Fixation device for securing an implantable medical device in a patient's tissue - Patent Application 20070122997

Abstract

A fixation device (1) for securing an implantable medical device (3) to a patient's tissue (33) is described. The fixation device includes an anchoring member (5) for anchoring the fixation device to the implantable medical device and at least two tines (7; 37, 39) extending from the anchoring member on opposite sides of a central axis (11) of the fixation device. The tines have a curved geometry and are elastically deformable such that they are reversibly deformable between a relaxed configuration and a pre-deployed configuration. In the relaxed configuration, the tines are free of any inherent mechanical prestress, their intermediate portions (12) are positioned distally relative to the anchoring member, and their cantilevered ends (21) are at least one of oriented proximally and / or proximally relative to the anchoring member. In the pre-deployed configuration, the tines are mechanically deformed and under inherent prestress to assume a geometry that allows the fixation device to be placed in a tubular protector sheath (31), with the intermediate portions and cantilevered ends of the tines being positioned distally relative to the anchoring member. The curved geometry and deformation characteristics of the tines are configured such that during the initial stage of the deformation procedure, during which the tines deform from their pre-deployed configuration to their relaxed configuration due to their inherent prestress, the cantilevered ends of the tines are displaced to follow a deployment trajectory extending at an acute angle of attack (α) of 40° to 90° relative to the central axis of the fixation device, thereby limiting the maximum penetration depth to such an extent that the fixation device can be secured even in very thin-walled cardiac tissue, such as the atrial wall.

Description

[Technical Field]

[0001] The present invention relates to a fixation device for fixing an implantable medical device to the tissue of a patient, and further to an implantable medical device comprising such a fixation device.

[0002] There are various medical devices (also called implantable medical devices - IMDs) that must be implanted in a patient at a location inside the patient's body. Specifically, some medical devices may be active, i.e., capable of generating electrical signals and transmitting such signals to tissues inside the patient's body, and are therefore called active IMDs (AIMDs). For example, a pacemaker may be implanted in a patient to generate electrical signals to stimulate the patient's heart.

[0003] Traditionally, pacemakers have included a housing and elongated leads extending from the housing, with the ends of the leads functioning as electrodes. The housing has been implanted subcutaneously. Electrodes are then implanted, making direct electrical contact with cardiac tissue. However, AIMD leads have been found to be a potential source of clinical complications.

[0004] To avoid such clinical complications, implantable leadless pacemakers (ILPs, sometimes referred to as intracardiac pacemakers) have been developed. Leadless pacemakers are small devices configured to be implanted directly into a patient's heart and therefore do not require external leads. Typically, ILPs are implanted directly into a heart chamber, such as one of the ventricles. The ILP includes a housing that houses electronics, such as a controller, and further houses an energy source, such as a battery. Additionally, the ILP includes electrodes exposed on the exterior of the housing. Finally, the ILP includes a fixation device configured to anchor the housing to, for example, cardiac tissue surrounding a ventricle, so as to securely fix the ILP inside the heart chamber with the electrodes of the ILP in electrical contact with the cardiac tissue.

[0005] Generally, during an implantation procedure, an ILP is introduced into a patient's body, advanced to an intended implantation location in the patient's heart, and anchored at such intended location using a specific fixation device. To deliver the ILP to the intended location in the heart, the ILP may be attached to or contained within the distal end of a specific delivery system. For example, during the delivery procedure, the ILP may be housed within a protector sheath (sometimes called a protector cup). The delivery system typically includes an elongated catheter. In this regard, the catheter may be steerable and / or navigable so that the distal end of the catheter can be displaced throughout the patient's body, i.e., along the patient's blood vessels, until it reaches the intended implantation location. Once the implantation location is reached, the ILP can be deployed, i.e., expelled from the protector sheath. During the deployment procedure, the fixation device can be activated to, for example, anchor the ILP in the tissue at the implantation location.

[0006] For example, the fixation device can include a plurality of elastically flexible tines. Once positioned in the protector sheath, these tines can be deformed in a pre-deployment configuration, where they are mechanically deformed to assume a geometry that allows them to be contained within the typically tubular protector sheath under inherent prestress. During the deployment procedure, the ILP, along with its fixation device, can be continuously ejected from the protector sheath, resulting in the tines exiting the protective sheath at their distal ends. When the protector sheath is held against cardiac tissue at the implantation site, the tines can penetrate and engage the cardiac tissue. Upon resuming the stress-free, relaxed configuration, the tines can securely fix the ILP to the cardiac tissue.

[0007] There may be a need for improved fixation devices for securing implantable medical devices to a patient's tissue. In particular, there may be a need for fixation devices that allow for fixation of IMDs to various types of cardiac tissue, including cardiac tissue that is different from cardiac tissue surrounding the ventricles of the heart, and that has different properties compared to such ventricular cardiac tissue. Specifically, there may be a need for fixation devices that allow for fixation of IMDs, particularly ILPs, to cardiac tissue surrounding the atria of the heart. Further, there may be a need for IMDs that include such fixation devices.

[0008] Such a need may be met by the subject matter of the independent claims. Advantageous embodiments are defined in the dependent claims and the corresponding description and drawings.

[0009] According to a first aspect of the present invention, a fixation device configured to fix an implantable medical device, particularly an implantable leadless pacemaker, to a patient's tissue, particularly an atrium of the patient's heart, is described. The fixation device includes an anchoring member for anchoring the fixation device to the implantable medical device and at least two tines extending from the anchoring member on different sides of a central axis of the fixation device. The tines have a curved geometry and are elastically deformable such that they are reversibly deformable between a relaxed configuration and a pre-deployed configuration. In the relaxed configuration, the tines are free of any inherent mechanical prestress, with intermediate portions of the tines positioned distally relative to the anchoring member and cantilevered ends of the tines oriented proximally and / or proximally relative to the anchoring member. In the pre-deployed configuration, the tines are mechanically deformed and under inherent prestress to a geometry that allows the fixation device to be placed in a tubular protector sheath, with the intermediate portions and cantilevered ends of the tines positioned distally relative to the anchoring member. In that regard, the curved geometry and deformation characteristics of the tines are configured such that during the initial stage of the deformation procedure, during which the tines deform from their pre-deployed configuration to their relaxed configuration due to their inherent prestress, the cantilevered ends of the tines are displaced to follow a deployment trajectory extending at an emergency angle of attack of 40° to 90° relative to the central axis of the fixation device.

