Implantable lead

Abstract

An implantable lead is described herein that includes a lead body, a fixation helix, and a ring electrode. A proximal end of the lead body is configured to be connected to an implantable medical device. The fixation helix projects beyond a distal end of the lead body to penetrate tissue of a patient. The lead body includes a housing configured to burrow into the tissue of the patient with the fixation helix. The housing is mounted to the ring electrode and extends to the distal end of the lead body. The housing includes a housing helix along an outer surface of the housing, which defines a portion of an exterior surface of the implantable lead. The housing helix has first turns that circumferentially wrap around the housing. The first turns have a common rotational direction as second turns of the fixation helix.

Description

IMPLANTABLE LEADCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 730,714 (filed 11 -December-2024), the entire disclosure of which is incorporated herein by reference.TECHNICAL FIELD

[0002] Embodiments of the present disclosure relate generally to implantable leads, and more specifically to implantable leads of medical devices within a patient.BACKGROUND

[0003] Some implantable medical devices (IMDs) function to monitor cardiac activity of a patient, provide electrotherapy to the cardiac tissue, and / or the like. Some cardiac pacemakers and implantable cardioverter-defibrillators (ICD) use insulated wires called implantable leads, implantable cardiac leads, or simply leads to monitor the heart and provide stimulation therapy by delivering electrical pacing pulses and / or shocks. Some leads pierce the myocardial tissue of the heart to deliver stimulation therapy directly into the tissue. Conventional transvenous cardiac leads were designed for the distal tip of the lead to abut against the cardiac tissue. For example, conventional leads may have a distal fixation element that extends from the distal end of the lead body and penetrates the tissue to secure the lead at the target implant location. In these conventional leads, no other portions of the lead burrow through, i.e., penetrate into, the tissue besides the fixation element. For example, some conventional leads have impeding features located just proximal to the distal fixation element and designed to hinder burrowing into the cardiac tissue.

[0004] Conduction system pacing (CSP) is a technique of cardiac pacing that involves implanting pacing leads into the interventricular septum between the15907W001 (013-0627PCT) 1 PATENTleft and right ventricles to reach the left ventricular nerve bundle (LBB). Pacing lead delivery for CSP systems, such as left bundle branch area (LBBA) implantation, may involve the distal end of the lead to be inserted a depth of around 1 cm into the septal wall, which may be greater than the protruding length of the distal fixation element.

[0005] There is a general need for an implantable lead designed for the distal end of the lead body to burrow into patient tissue, not just a distal fixation element that projects from the lead body. It is a particular need for an implantable lead that can be reliably used for CSP applications.SUMMARY

[0006] In accordance with embodiments herein, an implantable lead is provided that includes a lead body, a fixation helix, and a ring electrode. The lead body extends from a proximal end of the lead body to a distal end of the lead body. The proximal end is configured to be connected to an implantable medical device. The lead body defines a lumen therethrough. The fixation helix projects or is selectively extendable to project beyond the distal end of the lead body to penetrate tissue of a patient. The lead body includes a housing that is configured to burrow into the tissue of the patient with the fixation helix. The housing is mounted to the ring electrode and extends to the distal end of the lead body. An outer surface of the housing defines a portion of an exterior surface of the implantable lead. The housing includes a housing helix along the outer surface of the housing. The housing helix has first turns that circumferentially wrap around the housing along at least a portion of the housing. The first turns have a common rotational direction as second turns of the fixation helix.

[0007] Optionally, a first pitch between the first turns of the housing helix matches a second pitch between the second turns of the fixation helix.

[0008] Optionally, the housing helix may be defined by a recessed helical groove along the outer surface of the housing.15907W001 (013-0627PCT) 2 PATENT

[0009] Optionally, the housing helix may be defined by a continuous helical ridge that protrudes radially outward from the outer surface of the housing.

[0010] Optionally, the housing helix may include multiple stepped cutout recesses along a helical path of the housing helix.

[0011] Optionally, the stepped cutout recesses may include shoulder surfaces that resist rotation of the housing in a direction opposite the rotational direction of the housing helix.

[0012] Optionally, the housing helix may be defined by a discontinuous helical ridge that protrudes radially outward from the outer surface of the housing. The discontinuous helical ridge may be composed of multiple fins, with each of the fins tapering towards the distal end of the lead body to define a respective lead-in surface.

[0013] Optionally, the housing tapers towards the distal end of the lead body to provide a lead-in surface into the tissue of the patient.

[0014] Optionally, a distal face of the housing may be smooth (or smoother than one or more, or all, other surfaces of the housing). A distal edge of the housing at an intersection between the outer surface and the distal face may be curved to provide a lead-in surface into the tissue of the patient.

[0015] Optionally, the housing may be an electrically insulative and monolithic tubular member that extends from an exposed portion of the ring electrode to the distal end of the lead body.

[0016] Optionally, a proximal region of the housing may surround and mount to a distal portion of the ring electrode. The distal portion of the ring electrode may include at least one hole or depression along an outer surface of the ring electrode. The proximal region of the housing includes at least one locking protrusion that15907W001 (013-0627PCT) 3 PATENTprojects radially inward from an inner surface of the housing and is received within the at least one hole or depression in the distal portion of the ring electrode.

[0017] Optionally, a proximal region of the housing surrounds and mounts to a distal portion of the ring electrode. An inner surface of the housing may include a shoulder that abuts against and is bonded to a distal face of the distal portion of the ring electrode.

[0018] Optionally, the housing includes an annular ridge protruding radially outward from the outer surface of the housing. A distance from the annular ridge to the distal end of the lead body may be between 5 mm and 15 mm.

[0019] Optionally, the housing may include multiple tines that protrude radially outward beyond the outer surface of the housing and are circumferentially spaced apart around the housing. A distance from the tines to the distal end of the lead body may be between 5 mm and 15 mm.

[0020] Optionally, the housing may include multiple protrusions that are circumferentially spaced apart along the housing and located at a distal region of the housing proximate to the distal end of the lead body.

[0021] Optionally, the protrusions may include tines that project from the outer surface of the housing at different respective angles. The respective angles of the tines correspond to the rotational direction of the housing helix.

[0022] Optionally, the housing may include multiple annular ridges that protrude radially outward from the outer surface of the housing at the distal end of the lead body.

[0023] Optionally, the fixation helix may be selectively extendable relative to the housing between a retracted state and an extended state. The housing may be rotationally fixed to the fixation helix when the fixation helix is in the extended15907W001 (013-0627PCT) 4 PATENTstate so that the housing rotates with the fixation helix to penetrate the tissue of the patient.

[0024] In accordance with embodiments herein, an implantable lead is provided that includes a lead body, a fixation helix, and a ring electrode. The lead body extends from a proximal end of the lead body to a distal end of the lead body. The proximal end is configured to be connected to an implantable medical device. The lead body defines a lumen therethrough. The fixation helix projects or is selectively extendable to project beyond the distal end of the lead body to penetrate tissue of a patient. The lead body includes an electrically insulative and monolithic tubular housing that is configured to burrow into the tissue of the patient with the fixation helix. A proximal region of the tubular housing surrounds and mounts to a distal portion of the ring electrode and the tubular housing extends to the distal end of the lead body. An outer surface of the tubular housing defines a portion of an exterior surface of the implantable lead. The tubular housing includes a housing helix along the outer surface thereof.

[0025] Optionally, the housing helix includes first turns that circumferentially wrap around the tubular housing along at least a portion of the tubular housing. The first turns of the housing helix have a common rotational direction as second turns of the fixation helix.

[0026] Optionally, a first pitch between the first turns of the housing helix may match a second pitch between the second turns of the fixation helix.

[0027] Optionally, the housing helix may include multiple stepped cutout recesses along a helical path of the housing helix. The stepped cutout recesses include shoulder surfaces that resist rotation of the housing in a direction opposite the rotational direction of the housing helix.

[0028] Optionally, the distal portion of the ring electrode includes at least one hole or depression along an outer surface of the ring electrode. The proximal region of the tubular housing may include at least one locking protrusion that15907W001 (013-0627PCT) 5 PATENTprojects radially inward from an inner surface of the tubular housing and is received within the at least one hole or depression in the distal portion of the ring electrode.

[0029] Optionally, an inner surface of the tubular housing may include a shoulder that abuts against and is bonded to a distal face of the distal portion of the ring electrode.

[0030] Optionally, the housing helix may be defined by a discontinuous helical ridge that protrudes radially outward from the outer surface of the tubular housing. The discontinuous helical ridge may be composed of multiple fins that each taper towards the distal end of the lead body.

[0031] Optionally, the housing helix may be defined by one of (i) a continuous helical ridge that protrudes radially outward from the outer surface of the tubular housing or (ii) a recessed helical groove along the outer surface of the tubular housing.

