WO2022122201A1

WO2022122201A1 - Implantable cardiac monitor

Info

Publication number: WO2022122201A1
Application number: PCT/EP2021/074779
Authority: WO
Inventors: Joachim Elsner; Alan Fryer; Sophie NEEF; Armin FARIBORZ; Carsten SEEHAFER
Original assignee: Biotronik Se & Co. Kg
Priority date: 2020-12-08
Filing date: 2021-09-09
Publication date: 2022-06-16
Also published as: DE202020107059U1

Abstract

The present disclosure provides an implantable cardiac monitor (1), comprising: a housing (2) for enclosing an electronic circuit configured to record an electrocardiogram of a patient, a first electrode (3) and a second electrode (4) configured to derive the electrocardiogram, wherein the first electrode (3) is arranged at a free end (5a) of an elongated and flexible member (5) extending from a first end (21) of the housing (2), and wherein the second electrode (4) is arranged at a second end (22) of the housing (2) opposite to the first end (21).

Description

Implantable cardiac monitor

Embodiments of the present disclosure relate to an implantable cardiac monitor. Embodiments of the present disclosure relate more particularly to the use of an electrically conductive filament to reduce the volume of an implantable cardiac monitor. Such devices are sometimes also called loop recorder.

Prior art implantable cardiac monitors (ICMs), such as those shown in FIG. 1, include a longitudinal extension 100 of the housing 200 such that an extended SECG vector is created between the non-insulated tip (first ECG pole 300) and the opposite end 301 of the housing 200 (second ECG pole 301). Furthermore, the longitudinal extension 100, together with the housing 200, also serves as a dipole antenna for far-field RF telemetry, e.g. in the 402 - 405 MHz MICS band, for communication with another medical device used, for example, to analyze and/or relay data recorded by the cardiac monitor (e.g., SECG of the person wearing the ICM).

FIG. 3 shows a prior art implantation tool 400, in particular for use with the implantable cardiac monitor shown in FIG. 1, which uses a spout-like part 500 to implant the implantable cardiac monitor of the prior art.

Smaller integrated circuits combined with smaller battery technology have allowed the volume of such ICMs to be significantly reduced over the past decade.

However, the continuation of this development will lead to ICMs with an ever shorter ECG vector. The quality of a subcutaneous ECG (SECG for subcutaneous electrocardiogram) recorded by an ICM depends on the length of the ECG vector (the amplitude of the SECG signal is linearly proportional to the distance between the ECG poles), so that said progressive miniaturization of ICMs in the classical form will lead to SECGs with a correspondingly poorer signal-to-noise ratio. Moreover, if the housing of the cardiac monitor is very small, the device will more easily tend to move away from its original implantation site.

In light of the above, an implantable cardiac monitor that overcomes at least some of the problems in the art is beneficial.

It is an object of the present disclosure to provide an implantable cardiac monitor which is improved with respect to the aforementioned problem of shortening of the ECG vector, while further preventing movement of the implantable cardiac monitor away from the implantation site.

The objects are solved by the features of the independent claims. Preferred embodiments are defined in the dependent claims.

According to an independent aspect of the present disclosure, an implantable cardiac monitor (ICM) is provided. The implantable cardiac monitor includes a housing for enclosing an electronic circuit configured to record an electrocardiogram of a patient; and a first electrode and a second electrode configured to derive the electrocardiogram. The first electrode is arranged at a free end of an elongated and flexible member extending from a first end of the housing. The second electrode is arranged at a second end of the housing opposite to the first end.

Implantable cardiac monitors (also referred to as ICM) are small electrophysiology (EP) devices that can be used for long-term monitoring of a patient’s heart electrical activity. ICMs can eliminate the need for wire leads attached to the patient. ICMs can be inserted under the patient’s skin and can record cardiac data of the patient continuously for up to approximately five years. ICMs are sometimes also referred to as loop recorders.

Preferably, the implantable cardiac monitor is configured to record a surface electrocardiogram (SECG). Preferably, the first electrode is referred to as first ECG electrode. Likewise, the second electrode can be referred to as second ECG electrode.

Preferably, the housing is an electrically conductive housing.

