Catheter for high-power focal ablation

Abstract

To provide a medical apparatus.SOLUTION: The medical apparatus includes a flexible insertion tube, which has a first outer diameter and has a distal end configured for insertion into a cavity within a body of a patient. A rigid cylindrical electrode is fixed to the distal end of the flexible insertion tube, is configured to contact tissue within the cavity, and has a second outer diameter that is at least 10% greater than the first outer diameter.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention generally relates to invasive medical devices, and more specifically, to ablation catheters and methods of using the same.

Background Art

[0002] Cardiac radiofrequency (RF) ablation is widely used to correct cardiac arrhythmias such as atrial fibrillation. Ablation procedures typically involve inserting a catheter having one or more electrodes at its distal end into the heart and applying RF energy to one or more electrodes to ablate a selected area within the heart. For this purpose, various types of catheters can be used. As an example, the QDOT MICRO® catheter manufactured by Biosense Webster (Irvine, California) enables ablation at up to 90 watts of RF power for up to 4 seconds in a temperature-controlled ablation mode.

[0003] Such a catheter is described, for example, in U.S. Patent No. 10,517,667, the disclosure of which is incorporated herein by reference. The catheter comprises an insertion tube having a distal tip configured to act as an electrode for ablation. Typically, the distal tip, which is generally formed in a cup-like shape, has at least one cavity formed on its outer surface. For each cavity, there is a respective microelectrode configured to fit within the cavity, and the outer surface is contoured to conform to the outer surface of the distal tip. Typically, the microelectrodes are insulated from the distal tip, such that the microelectrodes can detect body-generated potentials with high spatial resolution, independent of the far-field signals picked up by the larger distal tip.

[0004] High-power focal ablation catheters may include means for irrigating an electrode region. For example, U.S. Patent Application Publication 2018 / 0104000, whose disclosure is incorporated herein by reference, describes a medical probe having at least one distal electrode coupled to an energy source for applying energy to tissue in the body. Multiple openings are formed within the electrode. A fluid directionation assembly located in the distal section of the probe has an axial passage, which is in fluid communication with at least one transaxial passage located perpendicular to the axial passage and leads to the outside of the assembly. A blocking termination located forward of the at least one transaxial passage prevents the irrigation fluid from flowing axially forward, thereby causing the fluid to flow outward in at least one transaxial direction into the lumen of the electrode and out of the electrode through the openings.

[0005] The distal end of an ablation catheter may also include other types of sensors. For example, U.S. Patent Application Publication 2019 / 0117298, whose disclosure is incorporated herein by reference, describes a medical probe comprising an insertion tube having a distal end configured to be inserted into a patient's body and containing a lumen having a conductor for transmitting electrical energy. The probe also has a conductive cap attached to the distal end of the insertion tube and electrically coupled to the conductor. The cap includes a side wall having a plurality of longitudinal bores inside. The plurality of thermocouples are arranged in the longitudinal bores, and a conductive cement fills at least partially the longitudinal bores to fix the thermocouples in place within the bores, while forming conductive contact between the thermocouples and the conductive cap. [Overview of the Initiative] [Means for solving the problem]

[0006] The embodiments of the present invention described below provide improved catheters and methods for their manufacture and use.

[0007] Accordingly, according to one embodiment of the present invention, a medical device is provided comprising a flexible insertion tube having a first outer diameter and a distal end configured to be inserted into a lumen in the patient's body. A rigid cylindrical electrode is fixed to the distal end of the flexible insertion tube and configured to contact the tissue in the lumen, and has a second outer diameter at least 10% larger than the first outer diameter.

[0008] In the disclosed embodiments, the second diameter is at least 20% larger than the first outer diameter. Additionally or alternatively, the second outer diameter is at least 3 mm. Further additionally or alternatively, the rigid cylindrical electrode has a rounded distal edge.

[0009] In some embodiments, the apparatus includes a conductor that passes through a flexible insertion tube and is configured to apply radio frequency (RF) electrical energy to a rigid cylindrical electrode with sufficient power to ablate the tissue. In the disclosed embodiments, the power of the RF electrical energy applied to the electrode by the conductor is at least 100 W.