[0010] The phrase "at least two tines extending from the anchoring member on different sides of the central axis of the fastening device" should be understood within the framework of the present application as tines distributed along the circumference of a circle having its center on the central axis of the fastening device. Two tines are considered to be on different sides of the central axis of the fastening device if the angle between at least two of the tines and the center of the circle is at least 100°, in particular at least 120°, in particular at least 180°.

[0011] According to a second aspect of the present invention, an implantable medical device, particularly an implantable leadless pacemaker, particularly configured for implantation within an atrium of a patient's heart, is described. The IMD comprises a housing, a controller provided in the housing for controlling the functions of the medical device, an energy source provided in the housing for supplying energy to the controller, and a fixation device according to an embodiment of the first aspect of the present invention, the fixation member of which is fixed to the housing.

[0012] The idea of ​​the embodiments underlying the present invention can be construed as being based, inter alia, on the following observations and realizations.

[0013] Briefly summarized in a non-limiting manner, embodiments of the present invention relate to fixation devices that can fix an IMD, such as an ILP, to an implantation location that differs from traditionally used implantation locations, particularly with respect to the characteristics of the tissue to which the IMD is fixed and / or the characteristics of the environment and space in which the IMD is placed.

[0014] In particular, it has been found that in certain medical conditions, it may be beneficial to implant an ILP inside the atrial cavity rather than inside the ventricular cavity. However, the properties of the cardiac tissue surrounding the atrium are significantly different from those of the cardiac tissue surrounding the ventricle, for example, in terms of tissue thickness, tissue surface properties, elastic properties, and tissue geometry. Specifically, the cardiac tissue of the atrium is generally much thinner, softer, and / or more flexible than the cardiac tissue of the ventricle, and furthermore, typically does not include a smooth surface, but includes a pectinate structure at least in some areas.

[0015] Therefore, it was an objective to design, for example, a fixation device that would serve as an anchoring mechanism to secure an IMD, particularly an ILP, inside the atrial cavity of the heart while also achieving reliable contact between the atrial electrode and tissue. The anchoring should not damage the atrium unnecessarily or to the point of clinical dysfunction, nor should it cause unacceptable blood loss.

[0016] It has been found that to achieve such a goal, the tines of the fixation device must be specifically configured. For example, whereas the tines of conventional fixation devices for anchoring an ILP to ventricular tissue are typically configured for relatively deep penetration of the ventricular tissue, the tines of the fixation device proposed herein are specifically configured for only shallow tissue penetration.

[0017] For such purposes, the geometry and elastic deformation characteristics of the tines are specifically adapted so that, when an IMD having its fixation device is deployed from a tubular protector sheath during implantation and deployment procedures, the tines extend at an angle of 40° to 90° relative to the central axis of the fixation device (referred to herein as an acute angle of attack). In other words, because the central axis of the fixation device is substantially perpendicular to the surface of the cardiac tissue to which the fixation device is attached, the tines extend at a shallow angle of less than 50°, preferably less than 40°, 30°, 20°, 10°, or even about 0° (i.e., parallel) relative to the surface of the cardiac tissue, thereby penetrating such cardiac tissue and / or, optionally, the interdigitated structures of such cardiac tissue at a shallow angle. Upon penetrating the cardiac tissue at such a shallow angle, the cantilevered ends of the tines may then be displaced along a shallow deployment trajectory.

[0018] Thus, as a result of the deployment procedure, the tines can extend through cardiac tissue with a small penetration depth, thereby significantly reducing the risk of damaging or perforating the heart wall surrounding, for example, the atrial cavity. Furthermore, the geometry of the tines can be configured to take into account the limited available space, for example, inside the atrial cavity.

[0019] The features of the embodiments of the present invention will be described in more detail below.

[0020] The fixation devices described herein are particularly adapted for anchoring an IMD, particularly an ILP, in patient tissue, particularly cardiac tissue surrounding an atrial cavity of the patient's heart. The fixation devices include an anchoring member that is anchored to the IMD with tissue-penetrating tines to secure the IMD to the cardiac tissue.

[0021] The anchoring member can form a common base or root element from which the tines extend. The anchoring member can consist of a single element. For example, the anchoring member can include a ring, plate, or other structural component and can further include a mounting structure capable of securing the anchoring member to the IMD. The anchoring member can have a symmetrical shape, including, for example, mirror symmetry or rotational symmetry about an axis of symmetry. For example, the anchoring member can be circular in shape.

[0022] The tines extend laterally from the anchoring member. Preferably, the tines extend radially outward from the anchoring member. Thus, the root end of each tine is attached to the anchoring member, while the opposite end is unsupported, hence the term cantilevered end. Preferably, the tines are distributed equidistantly around a circle centered on the central axis of the anchoring device. In this embodiment, the anchoring device includes an even number of tines that are circumferentially equidistant from each other, i.e., two, four, six, eight, or more tines. In this embodiment, the tines are arranged in pairs, with the tines of each pair extending diametrically opposite each other, thereby extending on opposite sides of the central axis of the anchoring device. Alternatively, the anchoring device includes an odd number of tines that are circumferentially equidistant from each other, i.e., three, five, seven, or more tines. In this embodiment, at least two of the tines are arranged on different sides of the central axis of the anchoring device. The tines extend from the anchoring member on both sides of a central axis of the fixation device, which may coincide with the longitudinal medial axis and / or axis of symmetry of the anchoring member and / or IMD. The tines may extend from the anchoring member, for example, in an equidistant and / or symmetrical configuration relative to the central axis. Preferably, but not necessarily, the tines are integral with the anchoring member, i.e., the tines and the anchoring member form a single component with the tines extending integrally from the anchoring member. The tines may be made of a medical-grade material. Furthermore, the tines may be made of a material with a shape memory effect. Preferably, the tines may be made of a superelastic material, particularly a superelastic metal or metal alloy such as a nickel-titanium alloy, also known as Nitinol. For example, the tines may be manufactured by laser cutting from Nitinol tubing and setting to the desired shape, which may include, for example, forming the tines into the intended curved geometry and further including heat treatment to establish the shape memory effect. The tines may have a consistent or uniform thickness and / or width along their entire length. Alternatively, the tines may have a non-uniform thickness and / or width along their entire length. At cantilevered ends, each tine tip may terminate in a radius. All tines of a fastener may have the same length.Alternatively, the fastener may include tines of different lengths, e.g., tines of a first type are longer than tines of a second type. Preferably, there are at least two tines of each type. Additionally, there may be an even number of tines of each type. The tines, or optionally the entire fastener, may be subjected to a finishing process, such as bead blasting, etching, and / or electropolishing, to remove sharp edges and / or reduce corrosion tendencies.