Preferably, the case is made of ceramic. In this case, no insulation of the housing would be necessary. However, the second electrode would then also have to be led out of the housing with a feedthrough.

Preferably, the housing includes, or is made of, metal. For example, the metal can be titanium or a titanium alloy.

Preferably, the implantable cardiac monitor includes a first electrical insulation surrounding the housing.

Preferably, the first electrical insulation is a silicone coating.

Preferably, the first electrical insulation is configured to leave the second end of the housing exposed. Thereby, the second end can contact surrounding tissue and accordingly act as a second electrode. In other words, the second end can be the second electrode.

Preferably, the housing has a cylindrical shape. The term “cylinder” can be understood as commonly accepted as having a circular bottom shape and a circular upper shape and a curved surface area or shell connecting the upper circle and the little lower circle.

Preferably, the elongated and flexible member has a greater extension in a direction of its longitudinal extension than perpendicular to this direction. The direction perpendicular to the longitudinal extension direction can be, or correspond to, an outer diameter of the elongated and flexible member. Preferably, the elongated and flexible member has an outer diameter that is many times (e.g. at least 100 times or at least 1000 times) smaller than a corresponding outer diameter of the housing in the same direction. Preferably, the outer diameter of the elongated and flexible member is in a size range from pm to mm.

Preferably, the direction of the longitudinal extension of the elongated and flexible member coincides with a longitudinal axis of the housing, such as a cylinder axis of the housing.

The elongated and flexible member is configured to be flexible. The term “flexible” is understood to distinguish over “inflexible” or “rigid”. In particular, the elongated and flexible member can be bent to a certain extent without being damaged.

Preferably, the elongated and flexible member is a thread.

Preferably, the elongated and flexible member includes, or consists of, individual filaments or fibers.

Preferably, the implantable cardiac monitor includes a second electrical insulation surrounding at least a part of the elongated and flexible member.

Preferably, the second electrical insulation is a silicone coating.

Preferably, the elongated and flexible member is surrounded by the second electrical insulation except for an end section, the end section (at the free end of the elongated and flexible member) forming the first electrode.

Preferably, the end section of the elongated and flexible member includes an element having a diameter greater than a diameter of the elongated and flexible member. The element may be a little object of body (e.g. a sphere having a diameter of about 1 mm) made of biocompatible material which is attached to the distal end of the elongated and flexible member. This element is useful for holding (“picking-up“) the elongated and flexible member during insertion and also serves as an extension of the SECG electrode surface, in particular if the element has a fractal surface. Instead of a sphere another shape suited for easy explantation (e.g. an ellipsoid) could also be used.

Preferably, the implantable cardiac monitor includes an RF (radio frequency) dipole antenna formed by the elongated and flexible member and/or the housing.

Advantageously, the relatively thin, longitudinally elongated and flexible member or thread can grow into the surrounding tissue after implantation and thus stabilizes the position of the implantable cardiac monitor at the implantation site. During explantation, the elongated and flexible member can be pulled out of the tissue like a typical “suture thread” due to its small outer diameter.

The present invention thus compensates for the adverse effects of miniaturization by using a conductive filament or a conductive, elongated and flexible member that serves as an ECG lead and RF antenna and further prevents the implantable cardiac monitor (ICM) from detaching from its implantation site. Compared to the prior art, the volume of the extension of the housing is thus reduced, while the length of the ECG vector can be maintained and further resulting in a shape of the implantable cardiac monitor that helps to better hold the implantable cardiac monitor at its implantation site.

According to another independent aspect of the present disclosure, an implantation tool for implanting an implantable cardiac monitor is provided. The implantation tool can be configured for implanting the implantable cardiac monitor of the embodiment described in this document.

The implantation tool includes a distal first cutting tool for inserting an elongated and flexible member of the implantable cardiac monitor and a proximal second cutting tool for inserting a housing of the implantable cardiac monitor.

Preferably, the first cutting tool has an outer diameter perpendicular to an insertion direction (or longitudinal extension direction of the first cutting tool) that is smaller than an outer diameter of the second cutting tool. Preferably, the first cutting tool is shaped to insert the elongated and flexible member having the first electrode. The first cutting tool can, for example, be configured as a needle that holds the elongated and flexible member. If a spherical body is attached to the distal end of the elongated and flexible member, this first cutting tool can be forked to hold the body (“sphere cutter”).

