Distal elements for implantable medical device

Abstract

A device comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis; an elongated body extending distally extending distally from the distal end of the elongated housing and defining a first electrode at or proximate a distal end of the elongated body; and one or more second electrodes disposed at or proximate the distal end of the elongated housing, wherein the one or more second electrodes are configured to contact wall tissue of the chamber without penetrating the wall tissue, wherein the elongated housing defines one or more ramps, each ramp of the one or more ramps extending at least partially around a perimeter of the elongated housing and along the longitudinal axis from a proximal surface to a distal surface, wherein the distal surface of each ramp defines at least a portion of the distal end of the elongated housing.

Description

DISTAL ELEMENTS FOR IMPLANTABLE MEDICAL DEVICE

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 675,589, filed July 25, 2024, the entire content of which is incorporated herein by reference.TECHICAL 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 cardiac pacemakers 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 IMD. More particularly, this disclosure is directed to IMDs with an electrode disposed at or near the distal end of the elongated housing.

[0006] In some examples, a single IMD is implanted in one chamber of a heart of the patient and is able to sense in and / or deliver cardiac pacing to more than one chamber, which may avoid the need for a leaded device or multiple smaller devices to provide such functionality, which may reduce the amount of material implanted within the patient. 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, and into wall tissue of another heart chamber. In addition to the distal electrode, the device includes a reference electrode and one or more proximal electrodes configured to contact the wall tissue of the heart chamber. The distal electrode may be a helix configured to penetrate tissue of the patient. The distal electrode may be configured to sense in and / or deliver cardiac pacing to one chamber of the heart and the one or more proximal electrodes may be configured to sense in and / or deliver cardiac pacing to another separate chamber of the heart.

[0007] In some examples, the IMD may need to be maintained in a substantially similar position and / or orientation relative to the cardiac tissue of the heart, e.g., to deliver consistent and efficacious cardiac pacing to one or more chambers of the heart. In some examples, this disclosure describes one or more sloped features (e.g., ramps) disposed on or proximate to a distal end of the IMD. The distal surface(s) of the one or more sloped features may interface with cardiac tissue, e.g., to inhibit unintended rotation of the IMD within the tissue. The distal surface(s) of the one or more sloped features may at least partially define a distal face of the IMD, from which a distal electrode may extend distally away from the IMD. Such a configuration may reduce compression, irritation, and / or inflammation of tissue around the distal electrode, which may improve efficacy of medical therapy delivered by the IMD to cardiac tissue via the distal electrode.

[0008] In some examples, the IMD includes one or more second electrodes disposed on the distal face of the IMD. Each second electrode may be configured to be placed incontact with cardiac tissue without penetrating the cardiac tissue. Each second electrode may be a cuff electrode (e.g., extending around the outer edge of the distal face of the IMD), a spring electrode, a button electrode, or the like. In some examples, IMD includes two or more second electrodes, which may be disposed along the circumference of the distal face of the IMD. With two or more second electrodes, the IMD may be configured to be implanted within the heart in wide range of locations and at a wide range of orientations, e.g., compared to an IMD with a single second electrode. In some examples, an IMD with two or more second electrodes may be capable of delivering cardiac pacing to a greater number of locations and / or distribute the cardiac pacing to at least a portion of the outer perimeter of the distal face of the IMD.

[0009] In some examples, this disclosure is directed to a device comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis, the elongated housing being configured to be implanted wholly within a chamber of a heart; an elongated body extending distally from the distal end of the elongated housing and defining a first electrode at or proximate a distal end of the elongated body; and one or more second electrodes disposed at or proximate the distal end of the elongated housing, wherein the one or more second electrodes are configured to contact wall tissue of the chamber without penetrating the wall tissue, wherein the elongated housing defines one or more ramps, each ramp of the one or more ramps extending at least partially around a perimeter of the elongated housing and along the longitudinal axis from a proximal surface to a distal surface, wherein the distal surface of each ramp of the one or more ramps defines at least a portion of the distal end of the elongated housing.

[0010] In some examples, this disclosure is directed to a device comprising: a housing extending from a proximal end to a distal end along a longitudinal axis, the housing being configured to be implanted wholly within a chamber of a heart; and an elongated body extending distally from the distal end of the elongated housing and defining an electrode at or proximate a distal end of the elongated body; and wherein the housing defines one or more ramps, each ramp of the one or more ramps extending at least partially around a perimeter of the housing and along the longitudinal axis from a proximal surface to a distal surface, wherein the distal surface of each ramp of the one or more ramps defines at least a portion of the distal end of the housing.

[0011] In some examples, this disclosure is directed to a device comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis, the elongated housing being configured to be implanted wholly within a chamber of a heart; an elongated body extending distally extending distally from the distal end of the elongated housing and defining a first electrode at or proximate a distal end of the elongated body; and one or more second electrodes disposed at or proximate the distal end of the elongated housing, wherein the one or more second electrodes are configured to contact wall tissue of the chamber without penetrating the wall tissue, and wherein each second electrode of the one or more second electrodes wraps around an outer edge of a distal end of the elongated housing.

[0012] In some examples, this disclosure is directed to a fixation device comprising: an elongated body extending distally from a distal end of an implantable medical device (IMD), the elongated body comprising a helix extending distally from the distal end of the IMD and defining one or more coils; and one or more ramps disposed at or proximate a distal portion of the IMD, each ramp of the one or more ramps extending at least partially around a perimeter of the IMD and along a longitudinal axis of the fixation device from a proximal surface to a distal surface, wherein the distal surface of each ramp of the one or more ramps defines at least a portion of the distal end of the IMD.

[0013] In some examples, this disclosure is directed to a method comprising: forming an elongated housing of an implantable medical device configured to be implanted wholly within a chamber of a heart, the elongated housing extending from a proximal end to a distal end along a longitudinal axis; removing material from the elongated housing to define one or more ramps, wherein each ramp of the one or more ramps extends at least partially around a perimeter of the elongated housing and along the longitudinal axis from a proximal surface to a distal surface, and wherein the distal surface of each ramp of the one or more ramps defines at least a portion of the distal end of the elongated housing; affixing an elongated body to the distal end of the elongated housing, wherein the elongated body defines a first electrode at or proximate to a distal end of the elongated body; and affixing one or more second electrodes to the distal end of the elongated housing, wherein the one or more second electrodes are configured to contact wall tissue of the chamber without penetrating the wall tissue.

[0014] 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

[0015] 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.

[0016] 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.

[0017] FIG. 2A is a perspective diagram illustrating an example configuration of the device of FIG. 1.

[0018] FIG. 2B is a perspective diagram illustrating another example configuration of the device of FIG. 1.

[0019] FIG. 2C is a perspective diagram illustrating another example configuration of the device of FIG. 1.

[0020] FIG. 3 A is a perspective diagram illustrating a side view of the example device of FIG. 2 A.

[0021] FIG. 3B is a perspective diagram illustrating a side view of the example device of FIG. 2B.

[0022] FIG. 3C is a perspective diagram illustrating a side view of the example device of FIG. 2C.

[0023] FIG. 4 is a block diagram illustrating an example configuration of an example device of any of FIGS. 1-3C.

[0024] FIG. 5 is a conceptual diagram of an example device of any of FIGS. 1-4 implanted at a target implant site.

[0025] FIG. 6 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. 1-5.

[0026] FIG. 7 is a flowchart illustrating an example process for manufacturing the example device of any of FIGS. 1-5.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 IMDs having one or more fixation features disposed at or around a distal end of an elongated housing of the IMD. Each fixation feature may define a textured outer surface. The fixation feature(s) may interface with a surface of a tissue (e.g., of a cardiac tissue) to inhibit unintended movement and / or rotation of the IMD relative to the tissue.

[0028] FIG. 1 is a conceptual diagram illustrating an example device 104 implanted in the heart 102 of a patient, in accordance with one or more aspects of this disclosure. Device 104 is shown implanted in the right atrium (RA) of the patient’s heart 102 in a target implant region 106, such as the triangle of Koch, 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. Target implant region 106 may lie between the bundle of His and the coronary sinus and may be adjacent the tricuspid valve. In some examples, target implant region 106 may be disposed in another position within heart 102, e.g., within a right ventricle (RV) of heart 102.