[0032] Optionally, the tubular housing may taper towards the distal end of the lead body to provide a lead-in surface into the tissue of the patient.

[0033] Optionally, a distal face of the tubular housing may be smooth. A distal edge of the housing at an intersection between the outer surface and the distal face may be curved to provide a lead-in surface into the tissue of the patient.

[0034] Optionally, the housing may include an annular ridge protruding radially outward from the outer surface of the housing. A distance from the annular ridge to the distal end of the lead body may be between 5 mm and 15 mm.

[0035] Optionally, the housing may include multiple tines that protrude radially outward beyond the outer surface of the housing and are circumferentially spaced apart around the housing. A distance from the tines to the distal end of the lead body may be between 5 mm and 15 mm.15907W001 (013-0627PCT) 6 PATENT

[0036] Optionally, the fixation helix may be selectively extendable relative to the tubular housing between a retracted state and an extended state. The tubular housing may be rotationally fixed to the fixation helix when the fixation helix is in the extended state so that the tubular housing rotates with the fixation helix to penetrate the tissue of the patient.BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 illustrates a schematic cutaway view of a heart relative to an implantable system comprising an IMD and an implantable lead.

[0038] Figure 2 is another schematic cutaway view of the heart showing a location of the bundle of His (e.g., His bundle) in the heart.

[0039] Figure 3 illustrates an implantable lead according to an embodiment.

[0040] Figure 4 illustrates a side view of the implantable lead showing a distal segment of the implantable lead according to an embodiment.

[0041] Figure 5 is a side cross-sectional view of a housing of the implantable lead according to an embodiment.

[0042] Figure 6 is a perspective view of the housing shown in Figure 5.

[0043] Figure 7 is an enlarged view of a portion of the housing shown inFigure 6.

[0044] Figure 8 is a perspective view of the distal segment of the implantable lead including a housing according to another embodiment.

[0045] Figure 9 is a perspective view of the distal segment of the implantable lead including a housing according to a further embodiment.

[0046] Figure 10 is a perspective view of a portion of the implantable lead showing a set of tines as depth control features according to an embodiment.15907W001 (013-0627PCT) 7 PATENT

[0047] Figure 11 is a perspective view of a distal portion of the housing according to an embodiment.

[0048] Figure 12 is a perspective view of the distal portion of the housing according to another embodiment.

[0049] Figure 13 is a perspective view of the distal portion of the housing according to a further embodiment.

[0050] Figure 14 is a flow chart of a method of assembling a lead of an IMD according to an embodiment.

[0051] Figure 15 illustrates a block diagram of an exemplary IMD that may be connected to the implantable lead in accordance with one or more embodiments herein.DETAILED DESCRIPTION

[0052] It will be readily understood that the components of the embodiments as generally described and illustrated in the figures herein may be arranged and designed in a wide variety of different configurations in addition to the described example embodiments. Thus, the following more detailed description of the example embodiments, as represented in the figures, is not intended to limit the scope of the embodiments, as claimed, but is merely representative of example embodiments.

[0053] Reference throughout this specification to “one embodiment” or “an embodiment” (or the like) means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” or the like in various places throughout this specification are not necessarily all referring to the same embodiment.15907W001 (013-0627PCT) 8 PATENT

[0054] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments. One skilled in the relevant art will recognize, however, that the various embodiments can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obfuscation. The following description is intended only by way of example, and simply illustrates certain example embodiments.

[0055] Embodiments may be implemented in connection with one or more implantable medical devices (IMDs). Non-limiting examples of IMDs include neurostimulator devices, implantable leadless monitoring and / or therapy devices, and / or alternative implantable medical devices. For example, the IMD may represent a cardiac monitoring device, pacemaker, cardioverter, cardiac rhythm management device, defibrillator, neurostimulator, leadless monitoring device, leadless pacemaker and the like. For example, the IMD may include one or more structural and / or functional aspects of the device(s) described in U.S. Patent 9,333,351 “Neurostimulation Method And System To Treat Apnea” and U.S. Patent 9,044,610 “System And Methods For Providing A Distributed Virtual Stimulation Cathode For Use With An Implantable Neurostimulation System”, which are hereby incorporated by reference.

[0056] All references cited herein, including publications, patent applications, and patents, are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein.

[0057] Embodiments set forth herein describe implantable leads that are designed to burrow or penetrate into cardiac tissue for delivering electrical stimulation therapy. In an example, the embodiments may address the challenges of using implantable leads, such as cardiac leads, for CSP applications. The15907W001 (013-0627PCT) 9 PATENTimplantable leads described herein may be implanted relatively deep into the interventricular septal wall between the right and left ventricles to reach the LBB. The implantable leads described herein include a lead body that has a distal region configured to burrow into the cardiac tissue with a fixation element, such as a helical fixation element, also referred to as fixation helix. The implantable leads include features for easing lead insertion and reducing the applied torque needed to burrow the distal region of the implantable lead into the patient tissue. These features may protect lead component integrity. The implantable leads described herein may provide increased control of burrowing or penetration depth to mitigate the risk of perforating the back side of the septal wall. Furthermore, the implantable leads described herein may provide improved tissue engagement and fixation at the implant site to retain the implantable lead at the target location. These fixation features may be designed to reduce the risk of dislodgement and loss of pacing effectiveness due to lead migration.

[0058] Figure 1 illustrates a schematic cutaway view of a heart 10 relative to an implantable system 50. The heart 10 includes a right atrium RA, a right ventricle RV, a left atrium LA, and a left ventricle LV. During normal operation of the heart 10, deoxygenated blood from the body is returned to the right atrium RA from the superior vena cava 12 and inferior vena cava 14. The right atrium RA pumps the blood through the atrioventricular or tricuspid valve 16 to the right ventricle RV, which then pumps the blood through the pulmonary valve 18 and the pulmonary artery 20 to the lungs for reoxygenation and removal of carbon dioxide. The newly oxygenated blood from the lungs is transported to the left atrium LA, which pumps the blood through the mitral valve 22 to the left ventricle LV. The left ventricle LV pumps the blood through the aortic valve 24 and the aorta 26 throughout the body.

[0059] Figure 2 is another schematic cutaway view of the heart 10 showing a location of the bundle of His 30, also referred to as His bundle, in the heart 10. The His bundle 30 consists of fast-conducting muscle fibers that begin at the15907W001 (013-0627PCT) 10 PATENTatrioventricular node in the right atrium and pass to the interventricular septum 32, also referred to as septal wall, between the left and right ventricles. The His bundle 30 divides in the interventricular septum 32 into a right branch and a pair of left branches. The right branch travels along the right side of the interventricular septum 32 and supplies excitation to the right ventricle. The pair of left branches travel along the left side of the interventricular septum 32 and supply excitation to the left ventricle. The fibers in the branches terminate in an extensive network of Purkinje fibers which distribute excitation pulses to the layer of cells beneath the endocardium. The His bundle 30 serves as an initial pathway for electrical impulses to travel from the atria to the ventricles. For example, the His bundle 30 transmits electrical signals from the atrioventricular (AV) node to the right and left bundle branches. The left bundle branch (LBB) is one of the two bundle branches of the His bundle 30, traveling along the left side of the interventricular septum 32. The LBB carries electrical impulses to the left ventricle, facilitating synchronized contraction of the left ventricle.

[0060] Returning to Figure 1 , the implantable system 50 includes an IMD 52, such as in the form of a pulse generator device, which is operably coupled to an implantable lead 54 through a lead adaptor 56. The lead adaptor 56 is configured to receive a lead connector (not shown) of the implantable lead 54. Although the implantable system 50 includes only one implantable lead in Figure 1 , the implantable system 50 may include multiple implantable leads in other embodiments. In an embodiment, the implantable lead 54 is a so-called implantable cardiac lead designed to penetrate the cardiac tissue of the heart 10. In an example, the implantable lead 54 may be positioned and advanced to penetrate the endocardium of the septal wall 32 to reach the LBB of the His bundle 30. The implantable lead 54 may be a transvenous lead that enters the vascular system through one of several possible vascular access sites. For example, the implantable lead 54 may extend through the superior vena cava 12 to the right atrium RA.15907W001 (013-0627PCT) 11 PATENT

[0061] In Figure 1 , the IMD 52 is a cardiac pacemaker. In other embodiments, however, the IMD 52 may be an intracardiac defibrillator (ICD), a cardiac resynchronization therapy defibrillator (CRT-D), or the implantable system 50 may include an ICD coupled with a pacemaker, and the like. The IMD 52 may be a dual-chamber stimulation device capable of treating both fast and slow arrhythmias with stimulation therapy, including cardioversion, defibrillation, and pacing stimulation, as well as being capable of detecting heart failure, evaluating its severity, tracking the progression thereof, and controlling the delivery of therapy and warnings in response thereto. The IMD 52 may be controlled to sense atrial and ventricular waveforms of interest, discriminate between two or more ventricular waveforms of interest, deliver stimulus pulses or shocks, and inhibit application of a stimulation pulse to a heart based on the discrimination between the waveforms of interest and the like. The IMD 52 may provide pacing stimulation to the LBB via the implantable lead 54.

