Pacing lead with folding anchoring tines for an implantable medical device, especially for a heart pacemaker

p0001The invention relates to a probe for an implanted medical device, particularly for pacemaker.

p0002These probes, including endocardial leads for pacemakers, comprise retention systems mounted on their distal end, close to the actual pacing electrode (or electrodes in the case of a bipolar lead). Various retention or anchoring systems have been proposed, including shaped fixing brackets or "whiskers" that become jammed themselves between endocardial trabeculae.

p0003The US Patent 4,236,529 describes such a probe, such as "passive fixation" that is to say, in which the barbs are housed themselves up by their elasticity, ensuring inclined shape an anti-return effect without any special maneuvering.

p0004It has also been proposed probes mechanical actuator, for example, in US-A-4,945,922, US-A-4957118 or EP-A-0546414 in which the barbs, initially folded against the body the probe, are deployed by operating a coaxial mandrel inserted into the probe at the time of implantation and the rotation comes to protrude beards once the distal end of the probe positioned at the desired location.

p0005The interest in recent fasteners is that they are generally reversible, so as to allow an explantation of the probe, for example after folding barbs by a reverse operation of a mandrel inserted into the central axial channel of the probe. However, these probes are both bulkier (the body diameter is more important because it is necessary to provide an axial channel) and a more complex structure - hence more expensive - due to the need for a mechanical transmission system of rotational movement of the mandrel and of converting the rotational movement into a deployment movement of the articulated beards.

p0006One of the aims of the present invention is to provide a probe which can be implemented without actuator of the anchoring system. Another object of the invention to provide such a probe that is removable without risk of tearing of trabeculae or fibrous tissue may have formed around the end of the probe.

p0007The probe of the present invention thus combines the advantages of small diameter, simple structure and therefore inexpensive, easy implantation without using special instrumentation and possibility of extraction without damaging the surrounding tissue. It allows, as will be explained below, using a sealed and independent probe body of barbs deployment system.

p0008To this end, the probe according to the invention comprises, firstly, a cylindrical body carrying the electrode or the electrodes of the probe and, on the other hand, a removable sleeve styling the electrode body. The sleeve has a sleeve of the retaining ring on the body, the mounting of the ring on the body being removable so as to allow the subsequent dissociation of the sleeve from the body by axial traction of the latter, and means deformable s' extending from the retaining ring and may take two stable configurations. The transition from the first to the second configuration results from an external force exerted axially on the sleeve and the deformable means essentially not projecting radially in the first configuration, so as to allow the insertion in place of the probe, and making essentially radially into the second configuration so as to form anchoring barbs.

p0009Preferably, the anchoring barbs of the deformable means are interconnected by a moving element surrounding the body and sliding along the latter between an initial position and a final position, these two positions corresponding respectively to the two stable configurations means deformable, these deformable means forming link means between the retaining ring and the movable member.

p0010In a first embodiment, the moving element is a skirt placed in a distal position relative to the ring, said skirt projecting axially from the body in the initial position and do not protrude into the end position, and the passage of the first to the second configuration resulting from the external force exerted axially in the proximal direction on the distal end of the skirt during docking thereof with a wall against which is to contact the electrode.

p0011Advantageously, it is then provided means for increasing the friction between the body and skirt in the vicinity of the final position, especially when the body presents an increased outside diameter and / or the skirt presents an increased inside diameter, or when the body has reliefs on its outer surface and / or the skirt presents portions in relief on its inside surface.

p0012The body may have a rear stop shoulder of the final position, and it may further be provided on the front face of the body an anchor screw, said screw being covered by the skirt in the initial position and projecting axially in final position. This latter configuration prevents tissue from trauma may be caused by the anchoring screw during insertion of the probe to its placement in a heart chamber.

p0013In a second embodiment, the moving element is a ring disposed proximal relative to the ring, and the transition from the first to the second configuration results from the external force exerted axially in the distal direction on the ring by manipulation of a threaded sleeve on the body. In this case, the body preferably carries a peripheral locking groove receiving and immobilizing the ring in the stroke end.

p0014In all cases, the connection means preferably comprise a plurality of bridges of elastically deformable material, in particular bridges having a concave profile in section, the concavity being reversed between the first and second configuration.

p0015Moreover, the retaining ring preferably has a substantially ring and the cylindrical body has a circular cross-section circumferential groove receiving the O-ring, groove and the torus having substantially identical counterparts diameters so as to enable any point local pivot the ring in the throat.

p0016We will now describe examples of implementation of the invention.

p0017Figure 1 is an exploded view of the distal end perspective view of a probe according to a first embodiment of the invention showing the two main elements thereof, the body and sleeve.