[0029] Device 104 includes a distal end 110 and a proximal end 116. Distal end 110 includes a first electrode 112, and one or more second electrodes 114. First electrode 112 may define a helical shape, e.g., as illustrated in FIG. 1. First electrode 112 extends from distal end 110 and may penetrate through the wall tissue of a first chamber (e.g., the RA in the illustrated example) into wall tissue of a second chamber (e.g., ventricular myocardium 108 of the LV in the illustrated example). Second electrode 114 may be may include, but is not limited to, a spring electrode, a button electrode, or a cuff electrode (e.g., on an outer perimeter of distal end 110 of device 104). Second electrode 114 may contact the wall tissue of the first chamber as first electrode 112 penetrates the wall tissue of the first chamber. In some examples, when device 104 is affixed to the wall tissue of the first chamber, second electrode 114 at least partially elastically deforms (e.g., compresses) toplace an electrically active region of second electrode 114 in contact with the wall tissue (e.g., without puncturing or penetrating the wall tissue). Device 104 may include two or more second electrodes 114 disposed around the outer perimeter of distal end 110, which may allow for delivery of cardiac pacing to tissue at or around target implant region 106 when device 104 is in different orientations and / or around the outer perimeter of distal end 110 of device 104.

[0030] In some examples, distal end 110 may include one or more sloped features (alternatively referred to herein as “one or more ramps”). Each ramp may extend from a proximal surface to a distal surface, e.g., with the distal surfaces of the one or more ramps defining a face of distal end 110. Each ramp may allow for movement of tissue into a space between distal end 110 and an outer surface of the ramp during implantation of device 104. The one or more ramps may interface with the tissue to inhibit unintended movement and / or rotation of device 104 within the tissue.

[0031] The configuration of electrodes 112 and 114 illustrated in FIG. 1 allows device 104 to sense cardiac signals and / or deliver cardiac pacing to multiple chambers of heart 102, e.g., the RA and ventricle(s) in the illustrated example. In this manner, the configuration of electrodes 112 and 114 may facilitate the delivery of multi-chamber pacing (e.g. DDD pacing) and / or A-V synchronous pacing by single device 104 implanted within the single chamber, e.g., the RA. While device 104 is implanted at target implant region 106 to sense in and / or pace the RA and 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 first electrode 112 may extend into tissue, e.g., myocardial tissue, of the LV or interventricular septum to, for example, facilitate the delivery of A-V synchronous pacing. 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. Such locations include any of the chambers of the heart, in the right atrium at the triangle of Koch or elsewhere therein, in the right ventricle at or near the apex thereof, or in the interventricular septum in the right ventricle, e.g. with the device implanted in the septum so as to enable conduction system pacing (CSP) such as leftbundle branch area pacing (LBBAP) with first electrode 112 selectively or non- selectively capturing the left bundle branch (LBB); in such a CSP / LBBAP application (or otherwise), second electrode 114 may optionally be omitted. In some examples, first electrode 112 extends into the tissue of heart 102 at region 106 and affixes device 104 to the tissue of heart 102.

[0032] FIG. 2A is a perspective diagram illustrating device 104A. Device 104A may include a housing 202 extending from a distal end 204 to a proximal end 206 along longitudinal axis 210. Device 104A may include one or more ramps 212 and one or more second electrodes 114A. First electrode 112 may extend distally from face 205 of device 104A at distal end 204 of housing 202 and along longitudinal axis 210. Each ramp 212 may extend from a proximal surface to a distal surface, with a distal surface of each ramp 212 at least partially defining or aligned with face 205. Each second electrode 114A may be disposed on a corresponding ramp 212, e.g., on a distal surface of the corresponding ramp 212.

[0033] 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.

[0034] Housing 202 extends between distal end 204 and proximal end 206 along longitudinal axis 210. 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 208, e.g., at proximal end 206, for engaging with a delivery tool during implantation of device 104 A. At distal end 204, housing 202 may define a face 205 of housing 202. Face 205 may define a distal end major surface. Face 205 may be orthogonal to longitudinal axis 210. In some examples, face 205 is slanted, e.g., face 205 defines a reference plane that is not orthogonal to longitudinal axis 210.

[0035] In some examples, an electrode assembly may include first electrode 112 connected to a bushing configured to be affixed to housing 202. The bushing may be atleast partially enclosed in coating formed from a polymer or silicon material (e.g., a silicon adhesive). First electrode 112 may extend distally through the coating. The distalmost surface of the coating may define face 205 when the electrode assembly is secured to housing 202.

[0036] First electrode 112 may extend distally from face 205 along longitudinal axis 210. In some examples, device 104A includes one or more fixation features (e.g., recesses, protrusions, ramps, meshes, tines, or the like) disposed on face 205. First electrode 112 may define a helical or spiral structure. First electrode 112 may extend distally from face 205 to a distal tip. First electrode 112 may define a first electrically active region 216 at or proximate to the distal tip of first electrode 112.

[0037] Housing 202 may define one or more sloped features 212 (alternatively referred to herein as “ramps 212”) at or proximate to distal end 204 of housing 202. Housing 202 may define one, two, three, four (e.g., as illustrated in FIG. 2 A), or five or more ramps 212. Ramps 212 may be uniform and / or evenly distributed around the outer perimeter of distal end 204 of housing 202. In some examples, at least one ramp 212 is different from another of ramps 212, e.g., to define a non-uniform distribution of ramps 212 at distal end 204. Each of ramps 212 may extend along and around longitudinal axis 210 from a proximal surface to a distal surface. In some examples, e.g., as illustrated in FIG. 2A, the distal surfaces of ramps 212 may at least partially define and / or be longitudinally aligned with face 205.

[0038] Each of ramps 212 may be configured to receive a portion of tissue (e.g., of heart 102) as device 104A is implanted within the tissue. Surfaces of ramps 212 (e.g., proximal surface and distal surface of each ramp 212, a drop-off surface between circumferentially adjacent ramps 212) may interface with tissue to inhibit unintended movement of device 104A (e.g., of first electrode 112) within the tissue. Ramps 212 may extend distally along longitudinal axis 210 in a same or different direction as the direction of winding for first electrode 112. For example, each ramp 212 may extend from the proximal surface to the distal surface in a clockwise direction and first electrode 112 may extend distally from face 205 in a counterclockwise direction, or vice versa. Each ramp212 may define a proximal surface wider than a distal surface, e.g., such that a width of ramp 212 tapers from the proximal surface to the distal surface.

[0039] Each ramp 212 may define a radi ally-inward edge and a radially-outward edge. The radially-inward edge may define a first radius and the radially-outward edge may define a second radius from a center of face 205. The second radius may be greater than the first radius. In some examples, the distal end of housing 202 may define an annular structure, e.g., disposed radially outwards of first electrode 112. In such examples, the inner circumference of the annular structure may define the first radius and the outer circumference of the annular structure may define the second radius.

[0040] Each ramp 212 may extending from the radially-inward edge to the radially- outward edge. The radially-inward edge may be radially outside of an outer circumference of first electrode 112. The radially-outward edge may be radially inside of or aligned with an outer perimeter of face 205. The distal surface of each ramp 212 may be aligned with one or both of the radially-inward edge or the radially-outward edge. The distal surface may extend along a reference plane orthogonal to longitudinal axis 210. The reference plane may extend along or may be parallel to face 205.

[0041] Device 104A may include one or more second electrodes 114A disposed on ramps 212. Each second electrode 114A may include, but is not limited to, a cuff electrode (e.g., as illustrated in FIG. 2A, a button electrode, a spring electrode, or the like. In some examples where second electrode 114A is a cuff electrode, as illustrated in FIG. 2A, second electrode 114A may extend from face 205, around an outer edge of face 205, and at least partially along an outer surface of housing 202 defining the outer perimeter of housing 202. Each second electrode 114A may define a second electrically active region 217. In some examples, as illustrated in FIG. 2A, second electrodes 114A may be disposed on distal surfaces of ramps 212. In such examples, second electrodes 114A may be aligned with face 205 of device 104 A.

