Patent Publication Number: US-2013245732-A1

Title: Lead header and manufacture thereof

Description:
TECHNICAL FIELD 
     The present embodiments generally relate to lead headers of implantable medical leads and to methods of manufacturing such lead headers. 
     BACKGROUND 
     Implantable medical leads form the electrical connection between an implantable medical device (IMD), such as cardiac pacemaker, cardiac defibrillator or cardioverter, and body tissue, such as the heart, which is to be electrically stimulated and/or sensed. As is well known, the implantable medical leads connecting the IMD with the tissue may be used for pacing/defibrillation and/or for sensing electrical signals produced by the tissue. 
     The implantable medical leads of today and in particular cardiac implantable medical leads can generally be divided into two classes depending on the tissue anchoring arrangement of the leads. Firstly, so-called passive fixation leads comprise radially protruding elements in the distal lead ends. These elements can become embedded in the trabecular network inside the heart and thereby provide an anchoring of the lead to the heart tissue. Examples of such protruding elements include collars, tines and fines. Passive leads are generally characterized by low chronic capture threshold and high impedance. 
     The other class of leads includes so-called active fixation leads. Such a lead typically comprises, in its distal end, a helical fixation element that can be screwed into the endocardium and myocardium to provide the necessary lead-to-tissue anchoring. Generally, active leads have superior ability to fixate without the need for any trabecular network. 
     The helical fixation element is generally extendable and retractable relative to the distal lead end by providing a post projecting radially inwardly from the lead header. By then applying a rotating motion at a connector pin in the proximal end of the lead, the rotational movement is transferred via an inner conductor and helix shaft up to the helical fixation element. The rotation of the helical fixation element forces, due to the post, the helical fixation element to advance or retract within the lead header. 
       FIG. 1  is a cross-sectional view of a current design of a typical lead header  100  for an active fixation lead. The lead header  100  basically consists of two separate pieces: a header body  110  and a marker ring  140 . These two pieces  110 ,  140  are typically manufactured as respective out-of-precision drawn tubes and cut to desired length using, for instance, a Swiss machine. The marker ring  140  additionally comprises slots  150  that are used to securely attach a silicon soft tip  170  (see  FIG. 2 ) to the marker ring  140 . Correspondingly, the header body  110  comprises a through-hole  120  into which the above mentioned post  160  is inserted during assembling. The header body  110  further comprises a cut out  130  onto which the marker ring  140  is threaded during manufacture. The slots  150 , the through-hole  120  and the cut out  130  need to be laser cut prior to assembling the marker ring  140  and the header body  110  together. Laser welding is then applied to securely attach the marker ring  140  to the header body  110 . 
     The post  160  is inserted in the through-hole  120  of the header body  110  and is laser welded to the header body  110 . This is a high-precision step due to the very small size of the components. Then the silicon soft tip  170  is molded over the marker ring  140  and a portion of the header body  110  as shown in  FIG. 2 . 
     Thus, the manufacture of the lead header  100  for prior art active fixation leads requires high precision and is very complex due to the small size of the components. Hence, the assembling process is costly and requires high skill of the operator that manually assemblies and attaches the different pieces together to form the final lead header  100 . 
     There is therefore a need for a lead header design that simplifies the manufacture process for active fixation leads as compared to prior art solutions. 
     SUMMARY 
     It is a general objective to provide a lead header for implantable medical leads that can be easily manufactured. 
     An aspect of the embodiments relates to a lead header for an implantable medical lead. The lead header is in the form of a metal sheet bent to form a metal tube having a lumen. The metal sheet has a protruding portion, e.g., lip, arranged in connection with a first longitudinal side of the metal sheet. The lip is bent to protrude radially inwardly into the lumen and is configured to transform a rotation of a helical fixation element at least partly present in the lumen into a longitudinal movement of the helical fixation element relative to the lead header. 
     Another aspect of the embodiments relates to an implantable medical lead comprising a proximal lead portion connectable to an implantable medical device. A tubular lead body has a first end connected to the proximal lead portion and a second, opposite end connected to a distal lead portion. This distal lead portion comprises a lead header in the form of a metal sheet bent to form a metal tube having a lumen. The metal sheet has a lip arranged in connection with a first longitudinal side and wherein the lip is bent to protrude radially inwardly into the lumen. The distal lead portion also comprises a helical fixation element at least partly present in the lumen of the metal tube. The lip is thereby configured to transform a rotation of the helical fixation element into a longitudinal movement of the helical fixation element relative to the lead header. 
