阅读说明：本技术 具有冷却的电穿孔 (Electroporation with cooling ) 是由 A·戈瓦里 C·T·贝克勒 K·J·赫雷拉 于 2021-06-10 设计创作，主要内容包括：本发明题为“具有冷却的电穿孔”。本发明公开了一种医疗系统,所述医疗系统包括导管,所述导管包括：具有远侧端部的插入管；固定到所述插入管的所述远侧端部的细长弹性远侧节段,所述远侧节段具有外表面；和多个电极结构,每个电极结构设置在所述远侧节段的所述外表面上并且从所述远侧节段的所述外表面上凸出,每个电极结构包括围绕所述外表面延伸的相应初级电极和至少一个相应次级电极,以及围绕所述外表面设置并且位于所述相应初级电极和所述至少一个相应次级电极之间的相应电绝缘材料,所述相应初级电极从所述外表面上凸出的程度大于所述至少一个相应次级电极和所述相应电绝缘材料。(The invention is entitled "electroporation with Cooling". The invention discloses a medical system comprising a catheter, the catheter comprising: an insertion tube having a distal end; an elongate resilient distal section secured to the distal end of the insertion tube, the distal section having an outer surface; and a plurality of electrode structures, each electrode structure disposed on and protruding from the outer surface of the distal section, each electrode structure comprising a respective primary electrode and at least one respective secondary electrode extending around the outer surface, and a respective electrically insulating material disposed around the outer surface and between the respective primary electrode and the at least one respective secondary electrode, the respective primary electrode protruding from the outer surface to a greater extent than the at least one respective secondary electrode and the respective electrically insulating material.)

1. A medical system comprising a catheter, the catheter comprising:

an insertion tube having a distal end;

an elongate resilient distal section secured to the distal end of the insertion tube, the distal section having an outer surface; and

a plurality of electrode structures, each electrode structure disposed on and protruding from the outer surface of the distal section, each electrode structure including a respective primary electrode and at least one respective secondary electrode extending around the outer surface, and a respective electrically insulating material disposed around the outer surface and between the respective primary electrode and the at least one respective secondary electrode, the respective primary electrode protruding from the outer surface to a greater extent than the at least one respective secondary electrode and the respective electrically insulating material.

2. The system of claim 1, wherein the insertion tube is configured for insertion through a blood vessel into a heart of a subject, and wherein upon deployment of the resilient distal section within the heart, the resilient distal section defines a loop and is configured to open and close the loop.

3. The system of claim 2, wherein the collar is between 5mm and 35mm in diameter.

4. The system of claim 1, wherein the respective primary electrode comprises a metal ring and the at least one respective secondary electrode comprises at least one metal ring, the respective primary electrode and the at least one respective secondary electrode being connected by the respective electrically insulating material.

5. The system of claim 1, wherein the at least one respective secondary electrode comprises two respective electrodes.

6. The system of claim 5, wherein the two respective electrodes are disposed on either side of the respective primary electrode.

7. The system of claim 5, wherein the distal section has an elongation direction, the respective primary electrode has a first width measured parallel to the elongation direction, each of the two respective electrodes has a second width measured parallel to the elongation direction, the first width being greater than the second width.

8. The system of claim 7, wherein the first width is at least twice the size of the second width.

9. The system of claim 7, wherein the first width is in a range of 2mm to 8mm and the second width is in a range of 0.1mm to 1 mm.

10. The system of claim 1, wherein the distal section has an elongation direction, each electrode structure having a width, measured parallel to the elongation direction, of between 2.5mm and 10 mm.

11. The system of claim 1, wherein each electrode structure includes a respective thermally conductive material disposed below the respective primary electrode between the respective primary electrode and the outer surface of the distal section.

12. The system of claim 11, wherein the respective thermally conductive material is formed of a different material than the respective primary electrode.

13. The system of claim 11, wherein the respective thermally conductive material and the respective primary electrode are formed as a unitary piece having a mass greater than twice a mass of the at least one respective secondary electrode.

14. The system of claim 1, further comprising a signal generator configured to generate a pulse signal to be applied to cardiac tissue by the respective primary electrode to perform electroporation of the cardiac tissue.

15. The system according to claim 14, further comprising an Intracardiac Electrogram (IEGM) module configured to receive at least one signal sensed by the at least one respective secondary electrode and generate an IEGM for output to a display device.