[0042] First and second electrodes 112 and 114 may be formed of an electrically conductive material, such as titanium, platinum, iridium, tantalum, stainless steel or alloys thereof. In some examples, second electrode 114 is formed from one or more of Platinum Iridium, a Platinum Iridium-clad alloy (e.g., Platinum Iridium-clad Titanium orNitinol), Nitinol, or Tantalum Tungsten. First and second electrodes 112 and 114 may be coated with an electrically insulating coating, e.g., a parylene, polyurethane, silicone, epoxy, orother insulating coating, to reduce the electrically conductive active surface area of first and second electrodes 112 and 114, and thereby define first and second electrically active regions 216 and 217. In the example of FIG. 2A, first electrically active region 216 includes the distal end of electrode 112. In some examples, first electrically active region 216 is more proximate to the second, e.g., distal, end of first electrode 112.

[0043] Defining first and second electrically active regions 216 and 217 by covering portions with an insulating coating may increase the electrical impedance of first and second electrodes 112 and 114 and thereby reduce the current delivered during a pacing pulse that captures the cardiac tissue. A lower current drain conserves the power source, e.g., one or more rechargeable or non-rechargeable batteries, of device 104 A.

[0044] Second electrically active regions 217 of the one or more second electrodes 114A may each define a surface area of up to 6 square millimeters (mm2). For example, the surface area of each second electrically active region 217 may be up to 2.5 mm2, up to 4.2 mm2, or up to 5.8 mm2. An example of device 104A with more second electrodes 114A than an otherwise identical device 104A may include second electrodes 114A with reduced surface areas for each second electrically active regions 217 than the other device 104A, e.g., such that the total surface area of second electrically active region(s) 217 is independent of the number and / or type of second electrodes 114A on device 104A.Second electrodes 114A may be evenly distributed around the outer perimeter of device 104A, e.g., to allow for sensing of signals and / or delivery of pacing signals around at least a portion of the outer perimeter of device 104 A. In some examples, second electrodes 114A are concentrated around a specific portion of the outer perimeter of housing 202.

[0045] In the example of FIG. 2 A, first electrode 112 takes the form of a helix or a coil. First electrode 112 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. First electrode 112 may extend from face 205 from a proximal end to a distal end, e.g., defining first electrically active region 216. The proximal end may be a location along first electrode 112 where first electrode 112 extends distally past face 205 of device 104A.

[0046] In some examples, first electrode 112 includes one or more anti-rotation features. The anti-rotation features may facilitate fixation of first electrode 112 to thetissue. The additional anti-rotation features may include a shape of first electrode 112, dimensions (e.g., outer diameter, pitch, or the like) of first electrode 112, one or more features disposed on an outer surface of first electrode 112, or the like. The shape and / or dimensions of first electrode 112 may include a geometric shape of first electrode 112, a varying diameter configuration of first electrode 112, a varying pitch configuration of first electrode 112, a waveform configuration of first electrode 112, or any combination herein. The one or more anti-rotation features disposed on first electrode 112 may include, but are not limited to, elongated darts, barbs, or tines. In some examples, the anti-rotation features include bumps, ridges, recesses, and / or other texturing disposed on face 205. The one or more anti-rotation features may resist rotation of first electrode 112, e.g., by penetrating the tissue, by increasing the friction between first electrode 112 and the tissue, or the like.

[0047] First and second electrodes 112 and 114A may vary in size and shape in order to enhance tissue contact of first and second electrically active regions 216 and 217. For example, first electrodes 112 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. In some examples, second electrode 114 defines an outer surface that varies in size and shape (e.g., an oval outer surface, an outer surface with a larger diameter, or the like) in order to enhance tissue contact of second electrically active region 217.

[0048] The distal end of first electrode 112 can have a conical, hemi-spherical, or slanted edge distal tip with a narrow tip diameter, e.g., less than 1 millimeter (mm), for penetrating into and through tissue layers. The distal end of first electrode can be a sharpened or angular tip or sharpened or beveled edges, but the degree of sharpness may be constrained to avoid a cutting action that could lead to lateral displacement of the distal end of first electrode 112 and undesired tissue trauma. In some examples, first electrode 112 defines a maximum diameter at its base that interfaces with housing distal end 204. In such examples, the outer diameter of the helix defined by first electrode 112 may decrease from housing distal end 204 to the distal end of first electrode 112. In some examples, the diameter of first electrode 112 varies from a proximal end to the distal end of first electrode 112. The varying diameter may cause first electrode 112 to resist rotation within the tissue of heart 102.

[0049] The outer dimensions of first electrode 112 can be substantially straight and cylindrical, with first electrode 112 being rigid in some examples. First electrode 112 mayhave 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, first electrode 112 can be configured to maintain a distance between first electrically active region 216 and housing distal end 204.

[0050] Distal end of first electrode 112 can pierce through one or more tissue layers to position first electrically active region 216 within a desired tissue layer, e.g., the ventricular myocardium 108 or interventricular septum. Accordingly, first electrode 112 extends a distance from housing distal end 204 corresponding 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 210, to resist bending in a lateral or radial direction when a longitudinal, axial, and / or rotational force is applied, e.g., to the proximal end 206 of housing 202 to advance device 104 A into the tissue at target implant region 106. By resisting bending in a lateral or radial direction, first electrode 112 can maintain a spacing between a plurality of windings of first electrode 112 when first electrode 112 is a helix electrode. The spacing may be a pre-determined pitch of first electrode 112 and may vary from distal end 204 to the distal end of first electrode 112. First electrode 112 may be longitudinally non-compressible. First 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 first electrode 112 is not exposed to any external force, or to only a force along its longitudinal axis (substantially similar to or coincident with longitudinal axis 210), first electrode 112 retains a straight, linear configuration as shown.

[0051] As first electrode 112 enters tissue, second electrode(s) 114A may at least partially contact a surface of the tissue, e.g., as ramps 212 contact the surface of the tissue. Second electrode(s) 114A may interface with the surface of the tissue without penetrating the surface of the tissue. Second electrode(s) 114 may sense signals from and / or deliver cardiac pacing signals to the tissue surface. In some examples, where second electrode(s) 114 are cuff electrodes as illustrated in FIG. 2A, second electrode(s) 114 may sensesignals from and / or deliver cardiac pacing signals to tissue in contact with face 205 and / or with the outer surface of housing 202 extending around distal end 204 of housing 202.

[0052] All, substantially all, or a portion of housing 202 may function as an electrode 218, e.g., an anode, during pacing and / or sensing. In some examples, electrode 218 circumscribes a portion of housing 202 at or near proximal end 206. Electrode 218 can fully or partially circumscribe housing 202. FIG. 2A shows electrode 218 extending as a singular band around the outer perimeter of housing 202. Electrode 218 can also include multiple segments spaced a distance apart along a longitudinal axis 210 of housing 202 and / or around a perimeter of housing 202.

[0053] 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 218.

[0054] 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 218.

[0055] In some examples, electrode 218 is a component, such as a ring electrode, that is mounted or assembled onto housing 202. Electrode 218 may be electrically coupled to internal circuitry of device 104 A via electrically-conductive housing 202 or an electrical conductor when housing 202 is a non-conductive material. In some examples, electrode 218 is located proximate to proximal end 206 of housing 202 and can be referred to as a proximal housing-based electrode. Electrode 218 can also be located at other positions along housing 202, e.g., located proximately to distal end 204 or at other positions along longitudinal axis 210.

[0056] In some examples, second electrode(s) 114 or electrode 218 is paired with first electrode 112 for sensing ventricular signals and delivering ventricular pacing pulses. In some examples, one or more of second electrodes 114 are paired with electrode 218 or first electrode 112 for sensing atrial signals and delivering pacing pulses to atrial tissue (e.g., to the atrial endocardium) in target implant region 106. In other words, electrode 218is paired, at different times, with first electrode 112 and / or second electrode 114A for either ventricular or atrial functionality, respectively. In some examples, first and second electrodes 112 and 114A are paired with each other, with different polarities, for atrial and ventricular functionality. In some examples, first electrode 112 is paired with a single second electrode 114A of two or more second electrodes 114 A. In some examples, first electrode 112 is simultaneously paired with two or more second electrodes 114A, e.g., to allow for the sensing of signals from and / or delivery of cardiac pacing signals to tissue at two or more different locations around the outer perimeter of distal end 204 of housing 202.

