Surface features for implantable medical device

Abstract

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; a first electrode extending distally from the distal end of the elongated housing, the first electrode comprising an elongated body defining a helix; a second electrode disposed on the distal end of the elongated housing, wherein the second electrode is configured to contact wall tissue of the chamber without penetrating the wall tissue; and one or more fixation features disposed on or about the distal end of the elongated housing, each fixation feature of the one or more fixation features defining a textured outer surface configured to interface with the wall tissue of the chamber to inhibit unintended movement of the elongated housing relative the wall tissue.

Description

SURFACE FEATURES FOR IMPLANTABLE MEDICAL DEVICE

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 669,342, filed July 10, 2024, the entire content of which is incorporated herein by reference.TECHNICAL FIELD

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

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

[0004] A cardiac pacemaker is an IMD configured to deliver cardiac pacing therapy to restore a more normal heart rhythm. Such IMDs 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 a compliant 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. This disclosure describes fixation features disposed on one or more outer surfaces of the IMD (e.g., around an outer perimeter of the IMD, on a face of IMD at or around the distal end of the IMD). The fixation features may define textured outer surfaces which may interface with surfaces of the cardiac tissue to adhere one or more outer surfaces of the IMD to the cardiac tissue, e.g., to inhibit unintended movement and / or rotation of the IMD relative to the cardiac tissue. The textured outer surface may define a plurality of protrusions and / or indentations. The protrusions and / or indentations may be macroscopic, microscopic, or nanoscopic.

[0008] 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; a first electrode extending distally from the distal end of the elongated housing, the first electrode comprising an elongated body defining a helix; a second electrode disposed on the distal end of the elongated housing, wherein the second electrode is configured to contact wall tissue of the chamber without penetrating the wall tissue; and one or more fixation features disposed on or about the distal end of the elongated housing, each fixation feature of the one or more fixation features defining a textured outer surface configured to interface with the wall tissue of the chamber to inhibit unintended movement of the elongated housing relative the wall tissue.

[0009] 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, the elongated body comprising: a proximal end located at the distal end of the implantable medical device; and a helix extending distally from the proximal end and defining one or more coils, wherein a distal end of the helix is configured to penetrate into tissue of a patient; and one or more fixation features disposed on or about a distal portion of the implantable medical device, each fixation feature of the one or more fixation features defining a textured outer surface configured to interface with the tissue to inhibit unintended movement of the elongated body relative to the tissue.

[0010] In some examples, this disclosure is directed to a method comprising: inserting a device into a chamber of a heart, the device comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis; a first electrode extending distally from the distal end of the elongated housing, the first electrode comprising an elongated body defining a helix; a second electrode disposed on the distal end of the elongated housing; and one or more fixation features disposed on or about the distal end of the elongated housing, each fixation feature of the one or more fixation features defining a textured outer surface; advancing the first electrode to penetrate wall tissue of the chamber; placing the second electrode and the one or more fixation features in contact with the wall tissue of the chamber, wherein when the one or more fixation features contact the wall tissue, the one or more fixation features inhibit unintended movement of the device relative to the wall tissue; and delivering cardiac pacing from the device to the wall tissue via at least one of the first electrode or the second electrode.

[0011] 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

[0012] 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.

[0013] 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.

[0014] FIG. 2A is a perspective diagram illustrating an example configuration of the device of FIG. 1 with an example fixation feature.

[0015] FIG. 2B is a perspective diagram illustrating an example configuration of the device of FIG. 1 with another example fixation feature.

[0016] FIG. 2C is a perspective diagram illustrating an example configuration of the device of FIG. 1 with another example fixation feature.

[0017] FIG. 3 A is a perspective diagram illustrating the example fixation feature of FIG. 2A.

[0018] FIG. 3B is a perspective diagram illustrating the example fixation feature of FIG. 2B.

[0019] FIG. 3C is a perspective diagram illustrating the example fixation feature of FIG. 2C.

[0020] FIG. 4A is a perspective diagram illustrating a macroscopic view of the textured surface of the fixation feature of any of FIGS. 2A-3C.

[0021] FIG. 4B is a perspective diagram illustrating a microscopic view of the textured surface of FIG. 4 A.

[0022] FIG. 4C is a perspective diagram illustrating a nanoscopic view of the textured surface of FIG. 4 A.

[0023] FIG. 5 is a block diagram illustrating an example configuration of an example device of any of FIGS. 1-2C.

[0024] FIG. 6 is a conceptual diagram of an example device of any of FIGS. 1-5 implanted at a target implant site.