     A further aspect of the embodiments relates to a method of manufacturing a lead header for an implantable medical device. The method comprises cutting a lip in connection with a first longitudinal side of a metal sheet. The lip is bent in a next step followed by bending the metal sheet to form a metal tube having a lumen. The lip thereby protrudes radially inwardly into the lumen and is configured to transform a rotation of a helical fixation element into a longitudinal movement of the helical fixation element relative to the lead header. 
     Yet another aspect of the embodiments relates to a lead header for an implantable medical lead. The lead header is in the form of a metal sheet bent to form a metal tube having a lumen. The metal sheet comprises a protruding portion, e.g., dent, protruding radially inwardly into the lumen and is configured to transform a rotation of a helical fixation element at least partly present in the lumen into a longitudinal movement of the helical fixation element relative to the lead header. 
     A further aspect of the embodiments relates to an implantable medical lead comprising a proximal lead portion connectable to an implantable medical device. A tubular lead body has a first end connected to the proximal lead portion and a second, opposite end connected to a distal lead portion. This distal lead portion comprises a lead header in the form of a metal sheet bent to form a metal tube having a lumen. The metal sheet comprises a dent protruding radially inwardly into the lumen. The distal lead portion also comprises a helical fixation element at least partly present in the lumen of the metal tube. The dent is thereby configured to transform a rotation of the helical fixation element into a longitudinal movement of the helical fixation element relative to the lead header. 
     Still further aspect of the embodiments relates to a method of manufacturing a lead header for an implantable medical device. The method comprises forming a dent in a metal sheet. The metal sheet is then bent to form a metal tube having a lumen. The dent thereby protrudes radially inwardly into the lumen and is configured to transform a rotation of a helical fixation element into a longitudinal movement of the helical fixation element relative to the lead header. 
     The lead header of the embodiments is easily manufactured and does not require the handling of a separate post but rather uses an integrated lip or a dent to achieve a rotation-to-translation transformation for the helical fixation element. The components for the lead header can be manufactured in a fully automated or at least semi-automated process, thereby reducing the time and cost for manufacturing the lead header. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with further objects and advantages thereof, may best be understood by making reference to the following description taken together with the accompanying drawings, in which: 
         FIG. 1  is a cross-sectional view of a lead header according to prior art; 
         FIG. 2  is a cross-sectional view of the lead header in  FIG. 1  with attached post and silicone soft tip; 
         FIG. 3  is a schematic drawing of a metal sheet used for forming a lead header according to an embodiment; 
         FIG. 4  is a cross-sectional view of a lead header according to an embodiment; 
         FIG. 5  is a cross-sectional view of a lead header according to an embodiment taken along the line A-A in  FIG. 4 ; 
         FIG. 6  is a schematic drawing of a metal sheet used for forming a lead header according to another embodiment; 
         FIG. 7  is a schematic drawing of a radiopaque metal sheet used for forming a marker ring according to an embodiment; 
         FIG. 8  is a cross-sectional view of a lead header with an attached marker ring according to an embodiment; 
         FIG. 9  is a cross-sectional view of a marker ring according to an embodiment; 
         FIG. 10  is a cross-sectional view of a lead header with an attached marker ring and a polymer tip tube according to an embodiment; 
         FIG. 11  is schematic drawing of a metal sheet used for forming a lead header according to a further embodiment; 
         FIG. 12  is a cross-sectional view of a lead header according to an embodiment taken along the line B-B in  FIG. 11  following bending the metal sheet into a tube; 
         FIG. 13  schematically illustrates an implantable medical lead according to an embodiment connectable to an implantable medical device; 
         FIG. 14  is an illustration of an implantable medical lead according to an embodiment; 
         FIG. 15  is a cross-sectional view of a distal portion of an implantable medical lead according to an embodiment; 
         FIG. 16  is a flow diagram illustrating a method of manufacturing a lead header according to an embodiment; 
         FIG. 17  is a flow diagram illustrating additional steps of the method in  FIG. 16 ; 
         FIG. 18  is a flow diagram illustrating an embodiment of attaching the marker ring in  FIG. 17 ; 
         FIG. 19  illustrates an example of a manufacturing process for a lead header; and 
         FIG. 20  is a flow diagram illustrating a method of manufacturing a lead header according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Throughout the drawings, the same reference numbers are used for similar or corresponding elements. 