[0010] Additionally or alternatively, a rigid cylindrical electrode includes an outer wall containing a central volume and having an opening formed through the outer wall that communicates with the central volume, and the device includes a lumen through which a flexible insertion tube passes and is coupled to supply fluid to the central volume, thereby the fluid exiting through the opening to irrigate tissue. In the disclosed embodiment, the lumen is configured to introduce fluid into the central volume along the axial direction, and the device includes a flow diverter positioned within the central volume of the cylindrical electrode and configured to radially deflect the fluid toward the opening.

[0011] In some embodiments, a rigid cylindrical electrode includes a distal surface and a side surface, with a circular rim between the distal surface and the side surface, and the distal surface includes a plurality of elongated grooves extending radially outward at different azimuthal angles through the rim across the peripheral region of the distal surface, and the device includes a plurality of sensors positioned within the elongated grooves to contact the tissue contacted by the rigid cylindrical electrode. In one embodiment, the sensor includes a sensing electrode, the sensing electrode being configured to detect an electrophysiological signal generated by the tissue in contact with the sensing electrode. Additionally or alternatively, the circular rim has a rounded contour extending between the distal surface and the side surface, and the sensors are sized and molded to fit into the elongated grooves such that the outer surface of each sensor is coplanar with the distal surface and coplanar with the rounded contour of the circular rim.

[0012] According to embodiments of the present invention, a method of treatment is further provided, which includes inserting a catheter into the ventricle of a patient's heart and bringing an electrode at the distal end of the catheter into contact with tissue within the heart. To ablate the tissue, radio frequency (RF) electrical energy is applied to the electrode through the catheter with a power of at least 100 W.

[0013] The present invention will be better understood from the following detailed description of its embodiments, along with the drawings. [Brief explanation of the drawing]

[0014] [Figure 1] This is a schematic view of the distal end of an ablation catheter according to one embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view of the distal tip of the catheter shown in Figure 1, according to an embodiment of the present invention. [Modes for carrying out the invention]

[0015] High-power focal ablation using devices such as the QDOT microcatheter described above has been found to be therapeutically advantageous, particularly because this approach significantly reduces the time required to perform the procedure. As used herein, the term “focal ablation” refers to the application of energy to tissue within the body, such as myocardial tissue, at a single location. Focal ablation typically uses a single electrode at the tip of a catheter or other probe, rather than ablating a range of locations using probes with multi-electrode distal assemblies such as baskets, balloons, or lasso assemblies simultaneously. Using a QDOT microcatheter with 90W of RF power, single-location focal ablation can be achieved in as little as 4 seconds.

[0016] It would be desirable to have the ability to create deeper lesions and further shorten ablation time by using higher levels of RF power. Shorter ablation times also reduce the likelihood of the ablation electrode shifting or losing contact with the myocardium during ablation. However, power delivery in focal catheters known in the art is also limited by the diameter of the catheter tip electrode, as excessive power can cause overheating of the catheter tip and body tissue and lead to lesions. Subsequently, the electrode diameter has been limited to the diameter of the catheter insertion tube, and the lesion depth of focal catheters known in the art is limited to about 3-4 times the tip diameter due to the biophysics of RF ablation. The diameter of the insertion tube is typically in the range of 2.5 mm, allowing the catheter to be easily inserted into the heart through the patient's vascular system. Thus, RF ablation power is practically limited to levels below 100 W, and the lesion depth is limited to less than 10 mm.

[0017] Embodiments of the present invention described herein overcome these limitations by providing devices such as cardiac catheters, where the rigid cylindrical electrode has an outer diameter at least 10% larger than the outer diameter of the flexible insertion tube to which the electrode is fixed at its distal end. In some embodiments, the electrode diameter is at least 20% larger than the insertion tube diameter. In typical cardiac ablation applications, this criterion means that the outer diameter of the rigid cylindrical electrode is 3 mm or more. These increases in dimensions allow the volume of the tip electrode to be 50-100% larger than the volume of catheters known in the art, thus supporting the application of RF ablation power exceeding 100 W and producing deeper ablation lesions. However, given the moderate increase in electrode size, it is still possible to non-traumatically manipulate the catheter through the patient's vascular system into the heart.

