Implantable leadless pacemaker with extendable electrode arrangement

Abstract

An implantable leadless pacemaker (1) is described to include a housing (3), accommodating an energy source (5) and a pacing circuitry (7), and a header (9) including an electrode arrangement (11). The header is attached to the housing such as to be rotatable relative to the housing around a Z-axis. The electrode arrangement comprises an elongate electrode arm (13) with an electrode (15) being provided at a distal end of the electrode arm and with a feedthrough (17) being provided at a proximal end of the electrode arm for connecting the electrode arm with the pacing circuitry. The header comprises a flattish cavity (19) extending in a XY-plane orthogonal to the Z-axis. The header is configured such that, upon rotating the header relative to the housing, the electrode arrangement is displaced within the cavity between a first configuration in which at least a proximal part (21) of the electrode arm is wound up in the XY-plane within the cavity and a second configuration in which at least a distal part (23) of the electrode arm is ejected from the cavity through an opening (25) in the header such as to extend beyond the header in an extension direction parallel to the Z-axis.

Description

[0001] Applicant: BIOTRONIK SE & Co. KG

[0002] Our Reference: 24.175P-WO

[0003] Date: 12.01.2026

[0004] IMPLANTABLE LEADLESS PACEMAKER WITH EXTENDABLE ELECTRODE ARRANGEMENT

[0005] The present invention relates to an implantable leadless pacemaker (ILP) having a specific electrode arrangement. Furthermore, the invention relates to a method for implanting such ILP.

[0006] Miniaturized pacemakers have been developed with a housing being small enough to be implanted directly into a heart chamber of a patient. In contrast to conventional pacemakers, such ILPs (also referred to as intracardiac pacemakers) do not require a long lead for connecting a subcutaneously implanted housing accommodating a battery and a pacing circuitry with an electrode to be implanted at an implantation site at or in a patient’s heart. Existing ILPs comprise an electrode arranged at an outer surface of a housing accommodating the battery and circuitry, such electrode being in superficial contact with adjacent cardiac tissue upon being implanted in a heart chamber.

[0007] Conduction system pacing (CSP) has been developed as a superior method for pacing the heart, offering improved clinical outcomes compared to traditional right ventricular pacing. CSP leads to more natural, coordinated, and efficient heart contractions. It includes both left bundle branch area pacing (LBBAP) and His bundle pacing (HBP).

[0008] One challenge with CSP is that pacing targets are located relatively deep within the septal tissue (typically ~8 to 20 mm). To reach these targets, traditional pacing leads are pushed into the septum while being rapidly rotated, which rotates a distal screw and allows the lead to penetrate deep into the septum.Recently, implantable leadless pacemakers have become increasing popular for pacing due to their minimally invasive nature and reduced risk of infection. However, they are currently not suitable for CSP. ILPs have electrodes near the body of the ILP device, and the ILP device body is too large in diameter for deep septal implantation. Therefore, it is impossible to reach the deep targets required for CSP with today’s ILP systems.

[0009] Challenges with designing an ILP system with an electrode that can penetrate into the deep septal area are for example: 1) achieving this with a minimal increase in the ILP implant size (particularly the device’s diameter), and 2) keeping the system easy for a physician to use and implant. It is critical that the implant diameter stays below a predefined upper limit of, in many applications, around 7 mm to remain competitive and to minimize the required diameter of the introducer sheath. Additionally, a depth of the electrode in the septum should be adjustable at the time of implantation to enable conduction system capture in a variety of anatomies. Finally, the electrode should be retracted during implantation so that an overall length of the ILP is minimized, enabling it to make necessary turns during delivery from the femoral vein or, in some cases, jugular vein to the septal wall of the heart.

[0010] There appears to be currently no leadless pacemaker suitable for conduction system pacing. Conduction system pacing can only be done with a traditional leaded pacemaker system. This means that physicians must choose between the advantages of an ILP for their patients such as being less invasive, inducing less risk of infection, etc. and the advantages of CSP such as enabling more physiological, coordinated and efficient heart contractions reducing a risk of pacing-induced cardiomyopathy and a risk of heart failure (HF) hospitalizations for HF patients.

[0011] The applicant of the present applicant described in a prior US provisional application 63 / 728,706 an ILP, wherein a tine-based sleeve is used to mechanically position a tip electrode at deeper depths by screwing said sleeve into different, adjustable positions. It is to be noted that the electrode arrangement described in the present application may apply characteristics and / or functionalities described in the prior application in a similar manner. Accordingly, the content of the cited prior application shall be incorporated herein in its

[0012] 24.175P-WO / 12.01.2026entirety by reference.

[0013] There may be a need for an improved implantable leadless pacemaker which at least partly overcomes one or more of the above mentioned deficiencies of conventional approaches. Particularly, there may be a need for an ILP which may enable applying CSP techniques by simply, reliably and / or adjustably accessing regions deeply within cardiac tissue for establishing an electric contact to such regions. Therein, the ILP should be sufficiently small for enabling simple implantation in a heart chamber. Furthermore, the ILP should enable simple and precisely positioned insertion of an electrode deep within cardiac tissue. Additionally, there may be a need for an improved method for implanting the proposed ILP.

[0014] Such needs may be met with the subject matter of the independent claims. Advantageous embodiments are defined in the dependent claims as well as in the corresponding specification and figures.

[0015] According to a first aspect of the present invention, an implantable leadless pacemaker (intracardiac pacemaker) is proposed to include a housing accommodating an energy source and a pacing circuitry, and a header including an electrode arrangement. Therein, the header is attached to the housing such as to be rotatable relative to the housing around a Z-axis (e.g. the longitudinal axis of the ILP). The electrode arrangement comprises an elongate electrode arm with an electrode being provided at a distal end of the electrode arm and electrically connected with the pacing circuitry. The header comprises a flatfish cavity extending in a XY-plane orthogonal to the Z-axis. The header is configured such that, upon rotating the header relative to the housing, the electrode arrangement is displaced within the cavity between a first configuration in which at least a proximal part of the electrode arm is wound up in the XY-plane within the cavity and a second configuration in which at least a distal part of the electrode arm is ejected from the cavity through an opening in the header such as to extend beyond the header in an extension direction parallel to the Z-axis.

[0016] According to a second aspect of the present invention, a method for implanting the proposed implantable leadless pacemaker is described. The method comprises at least the following steps, preferably in the indicated order:

[0017] 24.175P-WO / 12.01.2026positioning the pacemaker with its header adjacent to tissue at an implantation site, fixing the pacemaker at the tissue, and

[0018] rotating the housing of the pacemaker relative to the header such as to displace the electrode arrangement from the first configuration to the second configuration to thereby successively eject the distal part of the electrode arm beyond the header and introduce it into the tissue.

[0019] Ideas underlying embodiments of the present invention may be interpreted as being based, inter alia, on the following observations and recognitions.

