MICROPROBE FOR DETECTION / STIMULATION THAT CAN BE IMPLANTED IN VENOUS, ARTERIAL OR LYMPH SYSTEM NETS

Description

[0001] The invention relates generally to "active implantable medical devices" as defined by Directive 90 / 385 / EEC of 20 June 1990 of the Council of the European Communities.

[0002] This definition specifically includes cardiac implants designed to monitor heart activity and generate stimulation, defibrillation, and / or resynchronization pulses in the event of an arrhythmia detected by the device. It also includes neurological devices, cochlear implants, drug delivery pumps, implanted biological sensors, and so on.

[0003] These devices include a unit generally referred to as a "generator", electrically and mechanically connected to one or more intracorporeal "probes" equipped with electrodes designed to come into contact with the tissues on which stimulation pulses are to be applied and / or an electrical signal collected: myocardium, nerve, muscle, ...

[0004] The present invention relates more specifically to a detection / stimulation microprobe intended to be implanted in venous, arterial or lymphatic networks.

[0005] The current principle of electrical tissue stimulation is based on a device, generally called a "probe", which is an object implanted through various vessels, including veins, arteries or lymphatics, and whose function is to transmit an electrical signal to the target tissue while ensuring the following properties: Ease of implantation by the physician into the patient's vascular network, and in particular ease of: advancing the probe through the vessels by pushing, guiding the probe along tortuous paths and through branches, and transmitting torques; X-ray visibility to allow the physician easy navigation through the vessels of the network under X-ray fluoroscopy; atraumatic contact of the probe with the veins, which requires a highly flexible structure and the absence of rigid transitions or sharp angles; ability to transmit an electrical signal to the tissues and to perform stable monopolar or multipolar electrical measurements; biocompatibility with living tissues for long-term implantation; ability to connect to an implantable signal transmission device; suitability for sterilization (gamma rays, temperature...) without suffering damage; biostability, in particular resistance to corrosion in the living environment and resistance to mechanical stress in fatigue related to patient and organ movements; compatibility with MRI imaging, particularly important in neurology.

[0006] The current architecture of probes meeting these needs can be summarized as a generally hollow structure to allow the passage of a mandrel or guide wire, and comprising components such as insulated conductive cables, connected to mechanical electrodes to ensure electrical conductivity, radio opacity...

[0007] These are therefore probes requiring a complex assembly of a large number of parts, wires and associated insulators, creating significant risks of breakage given the long-term mechanical stresses to which they are exposed.

[0008] Examples of such probes are given in EP 2145648 A1, US 6 192 280 A and US 7 047 082 A, or in US 5 246 014 A.

[0009] Among the difficulties encountered, we can mention the management of stiffness gradients related to the mechanical parts used, which strongly affect the implantability and mechanical resistance properties in the long term (fatigue).

[0010] Furthermore, in order to seal the internal lumen of the probes, whose entry of blood would degrade performance during insertion and in the long term, valves and other complex devices are used which present significant associated risks.

[0011] Other difficulties may also arise in terms of assembly fatigue. Indeed, any area of ​​stiffness transition is likely to induce fatigue risks, difficulties in sterilization due to the presence of hard-to-reach areas, and problems with the strength of conductor junctions at the connection with the electrodes and the connector.

[0012] Furthermore, the clinical trend in the field of implantable probes is to reduce their size in order to make them less invasive and easier to manipulate through the vessels.

[0013] The current size of implantable probes is typically in the range of 4 to 6 French (1.33 to 2 mm) in their active part, i.e. the most distal part bearing the electrode(s) - even if the probe body, in the less distal part, uses conductors of smaller diameter, as for example in the aforementioned US 5 246 014 A which, at the level of the probe body, certainly includes a conductor whose diameter does not exceed 1 French (0.33 mm), but whose overall diameter of the active distal part, at the location of the anchoring screw, is several French.

[0014] However, it is clear that reducing the size of the probes would increase their complexity and impose technical constraints that generate risks.

[0015] However, such a reduction, to less than 2 French (0.66 mm) for example, would open up prospects for medical applications in various fields ranging from cardiology to neurology in the presence of a venous, arterial or even lymphatic network, such as the cerebral venous network or the venous network of the coronary sinus.