     The present embodiments generally relate to lead headers for implantable medical leads and to methods of manufacturing such lead headers. The embodiments are in particular directed towards such lead headers that are used in so-called active fixation leads having a helical fixation element or screw structure that is used to anchor the implantable medical lead in a target tissue. 
     The lead headers of active fixation leads generally have a post or projecting structure protruding inwardly into a lumen or channel defined by the lead header. There the post is interposed between adjacent turns of the helical fixation element and will transform rotation of the helical fixation element into a longitudinal movement of the helical fixation element relative to the lead header. 
     The minute diameter of implantable medical leads and the lead headers of such implantable medical leads make the assembling process very time consuming and skill requiring, in particular with regard to handling the lead header and the post, which has been discussed in the background section in connection with  FIGS. 1 and 2 . 
     The present embodiments have taken a radically different approach as compared to the prior art by using a lead header in the form of a metal sheet or plate that is bent or folded to form a metal tube or cylinder.  FIG. 3  schematically illustrates an embodiment of such a metal sheet  11 . The metal sheet  11  has a length corresponding to the length of the lead header in the implantable medical lead and a width that substantially corresponds to the circumference of the metal tube following bending of the metal sheet  11  into a metal tube. In some embodiments, the width of the metal sheet  11  could be somewhat larger than the circumference of the metal tube in the case of a partial overlap of the longitudinal sides  15 ,  16  of the metal sheet  11  in the joint of the metal tube. 
     The metal sheet  11  comprises an integrated lip or bendable structure  14  that is arranged in connection with a first longitudinal side  15  of the metal sheet  11 . In the embodiment shown in  FIG. 3 , the lip  14  is arranged at and extends beyond the first longitudinal side  15 . This lip  14  is configured to be bent to protrude radially inwardly into the lumen of the metal tube.  FIG. 4  illustrates a cross-sectional view of the lead header  10  that is in the form of a metal tube  12  formed by bending the metal sheet  11  of  FIG. 3  and by bending the lip  14  to protrude into the lumen  13  of the metal tube  12 .  FIG. 5  is a cross-sectional view of the metal tube  12  taken along the line A-A shown in  FIG. 4 . As is clearly seen in  FIG. 5 , bending the metal sheet  11  into a cylinder will bring the two longitudinal sides  15 ,  16  close together to form a joint and thereby a metal tube  12  with the lip  14  protruding inwards into the lumen  13  of the metal tube  12 . 
     The lip  14  of the metal tube  12  protruding into the lumen  13  is configured to transform a rotation of a helical fixation element to be at least partly present in the lumen  13  into a longitudinal movement of the helical fixation element relative to the lead header  10 . Hence, the lip  14  is then interposed between adjacent turns of the helical fixation element to achieve this rotation-to-translation transformation. 
     In a particular embodiment, the lip  14  is simply bent to protrude as a straight structure (not shown) into the lumen  13 . This generally works well and the width of the lip  14  is thereby selected to be equal to or preferably smaller then the distance between adjacent turns in the helical fixation element in order to be interposed between such adjacent turns. 
     In this embodiment the lip  14  is basically bent 90 degrees relative to the flat metal sheet  11  in  FIG. 3  prior to bending the metal sheet  11  into a tube or cylinder shape. This lip  14  will thereby project radially inwardly into the lumen  13 . Also other overall bending configurations of the lip  14  are possible and within the scope of the embodiments. For instance and as shown in  FIG. 5 , the lip  14  could be bent to a general U-shape to form a post  17  protruding radially inwardly into the lumen  13 . Such a U-shaped configuration of the lip  14  might achieve a more stable post structure as compared to a lip  14  bent to form a straight structure protruding into the lumen  13 . Hence, the U-shaped lip  14  might withstand any forces exerted by the helical fixation element during rotation of the helical fixation element better without the risk of a structural deformation of the lip  14 . 
