Catheter system for cryoablation of the vagus nerve

Abstract

A catheter system for cryoablation of the stomach, comprising: a catheter and at least one inflatable cryoballoon which is fastened to the catheter and exhibits a contact curve along which the cryoballoon can be brought into contact with the fundus, wherein the contact curve is a closed curve on the surface of the cryoballoon, and the cryoballoon contains a first cooling arrangement which extends along less than three quarters of the length of the contact curve.

Claims

1. A catheter system for cryoablation of a stomach, comprising: a catheter and at least one inflatable cryoballoon which is fastened to the catheter that exhibits a contact curve along which the at least one inflatable cryoballoon can be brought into contact with a fundus, wherein the contact curve is a closed curve on a surface of the at least one inflatable cryoballoon, and the at least one inflatable cryoballoon contains a first cooling arrangement which extends along less than three quarters of a length of the contact curve, and wherein a proximal end of the at least one inflatable cryoballoon comprises a region in which the contact curve extends and a cross-sectional area of the at least one inflatable cryoballoon increases continuously from the proximal end to a distal end.

2. The catheter system according to claim 1, wherein the at least one inflatable cryoballoon comprises two measuring electrodes which are arranged on its surface on different sides of the contact curve.

3. The catheter system according to claim 2, further comprising evaluation electronics configured to measure the impedance between the two measuring electrodes.

4. The catheter system according to claim 1, wherein the at least one inflatable cryoballoon exhibits a shape of at least a part of the fundus.

5. The catheter system according to claim 1, wherein the first cooling arrangement extends over at most half the length of the contact curve.

6. The catheter system according to claim 1, wherein the first cooling arrangement comprises at least one Peltier element.

7. The catheter system according to claim 1, wherein the first cooling arrangement is a cooling conduit for a cooling medium, and the catheter contains at least one conveying conduit connected to the cooling conduit, for the cooling medium.

8. The catheter system according to claim 1, wherein the at least one inflatable cryoballoon contains a second cooling arrangement that extends along the contact curve in a region which is not occupied by the first cooling arrangement.

9. The catheter system according to claim 1, wherein the at least one inflatable cryoballoon comprises at least one radiopaque marker.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention shall be described in more detail on the basis of specific example embodiments. The corresponding figures, which are not to scale, show:

(2) FIG. 1 is a schematic view of a stomach and the vagus nerve;

(3) FIG. 2 is the schematic view of FIG. 1, featuring a catheter system comprising a cryoballoon in accordance with a first embodiment;

(4) FIG. 3 is the schematic view of FIG. 1, featuring a catheter system comprising a cryoballoon in accordance with a second embodiment;

(5) FIG. 4 is a schematic view of the stomach, featuring a contact curve, two measuring electrodes and evaluation electronics;

(6) FIG. 5 is a schematic view of the structure of a cryoballoon;

(7) FIG. 6 is a second schematic view of the structure of the cryoballoon;

(8) FIG. 7 is a schematic view of a third embodiment of a cryoballoon; and

(9) FIG. 8 is a schematic view of a fourth embodiment of a cryoballoon.

DETAILED DESCRIPTION

(10) FIG. 1 shows a schematic view of a stomach 1. The upper region of the stomach 1, into which the oesophagus 2 emerges, is referred to as the fundus 3. FIG. 1 also schematically shows the anterior vagal trunk (truncus vagus anterior) 4a and the posterior vagal trunk (truncus vagus posterior) 4b which together form a part of the vagus nerve (Nervus vagus) 4. The two trunks 4a and 4b of the nerve extend in the body in front of and behind the stomach 1, respectively.

(11) FIG. 2 shows the schematic view of the stomach 1 from FIG. 1, featuring a catheter system in accordance with a first embodiment. The catheter system consists of a catheter 5, the distal end of which can be inserted up to and into the fundus 3 via the oesophagus 2, wherein the proximal end of the catheter 5 (not shown) remains outside the body.

(12) A cryoballoon 6 is arranged at the distal end of the catheter 5. It is inflatable and is introduced, while deflated, into the fundus 3 together with the distal end of the catheter 5. The cryoballoon 6 and the distal end of the catheter 5 can for example be introduced into the fundus 3 directly or through the working channel. The cryoballoon 6 can be arranged at the distal end of the catheter 5 or at a distance of up to 5 or 10 cm.

(13) FIG. 2 shows a cryoballoon 6a, as part of the catheter system, exhibiting the shape of the fundus 3.

(14) A filling conduit (not shown in the figures) extends within the catheter 5 and is connected to the interior of the cryoballoon 6. A filling medium such as air or a liquid, for example a saline solution, can be introduced into the cryoballoon 6a from outside the body via the filling conduit, such that the cryoballoon 6 is inflated.

(15) Due to its shape, the cryoballoon 6a automatically aligns in a predetermined position within the fundus 3. This results in a contact line 7a between the balloon 6a and the wall of the stomach 1. The contact curve 7a is a closed curve.

