WO2022152587A1

WO2022152587A1 - Medical implant, particularly in form of an implantable intracardiac pacemaker, comprising a rotatable anchoring device to allow extraction of the encapsulated medical implant

Info

Publication number: WO2022152587A1
Application number: PCT/EP2022/050028
Authority: WO
Inventors: R. Hollis Whittington
Original assignee: Biotronik Se & Co. Kg
Priority date: 2021-01-15
Filing date: 2022-01-03
Publication date: 2022-07-21

Abstract

The present invention relates to a medical implant (5) comprising: a housing (4), and an anchoring device (1) mounted to the housing (4), wherein the anchoring device (1) comprises at least one anchoring member (20) protruding from the housing (4) and being configured to pierce bodily tissue to anchor the medical implant (5) to said bodily tissue, and a supporting member (3) connected to the at least one anchoring member (20), wherein the anchoring device (1) is mounted to the housing (4) via the supporting member (3). According to the present invention, for explanting the medical implant (5), the housing (4) is configured to be rotated about a rotation axis (z) with respect to the anchoring device (1) when the at least one anchoring member (20) is embedded in said bodily tissue.

Description

MEDICAL IMPLANT, PARTICULARLY IN FORM OF AN IMPLANTABLE INTRACARDIAC PACEMAKER, COMPRISING A ROTATABLE ANCHORING DEVICE TO ALLOW EXTRACTION OF THE ENCAPSULATED MEDICAL IMPLANT

The present invention relates to a medical implant, particularly an implantable intracardiac pacemaker that is configured to be implanted into a chamber of a heart to deliver stimulation. These so-called leadless pacemakers are anchored to tissue inside the heart (myocardium). When implanted, it is advantageous to have a stable fixation technique for the implant that prevents dislodgement and embolization. After implantation, in some cases it may be necessary to remove the device. However, after a while the implanted medical implant is at least partially encapsulated by bodily tissue, which is created around the implant due to natural body reactions. As an important side effect, this physiological process leads to a more secure anchoring of the device but may impede extraction of the device.

Two major anchoring techniques for intracardiac pacemakers are known: (i) a helical fixation, which is a sturdy wire that is threaded into the myocardium (e.g. disclosed in US 2012/0158111 Al and US 2012/0116489 Al), and (ii) tines with a backward bend, which during implantation get stretched for piercing the myocardium (e.g. disclosed in US 2014/0121719 Al).

Helical fixation techniques can be implanted and explanted with a rotational movement to screw the device in or out the myocardium. However, screwing the device into the myocardium during initial implantation can be very dangerous and can lead to a myocardial perforation. Implantation of a tined fixation intracardiac medical device is more secure with lower risk of myocardial perforation compared to a device using a helix fixation. However, when an implanted medical implant with tines needs to be extracted a longitudinal retraction force has to be applied which can be dangerous to the patient due to the forces on the heart tissue and risk of perforation.

Thus, is an objective of the present invention to provide a medical implant, particularly an implantable intracardiac pacemaker, that is improved regarding explanting of the medical implant.

This objective is solved by a medical implant having the features of claim 1. Preferred embodiments of this aspect of the present invention are stated in the sub claims and are described below.

According thereto, claim 1 discloses a medical implant comprising: a housing, and an anchoring device mounted to the housing, wherein the anchoring device comprises at least one anchoring member protruding from the housing and being configured to pierce bodily tissue to anchor the medical implant to said bodily tissue, and a supporting member connected to the at least one anchoring member, wherein the anchoring device is mounted to the housing via the supporting member.

According to the present invention, for explanting the medical implant, the housing is configured to be rotated about a rotation axis with respect to the anchoring device when the at least one anchoring member is embedded in said bodily tissue, particularly without substantial damage to the bodily tissue interacting with the at least one anchoring member, particularly because the anchoring member remains essentially stationary.

According to an embodiment of the medical implant, the supporting member is an annular supporting member.

Furthermore, according to an embodiment of the medical implant, for allowing rotation of the housing about the rotation axis, the supporting member is arranged in a circumferential groove formed in the housing, wherein said at least one anchoring member preferably protrudes out of said groove. According to a further embodiment, the groove is formed in a face side of an end portion of the housing.

Furthermore, according to a preferred embodiment, said groove comprises a circumferential undercut, wherein the supporting member comprises at least one portion, particularly a plurality of portions, engaging behind said undercut so that the anchoring device is secured to the housing with respect to the extension direction of the rotation axis.

According to a preferred embodiment, the undercut is formed by a locking ring inserted into the groove. As a consequence, the remaining free cross section of the groove in which the supporting member can slide in a circumferential direction of the housing comprises the undercut, particularly an L-shape.