16. A medical system comprising a catheter, the catheter comprising:

an insertion tube having a distal end;

an elongate resilient distal section secured to the distal end of the insertion tube, the distal section having an outer surface;

a plurality of electrode structures disposed on and protruding from the outer surface of the distal section; and

a thermally conductive material disposed below the electrode structures between each of the electrode structures and the outer surface of the distal section, wherein the thermally conductive material is formed of a different material than the electrode structures.

17. The system of claim 16, wherein the insertion tube is configured for insertion through a blood vessel into a heart of a subject, and wherein upon deployment of the resilient distal section within the heart, the resilient distal section defines a loop and is configured to open and close the loop.

18. The system of claim 17, wherein the collar is between 5mm and 35mm in diameter.

19. The system of claim 16, further comprising a signal generator configured to generate a pulse signal to be applied by the electrode structure to cardiac tissue to perform electroporation of the cardiac tissue.

20. A medical method, comprising:

providing a catheter, the catheter comprising:

an insertion tube having a distal end;

a resilient distal section secured to the distal end of the insertion tube, the distal section having an outer surface and an inner flush lumen; and

a plurality of electrode structures projecting from the outer surface, the electrode structures having a plurality of perforations formed therethrough, the electrode structures defining respective hollow sections between respective ones of the electrode structures and the outer surface, the perforations being in fluid communication with the irrigation lumen via the hollow sections; and

transforming the catheter for electroporation by injecting a thermally conductive material into the hollow section via the perforations of the electrodes.

Technical Field

The present invention relates to medical systems and in particular, but not exclusively, to catheter apparatus.

Background

A number of medical procedures involve placing a probe, such as a catheter, within a patient. Position sensing systems have been developed to track such probes. Magnetic position sensing is one method known in the art. In magnetic position sensing, a magnetic field generator is typically placed at a known location outside the patient's body. A magnetic field sensor within the distal end of the probe generates electrical signals in response to these magnetic fields that are processed to determine the coordinate position of the distal end of the probe. Such methods and systems are described in U.S. Pat. nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, in PCT international patent publication WO 1996/005768, and in U.S. patent application publications 2002/006455, 2003/0120150, and 2004/0068178. Position may also be tracked using impedance or current based systems.

Treatment of cardiac arrhythmias is a medical procedure in which these types of probes or catheters have proven extremely useful. Cardiac arrhythmias and in particular atrial fibrillation have been a common and dangerous medical condition, especially in the elderly.

Diagnosis and treatment of cardiac arrhythmias includes mapping electrical properties of cardiac tissue, particularly the endocardium, and selectively ablating cardiac tissue by applying energy. Such ablation may stop or alter the propagation of unwanted electrical signals from one portion of the heart to another. The ablation method breaks the unwanted electrical path by forming a non-conductive ablation lesion. Various forms of energy delivery for forming lesions have been disclosed and include the use of microwaves, lasers and more commonly radio frequency energy to form conduction blocks along the walls of cardiac tissue. In two-step surgery (mapping followed by ablation), electrical activity at various points within the heart is typically sensed and measured by advancing a catheter including one or more electrical sensors into the heart and acquiring data at the points. These data are then used to select an endocardial target area to be ablated.

Electrode catheters have been commonly used in medical practice for many years. They are used to stimulate and map electrical activity in the heart, and to ablate sites of abnormal electrical activity. In use, an electrode catheter is inserted into a major vein or artery, such as the femoral vein, and then introduced into the heart chamber of interest. A typical ablation procedure involves inserting a catheter having one or more electrodes at its distal end into a heart chamber. A reference electrode may be provided, typically taped to the patient's skin, or may be provided using a second catheter placed in or near the heart. RF (radio frequency) current is applied through the tip electrode of the ablation catheter and the current flows through the medium surrounding the tip electrode, i.e., blood and tissue between the tip electrode and the indifferent electrode. The distribution of the current depends on the amount of contact of the electrode surface with the tissue compared to blood, which has a higher conductivity than the tissue. Heating of the tissue occurs due to the electrical resistance of the tissue. The tissue is heated sufficiently to cause cell destruction in the heart tissue, resulting in the formation of non-conductive foci within the heart tissue.