[0018] Figure 1 is a schematic view of the distal end of an ablation catheter 20 according to one embodiment of the present invention. The catheter 20 comprises a flexible insertion tube 22, the distal end of which is configured to be inserted into a cavity in the patient's body, such as the ventricle of the heart. A rigid cylindrical electrode 24 is fixed to the distal end of the insertion tube 22 and configured to contact the tissue in the cavity. In the illustrated example, the outer diameter of the electrode 24 is approximately 3.7 mm, which is more than 20% larger than the outer diameter of the insertion tube 22, which is less than 3 mm.

[0019] The electrode 24 contains a suitable biocompatible metal such as gold. The electrode is formed as a cylinder with a rounded edge, comprising a flat distal surface 26 and rounded sides 28, with a circular edge 30 between surfaces 26 and 28. The edge 30 has a rounded contour similar to, for example, the contour of the distal tip of the catheter described in U.S. Patent No. 10,517,667. The irrigation opening 32 passes through the outer shell of the electrode 24, allowing an irrigation fluid, such as saline solution, to exit through the opening and irrigate the tissue in contact with the electrode. Details of this irrigation mechanism are shown in Figure 2.

[0020] The distal surface 26 of the electrode 24 includes a number of elongated grooves 34 that extend radially outward at different azimuthal angles across the peripheral region of the distal surface, passing through the edge 30 to the side surface 28. ("Azimuthal angle" refers to the angle of rotation about the longitudinal axis of the catheter 20, and the radial direction is perpendicular to this axis in the plane of the distal surface 26. "Peripheral region" refers to the region adjacent to the edge 30, as opposed to the central region adjacent to the longitudinal axis. A groove is "elongated" in the sense that its radial length is at least twice its azimuthal width.) In this embodiment, the electrode 24 includes three grooves 34 located 120° apart. Alternatively, the electrode may include more or fewer such grooves.

[0021] The sensing electrode 36 is fitted into an elongated groove 34, but is electrically insulated from the metal body of the electrode 24. The sensing electrode 36 contacts the tissue that is in contact with the electrode 24, and therefore detects the electrophysiological signals generated by the tissue in contact with the sensing electrode. These signals provide an indicator of local electrical activity in the tissue before, after, and even during the ablation procedure. Alternatively or additionally, other types of sensors, such as thermocouples, can be fitted into the groove 34 and at other positions within the body of the electrode 24. The sensing electrode 36 itself is elongated, and is sized and shaped to fit into the groove 34 such that the outer surface of each sensing electrode 36 is coplanar with the distal surface 26 and the rounded contour of the circular edge 30. This coplanar configuration is useful for creating a non-traumatic tip, ensuring uniform electrical contact, and avoiding electrical hot spots and arc discharges.

[0022] Catheter 20 can be used for intracardiac ablation with increased RF power levels, for example, as an alternative to the catheter described in U.S. Patent No. 10,517,667 and U.S. Patent Application Publication No. 2018 / 0104000 and U.S. Patent Application Publication No. 2019 / 0117298. When catheter 20 is inserted into the ventricle of the patient's heart and the electrode 24 is in contact with tissue within the heart, RF electrical energy can be applied through the catheter to the electrode with a power of at least 100 W to ablate the tissue. The systems described in U.S. Patent No. 10,517,667 and U.S. Patent Application Publication No. 2018 / 0104000 and U.S. Patent Application Publication No. 2019 / 0117298 include an RF generator, an irrigation pump, and a sensing circuit, which can also be applied, with necessary modifications, to drive, irrigate, and receive signals from catheter 20. U.S. Patent Application Publication No. 2018 / 0104000 and U.S. Patent Application Publication No. 2019 / 0117298 also describe a temperature sensor, a contact force sensor, and a position sensor that can similarly be integrated into the distal end of the catheter 20. However, these additional sensors are omitted herein for the sake of brevity.

[0023] Figure 2 is a schematic cross-sectional view of the distal tip of the catheter 20 along line II-II in Figure 1, according to one embodiment of the present invention. As can be seen from this figure, the electrode 24 is connected to receive RF ablation energy via a conductor 40 that passes through the insertion tube 22 to a control console, as shown in the aforementioned U.S. Patent and U.S. Patent Application. (In the illustrated embodiment, for example, the conductor 40 is electrically and mechanically fixed by soldering to a cylindrical distal space in the flow diverter 50.) As previously stated, the conductor 40 can transmit RF energy to the electrode 24 with at least 100 W of power, sufficient to rapidly ablate the tissue contacted by the electrode. The sensing electrode 36 is similarly connected to sense the circuit in the console by a wire 42 that passes through the insertion tube 22.

