US3348548A - Implantable electrode with stiffening stylet - Google Patents

Description

@et 24, 1967 W. M. CHARDACK 3,348,548

IMPLANTABLE ELECTRODE WITH STIFFENING STYLET 2 Sheets-Sheet 22 Filed April 26, 1965 HUUHH HUI HIHIHIHHIHHIHHI HH INVENTOR Zz/Zcmz 772 CUPCZQ el? Qbw/V/ United States Patent O 3,348,548 IMPLAN'IABLE ELECTRUDE WITH STIFFENING STYLET William M. Chardack, 144 Ivyhurst Road, Buffalo, NY. 14226 Filed Apr. 26, 1965, Ser. No. 450,910 9 Claims. (Cl. 12S-418) This invention relates to a new and useful electrode especially adapted for implantation within the human body.

In certain cases of heart disease the impulses which normally elicit contraction of the cardiac ventricle are blocked. This leads to an abnormally low heart rate severely restricting the patients activities. Episodes of complete arrest occur in this condition leading to loss of consciousness which may terminate fatally. In some patients, the condition cannot be controlled short of electrical stimulation of the heart. A number of devices, known as Pacemakers have been developed for this purpose. They provide a suitable stimulating current pulse. Some of these devices are external, some are suitable for complete implantation within the body, and some are partly external and operate by induction through the intact skin through a subcutaneously buried coil. In most methods, the impulse ultimately travels to the heart muscle by an electrode at its leads, either from an external Pacemaker through the skin and deeper tissue to the heart muscle or from a subcutaneously implanted Pacemaker or an induction coil to the heart.

The provision of an electrode suitable for implanting in the heart muscle presents a severe problem, because of the varied motions which must be accompanied. The primary requirement of such an electrode, and connecting lead, are that they be flex-resistant to a high degree. That is to say, they must be capable of 'withstanding constantly, rapidly repeatedl flexing over a long period of time. For example, if the heart is stimulated once each second, there will be 60 flexing actions each minute, or more than 30 million flexing actions each year. The conductor and its insulation must be capable of withstanding repeated lateral and axial flexing on this order, without failureproducing fatigue. In addition, they must be able to withstand momentary elongation, such as produced by movement of the chest cavity during respiration, and by body motion as when bending, stretching and the like, as well as by motion of the heart. Also, when implanted in a youth whose body size will increase, the electrode and lead must be capable of accommodating such growth.

A Pacemaker electrode can be inserted through a vein and come to lie on contact with the inner lining of the heart. This is a desirable technique, because it avoids opening the chest cavity and can be performed under local anesthesia. As a result, it is particularly valuable for patients in whom a thoracotomy is contraindicated or carries a prohibitive risk.

However, a further problem arises where this technique is used, because an electrode having the requisite flexibility enabling it to withstand constantly, rapidly repeated flexing over a long period of time is too flexible to lbe advanced through the vein and directed into the appropriate position in the heart.

Accordingly, a primary object of my invention is to provide an electrode 'which is capable of withstanding the above-designated forces over a period of years, and which also is adapted for insertion into the heart through a vein.

In one aspect thereof, an electrode constructed in accordance with my invention is characterized by the provision of electrical conductors all of closely coiled construction enclosed within a sleeve of electrically insulating material, the conductors extending lengthwise of the sleeve and beingrinsulated from each other, and a stylet also extending lengthwise of the sleeve, the stylet providing rigidly enabling insertion of the electrode through a vein and being removable from the electrode ot restore optimal flex life thereto.

The foregoing and other objects, advantages and characterizing features of an electrode of my invention will become clearly apparent from the ensuing detailed description of two illustrative embodiments thereof, taken together with the accompanying drawings depicting the same wherein like reference numerals denote like parts throughout the various views and wherein:

FIG. 1 is a view of one form of electrode of my invention, showing a stylet in place therein;

FIG. 2 is a longitudinal seectional view thereof, on an enlarged scale, through the terminal end of the electrode;

FIG. 3 is a View partly in side elevation and partly in longitudinal section of the contact end portion of the electrode;

FIG. 4 is a longitudinal sectional view through the contact end of the electrode, on a further enlarged scale;

FIGS. 5 and 6 are transverse sectional views on a still further enlarged scale, taken about on lines 5-5 and 6 6, respectively, of FIG. 3;

FIG. 7 is a fragmentary side elevational view of the electrode, on the scale of FIG. 2 and with the stylet partly removed;

FIG. 8 is a view, partly in plan and partly in longitudinal section, showing the terminal end of another form of electrode of my invention; and

FIG. 9 is avtransverse sectional view thereof, on an enlarged scale, taken about on line 9-9 of FIG. 8.