[0025] FIG. 7 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. 1-6.DETAILED DESCRIPTION

[0026] 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.

[0027] 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.

[0028] Device 104 includes a distal end 110 and a proximal end 116. Distal end 110 includes a first electrode 112, and a second electrode 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 contact the wall tissue of the first chamber as first electrode 112 penetrates the wall tissue of the first chamber. When device 104 is affixed to the wall tissue of the first chamber, second electrode 114 may atleast partially elastically deform (e.g., compress) to place an electrically active region of second electrode 114 in contact with the wall tissue (e.g., without puncturing or penetrating the wall tissue). The compression of second electrode 114 may inhibit unintended rotation of first electrode 112 within the wall tissue. An amount of compression of second electrode 114 may be based on one or more parameters including, but are not limited to, a compliance of second electrode 114, a target implantation depth for first electrode 112, or an implantation angle of device 104 relative to a surface of the wall tissue.

[0029] 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 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. In some examples, first electrode 112 extends into the tissue of heart 102 at region 106 and affix device 104 to the tissue of heart 102.

[0030] FIG. 2A is a perspective diagram illustrating device 104A with example fixation feature 212A. Device 104A may be an example of device 104. Device 104A may include a housing 202 extending from a distal end 204 to a proximal end 206 along longitudinal axis 210. First electrode 112 and second electrode 114 may extend distally from distal end 204 of housing 202. Fixation feature 212A may define a band extending at least partially around the outer perimeter of housing 202.

[0031] Housing 202 may define a hermetically sealed internal cavity. Housing 202 may be formed from a conductive material including titanium or titanium alloy, stainlesssteel, 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.

[0032] 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 104A. 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.

[0033] Face 205 may define a distal end of housing 202. Electrodes 112 and 114 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. Second electrode 114 may be disposed on face 205. Second electrode 114 may be disposed radially outwards of first electrode 112 and radially inwards of or even with an outer perimeter of face 205. Second electrode 114 may include, but is not limited to, a button electrode, a ring electrode, or a spring electrode. A distal surface (e.g., a second electrically active region 217) of second electrode 114 may be proud of (e.g., extending distally of or located distal of) face 205 or may be flush with face 205.

[0034] First electrode 112 may include one or more coatings (e.g., electrically insulative coating(s)) configured to define a first electrically active region 216, or first electrode 112 may otherwise define first electrically active region 216. 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. Second electrode 114 may include one or more coatingsconfigured to define a second electrically active region 217 on an outer surface of second electrode 114.

[0035] 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 or Nitinol), 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, or other 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. 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 104A.

[0036] Fixation feature 212A may be disposed around an outer surface of housing 202. Fixation feature 212A may define an annular structure (e.g., a band) disposed around the outer surface of housing 202, e.g., along an outer perimeter of housing 202. Fixation feature 212A may be formed from, but is not limited to, titanium. Fixation feature 212A may define a textured outer surface. The textured outer surface may define a plurality of protrusions and / or a plurality of recesses which may interface with tissue surface to increase adherence of the outer surface of housing 202 to the tissue surface. In some examples, fixation feature 212A includes a steroid and / or an anti-inflammatory substance disposed on the fixation feature 212A, e.g., to reduce inflammation of tissue at or around the interface between the tissue surface and fixation feature 212A. Fixation feature 212A may be electrically isolated from one or more of first electrode 112, second electrode 114 electrode 218, and / or one or more other components within housing 202.

[0037] Fixation feature 212A may be a single continuous band or may be defined by two or more separate elements which may be arranged along housing 202 to collectively define fixation feature 212A. Housing 202 may define a groove along the outer surface of housing 202. The groove may be sized to retain fixation feature 212A. When fixation feature 212A is disposed within the groove, the outer surface of fixation feature 212A maybe flush with or proud of (e.g., extending radially beyond or located radially outward of) an outer perimeter of housing 202.

[0038] In some examples, first and second electrodes 112 and 114 include an electrically conducting material coating on first and second electrically active regions 216 and 217 to define the active regions. For example, first and second electrically active regions 216 and 217 may be coated with titanium nitride (TiN). First and second electrodes 112 and 114 may be made of substantially similar material or may be made of different material from one another.

[0039] 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.

[0040] 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 the tissue. 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.

[0041] First and second electrodes 112 and 114 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 aflatter 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.

[0042] 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.

[0043] 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 may have flexibility in lateral directions, being non-rigid to allow some flexing with heart motion. In a relaxed state, when not subjected to any external forces, first electrode 112 can be configured to maintain a distance between first electrically active region 216 and housing distal end 204.