[0020] Briefly summarized in a non-limiting manner, embodiments of the present invention relate to an improved implantable leadless pacemaker which is specifically adapted for being used in conductive system pacing. For such purpose, the proposed ILP comprises an electrode arrangement included in a header at the ILP housing, wherein the electrode arrangement includes an extendable elongate electrode arm. Therein, the header comprises a flattish cavity and at least parts of the electrode arm are comprised in this cavity. Particularly, a proximal part of the electrode arm may be accommodated within the cavity in a first configuration, in which the respective part of the electrode arm is arranged in a wound up manner. Accordingly, in such first configuration, a major portion or even an entirety of the electrode arrangement may be included and wound up in the cavity. Thus, in the first configuration, the entire ILP including the electrode arrangement may be provided in a very space-saving manner such that it may be simple to transfer the ILP to an implantation site using an implantation procedure with a catheter similar to conventional implantation procedure approaches. Upon being positioned at the implantation site, the electrode arrangement may then be ejected from the cavity of the header. For such purpose, the header is configured for being rotated relative to the housing of the ILP and for, as a result of such relative rotation, ejecting at least a distal part of the electrode arm from the cavity through an opening in the header in a direction towards adjacent cardiac tissue at the implantation site. Accordingly, the distal part of the electrode arm together with an electrode provided at a distal end of the electrode arm may be pierced into the cardiac tissue. Therein, a depth at which the electrode is finally located may be suitably set by rotating the ILP housing relative to the header into a respective suitable orientation in order to thereby eject the distal part of

[0021] 24.175P-WO / 12.01.2026the electrode arm away from the distal end surface of the housing down to the intended depth.

[0022] Within the frame of the application the term “the electrode is arranged in a wound up manner” or “the electrode arm is wound-up in the XY plane” is to be understood as the electrode arm is wound up or coiled in basically planar plane. The electrode may be wound up in circles, a circle or at least a part of a circle, in particular between 0.5 times and 1.5 times of a full circle.

[0023] In the first configuration (e.g. the retracted configuration), a major portion or even an entirety of the electrode arrangement (electrode arm comprising the electrode at the distal end) may be included and wound up in the cavity. Consequently, a minor portion or no portion of the electrode arrangement may already extend distally to the header in the first (retracted) configuration. If a minor portion of the electrode arrangement already extends distally to the header in the first configuration, the electrode at the distal end of the electrode may even at least partially pierce the cardiac tissue in the first configuration. In the second configuration (e.g. the erected configuration) the distal part of the electrode arm together with the electrode at the distal end of the electrode arm may be pierced or further pierced into the cardiac tissue.

[0024] The electrode arrangement comprises an elongate electrode arm with an electrode being provided at a distal end of the electrode arm and may be connected via a feedthrough provided at the proximal end or at the proximal portion of the electrode arm with the pacing circuitry. In general, any electrical connection between the pacing circuitry and the electrode at the distal end of the electrode arm may be suitable.

[0025] Therein, the proposed improved ILP may provide for, inter-alia, small overall dimensions as a result of the cavity in the housing accommodating the wound up electrode arm being flatti sh such that the header may have a small size. Furthermore, the proposed improved ILP may provide for simple handling enabling both, a simple implantation procedure similar to conventional leadless pacemaker implantation procedures as well as a simple procedure of extending the electrode arm from its wound up first configuration to its extended second configuration by simply rotating the housing and the header relative to each other.

[0026] 24.175P-WO / 12.01.2026In the following, characteristics of embodiments of the present invention will be described in more detail.

[0027] The proposed ILP shall be implanted into a body of a patient. Therein, the electrode arrangement may be in contact with and, particularly, may be introduced into tissue of the patient such as cardiac tissue at a patient’s heart. Accordingly, the ILP and its electrode arrangement may be dimensioned and may be made with components and materials such as to be compatible with an implantation at an in-body site. Thus, the housing, the header and the electrode arrangement or at least external portions thereof coming into contact with body fluid or body tissue may be made with biocompatible materials such as for example specific plastic materials including e.g. polyetheretherketone (PEEK) and / or specific metal materials including e.g. titanium, iridium, gold or platinum. Furthermore, the housing, the header and the electrode arrangement may be made with outer dimensions being compatible with an intracardiac implantation.

[0028] The housing of the ILP accommodates an energy source such as a battery as well as a pacing circuitry connected to the energy source. The pacing circuitry serves as ILP electronics and is configured for generating electric pacing pulses for pacing cardiac contractions at a patient’s heart. The housing generally encloses an inner volume in a fluid-tight manner. Particularly, the housing is made with a biocompatible material such as titanium or a titanium alloy.

[0029] Similar to the housing, the header may enclose an inner volume forming a cavity in which at least parts of the electrode arrangement may be accommodated. Outer walls of the header may be made with a biocompatible material, particularly with a biocompatible polymer material such as polyetheretherketone (PEEK).

[0030] The header is fixed to the housing such that the housing and the header may be handled as a unity for example during an implantation procedure. Typically, the header is attached to a distal front end side of the housing, i.e. to a side of the housing which faces away from a catheter being used for implanting the ILP and facing into a direction at which the ILP shall

[0031] 24.175P-WO / 12.01.2026be fixed to cardiac tissue. In other words, the header is generally attached to the housing in a manner to be fixed to the housing such as not to be separated from the housing in a distal direction facing away from the housing. At the same time, the header is attached to the housing such as to be rotatable relative to the housing around a Z-axis. Therein, the Z-axis may coincide with the distal direction and with an extension direction in which the elongate housing extends. For example, the header may be fixed to the housing using a constructional component such as a rivet, a bolt or an anchor pin extending along the Z-axis for example at a center of an interface between the front end side of the housing and an adjacent side of the header.

[0032] The header as well as the cavity enclosed therein are shaped such as to be flatfish. In such flatfish shape, the header and the cavity have lateral dimensions in an XY-plane being substantially larger than a height dimension in a Z-direction. Therein, the Z-direction corresponds to a direction of the Z-axis and is orthogonal to the XY-plane. Particularly, the header may have a cylindrical shape with the lateral dimensions corresponding to a diameter of a cylinder and the height dimension corresponding to a height of the cylinder along its center axis. Therein, the lateral dimensions or diameter, respectively of the header should preferably be smaller or same as corresponding dimensions of the housing. For example, with a housing of an ILP typically having a maximum diameter of at most 7 mm, also the header may have at most such maximum diameter. The height of the header may be smaller than its diameter. For example, the height may be between 0.5 mm and 6 mm, preferably between 1 mm and 4 mm. The cavity enclosed in the header may have slightly smaller dimensions than the header itself, for example it may be smaller by between 0.4 mm and 2 mm, depending on a walls thickness of the header’s walls.

[0033] The electrode arrangement comprises an electrode arm and an electrode.