[0023] The tines are fabricated to have a curved geometry when in the relaxed configuration. In that regard, the relaxed configuration corresponds to a configuration in which no substantial external forces are applied to the tines and there is no inherent mechanical prestress in the tines. Thus, the relaxed configuration corresponds to the shape the tines acquire due to superelastic and shape-memory effects, i.e., when the tines are not actively deformed. As described in more detail below, the curved geometry of the tines can be specifically adapted to enable the tines to penetrate tissue in an intended manner, particularly at an intended emergency angle of attack, during a deployment procedure, enabling shallow tissue penetration. In particular, in the relaxed configuration, each tine has a middle portion disposed distally relative to the anchoring member, i.e., the middle portion of the tine is disposed farther from the IMD than the anchoring member. Furthermore, in the relaxed configuration, each tine has a cantilever end disposed proximally, i.e., facing in a proximal direction extending toward the IMD, and / or each tine has a cantilever end disposed proximally relative to the anchoring member.

[0024] Due to their superelasticity, the tines can be temporarily and reversibly deformed to other configurations, such as a pre-deployed configuration. In such a pre-deployed configuration, the fixation device, along with the IMD, can be housed within a tubular protector sheath. Typically, the diameter of such a protector sheath is significantly smaller than the diameter of the fixation device in its relaxed configuration, resulting in the fixation device's tines having to be substantially deformed in the pre-deployed configuration. In particular, in the pre-deployed configuration, not only the cantilevered ends of the tines but also their intermediate portions are positioned and oriented distally relative to the anchoring members. Furthermore, in the pre-deployed configuration, the tines are deflected distally and toward the central axis, and are therefore elastically prestressed, i.e., mechanically biased, resulting in an inherent force pushing the tines radially outward and / or proximally toward the relaxed configuration.

[0025] In this regard, the curved geometry of the tines and their deformation characteristics are specifically adapted so that, as the tines are ejected from the tubular protector sheath, they begin to move and change their configuration to eventually resume their relaxed configuration. During this deformation process, the cantilevered ends of the tines are displaced along the deployment trajectory as the tines deflect from the pre-deployment configuration to the relaxed configuration. Specifically, the curved geometry and deformation characteristics of the tines are adapted so that, during the initial stage of the deformation process, i.e., at the beginning of the deployment trajectory, the cantilevered ends of the tines move at an emergency angle of attack relative to the central axis of the fixation device, the emergency angle of attack being between 40° and 90°. The lower limit of the emergency angle of attack may be greater than 40°, e.g., 45°, 50°, 55°, 60°, 65°, 70°, or more. The upper limit of the emergency angle of attack may be less than 90°, e.g., 89°, 88°, 87°, 85°, 82°, or less. Thus, during deployment of the fixation device, including the tine deformation procedure, the cantilevered ends of the tines impact and penetrate the surface of the adjacent tissue at a shallow penetration angle of 0° to 50°. In this regard, the penetration angle is defined as the complement of the emergency angle of attack, i.e., (penetration angle) = 90° - (emergency angle of attack). Generally, the smaller the penetration angle, the less the tines engage the tissue, i.e., the smaller the maximum penetration depth of the tines, resulting in a lower risk of damaging or even perforating thin-walled layers of tissue with the tines.

[0026] Preferably, according to embodiments, the curved geometry and deformation characteristics of the tines are configured to implement an emergency angle of attack between 75° and 90°. More specifically, the lower emergency angle of attack limit may be greater than 75°, such as 76°, 77°, 78°, 80°, 82°, 84°, or greater.

[0027] According to embodiments, the curved geometry and deformation characteristics of the tines are configured such that the maximum penetration depth of the tines is less than 1 mm, where the maximum penetration depth corresponds to the maximum distance of the deployment trajectory relative to the position of the cantilevered end of the tine when the tine is in the pre-deployment configuration, measured in a direction parallel to the central axis of the fixation device.

[0028] The maximum penetration depth may also be interpreted as the distance the tines are introduced into the tissue parallel to the central axis and distal to the distal-most surface of the IMD. Stated differently, the maximum penetration depth may be interpreted as the thickness of the layer rearwardly engaged by the penetrating tines.

[0029] Preferably, the maximum penetration depth is limited to less than 0.95 mm, less than 0.9 mm, less than 0.85 mm, less than 0.8 mm, less than 0.75 mm, less than 0.7 mm, less than 0.65 mm, less than 0.6 mm, less than 0.55 mm, less than 0.5 mm, less than 0.45 mm, less than 0.4 mm, less than 0.35 mm, less than 0.3 mm, less than 0.25 mm, less than 0.2 mm, less than 0.15 mm, or less than 0.1 mm. The deployment trajectory can even be adapted so that the maximum penetration depth is substantially 0 mm, meaning that the tines are ejected from the protector sheath at a 90° acute angle of attack so that the tines extend substantially parallel to the surface of the tissue with which they are engaged. At such a substantially 0° penetration angle, the tines may not penetrate tissue in depth, but may still penetrate tissue protrusions formed, for example, by pectinate structures, since these are typically present on the surface of cardiac tissue in the atrial wall. Generally, the smaller the maximum penetration depth is set, the lower the risk of damaging or perforating the thin-walled layer of tissue with the tines may be.

[0030] According to embodiments, the curved geometry and deformation characteristics of the tines are configured such that the maximum active diameter of the fixation device is less than 15 mm, where the maximum active diameter corresponds to the maximum width of the deployment track measured perpendicular to the central axis of the fixation device.

[0031] Generally, the active maximum diameter may correspond to, or in most cases may be slightly larger than, the diameter of the fixation device in its relaxed configuration. The active maximum diameter depends on the trajectory that the cantilevered ends of the tines travel during the deployment procedure, with such trajectory potentially extending along a width that is wider than the width of the fixation device in its relaxed configuration at the end of the deployment procedure.