U.S. patent publication 2010/0168548 to Govari et al describes a cardiac catheter including a lasso catheter for use in an electrical mapping system of the heart. The catheter has an array of raised, perforated electrodes in fluid communication with the irrigation lumen. There are position sensors on the distal collar portion and the proximal base portion of the catheter. The electrode is a sensing electrode that may be adapted for pacing or ablation. The raised electrodes safely contact the heart tissue, thereby forming an electrical connection with little resistance.

U.S. patent publication 2012/0310065 to Falwell et al describes a device and method for mapping electrical activity within the heart, creating lesions (ablations) in the heart tissue, creating areas of necrotic tissue that can prevent the propagation of errant electrical impulses caused by arrhythmias.

U.S. patent publication 2016/0324575 to Panescu et al describes a medical device (e.g., an ablation device) including an elongate body having a proximal end and a distal end; an energy delivery member positioned at the distal end of the elongate body; a first plurality of temperature measurement devices carried by or positioned within the energy delivery member, the first plurality of temperature measurement devices being thermally insulated from the energy delivery member; and a second plurality of temperature measurement devices positioned adjacent the proximal end of the energy delivery member, the second plurality of temperature measurement devices being thermally insulated from the energy delivery member.

U.S. patent 6,416,505 to Fleischman et al describes a surgical method and apparatus for positioning a diagnostic or therapeutic element within the body. The device may be catheter-based or a probe comprising a relatively short shaft.

U.S. patent 6,482,202 to Goble et al describes an electrosurgical instrument for treating tissue in the presence of an electrically conductive fluid medium and which includes an instrument shaft and an electrode assembly at one end of the shaft. The electrode assembly includes a tissue treatment electrode and a return electrode electrically insulated from the tissue treatment electrode by an insulating member. The tissue treatment electrode has an exposed end for treating tissue, and the return electrode has a fluid contact surface which is spaced from the tissue treatment electrode in use in a manner defining an electrically conductive fluid path which completes an electrical circuit between the tissue treatment electrode and the return electrode. The electrode assembly provides a plurality of apertures in the region of the tissue treatment electrode through which vapour bubbles and/or particulate matter can be aspirated from the region surrounding the tissue treatment electrode.

Disclosure of Invention

There is provided, in accordance with an embodiment of the present invention, a medical system including a catheter including: an insertion tube having a distal end; an elongate resilient distal section secured to the distal end of the insertion tube, the distal section having an outer surface; and a plurality of electrode structures, each electrode structure disposed on and protruding from the outer surface of the distal section, each electrode structure comprising a respective primary electrode and at least one respective secondary electrode extending around the outer surface, and a respective electrically insulating material disposed around the outer surface and between the respective primary electrode and the at least one respective secondary electrode, the respective primary electrode protruding from the outer surface to a greater extent than the at least one respective secondary electrode and the respective electrically insulating material.

Further, according to an embodiment of the invention, the insertion tube is configured for insertion into a heart of a subject through a blood vessel, and wherein the resilient distal section defines a loop and is configured to open and close the loop upon deployment of the resilient distal section within the heart.

Further, according to an embodiment of the invention, the collar has a diameter between 5mm and 35 mm.

Further, according to an embodiment of the invention, the respective primary electrode comprises a metal ring and the at least one respective secondary electrode comprises at least one metal ring, the respective primary electrode and the at least one respective secondary electrode being connected by a respective electrically insulating material.

Furthermore, according to an embodiment of the invention, the at least one respective secondary electrode comprises two respective electrodes.

Further, according to an embodiment of the invention, the two respective electrodes are arranged on either side of the respective primary electrode.

Further in accordance with an embodiment of the present invention, the distal section has an elongation direction, the respective primary electrode has a first width measured parallel to the elongation direction, each of the two respective electrodes has a second width measured parallel to the elongation direction, the first width being larger than the second width.

Further, according to an embodiment of the invention, the first width is at least twice the dimension of the second width.

Further, according to an embodiment of the present invention, the first width is in a range of 2mm to 8mm, and the second width is in a range of 0.1mm to 1 mm.

Further, according to an embodiment of the invention, the distal section has an elongation direction, each electrode structure having a width, measured parallel to the elongation direction, of between 2.5mm and 10 mm.

