Catheter and Method, in Particular for Ablation and Like Technique

Abstract

The invention relates to a catheter, provided with an elongated body with an electrically conductive first end, wherein through said body at least one live wire extends which is connected to said first end and a channel for feeding a cooling fluid through said body, which channel is provided, in or near said first end, with at least one outlet opening and wherein, in said first end, a temperature sensor has been arranged, while said channel is thermally insulated from said first end.

Description

In the further subclaims, further advantageous embodiments of the invention are described. In clarification of the invention, embodiments of the invention will be further described with reference to the drawing. In the drawing:

FIG. 1 schematically shows a catheter according to the invention with a first end in a heart ventricle;

FIG. 2 schematically shows a number of catheters in a heart, for treatment of heart rhythm disturbances;

FIG. 3 schematically shows, greatly enlarged, in cross section, a forward end of a catheter according to the invention, in a first embodiment;

FIG. 4 schematically shows, greatly enlarged, in cross section, a forward end of a catheter according to the invention, in a second embodiment;

FIG. 5 schematically shows, greatly enlarged, in cross section, a forward end of a catheter according to the invention, in a third embodiment; and

FIG. 5A shows a cross section along the line VA-VA in FIG. 5.

In this description, identical or corresponding parts have identical or corresponding reference numerals. The embodiments shown are only given by way of example and should not be construed as being limitative in any manner. In particular, combinations of parts of the embodiments shown are also understood to be described herein. Herein, a body cavity is understood to include at least each part of a human or animal body which can be reached by a forward end of a catheter.

In FIG. 1 it is schematically shown how a catheter 1 has been inserted into a heart 2 of a patient 3. A forward end 4 of a catheter 1A is inserted into a ventricle 5, in particular a right ventricle of the heart, while the corresponding forward end 4 of the second catheter 1B is inserted into the right atrium of the heart 2. This is merely shown as an illustration of possible positions. The catheter(s) has/have or has/have been inserted into the heart 2 from, for instance, the groin of the patient 3, which is a method known per se and will therefore not be described further, no more than the known method and device for controlling these catheters and the works thereto in the catheter.

In FIG. 2, in cross section, a heart 2 is shown, with left and right ventricle 5A, 5B and left and right atrium 6a, 6B. Into this heart 2, four catheters 1 have been inserted. During, for instance, a measurement and/or treatment of heart rhythm disturbances, one or more catheters 1 can be inserted into the heart 2, in order to obtain a clear picture of the electric currents in the heart. Each of the catheters 1 shown has a body 7 which is elongated and can be guided through the vascular system of the patient. The body 7 has a forward end 4, further to be called the first end 4 which is inserted as far as into the heart 2. In, at least adjacent the first end, a number of electrodes 8 is provided in the form of metal rings, for instance three, which are separated from each other by electrically insulating material of the body and each can be connected, via a conductive wire through the body 7 to electronic equipment, so that, in a manner known per se, measurements can be carried out, for instance an electrogram can be made.

The first end 4 is further provided with a tip 9 manufactured from an electrically conductive material such as metal, which tip, via an electrically conductive wire 10 (FIGS. 3-6), can be connected to electronic equipment (mentioned but not shown) with which, via the wire 10, current can be fed to this tip 9. During the measurement and/or the treatment, the patient lies on an electrically conductive underground, for instance on a earthed plate (not shown). For performing the treatment, for instance an ablation, the tip 9 of the catheter 1 is pressed against the wall 11 of the heart 2, so that a current will start to run through this wall 11. As a result of electrical resistance of the tissue of the wall, heat development will occur adjacent the tip 9, so that tissue can be treated, in particular heart muscle cells can be killed, so that undesired conduction pathways in the heart 2 or undesired sources of heart rhythm disturbances can be blocked. This is a known treatment, called ablation technique, for preventing heart rhythm disturbances. For a further description of these techniques, reference is made to the publication mentioned in the introduction and relevant manuals.

It is known to use a cooling fluid in a catheter 1 for use in for instance ablation techniques. This liquid is brought through a channel in the catheter to the forward end of the catheter and from there it is either introduced into the blood stream or returned through the catheter. At the inside of the catheter, the cooling fluid is then brought into intimate contact with the electrode to be cooled such as the tip of the catheter, in order to cool this electrode and thus prevent deposition of proteins on the outside. Such a catheter is for instance described in EP 0 856 292. However, such catheters have the drawback that the temperature of the respective electrode, such as the tip, no longer yields a good picture of the heat development in the wall 11 and/or in the blood B around this electrode.

With a catheter 1 according to the invention, these drawbacks have been solved in that, during use, the electrode such as the tip 9, is not cooled, at least not directly, but that the blood B is, so that, in the blood, no coagulation occurs and clots are prevented. As a result, the temperature of the respective electrode such as the tip 9 can be accurately measured and controlled, while, from it, an estimate can be made of the temperature of the wall 11.

Hereinafter, a number of examples of catheters 1 according to the invention is described.

In FIG. 3, a first embodiment of a forward end of a catheter 1 according to the invention is shown, in cross-sectional side view.