[0062] Although not shown, the IMD 52 may wirelessly communicate with an external device, such as a programmer. The external device may be used by a physician or other technician to select and / or modify therapy parameters to be implemented by the IMD 52.

[0063] Figure 3 illustrates an implantable lead 100 according to an embodiment. The implantable lead 100 may be the implantable lead 54 shown in Figure 1. The implantable lead 100 extends from a proximal end 102 to a distal end 104. The implantable lead 100 includes a fixation helix 106 at the distal end 104. In an embodiment, the implantable lead 100 includes a terminal connection segment 108 at the proximal end 102. The implantable lead 100 includes a lead body 110 between the proximal end 102 and the distal end 104, such as between the terminal connection segment 108 and the fixation helix 106. The lead body 110 extends from a proximal end 112 of the lead body 102 to a distal end 114 of the lead body 102.15907W001 (013-0627PCT) 12 PATENT

[0064] The fixation helix 106 projects beyond the distal end 114 of the lead body 102. The fixation helix 106 may be a corkscrew designed to be screwed into cardiac tissue. The fixation helix 106 may be composed of a metallic material. A rotational torque applied to the implantable lead 100 may drive the fixation helix 106 into the cardiac tissue, such as the septal wall 32, to engage and anchor the implantable lead 100 to the tissue. In a first example, the fixation helix 106 is fixed in place relative to the lead body 102. For example, the fixation helix 106 permanently projects beyond the distal end 114. In a second example, the fixation helix 106 may be selectively extendable, relative to one or more ring electrodes 120 of the lead body 110, between a retracted position and an extended position. The fixation helix 106 projects beyond the distal end 114 of the lead body 110 in the extended position. In the retracted position, the fixation helix 106 may be nested within a lumen of the lead body 110, without projecting beyond the distal end 114. The fixation helix 106 may be driven into the cardiac tissue when in the extended position.

[0065] The implantable lead 100 includes multiple electrodes for delivering electrical stimulation to the cardiac tissue of the patient. For example, the implantable lead 100 may include a defibrillation (e.g., shock) coil 116, a tip electrode 118, and one or more ring electrodes 120. The electrodes may be spaced apart along the length of the implantable lead 100. In an example, the fixation helix 106 defines the tip electrode 118. The ring electrode(s) 120 may be disposed between the defibrillation coil 116 and the tip electrode 118. The implantable lead 100 has two ring electrodes 120 in the illustrated example, but may have only one or more than two ring electrodes 120 in other example embodiments. In an embodiment, the implantable lead 100 comprises at least one ring electrode 120 and the tip electrode 118 and / or the defibrillation coil 116. In another embodiment, the implantable lead 100 comprises multiple ring electrodes 120, and optionally the tip electrode 118 and / or the defibrillation coil 116.15907W001 (013-0627PCT) 13 PATENT

[0066] The terminal connection segment 108 is designed to be received in a receptacle or lead adaptor 56 of the IMD 52, such a pulse generator device 52 (shown in Figure 1 ). The terminal connection segment 108 may have an IS1 / DF1 configuration, IS4 / DF4 configuration, or another configuration. The terminal connection segment 108 may include electrically conductive contacts 122 and electrically insulating portions 124 that alternate with the electrically conductive contacts 122 in a row. The electrically conductive contacts 122 may be ring contacts, pin contacts, and / or the like.

[0067] The implantable lead 100 includes electrical conductors that extend through the lead body 110 from the electrodes 116, 118, 120 to corresponding electrically conductive contacts 122 of the terminal connection segment 108. The electrical conductors may be helical coils, multi-filar conductors, and / or the like. Pacing pulses from the IMD 52, such as the pulse generator device 52, may be conveyed through one or more of the electrical conductors to at least one of the ring and tip electrodes 118, 120 for delivery to the cardiac tissue. Defibrillation shocks from the IMD 52, such as the pulse generator device 52, may be conveyed through one or more of the electrical conductors to the shock coil 116 to shock the cardiac tissue.

[0068] The implantable lead 100 is designed to allow a distal segment 130 of the implantable lead 100 to burrow or penetrate into patient tissue, such as heart tissue. The distal segment 130 may extend from the distal-most ring electrode 120 to the distal end 104 of the implantable lead 100. For example, the distal segment 130 includes the fixation helix 106 as well as a length (e.g., at least a portion) of the lead body 110 from the distal-most ring electrode 120 to the distal end 114 of the lead body 110. It may be desirable to burrow the distal segment 130 into the patient tissue to reach relatively deep areas for CSP applications. For example, the LBB may be located around 1 cm or more into the interventricular septal wall 32 (from the right ventricle). It may be difficult to reliably and accurately reach the LBB for CSP applications using known implantable leads. Known implantable15907W001 (013-0627PCT) 14 PATENTleads are not designed to burrow any portion of the lead body into the patient tissue. Rather, the known implantable leads are designed to permit only a tip electrode and / or fixation element, such as a fixation helix, to penetrate the patient tissue. The known implantable leads use the distal end of the lead body as a hard stop surface that abuts against the patient tissue without penetrating the tissue. For example, some known implantable leads have annular ridges, flanges, or other widening features at the distal end of the lead body, which are designed to prohibit the lead body from burrowing into the patient tissue. It may be difficult to provide accurate and reliable pacing and / or sensing of the LBB when only the tip electrode, such as a fixation helix, penetrates the septal wall.

[0069] In an example, the distal segment 130 of the implantable lead 100 described herein may be designed to ease insertion into the patient tissue, without snagging on the tissue or applying a large puncture force. The distal segment 130 may be designed to limit burrowing friction when penetrating the tissue, so that the applied torque on the implantable lead 100 is also limited. In an example, the distal segment 130 of the implantable lead 100 may be rotatable as one unit, so that the fixation helix 106 and the lead body 110 are rotationally fixed together and rotate together to burrow into the tissue. The components of the distal segment 130 may have torsional strength to withstand the torque and friction exerted on the distal segment 130 during the tissue burrowing procedure, without damaging the components. In an example, the implantable lead 100 may include one or more features that provide depth control to prohibit the distal segment 130 from burrowing too far into the patient tissue. For example, the implantable lead 100 may have one or more depth control features that reduce the risk of the fixation helix 106 perforating the full thickness of the septal wall 32 and protruding into the left ventricle. In an example, the implantable lead 100 may include one or more features to enhance fixation and retention of the distal segment 130 at the target implant location in the patient tissue. These lead fixation feature(s) may reduce the risk of lead migration over time and / or may resist pull-out forces on the implantable15907W001 (013-0627PCT) 15 PATENTlead 100 that pull the implantable lead 100 in a backward direction out of the patient tissue.

[0070] Figure 4 illustrates a side view of the implantable lead 100 showing the distal segment 130 according to an embodiment. The implantable lead 100 includes a housing 140 along the distal segment 130. The housing 140 may be a portion of the lead body 110. The housing 140 may be an outer layer of the implantable lead 100. For example, an outer surface 146 of the housing 140 may define at least a portion of an exterior surface of the implantable lead 100, which is exposed to the surrounding environment. The housing 140 may have a tubular (e.g., cylindrical) shape. The housing 140 surrounds internal components of the implantable lead 100. For example, the housing 140 defines a lumen 142 therethrough. The fixation helix 106 may extend through the lumen 142. The housing 140 may extend from the distal-most ring electrode 120 to the distal end 114 of the lead body 110. For example, a distal face 144 of the housing 140 may define the distal end 114 of the lead body 110. The housing 140 is shown in phantom in Figure 4 to visualize the internal components within the lumen 142. The distal segment 130 of the implantable lead 100 may be referred to as a distal header assembly. For example, the housing 140 may be referred to as a header or tubular header.

[0071] In an example, the fixation helix 106 is selectively extendable relative to the housing 140 between a retracted state and an extended state. The fixation helix 106 is shown in the extended state in Figure 4. In the extended state, the fixation helix 106 projects beyond the distal end 114 of the lead body 110 (e.g., the distal face 144 of the housing 140). In the retracted state, the fixation helix 106 may be nested within the lumen 142 without projecting beyond the distal end 114 of the lead body 110 (e.g., the distal face 144). In an example, the fixation helix 106 may be set to the retracted state while the implantable lead 100 navigates through the transvenous system of the patient into the heart. Upon approaching a target implant site, such as the interventricular septal wall 32, the fixation helix 10615907W001 (013-0627PCT) 16 PATENTmay be transitioned to the extended state. The fixation helix 106 may be set to the extended state for penetrating the patient tissue, for example burrowing into the septal wall 32. The fixation helix 106 may be rotated to screw the corkscrew fixation helix 106 into the tissue.

