Abstract:
Methods of implanting a two-part cardiac lead in a heart are disclosed. The two-part cardiac lead has inner and outer portions and a pin. The inner and outer lead portions are separately advanced to a location of interest within the vasculature of a patient. The pin is attached to a proximal end of the inner lead portion and can provide a connection between the inner and outer lead portions.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a divisional application of prior application Ser. No. 10/888,862, filed Jul. 9, 2004, now U.S. Pat. No. 7,191,017, issued Mar. 13, 2007, which is herein incorporated by reference in its entirety. 

   TECHNICAL FIELD 
   The present invention is related to implantable cardiac leads used with a cardiac function management device such as a pacemaker, a defibrillator, or a cardiac resynchronization therapy device to monitor and control heart function. 
   BACKGROUND 
   Cardiac function management devices, including implantable pacemakers and implantable defibrillators, include at least one cardiac lead having an electrode for making contact with a portion of the heart. Such leads are typically connected to a pulse generator at their proximal end and to cardiac tissue at their distal end. When such a lead is positioned so as to stimulate the left ventricle, it is common to advance the lead deep into the cardiac veins in order to effectively sense and stimulate in the left ventricle. However, traditional leads are not well suited for implantation in the coronary veins because the veins are narrow and traditional leads are often too large in diameter. Therefore, it is desirable to have a cardiac lead of a smaller size for placement in the coronary vein for left ventricle sensing and stimulation. 
   One such smaller size lead comprises a two-part bipolar lead where the first part of the lead includes an insulated conductive coil with an electrode at the distal end and the second part of the lead includes a wire or cable with an electrically conductive surface at its distal tip, which is delivered down the center of the conductive coil. There is a need in the art for a connector for such a lead that connects and secures the conductive cable to the conductive surface. There is a further need for such a device including a terminal connector compatible with standard cardiac function management devices. 
   SUMMARY 
   The present invention, according to one embodiment, is a method of implanting a cardiac lead. The method comprises advancing an outer lead portion into a coronary vessel, the outer lead portion having a longitudinal lumen and a terminal connector located at a proximal end. The terminal connector defines an internal bore and is adapted to couple with a cardiac function management device. A conductive member of an inner lead portion is advanced through the longitudinal lumen. A pin is attached to a proximal end of the conductive member such that the pin mechanically engages the internal bore of the terminal connector. 
   The present invention, according to another embodiment, is a method of implanting a cardiac lead. The method comprises advancing an outer lead portion into a heart or a coronary vessel, the outer lead portion having a longitudinal lumen, a terminal connector located at a proximal end, and a sleeve connected to the terminal connector. The terminal connector defines an internal bore and is adapted to couple with a cardiac function management device. A conductive member of an inner lead portion is advanced through the longitudinal lumen. A pin is attached to a proximal end of the conductive member such that the pin mechanically engages and couples to the sleeve and is electrically insulated from the terminal connector by the sleeve. 
   The present invention, according to yet another embodiment, is a method of implanting a cardiac lead. The method comprises advancing a guide catheter to a desired location in or near a heart. An inner lead portion having a conductive member is advanced through the guide catheter. An outer lead portion having a longitudinal lumen and a terminal connector located at a proximal end of the outer lead portion is advanced over the inner lead portion. The terminal connector defines an internal bore and is adapted to couple with a cardiac function management device. The outer lead portion is advanced over the inner lead portion. A pin is attached to a proximal end of the conductive member such that the pin mechanically engages and couples to the internal bore of the terminal connector. 
   While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various obvious aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a cardiac function management system in accordance with the present invention. 
       FIG. 2  is a sectional view of a cardiac lead of  FIG. 1 , according to one embodiment of the present invention. 
       FIG. 3  is a partial sectional view of the proximal end and first portion of the cardiac lead of  FIG. 2 , according to one embodiment of the present invention. 
       FIGS. 4A-4B  are partial sectional views of the proximal end and first portion of the cardiac lead of  FIG. 2 , according to another embodiment of the present invention. 
       FIGS. 4C-4D  show side plan view of the portion of  FIG. 4B  indicated as  4 C- 4 D. 
