Fixation mechanism for implantable medical device

Abstract

A system comprising: an implantable medical device (IMD) 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; and an elongated body extending distally from the distal end of the elongated housing and defining a helix, the helix defining an electrode at or proximate a distal end of the helix; and a sheath disposed around a distal portion of the IMD, the sheath defining one or more tracks extending along a surface of the sheath, wherein the one or more tracks are configured to interface with the IMD to facilitate distal movement of the elongated body through the sheath and into wall tissue of the chamber in response to rotation of the IMD about the longitudinal axis.

Description

FIXATION MECHANISM FOR IMPLANTABLE MEDICAL DEVICE

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63 / 675,567, filed July 25, 2024, and U.S. Provisional Patent Application Serial No. 63 / 710,905, filed October 23, 2024, the entire contents of each are 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 cardiacpacemakers 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 a chamber of a heart of the patient and is able to sense signals from and / or deliver cardiac pacing to cardiac tissue of a chamber of the heart (e.g., the same chamber the IMD is implanted in, another chamber separate from the chamber the IMD is implanted in). In some examples, such an implantable medical device includes a distal electrode that is configured to penetrate through wall tissue of the heart chamber in which the device is implanted (e.g., and into wall tissue of another heart chamber). Depending on the position and / or orientation of a target implantation site within the chamber of the heart, the distal electrode may need to be implanted at different depths within the wall tissue, e.g., to position the distal electrode at a specific location and / or orientation within the wall tissue.

[0007] This disclosure describes devices, systems, and techniques for affixing the distal electrode of the IMD at varying depths within the wall tissue of the heart. The IMD may be coupled to a sheath around a distal end of the IMD. The sheath may include one or more features (e.g., one or more tracks, one or more recesses) configured to interface with a corresponding feature on the IMD (e.g., a helical shape of the distal electrode, one or more extensions on the outer surface of the IMD, one or more tines couples to the IMD) to allow longitudinal movement of the IMD within the sheath and towards the wall tissue in response to rotation of the IMD relative to the sheath. The sheath may allow for a varying implantation depth of the distal electrode of the IMD while providing a contact surface between the sheath and the wall tissue, e.g., to inhibit unintended movement and / or rotation of the IMD from the wall tissue.

[0008] In some examples, this disclosure is directed to a system comprising: an implantable medical device (IMD) comprising: an elongated housing extending from aproximal end to a distal end along a longitudinal axis, the elongated 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 a helix, the helix defining an electrode at or proximate a distal end of the helix; and a sheath disposed around a distal portion of the IMD, the sheath defining one or more tracks extending along a surface of the sheath, wherein the one or more tracks are configured to interface with the IMD to facilitate distal movement of the elongated body through the sheath and into wall tissue of the chamber in response to rotation of the IMD about the longitudinal axis.

[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 (IMD), the elongated body comprising: a helix extending distally from the distal end of the elongated body along a longitudinal axis and defining one or more coils, wherein a distal end of the helix is configured to penetrate into tissue of a patient; and a sheath disposed radially outwards of the elongated body, the sheath defining one or more tracks extending along a surface of the sheath, wherein the one or more tracks is configured to interface with the elongated body to facilitate distal movement of the elongated body through the sheath and into wall tissue of the chamber in response to rotation of the IMD about the longitudinal axis.

[0010] In some examples, this disclosure is directed to a system comprising: an implantable medical device (IMD) 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 helix, the helix defining an electrode at or proximate a distal end of the helix; a rotatable ring disposed on the distal end of the IMD, the rotatable ring being configured to freely rotate relative to the IMD; and one or more tines affixed to the rotatable ring and extending radially away from the longitudinal axis; and a sheath disposed around a distal portion of the IMD, the sheath extending along the longitudinal axis, wherein the elongated body is configured to be advanced distally through the sheath in response to rotation of the IMD about the longitudinal axis to penetrate wall tissue of the chamber, wherein the sheath is configured to retain the one or more tines in an undeployed configuration when the IMD is in a proximal position within the sheath, and wherein as the IMD advances distally withinthe sheath, the one or more tines advance out of a distal end of the sheath and transition from the undeployed configuration to a deployed configuration to penetrate the wall tissue.

[0011] In some examples, this disclosure is directed to a method comprising: inserting a distal portion of a medical device system within a chamber of a heart, the distal portion of the medical device system comprising: an implantable medical device (IMD) comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis; and an elongated body extending distally from the distal end of the elongated housing and defining a helix, the helix defining an electrode at or proximate a distal end of the helix; and a sheath disposed around a distal portion of the IMD, the sheath defining one or more tracks extending along a surface of the sheath; rotating the IMD about the longitudinal axis to advance the elongated body of the IMD through the one or more tracks of the sheath to advance the IMD distally through the sheath along the longitudinal axis and cause the elongated body to penetrate wall tissue of the chamber; and delivering cardiac pacing signals from the IMD to wall tissue of the chamber via the electrode.

[0012] In some examples, this disclosure is directed to a system comprising: a leadless pacemaker (LP) 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 a helix extending distally from the distal end of the housing, the helix defining an electrode at or proximate a distal end of the helix; and a sheath disposed around a distal portion of the LP and in threaded engagement with the distal portion of the LP, to facilitate distal movement of the helix through the sheath and into wall tissue of the chamber in response to rotation of the LP about the longitudinal axis.

[0013] In some examples, this disclosure is directed to a system comprising: an implantable medical device (IMD) 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; 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 a sheath disposed around a distal portion of the IMD, the sheath defining: an inner volume configured to receive the distal portion of the IMD; a distal surface, wherein at least a portion of the distal surface extends along a reference plane offset from the longitudinal axis; and an opening extending fromthe distal surface to the inner volume, wherein when the IMD is rotated relative to the sheath, the elongated body moves relative to the sheath through the opening and along a reference axis offset from the longitudinal axis to penetrate tissue of the chamber of the heart.

[0014] 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) along a longitudinal axis; and a sheath disposed around a distal portion of the IMD, the sheath defining: an inner volume configured to receive the distal portion of the IMD; a distal surface, wherein at least a portion of the distal surface extends along a reference plane offset from the longitudinal axis; and an opening extending from the distal surface to the inner volume, wherein when the IMD is rotated relative to the sheath, a distal end of the elongated body moves relative to the sheath through the opening along a reference axis offset from the longitudinal axis and penetrates tissue of a patient.

[0015] In some examples, this disclosure is directed to a system comprising: a leadless pacemaker (LP) 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 housing, the elongated body defining an electrode at or proximate a distal end of the elongated body; and a sheath disposed around a distal portion of the LP, the sheath defining: an inner volume configured to receive the distal portion of the LP; a distal surface, wherein at least a portion of the distal surface extends along a reference plane offset from the longitudinal axis; and an opening extending from the distal surface to the inner volume, wherein when the LP is rotated relative to the sheath, the distal end of the elongated body moves relative to the sheath through the opening along a reference axis offset from the longitudinal axis to penetrate tissue of the chamber of the heart.

[0016] In some examples, this disclosure is directed to a system comprising: an implantable medical device (IMD) 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 fixation feature disposed on the distal end of the IMD, the fixation feature being configured to affix the distal end of the elongated housing to wall tissue of the chamber of the heart; and an elongated body disposed within the elongated housing around the proximal end of the elongated housing,wherein the elongated body defines an electrode at or proximate to a distal end of the elongated body, wherein in response to rotation of the elongated housing about the longitudinal axis, the elongated body is configured to extend out of the elongated housing and penetrate the wall tissue.

[0017] In some examples, this disclosure is directed to a method comprising: inserting an implantable medical device (IMD) within a chamber of a heart, the IMD comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis; a fixation feature disposed on the distal end of the IMD; and an elongated body disposed within the elongated housing around the proximal end of the elongated housing, wherein the elongated body defines an electrode at or proximate to a distal end of the elongated body, affixing the fixation feature of the IMD to wall tissue of the chamber; rotating the elongated housing of the IMD about the longitudinal axis to advance the elongated body out of the elongated housing and cause the distal end of the elongated body to penetrate the wall tissue; and delivering cardiac pacing signals from the IMD to the wall tissue via the electrode.

[0018] 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

[0019] 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.

[0020] 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.

[0021] FIG. 2 is a perspective diagram illustrating an example configuration of the device of FIG. 1.

[0022] FIG. 3 A is a perspective diagram illustrating an example medical device assembly including the device of FIG. 2.

[0023] FIG. 3B is a cross-sectional diagram illustrating an example cross-sectional view of the medical device assembly of FIG. 3 A, the cross-section being taken along the longitudinal axis of the medical device assembly.

[0024] FIG. 4A is a perspective diagram illustrating a partially exploded view of the example medical device assembly of FIG. 3 A.

[0025] FIG. 4B is a cross-sectional diagram illustrating an example cross-sectional view of the partially exploded medical device assembly of FIG. 4 A, the cross-section being taken along the longitudinal axis of the medical device assembly.

[0026] FIG. 5 is a perspective diagram illustrating a side view of another example medical device assembly including the device of FIG. 2.

[0027] FIG. 6 is a cross-sectional diagram illustrating an example partial cross- sectional view of another example medical device assembly, the cross-section being taken along the longitudinal axis of the medical device assembly.

[0028] FIG. 7A is a cross-sectional diagram illustrating an example partial cross- sectional view of another example medical device assembly, the cross-section being taken along the longitudinal axis of the medical device assembly.

[0029] FIG. 7B is a perspective diagram illustrating a top view of the example medical device assembly of FIG. 7A.

[0030] FIG. 8 is a block diagram illustrating an example configuration of an example device of any of FIGS. 1-7B.

[0031] FIG. 9 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. 1-8.

[0032] FIG. 10 is a perspective diagram illustrating an example configuration of the device of FIG. 1.

[0033] FIG. 11 A is a perspective diagram illustrating an example fixation feature of the device of FIG. 10.

[0034] FIG. 1 IB is a perspective diagram illustrating another example fixation feature of the device of FIG. 10.

[0035] FIG. 11C is a perspective diagram illustrating another example fixation feature of the device of FIG. 10.

[0036] FIG. 1 ID is a perspective diagram illustrating another example fixation feature of the device of FIG. 10.

[0037] FIG. 12 is a flowchart illustrating an example process for delivering cardiac pacing therapy to the heart of the patient via an example device of any of FIGS. 10-1 ID.

[0038] FIG. 13 is a perspective diagram illustrating an example medical device assembly including an example device of FIG. 1.

[0039] FIG. 14 is a perspective diagram illustrating an example sheath of the medical device assembly of FIG. 13.

[0040] FIG. 15 is a cross-sectional diagram illustrating an example partial cross- sectional view of the example medical device assembly of FIG. 13, the cross-section being taken along the longitudinal axis of the medical device assembly.DETAILED DESCRIPTION

[0041] In general, this disclosure is directed to distal end configurations for implantable medical devices (IMDs). More particularly, this disclosure is directed to IMDs, such as leadless pacemakers (LPs), with an elongated body extending distally from the distal end of the IMD. The IMD may be coupled to a sheath disposed around the distal end of the IMD. The sheath may interface with corresponding features on the IMD to control the distal movement of the IMD during implantation, e.g., thereby controlling an implantation depth of the elongated body within tissue of a patient (e.g., within cardiac tissue of the patient).

[0042] 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 ventricle (RV) of the patient’s heart 102 in a target implant region 106 in heart 102 of the patient with a distal end of device 104 directed toward the left ventricle (LV) of the patient’s heart 102. Although in the example of FIG. 1 the distal end of device 104 is directed toward the LV, the distal end may be directed to other targets, such as interventricular septum of heart 102. In some examples, target implant region 106 may be disposed in another position within heart 102, e.g., within a right atrium (RA) of heart 102. In some examples (not pictured in FIG. 1), target implant region 106 may be located at or around the Bachmann’s bundle of heart 102and / or a septal wall of the RA of heart 102. In such examples, the variable implantation depth of device 104, as described in greater detail below, may increase a range of possible target implant regions 106 for device 104. The variable implantation depth of device 104 may also provide for increased adaptability of device 104 to the varying anatomies of hearts 102 of different patients.

[0043] Device 104 includes a distal end 110 and a proximal end 116. Distal end 110 includes a distal electrode 112. Distal electrode 112 may be disposed along an elongated body extending to a distal end. In such examples, distal electrode 112 may be disposed along the elongated body at a position proximal to the distal end of the elongated body. The elongated body may define a helical shape, an elongated barb, or any other elongated shape. Distal electrode 112 may define the entire elongated body and an electrically active region of distal electrode 112 may be disposed at or proximal to the distal end of the elongated body.

[0044] The elongated body and distal electrode 112 extends from distal end 110 and may penetrate into the wall tissue of a chamber of heart 102 (e.g., the RV of heart 102). Distal electrode 112 may penetrate through the wall tissue of a first chamber (e.g., RV) and into wall tissue of a second chamber (e.g., LV). For example, a portion of distal electrode 112 may penetrate through cardiac tissue and be disposed at or around a left bundle branch (LBB) of heart 102.

