Abstract:
A temporary cardiac pacing wire, or a similar device, includes an electrically conductive lead which is folded over on itself so as to be adapted for connection to a pacing or monitoring apparatus. In the case of a bipolar temporary cardiac pacing wire, flexible wires are employed having two elongated conductive sections at a proximal end. The conductive sections are suitable for connecting 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. This section is suitable for directly connecting to the power source. The other conductive section is suitable for connecting to the power source when folded over on itself.

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 5 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 uninsulated 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 ART 
     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 timesaving manner. 
     Another objective of the invention is to provide an electrical connector 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 conductive lead adapted for connection to a source of electrical signals is folded over on itself. The present invention is especially suited for use in conjunction with a temporary cardiac pacing wire which includes an electrically conductive flexible wire having two elongated conductive sections at its proximal end. The conductive sections can be plugged a pair of socket-like terminals of a pacing or monitoring instrument which generates 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 needle. This section can be plugged directly into one of the socket-like terminals of the pacing or monitoring instrument. The other conductive section is suitable for connecting to the other socket-like terminal when folded over on itself, or an adjacent insulated portion of wire, to provide dimensional thickness necessary for an electrically secure connection. To facilitate its connection to the pacing or monitoring instrument in a plug-like fashion, this section 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 various exemplary embodiments 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 first embodiment taken along section line I—I and looking in the direction of the arrows; 
     FIG. 1B is a cross-sectional view of the first embodiment taken along section line II—II and looking in the direction of the arrows; 
     FIG. 2 is a schematic, partially cross-sectioned illustration of the first embodiment inserted into a pacemaker; 
     FIG. 3 is a schematic, partially cross-sectioned illustration of a second embodiment of the invention inserted into a pacemaker; 
     FIG. 4 is a schematic, partially cross-sectioned illustration of a third embodiment of the invention inserted into a pacemaker; 
     FIG. 5 is a schematic illustration of a fourth embodiment of the invention showing a bipolar temporary pacing wire including a distal anchoring portion; 
     FIG. 6 is a schematic, partially cross-sectioned illustration of the fourth embodiment inserted into a pacemaker; 
     FIG. 7 is a schematic, partially cross-sectioned illustration of a fifth embodiment of the invention inserted into a pacemaker; and 
     FIG. 7A is a cross-sectional view of the fifth embodiment 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. 
     At the proximal end of the pacing wire  10  there are two connectors  26 ,  28 . The connector  26  is mechanically and electrically connected to the electrode wire  20 , but only mechanically connected to the electrode wire  18 , which passes through the elongated, sleeve-like connector  26  and which is mechanically and electrically connected to the Keith-type needle  12  in a conventionally manner. The other elongated, sleeve-like connector  28  is positioned on the electrode wire  18  intermediate to the connector  26  and the Keith-type needle  12 . Unlike the connector  26 , which is electrically connected to the electrode wire  20 , the connector  28  does not have to be electrically connected to either of the electrode wires  18 ,  20 . However, the connector  28  may be electrically connected to the electrode wire  20 , which could also be electrically connected to both of the connectors  26 ,  28 . Each of the connectors  26 ,  28  extends circumferentially about the electrode wire  18  (see, for example, FIG. 1B) and is made from suitable electrically conductive material, such as stainless steel, for a purpose to be described hereinafter. While the connectors  26 ,  28  have a generally circular cross-sectional shape (as shown, for example, in FIG.  1 B), they could have other cross-sectional shapes, such as oval, square, rectangular, etc. 
     Referring now to FIG. 2, the pacing wire  10  is shown adapted for use in connection with a pacemaker  30  having a pair of sockets  32 ,  34 . As is typical of pacemakers like the pacemaker  30 , a pair of spring-loaded clamps  36 ,  38  is mounted in the socket  32 , 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  40 ,  42  is mounted in the socket  34 , one of which is neutral and the other of which carries an electrical charge opposite the charged clamp in the socket  32  (e.g., if the charged clamp in the socket  32  carries a negative charge, then the charged clamp in the socket  34  carries a positive charge, and vice versa). 