Further in accordance with an embodiment of the present invention, each electrode structure comprises a respective thermally conductive material disposed below a respective primary electrode between the respective primary electrode and an outer surface of the distal section.

Further, according to an embodiment of the present invention, the respective thermally conductive materials are formed of different materials from the respective primary electrodes.

Furthermore, according to an embodiment of the invention, the respective thermally conductive material and the respective primary electrode are formed as one piece having a mass greater than twice the mass of the at least one respective secondary electrode.

Further, according to an embodiment of the invention, the system comprises a signal generator configured to generate a pulse signal to be applied by the respective primary electrode to the cardiac tissue to perform electroporation of the cardiac tissue.

Additionally, in accordance with an embodiment of the present invention, the system includes an Intracardiac Electrogram (IEGM) module configured to receive at least one signal sensed by at least one respective secondary electrode and generate an IEGM for output to a display device.

There is also provided, in accordance with another embodiment of the present invention, a medical system including a catheter including: an insertion tube having a distal end; a resilient elongate distal section secured to the distal end of the insertion tube, the distal section having an outer surface; a plurality of electrode structures disposed on and protruding from the outer surface of the distal section; and a thermally conductive material disposed below the electrode structures between each of the electrode structures and the outer surface of the distal section, wherein the thermally conductive material is formed of a different material than the electrode structures.

Further, according to an embodiment of the invention, the insertion tube is configured for insertion into a heart of a subject through a blood vessel, and wherein the resilient distal section defines a loop and is configured to open and close the loop upon deployment of the resilient distal section within the heart.

Furthermore, according to an embodiment of the invention, the diameter of the collar is between 5mm and 35 mm.

Further, according to an embodiment of the invention, the system comprises a signal generator configured to generate a pulse signal to be applied by the electrode structure to the cardiac tissue for performing electroporation of the cardiac tissue.

There is also provided, in accordance with another embodiment of the present invention, a medical method including providing a catheter and converting the catheter for electroporation, the catheter including: an insertion tube having a distal end; a resilient distal section secured to the distal end of the insertion tube, the distal section having an outer surface and an inner flush lumen; and a plurality of electrode structures projecting from the outer surface, the electrode structures having a plurality of perforations formed therethrough, the electrode structures defining respective hollow sections between respective ones of the electrode structures and the outer surface, the perforations being in fluid communication with the flush lumen via the hollow sections, and the catheter being converted for electroporation by injecting a thermally conductive material into the hollow sections via the perforations of the electrodes.

Drawings

The present invention will be understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a medical system constructed and operative in accordance with an exemplary embodiment of the present invention;

FIG. 2 is a schematic illustration of a lasso catheter in a closed configuration, constructed and operative in accordance with an exemplary embodiment of the invention;

FIG. 3 is a schematic view of the lasso catheter of FIG. 2 in an open configuration;

4A-4D are cross-sectional views of alternative electrode configurations of the lasso catheter taken along line A: A of FIG. 3;

FIG. 5 is a schematic view of an alternative lasso catheter constructed and operative in accordance with an exemplary embodiment of the present invention; and is

Fig. 6 is a cross-sectional view of the electrode structure of the lasso catheter taken along line B: B of fig. 5.

Detailed Description

SUMMARY

Some catheters provide irrigation via a hole in the catheter electrode, e.g., nMRSA of Biosense Webster (Irvine, California)^TMA conduit. The nMRQ catheter is a lasso-shaped Radio Frequency (RF) ablation catheter that includes electrodes disposed along the lasso tube with open irrigation from within the lasso tube in the region of the electrodes (e.g., below the electrodes). Providing irrigation not only reduces heat but also dilutes blood to prevent its coagulation during RF ablation. Each electrode of the nMARQ protrudes from the surface of the lasso tube to ensure that the electrode protrudes above the polyurethane used to secure the electrode to the tube at the electrode edge to achieve proper contact between the electrode and the heart tissue. The electrode also has a uniform wall thickness so that when the electrode center bulges outward, there is a corresponding hollow section between the tube of the lasso and the inner surface of the electrode. The hollow section allows flushing fluid to be pumped into the hollow section to cool the electrode and exit through holes in the electrode.

