US3416534A - Body organ electrode - Google Patents

Description

J. G. QUINN Dec. 17, 1968 BODY ORGAN ELECTRODE Filed April 11,

FIG. I

FIG. 2

INVENTOR JOSEPH e. QUINN MA.

ATTORNEY United States Patent 3,416,534 BODY ORGAN ELECTRODE Joseph G. Quinn, Milwaukee, Wis., assignor to General Electric Company, a corporation of New York Filed Apr. 11, 1966, Ser. No. 541,726 2 Claims. (Cl. 128-418) ABSTRACT OF THE DISCLOSURE screwed in.

This invention relates to an electrode for connecting a living organ to an electrical device. Notwithstanding its various uses, the invention will be described as an electrode for connecting an implantable or external electronic stimulator to the myocardium.

The new electrode is an improvement over the type that enables connecting to the myocardium without thoracic surgery. The electrode comprises a long, flexible, wire conductor that is wound as a rather tight helix, preferably, which is insulated, except at its end regions. The end region that is intended for penetrating the myocardium is bare and has its helical pitch increased so it can be screwed into the heart. The insulated conductor is adapted to pass axially through a tubular hypodermic or puncture needle. The needle may be pressed through a selected intercostal region adjacent the sternum or through the body below the rib cage and at an angle that is appropriate for having the needle tip contact the heart. When the heart is felt by the surgeon, the needle is advanced through the pericardium to the myocardium. of the conductor that protrudes from the body.

When temporary cardiac stimulation i indicated, the bare free end of the conductor may be connected to the The conductor is then inserted in the needle until it comes to a stop after which the conductor is twisted in order to screw the expanded helical end into the myocardium. The needle is then withdrawn by sliding it back over the end terminal of an external electronic cardiac stimulator. If the patient is to be ambulatory, as in the case with heart block patients who are to be stimulated wit-h an implanted electronic stimulator, the surgeon may make a superficial incision and lay the conductor in it subcutaneously. The bare free end is then connected with the terminal of an electronic stimulator power supply which may be implanted under the skin in the axillary region or in the abdominal region, the latter region being preferred when the electrode passes into the body below the rib cage.

Myocardial electrodes for percutaneous insertion through a hypodermic needle were known before the instant invention, but available types were not wholly satisfactory for either short or long term pacing because their conductive tips were inclined to fall out of the moving heart muscle and create emergency situations. The reason for this is that the conductor usually terminated in a straight pointed tip which has practically no holding power by itself. In addition, the straight tip minimized current interchange area between conductor and heart tissue and resulted in a high impedance connection. Another disadvantage of some prior art electrodes is that the tip had to enter the myocardium at a right angle 3,416,534 Patented Dec. 17, 1968 and, hence, the tip had to be fairly short lest it puncture the myocardium.

One object of the present invention is to overcome the last mentioned difficulties by providing an electrode that may be screwed into the myocardium so that a sound mechanical connection and a low impedance electrical connection may be developed immediately and which connection becomes more secure with passage of time as a result of fibrotic tissue developing and intermeshing with the helical tip of the conductor.

Other objects of the invention are to provide an elec trode that is durably insulated, but nevertheless, extremely flexible, that has a small diameter, that is simple in construction and that is easy to use. Achievement of these and other objects will appear from time-to-time through out the course of the ensuing specification.

A more detailed descripition of a preferred embodiment of the invention will now be set forth in reference to the drawing in which FIGURE 1 is a side view of a hollow hypodermic needle body with a part broken away to show how the new electrode is disposed therein;

FIGURE 2 is a fragmentary view of the new electrode conductor, shown enlarged, and partly in section, for exhibiting details of its construction; and

FIGURES 35 are schematic representations of a fragment of the chest cavity and heart in connection with which the new electrode assembly is illustrated in its various stages of application.

FIGURE 1 shows the body 10 of a tubular hypodermic needle which is provided at one end with an enlargement 11 that facilitates pressing the needle into the body in a well-known manner. The tip of the needle 12 is pointed and the needle bore 13 has the same calibre from end-to-end in this embodiment. A No. 15 thin wall hypodermic needle is used with a commercial embodiment of the new electrode which has the dimensions given below, but another embodiment contemplates use of a No. 13 needle.

The electrode conductor is generally designated by the reference numeral 14 in FIGURE 1. Basically, the electrode is a closely wound helix of fine corrosion-resistant wire. As seen in the broken away part of the needle 10 in FIGURE 1, the pitch of the helix is increased near its end 15 to facilitate screwing the conductor into tissue. In a practical case, the portion 15 with the enlarged or open pitch i 0.43 inch long and the pitch is about 0.05 inch. The outside diameter of the portion with the increased pitch is approximately 0.051 inch and this is the nominal inside diameter of needle 10.

From a point that is marked with the numeral 17 to FIGURE 1 to a point that is marked with the numeral 18, the conductor is insulated, except that beyond the latter point there is a region 19 which is uninsulated to facilitate making electrical connection to the terminal of an implantable stimulator power supply or the like, not shown.

