US20120022356A1

US20120022356A1 - implantable mri compatible medical lead with a rotatable control member

Info

Publication number: US20120022356A1
Application number: US13/262,179
Authority: US
Inventors: Linn Olsen; Mikael Forslund; Henrik Djurling; Patrik Forsström; Leda Henriquez; Kenneth Dahlberg; Olof Stegfeldt; Åke Sivard
Original assignee: St Jude Medical AB
Current assignee: St Jude Medical AB
Priority date: 2009-03-31
Filing date: 2009-10-30
Publication date: 2012-01-26
Also published as: US20120035693A1; EP2414034A4; WO2010112245A1; EP2414034B1; US8521307B2; WO2010114433A9; WO2010114432A1; EP2414033A4; EP2414034A1; WO2010114433A1; EP2414033B1; EP2414033A1; WO2010114429A1

Abstract

A medical implantable lead is adapted to be implanted into a human or animal body for monitoring and/or controlling of an organ inside the body. The lead has in a distal end, a combined fixation means and electrode member in form of a helix, which is connected to a rotatable tubular member being connected to a rotatable member at a proximal end of the lead, and which is rotatable in relation to the lead and extendable out from the distal end, by rotation of the control member and the tubular torque transferring member, to be able to fixate the distal end of the lead to the organ by being screwed into the tissue. The helix is electrically connected to a connector at the proximal end by means of at least one electrically conducting wire formed as an electrically conducting coil, which is separate from the tubular torque transferring member and unrotatable in relation to the lead and that has one or more individual wires, each including an electrically conducting wire core and a surrounding electrically insulating layer, wherein the rotatable control member is rotatable within the connector.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a medical implantable lead of the kind being adapted to be implanted into a human or animal body for monitoring and/or controlling of an organ inside the body, comprising at a distal end a combined fixation means and electrode member in form of a helix, which is connected to a rotatable tubular torque transferring member being in its turn connected to a rotatable control member at a proximal end of the lead, and which is rotatable in relation to the lead and extendable out from the distal end, by rotation of the control member and the tubular torque transferring member, to be able to fixate the distal end of the lead to the organ by being screwed into the tissue, wherein the helix is electrically connected to a connector at the proximal end by means of at least one electrically conducting wire.
2. Description of the Prior Art
It is well known in the art to use a medical implantable lead of the above kind to monitor and/or control the function of an organ inside a human or animal body, for example to monitor and/or control a heart by means of a monitoring and/or controlling device in form of a pacemaker or cardiac defibrillator connected to the proximal end of the lead. The medical implantable lead is provided with at least one electrical conductor, in form of a coil having one or more helically formed electrically conducting wires, sometimes also referred to as filars, which connects one or more connectors arranged at the proximal end of the lead with one or more electrodes in its distal end. At least one of the electrodes is formed as a helix, which is adapted to be screwed into the tissue of the organ for receiving and/or transmitting electrical signals from and/or to the organ and transmit them, through the electrically conducting coil, to the monitoring and/or controlling device connected to the proximal end of the lead. The helix also functions as an attachment means for attaching the distal end of the lead to the organ by being rotatably extended out from the distal end of the lead and accordingly screwed into the tissue of the organ. To accomplish the rotation of the helix, it is mechanically connected to the innermost one of the electrically conducting coils, which accordingly has to be rotatable in relation to the lead as well as be sufficiently rigid to be able to transmit the required torque from the proximal to the distal end. The lead may also be provided with one or more additional electrodes separate from the helix and e.g. be formed as a contact electrode, abutting against a surface of the organ, or be formed as a so called indifferent electrode which is surrounded by body fluids such as blood.
Normally, such medical implantable leads are not considered to be compatible with Magnetic Resonance Imaging (MRI), i.e. persons or animals having such a lead implanted into the body, are excluded from being examined by MRI-scanning. This is due to the fact that the electromagnetic field, that is generated during the MRI-scanning, will induce a current in the conductor, which connects the one or more electrodes at the distal end of the medical implantable lead with the monitoring and/or controlling device at the proximal end of the lead. This induced current may cause heating at an electrode being in contact with the tissue of the organ, especially if the electrode is in form of a helix which is penetrated into and embedded within the tissue. If the heating is too high, there is a risk that this will cause damages to the tissue. However, the use of MRI-scanning for diagnostics is growing extensively and an increasing number of the population having a lead implanted would benefit from MRI-scans. It is thus desirable to reduce any heating at or close to the lead tip to acceptable and safe levels to allow MRI-scanning also of persons or animals having such a lead implanted.
It is known in the art to provide such medical implantable leads with an electrical shielding, in form of a tube of braided wires, which surrounds the coil and which in its proximal end normally is connected to the casing of the monitoring and/or controlling device. However, such shielded medical implantable leads are associated with several disadvantages. On the one hand, the braided shielding will give the medical implantable lead an increased thickness as well as increased rigidity, which normally is not desirable. On the other hand, it has appeared that such a braided shielding cannot prevent the induction of electrical current to the coiled conductor in a degree that is sufficient to, without risk, expose an individual, having an implanted lead, to a MRI-scanning.