This catheter 1 comprises an elongated body 7 with a first end 4, formed by a tip 9 made of an electrically and thermally conductive material, in particular metal such as platinum. The body has a longitudinal axis A-A and comprises a substantially cylindrical wall 12 through which a channel 13 extends. Between the wall 12 and the channel 13, there is an annular space 14 through which extends, for instance, the electrically conductive wire 10, the different connecting points for the electrodes 8 and control means known per se (not shown) for control of the end 4. Moreover, through the annular space 14 a second electrically conductive wire 15 extends which is connected to a thermocouple 16.

In the embodiment shown in FIG. 3, the tip 9 is coupled to the body 7 by means of a coupling part 18 which is attached, for instance glued, by a first side within the wall 12, and, on the other side, fitted in a compatible second snap edge 20 of the tip 9 via a snap edge 19. In this embodiment, the thermocouple 16 has been arranged in or against the interface 17 between the body 7 and the tip 9, at least on the end surface 21 of the tip 9 proximal to the body 7 and the coupling part 18.

In the first end 4, in particular in the tip 9, a channel part 22 is provided extending in line with the axis A-A and connected to the channel 13, for instance in that a sleeve 23 extends from the end surface 21 in the channel 13 and is fitted therein. From an outside 41 of the tip 9, first bores 24 are provided reaching as far as in the channel part 22 and extending substantially radially. These first bores 24 all have a longitudinal axis 25 including an angle α with the longitudinal axis A-A of the body 7, for instance approximately 90°. A second bore 26 is provided in line with the channel 13, at least with the axis A-A, which bore 26 terminates in the apex 36 of the tip 9. In each bore 24, 26, as well as around the channel part 22, a thermally insulating casing 27 is provided such, that during use a cooling fluid, in particular physiological salt solution, can be passed through the channel 13, the channel part 22 and the bores 24, 26 without direct contact occurring between the cooling fluid and the (inside of) the tip 9. Thus, direct cooling of the tip 9 by the cooling fluid is prevented for the larger part. In the elaboration of FIG. 3, the sleeve 23 is not thermally insulated.

In FIG. 4, a first, more advantageous alternative embodiment of a first end 4 of a catheter 1 according to the invention is shown, distinguished from the one according to FIG. 3 in that here, also the sleeve 13 is thermally insulated, while, moreover, the thermocouple 16 is arranged closer to the apex 36 of the tip 9, so that an even more accurate temperature measurement of, in particular, the heart wall can be performed.

In FIG. 5, a further alternative embodiment is shown, with only tip 9 in cross-sectional side view, which, as to built-up, largely corresponds to the one of the elaborations of FIGS. 3 and 4. However, here, a tip 9 is provided having a core 28, manufactured from a material with a low thermal and/or electrical conductivity, for instance glass, ceramics or plastic, and a casing 29 with, relative thereto, a good heat conductivity and/or electrical conductivity. Here, only in the casing 29 the bores 24, 26 have been provided with a thermal inside casing, at least formed as part of the core 28, so that in a simple manner the desired thermal insulation is obtained. In this embodiment, the longitudinal axes 25 extend approximately tangentially relative to the channel part 22 (FIG. 5A) and include an angle a with the longitudinal axis A-A which angle deviates from 90°, for instance approximately 75° to 80, such that the outflow direction is slightly in the direction of the apex 36, at least in the direction of the wall 11. Thus, the cooling of the blood around the tip 9 and adjacent the wall 11 can be even more improved. A thermocouple 16 has been provided against the casing 29.

In the embodiments according to the FIGS. 3-5, each time, the extremity of each bore 24, 26 forms an outflow opening 30 for cooling fluid. These outflow openings 30 can for instance be formed such that during use a turbulent flow is generated in blood flowing by. Means that can be used to that end are known from hydrodynamics. In the embodiments shown, for instance thirteen outflow openings have been provided but it will be clear that any number of outflow openings 30 can be provided.

Optionally, near the electrode, in particular near the interface 17 between body 7 and tip 9, one or more outlet openings can be provided, so that a part of the cooling fluid is directed along the tip 9, at least along the outer surface of the electrode, for direct cooling of the blood and/or generating turbulence.

When using a catheter 1 according to the invention in a treatment of, for instance, heart rhythm disturbances or the like, wherein ablation technique is used in a body cavity flown-through with blood such as a ventricle or atrium of a heart or an artery or a vein, preferably, the current intensity and the supply of cooling fluid is regulated such, that the temperature of the blood around the tip 9 is kept below the coagulation temperature. In practice, this means below approximately 56° C., so that no coagulation occurs. Preferably, the temperature of the tip 9 is regulated such that it does not exceed 65° C. In practice, this has appeared to be a reasonably safe limit. With larger electrodes (of a length of, for instance, 8 mm instead of 4 mm) relatively more cooling will occur to blood flowing around so that there is a larger difference between the tissue and electrode temperature. With an 8 mm tip, 50 to 55° is a good target value, at least with existing electrodes. The electrode will clearly remain cooler than the heated tissue of the wall, which is kept below 100° C. in order to prevent the earlier-mentioned explosions. In FIG. 3, schematically, in the wall 11 an area 40 is indicated in which heat development occurs as a result of the current passed through the wall 11, as described earlier. Naturally, as to dimension and shape, this area of influence 40 depends on the current intensity used, and duration of the treatment and is only given by way of indication.

