with conductive material can be exposed to define electrode 204.

[0055] When housing 202 is formed from a non-conductive material, such as a ceramic, glass or polymer material, an electrically-conductive coating or layer, such as a titanium, platinum, stainless steel, alloys thereof, a conductive material may be applied to one or more discrete areas of housing 202 to form electrode 204.

[0056] In some examples, electrode 204 is a component, such as a ring electrode, that is mounted or assembled onto housing 202. Electrode 204 may be electrically coupled to internal circuitry of device 104 via electrically-conductive housing 202 or an electrical conductor when housing 202 is a non-conductive material. In some examples, electrode 204 is located proximate to proximal end 305 of housing 202 and can be referred to as a proximal housing-based electrode. Electrode 204 can also be located at other positions along housing 202, e.g., located proximately to distal end 303 or at other positions along longitudinal axis 301. In some examples, electrode 204 is paired with distal electrode 112 for sensing ventricular signals and delivering pacing pulses (e.g., atrial pacing pulses, ventricular pacing pulses).

[0057] In some examples, in place of distal electrode 112, device 104 includes a fixation element (not shown) of similar shape and mechanical properties, but without an electrically active region or electrode formed thereon or borne thereby; in such examples,Aty Ref. No. A0013522W001the electrically active region can be positioned on a separate member and / or on the housing 202.

[0058] FIGS. 4 A and 4B are perspective diagrams illustrating example configurations of device 104. FIGS. 4A and 4B illustrate device 104 with tapered headers 402 and 420, respectively. Tapered headers 402, 420 are examples of tapered header 114.

[0059] As illustrated in FIGS. 4 A and 4B, device 104 may include helical electrode 406 extending distally from stylet 302. Helical electrode 406 may be an example of electrode 112. Helical electrode 406 may be an elongated body defining a helix. In some examples, a helix is an object having a three-dimensional shape like that of a wire wound uniformly in a single layer around a cylindrical or conical surface or mandrel such that the wire would be in a straight line if the surface were unrolled into a plane. Helical electrode 406 may extend from a distal end and / or distal opening of stylet 302 from a proximal end to a distal tip.

[0060] In some examples, helical electrode 406 includes one or more anti-rotation features. The anti-rotation features may facilitate fixation of helical electrode 406 to the tissue. The additional anti-rotation features may include a shape of helical electrode 406, dimensions (e.g., outer diameter, pitch, or the like) of helical electrode 406, one or more features disposed on an outer surface of helical electrode 406, or the like. The shape and / or dimensions of helical electrode 406 may include a geometric shape of helical electrode 406, a varying diameter configuration of helical electrode 406, a varying pitch configuration of helical electrode 406, a waveform configuration of helical electrode 406, or any combination herein. The one or more anti-rotation features disposed on helical electrode 406 may include, but are not limited to, elongated darts, barbs, or tines. The one or more anti -rotation features may resist rotation of helical electrode 406, e.g., by penetrating the tissue, by increasing the friction between helical electrode 406 and the tissue, or the like.

[0061] Helical electrode 406 may vary in size and shape in order to enhance tissue contact of the electrically active region. For example, helical electrode 406 may have a round cross-section or could be made with a flatter cross-section (e.g., oval or rectangular) based on tissue contact specifications.

[0062] The distal end of helical electrode 406 can have a conical, hemi-spherical, or slanted edge distal tip with a narrow tip diameter, e.g., less than 1 millimeter (mm), forAtly Ref. No. A0013522W001penetrating into and through tissue layers. The distal end can be a sharpened or angular tip or sharpened or beveled edges. In some examples, the diameter of helical electrode 406 varies from the proximal end to the distal tip of helical electrode 406. The varying diameter may cause helical electrode 406 to resist rotation within the tissue of heart 102.

[0063] The outer dimensions of helical electrode 406 can be substantially straight and cylindrical, with helical electrode 406 being rigid in some examples. Helical electrode 406 may have flexibility in lateral directions, being non-rigid to allow some flexing with heart motion. In a relaxed state, when not subjected to any external forces, helical electrode 406 can be configured to maintain a distance between the electrically active region and stylet 302, distal end 303, and / or distal end 304.

[0064] Tapered header 402 may include helical thread(s) 404 extending around an outer surface of tapered header 402. Helical thread(s) 404 may be an example of helical thread(s) 308, e.g., as illustrated in FIG. 3. Helical thread(s) 404 may extend around the outer perimeter of tapered header 402 and along a longitudinal length of tapered header 402 from proximal end 306 to distal end 304.