[0072] In an example, the housing 140 may be rotationally fixed to the fixation helix 106, at least when the fixation helix 106 is in the extended state. The housing 140 and the fixation helix 106 may rotate together, without relative rotational movement, when in the extended state. As such, rotation of the fixation helix 106 in the extended state may cause the housing 140 to rotate in the same direction. In an example, when the fixation helix 106 is in the retracted position, the fixation helix 106 may be rotatable relative to the housing 140. The fixation helix 106 may be extended from the retracted position to the extended position by rotating the fixation helix 106 in a first rotational direction relative to the ring electrode 120 and the housing 140. The fixation helix 106 may be part of an inner subassembly, which is rotatable relative to an outer subassembly of the lead, as described in U.S. Patent Publication No. 2024 / 0189601 , entitled Implantable Lead Having Variable Electrode Spacing, which is incorporated by reference herein in its entirety. Once the fixation helix 106 reaches the extended position, the fixation helix 106 may rotationally lock to the housing 140 so that additional torque applied to the fixation helix 106 in the first rotational direction may also be exerted on the housing 140. Thus, continued torque application in the first rotational direction may cause the housing 140 and fixation helix 106 to rotate together in the first rotational direction.

[0073] In an example, torque applied to the fixation helix 106 in a second rotational direction, which is opposite the first rotational direction, may cause the fixation helix 106 to rotate relative to the housing 140 and retract into the lumen 140 of the housing 140. The fixation helix 106 may retract until reaching a fully retracted position. In an example, after reaching the fully retracted position, continued torque applied in the second rotational direction may cause the housing15907W001 (013-0627PCT) 17 PATENT140 and the fixation helix 106 to rotate together in the second rotational direction. The combined rotation in the second direction may assist with removing the distal segment 130 of the implantable lead 100 from the patient tissue.

[0074] The housing 140 mounts to the distal-most ring electrode 120. For example, the ring electrode 120 may have a stepped outer surface, which includes a distal ring portion 148 and an exposed portion 150. The exposed portion 150 is proximal to the distal ring portion 148. Optionally, the ring electrode 120 may include a proximal ring portion 152, with the exposed portion 150 arranged between the distal ring portion 148 and the proximal ring portion 152. The distal ring portion 148 may have a smaller outer diameter than the exposed portion 150. In an example, the housing 140 may overlap and surround the distal ring portion 148, so that the distal ring portion 148 is received within the lumen 142 of the housing 140. In an example, the housing 140 does not cover the exposed portion 150 of the ring electrode 120. The exposed portion 150 may be exposed to the external environment, and may function as an electrode surface for delivering pacing pulses and / or sensing electrical signals.

[0075] The ring electrode 120 may be secured to the housing 140 via the distal ring portion 148. For example, a proximal region 161 of the housing 140 may surround and mount to the distal ring portion 148 of the ring electrode 120. The proximal region 161 of the housing 140 may be bonded to the distal ring portion 148 via a medical grade adhesive as an illustrative, but non-limiting, example. Further examples are described below with reference to Figures 4 and 5.

[0076] Figure 5 is a side cross-sectional view of the housing 140 of the implantable lead 100 according to an embodiment. The housing 140 in Figure 5 may represent the phantom housing 140 in Figure 4. The housing 140 in Figure 5 may be an electrically insulative and monolithic tubular member 153 (e.g., body) that seamlessly extends from a proximal face 154 of the housing 140 to the distal face 144. The tubular member 153 may be a sleeve. In an example, the tubular member 153 is composed of silicone. When assembled on the implantable lead15907W001 (013-0627PCT) 18 PATENT100, the tubular member 153 continuously extends from the ring electrode 120, such as from and edge of the exposed portion 150 of the ring electrode 120 to the distal end 114 of the lead body 110.

[0077] The housing 140 has one or more features to ease the insertion of the distal segment 130 of the implantable lead 100 into the patient tissue, such as the septal wall 32. The distal region of the housing 140 may be designed to prohibit snagging on the tissue and / or avoid requiring a large force to penetrate the tissue. In an example, the housing 140 tapers towards the distal face 144. The distal face 144 may define the distal end 114 (shown in Figure 4) of the lead body 110. The outer diameter of the housing 140 may decrease with increasing proximity to the distal face 144. In other words, the outer diameter of the housing 140 increases when traveling from the distal face 144 towards the proximal face 154 along this distal region of the housing 140. This means that the distal region of the housing 140 may be in the form of a tapered segment. The tapered segment of the housing 140 may provide a lead-in surface 155 into the tissue of the patient. The lead-in surface 155 alleviates an abruptness of the transition between the fixation helix 106 and the housing 140. In an example, the distal face 144 of the housing 140 is smooth to reduce the risk of snagging and / or reduce friction as the housing 140 is pressed against the patient tissue. Furthermore, a distal edge 156 of the housing 140 may be curved. The distal edge 156 is at an intersection between the outer surface 146 of the housing 140 and the distal face 144. The curved distal edge 156 may represent a portion of the lead-in surface 155.

[0078] In an example, the housing 140 may be designed to rotationally lock to the ring electrode 120. With additional reference to Figure 4, the distal ring portion 148 of the ring electrode 120 may include at least one hole or depression 160 along an outer surface 162 of the distal ring portion 148 of the ring electrode 120. As shown in Figure 5, the proximal region 161 of the housing 140 includes at least one locking protrusion 164 that projects radially inward from an inner surface 166 of the housing 140. The inner surface 166 faces and defines the lumen 142.15907W001 (013-0627PCT) 19 PATENTThe locking protrusion 164 is received within a corresponding hole or depression 160 in the outer surface 162 of the distal ring portion 148 of the ring electrode 120 when mounted. The interaction between the locking protrusion(s) 164 and the hole(s) or depression(s) 160 may mechanically secure the ring electrode 120 to the housing 140 and permit efficient torque transfer between the two components. The housing 140 has two locking protrusions 164 in Figure 5, and the ring electrode 120 has two holes or depressions 160 that receive the locking protrusions 164. When coupled, the housing 140 may be rotatably fixed to the ring electrode 120. For example, rotational torque applied to the ring electrode 120 is transferred to the housing 140, at least in part via the mechanical connection of the protrusions 164 and the holes or depressions 160.

[0079] In an example, the housing 140 may include a shoulder 168 along the inner surface 166. The shoulder 168 is a step feature between the proximal region 161 and a middle region 169 of the housing 140. The shoulder 168 may increase the grip between the housing 140 and the ring electrode 120. For example, the shoulder 168 may be sized and positioned to abut against a distal face 170 (shown in Figure 4) of the distal ring portion 148 of the ring electrode 120. The distal face 170 of the ring electrode 120 may be bonded to the shoulder 168 via a medical grade adhesive.

[0080] In an example, the housing 140 is designed to provide rotational torque transfer from the ring electrode 120 to the fixation helix 106. As such, rotation of the ring electrode 120 in a first rotational direction may cause the housing 140 and the fixation helix 106 to also rotate in the first rotational direction. This torque transfer may assist with burrowing the distal segment 130 of the implantable lead 100 into the patient tissue. The housing 140 may have several characteristics and / or features to enable efficient torque transfer with limited risk of damage to the lead components. For example, forming the housing 140 as a monolithic (e.g., one-piece, unitary) tubular member may assist with torque transfer by eliminating interfaces (e.g., seams) along the length of the housing 140.15907W001 (013-0627PCT) 20 PATENTSeams may be weak points. In another example, the housing 140 may have a relatively thick wall thickness, at least along the middle region 169. The thick wall thickness along the middle region 169 between the ring electrode 120 and the fixation helix 106 may permit torque transfer along the wall while increasing the torsional strength. The increased torsional strength resists twisting or other deformation of the tubular member 153 of the housing 140 along its length, which could damage the housing 140 and / or the internal components within the lumen 142. In another example, the torsional strength of the housing 140 may be increased due to the material composition of the housing 140. For example, the housing 140 may be constructed as a composite structure. The composite structure may include at least one stiffening material (e.g., fibers, a binder, etc.) embedded within a polymer material. The above-described examples for enabling efficient torque transfer may be combined.