(16) FIG. 3 shows the schematic view of FIG. 1, featuring a catheter system comprising a cryoballoon 6b of a second embodiment. The cryoballoon 6b does not exhibit a shape adapted to the fundus 3 but rather a generic shape such as for example a spherical shape or a rotationally symmetrical shape having an oval or elliptical cross-section. The cryoballoon 6b abuts the wall of the stomach 1 along the contact curve 7b.

(17) It should be noted that a cryoballoon 6 usually abuts the wall of the stomach 1 not just linearly along the contact curve 7 but rather over an area in a region of the surface of the cryoballoon 6 in which the contact curve 7 extends. In this document, the reference sign 6 describes a cryoballoon shaped in any way, and the reference sign 7 describes a contact curve shaped in any way, while additional letters relate to a particular embodiment.

(18) If the contact curve 7 is circular, it has a diameter of for example 5 to 7 cm. When inflated, the cryoballoon 6 has a volume of for example 400 to 500 ml. A typical diameter of a spherical cryoballoon or a rotationally symmetrical cryoballoon having an oval or elliptical cross-sectional area is for example 10 cm.

(19) FIG. 4 shows a schematic view of the stomach 1, featuring a contact curve 7, two measuring electrodes 8a and 8b and evaluation electronics 9. By means of the measuring electrodes 8, the evaluation electronics 9 ascertain the impedance of the tissue between the electrodes 8a and 8b.

(20) FIG. 5 shows a schematic view of an example structure of a cryoballoon 6. A first cooling arrangement 10, which in the present example is a cooling conduit, extends along the contact curve 7. It can however also be any other type of cooling arrangement, for example one or more Peltier elements.

(21) The cooling arrangement 10 is arranged on or directly below the surface of the cryoballoon 6 and extends over less than three quarters of the length of the contact curve 7. This means that the cooling arrangement does not cool the entire circumference of the contact region between the cryoballoon 6 and the wall of the stomach 1 but rather only a part of the circumference, such that for example each of the trunks 4a and 4b of the vagus nerve 4 can be cooled separately.

(22) By means of a conveying conduit 11, a cooling medium flows through the cooling conduit 10. The conveying conduit 11 extends within the catheter 5 or along the outer sleeve of the catheter 5 and is for example connected to a reservoir (not shown) for the cooling liquid. A second conveying conduit is optionally provided via which the cooling liquid is conveyed out of the cryoballoon 6, such that this results in a closed circulation for the cooling liquid.

(23) FIG. 5 shows the location of the two measuring electrodes 8a and 8b. They lie on the surface of the cryoballoon 6, on different sides on the contact curve 7. One of the measuring electrodes lies inside the contact curve 7, and one outside. The two measuring electrodes 8a and 8b preferably lie opposite each other with respect to the contact curve 7, for example on a straight line perpendicular to the contact curve 7. The distance between the two electrodes 8a and 8b and the contact curve 7 is for example identical.

(24) In the representation of FIG. 5, the cryoballoon 6 is not arranged at the distal end of the catheter 5 but rather at a distance from it. A part 5a of the catheter 5 thus protrudes beyond the inflated cryoballoon 6. This simplifies inserting the catheter 5.

(25) In one embodiment in which the cryoballoon 6 is not arranged at the distal end of the catheter 5 but rather at a distance from it, the cryoballoon 6 preferably surrounds the entire circumference of the catheter 5, such that the cryoballoon 6 can form a closed contact curve 7 with the wall of the stomach 1.

(26) Contrary to FIG. 5, FIG. 6 shows a schematic plan view onto the cryoballoon 6. As can be seen from FIG. 6, the cooling arrangement 10 extends along less than three quarters of the length of the contact curve 7. In the present example, the first cooling arrangement 10 extends along half the contact curve.

(27) The conveying conduits 11a and 11b are also shown, wherein each of the conveying conduits 11 is connected to a different end of the cooling conduit 10. The cooling liquid is conveyed through the conveying conduit 11a into the cooling conduit 10 and out of the cooling conduit 10 via the conveying conduit 11b. The continuous flow of the cooling medium through the cooling conduit 10 enables continuous ablation of the vagus nerve.

(28) FIG. 6 also shows that the cryoballoon 6 bears optional markers 12a and 12b on its surface. The markers 12 are radiopaque and thus identifiable in medical images based on X-ray radiation such as X-ray images or CT images. The position and/or alignment of the cryoballoon 6, and therefore the first cooling arrangement 10, within the stomach 1 can be detected on the basis of the markers 12. The cryoballoon 6 can in particular be navigated to a desired position. The size of the cryoballoon 6 can also be calculated from the distances between the markers 12. It is then for example possible to stop inflating the cryoballoon 6 as soon as the distance between two defined markers 12 reaches a defined limit value.

(29) FIG. 6 shows two markers 12; the cryoballoon 6 can however also contain fewer or more markers, for example 3, 4, 5 or 6 markers.

(30) FIG. 7 shows a schematic view of a third embodiment of the cryoballoon, in the form of the cryoballoon 6c. The cryoballoon 6c has a basically cuboidal shape in which one of the shortest edges has been removed by a section comprising a plane. The contact curve 7 lies on the sectional area, and the first cooling element 10 lies directly below that.

