Note: Descriptions are shown in the official language in which they were submitted.
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DEVICE FOR STIMULATING EXCITABLE TISSUE
The invention concerns an arrangement accordlng to the
preamble of ~laim l.
In the present invention, the term "stimulation" is
differentiated from the term "deflbrillation": In
stimulation, sensitive cells are selectively excited at one
point, the subsequent expansion of the excitation taking place
from that point. In defibrillation, the cells are affected
simultaneously and as extensively as possible in order to
depolarize said cells and to be able to re-establish their
natural conduction of impulses in an orderly fashion
subsequent thereto.
It can be seen in DE 32 13 331 A1 that a pacemaker electrode
should have a small geometric surface so that it produces a
high field strength and attains the desired selective
excitation for the stlmulation.
It can be seen in DE 35 23 226 A1 that as uniform a
distribution of the lines of force o~er the heart is desirable
in defibrillation.
Arrangements of this type are known in the form of cardiac
pacemakers with the appropriate electrode probes. In the
known devices, two electrodes are used, whereby an impulse
delivered by the pulse generator is used to produce an
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electric field and/or a dipole field between the two
electrodes. These known arrangements are used to stimulate
the heart tissue, i.e. they are to produce a directed
expansion of the stimulation starting from the electrodes by
means of the impulse.
Generically foreign are, for example, arrangements for
defibrillation known from EP 559 933 A1 in which a synchronous
discharging of heart cells is to be produced in the hope that
the normal stimulation activity can again be re-established or
that an excitation of the heart cells can take place
undisturbed stimulated by a cardiac pacemaker. In
arrangements of this type for defibrillation, three electrodes
are used, two of which are situated inside or outside directly
at the heart, while a third electrode is implanted under the
patient's skin.
In contrast thereto, in stimulation, i.e. when using cardiac
pacemakers, the electrodes are arranged as parietal electrodes
in the heart, i.e. they have direct contact with the cells to
be stimulated. Depending on the arrangement of the
electrodes, right ventricular stimulations or even atrio
ventricular stimulations can be obtained.
In principle, when developing cardiac pacemakers and/or
electrode arrangements for stimulation, it is desirable to
attain as low a threshold of sensation as possible. In
addition, it is desirable to protect the patient to the
greatest extent possible, i.e. to keep the number of implanted
electrodes as low as possible.
It is the object of the invention to further develop an
arrangement of this type in such a way that, when using
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conventional impulses for the stimulation, it is possible to
use parietal or floating electrodes.
This object on which the invention is based is solved by an
arrangement having the features of claim 1.
In other words, the invention proposes that, when using the
known electrode probes, the intercolmection between pulse
generator and probe should be modified in such a way that the
various electrodes provided on a probe produce overlapping
dipole fields when a single impulse is delivered by the pulse
generator. In this way, the threshold of sensation can be
reduced in such a way that both parietal and floating
electrodes can be used. In this case, local concentrations of
force lines are produced by overlapping of the electric fields
and/or dipole fields, whereby, as is known, an increase in the
number of force lines produces an amplified stimulation of the
cells, so that the non-parietal electrodes, namely floating
electrodes, can also produce a sufficient excitation of the
heart cells for stimulation.
It can therefore be used beyond the use in cardiac pacemakers,
for example, for muscular/neuronal stimulation, e.g. in
cardiomyoplasty cardiomy, to stimulate the bladder, for
skeletal muscle stimulation or for the central or also
peripheral nerve stimulation.
When using in the field of cardiac pacemaker therapy,
implantable pacemakers, external temporary pacemakers or even
implantable AICD can be made according to the invention both
when using floating electrodes in the heart and also when
using parietal electrodes in the heart.
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Advantageous embodiments of the invention can be found in the
subclaims.
Examples of embodiments of the arrangement of the invention
are shown in the drawings Figs. 1 to 10.
A heart silhouette H is schematically illustrated in Fig. 1,
in which the left ventricle is indicated with V at the bottom
on the right, while further up the atrium is schematically
indicated with A, i.e. the auricle.
Within the heart silhouette H, a probe S is indicated which
has three electrodes: The two floating electrodes 1 and 2 in
the area of the auricle _ as well as the parietal electrode 3
in ventricle V.
The probe S comprises lead-ins to the individual electrodes 1,
2 and 3, whereby it can be seen in Fig. 1 that these lead-ins
branch out, whereby each of the lead-ins allocated to the
respective electrodes 1, 2 and 3 is designated with the same
number as the respective electrode and whereby these lead-ins
are connected with the electrical contacts 4a and 4v of a
power source 5, e.g. a battery of a cardiac pacemaker. The
electrical contacts 4a are used to activate the atrium
electrodes 1 and 2, while the contacts 4v are used to activate
the ventricular electrode 3. The ventricular electrode 3 is
used primarily as fastening means for the probe S, however, it
can also be used for the known unipolar stimulation of the
heart cells, as can be seen in the interconnection with the
negative pole of the power source 5, whereby the positive pole
is connected with an additional electrode.