Preferably, the second cutting tool is shaped to insert the housing of the ICM (“body cutting tool”).

So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

FIG. 1 shows prior art ICMs that have an extension of the housing to capture a correspondingly long ECG vector. It also serves as an RF antenna in the MICS band;

FIG. 2 shows an implantable cardiac monitor according to embodiments of the present disclosure;

FIG. 3 shows a prior art implantation tool, in particular for use with the ICM shown in FIG. 1;

FIG. 4 shows an implantation tool for an implantable cardiac monitor according to embodiments of the present disclosure (e.g., according to FIG. 2); and

FIG. 5 shows a retraction of the implantation tool of FIG. 4.

Reference will now be made in detail to the various embodiments of the disclosure, one or more examples of which are illustrated in the figures. Within the following description of the drawings, the same reference numbers refer to same components. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the disclosure and is not meant as a limitation of the disclosure. Further, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the description includes such modifications and variations.

FIG. 2 shows an implantable cardiac monitor 1 according to embodiments of the present disclosure.

The implantable cardiac monitor 1 includes a housing 2 for enclosing an electronic circuit configured to record an electrocardiogram of a patient; and a first electrode 3 and a second electrode 4 configured to derive the electrocardiogram. The first electrode 3 is arranged at a free end 5a of an elongated and flexible member 5 extending from a first end 21 of the housing 2. The second electrode 4 is arranged at a second end 22 of the housing 2 opposite to the first end 21.

The implantable cardiac monitor 1 may include a first electrical insulation surrounding the housing 2. Preferably, the first electrical insulation is configured to leave the second end 22 of the housing 2 exposed. Thereby, the second end 22 can contact surrounding tissue and accordingly act as the second electrode 4. In other words, the second end 22 can be the second electrode 4.

Also an arrangement with several electrodes realized as flexible members is possible. As an example let us consider two electrodes realized as flexible members. In this case the housing could sit between (e.g. in the middle of) the two electrodes which are both realized as flexible members. The housing forms a third electrode. The three electrodes could be implanted to form an equilateral triangle.

In this way one would obtain three SECG vectors (electrode 1 - electrode 2, electrode 1 - electrode 3 and electrode 2 - electrode 3) which could be recorded independently. Alternatively, the vector with the best signal could be chosen. For an arrangement with several electrodes realized as flexible members a suitable implantation procedure would need to be defined and a tool corresponding to this procedure would need to be designed.

Example for an implantation procedure:

1) Insert the first electrode (realized as a flexible member) by using e.g. a needle which is subsequently removed.

2) Insert the second electrode (realized as a flexible member) at an angle -60° to the first electrode by using e.g. a needle which is subsequently removed.

3) Insert the housing by using a cutter.

The elongated and flexible member 5 may be in the form of a thread and may serve as the first electrode 3, and in particular as part of an antenna.

The elongated and flexible member 5 may be surrounded by a second electrical insulation 6 outside the housing 2 of the implantable cardiac monitor 1 except for the free end 5a, which forms the first electrode 3, and can be guided into the housing 2 of the implantable cardiac monitor 1 via an electrical feedthrough 7. The feedthrough 7 can optionally be arranged in a header 8 (e.g., made of an insulating material such as epoxy) of the housing 2 (the feedthrough 7 can also be arranged directly on the housing 2). Via the feedthrough 7, the elongated and flexible member 5 can be connected to the electronic circuit of the implantable cardiac monitor 1, which enables the recording of an ECG (e.g., SECG).

The elongated and flexible member 5 is electrically conductive so that the elongated and flexible member 5 can conduct ECG or SECG signals and form an RF antenna dipole. If desired, the conductive material can be biocompatible (e.g. titanium). Conductive stainless steel filaments are commercially available.

Simulations indicate that any part of the elongated and flexible member 5 that is more than 2 cm from the housing 2 acts as a good RF-antenna (actually the RF-antenna is formed by the flexible member and by the housing); the gain is expected to be approximately -30 dBi at both MICS and Bluetooth frequencies, which is good for an antenna implanted in body tissue.