[0045] Depending on the location of target implantation region 106 and / or a position of target cardiac tissue, the implantation depth for distal electrode 112 may vary. Device 104 may be coupled to a sheath disposed at or around distal end 110 of device 104. The sheath may define one or more tracks or other features configured to interface with corresponding features on device 104 (e.g., with distal electrode 112, with one or more other features on an outer surface of device 104) to control a distal movement of distal electrode 112 into or out of the tissue at or around target implant region 106. In some examples, the sheath may translate (e.g., via the one or more tracks or other features) a rotation of device 104 about a longitudinal axis into a longitudinal movement of distal electrode 112 along the longitudinal axis, e.g., thereby providing fine-grain control over the longitudinal movement and / or implantation depth of distal electrode 112. The sheath may provide increased implantation orientations and / or positions for device 104 withoutrequiring modification of device 104 (e.g., without requiring modification of distal electrode 112), thereby increasing the number of possible use cases for device 104.

[0046] The configuration of distal electrode 112 illustrated in FIG. 1 allows device 104 to sense cardiac signals and / or deliver cardiac pacing to one or more chambers of heart 102, e.g., the RV, LV, and / or the conduction system of either or both in the illustrated example. In this manner, the configuration of distal electrode 112 may facilitate the delivery of pacing by single device 104 implanted within the single chamber, e.g., the RV. While device 104 is implanted at target implant region 106 to sense in and / or pace the ventricle(s) in the example shown in FIG. 1, a device having an electrode configuration in accordance with the examples of this disclosure may be implanted at any of a variety of locations to sense in and / or pace any one, two or more chambers of heart 102. For example, device 104 may be implanted at region 106 or another region, and distal electrode 112 may extend into tissue, e.g., myocardial tissue, of the LV or interventricular septum. Furthermore, a device having an electrode configuration in accordance with the examples of this disclosure may be implanted at any of a variety of locations within a patient for sensing and / or delivery of therapy to other patient tissue, e.g., outside of heart 102.

[0047] FIG. 2 is a perspective diagram illustrating an example configuration of the device of FIG. 1. Device 104 A may be an example of device 104 of FIG. 1 and may be substantially similar to device 104 described with respect to FIG. 1 aside from the elements described below. Device 104 A may include a housing 202 extending from a distal end 204 to a proximal end 206 along longitudinal axis 201. Housing 202 may optionally be elongated; however, any other suitable form or shape may be employed for housing 202. Distal electrode 112A may extend distally from distal end 204 of housing 202 and along longitudinal axis 201. While FIG. 2 illustrates distal electrode 112A as an elongated helix, other example devices 104 may include distal electrode 112A defining an elongated barb or other elongated body. Distal electrode 112A may be an example of distal electrode 112 illustrated in FIG. 1.

[0048] 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.

[0049] Housing 202 extends between distal end 204 and proximal end 206 along longitudinal axis 201. 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 201. In some examples, face 205 is slanted, e.g., face 205 defines a reference plane that is not orthogonal to longitudinal axis 201.

[0050] Face 205 may define a distal end of housing 202. Distal electrode 112A may extend distally from face 205 and along longitudinal axis 201. Distal electrode 112A may define a helical or spiral structure. Distal electrode 112A may extend distally from face 205 to a distal tip. An outer diameter of distal electrode 112A may be less than or equal to an outer diameter of housing 202.

[0051] Housing 202 may include one or more protrusions 214 extending radially away from an outer surface of housing 202. In some examples, as illustrated in FIG. 2, protrusion(s) 214 may define a helical protrusion extending radially away from the outer surface of housing 202 and defining a helix extending along longitudinal axis 201, e.g., to face 205. Each protrusion 214 may define a portion or an entirety of the helix. Each protrusion(s) 214 may extend partially or entirely around the outer perimeter of housing 202 and / or along longitudinal axis 201 from distal end 204 to proximal end 206. In some examples, as illustrated in FIG. 2, protrusion(s) 214 are disposed at or around distal end 204 of housing 202. In such examples, protrusion(s) 214 may be flush with face 205, may be proud of face 205, or may terminate at a position proximal to face 205. In some examples, protrusion(s) 214 are disposed at one or more other locations along the longitudinal length of housing 202, e.g., at or around proximal end 206 of housing 202.

[0052] Protrusion(s) 214 may define a helix with a variable or constant pitch. Protrusion(s) 214 may be disposed within or otherwise interface with corresponding features on a sheath coupled to device 104A (not pictured in FIG. 2). Protrusion(s) 214may interface with the corresponding features on the sheath to translate a rotation of device 104A about longitudinal axis 201 into a longitudinal movement of device 104A and distal electrode 112A along longitudinal axis 201.

[0053] Distal electrode 112A may be formed of an electrically conductive material, such as titanium, platinum, iridium, tantalum, stainless steel or alloys thereof. Distal electrode 112A may be coated with an electrically insulating coating, e.g., a parylene, polyurethane, silicone, epoxy, or other insulating coating, to reduce the electrically conductive active surface area of distal electrode 112 A, and thereby define a corresponding electrically active region. Defining the electrically active region of distal electrode 112A by covering portions of distal electrode 112A with an insulating coating may increase the electrical impedance of distal electrode 112A 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. In some examples, distal electrode 112A includes an electrically conducting material coating to define the electrically active region. For example, the electrically active region may be coated with titanium nitride (TiN).

[0054] In the example of FIG. 2, distal electrode 112A takes the form of a helix or a coil. Distal electrode 112A 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. Distal electrode 112A may extend from face 205 from a proximal end to a distal end. The proximal end may be a location along distal electrode 112A where distal electrode 112A extends distally past face 205 of device 104A. In some examples, distal electrode 112A takes the form of an elongated barb or other elongated body configured to penetrate into tissue.

[0055] In some examples, distal electrode 112A includes one or more anti-rotation features. The anti-rotation features may facilitate fixation of distal electrode 112A to the tissue. The additional anti-rotation features may include a shape of distal electrode 112A, dimensions (e.g., outer diameter, pitch, or the like) of distal electrode 112A, one or more features disposed on an outer surface of distal electrode 112A, or the like. The shape and / or dimensions of distal electrode 112A may include a geometric shape of distal electrode 112A, a varying diameter configuration of distal electrode 112A, a varying pitchconfiguration of distal electrode 112A, a waveform configuration of distal electrode 112A, or any combination herein. The one or more anti-rotation features disposed on distal electrode 112A 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 distal electrode 112A, e.g., by penetrating the tissue, by increasing the friction between distal electrode 112A and the tissue, or the like.

[0056] Distal electrode 112A may vary in size and shape in order to enhance tissue contact of the electrically active region. For example, distal electrode 112A 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.

[0057] The distal end of distal electrode 112A 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 can be a sharpened or angular tip or sharpened or beveled edges. In some examples, distal electrode 112A 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 distal electrode 112A may decrease from housing distal end 204 to the distal end of distal electrode 112A. In some examples, the diameter of distal electrode 112A varies from a proximal end to the distal end of distal electrode 112A. The varying diameter may cause distal electrode 112A to resist rotation within the tissue of heart 102.

[0058] The outer dimensions of distal electrode 112A can be substantially straight and cylindrical, with distal electrode 112A being rigid in some examples. Distal electrode 112A 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, distal electrode 112A can be configured to maintain a distance between the electrically active region and housing distal end 204 and / or between the electrically active region and the distal end of distal electrode 112A.

[0059] The distal end of distal electrode 112A can pierce through one or more tissue layers to position the electrically active region within a desired tissue layer, e.g., the ventricular myocardium 108 or interventricular septum. The depth of the desired tissue layer may vary, e.g., based on the position of target implantation region 106 within heart102. The clinician may rotate device 104A within the sheath to control the penetration of the cardiac tissue by distal electrode 112A and a depth of distal electrode 112A (e.g., of the electrically active region) within the cardiac tissue to place the electrically active region within the desired tissue layer. Distal electrode 112A may extend 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 201, 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, distal electrode 112A can maintain a spacing between a plurality of windings of distal electrode 112A when distal electrode 112A is a helix electrode. The spacing may be a pre-determined pitch of distal electrode 112A and may vary from distal end 204 to the distal end of distal electrode 112A. Distal electrode 112A may be longitudinally non-compressible. Distal electrode 112A may also be elastically deformable in lateral or radial directions when subjected to lateral or radial forces, however, to allow temporary flexing, e.g., with tissue motion, but returns to its normally straight position when lateral forces diminish. In some examples, when distal electrode 112A is not exposed to any external force, or to only a force along its longitudinal axis (substantially similar to or coincident with longitudinal axis 201), distal electrode 112A retains a straight, linear configuration as shown.

[0060] All, substantially all, or a portion of housing 202 may function as an electrode 212, e.g., an anode, during pacing and / or sensing. In some examples, electrode 212 circumscribes a portion of housing 202 at or near proximal end 206. Electrode 212 can fully or partially circumscribe housing 202. FIG. 2 shows electrode 212 extending as a singular band around the outer perimeter of housing 202. Electrode 212 can also include multiple segments spaced a distance apart along a longitudinal axis 201 of housing 202 and / or around a perimeter of housing 202.

[0061] 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 212.

[0062] 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 212.

[0063] In some examples, electrode 212 is a component, such as a ring electrode, that is mounted or assembled onto housing 202. Electrode 212 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 212 is located proximate to proximal end 206 of housing 202 and can be referred to as a proximal housing-based electrode. Electrode 212 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 201. In some examples, electrode 212 is paired with distal electrode 112A for sensing ventricular signals and delivering pacing pulses (e.g., atrial pacing pulses, ventricular pacing pulses).

[0064] In some examples, in place of distal electrode 112A, device 104A 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, the electrically active region can be positioned on a separate member and / or on the housing 202.

[0065] FIG. 3 A is a perspective diagram illustrating an example medical device assembly 302A including device 104A of FIG. 2. FIG. 3B is a cross-sectional diagram illustrating an example cross-sectional view of medical device assembly 302 A, the crosssection being taken along the longitudinal axis of medical device assembly 302A. The longitudinal axis of medical device assembly 302A may be the same as or parallel to longitudinal axis 201.

[0066] Medical device assembly 302 A may include device 104 A, a first sheath 304 disposed around a distal portion (e.g., distal end 204) of device 104A, and a second sheath 306 disposed around a proximal portion (e.g., proximal end 206) of device 104A. In a delivery configuration first sheath 304 may be coupled to second sheath 306 along junction 310, e.g., to encapsulate device 104A. First sheath 304 and second sheath 306may be separate components from device 104A. For example, second sheath 306 may be a portion of or attached to a medical delivery system (e.g., a medical device delivery catheter, medical device delivery tether system) configured to deliver device 104 A to target implant region 106 within the patient.

[0067] First sheath 304 may extend along a longitudinal axis and terminate in a distal face 303. The longitudinal axis of first sheath 304 may be the same as or parallel to longitudinal axis 201 when first sheath 304 is coupled to device 104A. Distal face 303 of first sheath 304 may be configured to be placed in contact with a surface of wall tissue of a chamber of heart 102 without penetrating the wall tissue. First sheath 304 may define one or more features placed on distal face 303 and / or around the outer surface of first sheath 304. The one or more features may be configured to interface with the surface of the wall tissue, e.g., to inhibit unintended movement and / or rotation of first sheath 304 and / or of device 104A relative to the wall tissue. The one or more features may include, but are not limited to, surface textures, protrusions, indentations, channels, ramps, tines, barbs, or the like. First sheath 304 may be 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.

[0068] First sheath 304 may define an inner volume 307. Inner volume 307 may be sized to retain device 104A and to allow distal movement of device 104A through first sheath 304 along longitudinal axis 201. First sheath 304 may define one or more tracks 312 along the inner surface of first sheath 304. Each track 312 may extending radially away from the inner surface of first sheath 304. Track(s) 312 may define a helical groove within the inner volume of first sheath 304. The helical groove may extend along at least a portion of the longitudinal length of first sheath 304. In some examples, as illustrated n FIG. 3B, the helical groove may extend along the entirety of the longitudinal length of first sheath 304.

[0069] Device 104 A may include one or more protrusions 214 on housing 202 of device 104A. Track(s) 312 on first sheath 304 may be sized to retain protrusion(s) 214 on device 104A. As device 104A is rotated about longitudinal axis 201 (e.g., via application of a torque on delivery tool interface member 208 of device 104 A), protrusion(s) 214 are advanced along the helical groove defined by track(s) 312, which causes device 104A(e.g., distal electrode 112A of device 104A) to rotate and advance distally within inner volume 307 of first sheath 304. Rotation of device 104A in a first direction (e.g., in a counterclockwise direction) about longitudinal axis 201 may causes device 104A to advance distally along longitudinal axis 201. Rotation of device 104A in a second direction opposite the first direction about longitudinal axis 201 (e.g., in a clockwise direction) may cause device 104A to retract proximally along longitudinal axis 201. Inner volume 307 of first sheath 304 may be sized such that protrusion(s) 214 of device 104A may only move along longitudinal axis 201 within track(s) 312 on first sheath 304. The interface between track(s) 312 and protrusion(s) 214 may provide fine-grain control over the longitudinal position of device 104A within first sheath 304 and / or relative to wall tissue at target implantation region 106. First sheath 304 may be alternatively referred to as being in threaded engagement with device 104A, e.g., track(s) 312 are in threaded engagement with protrusion(s) 214.