If the same electrode is used without flushing (e.g., for electroporation), any heat generated in the air gap of the hollow section between the inner surface of the electrode and the tube (e.g., by electroporation) will not be readily dissipated because air is a very poor conductor of heat and the thin walls of the electrode do not provide a significant amount of heat capacity. Thus, even if electroporation does not generate too much heat, there may be an undesirable local temperature increase.

Exemplary embodiments of the present invention address the above-mentioned problems by providing a catheter having a resilient distal section (e.g., a shapeable loop) with an electrode structure disposed therealong. The electrode structure projects from a surface of the outer surface of the distal section and includes additional thermally conductive material to enhance cooling and increase thermal capacity during procedures such as electroporation. The thermally conductive material may be a fill material placed under an electrode of the electrode structure, the fill material being a different material than the rest of the electrode structure. For example, the filler may be a metal (such as platinum) or a non-metal (such as a thermally conductive epoxy). In other exemplary embodiments, the central protruding portion of the electrode structure may be configured to have a thickness greater than the thickness of the sides of the electrode structure, such that the thicker central section of the electrode structure provides a thermally conductive material (i.e., the electrode itself) to enhance cooling during procedures such as electroporation.

As used in the specification and claims, the term "thermally conductive material" is defined as a material having a thermal conductivity greater than or equal to 1 watt/meter-kelvin (W/mK) at 25 degrees celsius.

Another problem associated with electroporation is the need to provide electrodes large enough for applying the current of the electroporation pulse. The same large electrodes that facilitate electroporation may not be ideal for sensing, for example, for sensing cardiac electrical activity (e.g., Intracardiac Electrograms (IEGM) or for sensing position signals using current or impedance-based position tracking systems) because large electrodes may introduce excessive noise in the sensed signals or provide inaccurate spatial information due to their size. Providing a plurality of large electrodes for electroporation and smaller electrodes for sensing along the distal section of the catheter may make the distal section too inflexible.

Exemplary embodiments of the present invention address the above-mentioned problems by providing respective ones of electrode structures having a primary electrode that may be used for electroporation and one or more secondary electrodes and smaller electrodes that may be used for sensing. Providing electrodes for electroporation and sensing on the same electrode structure allows the electroporation and sensing functions to be combined on the catheter, but limits the number of structures on the distal section, allowing the distal section to remain sufficiently flexible. In some exemplary embodiments, each electrode structure may include two secondary electrodes, which may be placed on either side of the primary electrode, and may be used to sense location signals, IEGM, etc. The primary and secondary electrodes may be electrically isolated from each other using a suitable electrically insulating material (e.g., epoxy or any suitable polymer). In some exemplary embodiments, a thermally conductive material may be placed under the primary electrode to provide heat dissipation and heat capacity. In other exemplary embodiments, the primary electrode may be formed to have a thickness greater than that of the secondary electrode, such that the thicker electrode provides at least some heat dissipation. The primary and secondary electrodes may be formed as rings that extend around the distal section of the catheter and are connected together using an electrically insulating material. In other exemplary embodiments, the loop of thermally conductive material may form a loop around the distal segment, with the primary electrode placed over the thermally conductive loop and the secondary electrodes placed on either side of the thermally conductive loop. Many other configurations are possible, and some are described below with reference to the disclosed exemplary embodiments.

As used in the specification and claims, the term "electrically insulating material" is defined as a material having a volume resistivity of over one million volume resistivity (Ω cm) at 20 degrees celsius.

An exemplary embodiment of the present invention provides a medical system including a catheter. The catheter includes an insertion tube and an elongate resilient distal section secured to a distal end of the insertion tube. The insertion tube is inserted into the heart of the subject through a blood vessel. The resilient distal section defines a loop when deployed within the heart and is configured to open and close the loop, for example, using an internal resilient member (such as a length of metal, e.g., nitinol, that can be manipulated by a physician).

The catheter includes a plurality of electrode structures. Each electrode structure is disposed on and projects from an outer surface of a distal section. Each electrode structure may include a primary electrode and one or more secondary electrodes extending around an outer surface of the distal section, and an electrically insulating material disposed around the outer surface and between each primary electrode and the respective secondary electrode. The primary electrode of each electrode structure protrudes from the outer surface to a greater extent than the secondary electrode and the electrically insulating material of the electrode structure.

