Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Electrical energy applicator
Reexamination Certificate
1999-01-27
2001-05-08
Getzow, Scott M. (Department: 3737)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Electrical energy applicator
Reexamination Certificate
active
06230061
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an electrode arrangement for stimulating the heart by mans of an implantable cardiac pacemaker which generates electrical pulses.
In the treatment of various chronic disturbances in cardiac rhythm, implanted cardiac pacemakers are in use, in conjunction with stimulating electrodes disposed on an intracardial electrode catheter and positioned on the inner wall of the heart; the stimulatable cardiac tissue is excited by way of these electrodes. The design of the pacemakers and the associated electrode lines has undergone increasing perfection, and numerous technical solutions have been found for anchoring the electrode catheters to the heart wall—both in the ventricle and in the atrium-and substantial practical improvements have in fact successfully been attained.
Nevertheless, even today, electrode dislocations, which lead to a worsening of contact with the stimulatable tissue on the inner wall of the heart, or even a loss of such contact, and consequently at least a substantial increase in the stimulation threshold and thus increased current consumption by the pacemaker and reduced service life, and in the worst case cause the pacemaker to become nonfunctional, are among the most important complications in pacemaker therapy.
In addition, the fact that up to the present the stimulating pulses of an implanted pacemaker are transmitted to the stimulatable muscle tissue of the inner wall of the heart in the lower region of the ventricle or atrium are transmitted via electrodes attached to the walls is also necessarily unsatisfactory, for fundamental physiological reasons.
Floating electrodes, on the other hand, have been unable so far to assure stimulation with sufficient safety that regular use would be appropriate.
SUMMARY OF THE INVENTION
It is therefore the object of the invention to disclose an improved electrode arrangement of the generic type defined at the outset, which enables operation of a cardiac pacemaker that better suits physiological conditions with regard to localization of the stimulating pulses and is thus more reliable.
This object is attained by an electrode arrangement, according to the invention, in which a first electrode is connected to a first output of a cardiac pacemaker and is disposed on an intracardially placed electrode line and a second electrode, spaced apart from the first electrode on the electrode line, is connected to a second output of the cardiac pacemaker where the first and second electrode transmit electrical stimulating pulses up to a stimulation threshold to cardiac tissue wherein a third electrode is disposed so that the voltage pulses at the first and second electrodes have a different polarity from the third electrode and the first and second electrodes are disposed on the electrode line in such a way that the electrical dipole field that develops is distorted in the direction of the stimulation site such that an elevated potential gradient develops above the stimulation threshold.
The invention encompasses the concept of achieving an electrode arrangement and electrode triggering with which the stimulating pulses of the pacemaker can be delivered to the region that rank highly, in the hierarchy of impulse formation, in the impulse-forming and conduction system of the heart—primarily the sinoatrial node and secondarily the AV node-so that a sinoatrial node syndrome, for instance, can be treated directly where it occurs, or in the case of an AV block, stimulation can be done directly in the region primarily affected by this physiological defect.
For practical application of this concept, the proposed electrode arrangement makes use of the means of “focusing” of the electrical field, which develops in the surroundings of two or more electrodes in a suitable geometrical electrode arrangement when stimulating pulses of opposite polarity are output simultaneously, on the sinoatrial node or the AV node or other region to be stimulated.
In this way it is possible, even with a floating electrode, to concentrate such a strong electrical stimulus effect locally that physical contact between the tissue and the stimulating electrode is not required.
It is also of particular importance for the invention that not only the absolute potential course but also the field gradient in the region of the tissue should attain the highest possible value. This means that a maximum curvature in the equipotential lines in the region of the tissue to be stimulated should be attained, if at all possible in such a way that the equipotential lines enter the tissue and emerge from it again in the stimulation region. This can be attained by a geometric dimensioning in such a way that the electrode is dimensioned such that the equipotential line or plane is located on the side opposite the pacemaker. The pacemaker housing, as an indifferent electrode, in this case effects an additional strong distortion of the dipole field in the manner described. This effect is promoted by the discontinuity in the potential line course in the transitional region between tissue and blood, because of the lower specific resistance in the blood.
Elevating the potential gradient by the suitable geometric electrode arrangement on the one hand and the opposite polarity of the pulses on the other makes it possible to exceed the stimulation threshold in tissue regions not directly adjacent the electrodes, and thus makes it possible to stimulate the target regions for the excitement, namely the sinoatrial node or AV node, which are not located on the surface of the heart wall and thus are in regions of the heart where a fixation of electrodes is practically impossible.
In an embodiment of the electrode arrangement which is especially advantageous with regard to controlling the target excitation region, the electrode arrangement includes at least one third electrode, in a spatial relationship with the first and second electrodes, which is embodied and disposed and acted upon by a predetermined third voltage in such a way that in the region of the sinoatrial node or the AV node, it elevates the potential gradient above the value attainable solely with the first and second electrodes (for a given predetermined voltage amplitude).
In an embodiment that can advantageously be constructed in the conventional way and is favorable for implanting, the second electrode and/or the further electrode or electrodes are disposed in the intracardially placed electrode line.
This electrode line expediently has a length and/or curvature dimensioned such that the electrodes after introduction into the heart are disposed in the region of the roof of the atrium near the abouchement of the superior vena cava or near the septum and the abouchement of the coronary sinus into the atrium, that is, are disposed a slight distance from them, depending on whether the sinoatrial node or the AV node is to be excited.
In a preferred feature, the electrode line is embodied such that the third and/or further electrode or electrodes are disposed above the first and second electrodes, in particular approximately on the extended straight line connecting them—in the case where the sinoatrial node is stimulated, especially in the superior vena cava.
If in the aforementioned feature a third electrode is provided, then it is disposed essentially at the apex of curvature of the electrode line, such that it is spaced apart from a straight connecting line between the first and second electrodes.
Since it is unnecessary to fix the electrode line to the heart wall in the electrode arrangement of the invention, the electrode line can “float” in the heart. Thus it is accordingly constructed expediently with a flexural strength, and optionally a preimposed curvature in the longitudinal course, such that the electrodes after introduction into the heart are essentially not in direct contact with the heart wall but rather are disposed near the region to be stimulated.
In a preferred version, the electrode line has a branching point—which in an especially variable version is even still displace
Biotronik Mess-und Therapiegerate GmbH & Co. Ingenieurburo Berli
Getzow Scott M.
Kinberg Robert
Spencer George H.
Venable
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