     In a particular embodiment the two longitudinal sides  15 ,  16  of the metal sheet  11  meet each other at a joint following bending the metal sheet  11  into the metal tube  12 . In such a case, a weld, such as a laser weld, can be applied between the first longitudinal side  15  and a second, opposite longitudinal side  16  to form a mechanical joint between the longitudinal sides  15 ,  16 . Welding additionally achieves a closed system for the metal tube  12  with regard to its envelope or side surface. 
     Also other forms of mechanical joints are possible and do not necessarily have to achieve a closed joint. Such mechanical joints could be based on the principles of dovetail joints where a series of pins extending from one of the longitudinal sides  15  interlock with a series of tails in the other longitudinal side  16 . 
       FIG. 6  schematically illustrates another embodiment of a metal sheet  11  that can be bent to form metal tube  12  of a lead header  10  for an implantable medical lead. In this embodiment the lip  14  is arranged in connection with the first longitudinal side  15  but its end is substantially aligned with the first longitudinal side  15 . Hence, the lip  14  does not necessarily extend beyond the first longitudinal side  15 . The embodiments also encompass any lip structure that is basically an intermediate of the ones shown in  FIGS. 3 and 6 . Thus, the lip  14  could be attached to the metal sheet body at a position further to the center in the transversal direction of the metal sheet  11  as compared to the first longitudinal side  15 , i.e. as shown in  FIG. 6 . However, the lip  14  may still extend beyond the first longitudinal side  15 , i.e. as shown in  FIG. 3 . 
     Regardless of arrangement position in connection with the first longitudinal side  15 , the lip  14  is bent to protrude radially inwardly into the lumen  13  formed by the metal sheet  11  when it has been bent to form the metal tube  12 . 
     In  FIG. 3 , the lip  14  is formed by cutting away metal sheet material beyond the first longitudinal side  15 , such as by punching, but keeping part of the metal sheet material corresponding to the lip  14  left. In  FIG. 6  slots are cut in the metal sheet  11  on either side of the lip  14  unless the lip  14  is arranged in connection with one of the ends of the first longitudinal side  15 . In this latter case a single slot is cut or punched in the metal sheet  11  to form the lip  14 . 
     The position of the lip  14  along the first longitudinal side  15  can be selected by the manufacturer to be anywhere from a first end of the first longitudinal side  15  up to the second, opposite end of the first longitudinal side  15 . 
     The metal sheet  11  can be made of any metal material that can be manufactured into a metal sheet  11  and bent to form a metal tube. The metal material should furthermore be non-toxic and implantable in a human or animal body. Non-limiting but preferred examples of such metal materials include titanium, titanium alloys and MP35N®, which is a nickel-cobalt-chromium-molybdenum alloy. It is further preferred if the metal material can be welded to form a joint between the longitudinal sides  15 ,  16 . 
     In a particular embodiment the lead header also comprises a marker ring in addition to the metal tube formed from the metal sheet. The marker ring is then made of a radiopaque material to be visible through X-ray imaging, for instance during implantation of the implantable medical lead. The radiopaque marker ring that is present close to the distal end and tip of the implantable medical lead will therefore be a tool used by the physician to visually track the tip of the implantable medical lead in the human or animal body during implantation. 
     The marker ring  20  is attached to a portion of an outer surface  18  (envelope surface) of the metal tube  12  as is shown in  FIG. 8 . In more detail, the marker ring  20  is attached to the outer surface  18  in connection with a first end of the metal tube  12  and where this first end faces the distal end or tip of the implantable medical lead, into which the lead header  10  is to be assembled. 
     In an embodiment, the marker ring  20  can be in the form of a drawn tube or ring of the radiopaque material that has an inner diameter that substantially corresponds to the outer diameter of the metal tube  12 . The marker ring  20  is then threaded on the metal tube  12  as is shown in  FIG. 8 . 