[0065] Helical thread(s) 404 of tapered header 402 may define a uniform depth. For example, as illustrated in FIG. 4A, the radially outward-most points of helical thread(s) 404 define reference axis 405. Reference axis 405 may extend distally towards longitudinal axis 301. Reference axis 405 may be parallel to an outer surface of tapered header 402.

[0066] Tapered header 420 may include helical thread(s) 422 extending around an outer surface of tapered header 420. Helical thread(s) 422 may be an example of helical thread(s) 308. Helical thread(s) 422 may extend around the outer perimeter of tapered header 420 and along a longitudinal length of tapered header 420 from proximal end 306 to distal end 304.

[0067] Helical thread(s) 422 may define a varying depth. For example, as illustrated in FIG. 4B, helical thread(s) 422 defining decreasing depths from proximal end 306 to distal end 304. In some examples, helical thread(s) 422 define thread depths that increase from proximal end 306 to distal end 304, that increase then decrease along the longitudinal length of tapered header 420, that decrease then increase along the longitudinal length of tapered header 420, or vary in any other way.Atly Ref. No. A0013522W001

[0068] The radially outward-most points of helical thread(s) 422 may define reference axis 424. Reference axis 424 may extend distally towards longitudinal axis 301. In some examples, as illustrated in FIG. 4B, reference axis 424 intersects with device 104 at or around distal end 304 of tapered header 420. In other examples, reference axis 424 may intersect with device 104 at or around electrode 406 or at a location along stylet 302 (e.g., between helical electrode 402 and distal end 304).

[0069] As illustrated in FIGS. 4 A and 4B, device 104 may define a shoulder 408 around the outer perimeter of housing 202 at or around proximal end 306. Tapered header 402 or 420 and / or housing 202 may define shoulder 408. Shoulder 408 may define a surface orthogonal to longitudinal axis 301. Shoulder 408 may define a width 410. Width 410 may correspond to a difference between an outer diameter of housing 202 and a maximum outer diameter of tapered header 402 or 420 (e.g., at or around proximal end 306 of tapered header 402 or 420). When the clinician implants tapered header 402 or 420 into tissue of the patient, shoulder 408 may contact a surface of the tissue to inhibit insertion of a portion of housing 202 into the tissue.

[0070] FIG. 5 is a perspective diagram illustrating another example configuration of device 104. FIG. 5 illustrates device 104 with tapered header 502 and helical electrode 406. Tapered header 502 is an example of tapered header 114.

[0071] Tapered header 502 may define helical thread(s) 506 extending around an outer perimeter of tapered header 502 from proximal end 306 to distal end 304. As illustrated in FIG. 5, tapered header 502 may define an outer diameter with a variable rate of change along longitudinal axis 301. For example, the outer diameter of tapered header 502 may change at a non-uniform rate from proximal end 306 to distal end 304. The outer surface of tapered header 502 may define reference line 508 from proximal end 306 to distal end 304, wherein reference line 506 indicates the outer diameters of tapered header 502 from proximal end 306 to distal end 304. The outer diameter for tapered header 502 may be measured from the outer surface of the tapered header 502 (e.g., ignoring helical thread(s) 506). Reference line 508 illustrates a varied (e.g., reducing) rate of change, wherein the rate of change of the outer diameter is greater around proximal end 306 than around distal end 304. By comparison, other examples of tapered header 114 (e.g., tapered header 402, 420) may illustrate a uniform rate of change from proximal end 306 to distal end 304. The varied rate of change may include, but is not limited to, a reducing rate of change, anAtly Ref. No. A0013522W001increasing rate of change (e.g., wherein the outer diameter reduces at a greater rate at or around distal end 304 than proximal end 306), or a combination of both.

[0072] FIGS. 6 A - 6C are perspective diagrams illustrating other example configurations of device 104. FIGS. 6A - 6C illustrate device 104 with tapered headers 602, 610, and 620, respectively. Tapered headers 602, 610, and 620 are examples of tapered header 114.