[0081] In an example, the housing 140 may include one or more features designed to reduce or limit friction exerted on the housing 140 when burrowing the distal segment 130 of the implantable lead 100 into the patient tissue. For example, the housing 140 may include a helix 180 (referred to herein as a housing helix) along the outer surface 146 of the housing 140. The housing helix 180 is partially in phantom in Figure 5 because the housing 140 is shown in cross-section. The housing helix 180 has turns (referred to herein as first turns) 182 that circumferentially wrap around the housing 140. For example, the first turns 182 encircle the cylindrical housing 140. The housing helix 180 extends along a length (e.g., at least a portion) of the housing 140. For example, the housing helix 180 may extend along the middle segment 169. The housing helix 180 may extend a majority of the length of the housing 140. The distal end of the housing helix 180 may be at the tapered lead-in surface 155.

[0082] The housing helix 180 may assist with burrowing by screwing into the patient tissue. The housing helix 180 may work in tandem with the fixation helix 106. For example, the first turns 182 of the housing helix 180 may have a common15907W001 (013-0627PCT) 21 PATENTrotational direction as second turns 184 of the fixation helix 106, see Figure 4. For example, rotating the distal segment 130 of the implantable lead 100 in a first rotational direction may cause both the fixation helix 106 and the housing helix 180 to screw or worm in a penetration direction into the patient tissue. The housing helix 180 may function as an extension of the fixation helix 106. In an example, the first turns 182 of the housing helix 180 may have the same or approximately the same pitch as the second turns 184 of the fixation helix 106. For example, a first pitch 188 between the first turns 182 of the housing helix 180 may match a second pitch 190 (shown in Figure 4) between the second turns 184 of the fixation helix 106. The matching pitches may permit the housing helix 180 and the fixation helix 106 to provide a similar penetration distance per rotation. Matching pitches as used herein means that the first turns 182 of the housing helix 180 has approximately the same pitch, or preferably the same pitch, as the second turns 184 of the fixation helix 106. For example, two pitches that match each other may be identically the same in one example, may be different but within a manufacturing tolerance of each other (such that any difference in pitch is unintended) in another example, or may be different within a threshold range of each other (such as within 1 %, within 3%, or within 5% in different examples). The housing helix 180 may assist with burrowing by reducing torsional friction during the burrowing process. The housing helix 180 may also function as a secondary retention feature to retain the distal segment 130 of the implantable lead 100 secured at the target implant location within the patient tissue.

[0083] In the illustrated example, the housing helix 180 is defined by a recessed helical groove 192 along the outer surface 146 of the housing 140. The recessed helical groove 192 is a depression that defines the first turns 182 and continuously extends the length of the housing helix 180. The recessed helical groove 192 may allow tissue in-growth over time, which serves to secure the distal segment 130 of the implantable lead 100 in place at the target implant location. For example, patient tissue may grow into the recessed helical groove 192, reducing the risk of implantable lead migration.15907W001 (013-0627PCT) 22 PATENT

[0084] Figure 6 is a perspective view of the housing 140 shown in Figure 5. In an example, the housing 140 has a cylindrical shape. The housing 140 defines the lumen 142 extending through a full length of the housing 140 from the distal face 144 to the proximal face 154. Figure 7 is an enlarged view of a portion of the housing 140 shown in Figure 6. In an example, the housing helix 180 includes multiple stepped cutout recesses 194 along a helical path of the housing helix 180. The stepped cutout recesses 194 may be features that assist with fixation of the implantable lead 100 at the target implant location of the patient. For example, the cutout recesses 194 may assist with securing the distal segment 130 in place in the septal wall 32. Maintaining the distal segment 130 of the implantable lead 100 at the target implant location over time is useful for maintaining CSP and long IMD battery life.

[0085] The stepped cutout recesses 194 includes shoulder surfaces 196 on a first side of the recesses 194 but no shoulder surfaces on the opposite side of the recesses 194. For example, the shoulder surfaces 196 in Figure 7 are located on the left of the recesses 194. The shoulder surfaces 196 are formed to have negligible or no effect on rotation of the housing 140 in a first direction 197 of the housing 140, while impeding or resisting rotation of the housing 140 in the second direction 198 opposite the first direction 197. As shown in Figure 7, rotation of the housing 140 in the second direction 198 would cause the shoulder surfaces 196 to abut or dig into patient tissue, increasing mechanical interference and friction between the housing 140 and the tissue. Rotation of the housing 140 in the first direction 197 would not cause the same effect because the right side of the recesses 194 lack shoulder surfaces 196. In Figures 6 and 7, the stepped cutout recesses 194 may be formed in the outer surface 146 of the housing 140 between turns 182 of the recessed helical groove 192. In other examples in which the housing helix 180 is formed by a helical ridge that protrudes from the outer surface 146, stepped cutout recesses like the stepped cutout recesses 194 in this example can be formed in the helical ridge, rather than along the outer surface 146.15907W001 (013-0627PCT) 23 PATENT

[0086] The housing helix 180 may have other shapes and / or designs in other examples of the housing 140. For example, the housing helix 180 may be a helical ridge the projects outward from the outer surface 146. Figure 8 is a perspective view of the distal segment 130 of the implantable lead 100 including a housing 140 according to another embodiment. The housing 140 in Figure 8 is similar to the housing 140 in Figures 5 through 7, but the housing helix 180 is different. For example, rather than being formed by a recessed helical groove in the outer surface 146, the housing helix 180 in Figure 8 is defined by a continuous helical ridge 202 that protrudes radially outward from the outer surface 146 of the housing 140. The characteristics of the housing helix 180 in Figure 8, such as the length, turns, pitch, etc. may be the same or similar to the characteristics of the housing helix 180 in Figures 5 through 7. The housing helix 180 in Figure 8 may function to assist with burrowing just like the housing helix 180 in Figures 5 through 7. For example, the helical ridge 202 may reduce fiction and provide threaded contact area that acts with the fixation helix 106 to worm the distal segment 130 through the patient tissue (e.g., septal wall 32). Although not shown in Figure 8, the helical ridge 202 may define stepped cutout recesses like the stepped cutout recesses 194 in Figures 6 and 7 to assist with lead fixation at the target implant location. The stepped cutout recesses may be defined along the outer (e.g., radial) perimeter of the helical ridge 202, rather than along the outer surface 146.

[0087] Figure 9 is a perspective view of the distal segment 130 of the implantable lead 100 including a housing 140 according to a further embodiment. The housing 140 in Figure 9 is similar to the housing 140 in Figures 5 through 7 and the housing 140 in Figure 8, but the housing helix 180 is different. For example, the housing helix 180 in Figure 9 is defined by a discontinuous helical ridge 212 that protrudes radially outward from the outer surface 146 of the housing 140. The discontinuous helical ridge 212 includes multiple fins 214 that individually project from the outer surface 146. The fins 214 are arranged in a helical line that coils (e.g., wraps) around the cylindrical perimeter of the housing 140. Each of the fins15907W001 (013-0627PCT) 24 PATENT214 may taper towards the distal end 114 of the lead body 110 to define a respective ramp surface 216.

[0088] The characteristics of the housing helix 180 in Figure 9, such as the length, turns, pitch, etc. may be the same or similar to the characteristics of the housing helix 180 in Figure 8 and / or the housing helix 180 in Figures 5 through 7. The housing helix 180 in Figure 9 may function to assist with burrowing just like the previously-described housing helices 180. For example, the discontinuous helical ridge 212 may reduce fiction and provide threaded contact area that acts with the fixation helix 106 to worm the distal segment 130 through the patient tissue (e.g., septal wall).

[0089] In an example, the fins 214 may be shaped to function as fixation elements, similar to the stepped cutout recesses 194 in Figures 6 and 7. For example, the fins 212 may include shoulder surfaces 218 that drop from the top of the ramp surfaces 216 to the outer surface 146 of the housing 140. The shoulder surfaces 218 may function similar to the shoulder surfaces 196 of the cutout recesses 194 in Figure 7, resisting rotation of the housing 140 in a specific direction but permitting rotation in the other direction. The fins 214 may be arranged so that when the housing 140 is rotated in a first rotational direction that causes the housing 140 to burrow deeper into the patient tissue, the ramp surfaces 216 precede the shoulder surfaces 218 in engagement of the tissue. When rotated in the opposite direction that would cause the housing 140 to back out of the tissue, due to the housing helix 180, the shoulder surfaces 218 precede the ramp surfaces 216. The shoulder surfaces 218 engaging the tissue first impedes rotation of the housing 140 in the second rotational direction, which resists the distal segment 130 from backing out of the tissue.