     In another embodiment, the marker ring  20  is in the form of a radiopaque metal sheet  21 , see  FIG. 7 , which is bent or folded to form the marker ring  20 .  FIG. 7  illustrates an embodiment of such a radiopaque metal sheet  21  and  FIG. 9  illustrates a cross-sectional view of the marker ring  20  once the radiopaque metal sheet  21  has been bent to a ring shape with the opposite sides  26 ,  27  of the radiopaque metal sheet  21  joined as shown in  FIG. 9 . 
     In such an embodiment, the radiopaque metal sheet  21  can be placed on a part of the outer surface  18  of the metal tube  12  and then bent around the circumference of the metal tube  12  to form the marker ring  20  of  FIG. 8  attached to a portion of the outer surface  18  of the metal tube  12 . Alternatively, the radiopaque metal sheet  21  is first bent to form the marker ring  20 , which is then threaded on the metal tube  12 . 
     The first side  26  of the radiopaque metal sheet  21  can be joined to the second, opposite side  27  by any of the joining techniques disclosed in the foregoing for the metal sheet  11 . For instance, welding, such as laser welding, can be applied to form a closed joint. Also other mechanical joining techniques can be used, such as a dovetail joint. 
     In a particular embodiment, a joint is further applied between a portion of the inner surface of the marker ring  20  and a portion of the outer surface  18  of the metal tube  12 . Such a joint could be a circumferential weld, such as a circumferential laser weld, to obtain a closed joint. Other types of joint and welding techniques can be used. 
     In an embodiment, the radiopaque metal sheet  21  comprises at least two slotted through-holes  22 ,  23 ,  24 ,  25  angled relative to each other. These through-holes  22 ,  23 ,  24 ,  25  can then be used to attach a polymer tip tube to the marker ring  20 , which is further disclosed herein. The relative angles of the through-holes is thought to improve the connection between the marker ring  20  and the polymer tip tube and prevent the polymer tip tube from unintentionally falling off the marker ring  20 . 
     The angled through-holes  22 ,  23 ,  24 ,  25  have a further benefit in that they enable rotation orientation of the implantable medical lead during implantation through X-ray imaging. Thus, an X-ray image of the implantable medical lead in the human or animal body clearly shows the marker ring and the angled through-holes  22 ,  23 ,  24 ,  25  therein. This will guide the physician and provide rotation information that can be used if a particular lead rotation orientation is desired. 
     The angled through-holes  22 ,  23 ,  24 ,  25  are preferably positioned on the radiopaque metal sheet  21  so that a first straight connection line  2  between a center  28  of the marker ring  20  and a center of a first through-hole  22 ,  24  is perpendicular to a second straight connection line  3  between the center  28  of the marker ring  20  and a center of a second through-hole  23 ,  25 . This is shown in  FIGS. 8 and 9 . In a particular embodiment the radiopaque metal sheet  21  comprises four slotted through-holes  22 ,  23 ,  24 ,  25  angled about 90 degrees relative to each other and positioned so that the first straight connection line  2  between the center of the first through-hole  22 , the center  28  of the marker ring  20  and a center of a third through-hole  24  is perpendicular to the second straight connection line  3  between the center of the second through-hole  23 , the center  28  of the marker ring  20  and a center of a fourth through-hole  25 . 
     In this embodiment, the through-holes  22 ,  23 ,  24 ,  25  have different dimensions with the first and third through-holes  22 ,  24  having larger lengths as compared to their widths while the second and fourth through-holes  23 ,  25  have larger widths as compared to their lengths. 
     The marker ring  20  can be made of any radiopaque material that can be visually seen in a human or animal body through X-ray imaging and that is non-toxic and implantable. The radiopaque material is preferably selected so that it can be manufactured into a radiopaque metal sheet  21  and bent to form the marker ring  20 . Non-limiting but preferred examples of such radiopaque materials include radiopaque metal materials selected from tantalum and alloys of platinum and iridium. It is further preferred if the radiopaque material can be welded to form a joint between the sides  26 ,  27  and furthermore is weldable to the metal material of the metal sheet  11 . Tantalum is generally readily weldable to titanium materials and a platinum-iridium alloy is typically weldable to MP35N®. 
       FIG. 10  is a cross-sectional view of an embodiment of a lead header  10  with the metal tube  12  and its bent lip  14 , the marker ring  20  and a polymer tip tube  30  molded on the marker ring  20  and at least a portion of the metal tube  12 . The polymer tip tube  30  can be made of any electrically isolating polymer material that can be molded over the marker ring  20  and the metal tube  12 . A non-limiting example of suitable polymer material is silicone. 