[0032] Preferably, the upper limit of the active maximum diameter is set to less than 14.5 mm, less than 14 mm, less than 13.5 mm, or less than 13 mm. However, the active maximum diameter should generally be substantially larger than the diameter of the IMD, which typically has a diameter of 5 mm to 12 mm, more typically 6 mm to 9 mm. Thus, the lower limit of the active maximum diameter should generally be greater than 8 mm, and in most cases greater than 10 mm, or even greater than 12 mm.

[0033] A fixation device having tines configured to establish a relatively small active maximum diameter can reduce the risk of damaging or perforating the heart wall when implanting an IMD having that fixation device, for example, in an atrial cavity where available space or volume is very limited. Furthermore, a small active maximum diameter can also increase the likelihood that the tines will return to their preset shape when engaging tissue. If the active maximum diameter is too large, for example, the small anatomical structure of the atrial cavity may restrict the movement of the tines, preventing them from returning to their preset relaxed shape.

[0034] According to an embodiment, each tine comprises, in a relaxed configuration, a first curved portion closer to the anchor member and a second curved portion further away from the anchor member.

[0035] In other words, each tine may comprise two curved sections arranged behind each other along the longitudinal extension of the tine, and the two curved sections may differ from each other with respect to at least one characteristic including the radius of curvature, the direction of curvature, the variation in curvature along the curved section, the length of the curved section, the sweep angle through which the curved section extends, the width of the tines at the curved section, the cross section of the tines at the curved section, the deformation characteristics of the tines along the curved section, etc.

[0036] By appropriately adjusting or optimizing the characteristics of the at least two curved sections, the deformation characteristics of the fixation device when deformed into a pre-deployment configuration can be influenced so that the tines move along the intended deployment trajectory, particularly at the intended emergency angle of attack and / or at the intended maximum penetration depth, during the deformation procedure in the deployment process.

[0037] According to an embodiment, the first curved portion has a first radius of curvature and the second curved portion has a second radius of curvature different from the first radius of curvature.

[0038] For example, the first radius of curvature may be larger than the second radius of curvature. This can reduce mechanical strain on the first curved portion of the tine when it is deformed to the pre-deployment configuration, i.e., when held in the protector sheath. Furthermore, it can enhance the spring force in the second curved portion of the tine. Alternatively, the first radius of curvature may be smaller than the second radius of curvature. Generally, the first radius of curvature may differ from the second radius of curvature by more than 2%, more than 5%, more than 10%, or even more than 20%. When the radius of curvature varies along the curve, the term "radius of curvature" can relate to the average radius of curvature along the curve.

[0039] According to an embodiment, the second curved portion encompasses a sweep angle of between 80° and 150°.

[0040] The sweep angle can be interpreted as the angle between a first direction in which the tines extend to the distal end of the second curved portion and a second direction in which the tines extend to the proximal end of the second curved portion. The lower limit of such sweep angle can be greater than 85°, greater than 90°, greater than 95°, greater than 100°, greater than 105°, greater than 110°, greater than 115°, greater than 120°, greater than 125°, or greater than 130°. The upper limit of the sweep angle can be less than 145°, less than 140°, less than 135°, less than 130°, less than 125°, less than 120°, less than 115°, less than 110°, less than 105°, less than 100°, or less than 95°.

[0041] Generally, the sweep angle at the second bend of the tine can affect how the cantilevered end of the tine moves during the deployment process, and thus can affect the deployment trajectory. By appropriately setting the sweep angle at the second bend, and optionally optimizing such sweep angle depending on other characteristics of the tine, such as the curvature, length, and deformation characteristics of the adjacent portions of the tine, the deployment trajectory can be set to achieve the intended emergency angle of attack and / or maximum penetration depth.

[0042] According to embodiments, each tine may further comprise a proximal straight portion between the first curved portion and the second curved portion in the relaxed configuration. Additionally or alternatively, each tine may further comprise a distal straight portion between the second curved portion and the cantilevered end in the relaxed configuration.

[0043] In other words, the first curved portion and the second curved portion of a tine can be separated from each other by an intermediate straight portion, herein referred to as a proximal straight portion. Additionally or alternatively, a straight portion, herein referred to as a distal straight portion, can exist between the second curved portion and the distal end of each tine. The characteristics of the proximal and / or distal straight portions, including, among other things, the length of each straight portion, can significantly affect the deformation characteristics of the tine. For example, the length of the proximal and / or distal straight portions can be set to be longer, shorter, or equal to the length of the first curved portion and / or the second curved portion. Furthermore, the length of the proximal straight portion can be greater, smaller, or equal to the length of the distal straight portion. Therefore, by appropriately configuring such characteristics of the straight portions, the deployment trajectory can be set to achieve the intended emergency angle of attack and / or maximum penetration depth. The distal straight portion can be oriented parallel to the central axis of the fixation device, and in particular, the distal straight portion can be shorter than the proximal straight portion.

[0044] Each tine has a tine width and a tine thickness, whereby the tine width is at least twice the tine thickness. The tine width and the tine thickness are perpendicular to the longitudinal direction of the tine. In embodiments, at least one tine can have a first curved portion having a tine width that tapers from the first tine width to a second tine width, whereby the second tine width is smaller than the first tine width. The straight portion can have a second tine width. The second curved portion can have a tine width that expands from the second tine width to the first tine width.

[0045] According to embodiments, the fixation device may further comprise an overall height of less than 5 mm in the relaxed configuration. Alternatively or additionally, the fixation device may further comprise an overall width of less than 15 mm in the relaxed configuration. Alternatively or additionally, the fixation device may further comprise an axial clearance distance between the cantilevered ends of the tines and the central axis of at least 4 mm in the relaxed configuration.

[0046] The overall height of a tine may be the maximum dimension of the tine measured in a direction parallel to the central axis of the fixation device. In other words, such overall height extends from the most distal portion of the tine to the most proximal portion of the tine. Preferably, such overall height may be less than 4.8 mm, less than 4.6 mm, less than 4.4 mm, or 4.3 mm or less.

[0047] The overall width of a tine may be the maximum dimension of the tine measured in a direction perpendicular to the central axis of the fastener. In other words, such overall width extends from the left-most portion of the tine to the right-most portion of the tine. Preferably, such overall width may be less than 14.8 mm, less than 14.6 mm, or 14.4 mm or less.