[0034] The electrode arm is elongate and may be similar to a wire. For example, the electrode arm may have cross-sectional dimensions of at least 0.1 mm, preferably at least 0.2 mm, such as to have sufficient stability and / or rigidity, and at most 1.5 mm, preferably at most 0.8 mm, such as to be small enough to be accommodated within a small sized cavity in the header and / or to be easily introduced into cardiac tissue. The electrode arm may have a circular

[0035] 24.175P-WO / 12.01.2026cross-section or a non-circular cross-section like an oval or rectangular cross-section. The electrode arm may have a typical length of at least 10 mm, preferably at least 15 mm, in order to enable sufficiently deep injection of the electrode arm into adjacent cardiac tissue, and at most 40 mm, preferably at most 25 mm, such that it may be wound up into a small sized configuration within the header’s cavity. Furthermore, the electrode arm may be formed as a solid wire or as a tube. Generally, the electrode arm is made with an electrically conductive material such as a metal material. At its proximal end, the electrode arm may be connected to the pacing circuitry of the ILP via a feedthrough between the header and the housing of the ILP.

[0036] The electrode may be a separate component and may be attached to the electrode arm at or close to the distal end of the electrode arm. For example, the electrode may be attached to the electrode arm using techniques such as crimping, welding, soldering, etc. Alternatively, in principle, the electrode may be an integral part of the electrode arrangement and may be formed such as to cover or coat a surface portion of the electrode arm at or close to its distal end. Generally, the electrode may be made with another metal material as compared to the material of the electrode arm. Particularly, the material for the electrode may be selected such as to have a particularly high electric conductivity and / or a low contact resistance upon contacting cardiac tissue. For example, the electrode may be made with a noble metal such as iridium, gold or platinum or alloys or mixtures thereof.

[0037] According to an embodiment, the electrode arm contains a steroid eluting sleeve at the distal portion of the electrode arm, in particular just proximal and adjacent to the electrode. This sleeve may surround a narrowed section of the electrode arm such that the overall electrode arm is isodiametric. The sleeve may be made of a material such as silicon which acts as both a reservoir for the steroid, and through diffusion it elutes the steroid over time.

[0038] As a particular characteristic of the proposed ILP, its header and electrode arrangement are configured such that the electrode arrangement is displaced within the cavity upon the header being rotated relative to the housing. Specifically, such configuration is implemented in a way such that the electrode arrangement may be displaced between a first configuration in which at least a proximal part of the electrode arm is wound such as to be wound up in the

[0039] 24.175P-WO / 12.01.2026XY-plane within the cavity and a second configuration in which such wound arrangement is at least partially unwound and at least a distal part of the electrode arm is erected and is ejected from the cavity through an opening in the header. Accordingly, in the first configuration, the electrode arrangement may be accommodated mainly or entirely within the cavity in the header whereas, in the second configuration, a maj or portion of the electrode arrangement may be ejected from the header and may extend in an extension direction parallel to the Z-axis. Thus, the ejected distal part of the electrode arrangement may pierce into and may be introduced into cardiac tissue arranged adjacent to the distal surface of the ILP and its header.

[0040] According to an embodiment, the header comprises a channel arrangement in which at least the proximal part of the electrode arm is accommodated such as to be slidable along the channel arrangement. The channel arrangement comprises (i) a curved channel portion extending in the XY-plane, (ii) an outlet portion extending parallel to the Z-axis, and (iii) an intermediate portion connecting the curved channel portion and the outlet portion. The header is configured such that, upon rotating the header relative to the housing, the electrode arm is displaced along the channel arrangement between the first and second configurations. Therein, in the first configuration, a major portion of the electrode arrangement including the proximal part is retracted such as to be included in the curved channel portion in a wound up shape and, in the second configuration, a major portion of the electrode arrangement including the distal part is ejected out of the outlet portion such as to extend beyond the header in the extension direction parallel to the Z-axis.

[0041] In other words, the header may comprise a specific channel arrangement having different portions being adapted such that, upon the header being rotated relative to the housing, the electrode arm of the electrode arrangement may slide along the channel arrangement such as to be displaced between the first configuration and the second configuration. The channel arrangement may have cross-sectional dimensions such as a diameter being slightly larger than cross-sectional dimensions or a diameter of the electrode arm to be accommodated therein. The cross-sectional dimensions of the channel arrangement may be constant along an entire extension of the channel arrangement. Alternatively, such cross-sectional dimensions may vary along the extension of the channel arrangement.

[0042] 24.175P-WO / 12.01.2026Particularly, the channel arrangement is elongate and comprises the curved channel portion, the intermediate portion and the outlet portion adjoining each other such as to form a continuous channel. Therein, the channel portion is curved such as to extend in the XY-plane. Accordingly, the proximal part of the electrode arm may be accommodated within this curved channel portion such as to be curved and wound up within the cavity formed by the curved channel portion in the header. Furthermore, the outlet portion is preferably straight and extends parallel to the Z-axis. Accordingly, the portion of the electrode arm extending along the outlet portion of the channel arrangement is set into a straight shape and is oriented in the Z-direction. The intermediate portion interconnects the curved channel portion and the outlet portion and is suitably curved in order to guide the electrode arm extending from its proximal part within the curved channel portion of the channel arrangement to its distal part at or beyond the outlet portion of the channel arrangement.

[0043] According to an embodiment, the electrode arm is made with or made of Nitinol.

[0044] Nitinol is an electrically conductive metal alloy and is superelastic (i.e. highly flexible). Accordingly, the Nitinol electrode arm may electrically conduct pacing pulses from the pacing circuitry, to which it is connected at its proximal end, to the electrode, to which it is connected at its opposite distal end. Furthermore, due to its superelasticity, the Nitinol electrode arm may be wound and wound up into the small cavity within the header without being permanently plastically deformed. Thus, upon being ejected from the cavity, the Nitinol electrode arm may recover into an original elongate straight shape.

[0045] According to an embodiment, the electrode arm comprises an elongate core which is covered with a cover layer of a metal having an electrical conductivity being higher than an electrical conductivity of a material forming the core and / or a radiopacity being higher than a radiopacity of the material forming the core.

[0046] Expressed differently, the electrode arm may comprise a core such as a wire being made with a first material. Such core may form a mechanically flexible support structure. The first material may be a metal material such as e.g. Nitinol. However, in principle, the first material

[0047] 24.175P-WO / 12.01.2026can also be any other elastically bendable material having electrical conductivity or being electrically insulating. An outer surface of the elongate core may then be covered with a metal layer. Therein, the metal may have a higher electrical conductivity than an electrical conductivity of the first material forming the core. Accordingly, the entire electrode arm including the core and the cover layer may have a sufficiently high electrical conductivity in order to conduct pacing pulses from the pacing circuitry to the electrode at the distal end of the electrode arm with minimal energy loss. For example, in case the core is made with Nitinol, the cover may be made with a better conducting material such as gold or platinum. Alternatively or additionally, the cover layer may be made with a material having a higher radiopacity than the material forming the core. Accordingly, due to such radiopaque cover layer, the electrode arm may be seen with a higher visibility for example in x-ray images taken during an implantation procedure. The material forming the cover layer should be biocompatible.