     The through-holes  22 ,  23 ,  24  of the marker ring  20  enables the polymer material to penetrate from the outside of the marker ring  20  through the through-holes  22 ,  23 ,  24  and extend along the inner surface of the marker ring  20  as is shown in  FIG. 10 . The polymer tip tube  30  is therefore securely anchored in the marker ring  20  and is thereby prevented from unintentionally falling off the lead header  10 . 
     In the embodiments discussed in the foregoing the metal sheet that is formed to the metal tube of the lead header comprises a bendable integrated lip that is cut or punched in the metal sheet to be arranged in connection with the first longitudinal side of the metal sheet.  FIGS. 11 and 12  illustrate another embodiment of achieving a post structure from a metal sheet. In this embodiment a dent  19  is formed in the metal sheet  11  by applying pressure to one of the main surfaces of the metal sheet  11 , for instance by punching. The dent  19  will then project along a normal to the main surface of the metal sheet  11 . This means that when the metal sheet  11  is bent to form the metal tube  12  the dent  19  will protrude radially inwardly into the lumen  13  of the metal tube.  FIG. 12  illustrates a cross-sectional view taken along the line B-B in  FIG. 11  following bending the metal sheet  11  into a metal tube  12 . The dent  19  will thereby be interposed between adjacent turns of a helical fixation element at least partly present in the lumen  13 . The dent  19  transforms a rotation of the helical fixation element to a longitudinal movement of the helical fixation element relative to the lead header and the metal tube  12 . 
     The embodiment of the metal sheet  11  and metal tube  12  shown in  FIGS. 11 and 12  can be used together with the marker ring and polymer tip tube discussed in the foregoing and shown in  FIGS. 7 to 10 . 
       FIG. 13  is a schematic overview of an implantable medical lead  40  according to an embodiment comprising a lead header as disclosed herein. The implantable medical lead  40  basically comprises a proximal lead portion  42  that is connectable to an implantable medical device  1 , such as a pacemaker, a cardiac defibrillator or cardioverter. The proximal lead portion  42  is connected to a first end of a tubular lead body  43  having its second, opposite end connected to a distal lead portion  41  comprising the lead header and the helical fixation element  48 . 
       FIG. 14  illustrates the implantable medical lead  40  in more detail. The proximal lead portion  42  preferably comprises a rotatable connector  44 , also sometimes referred to as a connector pin. The rotatable connector  44  is connectable to the implantable medical device. The rotatable connector  44  is mechanically and electrically connected to a conductor, typically in the form of a conductor coil running in a lumen of the tubular lead body  43 . The opposite end of the conductor is mechanically and electrically connected to the helical fixation element  48 . Thus, when the physician would like to move the helical fixation element  48  out from the lead header in the distal lead portion  41  or retract the helical fixation element  48  back into the lead header, he/she rotates the rotatable connector  44 . This rotation is propagated through the conductor down to the helical fixation element  48 . The lip or dent present in the metal tube of the lead header projecting into the lumen and interposed between adjacent turns of the helical fixation element  48  transforms this rotation into a longitudinal movement of the helical fixation element  48  relative to the lead header. 
     The implantable medical lead  40  could be a so-called bipolar or multipolar lead. In such a case, it comprises at least one electrode  46  in the distal lead portion  41  in addition to the helical fixation electrode  48  that preferably operates as a sensing and/or pacing electrode. The at least one other electrode  46  is then typically a so-called ring electrode  46  that is electrically connected to a second conductor, such as an outer conductor coil, running in the lumen of the tubular lead body  43  and ends at a ring connector  45  in the proximal lead portion  42 . 