[0016] Today, electrical stimulation technology has enabled significant advances in the field of neuromodulation, which involves stimulating target areas of the brain for the treatment of Parkinson's disease, epilepsy, and other neurological disorders.

[0017] It is therefore conceivable that this type of technology could be used to treat new areas that are currently difficult to access, using small stimulation probes, or "microprobes," which are highly robust to ensure long-term biostability. Such a technique would allow for a less invasive approach to these treatments and, above all, greater efficacy of the administered treatments.

[0018] It would be possible to connect one or more microprobes through the network of vessels in question to their target location. Due to their small size, their placement could be performed using guidance devices currently used in interventional neuroradiology for the release of shunts ( coils ) during the treatment of intracranial aneurysms.

[0019] Therefore, the aim of the present invention is to propose such a small "microprobe" which would be in conformity with the general properties of implantable probes as listed above, while reducing their complexity and, consequently, their final cost.

[0020] The size of this microprobe should notably allow access to very small venules, currently inaccessible with larger devices. The microprobe of the invention should also significantly facilitate navigation within venous, arterial, or lymphatic networks due to its flexibility, enhanced by its small size.

[0021] According to the invention, this goal is achieved by means of a probe according to claim 1.

[0022] Thus, it is understood that with a diameter not exceeding 0.50 mm, the heart cable constituting the microcable of the microprobe according to the invention has great flexibility, favorable to its manipulation by the doctor, in particular during its implantation when it is necessary for example to introduce it into networks of vessels with strong tortuosity and many branches and to avoid trauma that could be caused by much more rigid probes, incompatible with the tissues.

[0023] On the other hand, choosing a stranded, multi-wire structure composed of very fine strands, each with a diameter of no more than 40 µm, preferably between 20 and 40 µm, increases the resistance of the heart cable to mechanical fatigue caused by patient and organ movement, given that the bending breaking strength of a wire is roughly inversely proportional to its diameter. To further enhance this important biostability, it is advantageous for the strands themselves to be made of a structural material with high intrinsic fatigue resistance, such as the materials mentioned above: stainless steel, cobalt alloys, titanium, and the NiTi alloy, also known as nitinol. In addition to these metals, which ensure the mechanical properties of the heart cable, a radiopaque material is used to make the microprobe visible to X-rays during its placement by the physician.The radio-opaque material can be chosen from tantalum (Ta), tungsten (W), iridium (Ir), platinum (Pt), gold (Au) and their alloys.

[0024] Specifically, the invention provides that the resulting composite structure of the core cable can be made from composite strands consisting of at least a structural material and a radiopaque material, or from strands made of structural material and strands made of radiopaque material. The plurality of strands in the bundle advantageously comprises between 15 and 300 strands.

[0025] To establish electrical contact with tissues and transmit the electrical signal, the invention proposes a solution that uses the core cable itself to form the microprobe electrodes, with exposed areas in an insulating layer surrounding the cable. The invention recommends that the insulating layer, preferably made of a fluoropolymer, not exceed 30% of the core cable's diameter in thickness, in order to avoid a step-like effect at the electrode edges that could impair electrical contact with the tissues.

[0026] Finally, the means for decreasing rigidity (i.e., those providing decreasing rigidity from the proximal to the distal portion) provided by the invention facilitate the implantation of the microprobe by enabling it to be pushed into the vessels. As will be detailed later, the means for decreasing rigidity can be implemented, according to the invention, by a stepped stacking of nested tubes, or by a succession of tubes of the same diameter with increasing rigidity.

[0027] Once in place, the microprobe is stabilized by preforming, either in an S-shape or a three-dimensional spiral, which also ensures continuous electrical contact between the electrodes and the tissues. Advantageously, the microprobe also incorporates local reinforcement features.

[0028] In order to limit the heating of the core cable by skin effect during MRI imaging, the invention recommends that the strands include an outer layer of material with low magnetic susceptibility, less than 2,000.10 -12< .m 3< .mole -1< .

[0029] The low magnetic susceptibility material can be, at choice, tantalum (Ta), titanium (Ti), rhodium (Rh), molybdenum (Mo), tungsten (W), palladium (Pd), gold (Au) and their alloys.