Preferably, the second electrical insulation 6 (“outer insulating layer”) of the elongated and flexible member 5 is made of silicone.

The second electrical insulation 6 can be removed at the distal (or free) end 5a of the elongated and flexible member 5, e.g., about 1 cm, already during the production process. This end section and/or the free end 5a of the elongated and flexible member 5 serves as the first electrode 3 for detecting the ECG or SECG.

The elongated and flexible member 5 extends from the first end 21 or from the header 8 (if present) of the housing 2. A second end 22 of the housing 2 opposite the first end 21 or the header 8 forms a second electrode 4, which together with the first electrode 3 serves to derive the ECG or SECG.

In some embodiments, an element or small body 9 (e.g. a sphere, in particular with a diameter of about 1 mm) made of biocompatible material can be attached to the distal end of the elongated and flexible member 5. This element or small body 9 serves to hold or grip the elongated and flexible member 5 during implantation (see FIGs. 4 and 5) and also serves as an extension of the surface of the first electrode 3, especially if the element or small body 9 has a fractal surface.

Instead of a sphere, another shape suitable for explantation (e.g., an ellipsoid) may be used.

The header 8 of the implantable cardiac monitor 1 is optional; it serves only as a rounded shape or outer surface to prevent potentially sharp edges of a classic feedthrough from contacting body tissue.

FIG. 4 shows an implantation tool 11 for an implantable cardiac monitor 1 according to embodiments of the present disclosure (e.g., according to FIG. 2). FIG. 5 shows a retraction of the implantation tool 11 of FIG. 4. The implantation tool 11 includes a distal first cutting tool 13 for inserting the elongated and flexible member 5 of the implantable cardiac monitor 1 and a proximal second cutting tool 14 for inserting the housing 2 of the implantable cardiac monitor 1.

In some embodiments, the first cutting tool 13 is configured as a needle or a syringe, but the present disclosure is not limited thereto.

FIG. 4 shows the insertion of the implantable cardiac monitor 1 into the patient’s body. As shown in FIG. 4, the implantation tool 11 distally has a first (thinner) cutting tool 13, which is shaped in such a way that it inserts the elongated and flexible member 5 (together with the first electrical insulation 6, the first electrode 3 and, if applicable, the element or small body 9) into the patient’s tissue. Hereto, the first cutting tool 13 can be configured, for example, as a needle, which holds the elongated and flexible member 5. If, for example, the element or small body 9 (or an alternative body) is attached to the elongated and flexible member 5, the first cutting tool 13 could be forked, for example, to hold the element or small body 9. The first cutting tool 13 can therefore also be referred to as a ball or sphere cutter 13.

The second (larger) proximal cutting tool 14 is shaped to insert the housing 2 of the implantable cardiac monitor 1 into the patient’ s tissue. The second cutting tool 14 is therefore also referred to as body cutter 14.

FIG. 5 shows the process of retracting the implantation tool 11, with the cutting tools 13, 14 moving away from the patient (here exemplarily to the right), with the elongated and flexible member 5 remaining in the implanted position and the second cutting tool 14 opening in such a way that the housing 2 remains in its implanted position.

The purpose of the implantation tool 11 is to cut (injure) as little body tissue as possible during insertion. According to FIG. 4, therefore, the first cutting tool 13 on the left side of FIG. 4 has exactly the size to provide the path for the elongated and flexible member 5. This first cutting tool 13 can thereby be configured as a needle, as already explained above, wherein the elongated and flexible member 5 can be threaded onto the needle, for example in an eye, wherein in particular the eye is arranged at the tip of the first cutting tool 13, and the non-fixed part of the elongated and flexible member 5 projects into the interior of the first cutting tool 13, preferably over a length of about 1 cm.

When the end of the elongated and flexible member 5 has the element or small body 9, preferably having a shape suitable for explantation, such as a sphere or an ellipsoid, the first cutting tool 13 is configured to receive or hold the element or small body 9. For example, the tip of the first cutting tool 13 may be bifurcated or split to receive or hold the element or small body 9.