       FIG. 15  is a cross-sectional view of the distal portion  41  of the implantable medical lead showing the lead header  10  of the embodiments.  FIG. 15  illustrates that the helical fixation element  48  is mechanically and electrically connected to an inner conductor coil  50  by means of the helix shaft  54  manufactured by an electrically conductive material such as platinum, gold, tantalum, titanium or an alloy such as platinum/iridium, e.g. Pt/Ir 90/10 or 80/20. The lead-connecting (proximal) end of the helical fixation element  48  and the distal end of the inner conductor coil  50  may be attached by, for instance laser welding or the like, to the opposite ends of the helix shaft  54 . The helix shaft  54  is journaled for rotation and axial movement within a sleeve  53  and includes a radially extending flange defining a proximal, radially-extending surface engageable against a distal extremity of the sleeve  53  to limit the retraction of the helical fixation element  48 . The sleeve  53  is preferably electrically conductive and secured to the metal tube  12  of the lead header  10 . 
     The proximal portion of the sleeve  53  has a counterbore terminating at a distal end wall. An electrically conductive tubular abutment  56 , such as of MP35N® or the like, L-shaped in cross section, has an axial portion connected, e.g. welded, to the proximal end of the helix shaft  54  and a flange projecting radially within the counterbore of the sleeve  53 . Thus, the abutment  56  being secured to the helix shaft  54  is movable rotationally and axially with the helix shaft  54  relative to the sleeve  53 . 
     Contained within the counterbore is an expandable/contractable contact member, preferably in the form of a metallic compression spring  55 . The compression spring  55  prevents the helical fixation element  48  from unintentionally moving out from the lead header  10  during implantation. 
     An outer insulating tube  49 , for instance of silicone rubber, polyurethane or OPTIM®, extends proximally from the ring electrode  46  and covers the main lead body up to the proximal lead portion. 
     The ring electrode  46  is in electrical contact with the ring connector of the proximal lead portion through an outer conductor coil  51 . The two conductor coils  50 ,  51  are electrically insulated by a longitudinally extending insulating tube  52 , such as made of silicone rubber, polyurethane or the like. The insulting tube  52  is disposed between the conductor coils  50 ,  51  to prevent electrical contact between the conductors  50 ,  51  and between the ring electrode  46  and the inner conductor coil  50 . 
     The distal lead portion  41  additionally comprises the lead header  10  with the metal tube  12 , the marker ring  20  and the polymer tip tube  30  previously discussed herein.  FIG. 15  clearly illustrates how the helical fixation element  48  is at least partly present in the lumen  13  of the metal tube  12  so that the lip  14  or the dent protrudes radially inwardly into the lumen  13  and is interposed between adjacent turns of the helical fixation element  48 . 
       FIG. 16  is a flow diagram of a method for manufacturing a lead header for an implantable medical lead according to an embodiment. The method generally starts in step S 1  where a lip is cut in connection with a first longitudinal side of a metal sheet. The lip can be formed by cutting or punching away excessive metal material on either sides of a portion of the metal sheet to get a lip extending beyond the first longitudinal side of the metal sheet as shown in  FIG. 3 . Alternatively, one or more slits can be cut or punched in the metal sheet to get a lip embodiment as shown in  FIG. 6 . 
     A next step S 2  bends the lip to form a post the projects substantially perpendicular from a main surface of the metal sheet. Hence the lip preferably extends along a normal to this main surface after the bending in step S 2 . The lip is optionally bent to form a U-shaped post as shown in  FIG. 5 . 
     In a next step S 3  the metal sheet is bent to form a metal tube having a lumen. By bending the lip in step S 2  the lip protrudes radially inwardly into the lumen following step S 3  to thereby be configured to transform a rotation of a helical fixation element at least partly present in the lumen into a longitudinal movement of the helical fixation element relative to the lead header. 
       FIG. 17  is a flow diagram illustrating additional, optional steps of the method in  FIG. 16 . The method continues from step S 3  in  FIG. 16 . A next step S 10  applies a weld, such as a laser weld, between the longitudinal sides of the metal sheet to form a closed joint in the metal tube. Alternative embodiments for joining the longitudinal sides of the metal sheet are possible as previously disclosed herein. 
     A marker ring of a radiopaque material is attached to a portion of an outer surface of the metal tube in step S 11 . If the marker ring is in the form of a pre-shaped ring step S 11  preferably involves threading the marker ring on the outer surface of the metal tube. Other embodiments of attaching the marker ring will be discussed further in connection with  FIG. 18  below. 