[0030] We will now describe an example of implementation of the device of the invention, with reference to the attached drawings where the same numerical references designate identical or functionally similar elements from one figure to another. THE Figures 1a à 1d These are cross-sectional views of strands composed of a structural material and a radiopaque material. Figures 2a à 2f are cross-sectional views of core cables formed from strands shown on the Figures 1a à 1d . There Figure 3 is a cross-sectional view of a core cable made up of structural strands and radio-opaque strands. Figures 4a à 4d These are side views of microprobe preforms according to the invention. Figure 5 is a perspective view of a microcable showing an area completely stripped of its insulation layer. Figure 6 is a perspective view of a microcable showing a partially exposed area of ​​the insulation layer. Figures 7a et 7b These are cross-sectional views of microcables showing areas of partially exposed insulation layer. Figure 8 is a cross-sectional side view of a microprobe exhibiting a stack of stiffness gradient tubes. Figure 9 is a perspective view of a microprobe equipped with a local enhancement device. Figure 10a is a side view of a first embodiment of a microprobe according to the invention. Figure 10b is a cross-sectional view of the distal section of the microprobe of the Figure 10a . There Figure 10c is a cross-sectional view of a single strand of the microprobe core cable of the Figure 10b . There Figure 10d is a perspective view of the microprobe in Figure 10a equipped with an IS-1 connector. Figure 10e is a perspective view showing an implantation of the microprobe of the Figure 10a in the coronary veins. The Figure 11a is a cross-sectional view of a second embodiment of a microprobe according to the invention. Figure 11b is a cross-sectional view of a single strand of the microprobe core cable of the Figure 11a . THE Figures 11c et 11d are perspective views showing microprobe implantations of the Figure 11a in a cavity of the heart. Figure 12a is a cross-sectional view of a third embodiment of a microprobe according to the invention. Figure 12b is a cross-sectional view of a single strand of the microprobe core cable of the Figure 12a . There Figure 12c is a cross-sectional view of an example of microprobe implantation of the Figure 12a in brain tissue.

[0031] The probes concerned by the invention are microstimulation probes intended to be implanted in venous, arterial or lymphatic networks, and whose diameter does not exceed 2 French (0.66 mm). They consist in their active, distal part of a microcable formed of a conductive core cable partially surrounded by an insulating layer defining at least one stimulation electrode.

[0032] Lifespan is a fundamental parameter that must be taken into account in the design of any medical device, particularly the stimulation microprobes that are the subject of this invention. Indeed, heartbeats and organ movement induce bending deformations in this type of device, which must be perfectly controlled.

[0033] In general, for a cylindrical wire of diameter d, the bending deformation can be characterized by the ratio ε = d / D where D represents the diameter of the bend imposed on the wire by the bending stress. This stress, for example linked to the heartbeat, can be experienced by the strand over 400 x 10⁶ cycles over a period of 10 years, generating material fatigue that can lead to its breakage and limit its lifespan.

[0034] Thus, a microprobe for venous network stimulation, for example, may be subject to greater curvature deformations than a normal probe, insofar as it has to follow the deformations of the veins, which causes greater stress and makes its resistance to fatigue more restrictive.

[0035] To increase the fatigue strength of microwave probes, there is an advantage in adopting a multi-strand structure for the core cable, in the form of a strand made up of a plurality of small-diameter conductive strands. d. Reducing the diameter of the individual strands allows for a reduction in the stress applied to each strand, thus increasing the fatigue performance of the strand structure. For a given material, it is possible to define a maximum deformation. c Max corresponding to its fatigue resistance limit for a number of deformation cycles equal for example to 100.10 6< .

[0036] The choice of a material constituting the reinforcement of the core cable, which we will call the "structuring material", must meet several criteria.

[0037] In particular, it must be among the materials whose mechanical properties are known for long-term implantable applications and exhibit a maximum deformation ε Max greater than the deformation that a strand is likely to undergo, while remaining compatible with the technical feasibility and cost of a very small diameter strand.

[0038] As an example, for a cobalt alloy of type MP35N having a maximum strain ε Max of 5.10 -3 < to 100.10 6 < cycles and for a curvature diameter D For a 7 mm diameter, the diameter of the individual strand must be less than 35 µm. A 20 µm strand will therefore easily withstand this stress, while a 40 µm strand risks breaking before reaching 100 x 10⁶ cycles. Note that NiTi alloys exhibit a maximum strain ε Max higher, from 5 to 9.10 -3<, offering even wider possibilities.