[0090] Referring now generally to the example housings 140 described above, the housing 140 may include one or more features to provide depth control. More specifically, the housing 140 may have feature(s) designed to prohibit advancement into the patient tissue beyond a designated length or depth. In an15907W001 (013-0627PCT) 25 PATENTexample application in which the distal segment 130 of the implantable lead 100 is inserted into the interventricular septal wall 32 from the right ventricle, the depth control feature(s) may be used to prevent or at least prohibit the fixation helix 106 from perforating the back surface of the septal wall 32 into the left ventricle. The depth control feature(s) may be located at a position along the length of the housing 140 so that the distance from the depth control feature(s) to the distal end of the fixation helix 106 (when extended) corresponds to a desired depth of the implantable lead 100 into the patient tissue. In the septal wall 32, the desired depth may be the distance from the front surface of the septal wall 32 along the right ventricle to the LBB. In some patients, that distance may be about 10 mm (1 cm) or 11 mm. In various examples, the depth control features described herein may be located a distance of between 5 mm and 15 mm from the distal end 114 of the lead body 110.

[0091] A first example depth control feature is shown in Figures 5 and 6. The housing 140 in Figures 5 and 6 has an annular ridge 199 protruding radially outward from the outer surface 146 of the housing 140. The annular ridge 199 has a greater diameter than the outer surface 146 of the housing 140 next to the annular ridge 199. The annular ridge 199 may function like a bumper that abuts against the patient tissue. The size of the ridge 199 restricts entering the patient tissue. The annular ridge 199 is located at the proximal end of the housing 140 and defines part of the proximal face 154. The annular ridge 199 may be formed at a location that is spaced apart from the proximal face 154 in another example. The positioning of the annular ridge 199 may be selected based on the length of the housing 140 and the desired depth of insertion into the patient tissue.

[0092] In another example, the housing 140 may include tines as depth control features instead of the annular ridge 199. Figure 10 is a perspective view of a portion of the implantable lead 100 showing a set of tines 230 as depth control features according to an example. The tines 230 may be small posts or tabs. The tines 230 may be circumferentially spaced apart around the implantable lead 100.15907W001 (013-0627PCT) 26 PATENTThe tines 230 may be used instead of the annular ridge 199 shown in Figures 5 and 6. For example, the axial position of the tines 230 may correspond to the desired depth of insertion. The desired depth of insertion may be based on the length of the housing 140 and the desired depth of insertion into the patient tissue. Another set of tines 240 serving as depth control features is shown in Figure 8.

[0093] The distal segment 130 of the implantable lead 100 may also have one or more retention features to assist with retaining the distal segment 130 at the target implant location within the patient tissue. As described above, retention of the tip electrode 118 at the target implant location within the septal wall 32 over time allows for efficient pacing and sensing, thereby maintaining CSP and permitting a long battery life of the IMD 52. The cutout recesses 194 shown in Figures 6 and 7 and the sloped fins shown in Figure 9 are examples of retention features.

[0094] Another example retention feature is a set of bumps near the distal end of the housing 140. Figure 11 is a perspective view of a distal portion of the housing 140 according to an example. The housing 140 in Figure 11 includes a set of bumps 250 protruding from the outer surface 146 of the housing 140 near the distal face 144 of the housing 140. The bumps 250 may be circumferentially spaced apart around the perimeter of the housing 140. The bumps 250 may be located proximal to the tapered lead-in surface 155, but near the tapered lead-in surface 155. For example, the bumps 250 may be within 1 mm, 2 mm, or 3 mm of the tapered lead-in surface 155.

[0095] Another example retention feature is a set of tines near the distal end of the housing 140. Figure 12 is a perspective view of the distal portion of the housing 140 according to another example. The housing 140 in Figure 12 includes a set of tines 260 protruding from the outer surface 146 of the housing 140 near the distal face 144 of the housing 140. The tines 260 may be circumferentially spaced apart around the perimeter of the housing 140. The tines 260 may be located proximal to the tapered lead-in surface 155, but near the tapered lead-in15907W001 (013-0627PCT) 27 PATENTsurface 155. For example, the tines 260 may be within 1 mm, 2 mm, or 3 mm of the tapered lead-in surface 155. The tines 260 may be angled (e.g., slanted) relative to the outer surface 146 to lean towards a common rotational direction. The housing 140 can be rotated in that rotation direction during implant to avoid the tines 260 snagging on the tissue or otherwise substantially impeding the burrowing process.

[0096] Another example retention feature is a set of annular ribs near the distal end of the housing 140. Figure 13 is a perspective view of the distal portion of the housing 140 according to a third example. The housing 140 in Figure 13 includes a set of annular ribs 270 protruding from the outer surface 146 of the housing 140 near the distal face 144 of the housing 140. The ribs 270 may be circumferential rings that are stacked in an axial line for a length of the housing 140. The ribs 270 may be located proximal to the tapered lead-in surface 155, but near the tapered lead-in surface 155. For example, the ribs 270 may be within 1 mm, 2 mm, or 3 mm of the tapered lead-in surface 155. The ribs 270 may increase the surface area of the outer surface 146, resisting pull-out forces and encouraging tissue in-growth to retain the positioning of the implantable lead 100 over time.

[0097] The various features and examples described herein can be combined unless the combination of a first feature with a second feature would frustrate the function of one of the features or render one of the features useless. For example, at least one of the types of distal retention features shown in Figures 11 through 13 could be used with one of the types of housing helices 180 shown in Figures 5 through 9. The distal retention features would be located between the housing helix 180 and the distal face 144 and / or tapered lead-in surface 155. In another example, any of the depth control features (e.g., the annular ridge 199, the tines 230, or the tines 240) could be combined with any of the types of housing helices 180 shown in Figures 5 through 9 and / or any of the types of distal retention features shown in Figures 11 through 13.15907W001 (013-0627PCT) 28 PATENT

[0098] The housing 140 in these examples is described as a monolithic tubular member (e.g., sleeve or outer jacket). In another example, the housing 140 may be a combination of multiple components. For example, the housing 140 may be defined by a sleeve and a distal tip member. The distal tip member may extend from a distal end of the sleeve to the distal end of the housing 140. For example, the distal tip member may define the distal face 144.

[0099] Figure 14 is a flow chart of a method 300 for assembling an implantable lead 100 of an IMD 52 according to an embodiment. The method 300 may be used to assemble the distal segment 130 of the implantable lead 100 shown in Figures 4 through 13. In different embodiments, the method may include different steps not shown in Figure 14, may omit one or more of the steps shown in Figure 14, and / or may have a different order of the steps than shown in Figure 14. The order of the steps may vary from the order that is presented below. In one example, step 306 may occur prior to step 304.

[0100] At step 302, a housing 140 is formed that is configured to burrow into patient tissue. In an example CSP application, the patient tissue may be the interventricular septal wall 32. A target implant location may be the LBB within the septal wall 32. The housing 140 may be formed to define a lumen 142 therethrough. The housing 140 may be formed to include a housing helix 180 along an outer surface 146 of the housing 140. The housing helix 180 has first turns 182 that circumferentially wrap around the housing 140 and are spaced along a length of the housing 140. In an example, the housing 140 is formed by molding (e.g., injection molding).

[0101] At step 304, a proximal region 161 of the housing 140 is mounted to a ring electrode 120 of the implantable lead 100. In an example, a distal portion 148 of the ring electrode 120 may be inserted into the lumen 142 along the proximal region 161 of the housing 140 so that the proximal region 161 surrounds the distal portion 148 of the ring electrode 120. The two components may be mounted via a friction fit, chemical bonding, mechanical coupling, adhesive15907W001 (013-0627PCT) 29 PATENTbonding, and / or the like. For example, a medical grade adhesive may be used to bond the distal portion 148 of the ring electrode 120 to an inner surface 166 of the housing 140. In an example, the housing 140 includes at least one locking protrusion 164 that projects radially inward from the inner surface 166 of the housing 140. The proximal region 161 of the housing 140 may be aligned with the distal portion 148 of the ring electrode 120 so that the at one locking protrusion 164 is received within at least one hole or depression 160 in the ring electrode 120.

[0102] At step 306, a fixation helix 106 is loaded within the lumen 142 of the housing 140 so that the fixation helix 106 protrudes, or is extendable to selective protrude, from a distal face 144 of the housing 140. The fixation helix 106 may function as a tip electrode 118. The fixation helix 106 may have second turns 184 that have a common rotational direction as the first turns 182 of the housing helix 180.

[0103] Figure 15 illustrates a block diagram of an exemplary IMD 600 that is configured to be implanted into the patient. The IMD 600 may represent the IMD 52 shown in Figure 1 . The IMD 600 may treat both fast and slow arrhythmias with stimulation therapy, including cardioversion, pacing stimulation, an implantable cardioverter defibrillator, suspend tachycardia detection, tachyarrhythmia therapy, and / or the like. The IMD 600 is connectable to the implantable lead 100 according to the embodiments described herein.

