Abstract:
A temporary cardiac pacing wire, or a similar device, includes a pair of flexible electrode wires extending conjointly from a distal end of the pacing wire to its proximal end, where two electrically conductive sections are located. The conductive sections are suitable for connection to a power source adapted to generate electrical signals for stimulating, pacing, sensing, monitoring or defibrillating the heart of a patient. One conductive section results from the distal end of a Keith-type needle that breaks away from the rest of the needle. The other conductive section is arranged at the free end of a third electrode wire which is movable independently of the other two electrode wires, thereby permitting its connection to the power source in a plug-like fashion.

Description:
FIELD OF THE INVENTION 
     The present invention relates to electrical connectors for cardiac devices and, more particularly, to temporary cardiac pacing wires that are adapted for use with apparatus that generate electrical signals suitable for stimulating, pacing, sensing, monitoring or defibrillating the heart. 
     BACKGROUND OF THE INVENTION 
     Devices to stimulate or regulate cardiac function have been known and used for decades. They involve a power source (pacemaker) and one or more surgical electrodes to attach the source to the heart. They are generally of two types. 
     Implantable pacers are intended for long-term use and, as the name suggests, are entirely implanted in the body. The other type is intended for temporary use. The temporary pacemaker is located outside the body and is connected to the heart by a surgical electrode called a “temporary pacing wire.” Although surgical electrodes are used for preparing electrocardiograms and other applications, for the sake of brevity, the description that follows is focused on temporary pacing wires. 
     In general, such wires are constructed of a number of fine, stainless steel wires braided or twisted together to form a single, flexible, multi-strand electrode wire. The major portion of the wire is electrically insulated with a polyethylene, polytetrafluoroethylene, silicon, nylon, or another non-conducting coating, with a short length of wire at either end left uninsulated. To the distal uninsulated end of the electrode wire there is attached, by swaging or other means, a fine curved needle for piercing the heart tissue to place the uninsulated end of the electrode in the myocardium. At the proximal end of the electrode wire, a straight (e.g., Keith-type) cutting needle is attached for piercing the thoracic wall to lead the electrode to an outer point for connection with the pacemaker. Once that has been accomplished, the needle, or its sharp-pointed end, is clipped or broken off and the proximal end of the electrode is readied for attachment to the pacemaker as required to stimulate or regulate the beating of the heart. A single setup involves two electrodes, i.e., two temporary pacing wires. During the time that the temporary pacing wire is performing its function, the unisulated end of the electrode must remain anchored in the myocardium. The anchorage must be secure, lest the continually beating heart cause the wire to be expelled from the myocardium. When the need for the pacing wire has passed, it is necessary to remove from the body the wire that runs from the external pacemaker to the myocardium. 
     The process of preparing the proximal ends of the pacing wires (electrodes) to the pacemaker requires numerous steps and is time consuming. Not only do the proximal ends of the pacing wires require removal from the Keith-like needles, but separate steps are required to make them suitably adapted for attachment to electrodes (terminals) within the pacemaker. 
     DESCRIPTION OF THE RELATED ARTS 
     U.S. Pat. No. 4,693,258, issued on Sep. 15, 1987 to Osypka et al., discloses an electrode connector assembly that can be used to electrically connect the proximal end of a pacing wire (with insulation removed) to the socket of a pacing or monitoring instrument. This approach is useful but requires many small parts to be assembled. This may prove to be difficult and time consuming to work with in the operating room environment. Also, multistrand wires have a tendency to fray which adds to difficulties. Additionally, small parts are prone to be easily lost. 
     U.S. Pat. No. 4,633,880, issued on Jan. 6, 1987 to Osypka et al., discloses an implantable bipolar electrode assembly where the two distal ends of the wire are received in an electrically conductive sleeve (pole). One wire is in electrical contact with the sleeve and the second wire passes through the sleeve. The distal end of the second wire is stripped of insulation to provide electrical contact with heart tissue. The stripped section is configured to introduce mechanical resistance to its removal from heart tissue. Although this electrode assembly is effective in delivering a bipolar signal to the heart, it is not intended for use as a direct electrical connection with a pacemaker. 