[0048] In an alternative embodiment, the electrode arm may comprise an elongated tube made of a second material and an inner core made of a first material. The core may be a metal having an electrical conductivity being higher than an electrical conductivity of the second material forming the tube surrounding the core and / or a radiopacity being higher than a radiopacity of the second material forming the tube. The tube may be made of Nitinol. In such an embodiment the Nitinol provides the required mechanical features of the electrode arm. The first material may provide the required conductivity and / or radiopacity. This embodiment is basically inverse to the embodiment as described in the paragraphs above.

[0049] According to an embodiment, the electrode arm comprises an elongate tube, an inner volume of which being filled with a reinforcement material providing a higher mechanical stiffness than a material forming the tube.

[0050] In other words, the electrode arm may be provided as a tube-like hollow structure being made with a first material in which a second material is included and serves as reinforcement due to its mechanical stiffness being higher than the one of the material forming the tube. For example, the tube may be formed with Nitinol being highly elastic and bendable. Such Nitinol tube may then be mechanically reinforced at its center by filling the tube with another

[0051] 24.175P-WO / 12.01.2026material having higher rigidity. For example, this other material may be a metal. Particularly, this material may be a metal having high electrical conductivity in order to, additionally, provide for improved electrical conductivity along the electrode arm.

[0052] According to an embodiment, a circumference of the electrode arm is at least partly covered with an electrically insulating layer.

[0053] Expressed differently, a radially inner portion of the electrode arm may be made with an electrically conductive material such as Nitinol or other metal materials whereas a radially outer portion forming an outer layer may be made with an electrically insulating material having a significantly lower electrical conductivity as compared to the material forming the inner portion. For example, the electrically insulating layer may be made with a polymer material such as parylene, polyimide, silicon, or other appropriate biocompatible insulators. The insulating layer may cover a major portion of the circumference of the electrode arm, particularly a portion of the electrode arm apart from the distal part of the electrode arm and the electrode provided at such distal part. Accordingly, such major portion of the circumference of the electrode arm may be electrically insulated against for example adjacent tissue or body fluids such that, inter-alia, no pacing pulses are applied to such tissue or fluid in areas away from the electrode. Accordingly, upon the electrode being precisely positioned at an intended location for example for conductive system pacing, no disturbing pacing is accomplished at areas away from such intended location. All or part of the insulating layer may be embedded with a steroid such as dexamethasone which slowly elutes to minimize inflammation.

[0054] According to an embodiment, the electrode arm is provided with a non-circular crosssection.

[0055] Generally, the electrode arm may be provided with a circular cross section, i.e. with a circular cylindrical shape, in such configuration, the electrode arm may be bent in all lateral directions homogeneously. However, it may be advantageous to provide the electrode arm with a non-circular cross section such as an oval cross-section or a rectangular cross-section. With such non-circular cross section, the electrode arm may be easily bent in a first direction

[0056] 24.175P-WO / 12.01.2026in which it has a smaller cross-sectional dimension whereas it is stiffer in a second direction in which it has a larger cross-sectional dimension. For example, the larger cross-sectional dimension may be 10%, 20%, 30%, 50% or even 100% larger than the smaller cross-sectional dimension. The non-uniformity in bending characteristics may be advantageous in order to, for example, enable bending the electrode arm from the wound up shape upon being in its first configuration into the straight configuration being its second configuration. Consequently, the non-uniformity in bending characteristic, e.g. the orientation of oval cross-section, are selected or orientated in a way to support the bend at the transition from the wound-up shape to the straight shape. However, in its erected second configuration, the electrode arm may benefit from its increased stiffness against bending at least in the second direction.

[0057] According to an embodiment, the opening in the header is arranged at a center of a distal surface of the header facing away from the housing.

[0058] In other words, the position at which the electrode arm may leave the cavity in the header through the opening may be set at a center of the distal surface of the header with which the header comes into contact with adjacent tissue upon being placed at an implantation site. With such central positioning, the electrode arm may be inserted into the tissue in a configuration in which it is centrally and symmetrically with respect to the header’s distal surface and other components such as tines provided thereon. Accordingly, a placement of the ILP and its header at an implantation site may be intuitive with regards to a resulting placement of the electrode at the electrode arrangement being introduced into the tissue for example at a CSP site.

[0059] However, in order to enable such central positioning of the opening in the header and the electrode arm extending through this opening centrally, the channel arrangement generally requires an intermediate portion which is curved in two directions in order to connect the curved channel portion, at its one side, with the outlet portion, at its opposite side. Such double curved channel intermediate portion may be complicated to form and may require the electrode arm to be flexible and bendable in multiple directions.

[0060] 24.175P-WO / 12.01.2026In order to avoid such complications, according to an alternative embodiment, the opening in the header may be arranged offset from a center of a distal surface (e.g. offset from the longitudinal axis of the ILP) of the header facing away from the housing.

[0061] In such alternative embodiment, the opening in the header and the electrode arm extending through this opening are laterally spaced apart from a center of the distal surface of the header. Preferably, the opening is arranged at a distance to the center which is equal or close to a radius of the curved channel portion, i.e. the curved channel portion and the outlet portion discharging at the header’s opening may be arranged at a same distance from the of the distal surface of the header. Accordingly, the intermediate portion connecting the curved channel portion and the outlet portion may not have to be curved in two directions but only in a single direction, thereby possibly simplifying a shape of the intermediate portion and, thus, of the entire channel arrangement as well as potentially reducing bending requirements to the electrode arm.

[0062] According to an embodiment, the ILP further comprises plural elongate bendable tines extending from the header in a distal direction.

[0063] Such tines are generally used for forming a fixing mechanism with which the ILP may be fixed at cardiac tissue. Particularly, the tines may be made with elongate, narrow Nitinol stripes which may be fixed at or close to a distal surface of the housing or of the header of the ILP and which, at least in partial portions thereof, extend in a distal direction away from the ILP. For example, the tines may be arranged at a common ring and may extend from this ring in a direction away from a plane formed by the ring, wherein the ring may be attached to the ILP at its housing or header. Typically, two, three, four or more tines may be arranged at the ring at equidistant intervals.

[0064] During a catheter procedure, the ILP together with its tines may be included in a sheath of the catheter with the tines being bent into a configuration in which their tip ends are directed in the distal direction. For fixing the ILP at the cardiac tissue at the implantation site, the ILP may be pushed out of the catheter sheath towards the cardiac tissue, thereby introducing the tip ends of the tines into the tissue, with the tines subsequently bending into their original

[0065] 24.175P-WO / 12.01.2026bent configuration. The ILP may then be fixed to the cardiac tissue via the tines engaging with the tissue.