Furthermore, according to an embodiment of the medical implant, the medical implant comprises at least one locking member being arranged with respect to the at least one anchoring member so as to temporarily prevent a rotation of the housing with respect to the anchoring device. This allows to have a rigid coupling between the housing and the anchoring device that prevents rotation of the housing with respect to the anchoring device (and vice versa) upon implantation of the medical implant. Particularly, the medical implant can comprise two locking members on either side of the at least one anchoring member. After implantation of the medical implant, the at least one locking member preferably releases the anchoring device so that a rotation of the housing with respect to the anchoring device is possible. The respective locking member can be a solid body being connected to the housing in at least one of: a form-fitting fashion, a force-fitting fashion, by a material bond. Particularly, the locking member can be applied to the medical implant in a non-solid state and is then cured to form a solid locking member.

Particularly, according to an embodiment, for releasing the rotation preventing fixation of the anchoring device to the housing, the at least one locking member is formed out of or comprises a biodegradable material, wherein the biodegradable material is preferably one of: a biodegradable metal alloy, a biodegradable alloy comprising Mg, a biodegradable alloy comprising Fe, a biodegradable alloy comprising Zn, a biodegradable polymer. The biodegradable metal alloy may include magnesium (Mg), iron (Fe) and/or zinc (Zn) as a main alloy component or an alloy component. The main alloy component is the component, whose amount by weight in the alloy is the largest. The main alloy component may amount to more than 50 % by weight, more 70 % by weight, and in particular more than 90 % by weight. In one embodiment, the main alloy component is Mg. Suitable alloys are Magnesium Zinc Calcium alloys, which are disclosed in documents WO 2014/001321 Al and WO 2014/001241 Al, Magnesium Aluminum alloys as disclosed in document WO 2014/001240 Al, or Magnesium Aluminum Zinc alloys as disclosed in document WO 2014/001191 Al. Suitable biodegradable polymers are polylactic acid (PLA), poly-L-lactide (PLLA), and poly-D-lactide (PDLA), etc.

Particularly, according to a further embodiment of the medical implant, the biodegradable material comprises a degradation time in the range from 3 months to 12 months, preferably 3 months to 8 months, more preferably 3 months to 6 months.

According to yet another embodiment, the locking member is configured to undergo biodegradation after being subjected to an external stimulus. Such an external stimulus could be subjecting the at least one locking member to heat, cold, electromagnetic radiation such as HF, etc. Particularly, the at least one locking member can be formed as disclosed e.g. in US20110276124A1. According thereto, the at least one locking member can comprise abase body which is completely or partially composed of a biocorrodable metallic material, a coating that coats the base body, the coating comprising a protective layer which is not biocorrodable; and control elements configured such that the protective layer, optionally in combination with the control elements, completely or partially encloses the base body so as to be impermeable to bodily medium, and the protective layer being convertible to a form which is permeable to bodily medium as the result of a change in shape of the control elements which may be regulated and/or controlled by the external stimulus.

Furthermore, according to a preferred embodiment, the housing is configured to be fully implanted into a chamber of a heart of a patient, i.e. forms an intracardiac medical implant. Particularly, according to an embodiment, the medical implant is an active medical implant for delivering electrical therapy to, and/or sensing physiological signal from bodily tissue, particularly an intracardiac pacemaker, an implantable sensor, etc.

Particularly, in an embodiment, the medical implant comprises an energy storage and an electronic circuit configured to generate electrical stimulation pulses, particularly pacing pulses for therapy of the heart of a patient.

Furthermore, according to an embodiment of the medical implant, the housing comprises at least one electrode arranged on the face side of said end portion of the housing for applying said electrical stimulation pulses to the bodily tissue, the at least one electrode contacting the bodily tissue when the medical implant is anchored to the bodily tissue by means of the anchoring device.

Furthermore, according to a preferred embodiment, the at least one anchoring member is a tine configured to assume a bent shape for anchoring the tine to the bodily tissue when the tine is embedded in the bodily tissue. Particularly the bent shape consists of a portion of the tine protruding from the end portion of the housing and a second portion being bent outwards and then back towards the end portion of the housing. Particularly, the at least one anchoring member is made of a super-elastic and/or shape-memory, e.g. nitinol.

Preferably, the anchoring device comprises a plurality of anchoring members, particularly tines, of the afore-mentioned kind, each anchoring member being connected to the supporting member and protruding out of the groove and from the housing. Preferably, the anchoring members are equidistantly spaced on the supporting member in the circumferential direction of the annular supporting member.