[0044] Distal end of first electrode 112 can pierce into and / or 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 104A 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 offirst electrode 112 when first electrode 112 is a helix electrode. The spacing may be a predetermined 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.

[0045] As first electrode 112 enters tissue, second electrode 114 may at least partially contact a surface of the tissue. Second electrode 114 may interface with the surface of the tissue without penetrating the surface of the tissue. Second electrode 114 may sense signals from and / or deliver cardiac pacing signals to the tissue surface. As first electrode 112 enters tissue, at least a portion of fixation feature 212A may be placed into contact with the tissue surface and may interface with the tissue surface to inhibit unintended movement of device 104A relative to the tissue surface.

[0046] 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.

[0047] 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.

[0048] 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 atitanium, platinum, stainless steel, alloys thereof, a conductive material may be applied to one or more discrete areas of housing 202 to form electrode 218.

[0049] 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.

[0050] In some examples, second electrode 114 or electrode 218 is paired with first electrode 112 for sensing ventricular signals and delivering ventricular pacing pulses. In some examples, second electrode 114 is 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 218 is paired, at different times, with first electrode 112 and / or second electrode 114 for either ventricular or atrial functionality, respectively. In some examples, first and second electrodes 112 and 114 are paired with each other, with different polarities, for atrial and ventricular functionality.

[0051] In some examples, second electrode 114 is configured as an atrial cathode electrode for delivering pacing pulses to the atrial tissue, e.g., at target implant region 106 in combination with electrode 218. Second electrode 114 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.

[0052] A distal end of first electrode 112 can be configured to rest within a ventricular myocardium of the patient, and second electrode 114 can be configured to contact an atrial endocardium of the patient without penetration of the atrial endocardium. Alternatively, the distal end of first electrode 112 can be configured to rest within an interventricular septum of a patient so as to establish selective or non-selective capture of (e.g., electrical connection with) a conduction system of the patient, e.g., the left bundle branch (in whichcase second electrode(s) 114 may be omitted if device 104A is intended for placement in one of the ventricles and pacing the ventricles only). Device 104A may include more or fewer electrodes than two electrodes. In some examples, device 104A includes one or more second electrodes 114 along housing distal end 204. For example, device 104A may include two or three electrodes configured for atrial functionality like second electrode 114, and the three electrodes may be substantially similar or different from one another. Spacing between a plurality of second electrodes 114 may be at an equal or unequal distance. Second electrode(s) 114 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, device 104 A only includes first electrode 112 and electrode 218 and does not include any second electrodes 114.

[0053] 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 104A. 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.

[0054] FIG. 2B is a perspective diagram illustrating an example configuration of device 104B with another example fixation feature 212B. FIG. 2C is a perspective diagram illustrating an example configuration of device 104C with other example fixation features 212C. Each of devices 104B, 104C may be an example of device 104. Devices 104B, 104C illustrated in FIGS. 2B and 2C may each be substantially similar to device 104 A illustrated in FIG. 2 A, aside from the difference described below. While FIG. 2B shows device 104B with fixation features 212A and 212B and FIG. 2C shows device 104Cwith fixation features 212A and 212C, examples of devices 104 described herein may include one or more of fixation features 212A, 212B, or 212C in any combination.

[0055] Fixation feature 212B may be an elongated strip disposed on face 205. Fixation feature 212B may be disposed radially inwards of or even with 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.

[0056] The elongated body of fixation feature 212B may define a horseshoe shape, a C-shape, a V-shape, or the like. Fixation feature 212B may be a single, continuous elongated body or may be defined by two or more separate elements. A therapeutic substance, e.g., as previously described herein, may be disposed on an outer surface of fixation feature 212B.

[0057] Fixation feature 212C may be one or more buttons disposed on face 205. The outer surfaces of the one or more buttons may be proud of or flush with face 205. Fixation feature 212C may be disposed radially inwards of or even with an outer perimeter of housing 202 and may be disposed radially outwards of first electrode 112. Fixation feature 212C may be radially and / or circumferentially offset from second electrode 114. Each button of fixation feature 212C 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. A therapeutic substance, e.g., as previously described herein, may be disposed on an outer surface of each button of fixation feature 212C.

[0058] FIG. 3A is a perspective diagram illustrating fixation feature 212A. FIG. 3B is a perspective diagram illustrating fixation feature 212B. FIG. 3C is a perspective diagram illustrating example fixation feature 212C. Unless described otherwise, fixation features 212A, 212B, and 212C (collectively referred to herein as “fixation features 212”) may be formed from substantially similar materials (e.g., titanium) and may define outer surfaces with substantially similar textures.