     Step S 12  molds a polymer tip tube on the marker ring and at least a portion of the metal tube. Thereafter the helical fixation element is introduced into the lumen of the metal tube in step S 13  to thereby have the lip or dent in the metal tube interposed between adjacent turns of the helical fixation element. 
       FIG. 18  is a flow diagram illustrating a particular embodiment of attaching the marker ring in  FIG. 17 . The method continues from step S 10  in  FIG. 17 . A next step S 20  cuts or punches slotted through-holes in a radiopaque metal sheet. At least two such slotted through-holes angled relative to each other are preferably cut in the radiopaque metal sheet as previously disclosed herein. The radiopaque metal sheet with the optional but preferred slotted through-holes is then bent to form the marker ring in step S 21 . Step S 21  could bend the radiopaque metal sheet around a portion of the metal tube. Alternatively, the radiopaque metal sheet is first bent to form the marker ring. The marker ring is then threaded onto the portion of the metal tube. 
     Step S 22  applies a weld between opposite sides of the radiopaque metal sheet to form a, preferably closed, joint in the marker ring. Alternatively other mechanical joints as discussed herein could be used. Step S 22  is preferably performed after attaching the marker ring to the metal tube but could actually be performed prior to threading the marker ring onto the metal tube. 
     Step S 23  applies a circumferential joint, such as weld and preferably laser weld, between the marker ring and the metal tube to mechanically attach the marker ring to the metal tube. The method then continues to step S 12  of  FIG. 17  to mold the polymer tip tube on the marker ring and the metal tube. 
     When manufacturing a lead header based on the metal sheet as disclosed in  FIGS. 11 and 12 , steps S 1  and S 2  of  FIG. 16  are replaced by forming the dent in the metal sheet as shown in step S 30  of  FIG. 20 . This dent is preferably formed by applying pressure to, such as punching, the metal sheet. The method then continues to step S 31  to bend the metal sheet with the dent into a metal tube with the dent protruding radially inwardly into the lumen of the metal tube. The optional steps of  FIGS. 17 and 18  can also be applied to the method illustrated in  FIG. 20 . 
       FIG. 19  schematically illustrates how a metal sheet for the lead header can be manufactured from a metal strip  60  in a serial process. A metal strip  60  is input in the manufacture process and guiding structures  61 ,  62 , represented by through-holes  61  and slotted through-holed  62  in  FIG. 19 , are cut or punched in the metal strip  60  in sub-process I. These guiding structures  61 ,  62  are used in the manufacture process to correctly align the metal strip  60  to the different cutting and bending sub-processes II-VI. A next sub-process II cuts one half of the metal sheet  11  with the following sub-process III cutting the other half to form the metal sheet  11  attached to the metal strip  60  at its two short sides. A next sub-process IV cuts the lip  14  in connection with the first longitudinal side of the metal sheet  11 . These sub-processes II to IV could be replaced by single cutting or punching sub-process in which the outer contour of the metal sheet with the lip  14  is formed directly from the metal strip  60 . Alternatively, the three sub-processes II to IV could be replaced by two sub-processes where sub-process II both cuts half the metal sheet  11  and the lip  14  in a single cutting/punching operation and with sub-process III cutting the other half of the metal sheet  11 . Sub-process V bends the lip  14  to form a post extending substantially parallel to a normal of the main surface of the metal sheet  11 . Finally sub-process VI bends the metal sheet  11  to form the metal tube  12  with the lid  14 /post  17  protruding radially inwardly into the lumen defined by the metal tube  12 . 
     Following sub-processes could apply a weld along the joint between the longitudinal sides of the metal sheet and finally cutting away the metal tube  12  from the metal strip  60 . 
     A similar procedure using a radiopaque metal strip can be used for manufacturing the marker ring of the lead header. 
     Hence, the lead header of the embodiments can be manufactured in a simple process that can be automated thereby reducing the cost and time of manufacturing and assembling a lead header for an implantable medical lead. 
     The embodiments described above are to be understood as a few illustrative examples of the present invention. It will be understood by those skilled in the art that various modifications, combinations and changes may be made to the embodiments without departing from the scope of the present invention. In particular, different part solutions in the different embodiments can be combined in other configurations, where technically possible. The scope of the present invention is, however, defined by the appended claims.