WO1999044675A1

WO1999044675A1 - Expandable electrode for implantation in a living organ and a method for implanting the electrode

Info

Publication number: WO1999044675A1
Application number: PCT/SE1999/000216
Authority: WO
Inventors: Hans LÖNROTH
Original assignee: Hälso-Och Sjukvårdens Innovationscenter
Priority date: 1998-03-06
Filing date: 1999-02-18
Publication date: 1999-09-10
Also published as: AU2752099A; SE9800714D0

Abstract

The invention concerns an electrode (1) intended to be implanted in a living organ, for emission or reception of electrical signals, and to be connected to an electric device, such as e.g. a pacemaker. The electrode (1) is expandable from a condition of insertion, in which the electrode is insertable into a living organ (3) via an aperture (4), such as e.g. a cannula aperture, into an expanded condition in which the extension of the electrode perpendicularly to the direction of introduction exceeds its extension in the condition of insertion. In its expanded condition said electrode (1) is prevented from being retracted via the aperture (4) of insertion, thus being attachable to the living organ (3). The invention likewise concerns a method of implanting an electrode (1) in a living organ (3). The method is particularly suitable for implantation of an electrode (1) in the stomach with the aid of a gastroscopic technique.

Description

EXPANDABLE ELECTRODE FOR IMPLANTATION IN A LIVING ORGAN AND A METHOD FOR IMPLANTING THE ELECTRODE

Field of Invention

The present invention concerns an electrode intended to be implanted into a living organ, such as the stomach, for emission or reception of electrical signals, and to 5 be connected to an electric device, such as e.g. a pacemaker .

The invention also concerns a method of implanting an electrode into a living organ.

10 Technical Background

The states of ill-health that result m disorder of the motor functions of the stomach and the intestinal canal still are not fully understood, although they may seriously handicap afflicted patient groups. The con-

15 dition known as gastropares (i.e. cease of motor function in the stomach) may afflict for instance patients suffering from highly advanced diabetes. This condition may be very difficult to treat. In order to ensure the motor functions of the intestinal canal under these circum-

20 stances and thus to accelerate the bowel movements, the pacemaker technique is often resorted to.

The pacemaker technique is well-known for mechanical-electrical control of the nerves of a living organ. The technique involves implantation of at least

25 one electrode in the organ concerned. Insulated lines connect the electrode to a pacemaker which is implanted underneath the patient's skin. The pacemaker generates electric impulses controlling the functions of the organ via lines and electrodes.

30 When the pacemaker technique is used to control the motor functions of the stomach and the intestinal canal the electrodes are implanted in the wall of the stomach. The electrodes supplied for this purpose are implanted by being sewn into the stomach wall, which is done in open abdominal surgical operations or with the aid of the laparoscopic surgery technique. Both implantation methods are serious operations requiring that the patient be anaesthetised.

Implantation of electrodes into a hollow living organ, such as e.g. the stomach, poses special problems since the organ wall yields as the electrodes are being implanted. In addition, the risks of inadvertent puncture of the organ wall are not negligible.

For the reasons stated there is a need for an electrode that may be implanted with the aid of a less precarious and more simple operation method that may be performed under local anaesthetic conditions. Not only would such an implantation method reduce the costs with respect to the operation as such and to the hospitalisa- tion of the patient, but it would also lessen patient discomfort .

Summary of the Invention

The object of the present invention is to provide an electrode that is easier to implant than existing electrodes, particularly in the stomach.

This object is achieved m accordance with the present invention by means of an electrode which is characterised in that from a condition of insertion, in which the electrode is insertable into a living organ via an aperture, such as e.g. a cannula aperture, the electrode is expandable into an expanded condition m which the extension of the electrode perpendicularly to the direction of introduction exceeds its extension in the condition of insertion, whereby in its expanded condition said electrode opposes its retraction via the aperture of insertion, thus making the electrode attachable to the living organ.