[0024] The rigid cylindrical electrode 24 includes an outer wall 44 that surrounds and houses a central volume 46. A lumen 48 that passes through the flexible insertion tube 22 supplies fluid axially to the central volume 46. The fluid exits the central volume 46 through an opening 32 and perfuses the tissue proximate to the electrode 24. A flow diverter 50 within the central volume 46 deflects the fluid entering through the lumen 48 radially toward the opening 32, ensuring a uniform dispersion of the fluid throughout the region surrounding the electrode 24. The opening 32 itself is angled to improve fluid dispersion. Further features of this configuration for tissue perfusion are described in U.S. Patent Application Publication No. 2018 / 0104000, cited above.

[0025] In some embodiments, the catheter 20 also has temperature sensing capabilities. For this purpose, a temperature sensor 52, such as a thermocouple, is inserted into a bore 54 within the electrode 24. An elastic bending rod 56 holds the temperature sensor 52 in place, and the temperature sensor faces the outer surface of the electrode 24, ensuring reliable measurements. In the embodiment shown in FIG. 2, each bore 54 includes two temperature sensors 52 at different axial positions.

[0026] It will be understood that the embodiments described above are given by way of example only, and that the invention is not limited to those specifically illustrated and described hereinabove. Rather, the scope of the invention includes both combinations and sub - combinations of the various features described in the foregoing specification, as well as variations and modifications thereof not disclosed in the prior art that would be contemplated by a person skilled in the art upon reading the foregoing description.

[0027] 〔Embodiments〕 (1) A medical device, a flexible insertion tube having a distal end configured to be inserted into a lumen within a patient's body and having a first outer diameter, a rigid cylindrical electrode fixed to the distal end of the flexible insertion tube and configured to contact tissue within the lumen, the rigid cylindrical electrode having a second outer diameter that is at least 10% larger than the first outer diameter, comprising a medical device. (2) The apparatus according to Embodiment 1, wherein the second diameter is at least 20% larger than the first outer diameter. (3) The apparatus according to Embodiment 1, wherein the second outer diameter is at least 3 mm. (4) The apparatus according to Embodiment 1, wherein the rigid cylindrical electrode has a rounded distal edge. (5) The apparatus according to Embodiment 1, comprising a conductor that passes through the flexible insertion tube and is configured to apply radio frequency (RF) electrical energy to the rigid cylindrical electrode with sufficient power to ablate the tissue.

[0028] (6) The apparatus according to Embodiment 5, wherein the power of the RF electrical energy applied to the electrode by the conductor is at least 100 W. (7) The apparatus according to Embodiment 1, wherein the rigid cylindrical electrode has an outer wall containing a central volume and an opening formed through the outer wall that communicates with the central volume, and the apparatus has a lumen that passes through the flexible insertion tube and is coupled to supply fluid to the central volume, thereby the fluid exits through the opening to irrigate the tissue. (8) The apparatus according to Embodiment 7, wherein the lumen is configured to introduce the fluid into the central volume along the axial direction, and the apparatus is positioned within the central volume of the cylindrical electrode and is configured to deflect the fluid radially toward the opening, comprising a flow diverter. (9) The rigid cylindrical electrode comprises a distal surface and a side surface, with a circular edge between the distal surface and the side surface, and the distal surface includes a plurality of elongated grooves extending radially outward at different azimuthal angles through the edge and across the peripheral region of the distal surface, The apparatus according to Embodiment 1, further comprising a plurality of sensors arranged in the elongated groove so as to contact the tissue that is in contact with the rigid cylindrical electrode. (10) The apparatus according to embodiment 9, wherein the sensor comprises a sensing electrode, the sensing electrode being configured to detect an electrophysiological signal generated by the tissue in contact with the sensing electrode.