U.S. Pat. No. 7,363,090 discloses a way to reduce heating caused by induced current from MRI-scanning by connecting a contact electrode and an indifferent ring electrode in series with a band stop filter, which are tuned to certain frequencies utilized during MRI-scanning. Such a prior art medical implantable lead comprises passive electronic components, which contribute to making the lead more complex and thus more costly to manufacture.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a medical implantable lead, which in a simple and cost-effective way reduces the induction of current from an electromagnetic field into the electrically conducting coil.
The basis of the invention is the insight that the above object may be achieved by separating the function of effecting rotation and extending the helix out from the distal end of the lead, from the function of transmitting the electrical signals between the helix and, where appropriate, the one or more further electrodes at the distal end and the one or more connectors at the proximal end, i.e. to split these functions on separate members within the lead. More precisely, the function of transmitting a torque from the proximal end to the distal end for effecting rotation of and extending the helix out from the distal end, is effected by an inner tubular torque transferring member, which has no electrically conducting function to or from the electrode, whereas the electrically conducting function to and from the electrode is effected by a separate electrically conducting coil formed of one or more helical wires. Each wire is moreover coated with an electrically insulating layer, such that the coil will form an inductor, which will allow the low frequency signals between the electrode and the monitoring and/or controlling device to pass through without being exposed to high impedance. On the other hand, for induced current from high frequency electromagnetic fields, such as fields from MRI-scanning typically operating at 64 or 128 MHz, the impedance in the electrically conducting coil will be very high which to a large extent will restrain induced high frequency currents.
According to the invention, also at the proximal end of the lead, the function of performing rotation of the torque transferring member, and consequently the helix, is separated from the function of conducting an electrical current between a connector at the proximal end via the electrically conducting coil and the helix. More precisely, the rotation of the torque transferring member is effected by rotation of a control member at the proximal end, which control member is connected to the torque transferring member and rotatably arranged coaxially within a connector. The connector is in turn electrically connected to the electrically conducting coil, which is rotatably fixed in relation to the lead. In case the torque transferring member and/or the control member is electrically conductive, the connector and the control member are electrically insulated from each other to prevent induced current from a magnetic field into the torque transferring member and/or the control member to be transmitted to the connector and the electrically conducting coil, as well as the helix. In other words, the lead is arranged such that the electrical connection between the helix and the conducting wire is maintained regardless of the rotational position of the helix, while no electrical connection is present between the helix and the tubular torque transferring member even though the helix is rotatable by means of the tubular torque transferring member, and the rotatable control member is rotatable within the connector.
By forming the medical implantable lead in this way, it is possible to form the tubular torque transferring member with a sufficient mechanical strength and stiffness to be able to transfer the torque required, from the proximal end to the distal end, to rotate the helix for extending it out from the distal end of the lead and screw it into the tissue. The electrically conducting coil, on the other hand, can be optimized to present an as high inductance as possible. For example, since the electrically conducting coil does not have to transfer any torque to the helix, it can be formed of one or only a few wires, which each can be made very thin. In this way, the pitch of the individual wires of the coil will be very low, which will increase the inductance of the coil. Also, since the electrically conducting coil will be positioned around the torque transferring member, the diameter of the coil can be made larger than what is possible with the prior art combined electrically conducting and torque transferring coils. This will also increase the inductance.
Within this overall idea, the invention may be modified in many different ways. As stated, the torque transferring member is tubular having an inner bore. This is done for the purpose of allowing insertion of a guide wire into the inner bore to enable guiding of the distal end of the lead to a desired location inside a body. Hence, the diameter of the inner bore is large enough for the guide wire to be inserted into the bore. Besides this requirement, the torque transferring member can be formed in many different ways. In the prior art, the torque transferring member is normally formed of three to five comparatively thick, metallic wires in order to function both as an electrical conductor as well as a torque transferring member. The several rather thick wires will give the coil a sufficient mechanical strength to transfer the required torque, but will also give the coil a rather large pitch, which will reduce the inductance. Also, the torque transferring member according to the invention may be formed in a similar way, with the exception that the wires are not electrically conducting between an electrode at the distal end and a connector at the proximal end. However, the torque transferring member could also be formed of an electrically non-conducting material, such as e.g. a polymeric material, which can be formed as a coil of one or more helical threads or as a flexible tubing.