The invention is not limited in any manner to the exemplary embodiments given in the description and the drawing. Many variations thereon are possible within the framework of the invention as outlined by the claims.

For instance, different materials can be used for the different parts, and outflow openings can be provided in different manners, as long as, at least substantially, the tip 9 is prevented from being cooled from the inside by cooling fluid flowing therethrough. The leading end of the catheter can have any desired shape and can also be used on different locations than the heart, for instance also for fighting tumors and such aberrations of for providing scar tissue in a controlled manner. A catheter according to the invention can also be provided with several electrodes, at least one of which being provided with a cooling device according to the invention, with insulated outflow opening. Also, only one electrode can be provided at a distance of the end.

These and many comparable variations are understood to fall within the framework of the invention as outlined by the claims.

Claims

1. A catheter, provided with an elongated body with an electrically conductive first end, wherein through said body extends at least one live wire, which is connected to said first end, and a channel for feeding a cooling fluid through said body, which channel is provided, in or near said first end, with at least one outlet opening; and wherein, in said first end, a temperature sensor has been arranged; and wherein said channel is thermally insulated from said first end.

2. The catheter according to claim 1, wherein said at least one outlet opening is provided in said first end.

3. The catheter according to claim 1, wherein said channel has a longitudinal direction and wherein said at least one outlet opening comprises a series of outlet openings, which outlet openings are arranged such that, during use, cooling fluid supplied through said channel flows out through said outlet openings in an outflow direction which is angled with respect to said longitudinal direction.

4. The catheter according to claim 3, wherein the outlet openings are provided with a thermally insulating inside casing.

5. The according to claim 1, wherein said at least one outlet opening is provided in said body, adjacent said first end.

6. The catheter according to claim 1, wherein said first end is attached to said body, wherein said temperature sensor is provided in said first end, at a distance from an interface formed between said body and said first end.

7. The catheter according to claim 3, wherein the outlet openings are designed such that cooling fluid flowing therefrom during use flows away from said first end.

8. The catheter according to claim 1, wherein said first end has at least one metal outside.

9. A method for thermal treatment, in particular ablation, wherein a catheter with an electrically conductive first end is provided in a body cavity, with said first end near or, preferably, against a wall of said body cavity, while at a distance from said first end a complementary electrically conductive element is arranged, preferably outside the body in which said cavity is located, whereupon an electric current is generated between said first end and said conductive element, such that said wall is heated, whereupon, adjacent said first end, a cooling fluid is dispensed, while the temperature of said first end is measured and is regulated, while direct cooling of said first end from the inside thereof by said cooling fluid is prevented.

10. The method according to claim 9, wherein said cooling fluid, through a channel in said catheter, is supplied and dispensed in protein containing liquid, while said cooling fluid in said catheter is separated from at least said first end through thermal insulation.

11. The method according to claim 9 or 10, wherein the cooling fluid is dispensed in a protein containing liquid such as blood around said first end such that said protein containing liquid is cooled with the aid of said cooling fluid adjacent an interface between said protein containing liquid and said wall and near the outside of said first end and is kept at a temperature below the coagulation temperature of said protein containing liquid.

12. The method according to claim 9, wherein said ablation is performed in a body cavity wherein blood is present, while the temperature of said blood is kept at a temperature below approximately 55° C. and the temperature of said first end is regulated such that it remains below approximately 65° C.

13. The method according to claim 9, wherein the cooling fluid comprises a physiological salt solution, wherein the physiological salt solution is introduced into said protein containing liquid such that, around said first end, turbulence occurs in said protein containing liquid.

14. A catheter comprising the following: an elongated body with an outer surface and an electrically-conductive first end;at least one live wire extending through said elongated body, said at least one live wire being connected to said electrically-conductive first end;a channel extending through said elongated body, said channel being adapted to deliver a cooling fluid through said elongated body;at least one thermally-insulated outlet opening extending from said channel to said outer surface of said elongated body at or near said electrically-conductive first end; anda temperature sensor arranged in said first end.

15. A catheter according to claim 14, wherein said channel has a longitudinal axis, wherein said at least one thermally-insulated outlet opening comprises a series of outlet openings adapted to deliver said cooling fluid toward said outer surface of said elongated body in an outflow direction, and wherein said outflow direction is at an angle relative to said longitudinal axis.

16. A catheter according to claim 15, wherein said at least one thermally-insulated outlet opening comprises a thermally-insulating inside casing.

17. A catheter according to claim 14, wherein said at least one thermally-insulated outlet opening is provided in said elongated body, adjacent to said first end.

18. A catheter according to claim 14, wherein said first end is attached to said elongated body, wherein said temperature sensor is provided in said first end at a distance from an interface formed between said elongated body and said first end.