WO2019092096A1

WO2019092096A1 - Laser applicator having an elongate catheter

Info

Publication number: WO2019092096A1
Application number: PCT/EP2018/080596
Authority: WO
Inventors: Martin HETTKAMP; Dennis Krist
Original assignee: Vimecon Gmbh
Priority date: 2017-11-08
Filing date: 2018-11-08
Publication date: 2019-05-16
Also published as: DE102017219862A1

Abstract

The invention relates to a laser applicator, comprising an elongate catheter (10), which contains at least one peripherally closed lumen (14), and an optical waveguide (20), which extends along the catheter and which has, in a distal end portion (10c) of the catheter, an outcoupling region (40) for coupling laser light out of the optical waveguide, the laser applicator having, in the region of the outcoupling region (40), at least one electrode (102, 104, 108, 110, 112, 114, 116) reducing the outcoupling of the laser light, such that the position of the outcoupling region relative to surrounding tissue can be sensed, and the outcoupling region (40) being formed by a groove (13) in the outside of the catheter, the optical waveguide (20) extending in the groove (13), and, in the outcoupling region or in a region adjacent thereto, material of the catheter (10) that adjoins the groove being homogeneously mixed with a material having optically reflective properties, and the groove being filled with a transparent material (33).

Description

Laser applicator with an elongated catheter

The invention relates to a laser applicator with an elongate catheter containing at least one lumen closed on the circumference, and a light guide extending along the catheter, which has a coupling-out region in a distal end section of the catheter.

Such a laser applicator is described in WO 2007/118745 A1 (Vimecon), the contents of which are incorporated by reference into the present description. The known laser applicator has an elongated flexible catheter containing a light guide. The distal end portion is a lasso-like Loop formed whose plane is transverse to the main part of the catheter. At the proximal end, the laser radiation is fed into the light guide. At the distal end of the catheter is a decoupling region, at which the energy is decoupled laterally from the light guide and leaves the catheter. The distal end is the forward, patient facing and laser energy source opposite end of the catheter. The proximal end is the rear end of the catheter facing the laser energy source and opposite the patient.

The laser applicator is used in particular for the treatment of atrial fibrillation and other heart rhythm disorders. With it heart tissue can be obliterated by conversion of light energy into thermal energy. As a result of the laser radiation emerging from the light guide, the surrounding tissue is heated until denaturation of proteins and formation of an electrically inactive scar occurs.

DE 10 2006 039 471 B3 describes a laser applicator which contains a catheter with a light guide. In a distal end portion of the catheter, the cladding of the light guide has a recess at which light emerges laterally from the light guide. While the intact cladding of the light guide provides total reflection, thereby transporting the light energy longitudinally of the light guide, the recesses at the boundary of the core of the light guide cause refraction, thereby coupling out radiant energy.

DE 10 2008 058 148 A1 (Vimecon), the contents of which are also incorporated by reference into the present description, also describes a laser applicator with an elongate catheter and a light guide extending along the catheter with a decoupling area in the distal end section of the catheter.

DE 10 2015 202 214 A1 and WO 2016/128205 A1 describe a laser applicator in which electrodes are arranged in a distance defined to the decoupling area in order to be able to detect the position of the decoupling area in relation to surrounding tissue. This is based on the idea that the decoupling region with the aid of the detected position of the decoupling region so can be specifically targeted that the laser light is introduced into the tissue to be ablated. In order to avoid overheating of the electrodes, they are arranged at a distance from the decoupling area.

Based on the above-described prior art, the invention has for its object to provide a laser applicator with which an accurate navigation in the surrounding tissue is possible.

The laser applicator according to the invention is defined by claim 1.

Accordingly, an optical waveguide runs along the catheter and has a decoupling region in a distal end section of the catheter. The laser applicator has at least one electrode which reduces the outcoupling of the laser light from the optical waveguide in order to be able to detect the position of the decoupling region with respect to surrounding tissue. The at least one electrode is thus arranged with respect to the decoupling region in such a way that the decoupling of the laser light in the region of the electrode is reduced. In the region of the electrode, therefore, less laser power is coupled out, since the electrode is located in the beam path of the coupled-out laser light. In the decoupling region or in an area adjacent thereto, the laser applicator is homogeneously mixed with a material having optically reflective properties.

As a result, the laser light is reflected by the material with optically reflective properties and is thereby decoupled from the catheter without heat being generated during the reflection, which could damage the electrodes. Conventionally, it has just been avoided to attach electrodes in the decoupling area. Rather, electrodes were at most arranged at a sufficient distance from the decoupling region in order to avoid overheating of the electrodes. According to the invention, it is thus possible for the first time to arrange electrodes in the beam path of the laser light coupled out of the decoupling region without the electrodes overheating. It is advantageous if the optically reflecting material is designed to reflect primarily radiation whose wavelength is in a range between 800 nm and 1500 nm. Heat radiation whose wavelength is outside this wavelength range is then just not reflected and a corresponding heating is avoided.