Referring now to the embodiment of FIGS. 1 7, there is shown an electrode of my invention comprising an elongated lead portion l, a contact end portion 2 and a terminal end portion 3. The electrode comprises a pair of closely wound, coiled conductors 4, 5 each in the form of a spring spirally wound about and along the axis of the conductor. The spring coils 4, 5 travel in separate lumens ofa jacket or sleeve 6 of electrically insulating material.

Each conductor 4, 5 is formed of electrically conductive material offering low electrical resistance and also resistant to corrosion by body fluids. Stainless steel is an example of a suitable material. Sleeve 6 is formed of an electrically insulating material, and preferably a silicone rubber such as medical grade Silastic available from Dow Corning Corporation. This material is additionally suitable because it is inert and well tolerated by body tissue.

Pins 7 of stainless steel or other suitable material are` inserted into the open lumen of the conductor coils 4 and 5, at the contact ends thereof, and these coil ends then are welded to electrode contacts 8 and 9. These contacts must be electrically conductive and resistant to corrosion by body fluids, and I have found platinum to be especially suitable. Contact 8 comprises a ring encircling both coils 4 and 5, and the contact end of sleeve 6. Contact 9 comprises a cup at the end of the electrode, enclosing the contact end of coil 4 which extends beyond coil 5 in a reduced diameter extension lil* of sleeve 6, as clearly shown in FIG. 4. A jacket ll of the same material as sleeve 6 is molded about the contact ends of coils 4 and 5, and about the sleeve extension 10, within the contact ring 8 and contact cup 9, as clearly shown in FIG. 4. In this way, the contact end 2 of the electrode is completely insulated, except for the contacts 8` and 9. It will be appreciated that after the molding operation jacket 11 and sleeve 6 become integral.

At their opposite ends, coils 4 and 5 are received in tubular terminals l2, 13 which are crimped in place on the conductor coils. A bifurcated boot 14- of the same material as jacket 6 is molded about the terminals 12, 13 and the terminal ends of coils 4 and 5, and jacket 6, with the terminals 12 and 13 projecting therebeyond. These terminals are adapted for insertion in receptacles provided on the pulse generator, which can comprise any suitable Pacemaker such as that shown for example in United States Patent 3,057,356 which may have provision for percutaneous adjustment of rate and amplitude in accordance with my pending application Ser. No. 231,349, now Patent No. 3,198,195.

The electrode construction thus far described is capable of withstanding constant, rapidly repeated flexing over a period of time which can be measured in years. The conductor coils are wound relatively tightly, although there can be a slight space between adjacent turns. This closely coiled construction provides a maximum number of conductor turns per unit length, thereby providing optimum strain distribution. The spirally coiled spring construction of the conductors also permits a substantial degree of elongation, within the elastic limits of the material, as well as distribution along the conductor of llexing stresses which otherwise might be concentrated at av particular point. Both the conductors 4 and 5, and the insulating bodies 6, 11 and 14 are elastic, and this, together with the coiled construction of the conductors, assures maximum distribution of flexing strains.

In addition to insulating the conductor coils 4 and 5, the bodies 6, 11 and 14 prevent ingrowth of tissue between convolutions of the conductor coils.

However, this very flexing characteristic, so essential to long life and dependability of the electrode, works against its adaptability for insertion through a vein, and renders it generally unsuitable for such method of implantation. Therefore, it is a particular feature of my invention that the electrode incorporates means facilitating its insertion through a body passage such as a vein, in the manner of a catheter, without impeding its flexing characteristics after the electrode is in place. This is accomplished by inserting in the open passageway or lumen through either coil 4, 5, or both of them, a stylet (FIGS. l and 7). In practice, the stylet or stylets, as the case may be, is furnished with the electrode as a removable part thereof. Each stylet 15 is formed of stainless steel or other material suitable for the purpose, and comprises for example a cylindrical wire closely tting the inner wall of the conductor coil with sufficient clearance therebetween for insertion and removal of the stylet. For example, where the coil 4 or 5 is wound on a mandrel of .016i inch dia., a stylet 15 having an outer diameter of .014 inch or .015 inch can be used.