[0066] According to an embodiment, the ILP further comprises at least one engagement structure arranged at a distal surface of the header facing away from the housing. Therein, the engagement structure is configured for promoting an engagement between the header and tissue at which the header abuts with its distal surface upon being implanted at an implantation site such as to at least partly absorb a torque acting onto the header.

[0067] In other words, the ILP may comprise specific engagement structures via which an engagement between the header of the ILP, on the one side, and adjacent cardiac tissue, on the other side, may be established or may be supported. Such engagement structures may protrude from the header in the distal direction, i.e. in the Z-direction. For example, an engagement structure may be embodied as a fin, pin, protuberance, etc. which may be pressed into adjacent cardiac tissue upon the ILP being fixed for example via its tines at the implantation site at the tissue. Alternatively, an engagement structure may be embodied as a recess, hole, etc. such that adjacent cardiac tissue may extend into the recessed engagement structure upon the ILP being pulled towards the tissue when fixed at the implantation site. Plural engagement structures may be distributed along the distal surface of the header. Preferably, the engagement structures are arranged at a substantial distance to a center of the distal surface, for example close to a circumference of the header. Due to such positioning and an established engagement between the engagement structures and the adjacent cardiac tissue, forces and particularly torques acting onto the header upon for example the housing being rotated relative to the header for displacing the electrode arrangement from its first configuration to its second configuration may be at least partially absorbed by the engagement structures. This may help avoiding excessive forces or torques being applied for example to the tines which, on the one hand, generally are optimized for pulling the ILP parallel to the distal direction towards the cardiac tissue upon being implanted but which, on the other hand, are generally not optimized for absorbing torques in a direction parallel to a surface of the tissue.

[0068] 24.175P-WO / 12.01.2026According to an embodiment, the housing comprises a hitch at its proximal side, the hitch being configured for an engagement with a catheter such as to transmit a rotation motion of the catheter or a torque translating structure of a catheter onto the housing.

[0069] In other words, a hitch may protrude from the housing of the ILP at its proximal end such that a catheter or a torque translating structure of a catheter interacting with the ILP during an implantation procedure may engage with such hitch. Therein, the catheter and / or a catheter handling mechanism may be configured such that the catheter or parts thereof may be rotated in a controllable manner and such rotation may then be transmitted to the housing of the ILP due to an interaction of the hitch with the rotating part of the catheter. Accordingly, in an implantation procedure, a physician may suitably rotate the ILP housing by actuating the catheter handling mechanism in order to thereby actuate the header and the electrode arrangement comprised therein for a displacement from its wound up first configuration into its expanded second configuration.

[0070] In the method for implanting the implantable leadless pacemaker according to an embodiment of the second aspect of the invention, the ILP may first be positioned at an implantation site with its header being arranged adjacent to tissue at a heart chamber. For such purpose, the ILP may be transported to the implantation sites using a catheter. Upon being correctly positioned, the pacemaker may then be fixed to the tissue. For example, the tines at the distal side of the header may be introduced into the tissue and may pull the ILP towards the surface of the tissue. Subsequently, the housing of the ILP may be suitably rotated relative to the header in order to thereby displace the electrode arrangement within the header from its wound up first configuration in an uncoiling motion to its second configuration, thereby successively ejecting the distal part of the electrode arm through the opening in the header and beyond the distal surface of the header. Thereby, the electrode at the distal end of the electrode arm may be pushed deep into the adjacent cardiac tissue until reaching a suitable depth for conduction system pacing.

[0071] It shall be noted that possible features and advantages of embodiments of the invention are described herein with respect to various embodiments of an ILP including a header and an electrode arrangement and with respect to a method for implanting such ILP. One skilled in

[0072] 24.175P-WO / 12.01.2026the art will recognize that the features may be suitably transferred from one embodiment or implementation to another and features may be modified, adapted, combined and / or replaced, etc. in order to come to further embodiments of the invention.

[0073] In the following, advantageous embodiments of the invention will be described with reference to the enclosed drawings. However, neither the drawings nor the description shall be interpreted as limiting the invention.

[0074] Fig. 1 shows a perspective, partially transparent view of an ILP according to an embodiment of the present invention.

[0075] Figs. 2A-C show side views of an ILP with a centered electrode arrangement in a partly extended and a fully extended configuration and a top view onto a distal front end side of the header of the ILP according to an embodiment of the present invention.

[0076] Figs. 3 A-C show side views of an ILP with an electrode arrangement arranged offset from a center in a partly extended and a fully extended configuration and a top view onto a distal front end side of the header of the ILP according to an embodiment of the present invention.

[0077] Fig. 4 shows a cross-sectional view of an electrode arrangement for an ILP according to an embodiment of the present invention.

[0078] The figures are only schematic and not to scale. Same reference signs refer to same or similar features.

[0079] Fig. 1 shows an implantable leadless pacemaker 1. The ILP 1 comprises a housing 3 accommodating an energy source 5 and a pacing circuitry 7. The energy source 5 is a battery providing electricity to the pacing circuitry 7 for generating electric cardiac pacing pulses. Additionally, the ILP 1 comprises a header 9 including an electrode arrangement 11.

[0080] 24.175P-WO / 12.01.2026The header 9 is attached to the housing 3 such as to be rotatable relative to the housing 3 around a Z-axis. The header 9 has a flattish cylindrical shape with a diameter corresponding to a diameter of the housing 3 and a height being substantially smaller than the diameter. Accordingly, the header 9 does not increase an overall diameter of the ILP 1 and does only slightly increase an overall height of the ILP 1 as compared to a conventional ILP with a non-rotatable header.

[0081] In the example shown, the header 9 is arranged at the housing 3 along an interface 63 and is fixed to the housing 3 via a pivot anchor 59 located centrally within this interface 63. Accordingly, the header 9 and the housing 3 may not be separated from each other in the Z-direction but may rotate relative to each other in a rotation direction 61 around the Z-axis.

[0082] The electrode arrangement 11 comprises an elongate electrode arm 13 and an electrode 15 being provided at the electrode arm 13 at a distal end thereof. At its proximal end, the electrode arm 13 is connected via a feedthrough 17 to the pacing circuitry 7. The electrode arm 13 may comprise or may consist of a Nitinol wire. The electrode 15 may be provided as a separate component comprising or consisting of for example an iridium alloy and being attached to the electrode arm 13 for example by crimping or laser welding.

[0083] The header 9 comprises a flattish cavity 19 extending in the XY-plane orthogonal to the Z-axis. In the example shown, the flattish cavity 19 comprises a channel arrangement 27 in which a proximal part 21 of the electrode arm 13 is accommodated such as to be slidable along the channel arrangement 27. The channel arrangement 27 comprises a curved channel portion 29 extending in the XY-plane, an outlet portion 31 extending parallel to the Z-axis and an intermediate portion 33 connecting the curved portion 29 and the outlet portion 31.