The medical implantable lead can be provided with more than one electrode, e.g. two electrodes for a bipolar lead, three electrodes for a tripolar lead, etc. The electrically conducting wires for each electrode can optionally be provided in separate coils, which are co-axially arranged in relation to each other, or two or more separate electrically conducting wires, dedicated for different electrodes, can be provided side by side in one and the same coil. One advantage with an embodiment according to the latter case is that the overall diameter of the lead can be made smaller than in the former case. However, the inductance will be somewhat lower in the latter case in relation to the former, since the pitch of each individual wire will be somewhat larger. This can be alleviated by forming the coil from wires having a sufficient thin cross section.
Since the helix functions as an electrode, and is rotatable in relation to the lead, together with the torque transmitting member, arrangements should be made in respect of the electrical connection of the helix to the electrically conducting coil. This is due to the fact that the electrically conducting coil dedicated for the helix is non-rotating while the torque transferring member is rotatable in relation to the electrically conducting coil. The electrical connection between the helix and the coil can be ensured by e.g. arranging a sliding electrical contact between the helix and the specific wire. However, the electrical connection between the electrically conducting coil and the helix may be maintained also in many other ways, as realized by the skilled person.
In a medical implantable lead according to the invention, the mechanical transfer of torque from the proximal to the distal end, for rotating and extending the helix for screwing it into the tissue, is separated from the electrical conducting between the monitoring and/or controlling device and an electrode member in form of a helix at the distal end. More precisely, the torque is transferred by means of a tubular torque transferring member, which does not transfer any electrical current between the monitoring and/or controlling device and the helix. On the other hand, the electrical signals are conducted by a coil arranged on the outside of the torque transferring member and formed by helically wound wires having an outer non-conducting layer, such that adjacent loops of the coil will be electrically insulated from each other and the coil will function as an inductor. By a medical implantable lead formed in this way, it is possible to achieve a sufficient inductance in the conducting coil to prevent or at least reduce the strength of induced high frequency current from an electromagnetic field, into the electrically conducting coil to a sufficient degree that is harmless for the tissue. At the same time, the torque transferring member can be made with a sufficient strength and rigidity to allow transferring of the torque required. In embodiments of the invention, the electrically conducting coil may e.g. be formed of a wire comprising a silver core, which presents an advantageous low resistance to the signals and therefore can be given a small cross sectional dimension, such that the coil can be formed with a small pitch which will increase the inductance. The non-conducting layer around the wire core may be formed of a mineral or a polymer, such as e.g. ETFE (Ethylene Tetra Fluor Ethylene).
Since the inner tubular torque transferring member is mechanically connected to the helix but has no electrically conducting function to and from the helix, whereas the electrically conducting coil arranged outside of the tubular torque transferring member is not adapted to mechanically transfer any torque to the helix, the one or more conducting wires in the electrically conducting coil are arranged to always maintain the electrical connection between a connector at the proximal end and the helix at the distal end irrespective of the rotated position of the tubular torque transferring member and the helix.
Within the overall idea, the invention may be altered and modified in many different ways. For example, the tubular torque transferring member may optionally be formed as a flexible tube or as a helical coil of one or more threads or wires. It may also optionally be formed of an electrically insulating or a conducting material. In the former case no special measures has to be taken for insulating the tubular torque transferring member electrically from the helix or from the connector at the proximal end, such as may have to be done in case the tubular torque transmitting member is formed of an electrically conducting material. The connecting structure at the proximal end of the lead, which is adapted to be connected to a monitoring and/or controlling device, is formed with a connector pin which comprises an inner control member and a connector arranged co-axially outside of the control member. Accordingly, at least a part of the outer surface of the connector pin will be formed by the connector, which is electrically connected to an electrically conducting coil and the helix and which is adapted to be electrically connected to the monitoring and/or controlling device. The control member is rotatably arranged within the connector and mechanically connected to the torque transferring member and the helix. The control member can optionally be entirely surrounded by the connector such that only a proximal end of the control member is visible and accessible, in which case some form of engagement means has to be formed at the end surface for engagement with a suitable rotary tool for performing rotation of the torque transferring member and the helix, or project a distance out from the proximal end of the connector such that it forms a part of the surface of the connector pin. In the latter case rotation may be performed by gripping the control member by means of a gripping tool around the outer surface. Preferably, the projecting part of the control member is formed with an enlarged cross section such that it will have the same diameter as the connector. Moreover, the control member is preferably electrically insulated from the connector in case the torque transferring member and/or the control member is electrically conductive, e.g. metallic. The electrical insulation can preferably be formed as a sleeve surrounding the control member, but could also be formed as e.g. two ring members at a distance from each other. The control member may either be rotatable within the electrical insulation, or the electrical insulation may be rotatable within the connector.
The embodiments described and illustrated hereinafter are given solely for exemplifying reasons and are not intended to be comprehensive. Accordingly, many other embodiments could be conceivable within the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a medical implantable lead.