[0059] Fixation feature 212A may define an elongated band, which may define an outer surface 302 and an inner surface 304. Outer surface 302 may define a textured outersurface and may be configured to be placed in contact with tissue (e.g., cardiac tissue). Inner surface 304 may be placed in contact with housing 202, e.g., to affix fixation feature 212A to housing 202 (e.g., within a groove in housing 202). In some examples, one or more attachment features (e.g., protrusions, recesses) are disposed on inner surface 304. The one or more attachment features may interface with corresponding elements on housing 202 (e.g., within the groove on housing 202) to affix fixation feature 212A to housing 202. In some examples, an adhesive is disposed on inner surface 304 to affix fixation feature 212A to housing 202. The elongated band may be a single, continuous band, as illustrated in FIG. 3 A, or may be defined by two or more separate elements which may be combined to define the elongated band.

[0060] Fixation feature 212B may define an elongated strip 306 extending from a first end 308A to a second end 308B. Elongated strip 306 may define an outer surface 310. Outer surface 310 may define a textured outer surface and may be configured to interface with tissue. Fixation feature 212B may be affixed to face 205 of housing 202 via one or more attachment features and / or adhesives disposed on an inner surface of fixation feature 212B (not pictured in FIG. 3B) opposite outer surface 310. Outer surface 310 may define a surface area less than, greater than, or similar to the surface area of outer surface 302 of fixation feature 212A.

[0061] Fixation feature 212C may include one or more buttons 311. Button 311 may include a distal portion 312 and a proximal portion 314 connected to distal portion 312. Distal portion 312 may, when affixed to housing 202, be flush with or proud of face 205 of housing 202. Distal portion 312 may define an outer surface 316. Outer surface 316 may be placed to be flush with or proud of face 205. Outer surface 316 may define a textured surface and may be configured to interface with tissue.

[0062] Proximal portion 314 may be configured to affix button 311 to housing 202. Proximal portion 314 may be configured to be disposed within a recess in face 205 and may be configured to secure button 311 to housing 202, e.g., via press fit, via one or more attachment features on proximal portion 314, and / or via an adhesive disposed over an outer surface of proximal portion 314.

[0063] FIG. 4A is a perspective diagram illustrating a macroscopic view 402 of a textured surface 404 of the fixation feature of any of FIGS. 2A-3C (e.g., fixation features 212A-C). FIG. 4B is a perspective diagram illustrating a microscopic view 406 of texturedsurface 404. FIG. 4C is a perspective diagram illustrating a nanoscopic view 408 of textured surface 404.

[0064] As illustrated in FIGS. 4A-4C, a manufacturing process may form textured surface 404 on an outer surface of one or more fixation features 212 (e.g., on one or more of outer surface 302, outer surface 310, or of outer surface 316). The manufacturing process may form textured surface 404 via subtractive or additive manufacturing. For example, a surface (e.g. textured surface 404) of a fixation feature (e.g., any of fixation features 212A-C, or face 205 or any portion(s) of distal end 204 when configured for fixation) can be textured using processes such as laser etching, ion beam etching, neutral atom beam etching, 3D printing, injection molding around removable materials, or any combination of such processes. In one such embodiment, a textured surface comprises a laser textured polymer such as laser textured PEEK (poly ether ether ketone). Optionally, distal end 204 of housing 202 can be formed from a polymer such as PEEK (or any other suitable polymer, or a metal) and a distal end face of distal end 204 can comprise a laser textured surface. A polymeric distal end 204 of housing 202 can be implemented as a polymeric header coupled to a proximal portion of housing 202, which proximal portion can be formed from a different material, e.g. a metal such as titanium or stainless steel, or from a different polymer, etc. Once formed, textured surface 404 may define protrusions and / or recesses at one or more scales, e.g., as illustrated in macroscopic view 402, in microscopic view 406, and / or in nanoscopic view 408. For example, textured surface 404 may define protrusions and / or recesses at up to the nanometer level.

[0065] In some examples, e.g., at the micrometer level, textured surface 404 may define protrusions and / or recesses substantially similar to osteoclastic-sized features. The protrusions and / or recesses may increase an interface area between an outer surface of one or more fixation features 212 and a tissue surface, e.g., thereby inhibiting unintended movement of fixation features 212, and by extension device 104, relative to the tissue surface. Textured surface 404 may facilitate tissue ingrowth into textured surface 404 of fixation features 212, thereby increasing fixation of device 104 to the tissue. In some examples, textured surface 404 is substantially similar to the Titan nanoLOCK™ surface available from Medtronic pic. of Dublin, Ireland.