[0073] Tapered header 602 may define helical thread(s) 604 extending around an outer surface of tapered header 602. Tapered header 602 may be identical to tapered header 114 and helical thread(s) 604 may be identical to helical thread(s) 308, aside from the elements described below. Tapered header 602 may include cutout(s) 606 on helical thread(s) 308. Each of cutout(s) 606 may be cut into one of helical threads 308 (e.g., in an outer thread edge of helical thread 308) and may extend partially or entirely through the respective helical thread 308. In some examples, the outer thread edge of helical thread(s) 604 may depart radially inwards to form cutout(s) 606. Cutout(s) 606 may be equally distributed among a plurality of helical threads 308. Cutout(s) 606 may be equally distributed around a circumference of tapered header 602 and / or along a longitudinal length of tapered header 602. Cutout(s) 606 may define an angle configuration.

[0074] Cutout(s) 606 may be formed by two or more cuts into helical thread(s) 308. For example, as illustrated in FIG. 6, each of cutouts 606 may be formed by first cut 607A and second cut 607B. First cut 607 A may be made at a steeper angle towards a longitudinal center of tapered header 602 than second cut 607B or vice versa.. First cut 607A may form a first thread edge portion. The first thread edge portion may face towards a direction of revolution of helical thread(s) 308 (e.g., a screwing direction of helical thread(s) 308). Second cut 607B may form a second thread edge portion. The second thread edge portion may face a direction opposite to the direction of revolution of helical thread(s) 308 (e.g., an unscrewing direction of helical thread(s) 308). The first and second thread edge portions may interface with the cardiac tissue., e.g., to cause cutout(s) 606 to inhibit rotation of tapered header 602 out of tissue of the patient. Cutout(s) 606 may define uniform dimensions or may define variable dimensions. For example, cutouts 606 at or around proximal end 306 may define larger dimensions than cutouts 606 at or around distal end 304.Atty Ref. No. A0013522W001

[0075] Tapered header 610 may define helical thread(s) 612 extending around an outer surface of tapered header 610. Tapered header 610 may be identical to tapered header 114 and helical thread(s) 612 may be identical to helical thread(s) 308, aside from the elements described below. Tapered header 610 may include cutout(s) 614 on helical thread(s) 308. Each of cutouts 614 may be a curved cutout into one of helical threads 308 and may extend partially or entirely through the respective helical thread 308. Each of cutouts 614 may be formed from one or two or more separate cuts. Cutout(s) 614 may be equally distributed among a plurality of helical threads 308. Cutout(s) 614 may be equally distributed around a circumference of tapered header 610 and / or along a longitudinal length of tapered header 610.

[0076] Cutout(s) 606, 614 may allow for flow of patient tissue into cutout(s) 606, 614 as the clinician advances device 104 into the tissue. Surfaces of cutout(s) 606, 614 may interface with patient tissue within cutout(s) 606, 614 to inhibit unintended rotation of device 104 within the patient tissue.

[0077] Tapered header 620 may define helical thread(s) 622 extending around an outer surface of tapered header 620. Tapered header 620 may be identical to tapered header 114 and helical thread(s) 622 may be identical to helical thread(s) 308, aside from the elements described below. Tapered header 620 may include tine(s) 624. Tine(s) 624 may be disposed on an outer surface of tapered header 620 (e.g., between helical thread(s) 622) and / or on one or more surfaces of helical thread(s) 622. Tine(s) 624 may be equally distributed around the circumference of tapered header 620 and / or along the longitudinal length of tapered header 620. Each of tines 624 may extend radially away from tapered header 620 or may extend away from tapered header 620 in a direction opposite to a direction of revolution of helical thread(s) 622.

[0078] FIGS. 7A-7C are perspective diagrams illustrating example implantations of device 104 of any of FIGS. 1-6C within tissue of a patient. While FIGS. 7A - 7C primarily illustrate example implantation with respect to device 104 as illustrated in FIG.3, any device 104 described herein may be implanted in accordance with one or more of the techniques illustrated herein.

[0079] In some examples, as illustrated in FIG. 7A, only a portion of tapered header 114 penetrates surface 702 of patient tissue (e.g., ventricular myocardium 108 of heart 102). In such examples, the portion of tapered header 114 inserted within the patient tissueAtty Ref. No. A0013522W001may engage with the patient tissue around tapered header 114 (e.g., around helical thread(s) 308 of tapered header 114) to inhibit unintended rotation and / or movement of device 104 within the tissue (e.g., within ventricular myocardium 108).