[0070] Distal face 303 may define opening 306 extending into inner volume 307. Opening 306 may be sized to allow for the travel of distal electrode 112A distally from within inner volume 307 of first sheath 304, e.g., and into wall tissue in contact with distal face 303 of first sheath 304. In some examples, opening 306 is sized to allow for the travel of face 205 of device 104A distally from within inner volume 307 of first sheath 304. First sheath 302 and second sheath 308 may interface to encapsulate device 104 A during delivery of device 104A to target implantation region 106. The clinician may advance distal electrode 112A distally from opening 306 when medical device assembly 302A is near target implantation region 106 to implant device 104A into tissue of the patient.

[0071] When distal face 303 is placed in contact with the wall tissue, distal face 303 may form a seal around opening 306, e.g., to inhibit tissue growth into opening 306 and inner volume 307. In some examples, a sealing element may be disposed over at least a portion of opening 306. In some examples, the sealing element encloses opening 306 prior and opens in response to distal movement of distal electrode 112A out of opening 306. The sealing element may reduce and / or eliminate any space between distal electrode 112A and an outer perimeter of opening 306, e.g., to allow movement of distal electrode 112A through opening 306 without permitting tissue growth into opening 306. The sealing element may be formed from a biocompatible material including, but is not limited to, silicone.

[0072] In some examples, first sheath 304 defines one or more openings and / or channels at or around distal face 303. Each opening and / or channel may extend from within inner volume 307 to an outer surface of first sheath 304. The one or more openings and / or channels may allow for the flow of fluid (e.g., a contrast fluid) out of inner volume 307. The flow of the contrast fluid out of the one or more openings and / or channels may aid in visualization of first sheath 304 and / or device 104A when first sheath 304 and / or device 104A is within patient vasculature and / or heart 102.

[0073] Second sheath 308 may define an inner volume 314 sized to retain device 104A. Second sheath 308 may be disposed over device 104A, e.g., without being affixed to device 104 A. For example, device 104 A may be configured to freely rotate within second sheath 308. Second sheath 308 may, when coupled to first sheath 304, interface with first sheath 304 to inhibit rotation of first sheath 304 about longitudinal axis 201.

[0074] The clinician may apply forces on device 104 A and on second sheath 308 to couple second sheath 308 to first sheath 304 or to release second sheath 308 from first sheath 304. For example, the clinician may apply a pulling force on device 104A along longitudinal axis 201 (e.g., via a tether assembly coupled to delivery tool interface member 208 of device 104 A) and a pushing force on second sheath 308 along longitudinal axis 201 to couple first sheath 304 to second sheath 308 along junction 310. The clinician may apply a pulling force on second sheath 308 along longitudinal axis 201 while applying a pushing force on device 104 A or maintaining a longitudinal position of device 104A to separate first sheath 304 from second sheath 308. As first sheath 304 is coupled to second sheath 308, the clinician may rotate device 104A about longitudinal axis 201 while keeping second sheath 308 stationary to facilitate rotate of device 104 A within first sheath 304 (e.g., without causing first sheath 304 to rotate), thereby advancing or retracting device 104A within first sheath 304.

[0075] The clinician may maintain (e.g., via second sheath 308), the position and / or orientation of distal face 303 and distal tip opening 306 of first sheath 303 relative to the wall tissue, as distal electrode 112A of device 104A is advanced into the tissue. In some examples, first sheath 304 includes an electrode (not pictured) disposed on distal face 303. The electrode may be electrically coupled to device 104 A and may be configured to be placed in contact with the surface of wall tissue without penetrating the wall tissue. As first sheath 303 maintains position during implantation of device 104A into wall tissue,first sheath 303 may cause the electrode to maintain the same position and / or orientation relative to the wall tissue surface. In such examples, the electrode on first sheath 304 may sense cardiac signals from and / or deliver pacing signals to the wall tissue (e.g., of a first chamber) while distal electrode 112A senses cardiac signals from and / or deliver pacing signals to cardiac tissue in another region of heart 102 (e.g., of a second chamber separate from the first chamber). The first chamber may be an atrium of heart 102 and the second chamber may be a ventricle of heart 102.

[0076] FIG. 4A is a perspective diagram illustrating a partially exploded view of example medical device assembly 302A of FIG. 3A. FIG. 4B is a cross-sectional diagram illustrating an example cross-sectional view of the partially exploded medical device assembly 302A of FIG. 4A, the cross-section being taken along the longitudinal axis of medical device assembly 302 A.

[0077] As illustrated in FIGS. 4 A and 4B, first sheath 304 extends along a longitudinal axis (e.g., longitudinal axis 201) from a distal end 402A to a proximal end 402B. Distal face 303 and opening 306 may be disposed at distal end 402A of first sheath 304. Second sheath 308 may extend along a longitudinal axis (e.g., longitudinal axis 201) to distal end 408. First sheath 304 may define one or more protrusions 404A and one or more recesses 406 A at proximal end 402B. Second sheath 308 may define one or more protrusions 404B and one or more recesses 406B at distal end 408. Each protrusion 404A on first sheath 304 may be sized to enter and interface with a recess 406B on second sheath 308 and each protrusion 404B may be sized to enter and interface with a recess 406A on first sheath 304. When first sheath 304 may be coupled to second sheath 308 when protrusions 404A are disposed within recesses 406B and protrusions 404B are disposed within recesses 406A. When first sheath 304 is coupled to second sheath 308, first sheath 304 is inhibited from rotating (e.g., about longitudinal axis 201) relative to second sheath 308. In such examples, when first sheath 304 is coupled to second sheath 308, the clinician may prevent first sheath 304 from rotating (e.g., as device 104A rotates) by maintaining the orientation of second sheath 308, and by extension, first sheath 304.

[0078] FIG. 5 is a perspective diagram illustrating a side view of another example medical device assembly 302B including device 104A of FIG. 2. Medical device assembly 302B may include device 104A and first sheath 502 and second sheath 308 disposedaround device 104A. First sheath 502 may be substantially similar to first sheath 304 illustrated in FIGS. 3A-4B, aside from the elements described below.

[0079] First sheath 502 may extend to a distal end 503. First sheath 502 may include face 504 and / or face 506 at distal end 503. Face 504 may be orthogonal to a longitudinal axis of medical device assembly 302B (e.g., to longitudinal axis 201). Face 504 may extend along a reference plane orthogonal to the longitudinal axis of medical device assembly 302B. Face 506 may extend along a reference plane offset (e.g., angled) from the longitudinal axis of medical device assembly 302B. The angular offset of face 506 may be up to 45 degrees. For examples, the angular offset is up to 20 degrees, up to 35 degrees, or up to 45 degrees. Face 504 may facilitate implantation of device 104A into the wall tissue at an orientation orthogonal to the surface of the wall tissue. Face 506 may facilitate implantation of device 104A into the wall tissue at an angle relative to the surface of the wall tissue.

[0080] FIG. 6 is a cross-sectional diagram illustrating an example partial cross- sectional view of another example medical device assembly 302C, the cross-section being taken along the longitudinal axis of medical device assembly 302C (e.g., along longitudinal axis 301). Medical device assembly 302C may include device 104B, a first sheath 602 disposed over a distal portion of device 104B, and second sheath 308. The components of medical device assembly 302C (e.g., device 104B, first sheath 602) may be substantially similar to other elements previously described herein (e.g., device 104A, first sheath 304, respectively), aside from the elements described below.

[0081] As illustrated in FIG. 6, device 104B may include an elongated body defining a helix or spiral extending along longitudinal axis 201. An outer diameter 610 of the elongated body may be greater than or equal to an outer diameter 612 of housing 202 of device 104B. In some examples, as illustrated in FIG. 6, the elongated body may define a distal electrode 112B of device 104B. Although the elongated body will be primarily described herein as distal electrode 112B, in some examples, distal electrode 112B is separate from the elongated body. For example, distal electrode 112B may be an elongated barb or projection disposed radially inwards of the elongated body. Distal electrode 112B of device 104B may define a greater cross-sectional area and / or a greater stiffness than distal electrode 112A of device 104A.

[0082] First sheath 602 may define an inner volume 606 and one or more tracks 604 extending along an inner surface of first sheath 602, e.g., in a manner similar to first sheath 304. Track(s) 604 may define a helical path within inner volume 606 and along an inner surface of first sheath 602. Track(s) 604 may define similar or different dimensions (e.g., pitches, widths along longitudinal axis 201, outer diameters) than track(s) 312 of first sheath 304.

[0083] Track(s) 604 may be sized to retain distal electrode 112B. As device 104B is rotated relative to first sheath 602, distal electrode 112B is advanced through track(s) 604 around and along longitudinal axis 201, thereby causing device 104B to advance or retract along longitudinal axis 201. A distal end of distal electrode 112B may exit a distal end of first sheath 602 through opening 608 at a distal face of first sheath 602. Opening 608 may be connected to track(s) 604. The distal face of first sheath 602 may be placed in contact with a tissue surface and, as device 104B rotates about longitudinal axis 201, the distal end of distal electrode 112B may protrude from first sheath 602 via opening 608 and penetrate into the tissue. First sheath 602 may be in threaded engagement with distal electrode 112B (e.g., track(s) 604 may be in threaded engagement with distal electrode 112B).

[0084] FIG. 7A is a cross-sectional diagram illustrating an example partial cross- sectional view of another example medical device assembly 302D, the cross-section being taken along the longitudinal axis of medical device assembly 302D. FIG. 7B is a perspective diagram illustrating a top view of example medical device assembly 302D. The longitudinal axis of medical device assembly 302D may be the same as or parallel to longitudinal axis 201. Medical device assembly 302D may include a first sheath 708, device 104C, and a second sheath (e.g., second sheath 308, not pictured). The elements of medical device assembly 302D may be substantially similar to the elements of any of medical devices assemblies 302A-302C previously described herein, aside from the elements described below.

[0085] Device 104C may include distal electrode 112A extending from face 205, a rotatable element 702 (e.g., a rotatable ring) disposed on face 205, and one or more tines 706 connected to rotatable element 702. Rotatable element 702 may be configured to rotate freely relative to housing 202 of device 104C. Retention element 704 (e.g., a retention bracket) may be disposed at least partially around and / or over rotatable element 702 to couple rotatable element 702 to device 104C without inhibiting rotation of rotatableelement 702. Rotatable element 702 may be disposed radially outwards of distal electrode 112A.

[0086] Rotatable element 702 may include one or more tines 706 extending distally from a distal surface of rotatable element 702. Each tine 706 may be configured to transition between a deployed configuration and an undeployed configuration. Tines 706 may be evenly distributed around the outer perimeter of rotatable element 702. Each tine 706 may expand radially outwards away from longitudinal axis 201 during the transition between the deployed and undeployed configurations. In the undeployed configuration, each tine 706 may penetrate tissue of the patient, e.g., to affix device 104C to the tissue. Each tine 706 may be formed from a shape memory material such as, but is not limited to, Nitinol.

[0087] First sheath 708 may define one or more recesses 710 at or around a distal end 705. Each recess 710 may be sized to retain a corresponding tine 706 of device 104C. When tines 706 are disposed within first sheath 708, first sheath 708 may retain tines 706 in the deployed configuration.

[0088] As device 104C is advanced distally out of first sheath 708 (e.g., in a manner previously described herein, such as via an interface between track(s) on first sheath 708 and protrusion(s) on device 104C, not pictured in FIGS. 7A and 7B), tine(s) 706 begin to transition from the deployed configuration to the undeployed configuration. Tine(s) 706 may enter and contact corresponding recesses 710 on first sheath 708. The interface between tine(s) 706 and recesses 710 may inhibit rotation of first sheath 708 with device 104C and may allow distal ends of tine(s) 706 to penetrate into tissue of the patient. The interface between tine(s) 706 and recesses 710 may not inhibit rotation of device 104C within first sheath 708, e.g., due to the rotation of rotatable element 702.

[0089] FIG. 8 is a block diagram illustrating an example configuration of an example device of any of FIGS. 1-7B. Device 104 may include any of devices 104A-104C previously described herein. In the example shown in FIG. 58, device 104 includes switch circuitry 802, sensing circuitry 804, signal generation circuitry 806, sensor(s) 808, processing circuitry 810, telemetry circuitry 812, memory 814, and power source 816. The various circuitry may be, or include, programmable or fixed function circuitry configured to perform the functions attributed to respective circuitry. Memory 814 may store computer-readable instructions that, when executed by processing circuitry 810, causedevice 104 to perform various functions. Memory 814 may be a storage device or other non-transitory medium. The components of device 104 illustrated in FIG. 8 may be housed within housing 202.

[0090] Signal generation circuitry 806 generates electrical stimulation signals, e.g., cardiac pacing pulses. Switch circuitry 802 is coupled to electrodes 112 (e.g., distal electrodes 112 A, 112B) and 212 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 802 is configured to direct stimulation signals from signal generation circuitry 806 to electrodes 112 and 212, having selected polarities, e.g., to selectively deliver pacing pulses to one or more positions within heart 102. For example, in order to pace one or both of the ventricles, switch circuitry 802 may couple distal electrode 112, which has penetrated to wall tissue of a ventricle or the intraventricular septum, to signal generation circuitry 806 as a cathode, and electrode 212 to signal generation circuitry 806 as an anode.