When in its condition of insertion, the inventive electrode may be introduced in a living organ through a small aperture, for instance by means of a cannula. The electrode, having expanded following its insertion such that the extension of the electrode perpendicularly to the direction of introduction exceeds its extension m the condition of insertion, is thus prevented from being retracted via the aperture of insertion. In this way the electrode is attached to the living organ without any other measures needed to be taken with respect to that organ than the provision therein of an aperture of insertion. An electrode in accordance with the invention thus may be implanted m a living organ in a minor and simple surgical operation that may be performed quickly and does not require complete anaesthetisation of the patient . Preferably, the electrode is arranged to expand automatically, i.e. it expands by itself and assumes its expanded condition as soon as it leaves the cannula. This is an advantageous feature in that no space-requiring mechanical means are needed to control the electrode expansion.

In accordance with one preferred embodiment the automatic expansion is achieved by configuring the electrode with an end portion which assumes the shape of a coil m the expanded condition of the electrode. The coil consists of a wire-like material possessing such properties that m the condition of insertion of the electrode the end portion of the coil may be compressed but from that condition endeavours to resume its original expanded configuration. In accordance with another embodiment the expansion of the electrode end portion is achieved by configuring the end portion not as a coil but m the shape of a T. Both electrode embodiments are reliable and owing to their simplicity, easy to manufacture.

The material of the electrode embodiments preferably is inert spring steel or a metal possessing memorious qualities. By memorious qualities is to be understood in this context that the metal lends itself to compression transversely of the direction of introduction but resumes its original configuration thereafter.

Another object of the invention is to suggest a method of implanting electrodes m a living organ, such as the stomach, that is minimally invasive and that allows the implantation to be performed under local anaesthetisation of the patient.

This object is achieved by means of a method of implanting an electrode in a living organ, which is char- acterised by forming an aperture n the organ, by inserting an expandable electrode through the aperture and by securing the electrode m the living organ by allowing the electrode to expand in a direction perpendicularly to the direction of its introduction. It is advantageous to use a cannula to form the aperture m the organ. The electrode may then be inserted in the organ by way of the cannula.

According to a preferred embodiment the method is applicable also for the implantation of electrodes m a wall of a hollow organ, in which case a gastroscopical technique is used for two important purposes. The first one is inflation of the organ to expand the organ wall, thus solving the problem connected with the wall yielding as the aperture is to be formed therein. The second pur- pose is to allow viewing of the wall from within while the aperture is being formed, thus ensuring that the organ wall is not penetrated inadvertently.

The method is particularly suitable for implantation of electrodes in the wall of the stomach. The electrode preferably is positioned n the connective tissue between the mucous membrane of the stomach and the muscle layer of the stomach wall.

Physiological saline solution may advantageously be injected through the aperture before the electrode is inserted. In this way a liquid-filled cavity is formed in the organ, which facilitates introduction and attachment of the electrode m the organ. If a cannula is used to form the aperture, the saline solution preferably is injected via the cannula. This mode of operation is advantageous also m the respect that remaining tissue, if any, is removed from the cannula. Preferably, the electrode is associated with an insulated conductor to be connected to an electric device. Upon insertion of an electrode which is connected to a conductor it is advantageous to use a cannula which is divisible m its lengthwise extension. The electrode and the conductor associated therewith are inserted by way of the cannula with the conductor extending through the cannula. After securement of the electrode, the cannula is opened up and retracted without being obstructed by the conductor. A considerable advantage associated with the claimed implantation method is that it may be performed under a local anaesthetic of the patient.

Thanks to the reduced invasiveness of the operation, the implantation of the electrodes may be performed also for diagnostic purposes. Measurement methods for this purpose have hitherto been out of the question because they involved an extensive surgical operation in order to implant the electrodes. For a diagnosis to be made, it is desirable that the function of the organ concerned be orserved for some length of time. For this reason, the electrodes are connected to a measurement instrument which may be located externally of the patient's body during the observation period.

Brief Description of the Drawings

A preferred embodiment of the invention will be described in the following with reference to the accompanying drawings, wherein

Fig. 1 is a view of an electrode 1 m accordance with the present invention m the electrode introduction position. The electrode 1 is positioned inside a cannula 2 for insertion into a living organ 3. Fig. 2 is a view of the electrode 1 of Fig. 1 m its expanded condition. The electrode 1 is implanted in a living organ 3.

Fig. 3 is a view of another embodiment of the elec- trode, the latter being shown in its expanded condition with the electrode end portion configured as a coil.