A suitable material with such optically reflective properties is barium sulfate (BaSO ₄ ). The optically reflective material should be in the mass fraction in a range of about 10% -40% barium sulfate. In this case, the optically reflective material can be mixed, for example, from granules and then extruded. In this case, barium sulfate is added to a base granulate, for example pebax, and then extruded. From the resulting extrusion, a granule is produced, which is used to extrude the catheter material in the decoupling region or in the adjoining region in its final form. The material with optically reflective properties then consists of a homogeneously mixed composite material (compound).

The electrodes can each penetrate or cover the decoupling region in part. In particular, at least one of the electrodes may be a ring electrode. The thermal effect is so low that overheating of the electrodes is avoided.

In the case of a light guide arranged in a groove in the outside of the catheter, whose coupling-out region runs in the groove, the groove can be provided with the optically reflective material. Alternatively, the optically reflective material may be adjacent to the groove, for example, where the catheter material has the optically reflective properties. The flanks of the groove are provided in this case with the optically reflective material and reflect the laser light through the decoupling region to the outside.

Advantageously, a temperature sensor is arranged below the electrode to measure the temperature in the decoupling region. The temperature sensor can serve to control the laser power temperature-dependent so that a certain temperature at the electrode is not exceeded.

It is particularly advantageous if the areas of the catheter adjacent to the decoupling area, such as, for example, the flanks of the groove of the decoupling area, are not provided, as conventionally, with a metallic coating for optical reflection. The metallic coating leads to a heat effect that could damage the electrodes. In the conventionally used metallic coating for reflection of the laser light from the decoupling region, it is not possible to arrange electrodes in the decoupling region due to the heat effect.

In the following an embodiment of the invention will be explained in more detail with reference to FIGS. Show it :

Fig. 1 is a schematic representation of the general structure of the optical fiber,

Fig. FIG. 2 shows a cross section along the line II-II in the middle section of FIG

Catheter according to FIG. 1,

Fig. FIG. 3 shows a cross section along the line III - III in the distal end section of FIG

Catheter according to FIG. 1,

Fig. 4 is a perspective view of the detail according to IV in FIG. 1 and

Fig. 5 is a top view of the catheter from the direction of the arrow V in FIG. 4.

The laser applicator has a catheter 10 in the form of an elongated strand. The catheter contains one or more lumens. It is preformed in the manner shown in Figure 1 and consists of a proximal portion 10a, a central portion 10b and a distal end portion 10c. While the sections 10a and 10b have a substantially rectilinear course, the distal end section 10c is formed into a loop forming a circle open at one point. The loop plane lies transversely, in particular at right angles, to the longitudinal direction the central portion 10b. It has such a size that it lays from the inside with slight pressure against the biological tissue to be ablated. The outer diameter of the loop is about 20 - 40mm.

The point A denotes the transition from the proximal portion 10a to the middle portion 10b. The point B indicates the transition from the central portion 10b into the distal end portion 10c.

Figure 2 shows a cross-section of the catheter in the central portion 10b. The catheter has a one-piece elongated catheter body 12 having a diameter of 1 to 4 mm, which has a substantially circular cross-section and is provided with a longitudinal, substantially V-shaped groove 13. The groove 13 has two outwardly diverging flanks 13a, 13b which are connected by an arcuate base 13c. The groove extends into the vicinity of the longitudinal central axis of the catheter body 12.

The catheter body 12 includes a lumen 14 for a forming wire. The lumen 14 is arranged diametrically opposite the groove 13. In addition, two longitudinal cooling channels 15, 16 are provided, which extend over the entire catheter length and are arranged symmetrically to the longitudinal median plane P, which forms a plane of symmetry and passes through the center of the lumen 14 and through the median plane of the groove 13. The catheter body 12 consists of a profile strand of uniform length over the length of an elastomeric material.

In the groove 13, a light guide 20 is inserted from the outside. This consists of a core 21 made of a glass fiber and a cladding 22 surrounding the core 21 made of a material having a higher refractive index than the core 21. The shell 22 is surrounded by a protective cover 23, which is a protection against breakage. The entire light guide 20 has a diameter such that it fits into the groove 13 without protruding beyond the circular contour of the catheter.

The light guide 20 is fixed in the groove 13 with a polymer 25 which fills the entire groove and has an outer surface corresponding to the circular contour of Catheter body corresponds. The polymer 25 is permeable to radiation. The catheter is coated on the outside with a transparent tube 26.