[0066] Textured surface 404 may be electrically insulated, e.g., coated with an electrically insulating material or be formed from an electrically insulating material. Insome example, In some examples, fixation features 212 electrically isolates textured surface 404 from electrodes and / or other electronic components of device 104.

[0067] FIG. 5 is a block diagram illustrating an example configuration of an example device 104 of any of FIGS. 1-2C. As illustrated in FIG. 5, device 104 include electrodes 112 and 114, which may be configured as described with respect to FIGS. 1-4C. In the example shown in FIGS. 1-2C, device 104 includes switch circuitry 502, sensing circuitry 504, signal generation circuitry 506, sensor(s) 508, processing circuitry 510, telemetry circuitry 512, memory 514, and power source 516. The various circuitry may be, or include, programmable or fixed function circuitry configured to perform the functions attributed to respective circuitry. Memory 514 may store computer-readable instructions that, when executed by processing circuitry 510, cause device 104 to perform various functions. Memory 514 may be a storage device or other non-transitory medium. The components of device 104 illustrated in FIGS. 1-2C may be housed within housing 202.

[0068] Signal generation circuitry 506 generates electrical stimulation signals, e.g., cardiac pacing pulses. Switch circuitry 502 is coupled to electrodes 112, 114, and 218 and may include one or more switch arrays, one or more multiplexers, one or more switches (e.g., a switch matrix or other collection of switches), one or more transistors, or other electrical circuitry. Switch circuitry 502 is configured to direct stimulation signals from signal generation circuitry 506 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 502 may couple first electrode 112, which has penetrated to wall tissue of a ventricle or the intraventricular septum, to signal generation circuitry 506 as a cathode, and one or both of second electrode 114 or electrode 218 to signal generation circuitry 506 as an anode. As another example, in order to pace the RA, switch circuitry 502 may couple second electrode 114, which maintains contact with the RA endocardium, to signal generation circuitry 506 as a cathode, and one or both of first electrode 112 or electrode 218 to signal generation circuitry 506 as an anode.

[0069] Each of electrodes 112, 114, 218 may be coupled to switch circuitry 502 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 isa 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.

[0070] Switch circuitry 502 may also selectively couple sensing circuitry 504 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 504 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 502 may couple each of first electrode 112 and second electrode 114 (in combination with electrode 218) to respective sensing channels provided by sensing circuitry 504 to respectively sense either ventricular or atrial cardiac electrical signals. In some examples, sensing circuitry 504 is configured to detect events, e.g., depolarizations, within the cardiac electrical signals, and provide indications thereof to processing circuitry 510. In this manner, processing circuitry 510 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 510 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 510 herein may be embodied as firmware, hardware, software or any combination thereof.

[0071] Sensor(s) 508 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) 508 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other types of sensors. Sensor(s) 508 may output patient parameter values that may be used as feedback to control sensing and delivery of therapy by device 104.

[0072] Telemetry circuitry 512 supports wireless communication between device 104 and an external programmer (not shown in FIG. 5) or another computing device under the control of processing circuitry 510. Processing circuitry 510 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 512. Telemetry circuitry 512 may accomplish communication by radiofrequency (RF) communication techniques, e.g., via an antenna (not shown).

[0073] Power source 516 delivers operating power to various components of device 104. Power source 516 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.

[0074] FIG. 6 is a conceptual diagram of device 104 of any of FIGS. 1-5 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 606 and central fibrous body 602 to position first electrically active region 216 in ventricular myocardium 108 as shown in FIG. 6. 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.

[0075] 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 606 and central fibrous body 602 to position first electrically active region 216 in ventricular myocardium 108 as shown in FIG. 6.

[0076] As first electrode 112 advances into the tissue, the distance between second electrode 114 and atrial endocardium 604 decreases until second electrode 114 contact, and may press against, the surface of atrial endocardium 604. Fixation features 212 (e.g., fixation features 212A, 212B as illustrated in FIG. 6) disposed on or around distal end 204of device 104 may contact and / or interface with atrial endocardium 604, e.g., to prevent or 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 606, central fibrous body 602, or the like) or blood flow during cardiac function. The interface between fixation features 212 and atrial endocardium 604 may be along face 205 at distal end 204 of device 104 and / or may be around an outer surface of housing 202 proximal to distal end 204.