FIG. 2 is a view in an enlarged scale of the lead in FIG. 1 in a shortened state showing only the proximal and the distal ends of the lead.

FIG. 3 is a longitudinal section along the line A-A in FIG. 2 of a portion of a medical implantable lead according to a first embodiment.

FIG. 4 is a cross section along the line B-B in FIG. 2 of the lead according to FIG. 3.

FIG. 5 is a longitudinal section along the line A-A in FIG. 2 of a portion of a medical implantable lead according to a second embodiment.

FIG. 6 is a cross section along the line B-B in FIG. 2 of the lead according to FIG. 5.

FIG. 7 is a longitudinal section through a distal portion of the medical implantable lead, illustrating an embodiment of the electrically connection to the electrodes as well as the mechanically connection to the helix, which is in a retracted state.

FIG. 8 is a longitudinal section according to FIG. 7 with the helix in an extended state.

FIG. 9 is a longitudinal section through the proximal end of a lead according to a first embodiment of the invention.

FIG. 10 is a combined longitudinal section and perspective view of the lead according to FIG. 9 together with a perspective view of a rotary tool.

FIG. 11 is a perspective view of the proximal end of the lead according to FIGS. 9 and 10.

FIG. 12 is a perspective view of a rotary tool for interaction with a medical implantable lead according to FIGS. 9-11.

FIG. 13 is a longitudinal section through the proximal end of a lead according to a second embodiment of the invention.

FIG. 14 is a combined longitudinal section and perspective view of the lead according to FIG. 13.

FIG. 15 is a perspective view of the proximal end of the lead according to FIGS. 13 and 14.