[0039] In summary, the invention proposes using, as a structural material, stainless steel, a cobalt alloy from the MP35N series, a precious metal, titanium, or a NiTi alloy with high fatigue resistance, to form a multi-strand structure whose diameter d the strands do not exceed 40 µm, this dimension allowing on average to guarantee maximum fatigue breakage resistance under the extreme stress conditions to which such structures may be subjected.

[0040] Ideally, we will consider strands of diameter d between 20 and 40 µm, smaller dimensions may pose technical feasibility and cost problems.

[0041] In order to ensure sufficient X-ray visibility for microprobe implantation, it is necessary to introduce a minimum amount of radio-opaque material along the core cable.

[0042] The challenge in this regard is to reconcile the cable's fatigue resistance with radiopacity and corrosion resistance. Indeed, most materials used for their X-ray visibility—namely tantalum (Ta), tungsten (W), iridium (Ir), platinum (Pt), gold (Au), and their alloys—generally do not exhibit high fatigue resistance. Therefore, it is advantageous in such cases to adopt a composite cable structure in which a radiopaque material is added to the structural material within the strand of individual strands.

[0043] Given the sensitivity of current X-ray fluoroscopy equipment, the minimum presence of radio-opaque material in the composite structure is estimated at an area of ​​0.008 mm² in the core cable section, without the proportion of radio-opaque material exceeding 50%, in order not to degrade the mechanical properties of the strands ensured by the structural material.

[0044] As shown by Figures 1a à 1d The composite structure of the core cable is made up of composite strands consisting, at least, of a structural material 1 and a radiopaque material 2. More precisely, the Figure 1a represents a strand in which the structural material 1 is located on the outside of the strand and the radiopaque material 2 on the inside. Conversely, in the strand of the Figure 1b The structural material 1 is on the inside and the radiopaque material 2 is on the outside. The strand of the Figure 1c is made with an alloy of 3 structural material and radio-opaque material. Finally, the strand structure of the Figure 1d is more complex, with two outer and inner sections of radio-opaque material 2 surrounding an intermediate section of structural material 1.

[0045] The 10 strands thus obtained can be twisted together to form a core cable for the microprobe. On the Figure 2a is represented a strand 11 of nineteen unit strands 10. Strand 12 of the Figure 2b is formed by the assembly of seven groups of seven strands 10. The Figure 2c shows a strand 13 of seven groups of 19 strands assembled according to strand 11 of the Figure 2a Finally, even more complex structures are illustrated on the Figures 2d à 2f .

[0046] According to the variant of the Figure 3 The core cable 14 has a composite structure built not at the level of the strands but at the level of the cable itself. In the example given, strands 101 made of structural material surround strands 102 made of radio-opaque material.

[0047] Regarding the number of strands per bundle, it can be calculated that for a strand diameter of 40 µm and a radiopaque material content of 50% occupying a cross-section of 0.008 mm², the total number of strands, regardless of the material, is approximately fifteen. Conversely, for a strand diameter of 15 µm and a radiopaque material content of 15% occupying the same cross-section, the total number of strands reaches approximately 300.

[0048] Another important physical characteristic of a microprobe is its flexibility. This property allows the stimulation device to navigate tight curves and ensures the absence of trauma to the probe by preventing perforation of the veins through which it travels. To guarantee this atraumatic approach, the tip of the microprobe is rounded into a hemispherical shape to minimize the risk of perforation.

[0049] By comparing it with existing guide wires used in the same applications, the Applicant was able to establish that an external diameter of the core cable of no more than 0.50 mm provides a sufficient level of flexibility and compatibility with living tissues.

[0050] In general, the compatibility of implantable devices with modern medical imaging techniques, such as MRI, is fundamental to ensuring optimal patient treatment.

[0051] Indeed, due to its predominantly metallic structure, the microprobe presents a risk of overheating related to currents induced by the "skin effect" on the outside of the individual strands under the influence of the applied magnetic field. However, the small diameter of the strands is favorable to heat dissipation and reduces the heating effects caused by MRI. Furthermore, the thermal energy stored by the materials, already limited in volume, can be further reduced if the individual strands are coated with an outer layer of a material with low magnetic susceptibility (magnetic susceptibility being the ability of a material to become magnetized under the influence of an external magnetic field).