[0084] Specifically, the header 9 with its channel arrangement 27 is configured such that, upon rotating the header 9 relative to the housing 3 in or against the rotation direction 61, the electrode arm 13 is displaced along the channel arrangement 27 between a first configuration and a second configuration, or vice versa. In the first configuration, at least the proximal part 21 of the electrode arm 13 is retracted such as to be included in the curved channel portion 29 in a wound up shape. Upon turning the header 9 relative to the housing 3, the electrode

[0085] 24.175P-WO / 12.01.2026arm 13 is displaced within the channel arrangement 27 such as to finally approach its second configuration in which at least the distal part 23 of the electrode arm 13 is uncoil and ejected out of the outlet portion 31 by being pushed through an opening 25 in the header 9 at which the outlet portion 31 discharges to an environment. Accordingly, in the second configuration, a major portion of the electrode arrangement 11 including the distal part 23 is ejected from the header 9 such as to extend in a distal direction 65 parallel to the Z-axis beyond a distal surface 45 of the header 9.

[0086] It may possible to put the device in any rotation state between the first position and second position. This allows the electrode 15 to be optimally placed at a depth where CSP pacing has acceptable thresholds. In an embodiment it is not possible when rotating to first position to rotate the housing with respect to the header beyond the first position. Like wise, it is not possible when rotating to second position to rotate beyond second position. The feedthrough 17 which is attached to the proximal end of the electrode arm 13 is cannot move into the intermediate portion 33 of the channel, and likewise it cannot move beyond the end of the channel 29. In some embodiments there are structures to place to protect the feedthrough from damage due to over torquing (not shown).

[0087] The ILP 1 and its header 9 further comprise plural tines 47 for attaching the ILP 1 to cardiac tissue 53 (only schematically indicated in Fig. 1). The tines 47 are provided as elongate curved and bendable Nitinol stripes extending from the header 9 in the distal direction 65 towards the cardiac tissue 53. In the example shown, four tines 47 are arranged equidistantly along a circumference of the header 9.

[0088] The ILP 1 further comprises plural engagement structures 49 arranged at the distal surface 45 of the header 9 and facing away from the housing 3 in the Z-direction. In the example shown, the engagement structures 49 are implemented as fins protruding from the distal surface 45 of the header 9 in the Z-direction towards the tissue 53. Accordingly, such fins may promote an engagement or friction between the header 9 and the tissue 53 at which the header 9 abuts with its distal surface 45 upon being implanted at an implantation site. Due to such engagement, a torque acting onto the header 9 for example upon the header being

[0089] 24.175P-WO / 12.01.2026rotated relative to the housing 3 may be at least partly absorbed at the engagement structure 49 instead of acting onto the tines 47.

[0090] Furthermore, the ILP 1 comprises a hitch 55 protruding at a proximal surface 67 of the housing 3. Such hitch 55 may engage with a catheter 57 such as to transmit a rotation motion of the catheter 57 onto the housing 3.

[0091] As shown in Figs. 2A-C, the header 9 may be configured such that its opening 25 is arranged at a center of the distal surface 45 of the header 9 and therefore its electrode arm 13 is ejected centrally from the header 9. Therein, Fig. 2A shows a configuration in which the electrode arrangement 11 is retracted towards its first configuration, i.e. the electrode arm 13 is ejected from the header 9 at most to a minor extend. Fig. 2B shows a configuration in which the electrode arrangement 11 is extended towards its second configuration, i.e. the electrode arm 13 is ejected from the header 9 to a major extend. Fig. 2C shows a top view onto the distal surface 45 of the header 9. Therein, the channel arrangement 27 comprises the curved channel portion 29 extending close to a circumference of the header 9 and further comprises the outlet portion 31 with its opening 25 positioned at the center of the distal surface 45. Accordingly, the intermediate portion 33 connecting the curved channel portion 29 with the outlet portion 31 is formed in a double-curve in which it bends out of the XY-plane towards the Z-direction and in which it further bends from a track close to the circumference of the header 9 towards the centred opening 25.

[0092] As an alternative to such embodiment, Figs. 3A-C show an ILP 1 comprising a header 9 at which the opening 25 of the channel arrangement 27 is arranged offset from a center of the distal surface 45. Accordingly, in such embodiment, the outlet portion 31 and the opening 25 may be arranged at a same or similar radial distance from the center as the curved channel portion 29. Therefore, the intermediate portion 33 may be formed in a single-curve in which it bends only from the XY-plane towards the Z-direction. Accordingly, the electrode arm 13 included in the channel arrangement 27 may need to bend only in one direction upon being ejected from the header 9. Particularly in such embodiment, it may be advantageous to provide the electrode arm 13 with a non-circular cross-section such as to increase its rigidity

[0093] 24.175P-WO / 12.01.2026in a direction in which the electrode arm 13 does not have to bend upon ejecting from the cavity 19 in the header 9.

[0094] Fig. 4 shows a cross-section of an exemplary electrode arm 13 with a proximal end being connected to the feedthrough 17 and a distal end being provided with the electrode 15. Therein, the electrode arm 13 comprises an elongate tube 39 consisting for example of Nitinol. An inner volume 69 of the tube 39 is filled with a reinforcement material 41 providing a higher mechanical stiffness than a material forming the tube 39. A circumferential surface of the tube 39 is at least partly covered with an electrically insulating layer 43. The electrode 15 may be crimped or welded to the tube 39 and may electrically contact the tube 39.

[0095] As an alternative (not shown), the electrode arrangement may comprise a core formed for example by the tube or by a solid wire consisting of a first material having relatively low electrical conductivity and / or a low radiopacity. Such core may then be covered with a cover layer of a material having a higher electrical conductivity and / or a higher radiopacity.

[0096] It is to be noted that, while being advantageous, neither the tube-shape nor the reinforcement material 41 nor the insulating layer 43 nor the cover layer 37 are necessary features of the electrode arm 13. Instead, the electrode arm 13 may only comprise one or some of these features or may, in a most simple implementation, be made with a simple highly bendable wire such as a Nitinol wire.

[0097] In the following paragraphs, possible features, characteristics and advantages of embodiments of the electrode arrangement presented herein shall be described once more with a different wording:

[0098] This disclosure describes an ILP 1 suitable for CSP. A key feature that makes the ILP suitable for CSP is its electrode 15, which is located on an extendable / retractable arm 13. This arm 13 can be extended deep into a septum by twisting a body or housing 3 of the ILP during an implant procedure and retracted by twisting in an opposite direction.

[0099] 24.175P-WO / 12.01.2026A significant advantage of the proposed ILP is that it achieves the extendable / retractable electrode arm 13 with minimal additional implant volume and no increase in the ILP diameter compared to a conventional ILP. This is accomplished by designing the extendable / retractable electrode arm 13 to make turns within the device header 9, allowing it to coil in a cavity 19 perpendicular to the axis of extension when retracted.

