Electric Heart Stimulation Method And Electrode

Abstract

Apparatus and method for electrically stimulating a heart by means of a flexible filament that carries a conductor connected to an electrode which is exposed at the surface of the filament. According to the preferred embodiment, a portion of the filament extends beyond the electrode, thereby forming a flexible tail section that helps to hold the electrode at a desired position within the heart. According to the preferred method aspect of the disclosure, the above-described filament is introduced into a vein in the arm so that it is carried to the heart by the ordinary blood flow through the vein. The tail section of the filament is carried through the heart into a portion of the lungs in order to stabilize the position of the electrode within the heart.

Description

BACKGROUND OF THE INVENTION

This invention relates to heart stimulation techniques, and is more specifically directed to techniques for applying an electric current to the heart through a filament.

Numerous illnesses, such as heart infarct and myocarditis, require an artificial stimulation of the heart for a limited period of time. After the acute stage of the illness is passed, naturally occurring stimulation of the heart is adequate, so that the artificial stimulation may be eliminated.

Various apparatus and methods for artificially stimulating the heart have been developed in the past, but each has exhibited certain deficiencies that have limited its overall usefulness. For example, one such technique involves the use of a relatively stiff catheter that could injure heart and other delicate tissue unless the device is introduced by a specialist with X-ray control. Another technique consists of a catheter comprising a wire netting which is insulated with a plastic material. This catheter is relatively flexible, but is unipolar. That is, the electrode of the catheter is located at the end point thereof. As a result, the electrode is free to move within the ventricle of the heart, so that it may produce dangerous and undesired mechanical irritations. In addition, such a catheter has a tendency to move in an uncontrolled manner into the right auricle of the heart.

Accordingly, it is a principal object of the present invention to avoid the disadvantages of the prior art techniques and to create improved stimulation apparatus which can be easily introduced into a vein and transported to the heart without X-ray control and without the danger of cuts or punctures in the walls of the vein or heart tissue.

Another object of the present invention is to provide an improved filament for safely and conveniently introducing electrodes within the heart so that the electrodes have a fixed position in the heart and can be maintained in this position for a relatively long period of time by means of a tail section provided on said filament.

Another object of the present invention is to provide an improved method of introducing an electrically controlled electrode into a vein so that the electrode is carried to the heart by normal blood flow and is accurately maintained in a predetermined position in the heart.

Yet another object of the present invention is to provide improved means for fabricating electrodes used in heart stimulation apparatus.

SUMMARY OF THE INVENTION

In order to overcome the deficiencies of the prior art apparatus and methods, and in order to achieve the foregoing objects, the present invention, in principal apparatus aspect, comprises a filament flexible enough to be carried by the blood flow in a vein, an electrical conductor carried within the filament, and an electrode connected to the conductor and located at the outer surface of the filament. According to the preferred embodiment, the electrode is displaced from the end point of the filament by a tail section of the filament having a predetermined length.

By making the filament out of flexible material and by limiting the thickness of the filament, the electrode can be introduced into the heart without X-ray control and without any substantial danger to the patient. Since the thickness of the filament is very small, it can be quickly introduced into a vein e.g., a vein in the arm) in a relatively painless manner even without local anaesthesia. Moreover, the danger of thrombosis, cuts, or punctures of the vein is completely avoided, so that the filament may be easily manipulated by persons who are not specialists.

When the filament is introduced into a vein in the foregoing manner, the filament is carried along the bloodstream and eventually into the heart. According to the preferred embodiment, the tail section of the filament is carried through the heart into a portion of the lungs, thereby stabilizing the position of the filament so that the electrode is accurately located in a predetermined portion of the heart.

According to another aspect of the invention, the filament is fitted with a plastic core that improves the tensile strength of the filament without substantially reducing the requisite flexibility, thereby reducing the danger of rupturing the electrical conductor.

By constructing the filament in the above-described manner, it is possible to use a portion of the electrical conductor as an electrode in a convenient manner.

