FR2501034A1 - Combined anticoagulation electrode and catheter - has bipolar operation and operates on HF AC - Google Patents

Abstract

The electro-coagulation electrode is inserted into a catheter until it projects slightly beyond the end of the catheter which is placed inside a blood-vessel. It is used to block the blood-vessel partially or completely. The electrode is bipolar and fed by a high frequency (100kHz) AC. This electrode permits a coagulation in 5 to 10 seconds, with a better control of the delivered energy. The electrode is coaxial and comprises a partly insulated stainless steel wire fitted with a metallic ball and a partly insulated metallic tube. Alternatively, the electrode comprises two parallel wires embedded in an insualting material. One wire has a non-insulated end and the other wire is connected to a metallic ring.

Description

 The invention relates to endovascular electrocoagulation.

 There are many techniques for therapeutic vascular obliteration. Among these, endovascular electrocoagulation has been studied essentially on the experiential level. The electrode used is monopolar with a metallic core isolated by the angiography catheter, protruding a few millimeters from the end of the latter.

The reference electrode is a plate affixed to the subject's skin. The use of direct current allows the formation of fibrino-cruoric clots around the electrode, sometimes accompanied by burning of the vascular wall. This parietal lesion gives hope for the definitive nature of the thrombosis.

The main disadvantages of this technique are - the importance of the time necessary for the obliteration of the va
bucket (20 to 40 minutes), electrolysis of the end of the
leader that can cause metallic migration, - fragmentation of the clot with distal embolization.

The use of alternating current allows an obliteration to be obtained in a few seconds (3, 5). But it is impossible with the devices used to control the energy delivered. This lack of control of the electrical constants can be responsible for apparently identical conditions, both of an obliteration and of a rupture.
In summary, the use of monopolar electrodes has proved dangerous.

 The present invention overcomes these drawbacks and relates to electrocoagulation by alternating current using an endovascular electrode, characterized in that this electrode is bipolar, and is supplied at very high frequency. For this purpose, an alternating current generator of the order of 100 kHz is used, the voltage used varying between 0 and 100 volts, and the intensity varying between 0 and 400 mA. In the rest of this presentation, this current generator is called an electrocoagulator.

 The use of alternating current and a bipolar electrode leads to vascular damage around the "active" electrode. This lesion is of thermal origin.

It is a thermocoagulation.

This thermal rise is the consequence of ionic agitation within the electrocoagulated tissue. The intensity of the thermal rise depends on the square of the intensity (I2) and the time of application of the current (T)
From a procedural point of view, the aorta of animals or humans is approached by the percutaneous technique of Seldinger. A fine catheter is introduced into the artery whose occlusion is desired. The bipolar electrode is introduced into the lumen of the catheter, which it must finally protrude by several centimeters.

 The electrode is then connected to the electrocoagulator and the current applied; 60 volts and 75 mA are recommended constants. A spontaneous drop in current is observed after 5 to 10 seconds, linked to the drying of the artery and therefore to the opening of the electrical circuit.

 Two to three coagulations of the artery are performed a few millimeters apart, then an angiographic check confirms the occlusion. Then the angiographic catheter and the electrode are removed.

The bipolar endovascular electrode causes definitive occlusion of small diameter blood buckets (less than 2 millimeters)
To better understand the invention, two examples of embodiments are given below with reference to the accompanying drawings.
Fig. i is a schematic axial section of a coaxial bipolar electrode,
Fig. 2 is a diagrammatic axial section of a bipolar electrode with parallel wires.

 The coaxial bipolar electrode of FIG. i comprises a core constituted by a stainless steel wire 1, insulated over its entire length by a tube 2 or a tetrafluoroethylene covering, for example of the "Teflon" brand. The end of the core i is terminated by a non-insulated metal ball 3, preferably made of copper, or by a segment of a spiral metal tube or wire. The wire 1 covered with its insulator 2 is introduced inside a metal tube 4, spiral, for example one meter long, and called leader. Leader 4 is slightly shorter than the Soul and is also isolated using tretrafluoroethylene, except on a small portion 4a (external whorl) at its distal end. The end of the core i is separated from the portion 4a by an insulating sleeve 5 made of tetrafluoroethylene of variable width and of the same diameter as the tube 4.

 the core i is then electrically connected to the terminal (+) and the tube 4 (therefore the turn 4a) to the terminal (-) called "plate pole" of the electrocoagulator.

 The bipolar electrode of FIG. 2 comprises two parallel metallic wires 6 and 7 embedded in flexible insulating plastic material 8. The wire 6 is said to be "conductive" and is terminated by an end 6a called "active" not covered with plastic. The wire 7 said "neutral" is connected to a metal ring 9 called "passive" not covered with pla ~ tic. This ring 9 is located for example at eight or ten millimeters from the "active" end 6a. The dimensions are obviously variable depending on the desired use.

 Most often this probe will have nine tenths of a millimeter in diameter, the ring 9 will also have this diameter for a width of the order of two millimeters. Then the electrode tapers to the tip 6a. This bipolar electrode with parallel wires is introduced into a cooe catheter exposed previously.

 Experiments with these bipolar electrodes have shown that the variations in impedance linked to the subject are suppressed and that it is possible to control the energy delivered sufficiently to obtain the desired obliteration.

Claims (3)

 i. Electrocoagulation electrode combined with a catheter which it protrudes slightly after being placed in a blood vessel for partial or total obstruction, characterized in that it is bipolar and which is supplied with high frequency alternating current .  2. bipolar electrode according to claim 1, characterized in that it is of the coaxial type and comprises a core of insulated stainless steel wire (i), except at its end where it is provided with a metal ball (3) , an outer metal tube (4) insulated, except at its end (4a) stopping at a certain distance from the ball (3), an insulating sleeve (5) placed in the space separating the non-insulated parts of the core (i) and tube (4).  3. bipolar electrode according to claim i, characterized in that it comprises two parallel metallic wires (6-7) embedded in an insulating material, the wire (6) being longer than the wire (7) and being terminated by a so-called "active" non-isolated end (6a), the wire (7) being connected to a non-external metal ring (9) isolated, the non-isolated parts being a few millimeters apart and separated by an isolated zone.