       FIGS. 5A-5B  are partial sectional views of the proximal end and first portion of the cardiac lead of  FIG. 2 , according to a third embodiment of the present invention. 
       FIG. 6  is a partial sectional view of the proximal end and first portion of the cardiac lead of  FIG. 2 , wherein the pin is threadably engaged with the sleeve, according to a fourth embodiment of the present invention. 
       FIG. 7  is a partial sectional view of the proximal end and first portion of the cardiac lead of  FIG. 2 , according to a fifth embodiment of the present invention. 
       FIG. 8  is a partial sectional view of the proximal end and first portion of the cardiac lead of  FIG. 2 , according to a sixth embodiment of the present invention. 
       FIGS. 9A-9C  are partial sectional views of the proximal end and first portion of the cardiac lead of  FIG. 2 , according to a seventh embodiment of the present invention. 
       FIGS. 10A-10C  are partial sectional views of the jaws of  FIGS. 9A-9B , wherein the jaws include mechanisms for gripping the conductive member, according to alternative embodiments of the present invention. 
       FIGS. 11A-11C  are sectional views of the distal end of the cardiac lead of  FIG. 2 , according to yet other alternative embodiments of the present invention. 
       FIG. 12  is a flowchart showing an implantation process for implanting the cardiac lead of  FIG. 2  into the human heart. 
   

   DETAILED DESCRIPTION 
     FIG. 1  is a perspective view of a cardiac function management system  10  for delivering a treatment or therapy to a human heart. The cardiac function management system  10  may, for example, be a pacemaker, an ICD, or a cardiac resynchronization device. The system  10  includes a pulse generator  22  and a cardiac lead  24 . The pulse generator  22  includes a power source, circuitry for receiving and delivering electrical signals through the cardiac lead  24 , and circuitry for determining an appropriate therapy. 
   As shown in  FIG. 1 , the lead  24  is implanted into a human heart  25  through a coronary vein  26 . The lead  24  operates to convey electrical signals between the heart  25  and the pulse generator  22 . A proximal end  28  of the lead  24  is coupled to the pulse generator  22  and a distal end  30  includes to a surface electrode  32 . In the embodiment shown in  FIG. 1 , the cardiac lead  24  of the present invention extends through the superior vena cava  34 , the right atrium  36 , and the coronary sinus  38  into the coronary vein  26 , so that the surface electrode  32  is located in a branch of the coronary vein  26 . When positioned as above, the electrode  32  can be used to sense the electrical activity of the heart  25  or to apply a stimulating pulse to the left ventricle  40 . In other embodiments, the cardiac lead  24  of the present invention can also be implanted in any other portion of the heart as known in the art of cardiac function management. For example, it may be implanted in right atrium  36 , the left atrium  41 , the right ventricle  42 , or the pulmonary artery  43 . 
     FIG. 2  shows a sectional view of the cardiac lead  24  in accordance with the present invention. As shown in  FIG. 2 , the cardiac lead  24  includes an inner or first portion  44  and an outer or second portion  46 . The first portion  44  is sized to fit into and couple with the second portion  46 . The first portion  44 , shown from left to right in  FIG. 2 , includes a conductive member  50 , a connector assembly  51 , and a front seal  52 . As shown from left to right on the bottom portion of  FIG. 2 , the second portion  46  includes the surface electrode  32 , a lead body  54 , a rear seal  56 , and a terminal connector  58 . 
   The connector assembly  51  electrically and mechanically connects the cardiac lead  24  to the pulse generator  22 . The connector assembly  51  includes a pin  60 , which is configured to mechanically couple to the terminal connector  58  (or a tube or sleeve  62  as shown in  FIGS. 3-8 ). The pin  60 , which is made from an electrically conductive material, is adapted to connect electrically and mechanically to the cable or conductive member  50 . The connection can be pre-formed or formed upon coupling with the terminal connector  58 . In embodiments where the connection is formed upon coupling with the terminal connector  58 , the connection can be permanent or reversible. The pin  60 , however, is electrically insulated from the terminal connector  58 . In one embodiment, the conductive member  50  is a wire or a cable. The conductive member  50  may include an insulating sheath  61 . The insulating sheath  61  can be a polymer or other insulating material surrounding the conductive member  50 . As shown in  FIG. 2 , the front seal  52  surrounds a proximal end  64  of the pin  60 . The front seal  52  is a standard seal as is known in the industry, such as an IS-1 seal. The front seal  52  may have any other standard terminal configuration known in the art. 