This additional electrode is designated with "ground", whereby
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this electrode can be formed by the housing of the cardiac
pacemaker or also by a third separate electrode on the actual
pacemaker probe S or on an independent probe.
Below this schematically illustrated arrangement in Fig. 1,
four different interconnections of the electrodes are
identified with the capital letters _, B, C and D and the run
of the lines of force of the electric fields schematically
illustrated above them. The overlapping area of two electric
fields is indicated by broken lines. The concentration of the
lines of force which, according to the invention, causes the
especially low threshold of sensation for stimulating the
heart tissue is located in this overlapping area.
It follows therefrom that the ground electrode be switched
negatively as a circuit possibility A, also electrode 1,
however, electrode 2 positively. Wiring diagram B shows
essentially the same structure, however, with exactly the
opposite electric connection of the individual electrodes:
The electrode "ground" is connected positively, electrode 1
also, electrode 2 on the other hand negatively. The run of
the electric lines of force remains essentially the same in
this case, so that the same point of a concentration of force
lines results in the area of electrode 2. However, the
polarity which can, as is generally known, affect and also
contribute to determining the behaviour of the threshold of
sensation changes.
An overlapping of the two electric fields over a substantially
larger area is caused by the interconnection of the electrodes
as per the circuit diagrams C and D: According to the
interconnection possibility C, the two electrodes 1 and 2 are
both connected negatively, while the electrode "ground" is
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connected positively. A run of the force lines which is
essentially the same is produced by a negated interconnection
of the electrodes in which the electrodes 1 and 2 are
connected positively, but the electrode "ground" is connected
negatively, i.e. by a change in polarization. Furthermore, a
similar run of the force lines results when - as indicated at
the bottom on the right in Fig. 1 - vis-à-vis electrode 2,
the electrodes 1 and "ground" are switched in reverse as shown
in the circuit diagrams C and D. In this way, the polarities
of the electrodes change, however, the basic run of the lines
of force and along with it the area of a concentration of
force lines, shown by broken lines, remain the same, so that
an especially intensive stimulation effect can be attained for
the surrounding tissue in this area and thus cause a reduction
in the threshold of sensation. In this way, the power source
5 can have either a longer life or made structurally smaller.
The probe S shown in Fig. 1 represents a conventional probe in
which the electrodes 1 and 2 are used as sensors which merely
register an auricle impulse in conventional cardiac pacemaker
arrangements. Subsequent thereto, the impulse delivered by
the cardiac pacemaker is produced with aid of the ventricular
electrode 3, whereby the latter is interconnected as a
unipolar electrode, i.e. the opposite pole/antipole to
electrode 3 is not found in the heart but on the outside, e.g.
in the form of the "ground" electrode.
Fig. 2 is constructed essentially the same as Fig. 1 and
schematically shows the arrangement of the invention in the
upper area, however, using parietal electrodes 1 and 2 and
omitting a ventricular electrode. In this case, a power
source with only two electrical contacts 4 is used. The probe
shown in Fig. 2 represents a conventional parietal auricle
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probe which, according to the invention, does not have to be
modified but only interconnected in a different manner with
the actual cardiac pacemaker to obtain the advantages of the
invention: The form of the impulses with respect to the run
of the impulses, impulse duration and impulse intensity can
remain unchanged, however, an improved stimulation of the
tissue is produced. If required, the cardiac pacemakers can
even be designed simpler than previously: While for many
applications the increase in voltage was required vis-à-vis
the voltage which the battery of the cardiac pacemaker
delivers (with aid of a so-called voltage-doubler), this type
of an increase in voltage can be omitted in many cases in an
interconnection of the electrodes according to the invention,
so that power-consuming circuit components of the stimulation
arrangement can be omitted.
Fig. 3 shows an arrangement similar to Fig. 2, however, using
floating atrium electrodes. The use of floating electrodes
spares the patient since the floating electrodes do not have
to be implanted. It is often necessary when implanting
electrodes to repeatedly select a new implanting location in
order to find a location which has as low a threshold of
sensation as possible. Generally, the implantations of
electrodes in the heart tissue have the danger of infections
and punctures, so that it is fundamentally desirable to keep
the number of implanted electrodes as low as possible.
