DE8525678U1 - Pacemaker electrode - Google Patents

Description

■tit HI«» _ I -■

ti ·· ti Il Il HiI

< < · 1 · I Il (I ItIII

t t t &igr;

■ I ·· Il Il CCCtI

Siemens Aktiengesellschaft Our symbol

Berlin and Munich VPA 85 P 7306

Pacemaker electrode

The invention relates to a pacemaker electrode with at least one electrical conductor which is surrounded by an insulating sheath which is inert to body fluids and is provided with a conductive electrode head at least at the distal end.

_1n Such pacemaker electrodes can be used both for stimulating the myocardium and for detecting cardiac potentials. In order to keep the necessary stimulation energy as low as possible, the current density should be as high as possible, which is most easily achieved by using the smallest possible surface area of the conductive electrode head. If such electrodes are used to sense QRS potentials, they have a relatively high source impedance of the order of 10 to 20 kohm with a smooth electrode head surface. Since the input impedance of the subsequent amplifiers is often of the same order of magnitude, these cardiac signals are strongly attenuated in the input stage. The sensing characteristics can most easily be improved by increasing the conductive surface of the electrode head. | The requirements for the size of the electrode surface are exactly opposite for stimulation and sensing, which is why optimization must be carried out .

This problem of conflicting requirements for the electrode head can also be solved in other ways, for example by making the surface of the electrode head microporous. This concentrates the current during stimulation and thus achieves the desired high current density, while the electrode head/electrolyte interface remains large enough *:

is to ensure low source impedance when sensing cardiac :

I signals. Such electrodes are for example A

GdI 1 Ed / 26.08.1985

■ t it! II , ,

It Il · I · ■ ···»·

- 2 - VPA 8S P 7306 DE

from the Siemens brochure on endocardial electrodes with an electrode head made of glassy carbon from March 1984 (A91003-M3372-L745-02-4JOÖ).

The present invention is based on the task of designing an electrode of the type mentioned at the beginning in such a way that it has both good stimulation and sensing properties and yet still allows great freedom in the design of the electrode head.

This object is achieved according to the invention in that the electrode head has areas with different impedances. These areas can be formed in a simple manner using materials with different conductivity. For example, the electrode head can have a tip with a small surface area with good conductivity for stimulation. This tip is then followed by a larger surface with lower conductivity. When stimulating, the current is therefore concentrated on the tip, since the impedance to the tissue is relatively low, for example 500 - 1000 ohms. When sensing, however, the entire surface of the electrode head is effective, since the source impedance of the electrode head can be several kohms without significantly affecting the sensing properties. In other words, the invention makes use of the knowledge that there is a large difference in impedance at the interface between the electrode head surface and the electrolyte, depending on whether the signals are small or large.

Instead of using different materials, the areas of different impedance can also be achieved by surface treatments of the same material. For example, the areas of high impedance can have a smooth surface, while the areas of low impedance can have a microporous surface.

I · a a at a 4 I I t · a a

i I t < a << i ill

&bull; ·· · 4 » at It Il 9Ii

&igr; itat &igr; aiii t tt

ti a · a lii &igr;

&bull; · aa &eegr; ti io7'i

~ 3 - VPA 85 P 7306 EN

According to an advantageous development of the invention, the low impedance areas are made of metal or metal compounds and the high impedance areas are made of conductive plastic that is inert to body fluids. As already explained, the tip of the electrode head can be made of a material with low impedance and can be intended for stimulation. However, it is also advantageous to divide the low impedance area into several sub-areas and to distribute them evenly or unevenly over the entire surface or part of this surface. The low impedance areas can be distributed in a ring shape over the electrode head. It is also possible for the areas to be distributed in strips or to form a cage pattern. In any case, the entire surface of the electrode head is larger than the entire surface of the electrode head.

&bull;j5 ser and by distributing the areas relevant for stimulation over this large surface area, there is the advantage that some of these areas will certainly make contact with highly conductive body tissue and the overall threshold can be kept low.

A further advantage is that the areas made of conductive plastic for sensing heart activity can also be used to fix the electrode head in the trabecular meshwork thanks to their special shape. These holding elements can be in the form of bristles or fins or as collars and have a relatively large surface area, which can greatly increase the sensing sensitivity. The holding elements can be used for passive or for

3Q active fixation should be provided.

In a further embodiment of the invention, it is also conceivable that the impedance of the holding elements is greater than that of the tip of the electrode head and that the holding elements thus serve to stimulate. The following six figures illustrate

is tt t· i* t &ngr;&igr;&bgr; · &igr;

iiit iti &igr; ftf

1 it · * » >-) it &eegr; ibt

1 111· I »311 > ) I

VPA 85 P 7306 DE

The following four embodiments of the invention are described and explained in more detail. They show:

Fig. 1 shows a first embodiment of the electrode according to the invention,

fig, 2 and 3 two views of an embodiment with

fin-shaped holding organs,

Fig. 4 another embodiment with ring-shaped

distributed areas of high conductivity and

Fig. 5 and 6 finally again an embodiment with holding elements.