[0048] The axial clearance distance may be the distance of the cantilevered end of the tine relative to the central axis of the fixation device. Such an axial clearance distance should be large enough to allow for favorable deformation characteristics during the deployment process and / or to avoid negative interactions with other components, such as the catheter's protector sheath and / or the IMD housing. In other words, setting the axial clearance distance to a sufficiently large value can increase the probability of engaging the interdigitated tissue at the heart wall during the deployment process without interfering with the insertion tooling or ILP housing.

[0049] According to an embodiment, the fastening device comprises a first set of at least two relatively long tines and a second set of at least two relatively short tines.

[0050] In other words, the fastening device can include at least two different types of tines, the tine types differing from one another at least with respect to their length, for example, the length of the relatively longer tines can be at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, at least 60%, or at least 70% longer than the length of the relatively shorter tines.

[0051] The first set of tines may be configured to implement other deformation characteristics than the second set of tines. For example, the first set of tines may be optimized to engage a first type of tissue, while the second set of tines may be optimized to engage a different second type of tissue. For example, the first set of tines may be optimized to engage tissue having protrusions, such as interdigitated structures, while the second set of tines may be optimized to engage tissue having a smoother surface.

[0052] According to an embodiment, relatively long tines and relatively short tines extend alternately from the anchoring member.

[0053] In other words, every relatively long tine has a relatively short tine as its immediate neighbor along the circumference of the fixation member, and vice versa. The relatively long tines and / or the relatively short tines may be positioned equidistant from one another. Such alternating placement of different tines can improve the engagement characteristics of the fixation device when deployed at the implantation site.

[0054] According to an embodiment, each of the longer tines includes, in the relaxed configuration, a first curved portion closer to the anchor member and a second curved portion further away from the anchor member, and each of the shorter tines includes, in the relaxed configuration, a single curved portion closer to the anchor member and a straight portion further away from the anchor member.

[0055] In the longer tines, the first curved portion may be separated from the second curved portion by an intermediate straight portion. Additionally or alternatively, the longer tines may include a straight portion between the second curved portion and the distal cantilevered end.

[0056] Shorter tines may differ from longer tines in terms of their geometry in that they include only a single curved portion, which may be located closer to the anchoring member, while the straight portion included in the shorter tine may follow the curved portion at a location further away from the anchoring member.

[0057] Different geometries of relatively long and relatively short tines can be optimized for different deformation characteristics during the deployment process.

[0058] For example, according to embodiments, the curved geometry and deformation characteristics of the relatively long and relatively short tines can be configured to implement tines such that the relatively long tines have a smaller emergency angle of attack than the relatively short tines and / or the relatively long tines have a greater maximum penetration depth than the relatively short tines, for example.

[0059] In other words, a first set of tines may be configured to implement a shallower deployment trajectory with a shallower entry angle and / or a smaller maximum penetration depth, while a second set of tines may be configured to implement a steeper and / or more curved deployment trajectory with a steeper initial entry angle and / or the same or even smaller maximum penetration depth than that of the first set of tines.

[0060] In this configuration, the longer tines engage tissue first during deployment. These tines may be more likely to engage areas of tissue with uneven surfaces, such as densely packed pectinate muscles. If the tissue area being deployed is smoother, a set of shorter tines extending later during the deployment process can engage the smoother tissue surface to ensure anchorage. These shorter tines may have a steeper penetration angle but a reduced maximum penetration depth, e.g., less than 0.7 mm, less than 0.6 mm, less than 0.5 mm, less than 0.4 mm, or even 0.3 mm or less. In particular, the maximum penetration depth of the shorter tines may be less than the typical thickness of the thin atrial wall of the atrial cavity, thus reducing the risk of any perforation.

[0061] It should be noted that possible features and advantages of embodiments of the present invention are described herein with reference to various embodiments of fixation devices or embodiments of IMDs including such fixation devices. Those skilled in the art will recognize that features can be transferred from one embodiment to another as appropriate, and that features can be modified, adapted, combined, and / or interchanged to arrive at further embodiments of the present invention.

[0062] Furthermore, while embodiments of the fixation device are described herein primarily with respect to fixation devices for implantable leadless pacemakers, particularly ILPs, configured for implantation within the atria of a patient's heart, it should be noted that the fixation device may also be configured and used to secure other types of implantable medical devices.

[0063] Advantageous embodiments of the present invention will now be described with reference to the accompanying drawings, in which: However, neither the drawings nor the description should be construed as limiting the present invention. [Brief explanation of the drawings]

[0064] [Figure 1] 1 shows a side view of the fixation device. [Figure 2] 2 shows a top view of the fixation device of FIG. 1. [Figure 3] 1 shows a side view of an implantable medical device. [Figure 4A] 1 shows a cross-sectional view of an implantable medical device during an early stage of the deployment process. [Figure 4B] 1A and 1B show cross-sectional views of the implantable medical device when finally fully deployed. [Figure 5A] 10A shows a side view of a fixation device having a second curved section with a different sweep angle during an early stage of the deployment process. [Figure 5B] 10A shows a cross-sectional view of a fixation device having a second curved section with a different sweep angle at an early stage of the deployment process. [Figure 6A] 10A shows a side view of a fixation device having a second curved section with a different sweep angle during an early stage of the deployment process. [Figure 6B] 10A shows a cross-sectional view of a fixation device having a second curved section with a different sweep angle at an early stage of the deployment process. [Figure 7A] 10A shows a side view of a fixation device having a second curved section with a different sweep angle during an early stage of the deployment process. [Figure 7B] 10A shows a cross-sectional view of a fixation device having a second curved section with a different sweep angle at an early stage of the deployment process. [Figure 8] 1 shows an alternative fixation device. [Figure 9] 1 shows an alternative fixation device. [Figure 10] 1 shows an alternative fixation device. [Figure 11] 1 shows an alternative fixation device. [Figure 12] FIG. 1 shows a side view of a fastening device having long and short tines. [Figure 13] 13A-13C show side views of the fixation device of FIG. 12 at different viewing angles. [Figure 14] 13 shows a perspective view of the fixation device of FIG. 12. [Figure 15] 13A-13C show cross-sectional views of the fixation device of FIG. 12 at intermediate stages in the deployment process.

[0065] The drawings are only schematic and are not to scale. Same reference signs refer to the same or similar features.

[0066] Figures 1 and 2 show an anchoring device 1 for anchoring an implantable medical device in the tissue of a patient, in particular for anchoring an ILP inside the atrium of the heart. Figure 3 shows an ILP 3 with such an anchoring device 1 anchored thereto.