     U.S. Pat. No. 5,792,217, issued on Aug. 11, 1998 to Camps et al., discloses an arrangement in which the proximal ends of two pacing wires can be simultaneously broken away from a Keith-type needle. Affixed to the proximal end of each wire is an electrical connector that is suitably dimensioned to connect to a pacing or monitoring instrument. This arrangement requires complex manufacturing processes to fabricate. Because the Keith-type needle accommodates two electrical connectors in a side-by-side fashion, the needle is approximately twice as large as those typically used. The larger needle can cause undesirable tissue trauma. 
     In view of the foregoing, there is a need for a simple, efficient and reliable mechanism for connecting the proximal ends of bipolar temporary pacing wires to a pacing or monitoring instrument. The mechanism should have few parts, be easy to manufacture and be consistent with minimal tissue trauma to the patient. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of this invention is to provide a novel and improved surgical electrical connector that can be connected to a medical instrument in a simple and time-saving manner. 
     Another objective of the invention is to provide an electrical connection that can be electrically connected directly to the socket of a pacing or monitoring instrument. 
     A further object of the invention is to provide an assembly requiring minimal tissue trauma during installation and simultaneously allowing for two electrical connections to be established with a pacing or monitoring instrument. 
     An additional object of the invention is to provide an electrical connector with partially insulated ends. 
     Still another object of the invention is to provide an electrical connector assembly that is smaller in diameter than the Keith-type needle used to guide the connector to the outside of the body. 
     With the foregoing objects in mind, the present invention relates to an electrical connector assembly in which a branch-like conductive lead is equipped with a connector in such a manner that the connector can be plugged into a socket-like terminal of a power source adapted to generate electrical signals. The present invention is especially suited for use in conjunction with a temporary cardiac pacing wire which includes a pair of electrode wires extending conjointly from a distal end of the pacing wire to its opposite (i.e., proximal) end. One of the electrode wires is mechanically and electrically connected to the distal end of a Keith-type needle that breaks away from the needle, thereby forming another conductive lead adapted for connection to another terminal of the power source in a plug-like fashion. The branch-like conductive lead is mechanically and electrically connected to the other electrode wire such that the branch-like conductive lead is freely movable independently of the pair of electrode wires. In this embodiment, the power source would be a pacing or monitoring instrument which generates electrical signals for stimulating, pacing, sensing, monitoring or defibrillating the heart of a patient. To facilitate its connection to the pacing or monitoring instrument in a plug-like fashion, the connector of the branch-like conductive lead may have a length which is more than ten times the diameter of the Keith-type needle, while having a maximum lateral dimension (e.g., a diameter in the case of a circular cross section) which is smaller than or equal to the diameter of the Keith-type needle. 
     The invention has the advantage of ease of use without requiring additional pin-plugs or other assemblies. Also, the invention allows the use of needles, wires and connectors sized smaller than or equal to the size of existing Keith-type needles. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is made to the following detailed description of an exemplary embodiment considered in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a schematic illustration of a first embodiment of the invention showing a bipolar temporary pacing wire including a distal anchoring portion; 
     FIG. 1A is a cross-sectional view of the embodiment of FIG. 1 taken along section line I—I and looking in the direction of the arrows; 
     FIG. 1B is a cross-sectional view of the embodiment of FIG. 1 taken along section line II—II and looking in the direction of the arrows; 
     FIG. 2 is a schematic illustration of the embodiment of FIG. 1 viewed from a different perspective; 
     FIG. 3 is a schematic, partially cross-sectioned illustration of the embodiment of FIGS. 1 and 2 inserted into a pacemaker; 
     FIG. 4 is a schematic, partially cross-sectional illustration of a second embodiment of the invention inserted into a pacemaker; and 
     FIG. 4A is a cross-sectional view of the embodiment of FIG. 4 taken along section line III—III and looking in the direction of the arrows. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Although the present invention is applicable to many different types of cardiac devices, it is especially suitable for use in conjunction with a bipolar temporary cardiac pacing wire. Accordingly, the present invention will be described below in connection with such a pacing wire. 
     As used herein, the term “distal” shall mean that portion of the pacing wire or element thereof which is remote from a source of electric signals located external to the patient&#39;s body. Conversely, the term “proximal” shall mean that portion of the pacing wire or element thereof which is in close proximity to the external source of electrical signals. 
