A LOCATING DEVICE WITH POLYIMIDE FILLED JOINTS IN THE TIP SECTION

Abstract: A locating device (2) comprising a tip section (4) provided at a distal end of a wire means (6) and a regulation unit (8) provided at a proximal end of said wire means. The locating device is adapted to be inserted into an interior channel within an elongated flexible component, such as a hollow electrode cable, to stiffen the flexible component and bend a distal end section thereof, preferably into a J-shape. The tip section (4) includes a bendable insulating polymer element (20) containing a number of bending actuators (22) connected in series. Each bending actuator comprises silicon plate sections (24) interconnected by polyimide filled V-groove joints (26) provided with heating means (34) allowing the binding angles of said V-groove joints to be controlled by thermal expansion of the polyimide filling (28) thereof by heating this filling (28).

Description: A LOCATING DEVICE WITH POLYIMIDE FILLED JOINTS IN THE TIP SECTION Description Field of invention The present invention relates to an electrically controlled locating device comprising a tip section provided at a distal end of a wire means and a regulation unit provided at a proximal end of said wire means, the device being adapted to be inserted into an interior channel within an elongated flexible component to stiffen such component and bend a distal end section thereof into a required shape. An elongated flexible component of the aforementioned kind may e.g. be a hollow electrode cable used for stimulation in the human body, e.g. an electrode cable or pacing lead for a heart stimulator. Such electrode cable may be devised to serve either as an implant or for removal from the human body after a medical treatment has been performed. The prior art A standard type of a locating device generally in use today is a stylet unit (or man- drin) used for stiffening and guiding an electrode cable (pacing lead) for a heart stimulator or pacemaker during insertion, advancing and positioning of such cable or lead into a human heart, and when the contact electrode at or near the distal tip end of the cable is to be anchored in a cavity of the heart. Such temporarily introduced stylet unit inside the electrode cable or pacing lead extends through the cable's interior channel from the proximal end of the cable to the distal end thereof where the contact electrode is mounted. This kind of stylet unit normally comprises a flexible, tubular stylet shell containing a stylet wire longitudinally movable within the shell's interior channel. To prevent the stylet wire from rotating in relation to its surrounding tubular stylet shell (sleeve) it is preferred to use a shell (sleeve) with an interior channel having a non-circular cross-section in combination with a stylet wire having a corresponding non-circular cross-section. In EP 0 773 037 A2 there is described a guide wire unit where the stylet wire is prevented from rotating in its surrounding shell (sleeve) by means of interacting non-circular cross-sections. When a pacing lead contact electrode is to be positioned and anchored in the heart's atrium using a stylet unit it is required that an appropriate J-shape be imparted to the distal end or tip section of the pacing lead, by means of the stylet unit. A suitable J- shape will highly facilitate the insertion of the distal end section of the pacing lead into the atrial auricle as well as the anchoring of the contact electrode in the trabeculae of the atrial auricle. After the pacing lead contact electrode has become duly positioned and anchored at the desired site in the heart, the stylet unit is withdrawn completely from the interior channel of the pacing lead and thereby from the heart. The above kind of stylet unit is relatively difficult to manufacture and furthermore is dependent on free longitudinal movement between the two parts and it would be desirable with locating devices not dependent on relative longitudinal movement between different parts. US Patent No 4,758,222 discloses a device comprising an electrically controlled catheter. The catheter incorporates parts made of memory metal that will change from one state to another when subjected to heating. The memory metal parts are heated by means of electrical current supplied from a power unit via longitudinal conducting means. When the memory metal parts are heated, the catheter will be deflected. US Patent No 5,211,183 discoses a guidewire for access to a body structure or location by inserting it into into the body and advancing it to the desired location. The guide wire includes shape memeory means that may be heated by means of induction heating, immersion heating, application of RF energy or by body heating, the guide wire thus being deflected when heated. Neither of the two above devices is designed for use in an internal lumen in for instance an endocardial pacing electrode lead or the like. Both also are limited to discrete changes in shape in view of the nature of shape-memory materials. Summary of the invention A primary object of the present invention is to provide a novel locating device which may be used for bending at least a portion or section of a tubular elongated flexible component without utilising any longitudinal movement between interacting mutually displaceable elements by providing an electrically controlled locating device having a tip section which can be bent into a J-shaped configuration. The locating device further should be easy and cheap to manufacture and it should be possible to manufacture very thin locating devices. According to the invention said objects when designing a locating device may be attained by utilizing the principles for thermally expansive joints for microactuators as described in 1) Ebefors et al, "New small radius joints based on thermal shrinkage of polyimides in V-grooves for robust self-assembly 3D microstructures", J. Micromech. - Microeng. 