In the distal end portion 10c, the catheter has the cross section shown in FIG. It has a catheter body 12 a, which has the same profile as the catheter body 12 of the central portion. In the lumen 14 is a forming wire 30 which gives the distal end portion 10c the loop shape shown in Figure 1, but is elastic and can be stretched. Of the light guide 20, the protective cover 23 is removed in the distal end portion 10c. The optical fiber 20 has only the core 21 and the cladding 22 in the distal end portion. It is embedded in the groove, wherein the groove 13 is filled with a translucent material in the form of a polymer 33.

Also in the distal end region of the catheter is provided with a peripheral tube 26 a, which is translucent in this area.

In the distal end portion, not shown in the figures, cooling channels are provided with outlet holes, which converge to each other and send cooling jets to the outside. The exit holes are at an acute angle to each other. They cause the cooling jets to hit the target area of heat radiation. The exit holes have corresponding openings in the hose.

In the decoupling region 40 (FIG. 1), in which the radiation is coupled out of the optical waveguide 20, the cladding 22 of the optical waveguide is provided with openings 41, by means of which the radiation is decoupled from the core 21. The decoupling portion 40 is directed radially outward relative to the loop of the distal end portion. The plane of symmetry P (Figure 2) is in the plane of the loop.

The core 21 of the light guide 20 and the jacket 22 are continuous over the entire length of the catheter 10, so that the glass fiber of the light guide is not interrupted. The catheter bodies 12 and 12a are connected together at a catheter splice site 37. The umschläuche 26 and 26 a are at a Hose splice 38 connected to each other, which is spaced from the catheter splice site 37, in the present case, distal thereof.

In the manufacture of the laser applicator, the catheter bodies 12, 12a are first cut from the same tube profile. The material of the catheter body is homogeneously mixed with reflection particles or coated with reflection particles.

The light guide 20 is first processed outside of the catheter by sections, the protective cover 23 is removed. In this decoupling area, the openings 41 are produced by machining in the form of small holes. The thus prepared light guide is inserted into the lateral groove 13 of the catheter body 12 and then attached to the polymer 25. Then, the catheter body 12a is tightly connected to the catheter body 12 at the catheter splice site 37. Finally, the decoupling region of the light guide 20 is inserted into the lateral groove of the catheter body 12 a and the groove is filled with the polymer 33. The polymer 33 corresponds to the polymer 25.

Finally, the tubes 26 and 26a are applied to the respective catheter section.

The length of the decoupling region 40 in the longitudinal direction of the catheter is shown in FIG. 1 marked with the reference numeral 40. Along the Auskoppelbereichs 40 each ring electrodes 102, 104, 108, 110, 112, 114, 116 are arranged. The ring electrodes are characterized in that they are arranged completely circumferentially along the circumference of the laser applicator. Each of the ring electrodes can be covered with an electrical insulation 107, which releases the respective electrode in the region of the recess 40, so that the electrode, as shown in FIGS. 3 and 4, has an electrically conductive contact surface 106 in the region of the recess 40. With the aid of the measuring signals of the ring electrodes, the position of the decoupling region 40 in the longitudinal direction of the catheter and also in the circumferential direction with respect to tissue contacted by the electrodes can be determined. In addition, the electrodes are visible in the fluoroscopy and characterize the position of the decoupling region 40. At the distal end of the catheter, as shown in FIG. 5, a spherical cap-shaped absorber for the laser radiation emerging distally from the light guide 120 is provided. The absorber 120 forms a blunt end of the catheter.

In FIG. 3 it can be seen that a temperature sensor 36 which is covered to the outside by the electrode 110 is arranged between the polymer 33 filling the groove 13 and the ring electrode 110. With the temperature sensor 36, the temperature in the material 33 and in the decoupling region 40 can be determined. This temperature signal can be used to control laser power and control tissue ablation success.

Although an outlet opening 41 is shown below the ring electrode 110 in FIG. 3, it is premature if at least the majority of the outlet openings are formed in the area between the electrodes 102, 104, 108, 110, 112, 114, 116, while below the electrodes proportionately only a few or as possible no outlet openings are formed in order to reduce the laser power transmitted in the direction of the electrodes and the associated heating effect.

The material 33 in the groove 13 is a transparent polymer. The flanks 31 of the groove 13 are not provided along the decoupling region 40 with a reflective coating and in particular not with a metallic coating. Such reflective coatings cause considerable heating of the catheter surface and can thereby lead to overheating of the electrodes.

Instead of the conventionally used metallic coating, the catheter body 12a, at least in the region of the decoupling region 40, consists of a material which is homogeneously mixed with a material having optically reflective properties. This results in the region of the edges 31, an interface between the catheter material with optically reflective properties and the transparent groove material without optically reflective Properties. The optical reflection coefficient is thereby greater in the catheter material than in the groove material. By contrast, the material 33 in the groove 13 has greater transmission properties than the material of the catheter body 12a in the region of the decoupling region 40.