[0029] (11) The apparatus according to Embodiment 9, wherein the circular edge portion has a rounded contour extending between the distal surface and the side surface, and the sensor is sized and molded to fit into the elongated groove such that each outer surface of the sensor is coplanar with the distal surface and coplanar with the rounded contour of the circular edge portion. (12) A method of treatment, Inserting a catheter into the ventricle of the patient's heart and bringing the electrode at the distal end of the catheter into contact with the tissue inside the heart, In order to ablate the tissue, radio frequency (RF) electrical energy is applied to the electrode through the catheter with a power of at least 100W, Methods that include... (13) The method according to embodiment 12, wherein the catheter comprises a flexible insertion tube having a first outer diameter, and the electrode comprises a rigid cylindrical electrode fixed to the distal end of the flexible insertion tube and having a second outer diameter at least 10% larger than the first outer diameter. (14) The method according to embodiment 13, wherein the second diameter is at least 20% larger than the first outer diameter. (15) The method according to embodiment 13, wherein the second outer diameter is at least 3 mm.

[0030] (16) The method according to embodiment 13, wherein the rigid cylindrical electrode has a rounded distal edge. (17) The method of Embodiment 12, comprising supplying a fluid through an opening in the electrode to irrigate the tissue. (18) The method according to Embodiment 17, wherein supplying the fluid includes introducing the fluid through the lumen of the catheter into the central volume of the electrode along the axial direction, and applying a flow diverter within the central volume to deflect the fluid radially toward the opening. (19) The method according to Embodiment 12, comprising using a plurality of elongated sensors extending radially outward at different azimuthal angles over a peripheral region of the electrode to detect electrophysiological signals generated by the tissue.

Claims

1. It is a medical device, A flexible insertion tube having a first outer diameter and a distal end, A rigid cylindrical electrode is fixed to the distal end of the flexible insertion tube, configured to contact the tissue within the cavity when the medical device is inserted into the cavity in the patient's body, and having a second outer diameter at least 10% larger than the first outer diameter, A catheter equipped with, The rigid cylindrical electrode comprises a distal surface and a side surface, with a circular rim between the distal surface and the side surface, and the distal surface includes a plurality of elongated grooves extending radially outward at different azimuthal angles through the circular rim across the peripheral region of the distal surface. The medical device comprises a plurality of sensors arranged in the elongated groove so as to contact the tissue that is in contact with the rigid cylindrical electrode.

2. The medical device according to claim 1, wherein the second outer diameter is at least 20% larger than the first outer diameter.

3. The medical device according to claim 1, wherein the second outer diameter is at least 3 mm.

4. The medical device according to claim 1, wherein the circular edge defines the rounded distal edge of the rigid cylindrical electrode.

5. The medical device according to claim 1, comprising a conductor that passes through the flexible insertion tube and is configured to apply radio frequency (RF) electrical energy to the rigid cylindrical electrode with sufficient power to ablate the tissue.

6. The medical device according to claim 5, wherein the power of the RF electrical energy applied to the rigid cylindrical electrode by the conductor is at least 100 W.

7. The medical device according to claim 1, wherein the rigid cylindrical electrode has an outer wall containing a central volume and has an opening formed through the outer wall that communicates with the central volume, and the medical device has a lumen that passes through the flexible insertion tube and is coupled to supply fluid to the central volume, thereby the fluid exits through the opening to irrigate the tissue.

8. The medical device according to claim 7, wherein the lumen is configured to introduce the fluid into the central volume along the axial direction, and the medical device comprises a flow diverter positioned within the central volume of the rigid cylindrical electrode and configured to deflect the fluid radially toward the opening.

9. The medical device according to claim 1, wherein the sensor comprises a sensing electrode, and the sensing electrode is configured to detect an electrophysiological signal generated by the tissue in contact with the sensing electrode.

10. The medical device according to claim 1, wherein the circular edge portion has a rounded contour extending between the distal surface and the side surface, and the sensor is sized and molded to fit into the elongated groove such that each outer surface of the sensor is coplanar with the distal surface and coplanar with the rounded contour of the circular edge portion.

11. The medical device according to claim 1, wherein the volume of the rigid cylindrical electrode having the second outer diameter is 50 to 100% larger than the volume when the rigid cylindrical electrode has the first outer diameter.

12. The medical device according to claim 1, wherein the second outer diameter is 3 mm to 3.7 mm.

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