[0080] In some examples, as illustrated in FIG. 7B, an entirety of tapered header 114 penetrates surface 702 into the patient tissue. In such examples, shoulder 408 at or around proximal end 306 of tapered header 114 (not pictured in FIG. 7B) may inhibit insertion of housing 202 into the patient tissue.

[0081] In some examples, as illustrated in FIG. 7C, tapered header 114 and at least a portion of housing 202 may penetrate surface 702 and into the patient tissue. The clinician may select a depth for electrode 112 of device 104 to enter into patient tissue (e.g., into ventricular myocardium 108) based at least in part on patient physiology, location of target implant region 106, and / or location of target tissue (e.g., LBB of heart 102). Based on the selected depth, the clinician may implant device 104 in accordance with one or more implanted positions as illustrated in FIGS. 7A-7C to position electrode 112 at the selected depth.

[0082] FIG. 8 is a flowchart illustrating an example process for sensing a cardiac electrical signal and delivering cardiac pacing therapy to a heart of a patient via an example device of any of FIGS. 1-7C. While FIG. 8 is primarily described with reference to implanting device 104 within heart 102 of a patient, the process may be used to implant another IMD within tissue of a patient at one or more other locations within the body of the patient.

[0083] A clinician may insert device 104 within a chamber of heart 102 (802). Device 104 may be retained within a medical device assembly. The clinician may control device 104 within the medical device assembly via a tether assembly coupled to delivery tool interface member 310 on device 104. The tether assembly may extend proximally out of the body of the patient.

[0084] Device 104 may be coupled to a tether assembly extending proximally out of the body of the patient. For example, device 104 may be coupled to a tether head of the tether assembly via delivery tool interface member 310. During implantation, the clinician may control the position and movement of device 104 via a tether handle of the tether assembly and may control the position and / or movement. As the clinician navigates the medical device assembly within the vasculature of the patient and into the chamber ofAtty Ref. No. A0013522W001heart 102, the clinician may manipulate the tether assembly to retain device 104 within the medical device assembly. For example, the clinician may apply a pulling force on the tether assembly while advancing the medical device assembly to retain device 104 within the medical device assembly. Retaining device 104 within the medical device assembly reduces a risk of unintended penetration of tissue by device 104 (e.g., by distal electrode 112) during navigation of device 104 into the chamber of heart 102.

[0085] Once device 104 is within the chamber of heart 102, the clinician may align (e.g., via the tether assembly) device 104 with target implantation region 106 within the chamber. The clinician may rotate device 104 to advance distal electrode 112 of device 104 to penetrate wall tissue of chamber of heart 102 (804). The clinician may then rotate and / or advance device 104 until distal electrode 112, stylet 302, and at least a portion of tapered header 114 penetrates the tissue at or around target implantation region 106.

[0086] The clinician may cause distal electrode 112 and / or stylet 302 to penetrate tissue by applying a pushing and / or rotary force on device 104. In some examples, where distal electrode 112 is helical electrode 406, the clinician may rotate device 104 about longitudinal axis 301 to cause a distal tip of helical electrode 406 to penetrate the patient tissue. The clinician may continue to advance device 104 into the patient tissue until distal end 306 of tapered header 114 contacts surface 702 of the tissue.

[0087] When distal end 306 of tapered header 114 contacts surface 702, the clinician may rotate device 104 about longitudinal axis 301 (e.g., via the tether assembly) to cause helical thread(s) 308 of tapered header 114 to penetrate surface 702 and engage with the tissue. As the clinician continues to rotate device 104, helical thread(s) 308 advance further into the tissue and causes tapered header 114 to advance further into the tissue. The clinician may rotate in a same direction to advance distal electrode 112 and tapered header 114 into the tissue.

[0088] The clinician may monitor a position of distal electrode 112 within the patient tissue and may adjust a depth of electrode 112 within the tissue to position electrode 112 at or around target tissue (e.g., at or around LBB of heart 102). The clinician may increase a depth of electrode 112 within the tissue by further advancing tapered header 114 and / or a portion of housing 202 into the tissue (e.g., as illustrated in FIG. 7C). The clinician may decrease a depth of electrode 112 within the tissue by retracting a portion of taperedAtty Ref. No. A0013522W001header 114 and / or a portion of housing 202 from within the tissue (e.g., as illustrated in FIG. 7 A).