[0104] The IMD 600 has a housing 661 to hold the electronic / computing components. A proximal end of the implantable lead 100, such as the terminal connection segment 108 of the implantable lead 100, may connect to the housing 661 of the IMD 600. The housing 661 (which is often referred to as the “can,” “case,” “encasing,” or “case electrode”) may be programmably selected to act as the return electrode for certain stimulus modes. The housing 661 further includes a connector (not shown) with a plurality of terminals 601 , 602, 604, 606, 608, and 610. The terminals may be connected to one or more leads (e.g., to the electrically15907W001 (013-0627PCT) 30 PATENTconductive contacts 122 at the terminal connection segment 108 of the implantable lead 100).

[0105] The IMD 600 includes a programmable microcontroller 620 that controls various operations of the IMD 600, including cardiac monitoring and stimulation therapy. The microcontroller 620 includes a microprocessor (or equivalent control circuitry), one or more processors, random access memory (RAM) and / or read-only memory (ROM) memory, logic and timing circuitry, state machine circuitry, and input / output (I / O) circuitry. The IMD 600 further includes a pulse generator 622 that generates stimulation pulses for connecting the desired electrodes to the appropriate I / O circuits, thereby facilitating electrode programmability. The switch 626 is controlled by a control signal 628 from the microcontroller 620.

[0106] Optionally, the IMD 600 may include multiple pulse generators, similar to the pulse generator 622, where each pulse generator is coupled to one or more leads / electrodes and controlled by the microcontroller 620 to deliver select stimulus pulse(s) to the corresponding one or more electrodes. The IMD 600 includes sensing circuit 644 selectively coupled to one or more electrodes that perform sensing operations, through the switch 626 to detect the presence of cardiac activity in the chamber of the heart. The output of the sensing circuit 644 is connected to the microcontroller 620 which, in turn, triggers, or inhibits the pulse generator 622 in response to the absence or presence of cardiac activity. The sensing circuit 644 receives a control signal 646 from the microcontroller 620 for purposes of controlling the gain, threshold, polarization charge removal circuitry (not shown), and the timing of any blocking circuitry (not shown) coupled to the inputs of the sensing circuit 624.

[0107] In the example of Figure 15, one sensing circuit 644 is illustrated. Optionally, the IMD 600 may include multiple sensing circuits 644, where each sensing circuit is coupled to one or more leads / electrodes and controlled by the microcontroller 620 to sense electrical activity detected at the corresponding one15907W001 (013-0627PCT) 31 PATENTor more electrodes. The sensing circuit 644 may operate in, for example, a unipolar sensing configuration or a bipolar sensing configuration.

[0108] The IMD 600 further preferably includes an analog-to-digital (A / D) data acquisition system (DAS) 650 coupled to one or more electrodes via the switch 626 to sample cardiac signals across any pair of desired electrodes. The A / D DAS 650 is configured to acquire intracardiac electrogram signals, convert the raw analog data into digital data and store the digital data for later processing and / or telemetric transmission to an external device 690 (e.g., a programmer, local transceiver, or a diagnostic system analyzer). The A / D DAS 650 is controlled by a control signal 656 from the microcontroller 620.

[0109] The microcontroller 620 is operably coupled to a memory 660 by a suitable data / address bus 662. The programmable operating parameters used by the microcontroller 620 are stored in the memory 660 and used to customize the operation of the IMD 600 to suit the needs of a particular patient. The operating parameters of the IMD 600 may be non-invasively programmed into the memory 660 through a telemetry circuit 664 in telemetric communication via communication link 667 (e.g., medical implant communication system (MICS), Bluetooth® low energy (BLE), and / or the like) with the external device 690.

[0110] The IMD 600 can optionally include one or more physiological sensors 670. Such sensors are commonly referred to as Tate-responsive” sensors because they are typically used to adjust pacing stimulation rates according to the exercise state of the patient. However, the physiological sensor 670 may further be used to detect changes in cardiac output, changes in the physiological condition of the heart, or diurnal changes in activity (e.g., detecting sleep and wake states). Signals generated by the physiological sensors 670 are passed to the microcontroller 620 for analysis. While shown as being included within the IMD 600, the physiological sensor(s) 670 may be external to the IMD 600, yet still, be implanted within or carried by the patient. Examples of physiological sensors might15907W001 (013-0627PCT) 32 PATENTinclude sensors that, for example, sense respiration rate, pH of blood, ventricular gradient, activity, position / posture, minute ventilation, and / or the like.

[0111] A battery 672 provides operating power to all of the components in the IMD 600. The battery 672 is capable of operating at low current drains for extended periods of time, and is capable of providing a high-current pulses (for capacitor charging) when the patient requires a shock pulse (e.g., in excess of 2 A, at voltages above 2 V, for periods of 10 seconds or more). The battery 672 also desirably has a predictable discharge characteristic so that elective replacement time can be detected. As one example, the IMD 600 employs lithium / silver vanadium oxide batteries.

[0112] The IMD 600 optionally includes an impedance measuring circuit 674, which can be used for many things, including sensing respiration phase. The impedance measuring circuit 674 is coupled to the switch 626 so that any desired electrode and / or terminal may be used to measure impedance in connection with monitoring respiration phase. The IMD 600 is further equipped with an optional communication modem (modulator / demodulator) 640 to enable wireless communication with other devices, implanted devices and / or external devices. In one implementation, the communication modem 640 may use high frequency modulation of a signal transmitted between a pair of electrodes. As one example, the signals may be transmitted in a high frequency range of approximately 10-80 kHz, as such signals travel through the body tissue and fluids without stimulating the heart or being felt by the patient. Such a form of communication is sometimes referred to as conductive communication.

[0113] Optionally, the microcontroller 620 may control an optional shocking circuit 680 by way of a timing control 632. The shocking circuit 680 generates shocking pulses as controlled by the microcontroller 620. The shocking circuit 680 may be controlled by the microcontroller 620 by a control signal 682.15907W001 (013-0627PCT) 33 PATENT

[0114] Although not shown, the microcontroller 620 may optionally include other dedicated circuitry and / or firmware / software components that assist in monitoring various conditions of the patient's heart and managing pacing therapies. As illustrative, but non-limiting examples, the microcontroller 620 may further include at least one of a timing control 632, an arrhythmia detector 634, a morphology detector 636 and multi-phase therapy controller 633. The timing control 632 is used to control various timing parameters, such as stimulation pulses (e.g., pacing rate, atria-ventricular (AV) delay, atrial interconduction (A-A) delay, ventricular interconduction (V-V) delay, etc.) as well as to keep track of the timing of RR-intervals, refractory periods, blanking intervals, noise detection windows, evoked response windows, alert intervals, marker channel timing, and the like.

[0115] The optional morphology detector 636 is configured to review and analyze one or more features of the morphology of cardiac activity signals. For example, in accordance with embodiments herein, the morphology detector 636 may analyze the morphology of detected R waves, where such morphology is then utilized to determine whether to include or exclude one or more beats from further analysis. For example, the morphology detector 636 may be utilized to identify nonconducted ventricular events, such as ventricular fibrillation and the like.

[0116] The optional arrhythmia detector 634 may be configured to apply one or more arrhythmia detection algorithms for detecting arrhythmia conditions. By way of example, the arrhythmia detector 634 may apply various detection algorithms. The arrhythmia detector 634 may be configured to declare a ventricular fibrillation episode based on the cardiac events.

[0117] The optional therapy controller 633 is configured to perform the operations described herein. The therapy controller 633 is configured to identify a multi-phase therapy based on the ventricular fibrillation episode, the multi-phase therapy including a pacing therapy. The therapy controller 633 is configured to manage delivery of the burst pacing therapy at a pacing site in a coordinated manner after the one or more shocks. The pacing site may be located at a target15907W001 (013-0627PCT) 34 PATENTSOI, such as a His Bundle. Optionally, other pacing sites may be located at one of a left ventricular (LV) site or a right ventricular (RV) site. The therapy controller 633 may manage delivery of the shock along a shocking vector between shocking electrodes.

[0118] Reference throughout this specification to “one embodiment” or “an embodiment” (or the like) means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in one embodiment” or “in an embodiment” or the like in various places throughout this specification are not necessarily all referring to the same embodiment.

[0119] The term “sized” as used herein is not limited to the act of manufacturing, but rather refers to a dimension similar to length, width, volume, etc. A lumen being sized to accommodate a specific component is not a method operation, but rather a characteristic of the lumen. The term “about” or “approximately” immediately preceding a stated numerical value, as used herein, indicates that the actual value can be + / - a designated threshold of the stated numerical value. The designated threshold may be 5%, 10% or the like of the stated numerical value.