   The lead body  54  of the second portion  46  is sized to allow cannulation of the coronary sinus and coronary veins. The lead body  54  includes an outer sheath  70  that substantially extends from a proximal end  72  of the lead body  54  to a distal end  74  of the lead body  54  and can be made of polyurethane tubing or any other material known in the art. The outer sheath  70  encapsulates a flexible conductive coil  76 . In one embodiment, the outer sheath  70  encapsulates one or more cables or both cables and a conductive coil  76 . In one embodiment, the conductive coil  76  may be coated with any biocompatible, polymeric material, such as, for example, ETFE, PTFE, silicone rubber, or polyurethane. In various embodiments the conductive coil  76  is made from any biocompatible material, such as stainless steel, MP35N, Platinum/Tantalum, and DFT. 
   A lumen  78  is located inside the lead body  54  and extends from the proximal end  72  to the distal end  74 . Upon assembly of the first portion  44  and the second portion  46 , the conductive member  50  extends through the lumen  78  from the proximal end  28  of the cardiac lead  24  to near the distal end  30  of the cardiac lead  24 . In one embodiment, the conductive member  50  extends beyond the distal end  30  and has a tip  80  serving as an electrode  31 . The conductive member  50  can be used convey sense electrical activity from the heart  25  or to convey electrical signals to the heart  25 , or both. Alternatively, the conductive member  50  may not extend beyond the distal end  30  of the cardiac lead  24 , but instead may couple to an electrode on the lead body  54  (see, for example,  FIGS. 11B and 11C .) In one embodiment, a spiral fixation shape is incorporated into the distal end  74  of the lead body  54 , which can facilitate fixation of the lead inside of the coronary vein. In another embodiment, fixation is accomplished using tines coupled to the distal end  74  of the lead body  54 . 
   The terminal connector  58 , as shown in  FIG. 2 , includes a tab  82  that is inserted into the proximal end  72  of the lead body  54 . The tab  82  of the terminal connector  58  is electrically connected to the conductive coil  76 . The rear seal  56  surrounds a portion of the conductive coil  76  that overlaps with the tab  82 . The surface electrode  32  is located at the distal end  30  of the cardiac lead  24 . The surface electrode  32  can be a terminal connector electrically connected to the conductive coil  76  or alternatively can be created by removing an annular portion of outer sheath  70 , thus exposing a portion of conductive coil  76 . The position of the surface electrode  32  along the cardiac lead  24  can vary. In one embodiment, the lead  24  includes more than one surface electrode  32 . 
     FIG. 3  shows a partial sectional view of the proximal end  72  of the lead body  54  and the first portion  44  of the cardiac lead  24 , in accordance with one embodiment of the present invention. As shown in  FIG. 3 , the first portion  44  includes the conductive member  50 , the connector assembly  51 , and the front seal  52 . The connector assembly  51  includes the pin  60 , which is adapted for insertion into the sleeve  62 . The sleeve  62  is generally shaped like a hollow cylinder and is adapted for insertion into and coupling with the terminal connector  58 . The sleeve may be formed, for example, for PEEK, tecothane, or other biocompatible polymers. In one embodiment, the sleeve  62  is adapted to snap fit into the terminal connector  58 . In another embodiment, the sleeve  62  is formed directly on the interior surface of the terminal connector  58 . In another embodiment, the sleeve  62  is formed directly on the pin  60 . 
   As shown in  FIG. 3 , the sleeve  62  includes a leading surface  84  which contacts a shoulder  86  of the terminal connector  58  when the sleeve  62  is inserted into the terminal connector  58 . The sleeve  62  also includes an inner surface  88  and an outer surface  90 . The outer surface  90  has protrusions  92 , which mate with indentations  94  on the terminal connector  58 . The protrusions  92  encircle the sleeve  62  and fit into the grooves comprising the indentations  94  on the terminal connector  58 . The protrusions  92  and indentations  94  could be of any configuration that effects mechanical coupling between the sleeve  62  and the terminal connector  58 . The inner surface  88  of the sleeve  62  has an angled surface  96 , which forms a triangular groove within the sleeve  62 . The inner surface  88  of the sleeve  62  also has indentations  98  adapted for mating with the pin  60 . The indentations  98  could be grooves or any other receptive feature as is known in the art. 