(31) The distance 13 between the first cooling arrangement 10 and the smallest non-sectioned rectangle of the cuboid is for example 3 to 5 cm, in particular 4 cm. The distance 14 between the catheter 5 and the smallest sectioned rectangle of the cuboid is for example 0.5 to 1.5 cm, in particular 1 cm.

(32) This shape of the cryoballoon 6c, which is connected eccentrically to the catheter 5, approximately replicates the shape of the fundus 3, but is easier to manufacture than a cryoballoon which exactly replicates the shape of the fundus 3. Approximately replicating the shape of the fundus 3 is sufficient in order to simplify positioning the cryoballoon 6 within the stomach 1.

(33) FIG. 8 shows a schematic view of a fourth embodiment of the cryoballoon, in the form of the cryoballoon 6d. The shape of the cross-sectional area of the cryoballoon 6d is reniform, but mirror-symmetrical with respect to the axis A in FIG. 8.

(34) The first cooling arrangement 10 lies on one side of the plane of symmetry A, completely within one half of the cryoballoon 6d. The cryoballoon 6d also comprises a second cooling arrangement 10a in the form of a cooling conduit which in the present example likewise consists of a cooling conduit connected to conveying conduits 11c and 11d through which a cooling medium can be fed to the cooling conduit 10a and drained from the cooling conduit 10a again. The second cooling conduit 10a is situated completely on the other side of the cryoballoon 6d with respect to the plane of symmetry A. It should be noted that a second cooling arrangement 10a such as is shown in FIG. 8 can be combined with any other embodiments of the cryoballoon 6. If there are multiple cooling arrangements, different types of cooling arrangements can be combined with each other. One cooling arrangement can then for example be a cooling conduit, and one cooling arrangement can be one or more Peltier elements.

(35) The measuring electrodes 8a and 8b are arranged on both sides of the first cooling arrangement 10. The two measuring electrodes 8c and 8d are also arranged on both sides of the second cooling arrangement 10a. All the measuring electrodes 8a to 8d are connected to the evaluation electronics 9 in order to measure the impedance of the tissue between the pair of measuring electrodes 8a and 8b and the pair of measuring electrodes 8c and 8d, respectively. Depending on the progress of ablation in the two regions, the operation of the corresponding cooling arrangement can be controlled independently of the operation of the other cooling arrangement.

(36) In a modification of this embodiment, the two cooling conduits 10 and 10a can also be connected to each other and thus form a complete ring along the entire length of the contact curve 7. In this case, at least two of the conveying conduits are optional. Likewise, only two of the measuring electrodes 8 are required, i.e. this embodiment has at least two measuring electrodes and a cooling arrangement which extends along the entire length of the contact curve 7, wherein it can also be a single cooling arrangement. This enables circumferential ablation, the progress of which can be tracked via the measuring electrodes 8 and the evaluation electronics 9.

(37) When using a catheter system in accordance with the invention, the distal end of the catheter 5 is inserted, together with the deflated cryoballoon 6, into the fundus 3 of the stomach 1. The cryoballoon 6 is then inflated, for example by filling it with a filling medium through a filling conduit which extends on or in the catheter 5. The catheter 5 is then retracted, together with the inflated cryoballoon 6, in the proximal direction until the cryoballoon 6 abuts the wall of the stomach 1 along the contact curve 7, wherein the cryoballoon 6 is aligned, for example by observing the markers 12 by means of X-ray radiation, such that the first cooling arrangement abuts the region of the wall of the stomach 1 which is to be cooled. The region to be cooled is either an anterior region of the stomach, for ablating the anterior vagal trunk, or a region on the posterior gastric wall, for ablating the posterior vagal trunk.

(38) The progress of ablation can be controlled by an impedance measurement by means of the measuring electrodes 8 and the evaluation electronics 9. If the measured impedance exceeds a predetermined limit value, then ablation is assumed to be complete.

(39) Once one trunk of the vagus nerve has being ablated, the cryoballoon 6 can be realigned, for example around the longitudinal axis of the catheter 5, such that the other trunk of the vagus nerve can be ablated.

(40) Multiple ablations can be performed in sequence by advancing and retracting the cryoballoon 6. The fill level of the cryoballoon is optionally altered between two ablations, in order to adapt the contact curve 7.

(41) Once ablation is complete, the cryoballoon 6 is deflated, for example by siphoning or bleeding the filling medium inside of the cryoballoon 6. The catheter 5 can then be removed, together with the cryoballoon 6, from the stomach 1.

(42) In an alternative application, ablation is performed not just on a part of the vagus nerve 4, but rather circumferential ablation is performed along the entire contact curve 7. The sequence for this is similar to that of partial ablation; aligning the cryoballoon around the axis of the catheter 5 is however optional, particularly if the cryoballoon is a rotationally symmetrical cryoballoon 6. Within the framework of the disclosure, the measuring electrodes 8a and 8b and the evaluation electronics 9 are however not optional in the case of circumferential ablation.