FIG. 16 is a perspective view of the proximal end of the lead and a clamp gripping around the control member.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is first made to FIG. 1, in which is illustrated a medical implantable lead according to the invention in a perspective view. The lead has a connecting structure 1 at a proximal end for connection to a not shown monitoring and/or controlling device such as a pacemaker or the like, an intermediate flexible lead part 2, and a so called header 3 at a distal end. The header is provided with a helix 4, which can be screwed out in the axial direction of the lead from a cavity at the distal end of the header. The helix has the function of attaching the distal end of the lead to the heart, by being screwed into the tissue, and also functions as an electrode for receiving and/or transmitting electrical signals from and to the tissue, respectively. The header is also provided with a second electrode, a so called indifferent electrode 5, which is formed as a ring and positioned a small distance from the distal end and has the purpose of forming a complete current path together with the helix.
The proximal and the distal ends of the lead according to FIG. 1, are illustrated in an enlarged scale in the shortened representation of the lead in FIG. 2. The helix 4 for fixation of the distal end of the lead to tissue as well as for function as an electrode is shown in an extended state. However, during insertion of the lead into a body, the helix is retracted into the bore of the header 3 having a tubular shape at the distal end. In addition to a tip electrode in form of the helix, which is adapted to be screwed into the tissue, the lead has, as is mentioned above, a second electrode in form of the ring electrode 5 on a short distance from the distal end.
At the proximal end, the connecting structure 1 for connection to a not shown monitoring and/or controlling device comprises a first fluid tight sealing member 6 and a second fluid tight sealing member 6′. The sealing members are formed of an elastic material, in order to achieve a fluid tight connection to a socket recess of the monitoring and/or controlling device. In the area being positioned proximal in relation to the first sealing member 6, the lead is provided with a first electrically conducting connector 7 and in the area between the first and second sealing members the lead is provided with a second electrically conducting connector 7′, as is described more in detail below, which are adapted to be electrically coupled to mating connectors inside the monitoring and/or controlling device. The first connector 7 is in electrical contact with the helix 4, whereas the second connector 7′ is in electrical contact with the ring electrode 5 by means of one or more electrical conducting coils inside the lead, as is to be explained more in detail below. In the most proximal end, the lead is provided with a rotatable control member 8, which in the embodiment of FIG. 2 is surrounded by the first connector 7 and accordingly not visible therein. The control member 8 is, according to the invention, separated from the connectors 7, 7′ and by means of the control member the helix 4 can be rotated and screwed out from the bore inside the header 3 and into the tissue.
Now reference is made to FIGS. 3 and 4, in which are illustrated a first embodiment of the flexible lead part 2 in a longitudinal section as well as a cross section through the lead, respectively. The lead comprises an inner tubular torque transferring member 9, an inner fluid tight tubing 10, an electrically conducting coil 11 and an outer fluid tight tubing 12. The inner tubular torque transferring member is rotatable arranged inside the inner tubing and is formed as a coil of five comparatively thick and rigid helical wires of e.g. metal or polymer, such that it is well suited for transferring of a torque from the proximal to the distal end of the lead. Moreover, the torque transferring member 9 defines an inner bore 13 for the purpose of allowing insertion of a guide wire or the like for guiding the tip of the lead to a desired position inside a body. The electrically conducting coil 11 is composed of two separate, co-radially wound wires 14, 14′, each having an electrically conducting core 15 and a surrounding electrically insulating layer 16, such that they form two electrically separated inductance coils.
With reference also to FIG. 2, it is to be understood that the structure of the flexible lead part 2 as illustrated in FIGS. 3 and 4, extends from the connecting structure 1 at the proximal end to the header 3 at the distal end. Moreover, the tubular torque transferring member 9 is in its proximal end mechanically connected to the rotatable control member 8 and in its distal end mechanically connected to the helix 4, such that by rotating the rotatable control member it is possible to rotate the helix and extend it out from the inner bore of the header and screw it into the tissue. One of the wires in the electrically conducting coil 11 is in its proximal end electrically connected to the first connector 7 and in its distal end electrically connected to the helix 4, whereas the other wire in the electrically conducting coil is in its proximal end electrically connected to the second connector 7′ and in its distal end electrically connected to the ring electrode 5.
Reference is then made to FIGS. 5 and 6, in which are illustrated a second embodiment of the flexible lead part 2 in a longitudinal section as well as a cross section through the lead, respectively. As in the first embodiment according to FIGS. 3 and 4, this embodiment has an inner tubular torque transferring member 9, formed in a similar way as in the first embodiment of five helical wires, and an inner fluid tight tubing 10. However, this embodiment has two separate electrically conducting coils, one inner coil 17 and one outer coil 17′, separated by an intermediate fluid tight tubing 18. Each of the electrically conducting coils is formed of one single wire 14 and 14′, respectively, having an electrically conducting core 15 and a surrounding electrically insulating layer 16, such that they form two coaxially arranged inductance coils. Also this embodiment has an outer fluid tight tubing 12.
As in the first embodiment, the tubular torque transferring member 9 is in its proximal end mechanically connected to the rotatable control member 8 and in its distal end mechanically connected to the helix 4, such that by rotating the control member it is possible to rotate the helix and extend it out from the inner bore of the header and screw it into the tissue. The inner electrically conducting coil 17 is in its proximal end electrically connected to the first connector 7 and in its distal end electrically connected to the helix 4, whereas the outer electrically conducting coil 17′ is in its proximal end electrically connected to the second connector 7′ and in its distal end electrically connected to the ring electrode 5.
Reference is then made to FIGS. 7 and 8 of the drawings, in which is illustrated an embodiment of a connection of the electrically conducting wires 14, 14′ to the electrodes as well as the tubular torque transferring member 9 to the helix 4. FIGS. 7 and 8 are longitudinal sections through the distal portion of a medical implantable lead, according to the embodiment as illustrated and described in relation to FIGS. 3 and 4, with the helix being retracted and extended, respectively.