The stylet 15 stiffens the electrode. Its distal end, at the contact end 2 of the electrode, is bent slightly, while its proximal end, adjacent the terminal end 3 of the electrode, is formed to provide means, such as the loop 16, for rotating the stylet about its axis to thereby direct the contact end 2 of the electrode as it is inserted through the vein. The stylet imparts rigidity to the proximal portion of the electrode, and introduces the` appropriate curvature to the distal, contact end portion facilitating the insertion of the electrode into and through a vein, for example one of the jugular veins, to advance the contact end 2 of the electrode into the right ventricle of the heart.

Once the electrode has been properly positioned, the stylet 15 is 'retracted and withdrawn from the conductor 4, completely separating it from the electrode, the terminals 12 and 13 of which then can be inserted into the Pacemaker sockets. This restores the electrode to its optimal condition in regard to tolerance of flexing stresses.

In the embodiment of FIGS. 1-7 the stylet is inserted through the open end of terminal 12 and through coil 4 (and/or through terminal 13 and coil 5, as the case may be) it being understood that the crimping of the terminals on the -coil ends does not interfere with passage of the stylet through the terminals and coils. This means that 4 the stylet or stylets must be removed from the electrode before the electrode is connected to the Pacemaker.

Sometimes, however, it is desired to have the stylet in place temporarily, with the electrode connected to the Pacemaker, and to be able to remove the stylet without having to dismantle the Pacemaker-electrode junction with its seal. This can be accomplished with the f-orm of electrode shown in FIGS. 8 and 9. In this embodiment, the lead portion includes an insulating jacket 60 of the same material as jacket 6 but formed with three lumens therethrough. Two of the lumens receive the conductor coils 4 and 5, in the same manner as before. The third lumen receives a lining sleeve 17 `of a flexible material which permits easy sliding of the stylet. Teflon with its selflubricating properties and its inertness in body tissue is particularly suitable. Sleeve 17 extends lengthwise within jacket 60 to the contact end and projects through the crotch of the terminal jacket 14. The stylet 15 is inserted through the sleeve 17. The contact end, not shown, of the electrode of FIGS. 8 and 9 is identical with the contact end 2 in the embodiment of FIGS. 1-7. The terminals 12 and 13 are of stainless steel or other suitable material, as in the case of the FIGS. 1-7 embodiment, but their outer ends can be closed if desired because the stylet -does not pass through the end terminals. Instead, it passes through the sleeve 17 from which it can be withdrawn after the electrode has been connected and sealed to the Pacemaker. For instance, this can be accomplished at any time after implantation of the assembly and with only a minute incision.

It will be appreciated that the stylet 15 serves the same function in the embodiment of FIGS. 8 and 9 as it did in the embodiment of FIGS. 1-7. The self-lubricating sleeve 17 facilitates insertion of the stylet through the sleeve, as distinguished from the resistance to such insertion which would be felt if the stylet were in contact with the silicone rubber of the jacket 60.

While substantial clearance has been shown between stylet 15 and sleeve 17, for ease of illustration in FIG. 9, it will be appreciated that essentially only sliding clearance is provided. With the stylet withdrawn, the electrode has the desired flexing characteristics and long flex life as previously described in connection with the embodiment of FIGS. 1-7.

It will be noted that the jacket 6 is flat sided, and rectangular, whereas the jacket 60 is circular. The rectangular form of the jacket 6 imparts directional bending characteristics to the electrode.

Accordingly, it is seen that my invention fully accomplishes its intended objects. While I have disclosed and described in detail only two embodiments of my invention, that has been done by way of illustration, and not by way of limitation. I lrealize that an electrode of my invention can assume additional forms, and I intend to include within the scope of the appended claims all modiactions and variations naturally occurring to those skilled in the art.

Having fully disclosed and completely described my invention, and its mode of operation, what I claim as new is:

1. In an electrode adapted for permanent implantation in an animal body, a sleeve of electrically insulating material having separate lumens therein, a coiled electrical conductor in one of said lumen, and a removable stylet in another of said lumen, said stylet imparting rigidity to said electrode for insertion thereof through a vein to the heart.