DESCRIPTION OF THE DRAWINGS

These and additional objects, advantages, and features of the present invention will hereinafter appear for purposes of illustration, but not of limitation, in connection with the accompanying drawings in which like numbers refer to like parts throughout, and in which:

FIG. 1 is a fragmentary, schematic illustration of a preferred form of filament made in accordance with the present invention that shows the manner in which the filament is introduced into a heart;

FIG. 2 is a fragmentary, perspective view of one embodiment of stimulation apparatus made in accordance with the present invention;

FIG. 3 is a fragmentary, partially schematic illustration of a preferred form of stimulation apparatus made in accordance with the present invention;

FIG. 3 is a fragmentary, partially schematic illustration of a preferred form of stimulation apparatus made in accordance with the present invention;

FIG. 4 is a cross-sectional view taken along line IV--IV in FIG. 3 ;

FIG. 5 is a fragmentary, partially schematic view of one manner of constructing the electrodes made in accordance with the present invention ; and

FIG. 6 is a fragmentary, partially schematic view of another method of constructing the electrodes made in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, one form of stimulation apparatus made in accordance with the present invention comprises a hollow catheter-like filament 1 through which a flexible wire conductor 2 is connected to electrodes 3. The electrodes are positioned at a distance from the end 4 of filament 1 so that a tail section 5 is formed.

According to the preferred method aspect of the present invention, filament 1 is introduced into a vein 6 in the region of the arm bend of a patient by well-known techniques. Thereafter, the filament, including tail 5, is carried along by the bloodstream in the direction of arrow 7 into the right ventricle 8 of the patient's heart 9. After entering ventricle 8, tail 5 is diverted by the bloodstream in the direction of arrow 10 through the outlet of the artery of the lungs, and eventually arrives in an artery of the lungs 11. When tail 5 arrives in the lungs, it tightens electrodes 3 and pulls them against a wall 12 of the right ventricle so that the electrodes assume a fixed position favorable for stimulation of the heart. In order to achieve this effect, tail 5 should be 15 to 30 centimeters in length. After electrodes 3 and tail 5 are in place, a current is generated and conducted through conductor 2 by well-known techniques so that the heart is stimulated.

FIG. 2 illustrates another form of the invention that is somewhat analogous to the embodiment illustrated schematically in FIG. 1. As a result, corresponding parts are provided with the same reference numerals. In the embodiment of FIG. 2, tail 5 is provided with a roughened surface 5a which increases the flow resistance thereof. This additional resistance aids the transportation of the entire filament through a vein by the flow of blood. The roughening may conveniently be achieved by coating the tail section with fine plastic particles. It should be noted that the roughness which is provided in the range of tail 5 may also extend over the entire length of filament 1.

As shown in FIG. 2, filament 1 is hollow and is fitted with two electrodes 3. The filament may also be fabricated in other ways. For example, it may comprise a mesh covered by a smooth outer skin. In order to retain the flexibility of filament 1, and in order to provide electrodes 3 with a sufficiently large effective area, the plastic material forming the outer surface of filament 1 is softened by the application of steam, and the electrodes are then applied onto the softened outer surface. The provision of two electrodes, of course, increases the effective surface area thereof. The electrodes are conveniently connected by conductor 2.

A preferred form of stimulation apparatus made in accordance with the present invention is illustrated in FIG. 3. The apparatus comprises a thin solid filament 13 of polyurethane having a mean diameter of 1 millimeter or less. The filament has a thin, braided plastic core 14 carried at the midline thereof. Two flexible wire conductors, 15 and 16, are embedded on opposite sides of core 14 and midway between the outer wall of filament 13 and core 14. Core 14 absorbes all traction forces so that filament 13 does not tend to stretch. As a result, conductors 15 and 16 do not tend to break, and the reliability of the apparatus is significantly increased.

The embodiment of FIG. 3 is preferably provided with a tail section such as the one shown in FIG. 2.