[0057] In some examples, one or more second electrodes 114A are configured as atrial cathode electrodes for delivering pacing pulses to the atrial tissue, e.g., at target implant region 106 in combination with electrode 218. Second electrodes 114A and electrode 218 may also be used to sense atrial P-waves for use in controlling atrial pacing pulses (delivered in the absence of a sensed P-wave) and for controlling atrial-synchronized ventricular pacing pulses delivered using first electrode 112 as a cathode and electrode 218 as the return anode.

[0058] A distal end of first electrode 112 can be configured to rest within a ventricular myocardium of the patient, and one or more second electrodes 114 A can be configured to contact an atrial endocardium of the patient without penetration of the atrial endocardium. Device 104 A may include more or fewer electrodes than two electrodes. In some examples, device 104A includes one or more second electrodes 114A along housing distal end 204. For example, device 104A may include two or three electrodes configured for atrial functionality like second electrode 114 A, and the three electrodes may be substantially similar or different from one another. Spacing between a plurality of second electrodes 114A may be at an equal or unequal distance. Second electrode(s) 114A may be individually selectively coupled to sensing and / or pacing circuitry enclosed by housing 202 for use as an anode with first electrode 112 or as an atrial cathode electrode, or may be electrically common and not individually selectable. In some examples, in place of first electrode 112, device 104 A 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, electrically active region 216 can be positioned on a separate member and / or on the housing 202. In some examples, device104 A only includes first electrode 112 and electrode 218 and does not include any second electrodes 114 A.

[0059] In some examples device 104A includes one or more therapeutic substance dispensing devices, e.g., on face 205. The therapeutic substance dispensing devices may be configured to elute one or more steroids to tissue in proximity to the therapeutic substance dispensing devices over time. The steroid may mitigate inflammation of patient tissue resulting from interaction with device 104 A. In some examples, the therapeutic substance dispensing devices comprises one or more monolithic controlled release devices (MCRDs). In some examples, the therapeutic substance is disposed over at least a portion of the outer surface of fixation feature 212A.

[0060] FIG. 2B is a perspective diagram illustrating another example configuration of device 104 of FIG. 1, i.e., device 104B. FIG. 2C is a perspective diagram illustrating another example configuration of device 104 of FIG. 1, i.e., device 104C. Devices 104B, 104C may be substantially similar to device 104A previously described above with respect to FIG. 2A, aside from the differences described below.

[0061] In some examples, as illustrated in FIG. 2B, device 104B includes second electrodes 114B disposed on the outer surface of ramps 212 and between the distal and proximal surfaces of ramps 212. In some examples, as illustrated in FIG. 2C, device 104C includes second electrodes 114C disposed on the proximal surfaces of ramps 212. In some examples, second electrodes 114 (e.g., second electrodes 114A, 114B, 114C) may all be disposed on distal surfaces of ramps 212, on proximal surfaces of ramps 212, or along the outer surfaces of ramps 212 between the distal and proximal surfaces. In some examples, one or more second electrodes 114 maybe positioned on different locations along ramps 212 than one or more other second electrodes 114. Each of second electrodes 114 may be configured to sense signals from and / or deliver cardiac pacing signals to tissue. Each of second electrodes 114 may define second electrically active regions 217 of the same or different surface area. Each of second electrodes 114 may be a cuff electrode, a button electrode, a spring electrode, or the like.

[0062] In some examples, device 104 does not include ramps 212. In such examples, second electrodes 114 may be of the same type, define the same dimensions, and / or be placed on the same locations on distal end 204 of housing 202, e.g., as previously described herein with respect to FIGS. 2A-2C.

[0063] FIG. 3 A is a perspective diagram illustrating a side view of device 104A. FIG. 3B is a perspective diagram illustrating a side view of device 104B. FIG. 3C is a perspective diagram illustrating a side view of device 104C. As illustrated in FIGS. 3A - 3C, each of ramps 212 may extend from a proximal surface 302 to a distal surface 304 along a medial surface 306.

[0064] Distal surface 304 may be aligned with face 205 along reference plane 308. Proximal surface 302 may be aligned along reference plane 310. Each of reference plane 308, 310 may be orthogonal to longitudinal axis 210 or may be offset from longitudinal axis 210. Reference plane 308, 310 may be parallel and may be separated by a distance 312. Distance 312 may define a depth of ramps 212 along longitudinal axis 210. Distance 312 may be up to 2 millimeters (mm), e.g., up to 1.5 mm.

[0065] Distal surface 304 may be orthogonal to longitudinal axis 210 and may define at least a portion of face 205. Proximal surface 302 may be orthogonal to longitudinal axis 210 and may be parallel to or offset from distal surface 304. Proximal surface 302 may define a greater surface area than distal surface 304. One or more of proximal surface or distal surface 304 may define fixation features (e.g., texturing, protrusions, indentations), e.g., to improve fixation of device 104 within tissue. In some examples, as illustrated in FIGS. 3 A and 3C, second electrodes 114 (e.g., second electrodes 114A, 114C) may be disposed on one or more of distal surface 304 or proximal surface 302, respectively. In some examples where second electrode 114 is a cuff electrode, e.g., as illustrated in FIG.3 A, a portion of second electrode 114 (e.g., a portion of second electrically active region 217) may wrap around the outer edge of ramp 212 (e.g., an outer edge of distal surface 304, of proximal surface 302, of medial surface 306) to place at least a portion of second electrode 114 along the radially outer surface of housing 202.

[0066] Medial surface 306 of ramp 212 may connect proximal surface 302 to distal surface 304. Medial surface 306 may extend along and around longitudinal axis 210 from proximal surface 302 to distal surface 304. Medial surface 306 may extend in a direction the same as or opposite to a direction of winding of first electrode 112. Medial surface 306 may define a uniform or variable slope. For example, the slope of medial surface 306 around proximal surface 302 may be steeper than the slope of medial surface 306 around distal surface 304, or vice versa. In some examples, as illustrated in FIG. 3B, secondelectrodes 114 (e.g., second electrodes 114B) may be disposed on at least a portion of medial surface 306.

[0067] Circumferentially adjacent ramps 212 may be separated by ledges 314 (alternatively referred to as “drop-offs 314”). Each of ledges 314 may connect distal surface 304 of one ramp 212 to proximal surface 302 of a circumferentially adjacent ramp 212. Each ledge 314 may define a surface substantially orthogonal to the connecting distal surface 304 and / or proximal surface 302. Each ledge 314 may define a chamfered, filleted, or rounded edge at the ends connected to distal surface 304 and / or to proximal surface 302, e.g., to reduce irritation of tissue at target implant region 106. When device 104 is implanted within tissue, ledges 314 may interface with tissue at or around proximal surfaces 302 of ramps 212, e.g., to act against and inhibit unintended rotation of device 104 due to movement of the tissue.

[0068] Fixation feature 212B may be an elongated strip disposed on face 205. Fixation feature 212B may be disposed radially inwards of an outer perimeter of housing 202 and may be disposed radially outwards of first electrode 112. Fixation feature 212B may be radially and / or circumferentially offset from second electrode 114. Fixation feature 212B may be electrically isolated from first electrode 112, from second electrode 114, from electrode 218, and / or from one or more other electrical components disposed within housing 202.

[0069] FIG. 4 is a block diagram illustrating an example configuration of an example device 104 of any of FIGS. 1-3C. As illustrated in FIG. 4, device 104 include electrodes 112 and 114, which may be configured as described with respect to FIGS. 1-3C. In the example shown in FIG. 4, device 104 includes switch circuitry 402, sensing circuitry 404, signal generation circuitry 406, sensor(s) 408, processing circuitry 410, telemetry circuitry 412, memory 414, and power source 416. The various circuitry may be, or include, programmable or fixed function circuitry configured to perform the functions attributed to respective circuitry. Memory 414 may store computer-readable instructions that, when executed by processing circuitry 410, cause device 104 to perform various functions.Memory 414 may be a storage device or other non-transitory medium. The components of device 104 illustrated in FIG. 4 may be housed within housing 202.