2. In an electrode adapted for permanent implantation in an animal body, a sleeve of electrically insulating material, a pair of coiled electrical conductors extending lengthwise within said sleeve, a stylet also extending lengthwise within said sleeve, said stylet imparting rigidity to said electrode for insertion thereof through a vein to the heart and being removable endwise from said electrode to restore the flexibility thereof.

3. In an electrode adapted for permanent implantation in an animal body, a body of electrically insulating material, electrically conductive means consisting entirely of spirally wound electrical conductor extending lengthwise within said body, and a removable stylet also extending lengthwise within said body, said stylet imparting rigidity to said electrode for insertion thereof through a vein into the heart.

4. In an electrode adapted for implantation in an animal body, a sleeve of electrically insulating material having separate lumens therein, a closely coiled electrical condu-ctor in one of said lumens, a liner of self-lubricating material in another of said lumens, and a stylet in said other lumen, said stylet providing rigidity to said electrode for insertion through a vein to the heart and being removable from said other lumen.A

5. In an electrode adapted for implantation in an animal body, a sleeve of electrically insulating material, a pair of closely coiled electrical conductors extending lengthwise of said sleeve, said coils being insulated by said sleeve, at least one of said conductors being open along its axis from one end thereof, and a stylet inserted in said one conductor, said stylet providing rigidity to said electrode for intralumenal insertion thereof and being removable from said conductor through said one end thereof for optimal flex life.

6. An electrode adapted for long-term implantation in an animal body comprising an elastic sleeve of electrically insulating material resistant to adhesion of body tissue, a pair of closely coiled electrical conductors extending lengthwise within said sleeve in spaced apart insulated relation, a pair of contacts `connected to said coils adjacent one end of said sleeve, a pair of terminals connected to said coils adjacent the opposite end of said sleeve, a separate passageway through said sleeve from the terminal end thereof substantially to the contact end thereof, and a stylet inserted in said passageway, said stylet providing ridigity to said electrode for insertion thereof through a vein to the heart and being removable from said passageway to restore flexibility to said electrode.

7. An electrode adapted for long-term implantation in an animal body comprising an elastic sleeve of electrically insulating material resistant to adhesion of body tissue, a pair of closely `coiled electrical conductors extending lengthwise within said sleeve, a pair of contacts connected to said coils adjacent one end of said sleeve, a pair of terminals connected to said coils adjacent the opposite end of said sleeve, at least one of said conductors and its terminal being open to provide a passageway through said one terminal and substantially through said one conductor, and a stylet inserted through said one terminal into said one conductor, said stylet providing rigidity to said electrode for insertion thereof through a vein to the heart and being removable from said one conductor and terminal.

8. An electr-ode as set forth in claim 3, wherein said removable stylet is inserted in said conductive means.

9. An electrode as set forth in claim 3, wherein said stylet extends lengthwise of said body externally of said conductive means.

References Cited UNITED STATES PATENTS 789,161 5/ 1905 Linn 128-409 X 2,164,926 7/1939 Kleine 128-349 2,774,382 12/ 1956 Bentley 174-47 X 2,976,865 3/ 1961 Shipley 12S-2.05 3,035,583 5/ 1962 Hirsch et al 12S- 418 X FOREIGN PATENTS 910,371 6/ 1946 France.

RICHARD A. GAUDET, Primary Examiner.

W. E. KAMM, Assistant Examiner.

Claims (1)

1. 3. IN AN ELECTRODE ADAPTED FOR PERMANENT IMPLANTATION IN AN ANIMAL BODY, A BODY OF ELECTRICALLY INSULATING MATERIAL, ELECTRICALLY CONDUCTIVE MEANS CONSISTING ENTIRELY OF SPIRALLY WOUND ELECTRICAL CONDUCTOR EXTENDING LENGTHWISE WITHIN SAID BODY, AND A REMOVABLE STYLET ALSO EXTENDING LENGTHWISE WITHIN SAID BODY, SAID STYLET IMPARTING RIGIDITY TO SAID ELECTRODE FOR INSERTION THEREOF THROUGH A VEIN INTO THE HEART.

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