[0077] Target implant region 106 in some pacing applications is along atrial endocardium 604, 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 or along the interventricular septum, in the case of a ventricular conduction system pacing (CSP) application of device 104. First electrode 112 can have a length that penetrates through atrial tissue 604 in target implant region 106, through the central fibrous body 602 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 604. 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).

[0078] FIG. 7 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.

[0079] A clinician may insert device 104 within a single first chamber of the heart 102 (702). 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 (704). 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.

[0080] 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 (706). The clinician may continue to advance first electrode 112 into the tissue until at least a portion of face 205 of distal end 204 of device 104 contacts the surface of the tissue. Once device 104 is implanted within the wall tissue, second electrode 114 and / or one or more fixation features 212 described herein may interface with the wall tissue to inhibit unintended movement of first electrode 112 out of the wall tissue. For example, textured surface 404 on an outer surface of one or more fixation features 212 may interface with the surface of the tissue, where the tissue may interface with macroscopic, microscopic, and / or nanoscopic features (e.g., protrusions and / or recesses) within textured surface 404 to increase adherence of device 104 to the tissue and inhibit unintended movement of device 104 (e.g., unintended rotation of first electrode 112) relative to the tissue.

[0081] 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 (708). 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).

[0082] It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the description and accompanying drawings. It should also be understood that, depending on the example,certain acts or events of any of the processes or methods described herein may be performed in a different sequence, may be added, merged, or left out altogether (e.g., all described acts or events may not be necessary to carry out the techniques). In addition, while certain aspects of this disclosure are described as being performed by a single module or unit for purposes of clarity, it should be understood that the techniques of this disclosure may be performed by a combination of units or modules associated with, for example, a medical device.

[0083] 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).

[0084] 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.

[0085] Instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Accordingly, the term “processor” as used herein may refer to any of the foregoing structure or any other physical structure suitable for implementation of the described techniques. Also, the techniques could be fully implemented in one or more circuits or logic elements.

[0086] This disclosure describes each of the following examples.

[0087] 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; a first electrode extending distally from the distal end of the elongated housing, the first electrode comprising anelongated body defining a helix; a second electrode disposed on the distal end of the elongated housing, wherein the second electrode is configured to contact wall tissue of the chamber without penetrating the wall tissue; and one or more fixation features disposed on or about the distal end of the elongated housing, each fixation feature of the one or more fixation features defining a textured outer surface configured to interface with the wall tissue of the chamber to inhibit unintended movement of the elongated housing relative the wall tissue.

[0088] Example 2: the device of example 1, wherein each fixation feature of the one or more fixation features is electrically isolated from the first electrode and the second electrode.

[0089] Example 3 : the device of any of examples 1 or 2, wherein the textured outer surface comprises titanium.

[0090] Example 4: the device of any of examples 1-3, wherein the textured outer surface defines microscopic features.

[0091] Example 5: the device of any of examples 1-4, wherein the textured outer surface defines a plurality of recesses and a plurality of protrusions.

[0092] Example 6: the device of any of claims 1-5, wherein the one or more fixation features comprises a band disposed around the distal end of the elongated housing and extending at least partially around an outer perimeter of the elongated housing.

[0093] Example 7: the device of example 6, wherein the elongated housing comprises a groove around the distal end of the elongated housing, and wherein the band is disposed within the groove.

[0094] Example 8: the device of example 7, wherein when the band is disposed within the groove, the textured outer surface is flush with an outer surface of the elongated housing.

[0095] Example 8.1 : the device of any of examples 1-8, wherein the textured outer surface comprises a laser textured material.

[0096] Example 8.2: the device of any of examples 1-2 or 4-8, wherein the distal end of the elongated housing comprises a polymeric header, and the textured outer surface comprises a laser textured polymeric material of the header.

[0097] Example 9: the device of any of examples 1-8, wherein the one or more fixation features comprises an elongated strip disposed on the distal end of the elongatedhousing, the elongated strip defining the textured outer surface on the distal end of the elongated housing.

[0098] Example 10: the device of example 9, wherein the elongated strip is circumferentially offset from the second electrode.

[0099] Example 11 : the device of any of examples 9 or 10, wherein the elongated strip is disposed radially outwards of the first electrode.

[0100] Example 12: the device of any of examples 9-11, wherein the elongated strip defines a horseshoe shape, a C-shape, or a V-shape.