[0089] The clinician may cause device 104 to deliver cardiac pacing signals from device 104 to the wall tissue via distal electrode (806). Depending on patient response and / or sensed signals from heart 102, the clinician may need to reposition device 104 within target implantation region 106. The clinician may iteratively adjust the implantation location within target implantation region 106 and / or an implantation depth of distal electrode 112 until the clinician determines that the patient response to cardiac pacing signals and / or sensed signals from heart 102 satisfy a threshold condition.

[0090] The clinician may then retract separate and retract the medical device assembly and / or the tether assembly from device 104. The clinician may de-couple the tether head of the tether assembly from device 104 (e.g., from delivery tool interface member 310 of device 104). Device 104 may then continue to deliver cardiac pacing signals to wall tissue of one or more chambers of heart 102, e.g., in accordance with the example techniques previously described herein. Helical thread(s) 308 on tapered head 114, fixation feature(s) on tapered head 114 (e.g., cutout(s) 606, 614, tine(s) 624), and / or other fixation feature(s) on device 104 may engage with the tissue around device 104 to inhibit unintended movement and / or rotation of device 104 within the tissue.

[0091] It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example, certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

[0092] In one or more examples, the described techniques may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored as one or more instructions or code on a computer-readable medium and executed by a hardware-based processing unit. Computer-readable mediaAtly Ref. No. A0013522W001may include non-transitory computer-readable media, which corresponds to a tangible medium such as data storage media (e.g., RAM, ROM, EEPROM, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer).

[0093] In addition, it should be noted that system described herein may not be limited to treatment of a human patient. In alternative examples, the system may be implemented in non-human patients, e.g., primates, canines, equines, pigs, and felines. These other animals may undergo clinical or research therapies that may benefit from the subject matter of this disclosure.

[0094] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0095] This disclosure describes each of the following examples.

[0096] Example 1: an implantable medical device (HMD) comprising: an elongated housing extending along a longitudinal axis from a proximal housing end to a distal housing end; a tapered header extending distally from the distal housing end, the tapered header defining one or more helical threads extending around an outer surface of the tapered header; and an electrode extending distally from a distal end of the tapered header, wherein the IMD is configured to be implanted within a chamber of a heart of a patient, and wherein the tapered header is configured to at least partially penetrate cardiac tissue of the chamber of the heart as the tapered header is rotated about the longitudinal axis to cause the one or more helical threads to engage with the cardiac tissue, and wherein the tapered header is configured to inhibit unintended rotation of the IMD within the cardiac tissue.

[0097] Example 2: the IMD of example 1, wherein the tapered header extends along the longitudinal axis from a proximal header end to a distal header end, and wherein the tapered header tapers from the proximal header end towards the distal header end.Atly Ref. No. A0013522W001

[0098] Example 3 : the IMD of example 2, wherein the tapered header defines a linear taper from the proximal header end towards the distal header end.

[0099] Example 4: the IMD of example 2, wherein a slope of the taper of the tapered header decreases from the proximal header end towards the distal header end.

[0100] Example 5: the IMD of any of examples 1-4, wherein one or more of the tapered header or the elongated housing defines a shoulder at or around the distal housing end of the housing, wherein the shoulder defines a step between an outer diameter of the elongated housing and an outer diameter of the outer surface of the tapered header, and wherein the shoulder is configured to inhibit insertion of the elongated housing into the cardiac tissue.

[0101] Example 6: the IMD of any of examples 1-4, wherein one or more of the tapered header or the elongated housing defines a shoulder at or around the distal housing end of the housing, wherein the shoulder defines a step between an outer diameter of the elongated housing and an outer diameter of the outer surface of the tapered header, and wherein the shoulder is configured to limit advancement of the electrode into the cardiac tissue.

[0102] Example 7: the IMD of any of examples 1-4, wherein a maximum outer diameter of the tapered header is less than or equal to an outer diameter of the elongated housing.

[0103] Example 8: the IMD of any of examples 1-7, wherein the one or more helical threads define a uniform pitch along the longitudinal axis.

[0104] Example 9: the IMD of any of examples 1-7, wherein the one or more helical threads define a variable pitch along the longitudinal axis.

[0105] Example 10: the IMD of any of examples 1-9, wherein the one or more helical threads define a uniform depth along the longitudinal axis.

[0106] Example 11 : the IMD of any of examples 1-10, wherein the one or more helical threads comprise an outer thread edge which is configured to promote interlock between the one or more threads and the cardiac tissue.