[0052] The most favorable materials in this application are those whose magnetic susceptibility is less than 2,000.10 -12< m 3< .mole -1< , notably tantalum (Ta), titanium (Ti), rhodium (Rh), molybdenum (Mo), tungsten (W), palladium (Pd), gold (Au) and their alloys.

[0053] Regarding the transmission of electrical current to tissues, the concept adopted by the invention is to avoid using added electrodes, but, as the Figure 5 The core conductor cable 11 is used to form the electrodes by partially surrounding the cable with a polymer insulating layer 20. An electrode 30 is thus formed by a stripped section of cable. This coating technique provides the electrode 30 with sufficient contact to ensure electrical stimulation of the tissues.

[0054] The insulation layer 20 covers the entire conductive structure of the core cable 11, except at the electrode areas distributed along the microcable thus produced.

[0055] Preferably, the thickness of the insulation layer 20 does not exceed 30% of the outside diameter of the core cable 11, to avoid the stair effect at the edge of the electrode, as the insulation may prevent contact between the electrode and the fabric.

[0056] The required characteristics for the 20 insulation layer are as follows: fatigue resistance, electrical insulation, long-term biocompatibility, biostability, transformation capability and implementation compatible with the core cable conductor.

[0057] Examples of materials that can be used in this context include: polyurethanes (PU), polyesters (PET), polyamides (PA), polycarbonates (PC), polyimides, fluorinated polymers, polyether-ether-ketone (PEEK), poly-p-xylylene (parylene), polymethyl methacrylate (PMM).

[0058] However, preference will be given to materials with high chemical inertness, such as fluoropolymers, which also offer very good insulation. Examples of these compounds include: PTFE (polytetrafluoroethylene), FEP (perfluoropropylene), PFA (perfluoroalkoxy copolymer resin), THV (tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride), PVDF (polyvinylidene fluoride), EFEP (ethylene propylene ethylene fluoride), ETFE (ethylene tetrafluoroethylene).

[0059] The methods for creating the insulation layer on the core cable vary depending on the materials used: co-extrusion on the conductor, for PU, PA, PEEK, polyimides and fluorinated polymers; deposition by dipping in a solution, for PU, PA and polyimides; heating of a heat-shrinkable tube, for PET and fluorinated polymers; chemical deposition by gas, for parylene; plasma treatments to improve adhesion between layers.

[0060] During the implementation of these processes, electrode zones can be defined by depositing separate insulating layers, or by partially stripping an insulating layer deposited over the entire cable. This stripping is performed, for example, by laser ablation. As indicated by the Figures 6 et 7a, 7b This technique allows for partial openings. In particular, the Figures 7a et 7b show a microcable with respectively two bare areas 30 1 , 30 2 , and five bare areas 30 1 , 30 2 , 30 3 , 30 4 , 30 5 .

[0061] Advantageously, the electrode areas distributed along the microcable have a cumulative surface area not exceeding 20 mm², for example in the form of 40 electrodes of 0.5 mm² or 20 electrodes of 1 mm², this surface area depending on the application as well as the electrical performance of the associated equipment.

[0062] Ideally, in order to limit current consumption, it is preferable to make electrodes with a surface area of ​​no more than 0.5 mm², thereby increasing the local current density.

[0063] If necessary, the microcable can incorporate corrosion resistance reinforcement at the electrodes, achieved by adding a dedicated, high-resistance coating. Corrosion resistance can also result from choosing a structure where the noble metal of the radiopaque material forms an outer layer sheathing a core of structural material.

[0064] A first technology used in this sense consists of a submicron deposition (less than 1 µm) by chemical or electrochemical means of a noble material, of the type of those mentioned above as radio-opaque materials.

[0065] Another technique involves creating a DFT-type composite tube ( Drawn Filled Tube ), with an additional layer of 1 to 2 µm of noble metal.

[0066] Another method involves creating a carbon deposit of the type Carbofilm (registered trademark) enabling corrosion protection and good performance in terms of hemocompatibility and biocompatibility.

[0067] If necessary, the outer surface of the insulating layer near the electrodes can contain a steroid-type anti-inflammatory. In this case, a very thin layer of steroid is deposited at the end of the manufacturing process by a chemical grafting process or by polymer crosslinking, for example a biodegradable polymer such as PLAGA (polylactic co-glycolic acid) or PLA (polylactic acid).