     In order to make an electrical connection within the socket  32  of the pacemaker  30 , the Keith-type needle  12  is severed intermediate to its ends and the distal section  12   a  is inserted into the socket  32 , while the proximal end  12   b  is discarded. Inside the socket  32 , the distal section  12   a  is gripped between the clamps  36 ,  38  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 electric-conducting material, such as stainless steel, electric-conducting contact within the socket  32  is ensured, regardless of which of the clamps  36 ,  38  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  34  of the pacemaker  30 , the electrode wire  18  is first folded over onto itself such that the connectors  26 ,  28  are arranged in an abutting, juxtaposed relationship with respect to each other (i.e., they extend conjointly in parallel directions along their lengths). The folded portion containing the side-by-side connectors  26 ,  28  is then inserted, in a plug-like fashion, into the socket  34 , where it is gripped between the clamps  40 ,  42  with the connector  26  in electric-conducting contact with the clamp  40  and the connector  28  in mechanical, but not electrical, contact with the clamp  42 . To ensure good electrical and/or mechanical contact with the cylindrically-shaped connectors  26 ,  28 , the clamps  40 ,  42  have concave gripping surfaces. Because the connectors  26 ,  28  are in electric-conducting contact with each other, it does not matter which of the clamps  40 ,  42  is charged. More particularly, if, on the other hand, the clamp  40  is charged, then electric signals will flow from the pacemaker  30  to the electrode wire  20  via the clamp  40  and the connector  26 . If, on the other hand, the clamp  42  is charged, then electric signals will flow from the pacemaker  30  to the electrode wire  20  via the clamp  42 , the connector  28  and the connector  26 . 
     Still referring to FIG. 2, the electrode wire  18  is flexible enough to form a loop  44  in the segment between the connector  28  and the distal section  12   a  of the Keith-type needle. In addition, the electrode wire  18  has sufficient flexibility to form a loop  46  in the segment between the connectors  26 ,  28 . The loop  46  is small enough so as not to inhibit the folded section of the electrode wire (i.e., the plug-like section with the side-by-side connectors  26 ,  28 ) from being inserted into the socket  34 . When arranged in the side-by-side manner depicted in FIG. 2, the cumulative size of the connectors  26 ,  28  is sufficiently large to avoid a poor (i.e., loose) grip by the clamps  40 ,  42 , thereby promoting a good electrical connection between the pacemaker  30  and the electrode wire  20 . 
     While the actual length of each of the connectors  26 ,  28  needs only be sufficient to assure secure inserted into the socket  34  of the pacemaker  30 , 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 each of the connectors  26 ,  28  has a diameter which is smaller than or equal to that of the Keith-type needle  12 . If the connectors  26 ,  28  do not have a circular cross-sectional shape, then their maximum lateral dimension would be smaller than or equal to the diameter of the Keith-type needle  12 . 
     To fabricate the connector  26 , a 300 series stainless steel tube (Type 304 Stainless Steel Hypodermic Needle Tubing Catalog No. T19XXTW available from Popper &amp; Sons, Inc., New Hyde Park, N.Y.) of 0.019″, 0.037″ inside diameter was used. The proximal end of the tube was reduced in diameter using a rotating Torrington swaging press (MIN 9194, made by Torrington Swager-Vaill End Forming Machinery Inc., Waterbury, Conn.), while the distal end was left as its original diameter. The ends of the electrode wires  18 ,  20  were separated for a length sufficient to allow for the electrode wire  18  to extend on for attachment to the distal section  12   a  of the Keith-type needle  12 . The electrode wire  20  was cut and the insulation removed from a small length of its end. Both of the electrode wires  18 ,  20  were then inserted into the distal opening (i.e., the larger one) of the swaged tube until the uninsulated end of the electrode wire  20  was completely inside the distal opening of the tube. The end of the tube containing the distal opening was then swaged to make a secure electrical connection between the uninsulated end of the electrode wire  20  and the tube. While the swaging operation was carried out using a Torrington swaging press, a multi-collet vice could also be used to achieve a similar result. 