[0070] Signal generation circuitry 406 generates electrical stimulation signals, e.g., cardiac pacing pulses. Switch circuitry 402 is coupled to electrodes 112, 114, and 218 andmay 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 402 is configured to direct stimulation signals from signal generation circuitry 406 to a selected combination of electrodes 112, 114, and 218, having selected polarities, e.g., to selectively deliver pacing pulses to the RA, ventricles, or interventricular septum of heart 102. For example, in order to pace one or both of the ventricles, switch circuitry 402 may couple first electrode 112, which has penetrated to wall tissue of a ventricle or the intraventricular septum, to signal generation circuitry 406 as a cathode, and one or both of one or more second electrodes 114 or electrode 218 to signal generation circuitry 406 as an anode. As another example, in order to pace the RA, switch circuitry 402 may couple one or more second electrodes 114, which maintains contact with the RA endocardium, to signal generation circuitry 406 as a cathode, and one or both of first electrode 112 or electrode 218 to signal generation circuitry 406 as an anode.

[0071] Each of electrodes 112, 114, 218 may be coupled to switch circuitry 402 via a corresponding feedthrough assembly. In some examples, each feedthrough assembly is substantially straight (e.g., along longitudinal axis 210). In some examples, such as when distal end 204 of housing 202 is removable from housing 202 (e.g., when distal end 204 is a removable header), the feedthrough assemblies are offset to allow for removal of distal end 204. For example, when a header defining distal end 204 is configured to be removably secured to housing 202 (e.g., via a turn-lock mechanism), the feedthrough assemblies are offset from longitudinal axis 210 to allow the header to turn relative to housing 202. In some examples, each of electrodes 112, 114, 218 and / or the corresponding feedthrough assemblies are electrically isolated from fixation features 212 on housing 202 of device 104.

[0072] Switch circuitry 402 may also selectively couple sensing circuitry 404 to selected combinations of electrodes 112, 114, and 218, e.g., to selectively sense the electrical activity of either the RA or ventricles of heart 102. Sensing circuitry 404 may include filters, amplifiers, analog-to-digital converters, or other circuitry configured to sense cardiac electrical signals via electrodes 112, 114, and / or 218. For example, switch circuitry 402 may couple each of first electrode 112 and second electrode 114 (in combination with electrode 218) to respective sensing channels provided by sensingcircuitry 404 to respectively sense either ventricular or atrial cardiac electrical signals. In some examples, sensing circuitry 404 is configured to detect events, e.g., depolarizations, within the cardiac electrical signals, and provide indications thereof to processing circuitry 410. In this manner, processing circuitry 410 may determine the timing of atrial and ventricular depolarizations, and control the delivery of cardiac pacing, e.g., AV synchronized cardiac pacing, based thereon. Processing circuitry 410 may include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), discrete logic circuitry, or any other processing circuitry configured to provide the functions attributed to processing circuitry 410 herein may be embodied as firmware, hardware, software or any combination thereof.

[0073] Sensor(s) 408 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) 408 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other types of sensors. Sensor(s) 408 may output patient parameter values that may be used as feedback to control sensing and delivery of therapy by device 104.

[0074] Telemetry circuitry 412 supports wireless communication between device 104 and an external programmer (not shown in FIG. 4) or another computing device under the control of processing circuitry 410. Processing circuitry 410 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 412. Telemetry circuitry 412 may accomplish communication by radiofrequency (RF) communication techniques, e.g., via an antenna (not shown).

[0075] In some examples, where device 104 includes two or more second electrodes 114, processing circuitry 410 may determine a selection of at least one second electrode 114 of the two or more second electrodes 114 for delivery of cardiac pacing signals to heart 102 (e.g., to RA of heart 102) and / or for sensing of signals from heart 102. Processing circuitry 410 may cause switch circuitry 402 to couple the selected at least one second electrode 114 to sensing circuitry 404 and / or to signal generation circuitry 406. Processing circuitry 410 may select the at least one second electrode 114 from the two or more second electrodes 114 in response to communications (e.g., from the externalprogrammer) received by telemetry circuitry 412. In some examples, processing circuitry 410 selects the at least one second electrode 114 based at least in part on one or more signals sensed by device 104 (e.g., via sensing circuitry 404, via sensor(s) 408). The one or more sensed signals may include, but are not limited to, sensed impedance values, pacing capture thresholds, or morphology and / or amplitude signatures of cardiac signals.

[0076] Power source 416 delivers operating power to various components of device 104. Power source 416 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.

[0077] FIG. 5 is a conceptual diagram of device 104 of any of FIGS. 1-4 implanted at one example of a target implant location 106. First electrode 112 may be inserted (e.g., in a manner similar to rotating and advancing a threaded screw) such that tissue becomes engaged with the helix of first electrode 112. As first electrode 112 becomes engaged with tissue, first electrode 112 pierces into the tissue at target implant region 106 and advances through atrial myocardium 506 and central fibrous body 502 to position first electrically active region 216 in ventricular myocardium 108 as shown in FIG. 5. In some examples, first electrode 112 penetrates into the interventricular septum. In some examples, first electrode 112 does not perforate either of the ventricular endocardial or epicardial surface.

[0078] In some examples, manual pressure applied to the housing proximal end 206, e.g., via an advancement tool, provides the longitudinal force to pierce the cardiac tissue at target implant region 106. In some examples, actuation of an advancement tool rotates device 104 and first electrode 112 configured as a helix about longitudinal axis 210. The rotation of the helix about the longitudinal axis 210 advances first electrode 112 through atrial myocardium 506 and central fibrous body 502 to position first electrically active region 216 in ventricular myocardium 108 as shown in FIG. 5.

[0079] As first electrode 112 advances into the tissue, the distance between second electrode 114 and atrial endocardium 504 decreases until second electrode 114 contact, and may press against, the surface of atrial endocardium 504. In some examples, as first electrode 112 advances into the tissue, portions of atrial endocardium 504 may enter a space between face 205 and ramps 212 and abut against portions of ramps 212 (e.g., proximal surfaces 302, distal surfaces 304, medial surfaces 306, ledges 314 of ramps 212).Atrial endocardium 504 may interface and apply forces against the portions of ramps 212 (e.g., against medial surface 306, ledges 314 of ramps 212) to inhibit movement and / or rotation of device 104 due to movement of tissue of heart 102 (e.g., movement of ventricular myocardium 108, atrial myocardium 506, central fibrous body 502, or the like) or blood flow during cardiac function. As ramps 212 are more proximal to face 205 along longitudinal axis 210, portions of atrial endocardium 504 interfacing with ramps 212 may exhibit reduced inflammation and / or irritation, e.g., compared to other devices 104 with ramps on face 205.

[0080] Target implant region 106 in some pacing applications is along atrial endocardium 504, substantially inferior to the AV node and bundle of His. For example, target implant region 106 may be at least partially within the Triangle of Koch of heart 102. First electrode 112 can have a length that penetrates through atrial endocardium 504 in target implant region 106, through the central fibrous body 502 and into ventricular myocardium 108 without perforating through the ventricular endocardial surface. In some examples, when the full length of first electrode 112 is fully advanced into target implant region 106, first electrically active region 216 rests within ventricular myocardium 108 and second electrode 114 is positioned in intimate contact with atrial endocardium 504. First electrode 112 may extend from housing distal end 204 approximately 3 mm to 12 mm in various examples. In some examples, first electrode 112 may extend a distance from distal end 204 by at least 3 mm. The diameter of an elongated body defining first electrode 112 may be 4 mm or less, e.g., may be 1 mm or less, may be 0.6 mm or less. An outer diameter of the helix or coil defined by first electrode 112 may be up to 6 mm (e.g., up to 4 mm).

[0081] FIG. 6 is a flow diagram illustrating an example process for sensing a cardiac electrical signal and delivering cardiac pacing therapy to heart 102 of a patient via an device 104 of any of FIGS. 1-6. The technique of FIG. 7 will be described with concurrent reference to device 104 as illustrated in FIGS. 1-6, although a person having ordinary skill in the art will understand that the technique may be performed in reference to an implantable medical lead or other medical device.

[0082] A clinician may insert device 104 within a single first chamber of the heart 102 (602). The first chamber of heart 102 may be the right atrium, left atrium, the right ventricle, or the left ventricle. The clinician may insert device 104 into the first chambervia delivery tool connected to device 104 (e.g., connected to delivery tool interface member 208). The clinician may advance first electrode 112 extending distally from housing 202 of device 104 to penetrate through wall tissue of the first chamber and into wall tissue of a second chamber of heart 102 (604). In some examples, advancing first electrode 112 includes positioning a distal end of first electrode 112 (e.g., a first electrically active region 216) within a ventricular myocardium 108 of the patient. The clinician may advance first electrode 112 by rotating device 104 clockwise or counterclockwise within the first chamber, depending on how first electrode 112 is wound. Depending on the surface features (e.g., surface curvature) of tissue within the target implantation region 106, the clinician may implant device 104 into the tissue orthogonally or at an angle.