[0091] Each of electrodes 112, 212 may be coupled to switch circuitry 802 via a corresponding feedthrough assembly. In some examples, each feedthrough assembly is substantially straight (e.g., along longitudinal axis 201). In some examples, such as 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 201 to allow the header to turn relative to housing 202.

[0092] Switch circuitry 802 may also selectively couple sensing circuitry 804 to selected combinations of electrodes 112, 212, e.g., to selectively sense the electrical activity of one or more chambers of heart 102. Sensing circuitry 804 may include filters, amplifiers, analog-to-digital converters, or other circuitry configured to sense cardiac electrical signals via electrodes 112, 212. For example, switch circuitry 802 may couple distal electrode 112 (in combination with electrode 212) to a respective sensing channel provided by sensing circuitry 804 to sense ventricular cardiac electrical signals. In some examples, sensing circuitry 804 is configured to detect events, e.g., depolarizations, within the cardiac electrical signals, and provide indications thereof to processing circuitry 810.In this manner, processing circuitry 810 may determine the timing of atrial and ventricular depolarizations, and control the delivery of cardiac pacing based thereon. Processing circuitry 810 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 810 herein may be embodied as firmware, hardware, software or any combination thereof.

[0093] Sensor(s) 808 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) 808 may include one or more accelerometers, optical sensors, chemical sensors, temperature sensors, pressure sensors, or any other types of sensors.Sensor(s) 808 may output patient parameter values that may be used as feedback to control sensing and delivery of therapy by device 104.

[0094] Telemetry circuitry 812 supports wireless communication between device 104 and an external programmer (not shown in FIG. 8) or another computing device under the control of processing circuitry 810. Processing circuitry 810 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 812.Telemetry circuitry 812 may accomplish communication by radiofrequency (RF) communication techniques, e.g., via an antenna (not shown).

[0095] Power source 816 delivers operating power to various components of device 104. Power source 816 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.

[0096] FIG. 9 is a flowchart illustrating an example process for sensing a cardiac electrical signal and delivering cardiac pacing therapy to heart 102 of a patient via an example device 104 of any of FIGS. 1-8. While FIG. 9 is primarily described with reference to implanting an IMD within a heart of a patient, the process may be used to implant another IMD within tissue of a patient at one or more other locations within the body of the patient.

[0097] A clinician may insert device 104 within a chamber of heart 102 (902). Device 104 may be retained within a medical device assembly 302 (e.g., any of medical device assemblies 302A-D). Medical device assembly 302 may include device 104, a first sheath (e.g., first sheath 304, 502, 602, 708) coupled to and enclosing a distal portion of device 104, and a second sheath 308 enclosing a proximal portion of device 104. Together the first sheath and second sheath 308 may enclose the entirety of device 104.

[0098] One or more features on device 104 may interface with one or more corresponding features on the first sheath to couple device 104 to the first sheath. In some examples, the distal portion of device 104 (e.g., including distal electrode 112) is disposed within inner volume 307 of first sheath 304 and protrusion(s) 214 on housing 202 of device 104 is disposed within track(s) 312 in first sheath 304. In such examples, track(s) 312 may be sized to retain and facilitate movement of protrusion(s) 214 along a helical path defined by track(s) 312 (e.g., via rotation of device 104 about longitudinal axis 201) but may inhibit longitudinal movement of protrusion(s) 214 out of track(s) 312, e.g., via pushing or pulling on device 104 along longitudinal axis 201. In some examples, distal electrode 112B of device 104 may interface with track(s) 604 in first sheath 602, e.g., in a similar manner previously described herein with respect to protrusion(s) 214 and track(s) 312.

[0099] Second sheath 308 may be removably coupled to the first sheath at junction 310. Protrusion(s) 404A and recesses 406A on the first sheath may interface with protrusion(s) 404B and recesses 406B on second sheath 308 to form junction 310. When second sheath 308 is coupled to the first sheath, the second sheath 308 may control the rotation of the first sheath (e.g., about longitudinal axis 201).

[0100] Device 104 may be coupled to a tether assembly extending proximally out of the body of the patient. For example, device 104 may be coupled to a tether head of the tether assembly via delivery tool interface member 208. Second sheath 308 may extend proximally out of the body of the patient and may include one or more guide elements (e.g., a guide wire, a guide sheath) disposed at least partially within second sheath 308. Second sheath 308 may define inner volume 314 extending along the length of second sheath 308. Device 104 and the tether assembly may be disposed within inner volume 314.

[0101] During implantation, the clinician may control the position and movement of device 104 via a tether handle of the tether assembly and may control the position and / ormovement of second sheath 308 via a proximal end of second sheath 308. As the clinician navigates medical device assembly 302 within the vasculature of the patient and into the chamber of heart 102, the clinician may manipulate the tether assembly and / or second sheath 308 to cause the first sheath and second sheath 308 to enclose device 104 (e.g., to enclose distal electrode 112 of device 104). For example, the clinician may apply a pulling force on the tether assembly while applying a pushing force on second sheath 308 to cause second sheath 308 to contact the first sheath along junction 310. By enclosing device 104, medical device assembly 302 inhibits a risk of unintended penetration of tissue by device 104 (e.g., by distal electrode 112) during navigation of medical device assembly 302 into the chamber of heart 102.

[0102] The clinician may rotate device 104 to advance distal electrode 112 of device 104 to penetrate wall tissue of chamber of heart 102 (904). Once medical device assembly 302 is within the chamber of heart 102, the clinician may align medical device assembly 302 with target implantation region 106 within the chamber and cause a distal face (e.g., face 303, 504, 506) of the first sheath to contact a surface of wall tissue at target implantation region 106. The distal face of the first sheath may contact the surface orthogonally or at an angle.

[0103] Once the first sheath contacts the wall tissue surface, the clinician may begin rotating device 104 within medical device assembly 302 to advance distal electrode 112 of device 104 from within the first sheath. As device 104 is rotated relative to the first sheath, one or more elements of device 104 (e.g., distal electrode 112B, protrusion(s) 214) may advance within a helical path defined by one or more elements of the first sheath (e.g., track(s) 312, 604), which may translate at least a portion of the rotational motion of device 104 into longitudinal motion of device 104 along longitudinal axis 201. The clinician may rotate device 104 about longitudinal axis 201 via the tether handle. The clinician may continue to rotate device 104 until the distal end of distal electrode 112 of device 104 is at an intended depth within the wall tissue. The interface between the first sheath and device 104 may allow for fine-grain control of the implantation depth of distal electrode 112 by the clinician.

[0104] The first sheath may continue to contact the surface of wall tissue during and after implantation of device 104 into the wall tissue. The first sheath may remain coupled to device 104 and may inhibit unintended movement and / or rotation of device 104 withinthe wall tissue e.g., due to movement of the wall tissue. During rotation of device 104, the clinician may maintain the position and / or orientation of the first sheath relative to the wall tissue via second sheath 308. For example, the clinician may apply a force on second sheath 308, and via junction 310, on the first sheath to cause the first sheath to resist any torque transferred from device 104 to the first sheath. By maintaining the position and / or orientation of the first sheath relative to the wall tissue, medical device assembly 302 facilitates rotation and longitudinal travel of device 104 within the first sheath, e.g., without causing the first sheath to rotate with device 104.

[0105] The clinician may cause device 104 to deliver cardiac pacing signals from device 104 to the wall tissue via distal electrode (906). Depending on patient response and / or sensed signals from heart 102, the clinician may need to reposition device 104 within target implantation region 106. In such examples, the clinician may rotate device 104 in an opposite direction within the first sheath to retract distal electrode 112 from within the wall tissue. The clinician may iteratively adjust the implantation location within target implantation region 106 and / or an implantation depth of distal electrode 112 until the clinician determines that the patient response to cardiac pacing signals and / or sensed signals from heart 102 satisfy a threshold condition.

[0106] The clinician may then retract second sheath 308 relative to the first sheath to de-couple second sheath 308 from the first sheath. The clinician may de-couple the tether head of the tether assembly from device 104 (e.g., from delivery tool interface member 208 of device 104). The first sheath may remain around the distal portion of device 104 after implantation of device 104 within heart 102. The clinician may then remove second sheath 308 and the tether assembly from within the chamber of heart 102. Device 104 may then continue to deliver cardiac pacing signals to wall tissue of one or more chambers of heart 102, e.g., in accordance with the example techniques previously described herein.

[0107] FIG. 10 is a perspective diagram illustrating an example configuration of the device 102 (i.e., device 102D) of FIG. 1. Device 102D may be identical to devices 102A - C described above in FIGS. 1 - 9, aside from the features described below.

[0108] Device 102D may include housing 202 extending along longitudinal axis 201 from distal end 204 to proximal end 206. Device 102D may include delivery tool interface member 208 at proximal end 206. Device 102D may include fixation feature 1004 at or around distal end 204 of housing 202 and electrode 1002 disposed within housing 202 ator around proximal end 206 of housing 202. When device 102D is implanted within heart 102, device 104D may be placed in parallel with surface 1006 of cardiac tissue of heart 102, e.g., longitudinal axis 201 may be parallel with or substantially parallel with surface 1006.

[0109] Fixation feature 1004 may be configured to interface within surface 1006 of cardiac tissue of heart 102 to affix device 102 to the cardiac tissue. The cardiac tissue may include, but is not limited to, ventricular myocardium 108, interventricular septum of heart 102, or trabeculae carneae of heart 102. Fixation feature 1004 may affix device 102D to the cardiac tissue with or without penetrating surface 1006 of the cardiac tissue. Fixation feature 1004 may allow for the rotation of device 104D relative to surface 1006 once fixation feature 1004 is affixed to the tissue. Fixation feature 1004 may act as a pivot point for device 104D. For example, fixation feature 1004 is configured to, once affixed to the cardiac tissue of heart 102, permit rotation of device 104D to align longitudinal axis 201 to be parallel or orthogonal to surface 1006.

[0110] Electrode 1002 may be identical to distal electrode 112 previously described herein, aside from the features described below. Electrode 1002 may be formed from a shape memory material such as, but is not limited to, nitinol. The shape memory material may be coated with a substance such as, but is not limited to, platinum, e.g., to improve the elasticity, biocompatibility, and / or corrosion resistance of electrode 1002. Electrode 1002 may be configured to transition between a compressed state (e.g., within housing 202) and an uncompressed state (e.g., outside of housing 202. In the compressed state, electrode 1002 may define a helical shape. In the uncompressed state, electrode 1002 may define a curved, straight, or helical shape. Electrode 1002 may extend from a proximal end 1010 to a distal end 1012. Electrode 1002 may be electrically coupled, via proximal end 1010, to components within housing 202 (e.g., to switch circuitry 802) Electrode 1002 may wrap around longitudinal axis 201 within housing 202.

[0111] Housing 202 may include an opening 1008 disposed on an outer surface of housing 202. Opening 1008 may be circumferentially aligned with fixation feature 1004 and / or may be disposed on a same half of an outer perimeter of housing 202). In such examples, when fixation feature 1004 is affix to surface 1006, opening 1008 also faces surface 1006. When at least a portion of device 104D is rotated around longitudinal axis 201 (e.g., and relative to fixation feature 1004), distal end 1012 of electrode 1002 mayextend out of housing 202 through opening 1008. At least the portion of device 104D may be caused to rotate via a rotational force applied on delivery tool interface member 208 (e.g., via a delivery tool coupled to delivery tool interface member 208). As distal end 1012 of electrode 1002 exits housing 202 through opening 1008, distal end 1012 may penetrate surface 1006 and into the cardiac tissue (e.g., into ventricular myocardium 108). Device 104D may be rotated until at least a distal portion 1014 of electrode 1002 is within the cardiac tissue. Distal portion 1014 may have a length of up to 20 mm. Distal portion 1014 outside of housing 202 may define a curved, linear, helical or other shape. In some examples, the entire distal portion 1014 may be electrically conductive (i.e., may define an electrically active region of electrode 1002). In some examples, distal end 1012 and / or a portion of electrode 1002 at or around distal end 1012 may be electrically conductive.

[0112] Device 104D may include electrode 212 disposed on housing 202. Electrode 212 may be disposed around distal end 204 of housing 202, e.g., as illustrated in FIG. 10, around proximal end 206 of housing 202, or at any other location on housing 202. When device 104D is implanted in heart 102, e.g., in the configuration illustrated in FIG. 10, electrode 212 may be placed into contact with surface 1006 or may be separated from surface 1006.

[0113] FIGS. 11 A-D are perspective diagrams illustrating examples of fixation feature 1004 of device 104D. Each of fixation features 1004A-D (collectively referred to herein as “fixation features 1004”) may be disposed around an outer perimeter of distal end 204 of housing 202. Fixation features 1004 may be evenly distributed around the entire outer perimeter of distal end 204, biased around a specific portion of the outer perimeter of distal end 204, or only around the specific portion of the outer perimeter of distal end 204. The specific portion of the outer perimeter of distal end 204 may circumferentially overlap with opening 1008 at or around proximal end 206 of housing 202. In some examples, fixation features 1004 define electrically conductive surfaces and may function as an electrode of device 104D, e.g., in addition to or instead of electrode 212. In some examples, fixation features 1004 define electrically insulated surfaces.