     The connector  28  was fabricated in a similar manner. More particularly, the electrode wire  18  was placed in a 0.019″ inside diameter  300  stainless steel tubing (Popper &amp; Sons, Inc.). The electrode wire  18  and the tubing wire then placed in a Torrington swaging press and swaged until the diameter of the tubing was reduced sufficiently to assure a secure circumferential fit around the electrode wire  18  without compromising the wire&#39;s insulation. 
     What follows is a description of various alternate embodiments of the present invention. In describing these embodiment, elements corresponding to elements described above in connection with the embodiment of FIGS. 1 and 2 will be described by corresponding reference numerals increased by one hundred, two hundred, three hundred and four hundred, respectively. The alternate embodiments are constructed and operate in the same manner as the embodiment of FIGS. 1 and 2, unless otherwise specified. 
     With reference to FIG. 3, the distal section  112   a  of a severed Keith-type needle has an end  148  which is exposed in that it extends outwardly from the socket  132  of the pacemaker  130 . Similarly, the connectors  126 , 128  has ends  150 , 152 , respectively, which are exposed in that they extend outwardly from the socket  134  of the pacemaker  130 . In order to prevent shorting or shocking problems, the exposed end  148  of the distal section  112   a  is provided with electric insulation  154 , while the exposed ends  150 , 152  of the connectors  126 ,  128  are also provided with electric insulation  156 ,  158 , respectively. 
     Referring now to FIG. 4, the socket  234  of the pacemaker  230  (such as a Medtronic Model No. 5375) houses the clamps  240 ,  242 , both of which carry an electric charge. In this embodiment, unlike the embodiment of FIGS. 1 and 2, the connector  226  can receive electric signals from either of the clamps  240 ,  242 , thereby making the connector  28  shown in FIGS. 1 and 2 expendable. Thus, although the electrode wire  218  still has a folded, plug-like portion, the connector  226  simply extends alongside the insulation on an abutting section of the electrode wire  218 . As depicted in FIG. 4, electric signals would be transmitted from the pacemaker  230  to the electrode wire  220  via the clamp  240  and the connector  226 . However, electric signals from the pacemaker  230  could also be transmitted to the electrode wire  220  if the connector  226  were in contact with the clamp  242 , rather than the clamp  240 . 
     The embodiment of FIGS. 5 and 6 is especially useful with Keith-type needles having a diameter that is too small to be securely gripped by the clamps of a pacemaker like the Medtronic Model No. 5375. In this embodiment, the electrode wire  318  has a third sleeve-like connector  360 , in addition to the connectors  326 ,  328 . In order to make an electrical connection in the socket  332  of the pacemaker  330 , the distal section  312   a  of a severed Keith-type needle is folded over onto the connector  360  in much the same way that the connectors  326 ,  328  are folded over onto each other, thereby forming a loop  362  in the segment of the electrode wire  318  between the distal section  312   a  and the connector  360 . Like the side-by-side connectors  326 ,  328  which are inserted together into the socket  334 , the distal section  312   a  and the connector  360  are inserted together, in plug-like fashion, into the socket  332 , the loop  362  being small enough so as not to inhibit such insertion. Once they have been fully inserted into the socket  332 , the distal section  312   a  makes electrical contact with the clamp  338 , while the connector  360  makes electrical contact with the clamp  336 . Of course, this arrangement could be reversed, whereby the distal section  312   a  would make electrical contact with the clamp  336 , while the connector  360  would make electrical contact with the clamp  338 . It should be noted that the connector  360  may or may not be electrically connected to the electrode wire  318  to which it is mechanically attached about the circumference thereof. 
     In the embodiment of FIGS. 7 and 7A, the electrode wires  418 ,  420  have a coaxial construction (see FIG.  7 A). Except for the sizes and shapes of the connectors  426 ,  428 , the other components of the pacing wire  410  are essentially the same as their counterparts in the embodiment of FIG.  2 . 
     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.