The longitudinal sections of FIGS. 7 and 8 are taken at the joint between the header 3, as seen to the right, and the distal end portion of the flexible lead part 2 as illustrated in FIGS. 3 and 4. The header is made of a rigid material such as metal or a polymer and is formed with an inner bore 19, in which the helix 4 is rotatably and displaceably accommodated. In the joint region between the header and the flexible lead part, the electrically conducting ring electrode 5 is provided, which also functions as a joint connector in that it comprises a distal shoulder surface, in which the proximal end of the header 3 is located and attached, and a proximal shoulder surface in which the distal end of the flexible lead part 2 is located and attached. A short distance towards the distal end from the ring electrode 5, the lead is provided with a fixed support member 20. Both the ring electrode 5 and the support member 20 are formed with a through bore, through which a shaft 21 is rotatably and displaceably inserted, at the distal end of which the helix 4 is mounted. The shaft 21 is of an electrically conducting material and to prevent electrical connection between the shaft 21 and the ring electrode 5 as well as the support member 20, in case it is manufactured of an electrically conducting material, electrically insulating shaft bushings 22 are arranged in each of the through bores. To allow rotation and displacing of the helix 4 out from and into the inner bore 19 of the header, the tubular torque transmitting member is mechanically connected to the proximal end of the shaft. In case the tubular torque transferring member 9 is of an electrically conducting material, the connection is arranged in an electrically non-conducting fashion, such as via an electrically insulating sleeve 23 or the like. The electrically conducting coil of the lead comprises two electrically conducting wires 14, 14′, which are electrically insulated from each other. To accomplish electrical connection to each of the ring electrode 5 and the helix 4, one of the electrical conducting wires 14′ is electrically connected to the ring electrode 5, whereas the other electrically conducting wire 14 is electrically connected to a sliding contact 24 arranged on the support member 20, the sliding contact being in permanent electrically contact with the shaft 21, which is in electrically contact with the helix 4. In this way an electrically connection is ensured with the helix in spite of the fact that the tubular torque transferring member 9 is not electrically conducting and irrespective of the position of the helix.
The embodiment of FIGS. 7 and 8 are only an exemplifying embodiment of how the mechanical and electrical connections between the helix 4 and the tubular torque transferring member 9 and the electrically conducting coils 14, 14′, respectively, can be maintained as well as separated. It is to be understood, however, that this embodiment is only exemplary and that these functions can be realized also in many other different ways.
Now reference is made to FIGS. 9 to 11 for a detailed description of a first embodiment of the arrangement of the connecting structure at the proximal end of the medical implantable lead according to the invention. As can be seen, the connecting structure is comprised of a thickened portion 25 and a connector pin 26 protruding from the proximal end of the thickened portion. A first fluid tight sealing member 6 is arranged around the connector pin adjacent the proximal end of the thickened portion. A second fluid tight sealing member 6′ is arranged around the thickened portion in an intermediate position of the same.
In prior art, normally the entire connector pin 26 is metallic and functions both as an electrical connector, which is in electrical connection with an inner electrically conducting coil connected to the helix at the distal end, as well as a rotatable control member for performing rotation of the helix by being rotatably mounted in the thickened portion. However, according to the invention, the connector pin is composed of an inner rotatable control member 8, which is connected to the inner torque transferring member 9 and is rotatably arranged within an outer, tubular electrically conducting connector 7, which in its turn is unrotatably mounted to the thickened portion and electrically connected to the helix 4 at the distal end via an electrically conducting coil 11, which is separated from the torque transferring member 9.
In this embodiment, the torque transferring member 9 and the control member 8 are metallic and accordingly electrically conductive. To prevent transfer of any electrical current, which may be induced into the torque transferring member by a surrounding electromagnetic field, from the torque transferring member to the electrically conducting coil 11 and hence to the helix 4, there is arranged an electrically insulating layer in form of an insulating tube 27 between the control member 8 and the connector 7. The insulating tube may optionally be unrotatably mounted to the connector 7, in which case the control member 8 is rotatable inside the insulating tube, or be unrotatably mounted to the control member, in which case the control member and the insulating tube are jointly rotatable within the connector. In case the control member and/or the torque transferring member would be of an electrically non-conductive material, the insulating tube could be dispensed with, since in that case no current can be induced into the torque transferring member from an electromagnetic field.
The control member 8 is tubular with a through bore 28 to allow insertion of a not shown guide wire through the control member and the tubular torque transferring member to the distal end of the lead. This is done for the purpose of performing guiding of the distal end of the lead, by means of the guide wire, to a desired position within a body, e.g. within a heart. As is evident from the drawings, in this embodiment the control member 8 is located entirely within the connector 7. To allow rotation of the control member, and hence also the torque transferring member and the helix, the proximal end of the through bore 28 in the control member is hexagonally formed to provide an engagement means 29 for a complementary formed rotary tool 30, as is illustrated in FIGS. 10 and 12. The rotary tool is formed with a body 31 and a protruding shaft 32 having a hexagonal cross section to be inserted into the hexagonally formed engagement means 29 in the control member 8. Also the rotary tool 30 is provided with a through bore 33 through the body and the shaft to allow insertion of the guide wire while the rotary tool is connected to the lead.