[0114] Fixation feature 1004A may include one or more tines 1020. Each tine 1020 may extend from distal end 204. Each tine 1020 may extend radially outwards of longitudinal axis 201 from distal end 204. In some examples, as illustrated in FIG. 11 A, a distal tip of tine 1020 may curve back and extend towards proximal end 206 of housing202. Each tine 1020 may be formed from a shape memory material including, but is not limited to ni tinol. Each tine 1020 may define a sharp distal tip and may penetrate surface 1006 of the cardiac tissue, e.g., to affix device 104D to the cardiac tissue. Each tine 1020 may include additional fixation elements on the outer surface of tine 1020 including, but is not limited to, surface texture, prongs, barbs, or the like.

[0115] Each tine 1020 may be electrically coupled to components of device 104D (e.g., to switch circuitry 802) and may function as an electrode of device 104D. Each tine 1020 may transition between a collapsed configured and a deployed configuration, as illustrated in FIG. 11 A. In the collapsed configuration, tines 1020 may be constrained (e.g., by a delivery catheter) to extend distally along longitudinal axis 201 and to not extend radially beyond the outer perimeter of housing 202. When tines 1020 are unconstrained, tines 1020 may transition between from the collapsed configuration to the deployed configuration and penetrate surface 1006.

[0116] Fixation feature 1004B may include a one or more barbs 1024. Barbs 1024 may extend radially outward of distal end 204 of housing 202. In some examples, as illustrated in FIG. 1 IB, barbs 1024 extend from an extension 1022 coupled to distal end 204. Extension 1022 may extend distally from distal end 204 and radially outwards of housing 202. In some examples, a distal tip of extension 1022 may extend back towards proximal end 206 of housing 202. When extension 1022 is placed in contact with surface 1006, barbs 1024 may penetrate surface 1006, e.g., to affix device 104D to the cardiac tissue.

[0117] Fixation feature 1004C may include one or more scoops 1026. Each scoop 1026 may define a cavity extending proximally from distal end 204. Scoop 1026 may allow for entry of cardiac tissue into scoop 1026 when device 104D is oriented relative to surface 1006 such that longitudinal axis 201 is orthogonal to surface 1006 and distal end 204 is placed in contact with surface 1006. When device 104D is subsequently rotated (e.g., to place longitudinal axis 201 to be parallel to surface 1006), the cardiac tissue may interface with scoop 1026 (e.g., may envelop sides of scoop 1026and act against the sides of scoop 1026) to affix device 104D to the cardiac tissue. Scoop 1026 may affix device 104D to the cardiac tissue without penetrating surface 1006.

[0118] Fixation feature 1004D may include one or more ledges 1028. Ledge 1028 may extend distally from distal end 204 of housing 202. Ledge 1028 may allow for the flow ofcardiac tissue around ledge 1028 when device 104D is oriented relative to surface 1006 such that longitudinal axis 201 is orthogonal to surface 1006 and distal end 204 is placed in contact with surface 1006. When device 104D is subsequently rotated (e.g., to place longitudinal axis 201 to be parallel to surface 1006), the cardiac tissue may interface with ledge 1028 (e.g., may act against the sides of ledge 1028) to affix device 104D to the cardiac tissue. Ledge 1028 may affix device 104D to the cardiac tissue without penetrating surface 1006.

[0119] While each of fixation features 1004 is illustrated individually in FIGS. 11 A- 1 ID, an example device 104D may include two or more fixation features 1004 in any combination. In some examples, fixation features 1004 may be disposed elsewhere on housing 202 of device 104D. For example, fixation features 1004 may be disposed at or around proximal end 206 of housing 202 and electrode 1002 may be disposed at or around distal end 204 of housing 202.

[0120] FIG. 12 is a flowchart illustrating an example process for delivering cardiac pacing therapy to heart 102 of the patient via an example device 104D of any of FIGS. 10- 1 ID. While FIG. 12 is primarily described with reference to implanting device 104D within heart 102 of a patient, the process may be used to implant another IMD within tissue of a patient at one or more other locations within the body of the patient.

[0121] The clinician may insert device 104D within a chamber of heart 102 (1102). The clinician may insert device 104D into a chamber of heart 102 through vasculature of the patient, e.g., in accordance with one or more techniques previously described herein. The clinician may orient device 104D in a first orientation relative to a surface 1006 of wall tissue of the chamber (1104). When device 104D is in the first orientation, longitudinal axis 201 of device 104D may be orthogonal to surface 1006. The clinician may orient device 104 in the first orientation directly over target implant region 106 within the chamber of heart 102.

[0122] The clinician may affix fixation feature 1004 of device 104D to surface 1006 of the wall tissue (1106). The clinician may place distal end 204 of housing 202 of device 104D in contact with surface 1006. In some examples, such as when fixation feature 1004 includes scoops 1026 and / or ledges 1028, The clinician may place distal end 204 in contact with surface 1006, e.g., to allow wall tissue to flow into and / or around fixation feature 1004. In some examples, such as when fixation feature 1004 includes tines 1020,extension 1022, and / or barbs 1024, the clinician may deploy fixation feature 1004 (e.g., via retraction of a delivery catheter around device 104D) and cause fixation feature 1004 (e.g., tines 1020 and / or barbs 1024) to penetrate surface 1006 and affix device 104D to the wall tissue.

[0123] The clinician may orient device 104D to a second orientation relative to surface 1006 (1108). Once fixation feature 1004 is affixed to or engaged with surface 1006, the clinician may rotate device 104D relative to fixation feature 1004 to orient device 104D into the second orientation. When device 104D is in the second orientation, longitudinal axis 201 of device 104D may be parallel to surface 1006. In some examples, when fixation feature 1004 includes scoops 1026 and / or ledges 1028, rotation of device 104D to the second orientation causes the wall tissue to further engage with fixation feature 1004 and affix distal end 204 of housing 202 to the wall tissue. The clinician may rotate device 104D within heart 102 by applying a force on delivery tool interface member 208, e.g., in a direction orthogonal to longitudinal axis 201.

[0124] The clinician may rotate device 104D about longitudinal axis 201 to advance an elongated body containing electrode 1002 into the wall tissue (1110). Electrode 1002 may be stored in a compressed configuration within housing 202. The clinician may rotate at least a portion of device 104D (e.g., a proximal portion of device 104D) about longitudinal axis 201 by applying a torque to delivery tool interface member 208. In some examples, the torque is applied directly to an electrode assembly containing electrode 1002 and / or to electrode 1002 to rotate electrode 1002 within housing 202 without rotating any portion of housing 202. As the clinician rotates device 104D, distal end 1012 of electrode 1002 may exit housing 202 through opening 1008 on housing 202 and penetrate into the wall tissue. The clinician may continue to rotate device 104D until the clinician determines that a threshold portion of electrode 1002 is within the wall tissue. A distal portion 1014 of electrode 1002 exiting housing 202 may define a curved, straight, helical, or another shape. The clinician may deliver cardiac pacing signals to the wall tissue using electrode 1002 (1112), e.g., in accordance with one or more techniques previously described herein.

[0125] FIG. 13 is a perspective diagram illustrating an example medical device assembly 302E including an example device 104E of FIG. 1. Medical device assembly 302E may include device 104E, first sheath 1202 disposed over a distal portion of device104E, and a second sheath 1208 disposed over a proximal portion of device 104E and removably coupled to first sheath 1202. First sheath 1202 may be similar to first sheath 502 of FIG. 5 and second sheath 1208 may be similar to second sheath 508 of FIG. 5, aside from the differences described below. Device 104E may be similar to device 104 A and may include the same components, aside form the differences described below.

[0126] First sheath 1202 may be disposed over a distal portion of device 104E. A distal end of first sheath 1202 may be configured to be placed in contact with wall tissue of heart 102 and may define one or more surfaces. The distal end of first sheath 1202 may be rounded around the outer perimeter of first sheath 1202. For example, as illustrated in FIG. 13, the distal end of first sheath 1202 may define a first surface 1204 and a second surface 1206. Second surface 1206 may extend along a reference plane orthogonal to longitudinal axis 201 of device 104E. First surface 1204 may be angled relative to second surface 1206 (e.g., may extend along a reference plane offset from longitudinal axis 201. The angle of first surface 1204 relative to longitudinal axis 201 may be up to 45 degrees (e.g., about 20 degrees, about 35 degrees, about 45 degrees). Each of first and second surfaces 1204, 1206 may include fixation elements disposed along the surface, e.g., to improve fixation of first sheath 1202 to wall tissue of heart 102. The fixation elements may include, but are not limited, barbs, tines, surface texture, protrusions, recesses, fixation helix, or the like.

[0127] First sheath 1202 may define an opening (not pictured in FIG. 13) extending from an inner volume of first sheath 1202 through the distal end of first sheath 1202. The opening may be size to allow for the exit of distal electrode 112C of device 104E out of the inner volume of first sheath 1202. The opening may be disposed on first surface 1202 and / or second surface 1204 and may be configured to direct distal end 1214 of distal electrode 112C along reference axis 1216. Reference axis 1216 may be offset from longitudinal axis 201. By angle 1218 and may be offset from first surface 1204 by angle 1220. Angle 1218 may be up to 90 degrees. Angle 1220 may be up to 90 degrees. In some examples, reference axis 1216 is orthogonal to the reference plane defined by first surface 1204. Angles 1218, 1220 may reduce a likelihood of a trapping or a pinching of wall tissue between the distal end of first sheath 1202 and distal electrode 112C, e.g., thereby reducing irritation and / or inflammation of the wall tissue. Angles 1218, 1220 may allow for placement of distal electrode 112C at a specific location in heart 102 independent of anangle between device 104E and the wall tissue of heart 102, e.g., thereby allowing implantation of distal electrode 112C within the wall tissue of heart 102 when device 104E is not orthogonal to the wall tissue. Extending distal electrode 112C along reference axis 1216 and having the distal end of first sheath 1202 including first and second surfaces 1204, 1206 may increase a range of possible orientations for device 104E within heart 102, thereby increasing a number of possible target implant regions 106 within heart 102, e.g., by allowing for access to specific target implant regions 106 previously restricted by an inability to orient the IMD to be orthogonal to tissue surface at the specific target implant regions 106.

[0128] Distal electrode 112C may assume a compressed shape and an uncompressed shape. A portion of distal electrode 112C disposed within the inner volume of first sheath 1202 may be at least partially compressed by first sheath 1202 and assume the compressed shape. In some examples, an entirety of distal electrode 112C may be disposed within the inner volume of first sheath 1202 and may assume the compressed shape. A portion of distal electrode 112C exiting first sheath 1202 at the opening may assume the uncompressed shape. The compressed shape may include, but is not limited to, a helix extending around longitudinal axis 201. The uncompressed shape may include, but is not limited to, a curved, straight, or helical shape extending along reference axis 1216. Distal electrode 112C may be formed from a shape memory material such as, but is not limited to, Nitinol. Distal electrode 112C may be coated within an electrically conductive material such as Platinum or Titanium Nitride to allow for the conduction of electrical signals through distal electrode 112C. The electrically conductive material may improve biocompatibility and / or corrosion resistance of distal electrode 112C. The electrically conductive material may increase a surface area of distal electrode 112C.

[0129] First sheath 1202 may be configured to freely rotate relative to device 104E. Rotation of first sheath 1202 relative to device 104E may cause distal electrode 112C to advance from first sheath 1202 and / or retract into first sheath 1202 along reference axis 1216. For example, rotation of device 104E relative to first sheath 1202 in a first direction causes distal electrode 112C to advance along reference axis 1216 and rotation of device 104E relative to first sheath 1202 in a second direction opposite the first direction causes distal electrode 112C to retract along longitudinal axis 1216.

[0130] Second sheath 1208 may interface with first sheath 1202 to inhibit rotation of first sheath 1202 with device 104E as the clinician applies a rotational force on device 104E. Second sheath 1208 may interface with first sheath 1202 in a same manner as previously described herein (e.g., with respect to first sheath 302 and second sheath 308).

[0131] Second sheath 1208 may define an electrically conductive band 1212 disposed within a body of second sheath 1208 (e.g., radially inward of an outer perimeter of second sheath 1208. Electrically conductive band 1212 may be exposed to an environment external to medical device assembly 302E via one or more windows 1210 on second sheath 1208. Electrically conductive band 1212 may allow for the transmission of electrical signals into or out of device 104E (e.g., into or out of electrode 212 of device 104E). Electrically conductive band 1212 may be in contact with or separated from device 104E (e.g., from electrode 212 and / or housing 202 of device 104E). Electrically conductive band 1212 may allow for the transmission of electrical signals into or out of device 104E (e.g., for determination of a placement of device 104E within heart 102) while inhibiting an unintended flow of fluids (e.g., blood, a contrast medium) into or out of medical device assembly 302).