[0083] The clinician may cause device 104 to maintain contact between second electrode 114 and the wall tissue of the first chamber, without penetrating the wall tissue of the first chamber (606). The clinician may continue to advance first electrode 112 into the tissue until at least a portion of face 205 and surfaces of ramps 212 of distal end 204 of device 104 contact the surface of the tissue. The tissue may enter spaces separating face 205 and ramps 212 to at least partially envelop face 205 and contact surfaces (e.g., proximal surfaces 302, distal surfaces 304, medial surfaces 306, ledges 314) of ramps 212. Once device 104 is implanted within the wall tissue, portions of the wall tissue may interfaces with and / or act against surfaces of ramps 212, e.g., to inhibit unintended movement and / or rotation of device 104 within the wall tissue. For example, movement within the wall tissue may apply a torque on first electrode 112, and ramps 212 may act against the wall tissue to resist rotation of device 104 due to the torque.

[0084] Device 104 may deliver cardiac pacing from device 104 to the second chamber via first electrode 112 and to the first chamber via second electrode 114 (608). Device 104 may deliver cardiac pacing to the first chamber and / or the second chamber via first electrode 112, second electrode 114, and / or one or more other electrodes of device 104 (e.g., electrode 218).

[0085] FIG. 7 is a flowchart illustrating an example process for manufacturing the example device of any of FIGS. 1-5. While FIG. 7 is primarily described with respect to device 104 A as illustrated in FIG. 2 A, the techniques described herein may be applied to any other example device described herein.

[0086] A manufacturing assembly may form an elongated housing (e.g., housing 202) of an IMD (e.g., device 104A) (702). The manufacturing assembly may form at least a portion of housing 202 via one or more conductive materials and / or one or more non- conductive materials. The manufacturing assembly may form housing 202 to define an outer surface and an inner volume configured to retain components of device 104, e.g., as illustrated and described above with respect to FIG. 4.

[0087] The manufacturing assembly may form a distal portion of housing 202 (e.g., at or around distal end 204 of housing 202) from a non-conductive material including, but is not limited to, PEEK. In some examples, the distal portion is a removable header of housing 202. In such examples, the manufacturing assembly may insert components of device 104 into the inner volume of housing 202 prior to affixing the removable header to the remainder of housing 202 to enclose the inner volume of housing 202. The manufacturing assembly may dispose one or more feedthrough assemblies through the removable header prior to affixing the removable header to the remainder of housing 202. In some examples, the manufacturing assembly may affix an electrode assembly (e.g., including a bushing and first electrode 112) to the removable header, e.g., after the removable header is affixed to the remainder of housing 202. Once the electrode assembly is affixed to housing 202, a distal surface of the bushing and / or a material enclosing the bushing may define face 205 of housing 202.

[0088] The manufacturing assembly may form one or more ramps 212 at or around distal end 204 of elongated housing 202 (704). In some examples, the manufacturing assembly may remove material from distal end 204 of housing 202 (e.g., via machining, via a cutting instrument, via a chemical process) to define ramps 212. In some examples, the manufacturing assembly forms ramps 212 via a molding process and / or an additive manufacturing process (e.g., via 3D printing). In some examples where device 104A includes a removable header, the manufacturing assembly may form ramps 212 on removable header prior to or after affixation of the removable header to the remainder of housing 202. Once formed, ramps 212 may define proximal surfaces 302, distal surfaces 304, medial surfaces 306 connecting proximal surfaces 302 to distal surfaces 304, and ledges 314 separating ramps 212. The manufacturing assembly may form ramps 212 to be identical and / or to define different dimensions.

[0089] In some examples, the manufacturing assembly form recesses on one or more of ramps 212. Each recess may be sized to retain second electrode 114 and / or a feedthrough assembly portion of second electrode 114. In some examples, the recesses are on or along the outer edge of distal end 204 of housing 202 (e.g., on the outer edge of one or more ramps 212). In some examples, the recesses are radially outwards of first electrode 112 and radially inwards of the outer perimeter of distal end 204 of housing 202. In some examples, where device 104 A does not include ramps 212, the manufacturing assembly forms the recesses on face 205 of device 104 A. The manufacturing assembly may form the recesses prior to or after affixing first electrode 112 to housing 202.

[0090] The manufacturing assembly may affix one or more second electrodes 114 (e.g., second electrodes 114A, 114B, 114C) to elongated housing 202 at or around distal end 204 of elongated housing 202 (706). In some examples, wherein elongated housing 202 defines one or more ramps 212 at or around distal end 204, the manufacturing assembly may affix the one or more second electrodes 114 to one or more surfaces of ramps 212 (e.g., to proximal surfaces 302, distal surfaces 304, and / or medial surfaces 306). In some examples, wherein elongated housing 202 does not define any ramps 212, the manufacturing assembly may affix the one or more second electrodes 114 on face 205 and / or on an outer edge of distal end 204.

[0091] The manufacturing assembly may affix the one or more second electrodes 114 to housing 202 by press-fitting the one or more second electrodes 114 into recesses at or around distal end 204 of housing 202 (e.g., on ramps 212, on face 205). In some examples, the manufacturing assembly may affix the one or more electrodes 114 to housing 202 via an adhesive, via a mechanical attachment mechanism, or the like. Once affixed each second electrode 114 may be electrically connected to components within the inner volume of housing 202, e.g., via a corresponding feedthrough assembly. Second electrodes 114 may be individually electrically coupled or collectively electrically coupled to components of device 104 A (e.g., to switch circuitry 402).

[0092] The manufacturing assembly may affix first electrode 112 to housing 202 by inserting a portion of an electrode assembly containing first electrode 112 (e.g., a bushing connected to first electrode 112) into a recess within face 205 of housing 202. Once first electrode 112 is affixed to housing 202, portions of the electrode assembly mayelectrically couple first electrode 112 to components of device 104A (e.g., to switch circuitry 402) via one or more feedthrough assemblies.

[0093] 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. For example, device 104 may only include ramps 212 and not second electrodes 114 of the types described herein, may include both ramps 212 and second electrodes 114, or may include second electrodes 114 and not ramps 212.

[0094] 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.

[0095] 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 media may 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).

[0096] 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.

[0097] 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 forimplementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0098] This disclosure describes each of the following examples.

[0099] Example 1 : a device comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis, the elongated housing being configured to be implanted wholly within a chamber of a heart; an elongated body extending distally from the distal end of the elongated housing and defining a first electrode at or proximate a distal end of the elongated body; and one or more second electrodes disposed at or proximate the distal end of the elongated housing, wherein the one or more second electrodes are configured to contact wall tissue of the chamber without penetrating the wall tissue, wherein the elongated housing defines one or more ramps, each ramp of the one or more ramps extending at least partially around a perimeter of the elongated housing and along the longitudinal axis from a proximal surface to a distal surface, wherein the distal surface of each ramp of the one or more ramps defines at least a portion of the distal end of the elongated housing.

[0100] Example 2: the device of example 1, wherein the distal end of the elongated housing has an annular shape defined by first and second radii, and the distal surface of each ramp of the one or more ramps spans the distance between the first radius and the second radius.

[0101] Example 3: the device of example 2, wherein the distal surface of each ramp of the one or more ramps forms an edge which is aligned with the first radius or the second radius.

[0102] Example 4: the device of example 2, wherein the distal surface of each ramp of the one or more ramps forms an edge which resides in a plane which is orthogonal to the longitudinal axis of the elongated housing.

[0103] Example 5: the device of any of examples 1-4, wherein at least one second electrode of the one or more second electrodes are disposed on the distal surface of at least one ramp of the one or more ramps.

[0104] Example 6: the device of any of examples 1-5, wherein at least one second electrode of the one or more second electrodes are disposed on the proximal surface of at least one ramp of the one or more ramps.

[0105] Example 7: the device of any of examples 1-6, wherein at least one second electrode of the one or more second electrodes are disposed on an outer surface of and between the proximal surface and the distal surface of at least one ramp of the one or more ramps.