However, the use of floating electrodes has thusfar been
disadvantageous because they require a lot of power to ensure
a sufficient stimulation in spite of the distance to the cells
to be stimulated. This could lead to irritations of the
threnicus, so that the stimulation could simultaneously
release minor skin spasms. Stimulations of this type are
ruled out in the electrode interconnections according to the
-
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-- 8
invention.
Fig. 4 shows an arrangement in which a relatively broad and
not only selective area, in which a concentration of the lines
of force is achieved, can also be obtained in circuit diagrams
A and B by use of a wide atrium electrode 2.
Fig. 5 shows that the ground electrode can be replaced when an
additional atrium electrode 4 is used. The same arrangement
shown on the right in Fig. 5 is illustrated in Fig. 6 together
with the run of the electric fields and dipole fields which
can be attained therewith and together with the circuit
possibilities A, B, C and D, whereby it is also indicated in
Fig. 6 at the bottom on the right, similar to Fig. 1, that the
two other electrodes are opposite the second atrium electrode
2, here: The two other atrium electrodes 1 and 4 can each be
switched in reverse, whereby an essentially similar run of the
electric and the dipole lines of force can be obtained.
Fig. 7 shows an arrangement similar to the one in Fig. 6,
however, with an atrium electrode 2 which is larger in
comparison thereto, so that a comparatively wide and not only
narrow or selective area of the concentration of the lines of
force result even in an interconnection of electrodes as per
circuit diagrams A and B.
An arrangement is shown in Fig. 8 in which the ventricular
electrode 3 is parietal as in the previous examples, in the
vicinity of which, however, the atrium electrode 4 is
arranged. The runs of the force lines resulting therefrom are
shown as-in the previous illustrations, whereby the area of an
increased concentration of the force lines and thus an
improved stimulating effect for the adjacent body tissue
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results in this case also within the scope of the llnes shown
by a broken line.
A conventional probe according to the prior art is also used
in the arrangement accordlng to Fig. 8. In this case, when
using this probe in a conventional m~nner, the electrodes 1
and 2 as sensors absorb the generated signals so that the
stimulatlon can then take place via the electrodes 3 and 4 in
a deferred manner. Lower thresholds of sensatlon can be
attalned by means of the interconnection of the electrodes
according to the lnvention when uslng lnexpensive conventional
probes and inexpensive conventional cardiac pacemakers.
Fig. g shows a comparison of two different interconnection
possibllities according to the invention, including a third
electrode in stimulation according to the invention: The
lllustratlon designated wlth l'Blmos 1" shows two electrodes
fastened to a common probe, said electrodes being shown as
rectangular, while the third electrode shown as an oval and
required according to the invention is formed by the pacemaker
housing as is known in a conventional unipolar stimulation
configuration. The distance between the first and the second
annular electrode (E1 and E2) is clearly less than the
distance between the second annular electrode E2 and the third
annular electrode E3 which is formed by the pacemaker housing.
In contrast thereto, the illustration "Bimos 2" shows three
annular electrodes arranged on a common probe, whereby the
distance between the first and second annular electrode E1 and
E2 can be either identical to or different from the distance
between the second and third annular electrode E2 and E3. The
third annular electrode E3 is always arranged intracardiacly
or in the lower part of the super~or vena ~arva.
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-- 10 --
Fig. 10 shows the two circuit variations "Bimos 11' and "Bimos
2", whereby a probe with three electrodes, shown as
rectangular fields, is shown in both cases. The pacemaker
housing is oval as in Fig. 9.
In the configuration according to "Bimos 1", the three
electrodes interconnected in accordance with the invention are
formed by two electrodes arranged on the probe and by the
pacemaker housing. In contrast thereto, the pacemaker housing
in the electrode interconnection according to "Bimos 2" is not
included in the electrode interconnections.
The different polarity configurations which are possible with
each of the circuit designs are shown below the two
illustrations "Bimos 1" and "Bimos 2". The darkened fields
indicate circuit possibilities which are not possible; in the
configuration according to "Bimos 1", the lightly illustrated
electrode on the probe is never part of the interconnections,
so that all of the fields below this lightly illustrated
electrode are darkened. In the circuit arrangement according
to "Bimos 2", the pacemaker electrode of the invention and in
bipolar circuits (A, B, C for the interconnections of the
invention and bi.1 ... to bi.6 for bipolar interconnections is
not included in the circuit arrangement. Unipolar circuit
arrangements in a configuration according to "Bimos 2" are,
however, possible when including the pacemaker housing, as can
be seen in the polarization illustrations according to uni.1
to uni.6.
The bipolar circuit variations 2, 3, 5 and 6 as well as the
unipolar circuit variations 3 and 4 cannot be realized in an
electrode arrangement according to "Bimos 1", so that the
corresponding circuit variation is also darkened below the
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-- 11 --
illustration of "Bimos 2 " .