[0132] FIG. 14 is a perspective diagram illustrating an example first sheath 1202 of medical device assembly 302E of FIG. 13. As illustrated in FIG. 14, distal end 1302 of first sheath 1202 may define first and second surfaces 1204, 1206. First sheath 1202 may define openings 1304, 1306 on distal end 1302. Opening 1306 may be disposed on distal end 1302 (e.g., on one or more of first surface 1204, second surface 1206) and may be connected to an inner volume of first sheath 1202 via channel 1308.

[0133] Opening 1306 and channel 1308 may be sized to allow for the movement of distal electrode 112C through opening 1306 and channel 1308. Opening 1306 may be flush with one or more of first and second surfaces 1204, 1206 and may be shaped to direct distal electrode 112C away from distal end 1302 along reference axis 1216 (illustrated in FIG. 13). In some examples, as illustrated in FIG. 14, opening 1306 may be oriented relative to one or more of first and second surfaces 1204, 1206 to allow distal electrode 112C to exit opening 1306 and penetrate wall tissue of heart 102 at a substantially orthogonal angle to the wall tissue. Channel 1308 may define a helical path within first sheath 1202 and may be configured to maintain at least a portion of distal electrode 112C within channel 1308 in a helical configuration. First sheath 1202 mayinclude one or more stops along channel 1308, e.g., to inhibit overextension of distal electrode 112C out of first sheath 1202. In some examples, radiopaque markers are disposed on first sheath 1202 and / or second sheath 1208, e.g., to notify the clinician of possible over-retraction or over-extension of distal electrode 112C relative to first sheath 112C.

[0134] First sheath 1202 may define opening 1304 at distal end 1302. Opening 1304 may be disposed radially inward of opening 1306 and / or channel 1308. Opening 1304 may extend through first sheath 1202 into the inner volume of first sheath 1202 and may fluidically connect the inner volume of first sheath 1202 to an external environment surrounding medical device assembly 302E. Opening 1304 may allow for the flow of a fluid (e.g., a contrast medium) out of the inner volume of first sheath 1202 and into the external environment surrounding medical device assembly 302E. In some examples, device 104E includes a center electrode disposed radially inward of distal electrode 112C. In such examples, the center electrode may extend through opening 1304 and contact wall tissue of heart 102.

[0135] First sheath 1202 may include one or more protrusions 404 A and one or more recesses 406A at a proximal end of first sheath 1202. Protrusions 404A and recesses 406A may interface with corresponding protrusions (e.g., protrusions 404B) and recesses (e.g., recesses 406B) on second sheath 1208 (not pictured in FIG. 14) to inhibit unintended rotation of first sheath 1202 about longitudinal axis 201, e.g., in accordance with one or more techniques previously described herein.

[0136] FIG. 15 is a cross-sectional diagram illustrating an example partial cross- sectional view of the example medical device assembly 302E of FIG. 13, the cross-section being taken along longitudinal axis 201 of medical device assembly 302E.

[0137] As illustrated in FIG. 15, first sheath 1202 may be coupled to a distal portion of device 104E. When device 104E is coupled to first sheath 1202, at least a portion of distal electrode 112C is retained within inner volume 1402 of first sheath 1202 in a compressed state (e.g., in a helical shape). At least a portion of distal electrode 112C may be disposed within channel 1308. When device 104E is rotated relative to first sheath 1202, distal electrode 112C may exit inner volume 1402 via opening 1306 (not pictured in FIG. 15) connected to channel 1308. Opening 1304 extends through distal end 1302 of first sheath 1202 into inner volume 1402. The clinician may expel a fluid (e.g., a contrast medium)from inner volume 1402 (e.g., into a chamber of heart 102) via opening 1304. Distal end 1302 of first sheath 1202 may define first and second surfaces 1204, 1206. First surface 1204 may be angled relative to second surface 1206, which may increase a number of possible implant orientations for device 104E relative to a surface of target implant region 106.

[0138] First sheath 1202 may define a one or more protrusions 1406 extending radially inwards (e.g., towards longitudinal axis 201). Each of protrusions 1406 may extend at least partially around an inner perimeter of first sheath 1202. Device 104E may define, at or around distal end 204 of housing 202, a recess 1404. Recess 1404 may extend around an entire perimeter of housing 202 and may be sized to retain protrusions 1406. When device 104E is coupled to first sheath 1202, protrusions 1206 may be disposed within recess 1404, which may allow for movement of protrusions 1206 around longitudinal axis and inhibit longitudinal movement of protrusions 1206 along longitudinal axis 201.Protrusions 1406 and recess 1404 may thereby interface to affix first sheath 1202 to device 104E and allow for free rotation of first sheath 1202 relative to device 104E (e.g., to advance or retract distal electrode 112C from inner volume 1402 of first sheath 1202). Protrusions 1406 may be disposed within recess 1404 via a snap-fit arrangement, via a combination of two or separate components of first sheath 1202 around device 104E, or the like.

[0139] When second sheath 1208 is coupled to first sheath 1202, a proximal portion of device 104E may be disposed within inner volume 1408 of second sheath 1208.Electrically conductive band 1212 may be exposed along an outer surface (e.g., via windows 1210) to an external environment around medical device assembly 302E and along an inner surface to inner volume 1408. Electrical signals may be transmitted between electrically conductive band 1212 and device 104E (e.g., with electrode 212 and / or housing of device 104E). Electrically conductive band 1212 may be arranged along second sheath 1208 to longitudinally and circumferentially overlap with at least a portion of electrode 212 of device 104E when device 104E is disposed within inner volume 1408. An inner surface of electrically conductive band 1212 may be in contact with or separated from electrode 212.

[0140] It should be understood that various aspects disclosed herein may be combined in different combinations than the combinations specifically presented in the descriptionand 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.

[0141] 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).

[0142] 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.

[0143] 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.

[0144] This disclosure describes each of the following examples.

[0145] Example 1 : a system comprising: an implantable medical device (IMD) 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 achamber of a heart; and an elongated body extending distally from the distal end of the elongated housing and defining a helix, the helix defining an electrode at or proximate a distal end of the helix; and a sheath disposed around a distal portion of the IMD, the sheath defining one or more tracks extending along a surface of the sheath, wherein the one or more tracks are configured to interface with the IMD to facilitate distal movement of the elongated body through the sheath and into wall tissue of the chamber in response to rotation of the IMD about the longitudinal axis.

[0146] Example 2: the system of example 1, wherein the IMD defines one or more helical protrusions disposed radially outwards of an outer surface of the elongated housing and extending along the longitudinal axis, wherein the one or more tracks of the sheath define a helical recess extending along an inner surface of the sheath, wherein the helical recess is sized to retain the one or more helical protrusions of the IMD and to allow travel of the one or more helical protrusions through the helical recess, and wherein as the one or more helical protrusions advance through the helical recess in response to the rotation of the IMD, the helical recess causes the IMD to advance distally through the sheath.

[0147] Example 3: the system of example 1, wherein the helix defines an outer diameter greater than or equal to an outer diameter of the elongated housing, wherein the one or more tracks of the sheath define a helical recess extending along an inner surface of the sheath, wherein the helical recess is sized to retain the helix and to allow travel of the helix through the helical recess, and wherein as the helix advances through the helical recess in response to the rotation of the IMD, the helical recess causes the IMD to advance distally through the sheath.

[0148] Example 4: the system of any of examples 1-3, wherein the sheath comprises a first sheath defining a proximal end, and wherein the system further comprises: a second sheath configured to retain the IMD, wherein a distal end of the second sheath is configured to interface with the proximal end of the first sheath to inhibit unintended rotation of the first sheath relative to the wall tissue.

[0149] Example 5: the system of example 4, wherein the IMD is configured to freely rotate relative to the second sheath, and wherein the second sheath is configured to interface with the first sheath to inhibit the unintended rotation of the first sheath as the IMD is rotated about the longitudinal axis and is advanced through the first sheath.

[0150] Example 6: the system of any of examples 4 or 5, wherein the first sheath defines one or more protrusions at the proximal end, wherein the second sheath defines one or more recesses at the distal end, wherein the one or more protrusions is configured to interface with the one or more recesses to inhibit the unintended rotation of the first sheath.

[0151] Example 7: the system of any of examples 1-6, wherein the sheath defines a distal surface, the distal surface being configured to contact a surface of the wall tissue without penetrating the wall tissue.

[0152] Example 8: the system of example 7, wherein the distal surface of the sheath defines one or more fixation features configured to interface with the surface of the wall tissue to inhibit unintended movement of the sheath relative to the wall tissue.

[0153] Example 9: the system of example 8, wherein the one or more fixation features comprises one or more of: one or more protrusions; one or more recesses; one or more tines; one or more textured surfaces; or one or more ramps.

[0154] Example 10: the system of any of examples 7-9, wherein the distal surface of the sheath comprises an angled surface extending along a reference plane offset from a longitudinal axis of the sheath.

[0155] Example 11 : the system of example 10, wherein the angled surface encompasses at least a portion of the distal surface.

[0156] Example 12: the system of any of examples 1-11, wherein the IMD comprises: a rotatable ring disposed on the distal end of the IMD, the rotatable ring being configured to freely rotate relative to the IMD; and one or more tines affixed to the rotatable ring and extending radially away from the longitudinal axis, wherein the sheath is configured to retain the one or more tines in an undeployed configuration when the IMD is in a proximal position within the sheath, and wherein as the IMD advances distally within the sheath, the one or more tines advance out of a distal end of the sheath and transition from the undeployed configuration to a deployed configuration to penetrate the wall tissue.

[0157] Example 13: the system of example 12, wherein as the one or more tines advance out of the distal end of the sheath, the one or more tines interface with one or more of the one or more tracks of the sheath or one or more recesses at or around the distal end of the sheath to inhibit unintended rotation of the sheath relative to the wall tissue.

[0158] Example 14: the system of any of examples 1-13, wherein the chamber comprises a ventricle of the heart.

[0159] Example 15: 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 elongated body along a longitudinal axis and defining one or more coils, wherein a distal end of the helix is configured to penetrate into tissue of a patient; and a sheath disposed radially outwards of the elongated body, the sheath defining one or more tracks extending along a surface of the sheath, wherein the one or more tracks is configured to interface with the elongated body to facilitate distal movement of the elongated body through the sheath and into wall tissue of the chamber in response to rotation of the IMD about the longitudinal axis.

[0160] Example 16: the fixation device of example 15, wherein the helix defines an outer diameter greater than or equal to an outer diameter of the IMD, wherein the one or more tracks of the sheath define a helical recess extending along an inner surface of the sheath, wherein the helical recess is sized to retain the helix and to allow travel of the helix through the helical recess, and wherein as the helix advances through the helical recess in response to the rotation of the IMD, the helical recess causes the helix to advance distally through the sheath.

[0161] Example 17: the fixation device of any of examples 15 or 16, wherein the sheath comprises a first sheath defining a proximal end, and wherein the system further comprises: a second sheath configured to retain the IMD, wherein a distal end of the second sheath is configured to interface with the proximal end of the first sheath to inhibit unintended rotation of the first sheath.

[0162] Example 18: the fixation device of example 17, wherein the IMD is configured to freely rotate relative to the second sheath, and wherein the second sheath is configured to interface with the first sheath to inhibit the unintended rotation of the first sheath as the helix is rotated about the longitudinal axis.

[0163] Example 19: the fixation device of any of examples 17 or 18, wherein the first sheath defines one or more protrusions at the proximal end, wherein the second sheath defines one or more recesses at the distal end, wherein the one or more protrusions is configured to interface with the one or more recesses to inhibit the unintended rotation of the first sheath.

[0164] Example 20: the fixation device of any of examples 15-19, wherein the elongated body defines a distal surface, the distal surface being configured to contact a surface of the tissue without penetrating the tissue.

[0165] Example 21 : the fixation device of example 20, wherein the distal surface of the sheath defines one or more fixation features configured to interface with the surface of the wall tissue to inhibit unintended movement of the sheath relative to the wall tissue.

[0166] Example 22: the fixation device of example 21, wherein the one or more fixation features comprises one or more of: one or more protrusions; one or more recesses; one or more tines; one or more textured surfaces; or one or more ramps.

[0167] Example 23: the fixation device of any of examples 20-22, wherein the distal surface of the sheath comprises an angled surface extending along a reference plane offset from a longitudinal axis of the sheath.

[0168] Example 24: the fixation device of example 23, wherein the angled surface encompasses at least a portion of the distal surface.

[0169] Example 25: the fixation device of any of examples 15-24, further comprising a tine assembly disposed on the distal end of the IMD, the tine assembly comprising: a rotatable ring disposed on the distal end of the IMD, the rotatable ring being configured to freely rotate relative to the IMD; and one or more tines affixed to the rotatable ring and extending radially away from the longitudinal axis, wherein the sheath is configured to retain the one or more tines in an undeployed configuration when the IMD is in a proximal position within the sheath, and wherein as the elongated body advances distally within the sheath, the one or more tines advance out of a distal end of the sheath and transition from the undeployed configuration to a deployed configuration to penetrate the wall tissue.

[0170] Example 26: the fixation device of example 25, wherein as the one or more tines advance out of the distal end of the sheath, the one or more tines interface with one or more of the one or more tracks of the sheath or one or more recesses at or around the distal end of the sheath to inhibit unintended rotation of the sheath relative to the wall tissue.