[0106] Example 8: the device of any of examples 1-7, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface and about the longitudinal axis in a first direction, wherein the elongated body defines a helix, and wherein the helix is wound about the longitudinal axis in a second direction, the second direction being the same as the first direction.

[0107] Example 9: the device of any of examples 1-7, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface and about the longitudinal axis in a first direction, wherein the elongated body defines a helix, and wherein the helix is wound about the longitudinal axis in a second direction, the second direction being opposite the first direction.

[0108] Example 10: the device of any of examples 1-9, wherein the one or more ramps comprises a first ramp and a second ramp, wherein the distal surface of the first ramp is circumferentially adjacent to the proximal surface of the second ramp, and wherein the distal surface of the first ramp is separated from the proximal surface of the second ramp by a ledge extending substantially along the longitudinal axis.

[0109] Example 11 : the device of any of examples 1-10, wherein the one or more ramps inhibit unintended rotation of the elongated body within the wall tissue.

[0110] Example 12: the device of any of examples 1-11, wherein at least one second electrode of the one or more second electrodes wraps around an outer edge of the elongated housing.

[0111] Example 13: the device of any of examples 1-12, wherein at least one second electrode of the one or more second electrodes is disposed radially outwards of the elongated body and radially inwards of an outer edge of the elongated housing.

[0112] Example 14: the device of any of examples 1-13, wherein the proximal surface and the distal surface of at least one ramp of the one or more ramps are separated by a longitudinal distance of up to 1.5 millimeters (mm).

[0113] Example 15: the device of any of examples 1-14, wherein the one or more ramps comprises two or more ramps symmetrically distributed around the perimeter of the elongated housing.

[0114] Example 16: the device of any of examples 1-15, wherein the chamber of the heart comprises a first chamber of the heart, and wherein the elongated body is configured to penetrate into wall tissue of a second chamber of the heart that is separated from the first chamber of the heart.

[0115] Example 17: the device of example 16, wherein the first chamber comprises an atrium of the heart, and wherein the second chamber comprises a ventricle of the heart.

[0116] Example 18: a device comprising: a housing extending from a proximal end to a distal end along a longitudinal axis, the housing being configured to be implanted wholly within a chamber of a heart; and an elongated body extending distally from the distal end of the elongated housing and defining an electrode at or proximate a distal end of the elongated body; and wherein the housing defines one or more ramps, each ramp of the one or more ramps extending at least partially around a perimeter of the housing and along the longitudinal axis from a proximal surface to a distal surface, wherein the distal surface of each ramp of the one or more ramps defines at least a portion of the distal end of the housing.

[0117] Example 19: the device of example 18, wherein the device is configured to deliver conduction system pacing (CSP) signal to cardiac tissue via the electrode.

[0118] Example 20: the device of example 19, wherein the CSP signal comprises a left bundle branch area pacing (LBBAP) signal.

[0119] Example 21 : the device of any of examples 18-20, wherein the distal end of the housing has an annular shape defined by first and second radii, and the distal surface of each ramp of the one or more ramps spans the distance between the first radius and the second radius.

[0120] Example 22: the device of example 21, wherein the distal surface of each ramp of the one or more ramps forms an edge which is aligned with the first radius or the second radius,

[0121] Example 23: the device of example 21, wherein the distal surface of each ramp of the one or more ramps forms an edge which resides in a plane which is orthogonal to the longitudinal axis of the housing.

[0122] Example 24: the device of any of examples 18-23, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface and about the longitudinal axis in a first direction, wherein the elongated body defines a helix, and wherein the helix is wound about the longitudinal axis in a second direction, the second direction being the same as the first direction.

[0123] Example 25: the device of any of examples 18-23, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface and about the longitudinal axis in a first direction, wherein the elongated body defines a helix, and wherein the helix is wound about the longitudinal axis in a second direction, the second direction being opposite the first direction.

[0124] Example 26: the device of any of examples 18-25, wherein the one or more ramps comprises a first ramp and a second ramp, wherein the distal surface of the first ramp is circumferentially adjacent to the proximal surface of the second ramp, and wherein the distal surface of the first ramp is separated from the proximal surface of the second ramp by a ledge extending substantially along the longitudinal axis.

[0125] Example 27: the device of any of examples 18-26, wherein the one or more ramps inhibit unintended rotation of the elongated body within wall tissue of the chamber of the heart.

[0126] Example 28: the device of any of examples 18-27, wherein the proximal surface and the distal surface of at least one ramp of the one or more ramps are separated by a longitudinal distance of up to 1.5 millimeters (mm).

[0127] Example 29: the device of any of examples 18-28, wherein the one or more ramps comprises two or more ramps symmetrically distributed around the perimeter of the elongated housing.

[0128] Example 30: a device comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis, the elongated housing being configured to be implanted wholly within a chamber of a heart; an elongated body extending distally extending distally from the distal end of the elongated housing and defining a first electrode at or proximate a distal end of the elongated body; and one or more second electrodes disposed at or proximate the distal end of the elongated housing, wherein the one or more second electrodes are configured to contact wall tissue of the chamber without penetrating the wall tissue, and wherein each second electrode of the oneor more second electrodes wraps around an outer edge of a distal end of the elongated housing.

[0129] Example 31 : the device of example 30, wherein the distal end of the elongated housing has an annular shape defined by first and second radii, and the distal surface of each ramp of the one or more ramps spans the distance between the first radius and the second radius.

[0130] Example 32: the device of example 31, wherein the distal surface of each ramp of the one or more ramps forms an edge which is aligned with the first radius or the second radius.

[0131] Example 33: the device of example 31, wherein the distal surface of each ramp of the one or more ramps forms an edge which resides in a plane which is orthogonal to the longitudinal axis of the housing.

[0132] Example 34: the device of any of examples 30-33, wherein a distal surface of at least one second electrode of the one or more second electrodes is flush with the distal end of the elongated housing.

[0133] Example 35: the device of any of examples 30-33, wherein a distal surface of at least one second electrode of the one or more second electrodes is proud of the distal end of the elongated housing.

[0134] Example 36: the device of any of examples 30-35, wherein an outer surface of at least one second electrode of the one or more second electrodes is flush with the outer edge of the distal end of the elongated housing.

[0135] Example 37: the device of any of examples 30-36, wherein the one or more second electrodes comprises two or more second electrodes, wherein the two or more second electrodes are equally distributed around the perimeter of the elongated housing.

[0136] Example 38: the device of any of examples 30-37, wherein each second electrode of the one or more second electrodes defines an electrically active surface area of up to 6 square millimeters.

[0137] Example 39: the device of any of examples 30-38, wherein the chamber of the heart comprises a first chamber of the heart, and wherein the helix is configured to penetrate into wall tissue of a second chamber of the heart that is separated from the first chamber of the heart.

[0138] Example 40: the device of example 39, wherein the first chamber comprises an atrium of the heart, and wherein the second chamber comprises a ventricle of the heart.

[0139] Example 41 : a fixation device comprising: an elongated body extending distally from a distal end of an implantable medical device (IMD), the elongated body comprising a helix extending distally from the distal end of the IMD and defining one or more coils; and one or more ramps disposed at or proximate a distal portion of the IMD, each ramp of the one or more ramps extending at least partially around a perimeter of the IMD and along a longitudinal axis of the fixation device from a proximal surface to a distal surface, wherein the distal surface of each ramp of the one or more ramps defines at least a portion of the distal end of the IMD.

[0140] Example 42: the fixation device of example 41, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface in a first direction, wherein the helix is wound about the longitudinal axis in a second direction, the second direction being the same as the first direction.

[0141] Example 43: the fixation device of example 41, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface in a first direction, wherein the helix is wound about the longitudinal axis in a second direction, the second direction being opposite the first direction.

[0142] Example 44: the fixation device of any of examples 41-43, wherein the one or more ramps comprises a first ramp and a second ramp, wherein the distal surface of the first ramp is circumferentially adjacent to the proximal surface of the second ramp, and wherein the distal surface of the first ramp is separated from the proximal surface of the second ramp by a ledge extending substantially along the longitudinal axis.

[0143] Example 45: the fixation device of example 44, wherein the edge between the distal surface of the first ramp and the ledge is rounded.

[0144] Example 46: the fixation device of any of examples 41-45, wherein the one or more ramps are configured to inhibit unintended rotation of the helix within tissue.