One may see in FIGURE 2 that the outside diameter of the open pitch portion of the conductor 15 is greater than the outside diameter of the tightly wound helical portion 20, but that the diameter of the electrode 14 as a whole is uniform by reason of the small diameter portion being coated with an insulating material 21. The insulating material is preferably self-curing medical grade silicone rubber such as Dow Corning type 891. The insulating material fills the central space of interior 26 of the tightly wound helix 20 as well as the exterior. Experience shows that greater holding force is achieved where the outside diameter of the open pitch portion is greater, but the tolerable needle size imposes a practical limit on the diameter. In any case, fibrotic tissue forms ultimately about the helix that is embedded in the myocardium so that it is unlikely to fall out.

It may be observed in FIGURE 2 that the tip of the open pitch helix part 15 which screws into the myocardium is pointed as at 22 to facilitate turning the electrode into the tissue with greater ease. The free or uninsulated end 19 of the conductor in a commercial embodiment has a length of 0.43 inch and an outside diameter of 0.042 inch, the same as the outside diameter of the tightly wound helix portion. A commercial embodiment of the electrode employs No. 316 extra low carbon stainless steel wire having a diameter of 0.012 inch to make the helix. The pitch of the closely wound part is, of course, approximately equal to the wire diameter. In a typical case, the conductor is twelve inches long and is wound on a cylindrical mandrel 0.015 inch in diameter over its principal length and 0.026 inch in diameter for the part 15 with the enlarged pitch which has an outside diameter equal to the other part when its insulating coating is in place. In any case, of course, the overall outside diameter of the electrode will depend on the calibre of the needle with which it is to be used. The external insulation 21 and the insulation in the center of the helix may be deposited by extruding the helix with uncured, gelatinous silicone rubber simultaneously by methods which are well-known to skilled artisans.

Other insulating materials have also been used successfully, such as, for example, heat shrinkable Teflon which may be slipped over the helix as a tube and then subjected to a temperature of over 600 to effect shrinking. Silicone is preferred, however, because of its greater flexibility.

Of course, one may also make the helically wound conductor of wire that is insulated before winding, but

it is still advisable to fill the center with silicone rubber so that the assembly does not act as a tube and to avoid too much flexibility and kinking.

In FIGURES 35 use of the invention is illustrated. In FIGURE 3 the needle has been pressed through the thoracic wall 23 with the electrode 14 protruding from the exterior end of the needle. The tip of the needle has penetrated the pericardium 24 which is symbolized as a layer overlaying the myocardium 25.

In FIGURE 4, the effect of grasping the electrode 14 between the fingers of the operator and turning it to advance the open-ended helix into the myocardium tissue 25 is illustrated. In FIGURE 5, the needle 10 has been withdrawn by sliding it back over electrode 14 and the connection to the myocardium 25 by the open pitch helix 15 is completed. A little sag is usually allowed to occur in electrode 14 between the point of attachment to the heart and the place where the electrodes penetrate the thorax so that no restraint is placed on the heart when it moves while beating.

From the foregoing description, one may see that although surgical skills are required, the procedure may be carried out very rapidly and the electrode connected to a cardiac stimulator, not shown, so that many patients who would otherwise expire due to low heart rates that accompany heart block can now be given emergency lifesaving treatment by virtue of the ease with which an external stimulator may be connected. Moreover, the elec- Cir trode constituting the present invention which is installed under emergency conditions, may also be used subsequently to connect with a permanently implanted stimulator, if use is indicated by the condition of the patient.

In summary, there has been described a body organ electrode which makes a tenacious connection with an organ that is not directly accessible and which may be easily introduced through a hypodermic needle that is first inserted into the body. The electrode is characterized by its small diameter, high flexibility, durability, and unexpectedly high holding power. The electrical impedance between the electrode tip and the myocardium is low because of the inherently greater current interchange area of the open helix and because the tip can be introduced at an angle which increases the length of the current path and minimizes the likelihood of perforating the myocardium. Moreover, the fact that the helix screws in reduces trauma or tissue destruction in the vicinity of the connection. Although a specific embodiment of the invention has been described, such description is intended to be illustrative rather than limiting, for the invention may be variously embodied and is to be limited only by interpretation of the claims which follow.

It is claimed:

1. An electrode that is adapted for being screwed into an organ for making electrical connection between the organ and an electric stimulator comprising:

(a) a helically wound continuous wire conductor that has a major portion of its length formed in a relatively close helix and a short portion at at least one end formed as an open pitch helix and terminating in a sharp point,

(b) a flexible insulating coating of uniform diameter that surrounds and is substantially coextensive in length with the closely wound portion of the helix, the said open pitch end being adapted to screw into an organ by twisting the conductor,

(0) the total outside diameter of the insulation surrounding the tightly wound portion of the helix being substantially equal to the outside diameter of the open pitch uninsulated portion of the helix.

2. The invention set forth in claim 1 including in combination:

(a) a tubular needle means into which the conductor extends for admitting the conductor into the body,

(b) the said needle means having an inside diameter that is approximately equal to, but a little larger than, the outside diameter of both the open pitch helix portion and the insulated portion of the conductor.

References Cited UNITED STATES PATENTS 789,161 5/1905 Linn. 3,216,424 11/1965 Chardack 128-4l8 3,367,339 2/1968 Sessions 128-418 RICHARD A. GAUDET, Primary Examiner.

W. E. KAMM, Assistant Examiner.

U.S. Cl. X.R. 17474

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