8 (1998) 188-194, IOP Publishing Ltd 1998, and 2) Ebefors et al "Dynamic actuation of polyimide V-groove joints by electrical heating", Sensors and Actuators A 67 (1998) 199-204, Elsevier Science S.A. 1998, both articles hereby being incorporated by reference. Said device thus has the features set forth in the enclosed claim 1. In such locating device the tip section thus includes a bendable insulating polymer element containing a sequence of bending actuators. In this sequence the bending actuators are connected after each other, i.e. in series. Each bending actuator comprises silicon plate sections interconnected by polyimide filled V-groove joints which are provided with heating means allowing the bending angles of the V-groove joints to be controlled by thermal expansion of the cured polyimide fillings of the V- grooves. As indicated in the above articles a useful polyimide is Selectilux® HTR- 3200 from OCG. The dynamic and reversible thermal expansion of the cured polyimide fillings is preferably done by electricity, more precisely by regulating an electric current supplied to the heating means which may be resistive heaters integrated with the polyimide fillings. A temperature increase in the joints will result in an expansion of the polyimide and thereby a dynamic change of the bending angles of the V-groove joints. If the V-grooves are defined by metal foil wall portions, for instance made of aluminium, these wall portions may constitute the resistive heaters used for producing the local heat dissipation in the joints. A dynamic bending angle of at least say 3°- 4° per V-groove is certainly possible with this type of design. Consequently, a series of say 45-60 bending actuators will be sufficient for obtaining an accumulated 180° bending angle corresponding to a desirable U- or J-shaped total bending angle. The individual bending actuator may comprise two or more silicon plate sections interconnected by polyimide filled V-groove joints. The V-groove defining surfaces of the V-groove joints may be lined with layers of electrically conductive material, e.g. aluminium, constituting integrated heating means in the form of resistors on the wall surfaces of the V-grooves. Furthermore, according to the present invention the wire means may comprise a flexible, tubular stylet shell and a single lead wire inside the longitudinal interior channel of the shell. The regulation unit (at the proximal end of said wire means) preferably comprises a manipulator housing containing a power source (e.g. an electric battery) connected to the wire means. The regulation unit may be provided with an adjustable potentiometer for controlling the intensity of the current supplied to the heating means. As indicated in the above articles, the wire means will be easy to manufacture by bulk micromachining metods for silicon substrates which after the completed manufacturing process easily can be cut into long strips. It is thus also possible to manufacture very thin wire means. Since the deflection is dependent on heat expansion instead on shape memory, the deflection will be continuous. Description of the drawings The invention will now be further elucidated referring to the attached drawings which schematically and not to scale depict an embodiment of a locating device and the bendable tip section thereof, according to the present invention. On the drawings: Fig. 1 very schematically shows a locating device; Fig. 1A shows (on a larger scale) a cross section of the wire means, at line A-A in Fig. 1; Fig. 2 shows the bendable tip section of the locating device, in a straight not yet bent state; Fig. 3 shows the bendable tip section in a bent state; Fig. 4 shows, in longitudinal section, very schematically and on a distorted scale, the fundamental construction of a bendable tip section containing a plurality of interconnected bending actuators. Description of preferred embodiments In Fig. 1 there is shown in side elevation an elongated locating device 2 adapted to be used e.g. for stiffening and guiding a tubular bendable pacing lead (not shown), which is connected to a heart stimulator (not shown), when such pacing lead is to be inserted, advanced and positioned in a human body so that a tip electrode at the distal end of the lead becomes suitably positioned and can be anchored in a cavity of the heart. The elongated locating device 2 comprises a bendable tip section 4 arranged at the distal end of a tubular wire means 6 being provided at its proximal end with a handle-like regulation unit 8. The unit 8 comprises a manipulator housing 10 containing an electric battery 12 and being provided at the forward end thereof with an adjustable potentiometer 14 used for controlling the electric current supply from the battery 12 via the wire means 6 to electric heating means within the bendable tip section 4. In the present case the wire means 6 preferably comprises a relatively stiff, thin metal tube 16 containing in its interior channel an insulated single-core line wire 18 (see enlarged cross-section of Fig. 1 A). The tube 16, which preferably can be made of stainless steel, itself will constitute the first pole, and the line wire 18 the second