p0018Figure 2 is a longitudinal section on a radial plane of the sleeve.

p00193 illustrates the deformation behavior of the sleeve during the introduction of the probe upon contact with the heart wall, respectively, for the sections AA and BB of Figure 2.

p0020Figures 4 to 6 show the successive stages of implementation of the probe.

p0021FIG 7 is a perspective view showing the configuration of the probe according to the first embodiment of the invention, in its final docked position.

p00228 illustrates the manner in which probe can be removed from the body despite the formation of fibrous tissue around thereof.

p00239 illustrates an advantageous variant of this sensor, wherein is provided a fixing screw.

p0024Figure 10 is similar to FIG 1 for a second embodiment of the invention.

p0025Figure 11 is a longitudinal section on a radial plane, the sleeve of the probe of Figure 10.

p0026Figures 12 and 13 illustrate how the barbs are deployed from the probe of Figure 10.

p0027FIGS 1-9 refer to a first embodiment of the invention.

p0028In Figure 1, reference 10 designates a rigid cylindrical body carrying the actual stimulation electrode 12 a pacemaker probe, which shows a portion of the flexible conductor 14. The other end of the probe (end proximal, not shown) comprises, in a manner itself conventional, a connector for its electrical connection to the remote pacemaker.

p0029So characteristic of the invention there is provided a cylindrical sleeve 16 which caps the body 10 of the electrode (as illustrated for example Figure 4) and made for example of a type of silicone ETRQ7 47.80 a Shore hardness about 80, or a type of polyurethane Corethane (trademark) of Corvita society. The sleeve 16 can slide freely, or with a slight friction (as explained below) on the body 10 in axial direction. A ring 18, preferably O, is snapped on a section of homologous peripheral groove 20 formed on the body 10, the ring 18 being connected to the front portion 22 of the sleeve by a plurality of bridges 24, which will be explained below below in more detail the role. The ring 18 has a necking force relative to the body 10 to avoid inadvertent detachment of the sleeve 16 during insertion of the probe to the cardiac cavity.

p0030As can be seen in Figures 2 and 3, the bridge 24 (which are positioned on the drawing three in number, but this number is in no way limiting) have a central section of reduced width with, in the free state of origin (that illustrated in figures 1 and 2) a concavity 26 facing the central axis of the sleeve (view from the left of Figure 3). The proximal ends 30 of the bridges, that is to say the ends facing the driver 14, are connected to the ring which, because of its circular section 28 constitutes a hinge point allowing rotation of the proximal end 30 around the center of this section 28, as shown in successive views of Figure 3.

p0031This rotation is against the natural biasing of the bridge of material 24, and causes an inversion of the concavity 26, thereby maintaining the assembly in another stable state. In other words, in Figure 3 the views of left and right correspond to two stable states (stability resulting from the concavity of the proximal parts 30, rotated, respectively, towards the axis of the sleeve of the ring and away from this axis) and the central view corresponds to an intermediate position, unstable.

p0032The passage from one position to the other occurs in the manner illustrated in Figures 4 to 6.

p0033When the probe is gradually approached to the wall 32 of the myocardial cavity (Figure 4), the body 10 and the sleeve 16 have the configuration illustrated in Figures 1 and 2 and Figure 3, seen from the left. In this phase, the distal portion 22 of the probe protects the electrode 12 of the various friction, for example against other probes already installed.

p0034The approach movement (arrow 34) continues until the distal end of the sleeve comes into contact with the wall 32 of the cavity (Figure 5).

p0035Once docking thus produced, further axial advancement movement 34 of the probe induces a reaction force 36 on the distal end of the sleeve 16. This reaction 36 is transmitted to the flexible bridge 24 (arrow 38) due to the rigidity of the distal portion 22 of the sleeve. The buckling point is located to the area having the moment of inertia of the lower, that is to say at the most constricted part of the bridges.

p0036This has the effect of causing a rotation of the proximal ends of the bridges 24 around the ring 18 (shown schematically by the rotation arrow 40 in Figure 5) with radial spacing correlative of the central portion of the bridge 24 (arrow 42). The situation bridges in Figure 5 essentially corresponds in cross section to the central view of figure 3.

p0037To prevent, by reaction, a recoil of the ring who would go out of her throat 20, advantageously provides a shoulder 52 (Figures 4-6) behind the groove; in other words, the body 10 has proximal side of the groove a diameter greater than the diameter it distally.