[0171] Example 27: a system comprising: an implantable medical device (IMD) 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 theelongated housing and defining a helix, the helix defining an electrode at or proximate a distal end of the helix; a rotatable ring disposed on the distal end of the IMD, the rotatable ring being configured to freely rotate relative to the IMD; and one or more tines affixed to the rotatable ring and extending radially away from the longitudinal axis; and a sheath disposed around a distal portion of the IMD, the sheath extending along the longitudinal axis, wherein the elongated body is configured to be advanced distally through the sheath in response to rotation of the IMD about the longitudinal axis to penetrate wall tissue of the chamber, wherein the sheath is configured to retain the one or more tines in an undeployed configuration when the IMD is in a proximal position within the sheath, and wherein as the IMD advances distally within the sheath, the one or more tines advance out of a distal end of the sheath and transition from the undeployed configuration to a deployed configuration to penetrate the wall tissue.

[0172] Example 28: the system of example 27, wherein as the one or more tines advance out of the distal end of the sheath, the one or more tines interface with one or more recesses at or around the distal end of the sheath to inhibit unintended rotation of the sheath relative to the wall tissue.

[0173] Example 29: the system of any of examples 27 or 28, wherein sheath defines one or more tracks extending along an inner surface of the elongated body, wherein the one or more tracks are configured to interface with the IMD to facilitate distal movement of the IMD through the sheath in response to rotation of the IMD about the longitudinal axis.

[0174] Example 30: the system of examples 29, wherein the IMD defines one or more helical protrusions disposed radially outwards of an outer surface of the elongated housing and extending along the longitudinal axis, wherein the one or more tracks of the sheath define a helical recess extending along an inner surface of the sheath, wherein the helical recess is sized to retain the one or more helical protrusions of the IMD and to allow travel of the one or more helical protrusions through the helical recess, and wherein as the one or more helical protrusions advance through the helical recess in response to the rotation of the IMD, the helical recess causes the IMD to advance distally through the sheath.

[0175] Example 31 : the system of example 29, wherein the helix defines an outer diameter greater than or equal to an outer diameter of the sheath, wherein the one or more tracks of the sheath define a helical recess extending along an inner surface of the sheath,wherein the helical recess is sized to retain the helix and to allow travel of the helix through the helical recess, and wherein as the helix advances through the helical recess in response to the rotation of the IMD, the helical recess causes the IMD to advance distally through the sheath.

[0176] Example 32: the system of any of examples 27-31, wherein the sheath comprises a first sheath defining a proximal end, and wherein the system further comprises: a second sheath configured to retain the IMD, wherein a distal end of the second sheath is configured to interface with the proximal end of the first sheath to inhibit unintended rotation of the first sheath relative to the wall tissue.

[0177] Example 33: the system of example 32, wherein the IMD is configured to freely rotate relative to the second sheath, and wherein the second sheath is configured to interface with the first sheath to inhibit the unintended rotation of the first sheath as the IMD is rotated about the longitudinal axis and is advanced through the first sheath.

[0178] Example 34: the system of any of examples 32 or 33, wherein the first sheath defines one or more protrusions at the proximal end, wherein the second sheath defines one or more recesses at the distal end, wherein the one or more protrusions is configured to interface with the one or more recesses to inhibit the unintended rotation of the first sheath.

[0179] Example 35: the system of any of examples 27-34, wherein the sheath defines a distal surface, the distal surface being configured to contact a surface of the wall tissue without penetrating the wall tissue.

[0180] Example 36: the system of example 35, wherein the distal surface of the sheath defines one or more fixation features configured to interface with the surface of the wall tissue to inhibit unintended movement of the sheath relative to the wall tissue.

[0181] Example 37: the system of example 36, wherein the one or more fixation features comprises one or more of: one or more protrusions; one or more recesses; one or more tines; one or more textured surfaces; or one or more ramps.

[0182] Example 38: the system of any of examples 35-37, wherein the distal surface of the sheath comprises an angled surface extending along a reference plane offset from a longitudinal axis of the sheath.

[0183] Example 39: the system of example 38, wherein the angled surface encompasses at least a portion of the distal surface.

[0184] Example 40: a method comprising: inserting a distal portion of a medical device system within a chamber of a heart, the distal portion of the medical device system comprising: an implantable medical device (IMD) comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis; and an elongated body extending distally from the distal end of the elongated housing and defining a helix, the helix defining an electrode at or proximate a distal end of the helix; and a sheath disposed around a distal portion of the IMD, the sheath defining one or more tracks extending along a surface of the sheath; rotating the IMD about the longitudinal axis to advance the elongated body of the IMD through the one or more tracks of the sheath to advance the IMD distally through the sheath along the longitudinal axis and cause the elongated body to penetrate wall tissue of the chamber; and delivering cardiac pacing signals from the IMD to wall tissue of the chamber via the electrode.

[0185] Example 41 : the method of example 40, wherein the IMD defines one or more helical protrusions disposed radially outwards of an outer surface of the elongated housing and extending along the longitudinal axis, wherein the one or more tracks of the elongated tube define a helical recess extending along an inner surface of the elongated tube, and wherein rotating the IMD about the longitudinal axis to advance the elongated body through the one or more tracks of the sheath comprises: rotating the IMD about the longitudinal axis to advance the one or more helical protrusions through the helical recess to advance the IMD distally through the sheath.

[0186] Example 42: the method of example 40, wherein the helix defines an outer diameter greater than or equal to an outer diameter of the elongated housing, wherein the one or more tracks of the elongated tube define a helical recess extending along an inner surface of the elongated tube, and wherein rotating the IMD about the longitudinal axis to advance the elongated body through the one or more tracks of the sheath comprises: rotating the IMD about the longitudinal axis to advance the helix through the helical recess to advance the IMD distally through the sheath.

[0187] Example 43: the method of any of examples 40-42, wherein the sheath comprises a first sheath defining a proximal end, and wherein the system further comprises: a second sheath configured to retain the IMD, wherein a distal end of the second sheath is configured to interface with the proximal end of the first sheath, and wherein rotating the IMD about the longitudinal axis comprises: rotating the IMD aboutthe longitudinal axis while maintaining an orientation of the first sheath and of the second sheath relative to the wall tissue.

[0188] Example 44: the method of any of examples 40-43, wherein a distal surface of the sheath defines an angled surface extending along a reference plane offset from the longitudinal axis, and wherein inserting the distal portion of a medical device system within the chamber of a heart comprises: placing the angled surface of the distal surface of the sheath in contact with a surface of the wall tissue; and rotating the IMD about the longitudinal axis to advance the IMD distally out of the sheath and penetrate the surface of the wall tissue, wherein the longitudinal axis is angled from the surface of the wall tissue.

[0189] Example 45: a system comprising: a leadless pacemaker (LP) 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 a helix extending distally from the distal end of the housing, the helix defining an electrode at or proximate a distal end of the helix; and a sheath disposed around a distal portion of the LP and in threaded engagement with the distal portion of the LP, to facilitate distal movement of the helix through the sheath and into wall tissue of the chamber in response to rotation of the LP about the longitudinal axis.

[0190] Example 46: the system of example 45, wherein the LP defines one or more helical protrusions disposed radially outwards of an outer surface of the elongated housing and extending along the longitudinal axis, wherein the sheath is configured to be in threaded engagement with the one or more helical protrusions of the LP, wherein as the one or more helical protrusions along the threaded engagement with the sheath, the LP advances distally through the sheath.

[0191] Example 47: the system of example 45, wherein the helix defines an outer diameter greater than or equal to an outer diameter of the elongated housing, wherein the sheath is configured to be in threaded engagement with the helix, and wherein as the helix advances along the threaded engagement with the sheath, the LP advances distally through the sheath.

[0192] Example 48: the system of any of examples 45-47, wherein the sheath comprises a first sheath defining a proximal end, and wherein the system further comprises: a second sheath configured to retain the LP, wherein a distal end of the secondsheath is configured to interface with the proximal end of the first sheath to inhibit unintended rotation of the first sheath relative to the wall tissue.

[0193] Example 49: the system of example 48, wherein the LP is configured to freely rotate relative to the second sheath, and wherein the second sheath is configured to interface with the first sheath to inhibit the unintended rotation of the first sheath as the LP is rotated about the longitudinal axis and is advanced through the first sheath.

[0194] Example 50: the system of any of examples 48 or 49, wherein the first sheath defines one or more protrusions at the proximal end, wherein the second sheath defines one or more recesses at the distal end, wherein the one or more protrusions is configured to interface with the one or more recesses to inhibit the unintended rotation of the first sheath.

[0195] Example 51 : the system of any of examples 45-50, wherein the sheath defines a distal surface, the distal surface being configured to contact a surface of the wall tissue without penetrating the wall tissue.

[0196] Example 52: the system of example 51, wherein the distal surface of the sheath defines one or more fixation features configured to interface with the surface of the wall tissue to inhibit unintended movement of the sheath relative to the wall tissue.

[0197] Example 53: the system of example 52, wherein the one or more fixation features comprises one or more of: one or more protrusions; one or more recesses; one or more tines; one or more textured surfaces; or one or more ramps.

[0198] Example 54: the system of any of examples 51-53, wherein the distal surface of the sheath comprises an angled surface extending along a reference plane offset from a longitudinal axis of the sheath.

[0199] Example 55: the system of example 54, wherein the angled surface encompasses at least a portion of the distal surface.

[0200] Example 56: the system of any of examples 45-55, wherein the LP comprises: a rotatable ring disposed on the distal end of the LP, the rotatable ring being configured to freely rotate relative to the LP; and one or more tines affixed to the rotatable ring and extending radially away from the longitudinal axis, wherein the sheath is configured to retain the one or more tines in an undeployed configuration when the LP is in a proximal position within the sheath, and wherein as the LP advances distally within the sheath, theone or more tines advance out of a distal end of the sheath and transition from the undeployed configuration to a deployed configuration to penetrate the wall tissue.

[0201] Example 57: the system of example 55, wherein as the one or more tines advance out of the distal end of the sheath, the one or more tines interface with one or more of the one or more tracks of the sheath or one or more recesses at or around the distal end of the sheath to inhibit unintended rotation of the sheath relative to the wall tissue.

[0202] Example 58: the system of any of examples 45-57, wherein the chamber comprises a ventricle of the heart.

[0203] Example 59: a system comprising: an implantable medical device (IMD) 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; 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 a sheath disposed around a distal portion of the IMD, the sheath defining: an inner volume configured to receive the distal portion of the IMD; a distal surface, wherein at least a portion of the distal surface extends along a reference plane offset from the longitudinal axis; and an opening extending from the distal surface to the inner volume, wherein when the IMD is rotated relative to the sheath, the elongated body moves relative to the sheath through the opening and along a reference axis offset from the longitudinal axis to penetrate tissue of the chamber of the heart.

[0204] Example 60: the system of example 59, wherein the elongated body defines a helix within the inner volume of the sheath.

[0205] Example 61 : the system of any of examples 59 or 60, wherein the reference axis is orthogonal to the reference plane.

[0206] Example 62: the system of any of examples 59-61, wherein the at least a portion of the distal surface comprises a first surface, wherein the reference plane comprises a first reference plane, wherein the distal surface comprises the first surface and a second surface, and wherein the second surface extends along a second reference plane orthogonal to the longitudinal axis.

[0207] Example 63: the system of any of examples 59-62, wherein at least a portion of the opening is disposed on the at least a portion of the distal surface.

[0208] Example 64: the system of any of examples 59-63, wherein the elongated housing defines a first feature around an outer perimeter of the elongated housing at or around the distal portion of the IMD, wherein the sheath defines a second feature extending around an inner perimeter of the sheath, and wherein the first feature interfaces with the second feature to couple the IMD to the sheath.

[0209] Example 65: the system of example 64, wherein the first feature interfaces with the second feature to allow for rotation of the sheath relative to the IMD.

[0210] Example 66: the system of any of examples 59-65, wherein the elongated body is compressed along the longitudinal axis when an entire length of the elongated body is disposed within the inner volume of the sheath.

[0211] Example 67: the system of example 66, wherein the elongated body defines a straight elongated body in an uncompressed state, and wherein the elongated body defines a helix in a compressed state within the inner volume of the sheath.

[0212] Example 68: the system of any of examples 59-67, wherein the sheath comprises a first sheath defining a proximal end, and wherein the system further comprises: a second sheath configured to retain the IMD, wherein a distal end of the second sheath is configured to interface with the proximal end of the first sheath to inhibit unintended rotation of the first sheath relative to the wall tissue.

[0213] Example 69: the system of example 68, wherein the IMD is configured to freely rotate relative to the second sheath, and wherein the second sheath is configured to interface with the first sheath to inhibit the unintended rotation of the first sheath as the IMD is rotated about the longitudinal axis.

[0214] Example 70: the system of any of examples 68 or 69, wherein the second sheath defines an electrically conductive band extending at least partially around a perimeter of the second sheath, wherein at least a portion of the electrically conductive band is exposed to an external environment surrounding the second sheath.