The second cutting tool 14, in order to protect the patient’s tissue, also only has a size such that a corresponding path can just be created for inserting the housing 2 of the implantable cardiac monitor 1.

When the housing 2 of the implantable cardiac monitor 1 is fully inserted or implanted, the implantation tool 11 is retracted, e.g. in analogy to the handling of current ICM implantation procedures. When removing the implantation tool 11 (see FIG. 5), the needle or the first cutting tool 13 is retracted in such a way that the element or small body 9 and the elongated and flexible member 5 remain in their respective positions. Furthermore, the second cutting tool 14 opens an exit opening for the housing 2, which can thereby be supported e.g. on an abutment 15 of the implantation tool 11 and remains in its implanted position.

According to the embodiments of the present disclosure, a volume of the implantable cardiac monitor is reduced while maintaining its long ECG vector and antenna characteristics. Implantation along the length of the elongated and flexible member is done with a needle and is therefore easier and associated to less tissue injury. In-growth of the elongated and flexible member prevents the implantable cardiac monitor from leaving the implantation site. In this way future implantable cardiac monitors can fully take advantage of smaller batteries and electronics. While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

1. An implantable cardiac monitor (1), comprising: a housing (2) for enclosing an electronic circuit configured to record an electrocardiogram of a patient; and a first electrode (3) and a second electrode (4) configured to derive the el ectrocardi ogram, wherein the first electrode (3) is arranged at a free end (5a) of an elongated and flexible member (5) extending from a first end (21) of the housing (2), and wherein the second electrode (4) is arranged at a second end (22) of the housing (2) opposite to the first end (21).

2. The implantable cardiac monitor (1) of claim 1, wherein the housing (2) is an electrically conductive housing and/or wherein the housing (2) includes, or is made of, metal.

3. The implantable cardiac monitor (1) of claim 1 or 2, further including a first electrical insulation surrounding the housing (2), wherein the first electrical insulation is configured to leave the second end (22) of the housing (2) exposed, in particular wherein the second end (22) is the second electrode (4).

4. The implantable cardiac monitor (1) of any one of claims 1 to 3, wherein the elongated and flexible member (5) has a greater extension in a direction of its longitudinal extension than perpendicular to this direction.

5. The implantable cardiac monitor (1) of claim 4, wherein the direction of the longitudinal extension of the elongated and flexible member (5) coincides with a longitudinal axis of the housing (2).

6. The implantable cardiac monitor (1) of any one of claims 1 to 5, wherein the elongated and flexible member (5) is a thread. The implantable cardiac monitor (1) of any one of claims 1 to 6, wherein the elongated and flexible member (5) includes, or consists of, individual filaments or fibers. The implantable cardiac monitor (1) of any one of claims 1 to 7, further including a second electrical insulation (6) surrounding at least a part of the elongated and flexible member (5). The implantable cardiac monitor (1) of claim 8, wherein the elongated and flexible member (5) is surrounded by the second electrical insulation (60) except for an end section, the end section forming the first electrode (3). The implantable cardiac monitor (1) of claim 9, wherein the end section of the elongated and flexible member (5) includes an element (9) having a diameter greater than a diameter of the elongated and flexible member (5). The implantable cardiac monitor (1) of claim 10, wherein the element (9) is a sphere or an ellipsoid and/or is made of a biocompatible material. The implantable cardiac monitor (1) of any one of claims 1 to 11, further including an RF dipole antenna formed by the elongated and flexible member (5) and/or the housing (2). An implantation tool (11) for implanting an implantable cardiac monitor (1) according to one of the proceedings claims, comprising: a distal first cutting tool (13) for inserting the elongated and flexible member (5) of the implantable cardiac monitor (1); and a proximal second cutting tool (14) for inserting the housing (2) of the implantable cardiac monitor (1). The implantation tool (11) of claim 13, wherein the first cutting tool (13) has an outer diameter perpendicular to an insertion direction that is smaller than an outer diameter of the second cutting tool (14). - 15 - The implantation tool (11) of claim 13 or 14, wherein: the first cutting tool (13) is shaped to insert the elongated and flexible member (5) having the first electrode (3); and/or the first cutting tool (13) is configured as a needle; and/or the first cutting tool (13) is forked.