[0067] The anchoring device 1 comprises an anchoring member 5 and four elongated tines 7 extending radially outward from the anchoring member 5. The anchoring member 5 is implemented as an annular ring 9. The tines 7 extend integrally from the ring 9 on either side of a central axis 11 of the anchoring device 1 and the ring 9. The tines 7 extend equidistantly around the circumference of the ring 9.

[0068] 1 shows the fixation device 1 in a relaxed configuration, in which the tines 7 are substantially free of any inherent mechanical prestress. In such a relaxed configuration, each tine 7 includes an intermediate portion 12 disposed distally relative to (close to) the anchoring member 5. Additionally, the cantilevered end 21 of each tine 7 is oriented in an opposite proximal direction and / or disposed proximally relative to (away from) the anchoring member 5.

[0069] Each of the tines 7 includes a first curved portion 13 and a second curved portion 15. The first curved portion 13 is positioned closer to the anchoring member 5, while the second curved portion 15 is positioned farther away from the anchoring member 5. Both curved portions 13, 15 curve in the same direction. However, the radius of curvature R1 of the first curved portion 13 may be different from the radius of curvature R2 of the second curved portion 15. Furthermore, a proximal straight portion 17 extends between the first curved portion 13 and the second curved portion, and a distal straight portion 19 extends between the second curved portion 15 and a cantilevered end 21 at the free end of each tine 7. The tines 7 extend along an overall height H of 4.3 mm. The overall width W of the fixation device 1 is 14.4 mm, and such overall width may also be referred to as the diameter of the fixation device 1. The axial clearance distance D between each of the cantilevered ends 21 of the tines 7 on one side and the central shaft 11 on the other side is 4.5 mm.

[0070] The tine array of the fixation device 1 is optimized for atrial tissue properties such as thickness and elasticity. It can be made of a superelastic material such as Nitinol, manufactured by laser cutting from Nitinol tubing and setting the desired shape. The tine legs typically have a constant thickness and width along their entire length, and the tine tips can terminate with a radius along their width. The entire component is subjected to finishing processes such as bead blasting, etching, and electropolishing to remove sharp edges and reduce corrosion tendencies.

[0071] FIG. 3 illustrates an IMD 3 implemented as an implantable leadless pacemaker, particularly configured for implantation within the atrium of the heart. The IMD 3 includes a housing 23. A controller 25 is contained within the housing 23 and configured to control the function of the IMD 3. An energy source 27, such as a battery, is also contained within the housing 23 and configured to provide electrical energy to the controller 25. Electrodes 29 are exposed at the distal end of the IMD 3, i.e., the electrodes 29 protrude beyond the housing 23. The electrodes 29 are electrically connected to the controller 25 so that voltage pulses generated by the controller 25 can be applied to the electrodes 29. The IMD 3 further includes a fixation device 1 attached to the housing 23 at the distal end of the housing 23.

[0072] 4A and 4B visualize different phases or stages during a deployment process for anchoring an IMD 3 to cardiac tissue 33, for example, in the atrial wall. Prior to such a deployment process, a catheter having a protector sheath 31 at its distal end is introduced into a patient's heart such that the distal end of the protector sheath 31 abuts the surface of the cardiac tissue 33. Prior to initiating the deployment process, the IMD 3, along with its fixation device 1, is fully contained within the protector sheath 31. At that point, the fixation device 1 is positioned distally relative to the IMD 3, and the tines 7 are disposed in a pre-deployment configuration, mechanically deforming and subjecting the tines 7 to an inherent prestress such that the fixation device 1 may be contained within the tubular protector sheath 31 and have a geometry in which the intermediate section 12 as well as the cantilevered ends of the tines 7 are positioned and directed distally relative to the anchoring members 5.

[0073] Next, upon initiating the deployment process as visualized in FIG. 4A , the catheter, along with the protector sheath 31, is continuously retracted, thereby continuously ejecting the IMD 3, along with the fixation device 1, from the protector sheath 31 at the distal open end of the protector sheath 31. As the cantilevered ends 21 of the tines 7 form the distal-most portion of the fixation device 1 in the pre-deployment configuration, these cantilevered ends 21 are ejected from the protector sheath 31 first. At that point, depending on the overall geometry of the fixation device 1, and particularly the shape and curvature of the tines 7, the tines 7 with their cantilevered ends 21 are positioned and ejected in a predetermined ejection direction. Furthermore, because the tines 7 are deformed and therefore subject to inherent prestress, the cantilevered ends 21 of the tines 7 tend to move along the deployment trajectory to relieve these inherent prestresses as they are ejected from the protector sheath 31.

[0074] 4A, such deployment trajectories extend at an emergency angle of attack α relative to the central axis 11 of the fixation device 1 during the initial deformation stage of the deployment process. Such emergency angle of attack α corresponds to a complementary angle of entry β that defines the angle between the deployment trajectories during the initial stage of deformation relative to the surface of the cardiac tissue 33, such surface being generally disposed perpendicular to the central axis 11.

[0075] As described herein, the shape of the tines 7 is specifically optimized to enable a pre-deployment configuration and an early stage of deformation manipulation in the deployment process, such that the emergency angle of attack α is between 40° and 90°, preferably between 75° and 90°, and the penetration angle β is less than 50°, preferably less than 15°. Due to such a shallow penetration angle β, the cantilevered ends 21 of the tines 7 penetrate the abutting cardiac tissue 33 at a shallow angle, thereby enabling a shallow deployment trajectory during the deployment process.

[0076] In other words, when deployed from the implant protector cup, the particular geometry of the tines 7 causes the tips of the tines 7 to approach the tissue 33 at an angle α that is nearly perpendicular to the axis 11 of the protector cup, allowing for an extremely shallow penetration depth PD. The primary direction of force from these tines 7 is radial, driving the tines 7 laterally through the tissue 33, increasing the probability of engaging, for example, the interdigitated structures 35 of the tissue 33 while minimizing the possibility of perforating the atrial wall.

[0077] In summary, as a result of the shallow deployment trajectory, the maximum penetration depth PD can be small, reducing the risk of damaging or perforating the cardiac tissue 33, even if the cardiac tissue 33 is part of the thin atrial wall surrounding the atrial cavity.