   The pin  60  has a generally cylindrical shape and has a pin proximal end  100 , a pin distal end  102 , a pin tip  104 , and pin protrusions  106 . As shown in  FIG. 3 , the pin distal end  102  is tapered. In an alternative embodiment, the pin distal end  102  need not be tapered. The pin distal end  102  is electrically and mechanically connected or coupled to the conductive member  50 . The pin protrusions  106  have an attaching end  108  and an engaging end  110  and are interposed between the pin tip  104  and the pin proximal end  100 . The attaching end  108  is resiliently attached to the pin  60  so that the pin protrusions  106  are compressed toward the pin  60  as the pin  60  is inserted into the sleeve  62  and expand outward into the indentations  98  upon reaching the indentations  98 , thereby locking the pin  60  into place in the sleeve  62 . The embodiment of  FIG. 3  shows two protrusions  106  but any number of protrusions could be used. In an alternative embodiment, pin protrusions  106  could be one or more solid protrusions encircling the pin  60 , or the pin protrusions  106  could be some other attachment feature as is known in the art, such as leaf springs. In one embodiment, the sleeve  62  (or terminal connector  58 ) supports a seal  111  near the proximal end. In this embodiment, the seal  111  functions to contact a leading portion of the front seal  52 , such that when the first portion  44  is inserted into the second portion  46 , the two portions form a sealed interface. 
     FIGS. 4A-4B  show partial sectional views of the interface between the pin  60  of the first portion  44  and the terminal connector  58  of the second portion  46 . In one embodiment, the conductive member  50  is fixed with respect to the pin  60 , such that the pin  60  and the conductive member  50  are inserted into the second portion  46  simultaneously. In another embodiment, the pin  60  is adapted for insertion over the conductive member  50 , after the conductive member  50  is properly positioned within the second portion  46 . As shown in  FIG. 4A , the pin  60  includes a lumen  112  extending along the longitudinal axis  114  of the pin  60 . The conductive member  50  is positioned in the lumen  112 . The pin  60  engages with the sleeve  62 , locking the pin  60  and the conductive member  50  into place. In the embodiment shown in  FIG. 4A , pin protrusions  106  are attached at the pin distal end  102 . In the alternative embodiment shown in  FIG. 4B , the pin protrusions  106  are attached at a location further from the pin tip  104 . 
     FIGS. 4C and 4D  show side views of the portion of  FIG. 4B  marked  4 C- 4 D.  FIGS. 4C and 4D  show the jaws  102  in further detail. As shown, as the jaws  102  close, they cut through the insulating sheath  61  thereby creating both a mechanical and an electrical connection between the pin  60  and the conductive member  50 . In the embodiment shown in  FIG. 4C , the jaws  102  include substantially flat edges  115  for cutting through the insulating sheath  61 . In another embodiment shown in  FIG. 4D , the jaws  128  have serrated edges  115 . In this embodiment, the pin tip  104  may be composed of 2, 3, 4, or more jaw members  102 . 
     FIGS. 5A-5B  show partial sectional views of the interface between the pin  60  of the first portion  44  and the terminal connector  58  of the second portion  46 , wherein the pin  60  is removably coupled to the sleeve  62 . As shown in  FIG. 5A , the pin protrusions  106  include a bend  116  having an angle  118 . The angle  118  is such that when the pin  60  is pulled out of the sleeve  62 , a contact area  120  acts against a top surface  122  of the protrusion  106  to compress the protrusion  106  toward the pin  60 , thereby releasing the pin  60  from the sleeve  62  and allowing removal of the pin  60  and repositioning of the conductive member  50 . In the embodiment shown in  FIG. 5A , the pin protrusions  106  are attached at the pin distal end  102 . In the alternative embodiment shown in  FIG. 5B , the pin protrusions  106  are attached at a position further from the pin tip  104 . 