[0101] Example 13: the device of any of examples 1-12, wherein the one or more fixation features comprises one or more buttons disposed on the distal end of the elongated housing, each button of the one or more buttons comprising: a distal portion configured to be disposed on the distal end of the elongated housing, the distal portion defining the textured outer surface; and a proximal portion coupled to the distal portion and configured to be disposed within and affixed to the elongated housing.

[0102] Example 14: the device of any of examples 1-13, 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.

[0103] Example 15: the device of example 14, wherein the first chamber comprises an atrium of the heart, and wherein the second chamber comprises a ventricle of the heart.

[0104] Example 16: a fixation device comprising: an elongated body extending distally from a distal end of an implantable medical device, the elongated body comprising: a proximal end located at the distal end of the implantable medical device; and a helix extending distally from the proximal end and defining one or more coils, wherein a distal end of the helix is configured to penetrate into tissue of a patient; and one or more fixation features disposed on or about a distal portion of the implantable medical device, each fixation feature of the one or more fixation features defining a textured outer surface configured to interface with the tissue to inhibit unintended movement of the elongated body relative to the tissue.

[0105] Example 17: the fixation device of example 16, wherein each fixation feature of the one or more fixation features is electrically isolated from one or more components within the implantable medical device.

[0106] Example 18: the fixation device of any of examples 16 or 17, wherein the textured outer surface comprises titanium.

[0107] Example 19: the fixation device of any of examples 16-18, wherein the textured outer surface defines microscopic features.

[0108] Example 20: the fixation device of any of examples 16-19, wherein the textured outer surface defines a plurality of recesses and a plurality of protrusions.

[0109] Example 21 : the fixation device of any of examples 16-20, wherein the one or more fixation features comprises a band disposed around the distal portion of the implantable medical device and extending at least partially around an outer perimeter of the distal portion of the implantable medical device.

[0110] Example 22: the fixation device of example 21, wherein band is configured to be disposed within a groove around the distal portion of the implantable medical device.

[0111] Example 23 : the fixation device of example 22, wherein when the band is disposed within the groove, the textured outer surface is flush with an outer surface of the distal portion of the implantable medical device.

[0112] Example 23.1 : the fixation device of any of examples 16-23, wherein the textured outer surface comprises a laser textured material.

[0113] Example 23.2: the fixation device of any of examples 16-17 or 19-23, wherein the distal end of the elongated housing comprises a polymeric header, and the textured outer surface comprises a laser textured polymeric material of the header.

[0114] Example 24: the fixation device of any of examples 16-23, wherein the one or more fixation features comprises an elongated strip disposed on the distal portion of the implantable medical device, the elongated strip defining the textured outer surface on the distal portion of the implantable medical device.

[0115] Example 25: the fixation device of example 24, wherein the elongated strip is disposed radially outwards of the elongated body.

[0116] Example 26: the fixation device of any of examples 24 or 25, wherein the elongated strip defines a horseshoe shape, a C-shape, or a V-shape.

[0117] Example 27: the fixation device of any of examples 16-26, wherein the one or more fixation features comprises one or more buttons disposed on the distal portion of the implantable medical device, each button of the one or more buttons comprising: a distal portion configured to be disposed on the distal portion of the implantable medical device,the distal portion defining the textured outer surface; and a proximal portion coupled to the distal portion and configured to be disposed within and affixed to the implantable medical device.

[0118] Example 28: a method comprising: inserting a device into a chamber of a heart, the device comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis; a first electrode extending distally from the distal end of the elongated housing, the first electrode comprising an elongated body defining a helix; a second electrode disposed on the distal end of the elongated housing; and one or more fixation features disposed on or about the distal end of the elongated housing, each fixation feature of the one or more fixation features defining a textured outer surface; advancing the first electrode to penetrate wall tissue of the chamber; placing the second electrode and the one or more fixation features in contact with the wall tissue of the chamber, wherein when the one or more fixation features contact the wall tissue, the one or more fixation features inhibit unintended movement of the device relative to the wall tissue; and delivering cardiac pacing from the device to the wall tissue via at least one of the first electrode or the second electrode.

[0119] Example 29: the method of example 28, wherein each fixation feature of the one or more fixation features is electrically isolated from the first electrode and the second electrode.

[0120] Example 30: the method of any of examples 28 or 29, wherein the textured outer surface comprises titanium.

[0121] Example 31 : the method of any of examples 28-30, wherein the textured outer surface defines microscopic features.

[0122] Example 32: the method of any of examples 28-31, wherein the textured outer surface defines a plurality of recesses and a plurality of protrusions.