In some exemplary embodiments, the primary electrode comprises a metal ring and the secondary electrode comprises one (or more) metal rings. The primary electrode and the corresponding secondary electrode (i.e. of the same electrode structure) may be connected by an electrically insulating material.

In some exemplary embodiments, the secondary electrode comprises two electrodes optionally disposed on either side of a respective primary electrode (i.e., the same electrode structure).

The distal section has an elongation direction. Each primary electrode has a first width measured parallel to the elongated direction. Each secondary electrode has a second width measured parallel to the elongated direction. In some embodiments, the first width is greater than the second width.

Each electrode structure may include a respective thermally conductive material disposed below a respective primary electrode between the respective primary electrode and an outer surface of the distal section. In some exemplary embodiments, the thermally conductive material is formed of a different material than the primary electrode. In other exemplary embodiments, the thermally conductive material and the primary electrode are formed as a unitary piece. The unitary piece forming the primary electrode may have a mass greater than twice the mass of each secondary electrode.

The medical system may include a signal generator that generates a pulse signal to be applied by the one or more of the primary electrodes to cardiac tissue to perform electroporation of the cardiac tissue. The medical system may include an IEGM module configured to receive at least one signal sensed by the secondary electrode and generate an IEGM (or IEGMs) for output to a display device.

In some exemplary embodiments, each electrode structure includes a single electrode having a thermally conductive material disposed beneath the electrode structure between each electrode structure and the outer surface of the distal section. The thermally conductive material is formed of a material different from the electrode structure.

In some exemplary embodiments, the flushed catheter may be converted for electroporation as described below. The method includes providing a catheter including an insertion tube and a resilient distal section secured to a distal end of the insertion tube. The distal section has an outer surface and an inner irrigation lumen, and an electrode structure projecting from the outer surface. The electrode structures have perforations formed therethrough and define respective hollow sections between respective ones of the electrode structures and the outer surface. The bore is in fluid communication with the flush lumen via the hollow section. The method comprises switching the catheter for electroporation by injecting a thermally conductive material into the hollow section via the perforations of the electrode, and typically, but not necessarily, flushing the catheter is provided.

Description of the System

Reference is now made to fig. 1, which is a schematic illustration of a medical system 20, constructed and operative in accordance with an exemplary embodiment of the invention. Reference is also made to fig. 2, which is a schematic illustration of a lasso catheter 40 in a closed configuration, constructed and operative in accordance with an exemplary embodiment of the present invention.

The system 20 includes a catheter 40 configured to be inserted into a body part of a living subject (e.g., patient 28). Physician 30 navigates catheter 40 to a target location in heart 26 of patient 28 by manipulating a deflectable element of insertion tube 22 of catheter 40 and/or deflecting from sheath 23 using manipulator 32 near the proximal end of catheter 40 (inset 25). In this manner, or in any suitable manner, the insertion tube 22 is configured for insertion through a blood vessel into the heart of a subject. In the illustrated embodiment, the physician 30 uses the catheter 40 to perform electroanatomical mapping of the heart cavity and ablation of the heart tissue.

The catheter 40 includes an elongate resilient distal section 35 (e.g., an adjustable loop) that is inserted through the sheath 23 in a straight configuration and the elongate resilient distal section 35 resumes its intended functional shape only after the catheter 40 exits the sheath 23. By constraining the elongate resilient distal section 35 in a straight configuration, the sheath 23 also serves to minimize vessel trauma on its way to the target site.

The catheter 40 includes a plurality of electrode structures 48 (only some labeled for simplicity) including electrodes for sensing electrical activity and/or applying ablation power and/or electroporation power to ablate and/or electroporate tissue of the body part. The catheter 40 may incorporate a magnetic sensor 50 (shown in the cutaway portion of the insertion tube 22 on the left side of fig. 2) at the distal edge of the insertion tube 22 (i.e., at the proximal edge of the elongate resilient distal section 35). By way of example only, the magnetic sensor 50 may be a Single Axis Sensor (SAS) or a Dual Axis Sensor (DAS) or a Three Axis Sensor (TAS), based on, for example, dimensional design considerations. The catheter 40 may also include one or more electrodes 52 disposed on the distal edge of the insertion tube 22, such as on either side of the magnetic sensor 50. The electrodes 52, magnetic sensor 50, and the electrodes of the electrode structure 48 disposed on the elongate flexible distal section 35 are connected to various drive circuits in the console 24 by wires passing through the insertion tube 22.