     FIG. 6  shows a partial sectional view of an alternative embodiment of the present invention, wherein the conductive member  50  is removable from the pin  60 . As shown in  FIG. 6A , the pin  60  is threadably engagable with the sleeve  62 . In the embodiment shown in  FIG. 6A , the pin  60  has external threads  124  and the sleeve  62  has mating internal threads  126 . When the pin  60  is screwed into the sleeve  62 , a leading angled surface  96  of jaws  128  contact the angled surface  96 , which causes the jaws  128  to close on the conductive member  50 . 
     FIG. 7  shows a partial sectional view of yet another alternative embodiment of the present invention. As shown in  FIG. 7 , the pin  60  includes both threads  124  and protrusions  106 . The sleeve  62  includes the sleeve inner surface indentations  98  and threads  126 . In the embodiment shown in  FIG. 7 , the protrusions  106  are shaped in the form of a chamfer so that as the pin  60  is screwed into the sleeve  62 , the protrusions  106  mechanically engage with the sleeve inner surface indentations  98 , locking the pin  60  into place in sleeve  62 . In an alternative embodiment, the pin  60  and sleeve  62  include pin protrusions  106  and sleeve inner surface indentations  98  of the type shown in  FIGS. 3-5B . The location of the protrusions  106  and inner sleeve indentations  98  can vary along the longitudinal axis  114 . 
     FIG. 8  shows a partial sectional view of yet another alternative embodiment of the present invention, wherein the pin  60  and the sleeve  62  act to sever the conductive member  50  when the pin  60  is mechanically engaged with the sleeve  62 . As shown in  FIG. 8 , the pin  60  includes cutting edges  134  and a shoulder  136 . The sleeve  62  includes a protrusion  138 . The shoulder  136  and protrusions  138  are located at a distance along the longitudinal axis  114  such that when the shoulder  136  reaches the protrusions  138 , the protrusions  138  act against the shoulder  136 , causing the cutting edges  134  to compress, thereby severing the conductive member  50 . In the embodiment shown in  FIG. 8 , the protrusions  138  have an arcuate shape, but other shapes are within the scope of the present invention, including a chamfer encircling the inner surface  88  of the sleeve  62 . The number of protrusions  138  and cutting points  134  can also vary as needed. 
     FIGS. 9A-9B  show an alternative embodiment of the present invention wherein the jaws  128  include cutting points  134 , gripping points  140 , and a jaw indentation  142 . The cutting points could be made using any technique known in the art, including, for example, wire EDM. The pin  60  includes a leading surface  144  and the sleeve  62  includes a shoulder  146 . In this embodiment, as the pin  60  is advanced into the sleeve  62 , the angled surface  96  acts to compress the jaws  128  together. As the jaws  128  are compressed together, gripping points  140  retain the conductive member  50  in the jaws  128  and cutting points  134  sever the conductive member  50 . In one embodiment, as shown in  FIG. 9C , the jaws  128  act in conjunction with the sleeve  62  to constrain the cable or conductive member  50 , such that when it is gripped by gripping points  140  or cut at cutting points  134 , the cable does not flatten, which would impede this gripping or cutting action. 
   The conductive member  50  is forced into the jaw indentation  142  and can then be removed from the pin  60  in the direction shown by the arrow in  FIG. 9B . When the pin  60  is inserted into the sleeve  62 , the leading surface  144  contacts the sleeve shoulder  146  to stop the pin from advancing further into the sleeve  62 . In the embodiment shown in  FIGS. 9A-9B , pin protrusions  106  mechanically engage with sleeve inner surface indentations  98  to lock the pin  60  into place. Alternatively, the pin  60  and sleeve  62  could be threadably engaged as shown in  FIGS. 6A-6C , or engaged using threads and a snap fit as shown in  FIG. 7 . 
     FIGS. 10A-10C  show alternative embodiments of the jaw gripping mechanism. In  FIG. 10A , the jaws  128  have inner surfaces  148  having sinusoidal shapes and gripping points  140  that are sharp enough to cut through the insulating sheath  61  of the conductive member  50 . In  FIG. 10B , the inner surfaces  148  are substantially flat so as to better control the depth of the cut into the insulating sheath  61 . In the embodiment shown in  FIG. 10C , the inner surfaces  148  have a proximal end  150  and a distal end  152 . The proximal end  150  includes gripping points  140  that cut through the insulating sheath  61 . The distal end  152  includes curves  154  that act to hold the conductive member  50  into place without penetrating the insulating sheath  61 . 