[0107] Example 12: the IMD of example 11, wherein the outer thread edge is configured to promote interlock in a region of the outer thread edge that extends along more than one full wind of the thread.Atly Ref. No. A0013522W001

[0108] Example 13: the IMD of example 12, wherein the outer thread edge is configured to promote interlock in a region of the outer thread edge that extends along more than two full winds of the thread.

[0109] Example 14: the IMD of any of examples 11-13, wherein the outer thread edge departs in the radial dimension from a helical form in one or more locations.

[0110] Example 15: the IMD of example 14, wherein the outer thread edge departs in the radial dimension from a helical form to form one or more cutouts.

[0111] Example 16: the IMD of example 15, wherein the one or more cutouts have an angled configuration.

[0112] Example 17: the IMD of example 16, wherein the one or more cutouts form a first thread edge portion that faces a screwing direction of the one or more threads and a second thread edge portion that faces an unscrewing direction of the one or more threads, and the second thread edge portion is orientated at a steeper angle than the first thread edge portion.

[0113] Example 18: the IMD of any of examples 11-13, wherein the outer thread edge is discontinuous.

[0114] Example 19: the IMD of any of examples 11-13, wherein the outer thread edge is roughened.

[0115] Example 20: the IMD of any of examples 1-19, wherein a maximum outer diameter of the one or more helical threads is less than or equal to an outer diameter of the elongated housing.

[0116] Example 21 : the IMD of any of examples 1-20, further comprising one or more cutouts on the one or more threads, each cutout of the one or more cutouts comprising: an angled cutout; or a curved cutout, wherein the one or more cutouts are configured to inhibit the unintended rotation of the IMD within the cardiac tissue.

[0117] Example 22: the IMD of any of examples 1-21, further comprising one or more tines or barbs disposed on one or more of: a surface of the one or more helical threads; or portions of the outer surface of the tapered header between the one or more helical threads, wherein the one or more tines are configured to inhibit the unintended rotation of the IMD within the cardiac tissue.

[0118] Example 23: the IMD of any of examples 1-22, wherein the tapered header is formed from an electrically insulating material.Atly Ref. No. A0013522W001

[0119] Example 24: the IMD of any of examples 1-23, wherein the electrode comprises one or more of: a button electrode; a helical electrode; or an elongated barb electrode.

[0120] Example 25: the IMD of any of examples 1-24, further defining a fixed distance along the longitudinal axis between the distal housing end of the elongated housing and the electrode, and wherein the IMD is configured to be adjustably positioned within the cardiac tissue to position the electrode at or around a target tissue within the heart.

[0121] Example 26: the IMD of example 25, wherein the target tissue comprises a Left Bundle Branch (LBB) of the heart.

[0122] Example 27: the IMD of any of examples 1-26, wherein the IMD comprises a transseptal device.

[0123] Example 28: a fixation device for an implantable medical device (IMD), the fixation device comprising: a tapered header extending distally from a distal housing end of the IMD, the tapered header defining: one or more helical threads extending around an outer surface of the tapered header, wherein the tapered header is configured to at least partially penetrate tissue of patient as the tapered header is rotated about a longitudinal axis to cause the one or more helical threads to engage with the tissue, and wherein the tapered header is configured to inhibit unintended rotation of the IMD relative to the tissue.

[0124] Example 29: the fixation device of example 28, wherein the tapered header extends along a longitudinal axis from a proximal header end to a distal header end, and wherein the tapered header tapers from the proximal header end towards the distal header end.

[0125] Example 30: the fixation device of example 29, wherein the tapered header defines a linear taper from the proximal header end towards the distal header end.

[0126] Example 31 : the fixation device of example 29, wherein a slope of the taper of the tapered header decreases from the proximal header end towards the distal header end.

[0127] Example 32: the fixation device of any of examples 28-31, wherein one or more of the tapered header or the elongated housing defines a shoulder at or around the distal housing end of the IMD, wherein the shoulder defines a step between an outerAtly Ref. No. A0013522W001diameter of the IMD and an outer diameter of the outer surface of the tapered header, and wherein the shoulder is configured to inhibit insertion of the IMD into the tissue.