The thickened portion of the connecting structure comprises a proximal electrically insulating portion 34, an intermediary electrically conducting second connector 7′ and a distal electrically insulating sleeve 35. The lead according to this embodiment is provided with only one electrically conducting coil 11. However, the electrically conducting coil comprises two separate electrically conducting wires 14, 14′, each surrounded by an electrically insulating layer 16, as is illustrated in FIGS. 3 and 4. One of the wires 14 is electrically connected to the helix 4 at the distal end and to the distal end of the first connector 7 within the proximal electrically insulated portion 34 of the thickened portion of the connecting structure at the proximal end of the lead. The other electrically conducting wire 14′ of the electrically conducting coil 11 is connected to the indifferent electrode 5 at the distal end and to a distal end of the second connector 7′ which is formed as a protruding flange having a smaller cross sectional dimension than the rest of the connector. The connections between the first and second electrically conducting wires of the electrically conducting coil and the first and second connector, respectively, appears from FIGS. 9 and 10.
As is also seen from FIGS. 9 and 10, the outer fluid tight tubing 12 of the electrically conducting coil 11 is thread over the flange portion of the second connector 7′ and the outer flexible sleeve 35 is thread onto the flange portion over the fluid tight tubing for protecting the transition section between the connecting structure and the flexible lead part.
Reference is then made to FIGS. 13-15 in which is illustrated a second embodiment of the arrangement of the connecting structure at the proximal end of the medical implantable lead according to the invention.
As in the embodiment according to FIGS. 9-11, the connecting structure according to this embodiment comprises a thickened portion 25 and a connector pin 26 protruding from the proximal end of the thickened portion. A first fluid tight sealing member 6 is arranged around the connector pin adjacent the proximal end of the thickened portion. A second fluid tight sealing member 6′ is arranged around the thickened portion in an intermediate position of the same.
Moreover, the connector pin 26 is composed of an inner rotatable control member 8, which is connected to the inner torque transferring member 9 and is rotatably arranged within an outer, tubular electrically conducting connector 7, which in its turn is unrotatably mounted to the thickened portion and electrically connected to the helix 4 at the distal end via an electrically conducting coil 11, which is separated from the torque transferring member 9.
The torque transferring member 9 and the control member 8 are metallic and accordingly electrically conductive. To prevent transfer of any electrical current from the torque transferring member to the electrically conducting coil 11 and hence to the helix 4, there is arranged an electrically insulating layer in form of an insulating tube 27 between the control member 8 and the connector 7. The insulating tube may optionally be unrotatably mounted to the connector 7, in which case the control member 8 is rotatable inside the insulating tube, or be unrotatably mounted to the control member, in which case the control member and the insulating tube are jointly rotatable within the connector.
The control member 8 is tubular with a through bore 28 to allow insertion of a not shown guide wire through the control member and the tubular torque transferring member to the distal end of the lead. This is done for the purpose of performing guiding of the distal end of the lead, by means of the guide wire, to a desired position within a body, e.g. within a heart.
The thickened portion of the connecting structure comprises a proximal electrically insulating portion 34, an intermediary electrically conducting second connector 7′ and a distal electrically insulating sleeve 35. The lead also according to this embodiment is provided with only one electrically conducting coil 11, comprising two separate electrically conducting wires 14, 14′, each surrounded by an electrically insulating layer 16, as is illustrated in FIGS. 3 and 4. One of the wires 14 is electrically connected to the helix 4 at the distal end and to the distal end of the first connector 7 within the proximal electrically insulated portion 34 of the thickened portion of the connecting structure at the proximal end of the lead. The other electrically conducting wire 14′ of the electrically conducting coil 11 is connected to the indifferent electrode 5 at the distal end and to a distal end of the second connector 7′ which is formed as a protruding flange having a smaller cross sectional dimension than the rest of the connector. The connections between the first and second electrically conducting wires of the electrically conducting coil and the first and second connector, respectively, appears from FIGS. 9 and 10.
As is also seen from FIGS. 9 and 10, the outer fluid tight tubing 12 of the electrically conducting coil 11 is thread over the flange portion of the second connector 7′ and the outer flexible sleeve 35 is thread onto the flange portion over the fluid tight tubing for protecting the transition section between the connecting structure and the flexible lead part.
As described so far, this embodiment is identical with the first embodiment. However, in this embodiment the connector pin 26 has a somewhat different structure. More precisely, the control member 8 is not entirely surrounded by the connector 7. Instead the control member projects from the proximal end of the connector where it is formed with an increased proximal portion 36 having a cross sectional dimension that is equal to the cross sectional dimension of the rest of the connector pin and consequently the control member constitutes the outer surface of the proximal end of the connector pin. To insulate the control member 8 electrically from the first connector 7, also the insulating tube 27 between the control member and the connector is formed with an increased proximal portion 37 having a cross sectional dimension that is equal to the cross sectional dimension of the rest of the connector pin, such that the connector pin is provided with an insulating surface between the control member and the first connector.
Moreover, the control member is not formed with any specific engagement means for engagement with a rotary tool, as in the embodiment according to FIGS. 9-11. To rotate the torque transferring member and the helix during implanting of the lead inside a body, the proximal portion 36 may instead be gripped by means of an arbitrary gripping tool such as a clamp 38, as is illustrated in FIG. 16. The clamp 38 is made of an elastic material, such as a plastic, and comprises two shanks 39, 39′ which are formed as one unitary piece and being connected in a connecting portion 40 adjacent a lower end, wherein the clamp forms a gripping portion 41 in form of a recess below the connecting portion. Accordingly, by gripping upper ends of the shanks 39, 39′ by hand, a physician can displace them towards each other, in which case the gripping portion 41 in the lower end will open up due to elastic deformation in the connecting portion 40 such that the gripping portion may be positioned over the proximal portion 36 of the control member 8. Due to the elastic characteristics in the material, the gripping portion will clamp around the control member such that the physician may rotate the control member, and hence also the helix 4 at the distal end, by rotating the clamp 38.
Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted heron all changes and modifications as reasonably and properly come within the scope of their contribution to the art.

