Surgery – Instruments – Electrical application
Reexamination Certificate
1999-12-15
2001-11-20
Gibson, Roy (Department: 3739)
Surgery
Instruments
Electrical application
C606S042000, C607S101000, C607S102000
Reexamination Certificate
active
06319249
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an ablation arrangement which includes an ablation catheter with a plurality of ablation electrodes and a neutral electrode and at least one energy source and switching means for connecting the electrodes to the energy source. The invention also concerns a method of controlling the electrodes of such an ablation arrangement.
BACKGROUND OF THE INVENTION
The term ablation electrode in this respect stands for any small area energy coupling-out element and the term neutral electrode stands for any comparatively large-area energy coupling-out element. In addition the term ablation catheter is used to denote any arrangement of small area energy coupling-out elements which are spatially associated with each other by suitable connecting means.
The invention concerns in particular the general problem of producing line-shaped lesions of sufficient depth throughout in order, for example, to achieve an enduring curative effect in the ablation of tachyarrhythmmia phenomena.
To produce linear lesions of that kind it is known, for example, to use an ablation catheter with a relatively elongated electrode at the free end of the catheter. The linear lesion is produced by the electrode being slowly moved in its longitudinal direction while it is connected to an energy source.
Another ablation arrangement is known from international patent application WO-A97/20510. Described therein is an HF-ablation system in which HF-energy can be delivered simultaneously and in a predetermined phase association by way of a plurality of electrodes of a multipolar catheter. In that case, a number of power modules corresponding to the number of electrodes is used. That arrangement is complicated and expensive due to its structure. In addition, the various electrode systems are not decoupled from each other so that measurement or regulating circuits based thereon have a mutual influencing effect.
SUMMARY OF THE INVENTION
Therefore the object of the present invention is to provide ways and means of producing, in particular, linear ablation without involving high cost.
In accordance with the invention that object is attained by an ablation arrangement which includes control means which are connected to the switching means and which are of such a design that pairs of electrodes formed by two ablation electrodes and also by an ablation electrode together with the neutral electrode can be connected to the energy source in a predeterminable sequence.
In accordance with the invention the object is also attained by a method in which pairs of electrodes are connected to the energy source in a predetermined sequence, wherein the pairs of electrodes are formed both by two ablation electrodes and also by an ablation electrode together with the neutral electrode.
The invention involves the realization that different lesion patterns are formed, depending respectively on whether two ablation electrodes are connected to the energy source or whether one ablation electrode and the neutral electrode are connected to the energy source. An explanation for this phenomenon on which the invention is based is that formed between the corresponding electrodes of a pair thereof is an electrical field which in the region of the small-area ablation electrodes is strongly concentrated and has a high level of energy density while the neutral electrode is of such a large area that the energy density of the field is sufficiently low as not to cause any lesions. In accordance with the invention the result of this is that, upon actuation of a pair of electrodes comprising two ablation electrodes, the lesions occur between those ablation electrodes, while upon actuation of a pair of electrodes consisting of an ablation electrode and the neutral electrode, the lesions occur in the proximity of the one ablation electrode. The lesions can differ for example in terms of their depth: by virtue of the electrical properties of the myocardium to be treated, in comparison with the surrounding blood, the electrical field experiences concentration between two ablation electrodes connected to the energy source, and, depending on the amount of energy, the lesion is of a smaller depth, while the lesions produced by an ablation electrode in conjunction with the neutral electrode have a tendency to extend deeper into the myocardium. Actuation of a pair of electrodes comprising two ablation electrodes is referred to hereinafter as a bipolar mode of operation while actuation of a pair of electrodes consisting of an ablation electrode and the neutral electrode is referred to as a unipolar mode of operation. The core and essence of the invention is to operate an ablation catheter with a plurality of ablation electrodes both in a bipolar and in a unipolar mode in order in that way to produce in particular linear ablations. Accordingly the sequence in which the ablation electrodes are operated, as claimed, includes the unipolar and the bipolar mode of operation of the ablation electrodes.
Preferably the ablation arrangement is designed so that the ablation electrodes are arranged in succession at a determined spacing and the control means are such that the pairs of electrodes formed by two ablation electrodes are formed by mutually adjacent ablation electrodes. In a particularly preferred ablation arrangement, the control means are such that a pair of electrodes formed by ablation electrodes and a pair of electrodes formed by one of the ablation electrodes together the neutral electrode can be connected to the energy source in an alternating maimer. That means, in other words, that respectively adjacent ablation electrodes are used for the bipolar mode of operation and the unipolar and the bipolar modes preferably continuously alternate.
Accordingly, a preferred alternative form of the method is distinguished in that the pairs of electrodes formed by the ablation electrodes are formed by mutually adjacent ablation electrodes of a plurality of ablation electrodes which are disposed in succession at a determined spacing from each other. In a particularly preferred method, a pair of electrodes formed by two ablation electrodes together with the neutral electrode are connected to the energy source in an alternating manner. This also results in alternate unipolar and bipolar operation, in which respect preferably mutually adjacent ablation electrodes are connected to the energy source for the bipolar mode of operation.
A preferred method is also one in which firstly one pair of electrodes is connected to the energy source, which is formed by a first ablation electrode comprising a series of ablation electrodes which occur in succession at a spacing together with the neutral electrode. then a pair of electrodes formed by the first ablation electrode and a second ablation electrode following same, thereupon a pair of electrodes formed by the second ablation electrode and the neutral electrode, thereupon once again a pair of electrodes formed by the second ablation electrode and the next following ablation electrode, and continuing in that way in that alternate sequence, until a desired ablation length is achieved. When applied to a multipolar catheter with a tip electrode at its free end and a plurality of ring electrodes following the tip electrode, the procedure involved in the method is such that the energy of the energy source is firstly discharged in unipolar fashion between the tip electrode and the neutral electrode, then in bipolar mode between the tip electrode and the first ring electrode, then again in unipolar mode between the first ring electrode and the neutral electrode, then in bipolar mode between the first and second ring electrodes, and so forth, until the desired length of lesion is achieve. The ring electrodes are only referred to by way of example. Instead of ring electrodes, it is also possible for arrays or spirals of electrodes to be actuated in corresponding manner.
A further preferred alternative form of the method is distinguished in that one or more of the ablation electrodes are omitted in the sequen
Biotronik Mess-und Therapiegeraete GmbH & Co. Ingenieurbuero Ber
Gibson Roy
Kinberg Robert
Venable
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