[0123] Example 33: the method of any of examples 28-32, wherein the one or more fixation features comprises a band disposed around the distal end of the elongated housing and extending at least partially around an outer perimeter of the elongated housing.

[0124] Example 34: the method of example 33, wherein the elongated housing comprises a groove around the distal end of the elongated housing, and wherein the band is disposed within the groove.

[0125] Example 35: the method of example 34, wherein when the band is disposed within the groove, the textured outer surface is flush with an outer surface of the elongated housing.

[0126] Example 35.1 : the method of any of examples 28-35, wherein the textured outer surface comprises a laser textured material.

[0127] Example 35.2: the method of any of examples 28-29 or 31-35, wherein the distal end of the elongated housing comprises a polymeric header, and the textured outer surface comprises a laser textured polymeric material of the header.

[0128] Example 36: the method of any of examples 28-35, wherein the one or more fixation features comprises an elongated strip disposed on the distal end of the elongated housing, the elongated strip defining the textured outer surface on the distal end of the elongated housing.

[0129] Example 37: the method of example 36, wherein the elongated strip is circumferentially offset from the second electrode.

[0130] Example 38: the method of any of examples 36 or 37, wherein the elongated strip is disposed radially outwards of the first electrode.

[0131] Example 39: the method of any of examples 36-38, wherein the elongated strip defines a horseshoe shape a C-shape, or a V-shape.

[0132] Example 40: the method of any of examples 28-39, wherein the one or more fixation features comprises one or more buttons disposed on the distal end of the elongated housing, each button of the one or more buttons comprising: a distal portion configured to be disposed on the distal end of the elongated housing, the distal portion defining the textured outer surface; and a proximal portion coupled to the distal portion and configured to be disposed within and affixed to the elongated housing.

[0133] Example 41 : the method of any of examples 28-40, wherein the chamber of the heart comprises a first chamber of the heart, and advancing the first electrode to penetrate wall tissue of the chamber comprises advancing the first electrode through the wall tissue of the first chamber into wall tissue of a second chamber of the heart that is separated from the first chamber of the heart.

[0134] Example 42: the method of example 41, wherein the first chamber comprises an atrium of the heart, and wherein the second chamber comprises a ventricle of the heart.

[0135] 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; a first electrode extending distally from the distal end of the elongated housing, the first electrode comprising an elongated body defining a helix; a second electrode disposed on the distal end of the elongated housing, wherein the second electrode is configured to contact wall tissue of the chamber without penetrating the wall tissue; and one or more fixation features disposed on or about the distal end of the elongated housing, each fixation feature of the one or more fixation features defining a textured outer surface configured to interface with the wall tissue of the chamber to inhibit unintended movement of the elongated housing relative the wall tissue.

2. The device of claim 1, wherein each fixation feature of the one or more fixation features is electrically isolated from the first electrode and the second electrode.

3. The device of any of claims 1 or 2, wherein the textured outer surface comprises titanium.

4. The device of any of claims 1-3, wherein the textured outer surface defines microscopic features.

5. The device of any of claims 1-4, wherein the textured outer surface defines a plurality of recesses and a plurality of protrusions.

6. The device of any of claims 1-5, wherein the one or more fixation features comprises a band disposed around the distal end of the elongated housing and extending at least partially around an outer perimeter of the elongated housing.

7. The device of claim 6, wherein the elongated housing comprises a groove around the distal end of the elongated housing, and wherein the band is disposed within the groove.

8. The device of claim 7, wherein when the band is disposed within the groove, the textured outer surface is flush with an outer surface of the elongated housing.

9. The device of any of claims 1-8, wherein the textured outer surface comprises a laser textured material.

10. The device of any of claims 1-2 or 4-8, wherein the distal end of the elongated housing comprises a polymeric header, and the textured outer surface comprises a laser textured polymeric material of the header.

11. The device of any of claims 1-8, wherein the one or more fixation features comprises an elongated strip disposed on the distal end of the elongated housing, the elongated strip defining the textured outer surface on the distal end of the elongated housing.

12. The device of claim 11, wherein the elongated strip is circumferentially offset from the second electrode.

13. The device of any of claims 1-12, wherein the one or more fixation features comprises one or more buttons disposed on the distal end of the elongated housing, each button of the one or more buttons comprising: a distal portion configured to be disposed on the distal end of the elongated housing, the distal portion defining the textured outer surface; and a proximal portion coupled to the distal portion and configured to be disposed within and affixed to the elongated housing.

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 helix is configured to penetrateinto 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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