     Referring to FIG. 1, a bipolar temporary cardiac pacing wire  10  includes a Keith-type breakaway needle  12  arranged at a proximal end of the pacing wire  10  and a curved needle  14  arranged at a distal end of the pacing wire  10 , which also includes any type of suitable anchor  16  such as the one disclosed in U.S. patent application Ser. No. 09/307,537, which was filed on May 7, 1999 by the assignee of the present application and which is incorporated herein by reference. The Keith-type needle  12 , such as the one disclosed in U.S. Pat. No. 4,010,756 issued on Mar. 8, 1977 to DuMont et al., has a distal section  12   a  and a proximal section  12   b , which is pointed for piercing the thoracic wall to lead the proximal end of the pacing wire  10  outside the chest cavity of a patient in accordance with a medical procedure well known in this field. The curved needle  14  is adapted to pierce the heart tissue and to attach the anchor  16  to the heart in accordance with another well-known medical procedure. 
     A pair of insulated, electrically conductive electrode wires  18 ,  20  extends between the distal and proximal ends of the pacing wire  10 . The electrode wires  18 ,  20  are of the “lamp cord” type (i.e., they are arranged in a side-by-side fashion as shown in FIG.  1 A), each wire having a braided, multi-strand core of stainless steel and a surrounding layer of insulation made from polyethylene. Alternatively, the core of each wire could have a twisted construction with a surrounding layer of insulation made from polyethylene or any other suitable electric non-conducting material, such as silicon, polytetrafluoroethylene, or nylon. 
     At the distal end of the pacing wire  10  there are two electrodes  22 ,  24 . The electrode  22  is electrically and mechanically connected to the electrode wire  18 , but only mechanically connected to the electrode wire  20 , which passes through the sleeve-like electrode  22  and is mechanically and electrically connected to the electrode  24 . The electrodes  22 ,  24  have a conventional construction and are adapted to transmit electrical signals from one to the other for the purpose of stimulating, pacing, sensing, monitoring, or defibrillating the heart. 
     An elongated connector  26  and a bushing-like connector  28  are located at the proximal end of the pacing wire  10 . The connector  26  is mechanically and electrically connected to a free end of a third electrode wire  30 , which has a construction similar to that of the electrode wires  18 ,  20 . The other end of the electrode wire  30  is mechanically connected to the connector  28 , which extends circumferentially about all three of the electrode wires  18 ,  20 ,  30  (see FIG.  2 ). While the connectors  26 ,  28  have a generally circular cross-sectional shape (see, for example, the corresponding connectors  126 ,  128  in FIG.  4 A), they could have other cross-sectional shapes, such as oval, square, rectangular, etc. 
     Within the connector  28 , the electrode wire  30  is electrically connected to the electrode wire  20 , but not to the electrode wire  18  or to the connector  28 , which can therefore be made from an electrically non-conductive material. If the connector  28  is used to electrically connect the electrode wires  20 ,  30 , then it would have to be made from suitable electrically conductive material, in which case electrical insulation could be applied to avoid shorting. The majority of the electrode wire  30  is not attached to either of the electrode wires  18 ,  20 ; and it is, therefore, free for movement independently of the rest of the pacing wire  10  (see FIG.  2 ). 
     The electrode wire  18  is only mechanically connected to the connector  28 . In fact, the wire electrode  18  is electrically insulated from the electrode wires  20 ,  30 , as well as the connector  28 . Thus, the electrode wire  18  is only electrically connected to the electrode  22  (at one end of the wire  18 ) and to the distal section  12   a  of the Keith-type needle  12  (at an opposite end of the wire  18 ). 
     Referring now to FIG. 3, the pacing wire  10  is shown adapted for use in connection with a pacemaker  32  which has a pair of sockets  34 ,  36 . As is typical of pacemakers like the pacemaker  32 , a pair of spring-loaded clamps  38 ,  40  is mounted in the socket  34 , one of which carries an electrical charge (either positive or negative) and the other of which is neutral (it does not carry either a positive charge or a negative charge). In a similar and typical fashion, a pair of spring-loaded clamps  42 ,  44  is mounted in the socket  36 , one of which is neutral and the other of which carries an electrical charge opposite the charged clamp in the socket  34  (e.g., if the charged clamp in the socket  34  carries a negative charge, then the charged clamp in the socket  36  carries a positive charge, and vice versa). Alternatively, the pacemaker  32  could be the type (e.g., a Medtronic Model No. 5375) in which all of the clamps (i.e., the clamps  38 ,  40  of the socket  34  and the clamps  42 ,  44  of the socket  36 ) carry an electric charge. 