[0068] It is also possible to consider that the anti-inflammatory product is contained in the material constituting the isolation layer.

[0069] Finally, the microprobe is terminated at its proximal end by a connector designed to be connected to the generator of the implantable device.

[0070] According to the invention, due to the small size of the microprobe, it is envisaged to preform it at the level of the electrodes in order to promote electrical contact with the tissues, and also in order to mechanically stabilize the microprobe in the vessels.

[0071] The preforms can be obtained by forming the metallic or polymer part of the probe, for example by heat treatment.

[0072] THE Figures 4a à 4d illustrate some particular embodiments of the preform: the preforms of Figures 4a et 4b have a planar S-shaped configuration, simple or multiple, while the preforms of Figures 4c et 4d are configured in a three-dimensional spiral, single or double.

[0073] According to another aspect of the invention, a determining characteristic of a microprobe is that it can be easily manipulated by the physician during implantation.

[0074] It is also important to minimize stiffness transitions along the probe to reduce stress concentrations that could lead to fatigue embrittlement of the device. Nevertheless, some stiffening is necessary because an excessively flexible microprobe would limit manipulation during thrusting.

[0075] The solution to these difficulties lies in a graduated stiffening system, made possible by means of graduated stiffness between the proximal and distal parts of the microprobe. It is then possible to manage the progressive stiffness gradient along the probe in such a way as to guarantee, on the one hand, a flexible, non-traumatic distal section allowing passage through tortuosity and, on the other hand, a more rigid proximal section enabling the transmission of the force exerted by the physician using appropriate devices.

[0076] In the example provided to the Figure 8 The means of reducing stiffness are achieved by a stepped stacking of three tubes 51, 52, 53 nested one inside the other on the microcable 40. These tubes, made of PET (polyethylene terephthalate) for example, can have a thickness of 5 to 20 µm.

[0077] Thus, the rigidity at the proximal end of the probe can be fifty times greater than the rigidity at the distal end, without requiring the addition of any extra mechanical parts. The overall robustness is also significantly increased.

[0078] One can also consider methods of decreasing stiffness achieved by a succession of tubes of the same diameter with decreasing stiffness, welded together. However, this technique creates a risk of breakage at the welds between the tubes.

[0079] Finally, the Figure 9 This illustrates another variant consisting of a local reinforcement of the microprobe by a series of tubes 70 to, independently of the insulation, reinforce a preform or angulation necessary for the desired function, giving the microprobe a specific shape. The end 41 of the microprobe can also be thermoformed using this type of approach.

[0080] This solid, seamless structure offers the significant advantage of being easier to sterilize compared to conventional probes. This reduces the risk of damage to the microprobe materials due to overly aggressive sterilization processes.

[0081] We will now describe specific examples of the realization of a microprobe according to the invention, intended to be implanted in different sites of the body. Exemple 1

[0082] THE Figures 10a à 10e illustrate an example of the realization of a microprobe according to the invention, intended to be implanted in a vein of the coronary sinus.

[0083] The microprobe shown at the Figure 10a includes a 40 microcable, a cross-sectional view of which is shown on the Figure 10b The core cable 12 of the microcable 40 is formed of composite unit strands 10, as can be seen on the Figure 10c The structure consists of a core made of a structural metal 1, here an MP35N alloy with a diameter of 33 µm, and an outer shell 5 µm thick made of Pt / Ir 90 / 10 as a radio-opaque material 2. The ratio between the materials is 75% for the core and 25% for the outer shell. This simple structure offers good fatigue strength and corrosion resistance guaranteed by the platinum.

[0084] A cable 12 with a 49-strand core is required to obtain an apparent platinum surface of 0.011 mm², sufficient to ensure good visibility under X-ray fluoroscopy. The core conductor cable 12 then has a diameter of 0.30 mm, which gives it sufficient flexibility for intravascular use, via the coronary sinus for example.

[0085] The cable 12 is covered with a layer 20 of ETFE type insulation 25 µm thick allowing good insulation, compatible with an in-line extrusion process, for a final external diameter of 0.35 mm in the distal part 103 of the microprobe.

[0086] Openings 30 forming electrodes are made by laser ablation in the distal part 103 over an area of ​​0.5 mm², allowing to reduce current consumption to a minimum.