p0038The movement thus described continues until the abrupt change in concavity of the bridges 24 (Figure 6 and right side of Figure 3) which has the effect, firstly, to completely uncover the electrode 12 due to the 44 complete translation of the sleeve 16 and, secondly, to enable the full deployment radial bridges 24, the part of smaller radius of curvature will be radially and with a slight inclination in the proximal direction, taking the form of barbs which will be able to bear against the trabeculae in myocardial cavity by transmitting an action-reaction effect a slight pressure of the electrode 12 against the wall 32.

p0039The barbs are thus constituted by the two parts of each bridge 24, folded at the central area, where the section is the lower, as can be seen very clearly in the perspective view of Figure 7.

p0040Advantageously, it is provided to reduce the friction of the sleeve 16 on the body 10 by placing an appropriate lubricant such as a hydrogel, biocompatible course, between these two elements or one of them.

p0041Moreover, advantageously, sleeve and body are so designed that, in the sliding movement of the sleeve on the body, the friction is low early in the race (Figures 4 and 5 position) and largest at the end of displacement (position of Figure 6) to lock the system in position, due to additional resistance to be overcome if one wanted to return to the original position. In other words, it is desired to make the transition from the initial position to the final position of the less reversible as possible. This can be achieved for example by giving the one and / or the other of the cooperating parts a very slight taper and / or by providing light of reliefs on the inner surface of the sleeve 16 and / or on the outer surface of the body 10.

p0042Note also that inadvertent operation of the system during the introduction is prevented because the bridges 24 are pressed against the body 10 of the probe by the spring bias of the vein walls.

p0043Finally, the sleeve material may advantageously contain radiopaque particles so that the practitioner can visually check for proper deployment of the barbs during surgery.

p0044A major additional advantage of the invention lies in the ease of extraction of the probe.

p0045Indeed, as illustrated in Figure 8, after months fibrosis 46 has generally wrap the barbs formed by the folded 24 bridges, including the volume 48 between the two branches of each folded beard. The connection between beard and fibrosis is much stronger than the traditional configuration of a full beard, flat or cylindrical. Therefore, a pull exerted on the body 50 of the probe 10 cause almost invariably a tearing of fibrous tissue and therefore damage to the myocardial wall.

p0046But advantageously, the ring 18, which is made of a material such as polyurethane or silicone with a Shore hardness from 30 to 50, has a slight elasticity allowing a radial distension to the exit of the groove 20 and therefore the sliding of the probe , the entire removable sleeve remaining in place fully embedded in the fibrosis.

p0047It is thus possible with this dissociation of the sleeve from the body, perform easily and without damage to the tissues withdrawal of the probe by a simple axial traction movement exerted on the driver.

p0048In an advantageous variant of the first embodiment, illustrated in FIG 9, the sensor head can provide an anchoring screw 54 placed on the front part of the probe, in a manner known per se. The skirt 22 thus plays a role of protecting the vein wall at the time of insertion of the probe. On the other hand, the combination of the screw and the sleeve of the invention allows to make sure, once the screw anchored to the myocardial wall, the barbs have been deployed, that is to say the sleeve is in the configuration of FIG 7.

p0049Figures 10 to 13 illustrate a second embodiment of the invention.

p0050In this second embodiment, the movable member is no longer the skirt 22, as in the first embodiment, but a ring 56 which may be of a shape and dimensions comparable to the ring 18, and which is connected to thereof by a plurality of bridges 24 which play the same role than in the first embodiment (where the same reference numerals are used for one and the other embodiment, these references correspond to elements corresponding functionally similar).

p0051Unlike the previous case where the movable member located forward (distally) from the retaining ring 18, in this second embodiment the movable ring 56 is located behind (proximally) of the same ring 18.

p0052Therefore, the displacement of the movable member is no longer done by a front biasing at the coming into contact of the movable skirt with the myocardial wall (that is to say a force exerted axially on the distal end the sleeve) but by a rear load, exerted by means of a sheath 58 (figures 12 and 13) pushed onto the conductor to the probe (that is to say a force exerted axially on the proximal end the sleeve). The increase in distal direction (60 in Figure 12) of the sheath continues until the contact of the movable ring 56, which will therefore be pushed forward (Figure 1), thus causing bending of the bridges 24. the final position is determined by a peripheral groove 62 into which is permanently fit the movable ring 56, the bridges 24 then being in full flexion position in the same way as was explained for the first embodiment.

p0053The operation ends with the removal of the sheath 58, which is advantageously a "peelable" disposable sheath, which can be split longitudinally in two halves as and extent of its withdrawal

p0054This second embodiment has the same vis-a-vis advantage of extracting the previous embodiment, that the sleeve can easily become detached from the probe body to permit, in the same way, extracting this last.