Apart from said bent shape, the anchoring element / tine may also comprise other shapes. Particularly the anchoring element/tine may comprise a shape or a portion which may not be actively pulled out of the bodily tissue again but may be biodegradable (e.g. may comprise or may be formed out of one of the materials stated above). According to yet another aspect of the present invention, a method for explanting a medical implant according to the present invention is disclosed, wherein the housing of the implanted medical implant is rotated with respect to the anchoring device (particularly back and forth about a rotation axis coinciding with a longitudinal axis of the housing) in order to break an attachment of the housing to bodily tissue encapsulating the housing or a portion thereof, and wherein a pulling force is applied to the housing of the medical implant in order to disengage the at least one anchoring member from the bodily tissue.

In the following embodiments as well as further features and advantages of the present invention shall be described with reference to the Figures, wherein

Fig. 1A shows an embodiment of a medical implant according to the present invention comprising an anchoring device being rotatably supported on the housing,

Fig. 2A shows the anchoring device of the medical implant shown in Fig. 1 A,

Fig. 3A shows a schematic cross-sectional view of an embodiment of a medical implant according to the present invention, wherein a supporting member of the anchoring device is slidably arranged in a circumferential groove of the housing,

Figs. 3B - 3C show a further embodiment of a medical implant according to the present invention, wherein the supporting element is fixed with respect to the housing by at least one locking element to temporarily prevent a rotation of the housing with respect to the anchoring device,

Fig. 3D illustrates a variant of the locking member(s) of Figs. 3B to 3C,

Fig. 4A shows schematic cross-sectional views of an embodiment of a medical implant according to the present invention, wherein the groove for accommodating the supporting member of the anchoring device comprises an undercut for securing the supporting member to the housing, and

Fig. 4B shows a variant of the anchoring device comprising an annular supporting member comprising protruding portions for engaging behind the undercut of the groove shown in Fig. 4A.

Intracardiac medical implant implantation is often characterized by a small implant approximately lee in volume that is fixed to the heart wall where it eventually is encapsulated and paces for a period of 5-10 years or more. During implantation, it is advantageous to have a stable fixation technique that prevents dislodgement and embolization. After implantation, in some cases it is necessary to remove the medical implant. Once encapsulated, removal is easier when the medical implant can be rotated to break the attachments to tissue and then retracted with longitudinal force. Helix fixation methods do not adequately meet the implant needs, while tine fixation does not adequately meet the needs for extraction.

As indicated in Figs. 1A and 2A, the present invention therefore proposes an anchoring device 1 that particularly allows longitudinal insertion of the medical implant 5 for secure implantation and placement. Particularly, the anchoring device 1 is able to rotate freely (or can be brought into such a state) within an end portion 4a of a housing 4 rather than being in a permanent fixed rotational position with respect to the housing 4. When explantation is needed, the housing 4 of the medical implant 5 can be captured, twisted (e.g. rotated back and forth about the longitudinal axis z of the housing 4) to break an attachment to fibrous encapsulation without damaging the heart (utilizing the rotational freedom of the anchoring device 1 with respect to the housing 4), and then extracted with longitudinal force, like a helix-based device. This confers the advantages of an anchoring device 1 having anchoring members 20 in form of tines during implantation and the advantages of helix-based fixation for extraction.

As shown in Figs. 1 A and 2A, in an embodiment the anchoring device 1 comprises at least one anchoring member 20, here four such anchoring members 20 in the form of tines, that are configured to anchor the housing 4 of the medical implant 5 e.g. to bodily tissue of the heart of a patient. The anchoring members 20 are preferably integrally connected to an annular (particularly circular) supporting member 3 of the anchoring device 1 by means of which the anchoring members 20 are mounted an end portion 4a of the housing 4 of the medical implant 5. Furthermore, each tine 20 can be brought into an essentially straight configuration allowing to pierce bodily tissue and embedding the respective tine 20 into the bodily tissue, and is further configured to assume a bent shape when embedded in the bodily tissue for anchoring the respective tine to the bodily tissue. Particularly the bent shape consists of a portion of the tine protruding from the end portion along the longitudinal axis z of the housing 4 and a further portion being bent outwards and then back towards the end portion of the housing so that the respective tine 20 forms a hook. Other shapes are also conceivable.

Preferably, the housing 4 is hermetically sealed and particularly encloses an electronic circuit forming a pulse generator for generating stimulation pulses that are to be applied to the patient’s heart via at least one tip or pacing electrode 8 that is preferably arranged on a face side 4b of the distal end portion 4a of the housing 4. Furthermore, the medical implant 5 preferably comprises a sensing circuit for sensing physiological signals from the body of the patient, and an energy storage (e.g. battery) for supplying energy to the pulse generator.