[0128] Example 33: the fixation device of any of examples 28-32, wherein one or more of the tapered header or the elongated housing defines a shoulder at or around the distal housing end of the housing, wherein the should defines a step between an outer diameter of the elongated housing and an outer diameter of the outer surface of the tapered header, and wherein the shoulder is configured to limit advancement of the electrode into the tissue.

[0129] Example 34: the fixation device of any of examples 28-33, wherein a maximum outer diameter of the tapered header is less than or equal to an outer diameter of the elongated housing.

[0130] Example 35: the fixation device of any of examples 28-34, wherein the one or more helical threads define a uniform pitch along the longitudinal axis.

[0131] Example 36: the fixation device of any of examples 28-35, wherein the one or more helical threads define a variable pitch along the longitudinal axis.

[0132] Example 37: the fixation device of any of examples 28-36, wherein the one or more helical threads define a uniform depth along the longitudinal axis.

[0133] Example 38: the fixation device of any of examples 28-37, wherein the one or more helical threads comprise an outer thread edge which is configured to promote interlock between the one or more threads and the tissue.

[0134] Example 39: the fixation device of example 38, wherein the outer thread edge is configured to promote interlock in a region of the outer thread edge that extends along more than one full wind of the thread.

[0135] Example 40: the fixation device of example 39, wherein the outer thread edge is configured to promote interlock in a region of the outer thread edge that extends along more than two full winds of the thread.

[0136] Example 41 : the fixation device of any of examples 38-40, wherein the outer thread edge departs in the radial dimension from a helical form in one or more locations.

[0137] Example 42: the fixation device of example 41, wherein the outer thread edge departs in the radial dimension from a helical form to form one or more cutouts.

[0138] Example 43 : the fixation device of example 42, wherein the one or more cutouts have an angled configuration.Atly Ref. No. A0013522W001

[0139] Example 44: the fixation device of example 43, wherein the one or more cutouts form a first thread edge portion that faces a screwing direction of the one or more threads and a second thread edge portion that faces an unscrewing direction of the one or more threads, and the second thread edge portion is oriented at a steeper angle than the first thread edge portion.

[0140] Example 45: the fixation device of any of examples 38-40, wherein the outer thread edge is discontinuous.

[0141] Example 46: the fixation device of any of examples 38-40, wherein the outer thread edge is roughened.

[0142] Example 47: the fixation device of any of examples 28-46, wherein a maximum outer diameter of the one or more helical threads is less than or equal to an outer diameter of the elongated housing.

[0143] Example 48: the fixation device of any of examples 28-47, further comprising one or more cutouts on the one or more threads, each cutout of the one or more cutouts comprising: an angled cutout; or a curved cutout, wherein the one or more cutouts are configured to inhibit the unintended rotation of the IMD within the tissue.

[0144] Example 49: the fixation device of any of examples 28-48, further comprising one or more tines disposed on one or more of: a surface of the one or more helical threads; or portions of the outer surface of the tapered header between the one or more helical threads, wherein the one or more tines are configured to inhibit the unintended rotation of the IMD within the tissue.

[0145] Example 50: the fixation device of any of examples 28-49, wherein the tapered header is formed from an electrically insulating material.

[0146] Example 51: a method comprising: inserting an implantable medical device (IMD) within a chamber of a heart of a patient, the IMD comprising: an elongated housing extending along a longitudinal axis from a proximal housing end to a distal housing end; a tapered header extending distally from the distal housing end of the elongated housing, the tapered header defining one or more helical threads extending around an outer surface of the tapered header; and an electrode extending distally from a distal header end of the tapered header; advancing the tapered header at least partially into cardiac tissue of the chamber of the heart by rotating the tapered header about the longitudinal axis to cause the electrode and the one or more helical threads to engage with the cardiac tissue, whereinAtly Ref. No. A0013522W001the tapered header inhibits unintended rotation of the IMD within the cardiac tissue; and delivering, by the IMD and via the electrode, electrical stimulation signals to the cardiac tissue.

[0147] Example 52: the method of example 30, where the IMD further comprises one or more elements of any of examples 2-26.

[0148] Example 53: the method of any of examples 51-52, wherein the IMD defines a fixed distance along the longitudinal axis between the distal housing end of the elongated housing and the electrode, wherein advancing the tapered header at least partially into the cardiac tissue comprises: advancing the tapered header within the cardiac tissue by rotating the tapered header about the longitudinal axis to position the electrode at or around a target tissue within the heart, and wherein delivering the electrical stimulation signals to the cardiac tissue comprises delivering, by the IMD and via the electrode, the electrical stimulation signals to the target tissue.