The laser light coupled out of the light guide 20 in the region of the decoupling region 40 is transmitted in the groove 13 and reflected at the boundary layer of the flank 13 due to the larger reflection coefficient of the optically reflective catheter body material. The reflection is not effected by a reflective, such as metallic coating of the flanks to avoid overheating of the electrode. The transparent groove material also causes a significantly lower heat effect compared to the conventional groove material with optically reflective properties.

As the catheter body material having optically reflective properties, barium sulfate (BaSO ₄ ) or titanium oxide may be used. The optically reflective material reflects in a wavelength range between 800 nm and 1500 nm, so that no heat radiation is reflected, thereby preventing overheating of the electrodes, while the laser light is reflected at the flanks 13. The material of the catheter body 12a is preferably mixed and extruded from granules of the material having optically reflective properties, with a mass fraction in the range of about 10-40% of the optically reflective material (BaS0 ₄ ) at the material making up the total volume of the material of the catheter 12a becomes . The remaining 60-90% of the catheter material is an extrudable material, such as polyurethane or nylon.

Barium sulfate or titanium oxide or other optically reflective materials are intended to serve as a homogeneous reflector for the wavelength of the laser light while heat radiation is not reflected to reduce the surface temperature of the catheter in the outcoupling region 40. Due to the reduced or possibly omitted light exit channels 41 below the electrodes, the lateral outcoupling of the laser light is reduced to below 40%, for example, in order to prevent overheating of the electrodes. Preferably, the electrode 102 is located exactly at the proximal end of the decoupling region 40, while the electrode 104 is disposed at the distal end of the decoupling region 40 to define the beginning and the end of the decoupling region and to allow a corresponding positioning of the decoupling region 40 in the longitudinal direction. The electrodes should be distributed equidistantly. The width of the electrodes in the longitudinal direction of the catheter can be between 0.5 and 1 mm. Alternatively, the electrodes may be placed in pairs at a minimum distance of 3mm between the electrodes.

The temperature sensor 36 is preferably a thin film temperature sensor in the form of a printed circuit that can be wrapped around the catheter surface by its flexibility. The temperature sensor 36 should have a maximum of 80% of the width of the electrode in the catheter longitudinal direction and a thickness in the radial direction of the catheter of a maximum of 150μη "".

Claims

claims

A laser applicator comprising an elongated catheter (10) containing at least one circumferentially closed lumen (14) and a light guide (20) extending along the catheter, having a decoupling region (40) for decoupling in a distal end portion (10c) of the catheter of laser light from the optical waveguide, characterized in that the laser applicator in the region of the decoupling region (40) at least one decoupling of the laser light-reducing electrode (102, 104, 108, 110, 112, 114, 116) to the position of the decoupling in With respect to surrounding tissue to be able to capture, and that the decoupling region (40) by a groove (13) formed in the outside of the catheter, wherein the light guide (20) in the groove (13) and extending adjacent to the groove material of the Catheter (10) in the decoupling region or in an adjoining region of a material with optically reflective properties homogeneous is mixed, and that the groove is filled with a transparent material (33).

2. Laserapplikator according to claim 1, characterized in that the flanks (31) of the groove (13) along the Auskoppelbereichs (40) are not provided with a reflective coating.

3. Laser applicator according to claim 1 or 2, characterized in that the groove (13) adjacent to the material of the catheter has an optical reflection coefficient which is greater than the optical reflection coefficient of the groove material (33).

4. Laser applicator according to one of the preceding claims, characterized in that the groove material (33) has an optical transmission coefficient which is greater than the optical transmission coefficient of the adjoining the groove material of the catheter (10).

5. Laser applicator according to one of the preceding claims, characterized in that the material with optically reflective properties to a predominant proportion of radiation reflects whose wavelength is in a range between 800 nm and 1500 nm.

6. Laser applicator according to one of the preceding claims, characterized in that the material with optically reflective properties to a mass fraction in a range of about 10% - 40% of barium sulfate (BaS0 ₄ ) consists.

7. Laser applicator according to claim 6, characterized in that the material with optically reflective properties consists of a homogeneously mixed composite material.

8. Laser applicator according to one of the preceding claims, characterized in that the electrodes are arranged in the decoupling region or penetrate the decoupling region in each case to a part or cover.

9. Laser applicator according to one of the preceding claims, characterized in that the electrodes are ring electrodes.

10. Laser applicator according to one of the preceding claims, characterized in that the groove is substantially V-shaped.

11. Laser applicator according to one of the preceding claims, characterized in that between at least one of the electrodes and the catheter (10) or the decoupling region (40), a temperature sensor which is adapted to measure the temperature in the decoupling region, is arranged. Laser applicator according to one of the preceding claims, characterized in that no metallic coating is used in a region adjacent to the decoupling region (40).