Furthermore, the anchoring device 1 is preferably mounted on the distal end portion 4a of the housing 4 of the medical implant 5 such that the anchoring members 20 protrude from the housing 4 for anchoring the medical implant 5 to bodily tissue of a bodily cavity, particularly a heart chamber. According to a preferred embodiment, the medical implant 5 is an implantable intracardiac pacemaker (also denoted as leadless pacemaker) that is configured to be implanted into a ventricle and/or an atrium of the patient’s heart, particularly into the right or left ventricle or right or left atrium, particularly via a catheter. Alternatively, such a medical implant may be fixated to the epicardial surface of the heart.

Preferably, for allowing the anchoring device 1 to rotate with respect to the housing 4 (or vice versa) the supporting member 3 can reside in a groove 6 where it is secured to the housing 4, but can assume a state in which it can rotate within the groove 6 to allow free rotation of the implant’s housing 4 once the anchoring members (e.g. tines) 20 that protrude out of the groove 6 are embedded in the bodily tissue.

As shown in Fig. 3 A, the groove 6 can be formed in a face side 4b of the distal end portion 4a of the housing 4. Additionally, the anchoring device 1 can be configured to be locked in place for the implantation procedure, but over time a dissolvable (resorbable) locking member 7 frees the anchoring device 1 (to realize said rotatable state of the supporting member). In such an embodiment, the anchoring device 1 is free to rotate after a period of time in the body of the patient that is shorter than the full encapsulation time, so that the housing 4 can be rotated to free it from attached bodily tissue upon explantation. A particular embodiment allowing implementation of the resorbable locking feature is shown in Figure 3B to 3D.

Particularly, one means by which the anchoring device 1 can be temporarily locked is the inclusion of locking members 7 on one side of the anchoring members (here in the form of tines) 20 as shown in Fig. 3B. In this figure, the full body of the tines 20 is truncated for illustration purposes. These locking members 7 may be arranged on one side of the respective tine 20, or on each side of one or more of the tines 20 in order to prevent the rotation of the anchoring device (also denoted as tine array) 1. Once these locking members 7 are in contact with bodily tissue, they are configured to dissolve or degrade and leave the anchoring device 1 free to rotate within the groove 6 about the rotation axis z which preferably also forms the longitudinal axis z of the housing 4 of the medical implant 5. Another view of this is shown in the groove cross section (Fig. 3C), where the locking member 7 is seen spanning the groove 6 and blocking the rotation of the anchoring device 1 due to the tine (dotted line) 20 mechanically interfering with the locking member 7.

Another embodiment is shown in Fig 3D, where a locking member 7 in form of a conformal or viscous resorbable polymer is applied while still being deformable (i.e. before it eventually cures/cross links). In this case, the material/locking member 7 is added nearby one or both sides of the tine 20 (or multiple tines), in order to again create a mechanical interference and prevent rotation of the anchoring device 1. Once this material/locking member 7 dissolves in the body of the patient, the housing 4 can rotate about the rotation/longitudinal axis z while the tines 20 remain in place.

Fig. 3B to 3D demonstrates the principle of the locking members 7 but does not adequately illustrate the groove 6 that allows the anchoring device 1 to rotate freely without coming off the housing 4 of the medical implant 5. Figs 4A and 4B show an embodiment for achieving securing of the supporting member 3 to the end portion 4a of the housing 4. In Fig 4A, on the left, the supporting member 3 comprises a bottom having an L-shape. A locking ring 60 is inserted into the groove 6 on top of said protruding portion 30 of the supporting member 3 during assembly that locks the annular supporting member 3 in place in the groove 6 via this L shaped feature (right hand side of Fig. 4). Thus, there is a larger rectangular groove 6 in which the supporting member 3 of the anchoring device 1 is placed, and then a locking ring 60 is added which forms an undercut behind which the supporting member 3 engages with said protruding portion 30.

Fig 4B shows a particular embodiment of the anchoring device 1. Here, the supporting member 3 comprises several protruding portions 30 in the form of fingers that each form an L-shaped feature (in cross section) for engaging behind the undercut 6a of the groove 6 that can e.g. be formed by said locking ring 60 as described above. Particularly, the fingers 30 are cut segments from the same material as the tines 20 and supporting member 3, which segments 30 are bent outwards to form said multiple radially protruding fingers 30. These fingers 30 engage behind the undercut 6a / locking ring 60. Advantageously, this allows the anchoring device 1 to be cut from a single tube, and then shaped into fingers 30 on the bottom and tines 20 on the top. The lower part of Fig. 4B shows a single cross section of a tine 20 where it is coincident with a finger 30.