[0087] Heat-shrinkable PET tubes 51 and 52 are respectively placed in an intermediate zone 102 and in the proximal part 101, at 25 cm and 45 cm from the distal tip 41 of the probe, the total useful length of which varies between 90 and 120 cm.

[0088] The complete structure of the microprobe is given in the Figure 10d , on which we can see that the proximal part 101 ends with a transition zone 100 formed by a polyurethane tube 50 connected to an IS-1 type connector 200 whose end is equipped with a terminal 201 for electrical connection to the generator of the implantable equipment.

[0089] One method for inserting such a probe, shown in Figure 10e, consists of placing the intermediate part 102 in the coronary sinus and the distal part 103 with multiple electrodes 30 in the veins of the coronary network, thus stimulating the left ventricle (LV). This operation is performed using a placement catheter 300 which can be removed by cutting with a cutting tool ( stitter ), as with the placement of conventional probes. Exemple 2

[0090] A second example of the realization of a microprobe intended to be implanted in a cardiac chamber, for example a right heart chamber, is illustrated on the Figures 11a à 11d .

[0091] This microprobe includes a 40-meter microcable, a cross-section of which is shown on the Figure 11a The core cable 11 of the microcable 40 is formed of composite unit strands 10, as can be seen on the Figure 11b The structure consists of a tantalum 2 core as a radiopaque material and an outer shell 2 of a structural material, in this case nitinol. The ratio between the materials is 25% core and 75% outer shell. This simple structure provides external elasticity as well as good radiopacity ensured by the inner core.

[0092] It is worth recalling the advantage of nitinol in having significant shape memory, particularly favorable for contact in a large cavity.

[0093] A heart cable 11 of nineteen strands is required to obtain an apparent platinum surface of 0.010 mm², sufficient to ensure good visibility under X-ray fluoroscopy. The conductive heart cable 11 then has a diameter of 0.20 mm, which gives it sufficient flexibility for intracavitary use, particularly in the ventricle and / or right atrium.

[0094] The cable 11 is covered with a layer 20 of FEP type insulation 25 µm thick allowing good insulation and compatible with an in-line extrusion process, for a final external diameter of 0.25 mm in the distal part of the microprobe.

[0095] In this example, it is possible to use a very thin polyimide or PEEK reinforcement structure that preserves the superelastic properties of nitinol. In this case, a coating ( coating ) of type Carbofilm (Registered trademark) exhibiting superior corrosion resistance and increased biocompatibility. This type of coating, less than 1 µm thick, does not alter the electrical properties of the electrode while significantly improving its surface compatibility with blood.

[0096] Furthermore, through appropriate processing, it is possible to configure the probe to conform to the cardiac cavity according to the associated stimulation and anatomical requirements. Figures 11c et 11d show two possible probe conformations for stimulation of the right cavities. Exemple 3

[0097] A third example of the realization of a microprobe intended to be implanted in the cerebral cavities is illustrated on the Figures 12a à 12c .

[0098] In this example, very good radiopacity is required, as well as high flexibility and a very small diameter. Furthermore, for this type of product, MRI compatibility is essential.

[0099] The 40 microcable shown on the Figure 12a includes a core cable 13 formed from composite unit strands 10 made up, as can be seen on the Figure 12b The three-layer wire comprises (i) a core 2 of a radiopaque material, in this case tantalum, (ii) an intermediate layer 1 of titanium as a structural material, and (iii) an outer sheath 3 of palladium to minimize skin effects and achieve better structural compatibility with MRI. The ratio between the three materials is 30% Ta / 65% Ti / 5% Pd. This structure, although less fatigue-resistant at the strand 10, is compensated for by a unit diameter of 16 µm, which is subject to less mechanical stress.

[0100] A core cable 13 of 133 strands (7x19) is required to obtain an apparent platinum surface of 0.010 mm², sufficient to ensure good visibility under X-ray fluoroscopy. The conductive core cable 13 then has a diameter of 0.25 mm, very flexible for intracerebral use.

[0101] The cable 13 is covered with a layer 20 of FEP type insulation, mechanically more flexible, 25 µm thick allowing good insulation and compatible with an in-line extrusion process, for a final external diameter of 0.30 mm in the distal part of the microprobe.