Claims

1.-10. (canceled)

11. An MRI-compatible medical implantable lead comprising:

a lead body adapted to be implanted into a human or animal body for monitoring and/or controlling an organ inside the body;

a connecting structure comprising a connector pin at a proximal end of the lead body, said connector pin comprising a rotatable control member;

a rotatable tubular torque transferring member connected to the rotatable control member;

a combined fixation means and electrode member in form of a helix at a distal end of the lead, said helix being connected to said rotatable tubular torque transferring member and being rotatable in relation to the lead body and extendable out from said distal end, by rotation of the control member and the tubular torque transferring member, for fixation of the lead to the organ;

a connector at said proximal end of the lead body electrically connected to the helix by at least one electrically conducting wire formed as an electrically conducting coil, said coil being separate from the tubular torque transferring member and rotatably fixed in relation to the lead, whereby the tubular torque transferring member is rotatably arranged within the electrically conducting coil and having no electrically conducting function to or from the helix;

said electrically conducting coil comprising one or more individual wires, each comprising an electrically conducting wire core and a surrounding electrically insulating layer; and

said connector pin comprising said control member and said connector, said control member being rotatably arranged within said connector.

12. A medical implantable lead according to claim 11, wherein the control member is electrically insulated from the connector.

13. A medical implantable lead according to claim 11, wherein the control member and the connector are electrically insulated from each other by an electrically insulating member.

14. A medical implantable lead according to claim 13, wherein the electrically insulating member is an electrically insulating sleeve and the connector is arranged at the outer circumference of the insulating sleeve.

15. A medical implantable lead according to claim 13, wherein the electrically insulating member is in one unitary piece.

16. A medical implantable lead according to claim 13, wherein the electrically insulating member is non-rotatably mounted to said connector, and said control member is rotatable inside said insulating member.

17. A medical implantable lead according to claim 13, wherein the electrically insulating member is non-rotatably mounted to said control member, and said control member and said electrically insulating member are jointly rotatable within said connector.

18. A medical implantable lead according to claim 11, wherein that the connector is a metallic sleeve completely surrounding the control member.

19. A medical implantable lead according to claim 18, wherein the control member has a rotary engagement portion configured to engage a rotary tool.

20. A medical implantable lead according to claim 19, wherein the rotary engagement portion is a recess having engagement formations at the proximal end of the control member.

21. A medical implantable lead according to claim 11, wherein the control member projects with a proximal portion beyond the connector at the proximal end of the lead body.

22. A medical implantable lead according to claim 21, wherein the proximal portion of the control member is adapted to be gripped by a gripping tool for rotation of the control member.

23. A medical implantable lead according to claim 11, wherein said connecting structure comprises a thickened portion and said connector is non-rotatably mounted to said thickened portion.