pole, of the bipolar wire means 6. The outer diameter of the tube 16 may be e.g. 0,4 mm, and the inner diameter thereof may be about 0,3 mm. A preferred type and structure of the bendable tip section 4 of the locating device 2 will now be described more in detail and with reference to Figs. 2-4. The bendable tip section 4 comprises a bendable insulating casing 20 made of a suitable polymer. This outer polymer casing 20 contains a plurality of bending actuators 22 being connected in series to be able to provide, together, a reversible, accumulated 180° bending angle corresponding to a contemplated U- or J-shape. Each bending actuator comprises two silicon plates or beam sections 24 interconnected by an intermediate polyimide filled V-groove joint 26. The polyimide filling in each such joint is constituted by a cured polyimide body 28 positioned in a support channel (defining the V-groove) consisting of a bottom portion 30 and a pair of opposite flanks 32a, 32b being integral parts of a cross corrugated metal foil strip 34. The V- groove angle between the flanks 32a, 32b constitutes a dynamic and reversible "bending angle" the magnitude of which can be changed by controlling the thermal expansion of the cured polyimide body 28. In this case the metal foil strip 34 is used as a resistive heater producing local heat dissipation (temperature increase) in the polyimide body of the joint 26. A temperature increase in the polyimide body 28 will result in an expansion of the polyimide, thereby providing a dynamic change of the bending angle. Large bending angles can be obtained by connecting a plurality of V-groove joints 26 in series. The under side (as seen in the drawing) of the bendable tip section is provided with a second conducting layer 34' separated from the bendable tip by means of an insulating layer. This conducting layer is connected to the metal tube 16. Instead of using the metal foil strip 34 as a resistive heater for controlling the expansion of the polyimide bodies 28, it is possible to use some other type of heating means, e.g. an electric heating means fully integrated (embedded or contained) in the polyimide bodies 28. Irrespective of the type of heating means used for control- ling the bending angles of the series of interconnected V-groove joints 26 it is only required to have such heating means connected to a pair of electric wires (or pole means) for supplying the current necessary to produce the local heat dissipation in the joints. In the description above, the metal tube 16 has been illustrated as being the second conductor in the above device. It should however be noted that this part of the stylet unit could be designed at will as long as there are two conducting paths for the electrical current to be supplied to the bendable tip. The initial shape of the wire can be determined by means of the curing of the polyimide since the polyimide shrinks when cured.

Claims: Claims 1. An electrically controlled locating device (2) comprising a tip section (4) provided at a distal end of a wire means (6) and a regulation unit (8) provided at a proximal end of said wire means, the device being adapted to be inserted into an in- terior channel within an elongated flexible component, such as a hollow electrode cable, to stiffen the flexible component and bend a distal end section thereof, preferably into a J-shape, characterized in that the tip section (4) includes a bendable insulating polymer element (20) containing a sequence of bending actuators (22), each bending actuator comprising silicon sections (24) interconnected by polyimide filled V-groove joints (26) provided with heating means (34) allowing the bending angles of said V-groove joints to be controlled by thermal expansion of the polyimide filling (28) thereof. 2. A locating device according to claim 1, characterized in that each bending actuator (22) comprises at least three silicon sections (24) interconnected by two polyimide filled V-groove joints (26). 3. A locating device according to claim 1 or 2, characterized in that the total attainable, accumulated bending angle of all V-groove joints (26) within the tip section (4) amounts to about 180° thereby providing a J-shaped configuration for the tip section. 4. A locating device according to any of the claims 1-3, characterized in that the heating means comprises electric heating means being integrated in the V-groove joints (26). 5. A locating device according to any of the claims 1-3, characterized in that the V-groove surfaces of the V-groove joints (26) are lined with layers (32a,32b) of electrically conductive material, e.g. aluminum, which may constitute an integrated heating means in the form of resistors in the V-grooves. 6. A locating device according to claim 5, characterized in that the integrated heating means are connected to a pair of electrical wires adapted for supplying current for producing local power dissipation in the joints. 7. A locating device according to any preceding claim, characterized in that the wire means (6) comprises a flexible, tubular stylet shell (16) and a single lead wire (18) inside the longitudinal channel of the shell, and that the regulation unit (8) comprise a manipulator housing (10) containing a source of power, e.g. an electric battery (12), connected to the wire means, and a potentiometer (14) for controlling the power supply to the heating means.

Inventors: HILL ROLF, HILL, ROLF
Applicants: HILL ROLF, ST JUDE MEDICAL, HILL, ROLF, ST. JUDE MEDICAL AB
Application year: 2001
Main classification: A61M25
IPC codes: A61M25, A61N1