[0078] 4B shows the final stage of the deployment process when the fixation device 1 is fully deployed and has substantially reached its relaxed configuration. At that point, during the deployment process, the tines 7 move through and rearwardly engage a portion of the cardiac tissue 33, thereby anchoring the fixation device 1 along with the IMD 3 in the cardiac tissue 33. The maximum thickness of the portion of the fixation device 1 rearwardly engaged by the tines 7 generally corresponds to the maximum penetration depth PD.

[0079] 5 to 7 show embodiments of the fixation device 1 which differ in terms of the sweep angle γ2 of the second curved portion 15. In FIG. 5, this sweep angle γ2 is 130°. In FIG. 6, the sweep angle γ2 is 115°. In FIG. 7, the sweep angle γ2 is 100°.

[0080] 5A, 6A, and 7A, the magnitude of the sweep angle γ2 directly affects the emergency angle of attack α when the fixation device 1 is ejected from the protector sheath 31 and deployed from its pre-deployed configuration to its relaxed configuration. In the illustrated example, when the sweep angle γ2 of the second curved portion 15 is 130° (see FIG. 5B), the emergency angle of attack α1 is approximately 90°, while when the sweep angle γ2 of the second curved portion 15 is 100° (see FIG. 7B), the emergency angle of attack α3 is approximately 60°.

[0081] In other words, the variations of the embodiment shown in Figures 5-7 involve a gradual decrease in the sweep angle of the second radius of curvature, ranging from about 130° to about 100°. As the sweep angle decreases, the encirclement angle of the tine trajectory increases. This, in turn, increases both the angle of attack when loaded onto the catheter and the estimated maximum penetration depth PD. The first embodiment visualized in Figure 5 is designed for lateral engagement only and has a penetration depth of 0 mm by design. The embodiments visualized in Figures 6 and 7 increase the maximum allowable penetration depth from about 0.2 mm to 1 mm.

[0082] 8 to 11 show various embodiments of the fastening device 1 in which the tines 7 have different geometric shapes.

[0083] In the embodiment shown in FIG. 8, the first curved portion 13 includes a larger first radius of curvature R1 of approximately 1.5 mm with a sweep angle γ1 of 150°. The first curved portion 13 is followed by a proximal straight portion 17 having a length lp of approximately 2.54 mm. The second curved portion 15 includes a smaller second radius of curvature R2 of approximately 0.8 mm with a sweep angle γ2 of 90°. The second curved portion 15 is followed by a distal straight portion 19 having a length ld of approximately 2.22 mm. Such a geometry can reduce distortion of the first curved portion 13 and enhance the springiness of the second curved portion 15 when retracted into the implant tooling.

[0084] In the embodiment shown in Figure 9, the geometry of the tine profile is reduced to optimize anchoring in the narrowed atrial appendage. In such an embodiment, the straight segments (i.e., proximal straight section 17 and distal straight section 19) are eliminated, and instead, the tine profile is a series of continuously varying radii. A first protruding radius R1 is attached tangentially to the base ring 9 and is, for example, 1 mm to 2 mm (1.02 mm is the example visualized in Figure 9) at a sweep angle γ1 of approximately 90°. A spline extends the first radius of curvature to a second, more pronounced radius R2 of approximately 1.25 mm at a sweep angle γ2 of approximately 115°.

[0085] Alternatively, the first radius of curvature R1 and the second radius of curvature R2 can be slightly increased so that the tine profile has two different radii, as shown in Figure 10. The first radius of curvature R1 is attached tangentially to the base ring 9 and has a radius R1 of 1-2 mm and a sweep angle γ1 of approximately 90°. The second radius of curvature R2 is attached tangentially to R1 and has a radius R2 of 1-2 mm and a sweep angle γ2 of approximately 120°.

[0086] 11 shows another alternative embodiment of the fastening device 1, in which the tine profile is a spline-based geometry terminating with a terminal cantilevered end 21 tip parallel to the central axis 11.

[0087] 12-15 show embodiments of the fastening device 1 having different types of tines 7. Specifically, the fastening device 1 includes relatively long tines 37 and relatively short tines 39. In the example shown, there are four relatively long tines 37 and four relatively short tines 39 extending alternately from the circumference of the anchoring member 5.

[0088] The relatively long tines 37, when in their relaxed configuration, have a similar or identical profile to that described above with respect to the embodiment of Figures 1 and 5-11. In particular, the relatively long tines 37 include a first curved portion 13, a second curved portion 15, and optionally a proximal straight portion 17 and a distal straight portion 19. The relatively short tines 39 include only a single curved portion 41 proximal to the anchoring member 5 and a straight portion 43 further from the anchoring member 5.

[0089] In that regard, the curved geometry and deformation characteristics of the relatively long tines 37 and the relatively short tines 39 are configured to implement the tines such that the relatively long tines 37 have a smaller emergency angle of attack than the relatively short tines 39 and / or the relatively long tines 37 have a greater maximum penetration depth PD than the relatively short tines 39, as visualized in the initial deployment stage diagram shown in FIG. 15.

[0090] In other words, the embodiment shown in Figures 12-15 is a multi-tine array optimized for anatomical variations in the atrial wall, including regions of interdigitated and smooth atrial wall. It can be made from a superelastic material, such as Nitinol, manufactured by laser cutting from Nitinol tubing and setting the desired shape. All tine legs are of a consistent thickness and width along the entire length of the tine, and each tine tip terminates in a radius. The entire component is then subjected to a finishing process, such as bead blasting or electropolishing, to remove sharp edges and reduce corrosion propensity.

[0091] One set of tines 37 in this array, four of which are shown, are equidistant around the ring of tines 9 and are shaped as described above, i.e., beginning at the transition from the base ring 9 that connects all of the tines 37, 39 together, the longer tines 37 in this set consist of a small radius followed by a long straight section followed by a larger radius followed by a short straight section. Alternating tines 39, four of which are shown, are shorter, consisting of a radius followed by a straight section. In this embodiment, the first radii of all tines 37, 39 are all equal. The straight sections of the shorter tines 39 are substantially equal to the central axis 11 of the device in the unrestrained state.

[0092] The longer tines 37 engage tissue first during deployment. These tines 37 have a high probability of engaging in areas of dense pectinate muscle. If the deployment area is smoother, a second set of shorter tines 39 engages the smooth atrial wall for secure anchoring. These tines have a higher angle of attack α, but a reduced maximum penetration depth PD of approximately 0.3 mm, which is less than the thickness of thin atrial wall regions characterized in the literature.