Fig. 4 is a view of a further embodiment of the electrode, the latter being shown m its expanded condition with the electrode end portion configured as a helically wound coil.

Fig. 5 is a view of yet another embodiment of the electrode, the latter being shown m its expanded condition with the electrode end portion being configured as a T. Fig. 6 is a view of an electrode 1 implanted in the wall 3 of the stomach.

Detailed Description of Preferred Embodiments

Fig. 1 illustrates a preferred embodiment of an automatically expanding electrode 1 m accordance with the invention m a condition of insertion of said electrode. The electrode 1 is located inside a cannula 2 to be inserted in a living organ 3. The cannula 2 is introduced into the organ 3. In this position, the elec- trode is compressed into an essentially elongate shape allowing introduction thereof into the organ 3 via an aperture 4 which is produced by the cannula 3. The electrode 1 is connected to an insulated conductor 5. When the electrode 1 leaves the cannula 2 it expands automatically and assumes its expanded condition.

Fig. 2 illustrates the electrode 1 in an expanded condition inside the living organ 3. The cannula 2 has been removed. In this condition, the extension of the electrode 1 perpendicularly to the direction of mtro- duction exceeds its extension m the condition of insertion, a feature which prevents the electrode 1 from being pulled outwardly via the insertion aperture 4. Figs 3, 4 and 5 show some possible embodiments in accordance with the invention. The electrodes m accordance with all embodiments are shown in their expanded conditions. In Fig. 3, the end portion of the electrode is configured as a coil extending m one plane. In Fig. 4, the end portion of the electrode is configured as a helically wound coil extending m more than one plane. In Fig. 5 the end portion of the electrode is configured in the shape of a T. All varieties of the electrodes pre- ferably are manufactured from inert spring steel or a metal possessing memorious qualities.

The invention may be modified within the scope of the appended claims. For instance, the end portion of the electrode may be configured in many different ways, and have an extension in the expanded condition of the electrode being n one plane or m several planes. It should be appreciated that the electrode could be manufactured from other electrically conductive materials than those mentioned above. The electrode may also be associated with an insulated conductor for connection to an electric device.

In a preferred version of the method in accordance with the invention the method is used to attach an electrode together with its associated conductor m the stomach wall.

Fig. 6 illustrates an electrode 1 implanted m the stomach by means of the inventive method. The stomach wall 3 has a porous connective tissue layer 7 sandwiched betwen the mucosa 6 of the stomach and a muscular layer 8. In the implantation of an electrode 1 into the stomach wall 3 in accordance with the inventive method the stomach is inflated and is viewed from within by means of a gastroscopic instrument. A cannula is made to penetrate the abdominal wall and the stomach wall 3 to be posi- tioned in the connective tissue layer 7. The cannula is in position m the connective tissue layer 7 when the mucosa 6, as determined by the gastroscopic instrument, is seen to cave inwards under the pressure from the cannula. Physiological saline solution is then injected through the cannula, thus removing from the cannula any tissue remaining therein and creating a cavity 9 m the connective tissue 7. An electrode 1 of an automatically expanding type with a conductor 5 attached thereto is introduced, while in its condition of insertion, into the cannula and further into the cavity 9 created in the connective tissue layer 7. As the electrode 1 leaves the cannula, it expands and in doing so attaches itself to the stomach wall 3. The cannula is then removed.

It is advantageous to use a cannula of a kind that may be divided into sections, allowing it to be easily removed without impediment from the electrode 1 and the conductor 5 attached thereto. To be removed, the cannula is separated into its two sections.

Finally, the conductor 5 is connected to an electric device for the purpose of control of or observation of the organ. A device of control type, for instance a pacemaker, preferably may be implanted under the patient's skin. During the observation period, a measurement device for observation of the organ is advantageously positioned externally of the patient.

The invention may be modified within the scope of the appended claims. For example, the method may be used to implant electrodes into a non-hollow organ, m which case the use of a gastroscopic technique is not necessary.

Claims

1. An electrode intended to be implanted m a living organ, for emission or reception of electrical signals, and to be connected to an electric device, such as e.g. a pacemaker, c h a r a c t e r i s e d m that from a condition of insertion, m which the electrode is insert- able into a living organ (3) via an aperture (4), such as e.g. a cannula aperture, the electrode (1) is expandable into an expanded condition in which the extension of the electrode perpendicularly to the direction of introduction exceeds its extension m the condition of insertion, whereby in its expanded condition said electrode opposes (1) its retraction via the aperture (4) of insertion, thus making the electrode attachable to the living organ 3.