[0145] Example 47: the device of any of examples 41-46, wherein the proximal surface and the distal surface of at least one ramp of the one or more ramps is separated by a longitudinal distance of up to 1.5 millimeters (mm).

[0146] Example 48: the device of any of examples 41-47, wherein the one or more ramps comprises two or more ramps symmetrically distributed around the perimeter of the IMD.

[0147] Example 49: a method comprising: forming an elongated housing of an implantable medical device configured to be implanted wholly within a chamber of a heart, the elongated housing extending from a proximal end to a distal end along a longitudinal axis; removing material from the elongated housing to define one or more ramps, wherein each ramp of the one or more ramps extends at least partially around a perimeter of the elongated housing and along the longitudinal axis from a proximal surface to a distal surface, and wherein the distal surface of each ramp of the one or more ramps defines at least a portion of the distal end of the elongated housing; affixing an elongated body to the distal end of the elongated housing, wherein the elongated body defines a first electrode at or proximate to a distal end of the elongated body; and affixing one or more second electrodes to the distal end of the elongated housing, wherein the one or more second electrodes are configured to contact wall tissue of the chamber without penetrating the wall tissue.

[0148] Example 50: the method of example 49, wherein the distal end of the elongated housing has an annular shape defined by first and second radii, and the distal surface of each ramp of the one or more ramps spans the distance between the first radius and the second radius.

[0149] Example 51 : the method of example 50, wherein the distal surface of each ramp of the one or more ramps forms an edge which is aligned with the first radius or the second radius.

[0150] Example 52: the method of example 50, wherein the distal surface of each ramp of the one or more ramps forms an edge which resides in a plane which is orthogonal to the longitudinal axis of the housing.

[0151] Example 53: the method of any of examples 49-52, wherein affixing the elongated body to the distal end of the elongated housing comprises affixing the elongated body to the distal end of the elongated housing and radially inwards of the one or more ramps.

[0152] Example 54: the method of any of examples 49-53, wherein the elongated housing comprises a proximal portion and a distal portion separate from the proximalportion, the distal portion defining the distal end of the elongated housing, and wherein the method further comprises: removing the material from the distal portion to define the one or more ramps; and affixing the distal portion to the proximal portion to define the elongated housing.

[0153] Example 55: the method of any of examples 49-54, wherein removing material from the elongated housing to define the one or more ramps comprises removing the material using one or more of: a laser ablation instrument; or a cutting instrument.

[0154] Example 56: the method of any of examples 49-55, wherein affixing the one or more second electrodes to the distal end of the elongated housing comprises: forming one or more recesses at or around the distal end of the elongated housing, and inserting each second electrode of the one or more second electrodes into a corresponding recess of the one or more recesses.

[0155] Example 57: the method of any of examples 49-56, wherein affixing the one or more second electrodes to the distal end of the elongated housing comprises affixing at least one second electrode of the one or more second electrodes on the distal surface of at least one ramp of the one or more ramps.

[0156] Example 58: the method of any of examples 49-57, wherein affixing the one or more second electrodes to the distal end of the elongated housing comprises affixing at least one second electrode of the one or more second electrodes on the proximal surface of at least one ramp of the one or more ramps.

[0157] Example 59: the method of any of examples 49-58, wherein affixing the one or more second electrodes to the distal end of the elongated housing comprises affixing at least one second electrode of the one or more second electrodes on an outer surface of and between the proximal surface and the distal surface of at least one ramp of the one or more ramps.

[0158] Example 60: the method of any of examples 49-59, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface and about the longitudinal axis in a first direction, wherein the elongated body defines a helix, and wherein the helix is wound about the longitudinal axis in a second direction, the second direction being the same as the first direction.

[0159] Example 61 : the method of any of examples 49-60, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface and about thelongitudinal axis in a first direction, wherein the elongated body defines a helix, and wherein the helix is wound about the longitudinal axis in a second direction, the second direction being opposite the first direction.

[0160] Example 62: the method of any of examples 49-61, wherein the one or more ramps comprises a first ramp and a second ramp, wherein the distal surface of the first ramp is circumferentially adjacent to the proximal surface of the second ramp, and wherein the distal surface of the first ramp is separated from the proximal surface of the second ramp by a ledge extending substantially along the longitudinal axis.

[0161] Example 63: the method of any of examples 49-62, wherein affixing the one or more second electrodes to the distal end of the elongated housing comprises wrapping at least one second electrode of the one or more second electrodes around an outer edge of the elongated housing.

[0162] Example 64: the method of any of examples 49-63, wherein affixing the one or more second electrodes to the distal end of the elongated housing comprises disposing at least one second electrode of the one or more second electrodes radially outwards of the elongated body and radially inwards of an outer edge of the elongated housing.

[0163] Example 65: the method of any of examples 49-64, wherein the proximal surface and the distal surface of at least one ramp of the one or more ramps is separated by a longitudinal distance of up to 1 millimeter (mm).

[0164] Example 66: the method of any of examples 49-65, wherein the one or more ramps comprises two or more ramps symmetrically distributed around the perimeter of the elongated housing.

[0165] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A device comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis, the elongated housing being configured to be implanted wholly within a chamber of a heart; an elongated body extending distally from the distal end of the elongated housing and defining a first electrode at or proximate a distal end of the elongated body; and one or more second electrodes disposed at or proximate the distal end of the elongated housing, wherein the one or more second electrodes are configured to contact wall tissue of the chamber without penetrating the wall tissue, wherein the elongated housing defines one or more ramps, each ramp of the one or more ramps extending at least partially around a perimeter of the elongated housing and along the longitudinal axis from a proximal surface to a distal surface, wherein the distal surface of each ramp of the one or more ramps defines at least a portion of the distal end of the elongated housing.

2. The device of claim 1, wherein the distal end of the elongated housing has an annular shape defined by first and second radii, and the distal surface of each ramp of the one or more ramps spans the distance between the first radius and the second radius.

3. The device of claim 2, wherein the distal surface of each ramp of the one or more ramps forms an edge which is aligned with the first radius or the second radius.

4. The device of claim 2, wherein the distal surface of each ramp of the one or more ramps forms an edge which resides in a plane which is orthogonal to the longitudinal axis of the elongated housing.

5. The device of any of claims 1-4, wherein at least one second electrode of the one or more second electrodes are disposed on the distal surface of at least one ramp of the one or more ramps.

6. The device of any of claims 1-5, wherein at least one second electrode of the one or more second electrodes are disposed on the proximal surface of at least one ramp of the one or more ramps.

7. The device of any of claims 1-6, wherein at least one second electrode of the one or more second electrodes are disposed on an outer surface of and between the proximal surface and the distal surface of at least one ramp of the one or more ramps.

8. The device of any of claims 1-7, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface and about the longitudinal axis in a first direction, wherein the elongated body defines a helix, and wherein the helix is wound about the longitudinal axis in a second direction, the second direction being the same as the first direction.

9. The device of any of claims 1-7, wherein each ramp of the one or more ramps extends from the proximal surface to the distal surface and about the longitudinal axis in a first direction, wherein the elongated body defines a helix, and wherein the helix is wound about the longitudinal axis in a second direction, the second direction being opposite the first direction.

10. The device of any of claims 1-9, wherein the one or more ramps comprises a first ramp and a second ramp, wherein the distal surface of the first ramp is circumferentially adjacent to the proximal surface of the second ramp, and wherein the distal surface of the first ramp is separated from the proximal surface of the second ramp by a ledge extending substantially along the longitudinal axis.

11. The device of any of claims 1-10, wherein at least one second electrode of the one or more second electrodes wraps around an outer edge of the elongated housing.

12. The device of any of claims 1-11, wherein at least one second electrode of the one or more second electrodes is disposed radially outwards of the elongated body and radially inwards of an outer edge of the elongated housing.

13. The device of any of claims 1-12, wherein the proximal surface and the distal surface of at least one ramp of the one or more ramps are separated by a longitudinal distance of up to 1.5 millimeters (mm).

14. The device of any of claims 1-13, wherein the chamber of the heart comprises a first chamber of the heart, and wherein the elongated body is configured to penetrate into wall tissue of a second chamber of the heart that is separated from the first chamber of the heart.

15. The device of claim 14, wherein the first chamber comprises an atrium of the heart, and wherein the second chamber comprises a ventricle of the heart.

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