[0102] A polyether block amide Pebax (trademark) can be associated with the isolation layer 20 to manage stiffness gradients towards the proximal part of the microprobe.

[0103] An example of the implantation of this probe is shown on the Figure 12c .

Claims

1. Detection / stimulation probe intended for implantation in venous, arterial or lymphatic networks, comprising a microcable (40) with a diameter of at most 2 French (0.66mm), said microcable (40) comprising: - an electrically conductive core cable (11, 12, 13, 14) with a diameter of at most 0.50mm, formed by a strand comprising a plurality of wires (10) with a unit diameter (d) of at most 40µm, said core cable comprising a structuring material (l) having a high fatigue resistance; and - an insulating layer (20) made of polymer, partially surrounding the core cable to a thickness of at most 30% of the core cable's diameter, wherein: - said probe is a microprobe comprising, in its active, distal part, the said microcable (40) with a diameter of at most 2 French (0.66mm); - said structuring material (1) of the core cable comprises stainless steel, a cobalt alloy, a precious metal, titanium or a NiTi alloy; - the radiopaque material (2) is a material selected from the group consisting of: tantalum (Ta), tungsten (W), iridium (Ir), platinum (Pt), gold (Au) and their alloys; - means for reducing stiffness (51, 52, 53) are provided along the length of the microprobe between its proximal end and its distal end, characterised in that: - the core cable (11, 12, 13, 14) of the microcable has a composite structure comprising, at least, said structuring material (1) and a radiopaque material (2) constituting at least approximately 0.008mm2 of the section of the core cable, in a proportion not exceeding 50%; - at least one exposed area (30) is formed in the insulating layer (20) so as to form at least one electrode on a total cumulative surface area of no more than 20mm2; - the microprobe is shaped at the electrodes (30) in accordance with at least one preform (61, 62, 63, 64) for electrical contact and mechanical stabilisation; and - the microprobe comprises local reinforcement means, including a series of tubes (70), to reinforce the preform of the microcable (40), independently of the insulation.

2. Microprobe of claim 1, wherein the composite structure of the core cable (11, 12, 13) is formed by composite wires (10) comprising, at least, a structuring material (1) and a radiopaque material (2).

3. Microprobe of to claim 2, wherein: - the structuring material (l) is on the outside and the radiopaque material (2) is on the inside of the wire (10), or - the structuring material (l) is on the inside and the radiopaque material (2) is on the outside of the wire (10), or - an outer section and an inner section of radiopaque material (2) surround an intermediate section of structuring material (1).

4. Microprobe of claim 1, wherein the composite structure of the core cable (14) is formed by wires (101) made of structuring material (1) and wires (102) made of radiopaque material (2).

5. Microprobe of claim 1, wherein the unit diameter (d) of the wires (10) is between 20 and 40µm.

6. Microprobe of claim 1, wherein the said plurality of wires of the strand comprises between 15 and 300 wires.

7. Microprobe of claim 1, wherein the polymer forming the insulating layer (20) is a fluorinated polymer.

8. Microprobe of claim 1, wherein the strands (10) comprise an outer layer of material (3) having a low magnetic susceptibility of less than 2000.10-2 m3.mol-1.

9. Microprobe of claim 8, wherein the material (3) having a low magnetic susceptibility is a material selected from the group consisting of: tantalum (Ta), titanium (Ti), rhodium (Rh), molybdenum (Mo), tungsten (W), palladium (Pd), gold (Au) and alloys thereof.

10. Microprobe of claim 1, wherein the surface area of an electrode (30) is at most 0.5mm2.

11. Microprobe of claim 1, wherein the microcable (40) comprises a corrosion-resistant coating at the electrodes (30).

12. Microprobe of claim 1, wherein the outer surface of the insulating layer (20) near the electrodes (30) contains an anti-inflammatory agent.

13. Microprobe of claim 1, wherein the material constituting the insulating layer (20) contains an anti-inflammatory agent.

14. Microprobe of claim 1, wherein the preform is: - a flat S-shaped preform (61, 62), or - a three-dimensional spiral preform (63, 64).

15. Microprobe of claim 1, wherein: - the means for reducing stiffness are provided by a stepped stack of tubes (51, 52, 53) nested one inside the other, or - the means for reducing stiffness are provided by a series of tubes of the same diameter, with decreasing stiffness.