2. An electrode as claimed m claim 1, c h a r a ct e r i s e d m that the electrode (1) expands automatically from the condition of insertion to the expanded condition.

3. An electrode as claimed in any one of the preceding claims, c h a r a c t e r i s e d m that m the condition of insertion the electrode (1) has an essentially elongate configuration, whereby the electrode is insertable m its lengthwise direction into the wall of the living organ (3).

4. An electrode as claimed m any one of claims 2-3, c h a r a c t e r i s e d m that the electrode (1) is formed with an end portion, said portion, m the expanded condition of the electrode (1), being configured as a coil made from a wire-like material allowing the end portion to be compressed to the condition of insertion of the electrode (1), and in that from the condition of insertion said end portion endeavours to resume its original, expanded configuration.

5. An electrode as claimed in any one of claims 2-3, c h a r a c t e r i s e d m that the electrode (1) has an end portion which is configured as a T in the expanded condition of the electrode.

6. An electrode as claimed in claim 4 or 5, c h a r^┬¼ a c t e r i s e d in that the material of the end por- tion of the electrode is a material possessing memorious properties .

7. An electrode as claimed in claim 4 or 5, c h a ra c t e r i s e d in that the material of the end portion of the electrode is a metal of inert spring steel type.

8. An electrode as claimed in any one of the preceding claims, c h a r a c t e r i s e d m that it is designed for the control and/or observation of the functions of the living organ.

9. A method of implanting an electrode m a living organ, c h a r a c t e r i s e d by forming an aperture (4) m the living organ (3), by inserting an expandable electrode (1) through the aperture and by securing the electrode m the living organ (3) by allowing the elec- trode to expand in a direction perpendicularly to the direction of its introduction.

10. A method as claimed in claim 9, c h a r a ct e r i s e d in that the method is performed on a hollow, living organ (3) having a wall, in that the organ (3) is inflated and is viewed from within with the aid of a gastroscopic technique while an aperture is being made in the wall of the living organ, in order to avoid unintentional complete penetration of said organ wall.

11. A method as claimed in claim 9 or 10, c h a r- a c t e r i s e d m that a cannula (2) is used to form the aperture (4) m the wall of the living organ, and m that the electrode (1) is inserted through said aperture (4) by way of said cannula (2) .

12. A method as claimed m claims 10 and 11, c h a r a c t e r i s e d in that the insertion of the the cannula (2) into the living organ (3) continues until 11

said cannula is seen to form m inwards bulge in the wall of the living organ (3) .

13. A method as claimed m claim 12, c h a r a ct e r i s e d m that said living organ (3) is a stomach, said cannula (2) being inserted thereinto until it is seen to form an inwards bulge m the mucosa (6) of the stomach, i.e. until the cannula tip is positioned in the connective tissue layer (7) between the mucosa (6) of the stomach and the muscle layer (8) of the wall of the stomach.

14. A method as claimed m any one of the preceding claims, c h a r a c t e r i s e d in that the expandable electrode (1) expands automatically.

15. A method as claimed in any one of the preceding claims, c h a r a c t e r i s e d m that physiological saline solution is injected through the aperture (4) prior to insertion of the electrode (1) m order to create a liquid-filled cavity (9) m said living organ (3) .

16. A method as claimed m any one of the preceding claims, c h a r a c t e r i s e d in that the electrode (1) is associated with an insulated conductor (5) prior to its insertion.

17. A method as claimed in claims 11 and 16, c h a r a c t e r i s e d m that the cannula (2) is divisible, and in that it is removed after insertion of the electrode (1) by being divided into sections.

18. A method as claimed in claim 16, c h a r a ct e r i s e d in that at least one electrode (1) is implanted and thereafter connected to an electric device.

19. A method as claimed in claim 18, c h a r a ct e r i s e d m that the electric device is a pacemaker .

20. A method as claimed m claim 18, c h a r a c- t e r i s e d in that the electric device is a measurement instrument designed for observation of the functions of the living organ (3) .