As an alternative to the fingers 30, the supporting element 3 may also be thicker at the bottom or generally thicker as the bases of the tines 20, wherein the locking ring 60 then secures this thicker portion or even the entire supporting member 3 while allowing rotation of the supporting member 3 in the groove 6 and tines 20 outside the groove 6 with respect to the housing 4. The advantage of the invention at hand is that it allows the safety of the tines implant approach and the explantability of the helix approach. Helices are known to be sensitive to heart wall contact forces, number of turns during deployment, and the nature of the tissue in contact with the helix. Excessive turning can lead to damage of the tissue. Anchoring elements / tines 20 protruding from an annular supporting member 3 do not have this problem. However, tines 20 are difficult to remove once the medical implant is encapsulated. These forces can be overcome with lower risk by twisting the housing 4 of the medical implant 5 about e.g. its longitudinal axis z. Thus, the medical implant 5 according to the present invention can avoid helix-related problems during implantation and avoid tine- related problems during explantation, since the tines 20 do not obstruct rotation according to the present invention.

Claims

1. A medical implant (5) comprising: a housing (4), and an anchoring device (1) mounted to the housing (4), wherein the anchoring device (1) comprises at least one anchoring member (20) protruding from the housing (4) and being configured to pierce bodily tissue to anchor the medical implant (5) to said bodily tissue, and a supporting member (3) connected to the at least one anchoring member (20), wherein the anchoring device (1) is mounted to the housing (4) via the supporting member (3), wherein for explanting the medical implant (5), the housing (4) is configured to be rotated about a rotation axis (z) with respect to the anchoring device (1) when the at least one anchoring member (20) is embedded in said bodily tissue.

2. The medical implant according to claim 1, wherein the supporting member (3) is an annular supporting member.

3. The medical implant according to claim 1 or 2, wherein for allowing rotation of the housing (4) about the rotation axis (z), the supporting member (3) is arranged in a circumferential groove (6) formed in the housing (4).

4. The medical implant according to claim 3, wherein said at least one anchoring member (20) protrudes out of said groove (6).

5. The medical implant according to claim 3 or 4, wherein the groove (6) is formed in a face side (4b) of an end portion (4a) of the housing (4).

6. The medical implant according to one of claims 3 to 5, wherein said groove (6) comprises a circumferential undercut (6a), wherein the supporting member (3) comprises at least one protruding portion (30), preferably a plurality of protruding portions (30), engaging behind said undercut (6a) so that the anchoring device (1) is secured to the housing (4). The medical implant according to one of the claims 3 to 6, wherein the undercut (6a) is formed by a locking ring (60) inserted into the groove (6). The medical implant according to one of the preceding claims, wherein the medical implant (5) comprises at least one releasable locking member (7) being arranged with respect to the at least one anchoring member (20) so as to temporarily prevent a rotation of the housing (4) with respect to the anchoring device (1). The medical implant according to claim 8, wherein the locking member (7) is formed out of or comprises a biodegradable material, wherein the biodegradable material is preferably one of: a biodegradable metal alloy, an Mg based biodegradable alloy, and Fe based biodegradable alloy, a Zn based biodegradable alloy. The medical implant according to claim 8 or 9, wherein the biodegradable material comprises a degradation time in the range from 3 months to 12 months, preferably 3 months to 8 months, more preferably 3 months to 6 months. The medical implant according to one of the preceding claims, wherein the housing (4) is configured to be fully implanted into a chamber of a heart of a patient. The medical implant according to one of the preceding claims, wherein the medical implant (5) comprises an energy storage and an electronic circuit enclosed by the housing (4) and configured to generate electrical stimulation pulses. The medical implant according to claims 5 and 12, wherein housing (4) comprises at least one electrode (8) arranged on the face side (4b) of said end portion (4a) of the housing (4) for applying said electrical stimulation pulses to the bodily tissue. The medical implant according to one of the preceding claims, wherein the at least one anchoring element (20) is a tine configured to assume a bent shape for anchoring the tine to the bodily tissue when the tine is embedded in the bodily tissue. - 14 - A method for explanting a medical implant (5) according to one of the preceding claims, wherein the housing (4) is rotated with respect to the anchoring device (1) in order to break an attachment of the housing (4) to bodily tissue, and wherein a pulling force is applied to the housing (4) of the medical implant (5) in order to disengage the at least one anchoring member (20) from the bodily tissue.