[0215] Example 71 : the system of example 70, wherein when the IMD is disposed within the second sheath, the electrically conductive band is separated from the IMD.

[0216] Example 72: the system of example 70, wherein when the IMD is disposed within the second sheath, the electrically conductive band is in contact with the IMD.

[0217] Example 73: the system of any of examples 59-72, wherein the opening comprises a first opening, and wherein the sheath further comprises a second opening extending from the distal surface to the inner volume.

[0218] Example 74: the system of example 73, wherein the second opening is radially inward of the first opening on the distal surface of the sheath.

[0219] Example 75: the system of any of examples 73 or 74, wherein the second opening allows for flow of fluid out of the inner volume of the sheath.

[0220] Example 76: the system of any of examples 59-75, wherein the chamber comprises a ventricle of the heart.

[0221] Example 77: a fixation device comprising: an elongated body extending distally from a distal end of an implantable medical device (IMD) along a longitudinal axis; and a sheath disposed around a distal portion of the IMD, the sheath defining: an inner volume configured to receive the distal portion of the IMD; a distal surface, wherein at least a portion of the distal surface extends along a reference plane offset from the longitudinal axis; and an opening extending from the distal surface to the inner volume, wherein when the IMD is rotated relative to the sheath, a distal end of the elongated body moves relative to the sheath through the opening along a reference axis offset from the longitudinal axis and penetrates tissue of a patient.

[0222] Example 78: the fixation device of example 77, wherein the reference axis is orthogonal to the reference plane.

[0223] Example 79: the fixation device of any of examples 77 or 78, wherein the at least a portion of the distal surface comprises a first surface, wherein the reference plane comprises a first reference plane, wherein the distal surface comprises the first surface and a second surface, and wherein the second surface extends along a second reference plane orthogonal to the longitudinal axis.

[0224] Example 80: the fixation device of any of examples 77-79, wherein at least a portion of the opening is disposed on the at least a portion of the distal surface.

[0225] Example 81 : the fixation device of any of examples 77-80, wherein the IMD defines a first feature extending around an outer perimeter of the distal portion of the IMD, wherein the sheath defines a second feature around an inner perimeter of the sheath, and wherein the first feature interfaces with the second feature to couple the IMD to the sheath.

[0226] Example 82: the fixation device of example 81, wherein the first feature interfaces with the second feature to allow for rotation of the sheath relative to the IMD.

[0227] Example 83: the fixation device of any of examples 77-82, wherein the elongated body is compressed along the longitudinal axis when an entire length of the elongated body is disposed within the inner volume of the sheath.

[0228] Example 84: the fixation device of example 83, wherein the elongated body defines a straight elongated body in an uncompressed state, and wherein the elongated body defines a helix in a compressed state within the inner volume of the sheath.

[0229] Example 85: the fixation device of any of examples 77-84, wherein the sheath comprises a first sheath defining a proximal end, and wherein the fixation device further comprises: a second sheath configured to retain the IMD, wherein a distal end of the second sheath is configured to interface with the proximal end of the first sheath to inhibit unintended rotation of the first sheath relative to the wall tissue.

[0230] Example 86: the fixation device of example 85, wherein the IMD is configured to freely rotate relative to the second sheath, and wherein the second sheath is configured to interface with the first sheath to inhibit the unintended rotation of the first sheath as the IMD is rotated about the longitudinal axis.

[0231] Example 87: the fixation device of any of examples 85 or 86, wherein the second sheath defines an electrically conductive band extending at least partially around a perimeter of the second sheath, wherein at least a portion of the electrically conductive band is exposed to an external environment surrounding the second sheath.

[0232] Example 88: a system comprising: a leadless pacemaker (LP) 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 housing, the elongated body defining an electrode at or proximate a distal end of the elongated body; and a sheath disposed around a distal portion of the LP, the sheath defining: an inner volume configured to receive the distal portion of the LP; a distal surface, wherein at least a portion of the distal surface extends along a reference plane offset from the longitudinal axis; and an opening extending from the distal surface to the inner volume, wherein when the LP is rotated relative to the sheath, the distal end of the elongated body moves relativeto the sheath through the opening along a reference axis offset from the longitudinal axis to penetrate tissue of the chamber of the heart.

[0233] Example 89: the system of example 88, wherein the reference axis is orthogonal to the reference plane.

[0234] Example 90: the system of any of examples 88 or 89, wherein the at least a portion of the distal surface comprises a first surface, wherein the reference plane comprises a first reference plane, wherein the distal surface comprises the first surface and a second surface, and wherein the second surface extends along a second reference plane orthogonal to the longitudinal axis.

[0235] Example 91 : the system of any of examples 88-90, wherein at least a portion of the opening is disposed on the at least a portion of the distal surface.

[0236] Example 92: the system of any of examples 88-91, wherein the housing defines a first feature around an outer perimeter of the elongated housing at or around the distal portion of the LP, wherein the sheath defines a second feature extending around an inner perimeter of the sheath, and wherein the first feature interfaces with the second feature to couple the LP to the sheath.

[0237] Example 93 : the system of example 92, wherein the first feature interfaces with the second feature to allow for rotation of the sheath relative to the LP.

[0238] Example 94: the system of any of examples 88-93, wherein the elongated body is compressed along the longitudinal axis when an entire length of the elongated body is disposed within the inner volume of the sheath.

[0239] Example 95: the system of example 94, wherein the elongated body defines a straight elongated body in an uncompressed state, and wherein the elongated body defines a helix in a compressed state within the inner volume of the sheath.

[0240] Example 96: the system of any of examples 88-95, wherein the sheath comprises a first sheath defining a proximal end, and wherein the system further comprises: a second sheath configured to retain the LP, wherein a distal end of the second sheath is configured to interface with the proximal end of the first sheath to inhibit unintended rotation of the first sheath relative to the wall tissue.

[0241] Example 97: the system of example 96, wherein the LP is configured to freely rotate relative to the second sheath, and wherein the second sheath is configured tointerface with the first sheath to inhibit the unintended rotation of the first sheath as the LP is rotated about the longitudinal axis.

[0242] Example 98: the system of any of examples 96 or 97, wherein the second sheath defines an electrically conductive band extending at least partially around a perimeter of the second sheath, wherein at least a portion of the electrically conductive band is exposed to an external environment surrounding the second sheath.

[0243] Example 99: the system of any of examples 88-98, wherein the opening comprises a first opening, and wherein the sheath further comprises a second opening extending from the distal surface to the inner volume.

[0244] Example 100: the system of example 99, wherein the second opening is radially inward of the first opening on the distal surface of the sheath.

[0245] Example 101 : the system of any of examples 99 or 100, wherein the second opening allows for flow of fluid out of the inner volume of the sheath.

[0246] Example 102: the system of any of examples 88-101, wherein the chamber comprises a ventricle of the heart.

[0247] Example 103: a system comprising: an implantable medical device (IMD) 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 fixation feature disposed on the distal end of the IMD, the fixation feature being configured to affix the distal end of the elongated housing to wall tissue of the chamber of the heart; and an elongated body disposed within the elongated housing around the proximal end of the elongated housing, wherein the elongated body defines an electrode at or proximate to a distal end of the elongated body, wherein in response to rotation of the elongated housing about the longitudinal axis, the elongated body is configured to extend out of the elongated housing and penetrate the wall tissue.

[0248] Example 104: the system of example 103, wherein the elongated body defines a helix within the elongated housing, and wherein the elongated body defines a straight body outside of the elongated housing.

[0249] Example 105: the system of any of examples 103 or 104, wherein when the fixation feature and the elongated body penetrates the wall tissue, the elongated housing is substantially parallel to a surface of the wall tissue.

[0250] Example 106: the system of any of examples 103-105, wherein the fixation feature comprises one or more of: one or more tines; one or more barbs; one or more ledges; or one or more scoops.

[0251] Example 107: the system of any of examples 103-106, wherein the elongated housing defines an opening, wherein the elongated body is configured to extend out of the elongated housing through the opening.

[0252] Example 108: the system of example 107, wherein the opening is at a same circumferential position around an outer perimeter of the elongated housing as the fixation feature.

[0253] Example 109: a method comprising: inserting an implantable medical device (IMD) within a chamber of a heart, the IMD comprising: an elongated housing extending from a proximal end to a distal end along a longitudinal axis; a fixation feature disposed on the distal end of the IMD; and an elongated body disposed within the elongated housing around the proximal end of the elongated housing, wherein the elongated body defines an electrode at or proximate to a distal end of the elongated body, affixing the fixation feature of the IMD to wall tissue of the chamber; rotating the elongated housing of the IMD about the longitudinal axis to advance the elongated body out of the elongated housing and cause the distal end of the elongated body to penetrate the wall tissue; and delivering cardiac pacing signals from the IMD to the wall tissue via the electrode.

[0254] Example 110: the method of example 109, wherein affixing the fixation feature of the IMD to the wall tissue comprises: orienting the IMD relative to a surface of the wall tissue in a first orientation, wherein when the IMD is in the first orientation, the longitudinal axis is orthogonal to the surface of the wall tissue; affixing the fixation feature to the surface of the wall tissue; and rotating the IMD from the first orientation to a second orientation, wherein when the IMD is in second orientation, the longitudinal axis is parallel to the surface of the wall tissue.

[0255] Example 111 : the method of any of examples 109 or 110, wherein the elongated body defines a helix within the elongated housing, and wherein the elongated body defines a straight body outside of the elongated housing.

[0256] Example 112: the method of any of examples 109-111, wherein the fixation feature comprises one or more of: one or more tines; one or more barbs; one or more ledges; or one or more scoops.

[0257] Example 113: the method of any of examples 109-112, wherein the elongated housing defines an opening, wherein the elongated body is configured to exit the elongated housing through the opening.

[0258] Example 114: the method of example 113, wherein the opening is at a same circumferential position around an outer perimeter of the elongated housing as the fixation feature.

[0259] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A system comprising: an implantable medical device (IMD) 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; 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 a sheath disposed around a distal portion of the IMD, the sheath defining: an inner volume configured to receive the distal portion of the IMD; a distal surface, wherein at least a portion of the distal surface extends along a reference plane offset from the longitudinal axis; and an opening extending from the distal surface to the inner volume, wherein when the IMD is rotated relative to the sheath, the elongated body moves relative to the sheath through the opening and along a reference axis offset from the longitudinal axis to penetrate tissue of the chamber of the heart.

2. The system of claim 1, wherein the elongated body defines a helix within the inner volume of the sheath.

3. The system of any of claims 1 or 2, wherein the reference axis is orthogonal to the reference plane.

4. The system of any of claims 1-3, wherein the at least a portion of the distal surface comprises a first surface, wherein the reference plane comprises a first reference plane, wherein the distal surface comprises the first surface and a second surface, and wherein the second surface extends along a second reference plane orthogonal to the longitudinal axis.

5. The system of any of claims 1-4, wherein the elongated housing defines a first feature around an outer perimeter of the elongated housing at or around the distalportion of the IMD, wherein the sheath defines a second feature extending around an inner perimeter of the sheath, and wherein the first feature interfaces with the second feature to couple the IMD to the sheath.

6. The system of any of claims 1-5, wherein the elongated body is compressed along the longitudinal axis when an entire length of the elongated body is disposed within the inner volume of the sheath.

7. The system of claim 6, wherein the elongated body defines a straight elongated body in an uncompressed state, and wherein the elongated body defines a helix in a compressed state within the inner volume of the sheath.

8. The system of any of claims 1-7, wherein the sheath comprises a first sheath defining a proximal end, and wherein the system further comprises: a second sheath configured to retain the IMD, wherein a distal end of the second sheath is configured to interface with the proximal end of the first sheath to inhibit unintended rotation of the first sheath relative to the wall tissue.

9. The system of claim 8, wherein the second sheath defines an electrically conductive band extending at least partially around a perimeter of the second sheath, wherein at least a portion of the electrically conductive band is exposed to an external environment surrounding the second sheath.

10. The system of any of claims 1-9, wherein the opening comprises a first opening, and wherein the sheath further comprises a second opening extending from the distal surface to the inner volume.

11. A system comprising: an implantable medical device (IMD) 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 fixation feature disposed on the distal end of the IMD, the fixation feature being configured to affix the distal end of the elongated housing to wall tissue of the chamber of the heart; and an elongated body disposed within the elongated housing around the proximal end of the elongated housing, wherein the elongated body defines an electrode at or proximate to a distal end of the elongated body, wherein in response to rotation of the elongated housing about the longitudinal axis, the elongated body is configured to extend out of the elongated housing and penetrate the wall tissue.

12. The system of claim 11, wherein the elongated body defines a helix within the elongated housing, and wherein the elongated body defines a straight body outside of the elongated housing.

13. The system of any of claims 11 or 12, wherein when the fixation feature and the elongated body penetrates the wall tissue, the elongated housing is substantially parallel to a surface of the wall tissue.

14. The system of any of claims 11-13, wherein the fixation feature comprises one or more of one or more tines; one or more barbs; one or more ledges; or one or more scoops.

15. The system of any of claims 11-14, wherein the elongated housing defines an opening, wherein the elongated body is configured to extend out of the elongated housing through the opening.

Images