     In order to make an electrical connection within the socket  34  of the pacemaker  32 , the Keith-type needle  12  is severed intermediate to its ends and the distal section  12   a  is inserted into the socket  34 , while the proximal end  12   b  is discarded. Inside the socket  34 , the distal section  12   a  is gripped between the clamps  38 ,  40  which have concave-shaped gripping surfaces so as to make good electrical and/or mechanical contact with the cylindrically-shaped distal section  12   a  and hence the electrode wire  18 . Because the distal section  12   a  is made entirely of an electrically conductive material, such as stainless steel, electric-conducting contact within the socket  34  is ensured, regardless of which of the clamps  38 ,  40  is charged and regardless of how the distal section  12   a  is oriented relative to the charged clamp. 
     In order to make an electrical connection within the socket  36  of the pacemaker  32 , the connector  26  is simply inserted, in a plug-like fashion, into the socket  36 , where it is gripped between the clamps  42 ,  44  which have concave-shaped gripping surfaces to ensure good electrical and/or mechanical contact with the cylindrically-shaped connector  26  and hence the electrode wire  30 . Because the connector  26  is cylindrical and is made from an electrically conductive material, such as stainless steel, electric-conducting contact within the socket  36  is ensured, regardless of which of the clamps  42 ,  44  is charged and regardless of how the connector  26  is oriented relative to the charged clamp. The electrode wire  30  is long enough and flexible enough to form a loop  46  in the segment extending from the connector  26  to the connector  28 , where the electrode wire  30  is electrically connected to the electrode wire  20 . 
     While the actual length of the connector  26  needs only be sufficient to assure secure insertion into the socket  36  of the pacemaker  32 , preferably this length is about ten times or greater than ten times the diameter of the Keith-type needle  12 . It is also preferable that the connector  26  has a diameter which is smaller than or equal to that of the Keith-type needle  12 . If the connector  26  does not have a circular cross-sectional shape, then its maximum lateral dimension would preferably be smaller than or equal to the diameter of the Keith-type needle  12 . The diameter or maximum lateral dimension of the connector  26  could, however, be larger than the diameter of the Keith-type needle  12 . 
     The connector  26  is fabricated from a solid piece of stainless steel wire which is drilled from its back side so as to form a blind hole. After inserting an uninsulated end of the electrode wire  30  into the blind hole, the connector  26  is mechanically and electrically attached to the electrode wire  30  by a swaging operation. 
     If the connector  28  is made from an electric insulating material, such as polypropylene or polyethylene, it can be applied to the electrode wires  18 ,  20 ,  30  by any conventional process. If the connector  28  is made from an electric conducting material, such as stainless steel, it would be swaged to the electrode wires  18 ,  20 ,  30  and then coated with a layer of insulation. 
     What follows is a description of an alternate embodiment of the present invention. In describing this embodiment, elements corresponding to elements described above in connection with the embodiment of FIGS. 1-3 will be described by corresponding reference numerals increased by one hundred. The alternate embodiment is constructed and operates in the same manner as the embodiment of FIGS. 1-3, unless otherwise specified. 
     In the embodiment of FIGS. 4 and 4A, the electrode wires  118 ,  120  have a coaxial construction (see FIG.  4 A). Except for the size and shape of the connector  128 , the other components of the pacing wire  110  are essentially the same as their counterparts in the embodiment of FIGS. 1-3. To form the desired electrical connection between the electrode wire  120  and the electrode wire  130 , insulation is removed from portions of both of the wires and the exposed electric conducting cores are then subjected to a swaging operation, resulting in the assembly illustrated in FIG.  4 A. 
     It will be understood that the embodiments described herein are merely exemplary and that a person skilled in the art may make many variations and modifications without departing from the spirit and scope of the invention. All such variations and modifications are intended to be included within the scope of the invention as defined in the appended claims.