[0100] In a preferred embodiment, the electrode arm 13 is made of Nitinol which is ~0.2 mm to 0.8 mm in diameter. Nitinol is chosen because it is superelastic, allowing it to make the tight curves in the header during extension / retraction without permanently deforming. Nitinol has a resistivity of approximately 82 p -cm. Therefore, a 0.5 mm diameter Nitinol arm fully extended to 20 mm will have a theoretical electrical resistance of only about 0.08 . This is an insignificant series resistance for pacing systems. Further, the conductivity can be improved (if desired) by plating the electrode arm with gold or platinum, which also helps visualization during implant by making the electrode arm much more radioopaque. The nitinol arm can be insulated (e.g., coated with parylene, polyimide, silicon, or other appropriate biocompatible insulator) to ensure that only the electrode is in electrical contact with tissue.

[0101] The mechanism for extending and retracting the arm is shown in detail in Figure 1. The device header 9 is attached to the ILP electronics and battery housing 3 via a central pivot anchor 59, allowing the housing 3 to rotate relative to the header 9. The direction of rotation is indicated by 61 in the figure, and an interface between the rotating housing 3 and the fixed header 9 is labeled as 63. Typically, the housing is made of a titanium alloy, and in one embodiment the pivot anchor is also made of a titanium alloy. In one embodiment the pivot anchor is shaped like a small round table and is welded onto the housing. The header material, which can be peek, polyurethane, epoxy, or some other suitable material, completely surrounds the pivot anchor, permanently attaching the header to the housing. However, the pivot anchor and therefore the housing are free to rotate with respect to the header.

[0102] After the ILP is anchored in cardiac septal tissue by the tines 47, the header is held stationary by the tines and preferably by additional anti-rotation features such as small fins 49. Once

[0103] 24.175P-WO / 12.01.2026anchored, but before being released from an implantation catheter, the electrode arm can be extended by rotating the housing via the implantation catheter. It can also be retracted (e.g. if it was extended too far for CSP capture, or if the ILP needs to be repositioned because CSP capture not possible with initial anchor point) by rotating the housing in the opposite direction via the implantation catheter.

[0104] The ILP is fixated via delivery catheter in two steps. One step deploys the tine into the right ventricular septum and the other step provides a controlled rotation of the ILP’s hitch 55. The rotation of the ILP hitch rotates the housing which the hitch is permanently attached to (typically by welding). Rotation of the housing moves an electrical feedthrough 17 in an arc along a slot in the header. A proximal end of the electrode arm is attached to the electrical feedthrough, so as the feedthrough moves in an arc along the slot, the electrode arm advances along the slot in the header. The electrode arm exits the slot in the header and enters a guide channel 27 in the header. The guide channel turns the electrode arm first toward the center axis of the ILP, then up along the central axis (Z-axis in figure 1) and out of the distal end of the ILP header. Because the electrode arm in the preferred embodiment is made of superelastic nitinol, it can make these tight turns without permanently deforming. The result of this mechanism is that rotating the hitch in one direction (e.g., clockwise) extends the electrode arm deeper into the septum, while rotating it in the opposite direction (e.g., counterclockwise) retracts the electrode arm into the ILP header cavity. Through controlled rotation, the electrode arm can achieve any extension between, for example, 5 mm and 20 mm in length.

[0105] The electrode can be IrOx, Platinum Iridium, gold, titanium nitride, so some other appropriate metal or metal alloy. Nitinol is difficult to weld because of its high sensitivity to heat and the Nitinol phase instability. Therefore, in one embodiment, the electrode is attached to the distal end of the Nitinol arm by a mechanical technique such as crimping. Likewise, the attachment of the proximal end of the Nitinol arm to the feedthrough is preferably a mechanical technique such as crimping.

[0106] When the device ships, the electrode arm is preferably fully extended. This ensures that the straight part of the fully extended nitinol electrode arm retains its shape, even when exposed

[0107] 24.175P-WO / 12.01.2026to a wide temperature range during shipment and storage. The device may sit in a warehouse or on a hospital shelf for over a year before use. At the time of implantation, the physician retracts the electrode arm completely before inserting the delivery catheter (with the ILP attached) into the patient. The electrode arm remains retracted during device delivery to the cardiac septum, allowing the ILP to navigate the necessary turns to reach the implant location transvenously.

[0108] Once the ILP is at the desired implant location, which may involve electrical mapping to find the LBBA, the device is anchored into the cardiac tissue similarly to a traditional ILP implantation. After anchoring, the physician can advance the electrode deeper into the septum by rotating the ILP hitch using implant catheter controls on a handle.

[0109] In a preferred embodiment, the header includes a feature to help it stay fixed and resist torque during rotation of the ILP housing. The anchor tines 47 of the ILP are typically oriented to present only their thin edge to counter rotation, which is not very effective at resisting torque forces. The anti-torque feature forming an engagement structure 49 can be thin fins placed radially around the header, which penetrate cardiac tissue during implantation. The fins are oriented so that their broad surface resists torque forces, ensuring that the header and anchor tines, once anchored, do not rotate and damage tissue when the implantation catheter rotates the housing. Alternatively, the anti-rotation feature can be bumps added to the header surface to increase friction at the contact point with cardiac tissue.

[0110] In one embodiment, the turning mechanism in the catheter includes a torque-limiting featuring to prevent over-torquing of the ILP housing, which could cause the header and fixation tines to damage tissue.

[0111] In one embodiment, the electrode arm protrudes from the ILP header at an off-center location. This off-center electrode arm is shown in Fig. 3. The off-center electrode arm simplifies the required turns in header that the electrode arm must make during extension and retraction. Recall that with a centered electrode arm the guide channel first turns the central electrode arm toward the center axis of the ILP in the x-y plane, then it turns it up along the z-axis and out of the distal end of the ILP header. This requires two turns, first to

[0112] 24.175P-WO / 12.01.2026change the path of the electrode arm towards the center of the ILP, then to turn it along the Z-axis. The off-center electrode arm simplifies this to a single turn. The off-center electrode arm only needs to make one turn from the x-y plane to the z-axis. This simplifies the design and makes it easier for the electrode arm (41) to be extended or retracted.

[0113] Features of the ILP proposed herein relate, inter alia, to:

[0114] 1. An ILP with an extendible / retractable electrode arm

[0115] 2. The Electrode arm makes at least one turn in the header, so that when retracted it is stored in a cavity perpendicular to the central axis of the ILP (Z-axis).

[0116] 3. The Electrode arm is extended and retracted by turning the housing while the header is fixed in place.

[0117] 4. An ILP with anti-rotation features on the header to help the header resist torque without tissue damage.

[0118] 5. The Electrode arm is made of nitinol (or gold-plated nitinol)

[0119] 6. The Electrode arm is insulated except for the electrode at its distal tip.