[0120] It is to be understood that the above description is intended to be illustrative, and not restrictive. For example, the above-described embodiments (and / or aspects thereof) may be used in combination with each other. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the inventive subject matter without departing from its scope. While the dimensions and types of materials described herein are intended to define the parameters of the inventive subject matter, they are by no means limiting and are exemplary embodiments. Many other embodiments will be apparent to one of ordinary skill in the art upon reviewing the above description. The scope of the inventive subject matter should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are15907W001 (013-0627PCT) 35 PATENTentitled. In the appended claims, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. Further, the limitations of the following claims are not written in means-plus-function format and are not intended to be interpreted based on 35 U.S.C. § 112(f) unless and until such claim limitations expressly use the phrase “means for” followed by a statement of function void of further structure.15907W001 (013-0627PCT) 36 PATENT

Claims

WHAT IS CLAIMED IS:

1. An implantable lead comprising: a lead body that extends from a proximal end of the lead body to a distal end of the lead body, the proximal end configured to be connected to an implantable medical device, the lead body defining a lumen therethrough; a fixation helix that projects or is selectively extendable to project beyond the distal end of the lead body to penetrate tissue of a patient; and a ring electrode; wherein: the lead body includes a housing that is configured to burrow into the tissue of the patient with the fixation helix; the housing is mounted to the ring electrode and extends to the distal end of the lead body; an outer surface of the housing defines a portion of an exterior surface of the implantable lead; the housing includes a housing helix along the outer surface of the housing, the housing helix having first turns that circumferentially wrap around the housing along at least a portion of the housing, the first turns having a common rotational direction as second turns of the fixation helix.

2. The implantable lead of claim 1 , wherein a first pitch between the first turns of the housing helix matches a second pitch between the second turns of the fixation helix.

3. The implantable lead of claim 1 , wherein the housing helix is defined by a recessed helical groove along the outer surface of the housing.15907W001 (013-0627PCT) 37 PATENT4. The implantable lead of claim 1 , wherein the housing helix is defined by a continuous helical ridge that protrudes radially outward from the outer surface of the housing.

5. The implantable lead of claim 1 , wherein the housing helix includes multiple stepped cutout recesses into the outer surface of the housing along a helical path of the housing helix, wherein the stepped cutout recesses include shoulder surfaces that resist rotation of the housing in a direction opposite the rotational direction of the housing helix.

6. The implantable lead of claim 1 , wherein the housing helix is defined by a discontinuous helical ridge that protrudes radially outward from the outer surface of the housing, the discontinuous helical ridge composed of multiple fins, each of the fins tapering towards the distal end of the lead body to define a respective lead- in surface.

7. The implantable lead of claim 1 , wherein the housing tapers towards the distal end of the lead body to provide a lead-in surface into the tissue of the patient.

8. The implantable lead of claim 1 , wherein a distal face of the housing is smooth and a distal edge of the housing at an intersection between the outer surface and the distal face is curved to provide a lead-in surface into the tissue of the patient.

9. The implantable lead of claim 1 , wherein the housing is an electrically insulative and monolithic tubular member that extends from an exposed portion of the ring electrode to the distal end of the lead body.

10. The implantable lead of claim 1 , wherein a proximal region of the housing surrounds and mounts to a distal portion of the ring electrode, wherein the distal portion of the ring electrode includes at least one hole or depression along an outer surface of the ring electrode, wherein the proximal region of the housing includes at least one locking protrusion that projects radially inward from an inner15907W001 (013-0627PCT) 38 PATENTsurface of the housing and is received within the at least one hole or depression in the distal portion of the ring electrode.

11. The implantable lead of claim 1 , wherein a proximal region of the housing surrounds and mounts to a distal portion of the ring electrode, wherein an inner surface of the housing includes a shoulder, wherein the shoulder abuts against and is bonded to a distal face of the distal portion of the ring electrode.

12. The implantable lead of claim 1 , wherein the housing includes an annular ridge protruding radially outward from the outer surface of the housing, wherein a distance from the annular ridge to the distal end of the lead body is between 5 mm and 15 mm.

13. The implantable lead of claim 1 , wherein the housing includes multiple tines that protrude radially outward beyond the outer surface of the housing and are circumferentially spaced apart around the housing, wherein a distance from the tines to the distal end of the lead body is between 5 mm and 15 mm.

14. The implantable lead of claim 1 , wherein the housing includes multiple protrusions that are circumferentially spaced apart along the housing and located at a distal region of the housing proximate to the distal end of the lead body.

15. The implantable lead of claim 14, wherein the protrusions include tines that project from the outer surface of the housing at different respective angles, wherein the respective angles of the tines correspond to the rotational direction of the housing helix.

16. The implantable lead of claim 1 , wherein the housing includes multiple annular ridges protruding radially outward from the outer surface of the housing at the distal end of the lead body.

17. The implantable lead of claim 1 , wherein the fixation helix is selectively extendable relative to the housing between a retracted state and an extended15907W001 (013-0627PCT) 39 PATENTstate, wherein the housing is rotationally fixed to the fixation helix when the fixation helix is in the extended state so that the housing rotates with the fixation helix to penetrate the tissue of the patient.

18. An implantable lead comprising: a lead body that extends from a proximal end of the lead body to a distal end of the lead body, the proximal end configured to be connected to an implantable medical device, the lead body defining a lumen therethrough; a fixation helix that projects or is selectively extendable to project beyond the distal end of the lead body to penetrate tissue of a patient; and a ring electrode; wherein the lead body includes an electrically insulative and monolithic tubular housing that is configured to burrow into the tissue of the patient with the fixation helix; a proximal region of the tubular housing surrounds and mounts to a distal portion of the ring electrode and the tubular housing extends to the distal end of the lead body; an outer surface of the tubular housing defining a portion of an exterior surface of the implantable lead, the tubular housing including a housing helix along the outer surface thereof.

19. The implantable lead of claim 18, wherein the housing helix includes first turns that circumferentially wrap around the tubular housing along at least a portion of the tubular housing, and the first turns of the housing helix have a common rotational direction as second turns of the fixation helix.15907W001 (013-0627PCT) 40 PATENT20. The implantable lead of claim 19, wherein a first pitch between the first turns of the housing helix matches a second pitch between the second turns of the fixation helix.

21. The implantable lead of claim 19, wherein the housing helix includes multiple stepped cutout recesses into the outer surface of the housing along a helical path of the housing helix, wherein the stepped cutout recesses include shoulder surfaces that resist rotation of the housing in a direction opposite the rotational direction of the housing helix.

22. The implantable lead of claim 18, wherein the distal portion of the ring electrode includes at least one hole or depression along an outer surface of the ring electrode, wherein the proximal region of the tubular housing includes at least one locking protrusion that projects radially inward from an inner surface of the tubular housing and is received within the at least one hole or depression in the distal portion of the ring electrode.

23. The implantable lead of claim 18, wherein an inner surface of the tubular housing includes a shoulder, and the shoulder abuts against and is bonded to a distal face of the distal portion of the ring electrode.

24. The implantable lead of claim 18, wherein the housing helix is defined by a discontinuous helical ridge that protrudes radially outward from the outer surface of the tubular housing, the discontinuous helical ridge composed of multiple fins, each of the fins tapering towards the distal end of the lead body.

25. The implantable lead of claim 18, wherein the housing helix is defined by one of (i) a continuous helical ridge that protrudes radially outward from the outer surface of the tubular housing or (ii) a recessed helical groove along the outer surface of the tubular housing.15907W001 (013-0627PCT) 41 PATENT26. The implantable lead of claim 18, wherein the tubular housing tapers towards the distal end of the lead body to provide a lead-in surface into the tissue of the patient.

27. The implantable lead of claim 18, wherein a distal face of the tubular housing is smooth and a distal edge of the housing at an intersection between the outer surface and the distal face is curved to provide a lead-in surface into the tissue of the patient.

28. The implantable lead of claim 18, wherein the housing includes an annular ridge protruding radially outward from the outer surface of the housing, wherein a distance from the annular ridge to the distal end of the lead body is between 5 mm and 15 mm.

29. The implantable lead of claim 18, wherein the housing includes multiple tines that protrude radially outward beyond the outer surface of the housing and are circumferentially spaced apart around the housing, wherein a distance from the tines to the distal end of the lead body is between 5 mm and 15 mm.

30. The implantable lead of claim 18, wherein the fixation helix is selectively extendable relative to the tubular housing between a retracted state and an extended state, wherein the tubular housing is rotationally fixed to the fixation helix when the fixation helix is in the extended state so that the tubular housing rotates with the fixation helix to penetrate the tissue of the patient.15907W001 (013-0627PCT) 42 PATENT

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