FIG. 5 illustrates one manner in which filament 13 may be constructed so that conductors 15 and 16 may be used as electrodes. More specifically, this result may be achieved by providing recesses 17 and 18 in connection with conductor 15, and by providing recesses 19 and 20 in connection with conductor 16. When the recesses are constructed in the manner illustrated, conductors 15 and 16 are partially exposed so that they may be used as electrodes. Naturally, the electrode surface may be increased by pressing rings about the circumference of filament 13 in contact with the electrodes, or by analogous means. The linear extension of recesses 17-20 is relatively small, and the elevated sections 21 and 22 are left standing between recesses 17, 18 and 19, 20, respectively, so that conductors 15 and 16 will not work themselves free even though they are put under considerable strain.

FIG. 6 illustrates a preferred method of fabricating conductors 15 and 16 so that they may be used as electrodes. As illustrated in FIG. 6, conductors 15 and 16 are somewhat drawn out and externally wound around filament 13 in the form of windings 23 and 24, respectively. The windings are fastened by means of knots 25 and 26 that are secured through applied drops 27 and 28 of dissolved plastic material. Additional drops of plastic material 29 and 30 may be applied to prevent windings 23 and 24 from sliding. Alternatively, windings 23 and 24 may be sewn through the filament.

The filament may also be used to measure pressure by merely providing a channel 32 in filament 13 that exits to the surface of the filament at the point at which the pressure measurement is desired.

Those skilled in the art will realize that the specific structures and methods of operation described herein may be altered without departing from the spirit and scope of the invention.

Claims

What is claimed is:

1. Apparatus for the electric stimulation of a heart comprising:

an electrode;

a conductor connected to the electrode; and

flexible filament means having an outer surface and an end point for carrying the electrode and the conductor solely by blood flow in a vein to the heart, said electrode being exposed at the outer surface and being supported by the flexible filament means at a predetermined distance from the end point such that the electrode is maintained at a predetermined position in the heart solely by ordinary blood flow.

2. Apparatus, as claimed in claim 1, wherein said predetermined distance is adapted to extend from the right auricle of the heart to the outlet of the artery of the lungs.

3. Apparatus, as claimed in claim 1, wherein the predetermined distance is 15 to 30 centimeters long.

4. Apparatus, as claimed in claim 1, wherein the flexible filament means comprises solid polyurethane having a means diameter of about 1 millimeter or less.

5. Apparatus, as claimed in claim 1, wherein a flexible core is carried by the flexible filament means adjacent the midline thereof.

6. Apparatus, as claimed in claim 5, wherein the conductor is carried through the flexible filament means between the core and the outer surface of the filament.

7. Apparatus, as claimed in claim 6, wherein the conductor is carried in the flexible filament means midway between the core and the outer surface of the flexible filament means.

8. Apparatus, as claimed in claim 6, wherein the conductor comprises a flexible wire.

9. Apparatus, as claimed in claim 1, wherein the electrode comprises a portion of the conductor.

10. Apparatus, as claimed in claim 9, and further comprising a second conductor carried on the side of the flexible filament means opposite said conductor, the second conductor being exposed at the outer surface of the flexible filament means.

11. A method of stimulating a heart by means of a filament having sufficient flexibility to be carried solely by blood flow in a vein to the heart, said filament comprising an electrode exposed at the outer surface of the filament and a conductor connected to the electrode, said method comprising the steps of:

guiding the filament into a vein so that the filament is carried through the vein and the electrode is positioned in the heart solely by blood flow; and

conducting an electric current through the conductor to the electrode, whereby the heart is stimulated.

12. A method of electrically stimulating a heart by means of an electrode, said method comprising the steps of:

arranging the electrode on a filament that is carried through a vein by ordinary blood flow;

guiding the filament and electrode into a vein so thet the electrode is carried through the vein into the heart solely by blood flow in the vein;

passing a portion of the filament through the heart and into another blood vessel so that the electrode is maintained at a predetermined position in the heart;

generating an electric current; and

conducting the electric current through the filament to the electrode, whereby the heart is stimulated.

13. A method, as claimed in claim 12, wherein the portion of the filament passed through the heart is 15 to 30 centimeters long.