[0120] 7. An implantation catheter that can deploy the tines of the ILP and provide torque to the hitch to extend or retract the electrode arm.

[0121] Advantages of embodiments of the ILP may be, inter alia:

[0122] The proposed ILP is suitable for CSP pacing with minimal added volume to account for the necessary adjustable electrode protrusion. It allows the electrode to be extended into (and retracted from) deep in the septum, without adding significant volume to the ILP. Crucially the ILP radius is not increased at all over a conventional ILP design. And the housing does not need a Z-axis cavity to hold the retracted arm. Instead, the retracted arm makes a tight turn and is stored in the X-Y plane at the base of the header.

[0123] Finally, it should be noted that the term “comprising” does not exclude other elements or steps and the “a” or “an” does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims should not be construed as limiting the scope of the claims.

[0124] 24.175P-WO / 12.01.2026List of Reference Numerals

[0125] I leadless pacemaker

[0126] 3 housing

[0127] 5 energy source

[0128] 7 pacing circuitry

[0129] 9 header

[0130] I I electrode arrangement

[0131] 13 electrode arm

[0132] 15 electrode

[0133] 17 feedthrough

[0134] 19 cavity

[0135] 21 proximal part of the electrode arm 23 distal part of the electrode arm 25 opening in header

[0136] 27 channel arrangement

[0137] 29 curved channel portion

[0138] 31 outlet portion

[0139] 33 intermediate portion

[0140] 35 core

[0141] 37 cover layer

[0142] 39 tube

[0143] 41 reinforcement material

[0144] 43 electrically insulating layer

[0145] 45 distal surface of the header

[0146] 47 tine

[0147] 49 engagement structure

[0148] 53 tissue

[0149] 55 hitch

[0150] 57 catheter

[0151] 59 pivot anchor

[0152] 61 rotation direction

[0153] 24.175P-WO / 12.01.2026interface

[0154] distal direction

[0155] proximal surface of the housing inner volume

[0156] 24.175P-WO / 12.01.2026

Claims

Claims1. An implantable leadless pacemaker (1) including:a housing (3) accommodating an energy source (5) and a pacing circuitry (7), a header (9) including an electrode arrangement (11),wherein the header (9) is attached to the housing (3) such as to be rotatable relative to the housing (3) around a Z-axis,wherein the electrode arrangement (11) comprises an elongate electrode arm (13) with an electrode (15) being provided at a distal end of the electrode arm (13) electrically connected with the pacing circuitry (7),wherein the header (9) comprises a flattish cavity (19) extending in a XY-plane orthogonal to the Z-axis,wherein the header (9) is configured such that, upon rotating the header (9) relative to the housing (3), the electrode arrangement (11) is displaced within the cavity (19) between a first configuration in which at least a proximal part (21) of the electrode arm (13) is wound upin the XY-plane within the cavity (19) and a second configuration in which at least a distal part (23) of the electrode arm (13) is ejected from the cavity (19) through an opening (25) in the header (9) such as to extend beyond the header (9) in an extension direction parallel to the Z-axis.

2. The implantable leadless pacemaker of claim 1,wherein the header (9) comprises a channel arrangement (27) in which at least the proximal part (21) of the electrode arm (13) is accommodated such as to be slidable along the channel arrangement (27),the channel arrangement (19) comprising:- a curved channel portion (29) extending in the XY-plane,- an outlet portion (31) extending parallel to the Z-axis, and- an intermediate portion (33) connecting the curved channel portion (29) and the outlet portion (31),wherein the header (9) is configured such that, upon rotating the header (9) relative to the housing (3), the electrode arm (13) is displaced along the channel arrangement (27) between the first and second configurations, wherein, in the first configuration,24.175P-WO / 12.01.2026a major portion of the electrode arrangement (11) including the proximal part (21) is retracted such as to be included in the curved channel portion (29) in a wound up shape and wherein, in the second configuration, a major portion of the electrode arrangement (11) including the distal part (23) is ejected out of the outlet portion (31) such as to extend beyond the header (9) in the extension direction parallel to the Z- axis.

3. The implantable leadless pacemaker of claim 1,wherein the electrode arm (13) is made with Nitinol.

4. The implantable leadless pacemaker of claim 1,wherein the electrode arm (13) may comprise an elongated tube (37) made of a second material and an inner core (35) made of a firstmaterial.

5. The implantable leadless pacemaker of claim 1,wherein the electrode arm (13) comprises an elongate tube (39), an inner volume (69) of which being filled with a reinforcement material (41) providing a higher mechanical stiffness than a material forming the tube (39).

6. The implantable leadless pacemaker of claim 1,wherein a circumference of the electrode arm (13) is at least partly covered with an electrically insulating layer (43).

7. The implantable leadless pacemaker of claim 1,wherein the electrode arm (13) is provided with a non-circular cross-section.

8. The implantable leadless pacemaker of claim 1,wherein the opening (25) in the header (9) is arranged at a center of a distal surface (45) of the header (9) facing away from the housing (3).24.175P-WO / 12.01.20269. The implantable leadless pacemaker of claim 1,wherein the opening (25) in the header (9) is arranged offset from a center of a distal surface (45) of the header (9) facing away from the housing (3).

10. The implantable leadless pacemaker of claim 1,further comprising plural elongate bendable tines (47) extending from the header (9) in a distal direction (65).

11. The implantable leadless pacemaker of claim 1,further comprising at least one engagement structure (49) arranged at a distal surface (45) of the header (9) facing away from the housing (3),wherein the engagement structure (49) is configured for promoting an engagement between the header (9) and tissue (53) at which the header (9) abuts with its distal surface (45) upon being implanted at an implantation site such as to at least partly absorb a torque acting onto the header (9).

12. The implantable leadless pacemaker of claim 1,wherein the housing (3) comprises a hitch (55) at its proximal side,the hitch (55) being configured for an engagement with a catheter (57) such as to transmit a rotation motion of the catheter (57) or a torque translating structure of the catheter onto the housing (3).

13. A method for implanting the implantable leadless pacemaker of claim 1, the method comprising:positioning the pacemaker (1) with its header (9) adjacent to tissue (53) at an implantation site,fixing the pacemaker (1) at the tissue (53), androtating the housing (3) of the pacemaker (1) relative to the header (9) such as to displace the electrode arrangement (11) from a first configuration to a second configuration to thereby successively eject the distal part (23) of the electrode arm (13) beyond the header (9) and introduce it into the tissue (53).24.175P-WO / 12.01.202614. The method of claim 13,wherein the pacemaker (1) is fixed at the tissue (53) by introducing tines (47) extending from the header (9) of the pacemaker (1) into the tissue (53).

15. The method of claim 13,further comprising setting an introduction depth, at which the electrode (15) is finally arranged within the tissue (53), by suitably rotating the housing (3) of the pacemaker (1) relative to the header (9).24.175P-WO / 12.01.2026

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