[0149] Example 54: the method of example 53, wherein the target tissue comprises a Left Bundle Branch (LBB) of the heart.

[0150] Example 55: an implantable medical device (IMD) comprising: an elongated housing extending along a longitudinal axis from a proximal housing end to a distal housing end; a tapered header extending distally from the distal housing end; an electrode including an electrode shaft extending distally from a distal end of the tapered header; and the tapered header and / or the electrode shaft defining one or more helical threads extending around an outer surface of the tapered header and / or electrode shaft; wherein the IMD is configured to be implanted within a chamber of a heart of a patient, and wherein the one or more helical threads are configured to at least partially penetrate cardiac tissue of the chamber of the heart as the IMD is rotated about the longitudinal axis to cause the one or more helical threads to engage with the cardiac tissue, and wherein the tapered header and / or the electrode shaft is configured to inhibit unintended rotation of the IMD within the cardiac tissue.

[0151] Example 56: the IMD of example 55, further comprising one or more elements of any of examples 2-26.

[0152] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

Atly Ref. No. A0013522W001WHAT IS CLAIMED IS:

1. An implantable medical device (IMD) comprising:an elongated housing extending along a longitudinal axis from a proximal housing end to a distal housing end;a tapered header extending distally from the distal housing end, the tapered header defining one or more helical threads extending around an outer surface of the tapered header; andan electrode extending distally from a distal end of the tapered header, wherein the IMD is configured to be implanted within a chamber of a heart of a patient, and wherein the tapered header is configured to at least partially penetrate cardiac tissue of the chamber of the heart as the tapered header is rotated about the longitudinal axis to cause the one or more helical threads to engage with the cardiac tissue, and wherein the tapered header is configured to inhibit unintended rotation of the IMD within the cardiac tissue.

2. The IMD of claim 1, wherein the tapered header extends along the longitudinal axis from a proximal header end to a distal header end, and wherein the tapered header tapers from the proximal header end towards the distal header end.

3. The IMD of claim 2, wherein the tapered header defines a linear taper from the proximal header end towards the distal header end.

4. The IMD of claim 2, wherein a slope of the taper of the tapered header decreases from the proximal header end towards the distal header end.

5. The IMD of any of claims 1-4, wherein one or more of the tapered header or the elongated housing defines a shoulder at or around the distal housing end of the housing, wherein the shoulder defines a step between an outer diameter of the elongated housing and an outer diameter of the outer surface of the tapered header, and wherein the shoulder is configured to inhibit insertion of the elongated housing into the cardiac tissue.Atly Ref. No. A0013522W0016. The IMD of any of claims 1-4, wherein a maximum outer diameter of the tapered header is equal to an outer diameter of the elongated housing.

7. The IMD of any of claims 1-6, wherein the one or more helical threads define a uniform pitch along the longitudinal axis.

8. The IMD of any of claims 1-6, wherein the one or more helical threads define a variable pitch along the longitudinal axis.

9. The IMD of any of claims 1-8, wherein the one or more helical threads define a uniform depth along the longitudinal axis.

10. The IMD of any of claims 1-9, further comprising one or more cutouts on the one or more threads, each cutout of the one or more cutouts comprising:an angled cutout; ora curved cutout,wherein the one or more cutouts are configured to inhibit the unintended rotation of the IMD within the cardiac tissue.

11. The IMD of any of claims 1-10, further comprising one or more tines disposed on one or more of:a surface of the one or more helical threads; orportions of the outer surface of the tapered header between the one or more helical threads,wherein the one or more tines are configured to inhibit the unintended rotation of the IMD within the cardiac tissue.

12. The IMD of any of claims 1-11, wherein the tapered header is formed from an electrically insulating material.

13. The IMD of any of claims 1-12, wherein the electrode comprises one or more of:Atly Ref. No. A0013522W001a button electrode;a helical electrode; oran elongated barb electrode.

14. The IMD of any of claims 1-13, further defining a fixed distance along the longitudinal axis between the distal housing end of the elongated housing and the electrode, and wherein the IMD is configured to be adjustably positioned within the cardiac tissue to position the electrode at or around a target tissue within the heart.

15. The IMD of claim 14, wherein the target tissue comprises a Left Bundle Branch (LBB) of the heart.

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