[0093] Finally, it should be noted that the term "comprising" does not exclude other elements or steps, and "a" or "an" do 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 shall not be construed as limiting the scope of the claims. [Explanation of symbols]

[0094] 1 Fixing device 3 Implantable medical devices 5 Fixing member 7 Tyne 9 Ring 11 Center axis 12 Middle section 13 First curved section 15 Second curved section 17 Proximal straight section 19 Distal straight section 21 Cantilever end 23 Housing 25 Controller 27 Energy Sources 29 electrode 31 Protector sheath 33 Heart Tissue 35 Pectinate structure 37 Relatively long tines 39 Relatively short tines 41 Curved section 43 Straight section H Overall height W Full width D Axial clearance distance Α Emergency angle of attack β penetration angle PD maximum penetration depth R1 Radius of curvature of the first curve R2 Radius of curvature of the second curve γ1 Sweep angle of the first curve γ2 Sweep angle of the second curve lp Length of the proximal straight section ld Length of the distal straight section

Claims

1. A fixation device (1) configured to fix an implantable medical device, in particular an implantable leadless pacemaker (3), to tissue (33) of a patient, comprising: an anchoring member (5) for anchoring the fixation device (1) to the implantable medical device (3); at least two tines (7; 37, 39) extending from the anchoring member (5) on different sides relative to the central axis (11) of the fastening device (1); the tines (7; 37, 39) have a curved geometry and are elastically deformable so as to be reversibly deformable between a relaxed configuration and a pre-deployed configuration; In the relaxed configuration, the tines (7; 37, 39) are free from any inherent mechanical prestress, the intermediate portions (12) of the tines (7; 37, 39) are arranged distally relative to the anchoring member (5), and the cantilevered ends (21) of the tines (7; 37, 39) are at least one of directed and arranged proximally relative to the anchoring member (5), In the pre-deployment configuration, the tines (7; 37, 39) are mechanically deformed and inherently prestressed to assume a geometry that allows the fixation device (1) to be placed in a tubular protector sheath (31), with the intermediate section (12) and the cantilevered ends (21) of the tines (7; 37, 39) positioned and oriented distally relative to the anchoring member (5), The curved geometry and deformation characteristics of the tines (7; 37, 39) are configured such that, during an initial stage of the deformation procedure in which the tines (7; 37, 39) are transformed from their pre-deployed configuration to their relaxed configuration due to their inherent prestress, the cantilevered ends (21) of the tines (7; 37, 39) are displaced along a deployment trajectory extending at an emergency angle of attack (α) of 40° to 90° relative to the central axis (11) of the fixation device (1).

2. 2. The fixing device according to claim 1, wherein the curved geometry and deformation characteristics of the tines (7; 37, 39) are configured to implement an emergency angle of attack (α) of between 75° and 90°.

3. 2. The fixation device according to claim 1, wherein the curved geometry and deformation characteristics of the tines (7; 37, 39) are configured such that the maximum penetration depth (PD) of the tines (7; 37, 39) is less than 1 mm, the maximum penetration depth (PD) corresponding to the maximum distance of the deployment trajectory in a direction parallel to the central axis (11) of the fixation device (1) relative to the position of the cantilevered end (21) of the tine when the tine is in a pre-deployed configuration.

4. 2. The fixation device according to claim 1, wherein the curved geometry and deformation characteristics of the tines (7; 37, 39) are configured such that the maximum active diameter of the fixation device (1) is less than 15 mm, the maximum active diameter corresponding to the maximum width of the deployment track in a direction perpendicular to the central axis (11) of the fixation device (1).

5. 2. The fastening device according to claim 1, wherein each tine (7; 37, 39) comprises, in the relaxed configuration, a first curved portion (13) closer to the anchoring member (5) and a second curved portion (15) further away from the anchoring member (5).

6. 6. The fixation device according to claim 5, wherein the first curved portion (13) has a first radius of curvature (R1) and the second curved portion (15) has a second radius of curvature (R2) different from the first radius of curvature (R1).

7. 6. The fixation device according to claim 5, wherein the second curved portion (15) encompasses a sweep angle (γ1) of between 80° and 150°.

8. Each tine (7; 37, 39), in said relaxed configuration, a proximal straight section (17) between the first curved section (13) and the second curved section (15); 6. The fixation device of claim 5, further comprising at least one of the second curved portion (15) and a distal straight portion (19) between the cantilevered end (21).

9. 9. The fixation device according to claim 8, wherein the distal straight portion (19) is oriented parallel to the central axis (11) of the fixation device (1).

10. The fixation device (1) in the relaxed configuration: Overall height (H) of less than 5 mm, an overall width (W) of less than 15 mm, and 2. The fastening device of claim 1, further comprising at least one of: an axial clearance distance (D) between the cantilevered end (21) of the tine and the central axis (11) of at least 4 mm.

11. 2. The fastening device of claim 1, wherein the fastening device (1) comprises a first set of at least two relatively long tines (37) and a second set of at least two relatively short tines (39).

12. 12. The fastening device of claim 11, wherein the relatively long tines (37) and the relatively short tines (39) extend alternately from the anchoring member (5).

13. Each of the relatively long tines (37) includes, in the relaxed configuration, a first curved portion (13) that is closer to the anchoring member (5) and a second curved portion (15) that is further away from the anchoring member (5); 12. The fastening device of claim 11, wherein each of the relatively short tines (39) comprises, in the relaxed configuration, a single curved portion (41) close to the anchoring member (5) and a straight portion (43) further away from the anchoring member (5).

14. The curved geometry and deformation characteristics of the relatively long tines (37) and the relatively short tines (39) are the relatively long tines (37) have a smaller emergency angle of attack (α) than the relatively short tines (39); and 12. The fastening device of claim 11, wherein the relatively long tines (37) are configured to implement the tines with at least one of: a maximum penetration depth (PD) greater than the relatively short tines (39).

15. An implantable medical device (3), a housing (23); a controller (25) contained in the housing (23) for controlling the functioning of the medical device (3); an energy source (25) contained in said housing (23) for supplying said controller (25); An implantable medical device (3) comprising the fixation device (1) according to claim 1, wherein an anchoring member (5) is anchored to the housing (23).

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