All figures show the distal end of an electrode lead only in a schematic representation and not necessarily to scale.

In Figure 1, the electrode line is designated 1. The dashed line indicates an electrical conductor 2 which is surrounded by an insulating sheath 3. At the distal end, the conductor 2 is connected to a tip 4 made of smooth or microporous metal, a metal compound or carbon. The tip U has a low impedance and is ideal for stimulation. The surface of this tip should be as small as possible in order to achieve a sufficiently high current density and can be, for example, 10 mn ^2. This tip is followed by a ring 5 which is electrically connected to it and which can consist, for example, of a conductive elastomer or a metal with low conductivity. Metal compounds or ceramic compounds are also possible. The surface of this ring is larger than that of the tip U. Due to the lower conductivity of the ring 5, practically no current flows during stimulation.

-5- " '" VPA 85 ? 7306 EN

There is no current flowing over this surface. However, the conductivity of this ring is high enough to pick up these signals together with tip 4 when sensing the heart’s own potentials.

Figures 2 and 3 show another pacemaker electrode 11, again with a conductor 12 and an insulating sheath 13 surrounding it. Three fin-like projections 15 are provided electrically connected to a tip 14, which are made of a less conductive material than the tip 14. The fins 15 can in turn be made of a conductive elastomer and, in addition to enlarging the surface of the electrode head for sensing cardiac potentials, also serve to passively fix the electrode head. Figure 3 shows the electrode from the front.

Figure 4 shows another pacemaker electrode 21 with an electrical conductor 22 and an insulating sleeve 23, at the distal end of which there is an electrode head 24. The surface of this electrode head consists mainly of areas 25 with lower conductivity. In this embodiment, two areas 26 are provided in a ring shape, which have a high conductivity and are used for stimulation.

Figures 5 and 6 show a pacemaker electrode 31 with a conductor 32 and an insulating sleeve 33, which is provided at the distal end with a flat tip 34 made of low-impedance material, to which a ring made of a conductive elastomer 35 is connected, from which bristle-like passive holding elements 36 also made of conductive material protrude. Figure 6 shows the pacemaker electrode again from the front.

14 Patent claims
5 figures

·· HlI Il tf II ti * H

■ # * I t t (

fl 4(1 1(11 Iff 4

&bull; 4 »1 1 « 4 1

&bull; * Il till «· 4 1* IIM HI «J I

Claims (14)

-6'- ' VPA 85 P 7306 DE &bull; · st Ii . &eegr; % · It· Patent claims 1. Pacemaker electrode with at least one electrical conductor which is surrounded by an insulating sheath that is inert to body fluids and is provided with a conductive electrode head at least at the distal end, characterized in that the electrode head has regions with different impedances (4,5; 14,15; 25,26; 3^,35,36). 2. Pacemaker electrode according to claim 1, characterized in that the regions of different impedance are formed by materials of different conductivity. 3· Pacemaker electrode according to claim 1, characterized in that the regions of different impedance are formed by different surface treatment of the electrode head. ** · Pacemaker electrode according to claim 3, characterized in that the low impedance regions have a microporous surface. 5. Pacemaker electrode according to claim 2, characterized in that the low impedance regions consist of metal or a metal compound and the high impedance regions consist of conductive plastic that is inert to body fluids. 6. Pacemaker electrode according to one of claims 1 to 5, characterized in that the tip of the electrode head has the lower impedance. 7. Pacemaker electrode according to one of claims 1 to 5, 35 *· ·« · * t I I IM * · · · ItI * · * * III 4 t tt · · I tt &eacgr; II Il - 7 - VPA 85 P 7306 EN characterized in that the low impedance regions (26) are distributed in a ring shape over the electrode head (24). 8. Pacemaker electrode according to claim 1 to 5, characterized in that several areas of different impedance are distributed over the head. 9. Pacemaker electrode according to claim 8, characterized in that the areas of low impedance are evenly distributed over the head. 10. Pacemaker electrode according to claims 1 to 5, characterized in that the regions of an impedance (15; 36) serve as holding members for fixing the
Electrode head on the heart. 11. Pacemaker electrode according to claim 10, characterized in that the holding members are designed in a known manner for passive fixation in the trabecular meshwork of the heart. 12. Pacemaker electrode according to one of claims 10 or 11, characterized in that the impedance of the holding members is greater than that of the tip of the electrode head . 13. Pacemaker electrode according to claim 12, characterized in that the holding members consist of conductive plastic. 14. Pacemaker electrode according to one of the preceding claims, characterized in that the total area of the high impedance regions is larger the entire area of the low impedance regions. ■ I I i II» ■ t · I