     FIGS. 11A-11C  show alternative embodiments of the distal end of the cardiac lead  24 . In the embodiment shown in  FIG. 11A , the conductive member  50  extends beyond the distal end  30  of the lead body  54 . The conductive member  50  has a generally spherically-shaped tip  80 . The tip  80  can also be canted or biased to one side to improve contact with the coronary vein  26 . In this embodiment, the tip  80  of the conductive member  50  functions as the surface electrode  31 . In one embodiment, the lead body further includes a drug collar  155 . 
   In an alternative embodiment shown in  FIGS. 11B and 11C , the surface electrode  32  includes a first surface electrode  158  located near the distal end  30  of the cardiac lead  24  and a second surface electrode  159  located further from the distal end  30 . As shown in  FIG. 11C , the first surface electrode  158  includes recesses  160 , a proximal surface  162 , and a distal surface  164 . The proximal diameter  166  is slightly larger than the distal diameter  168  so that the conductive member  50  can pass through the proximal diameter  166  but not the distal diameter  168 . The distal diameter  168  is large enough that a guidewire (not shown) can pass through it. 
   As further shown in  FIG. 11C , the conductive member  50  includes a cable conductor  170  and tines  174 . As shown in  FIG. 11C , the tines  174  are resiliently attached to the tip  176  of the cable conductor  170 . When the conductive member  50  is inserted through the lumen  78  of the lead body  54  sufficiently far that the tines  174  reach the recesses  160 , the tines  174  expand outward into the recesses  160 , thereby electrically and mechanically attaching to the surface electrode  158 . Two tines  174  are shown in  FIG. 11B , but any number could be used as needed for retention properties. In this embodiment, the conductive member  50  can be used to electrically couple the first surface electrode  158  to the pin  60 . In other embodiments, any other configuration known in the art can be used to couple the distal end of the conductive member to either of the surface electrodes  158 ,  159 . In one embodiment, the conductive member  50  is fixed with respect to the lead body  54 , such that the conductive member  50  can be used as a stylet for delivering the lead body  54 . In one embodiment, the conductive member  50  is fixed rotationally, such that it can be used to apply torque for steering the lead body  54  during delivery. In one such embodiment, the conductive member  50  has a pre-formed shape to assist in delivery and cannulation. 
     FIG. 12  depicts an exemplary implantation process  200  for implanting the cardiac lead  24  into the human heart  25 . As shown, the second portion  46  of the cardiac lead  24  is advanced, using a stylet or over a guide wire, to the desired position in the coronary vein  26  (block  206 ). In one embodiment, the cardiac lead  24  is advanced through a previously-placed guide catheter extending through the vasculature to the coronary sinus. The stylet or guide wire is then removed from the lumen  78  of the second portion  46  (block  208 ). Next, the first portion  44  of the cardiac lead  24  is inserted into the lumen  78  and advanced to the desired position in the coronary vein  26  (block  210 ). The conductive member  50  is then advanced through a lumen in the first portion  44 . In one embodiment, the conductive member  50  is advanced to a position extending beyond the distal end of the lead body  54 , such that the tip  80  can act directly as a surface electrode  31  (see  FIG. 11A ). In another embodiment, the distal end of the conductive member  50  couples to a surface electrode  32  located on the lead body  54  (see  FIGS. 11B-11C ). The first portion  44  and the second portion  46  are then connected using the connector assembly  51  at the proximal end  28  of the cardiac lead  24  (block  212 ). If needed, any excess portion of the conductive member  50  can be removed (block  214 ). In an alternative embodiment, the connector assembly  51  is pre-affixed to the conductive member  50 , such that insertion of the conductive member  50  and coupling of the connector assembly  51  to the second portion  46  occur simultaneously. In yet another alternative method, the conductive member  50  can be used as a stylet to deliver the second part  46  of the cardiac lead  24 . 
   Although the present invention has been described with reference to exemplary embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.