In some exemplary embodiments, system 20 includes a magnetic sensing subsystem to estimate the location of elongate flexible distal section 35 of catheter 40 within the cardiac lumen of heart 26. The patient 28 is placed in a magnetic field generated by a pad containing one or more magnetic field generator coils 42 driven by a unit 43. The magnetic field generated by the coil 42 transmits an alternating magnetic field into the area where the body part is located. The transmitted alternating magnetic field generates a signal in the magnetic sensor 50 that is indicative of the position and/or orientation of the distal end of the catheter 40. The generated signals are transmitted to the console 24 and become respective electrical inputs to the processing circuitry 41.

In some exemplary embodiments, processing circuitry 41 uses position signals received from electrodes 52 and/or electrodes of electrode structure 48 and/or magnetic sensor 50 to estimate the position of catheter 40 within an organ, such as a heart chamber. In some embodiments, processing circuitry 41 correlates the position signals received from the electrodes with previously acquired magnetic position-calibration position signals to estimate the position of catheter 40 within the organ. The positional coordinates of the electrodes may be determined by the processing circuitry 41 based on (among other inputs) the ratio of the measured impedance or current distribution between the electrodes and the body surface electrodes 49.

Methods of position sensing using current distribution measurements and/or external magnetic fields are implemented in various medical applications, for example, in the manufacture by Biosense Webster Inc (Irvine, California)Implemented in systems and described in detail in U.S. patent nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, 6,332,089, 7,756,576, 7,869,865 and 7,848,787, PCT patent publication WO 96/05768, and U.S. patent application publications 2002/0065455 a1, 2003/0120150 a1, and 2004/0068178 a 1.

The 3-system applies a position tracking method based on Advanced Catheter Localization (ACL) impedance. In some exemplary embodiments, the processing circuitry 41 is configured to use an ACL method to generate a mapping (e.g., a current-position matrix (CPM)) between the indication of electrical impedance and the position of the magnetic field generator coil 42 in the magnetic coordinate system. The processing circuitry 41 estimates the position of the electrode by performing a look-up in CPM.

Other methods of determining the position of the distal end of the catheter 40 may be used, for example, based on an ultrasound transducer and receiver, using imaging techniques such as ultrasound or MRI or CT scanning (which may include placing radiopaque markers on the catheter 40).

The processing circuitry 41 (typically part of a general purpose computer) is further connected via suitable front end and interface circuitry 44 to receive signals from body surface electrodes 49. The processing circuitry 41 is connected to the body surface electrodes 49 by wires that extend through the cable 39 to the chest of the patient 28.

In some exemplary embodiments, the processing circuitry 41 presents the representation 31 of the at least a portion of the catheter 40 and the mapped body portion to the display device 27 in response to the calculated position coordinates of the catheter 40.

The processing circuitry 41 is typically programmed with software to perform the functions described herein. The software may be downloaded to the computer in electronic form over a network, for example, or it may alternatively or additionally be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory.

Medical system 20 may also include a signal generator 54 (such as an RF signal generator) configured to be connected to catheter 40 and apply electrical signals to the electrodes of electrode structure 48 to perform RF ablation and/or electroporation.

The exemplary illustrations shown in fig. 1 and 2 were chosen purely for the sake of conceptual clarity. For simplicity and clarity, FIG. 1 only shows the elements relevant to the disclosed technology. System 20 generally includes additional modules and elements that are not directly related to the disclosed technology and, therefore, are intentionally omitted from fig. 1 and the corresponding description. The elements of system 20 and the methods described herein may further be applied, for example, to control ablation/electroporation of tissue of heart 26.

The medical system 20 is described with reference to a catheter 40 having a lasso-shaped elongate resilient distal section 35. The catheter 40 may be implemented with an elongate resilient distal section 35 of any suitable shape, such as, but not limited to, a multi-splined catheter.

Reference is now made to fig. 3, which is a schematic illustration of the lasso catheter 40 of fig. 2 in an open configuration. Reference is also made to fig. 2.

The distal end 56 of the insertion tube 22 generally includes a deflectable section and a distal edge that includes the electrode 52 with the magnetic sensor 50 disposed therebetween. The distance between the centres of the two electrodes 52 may be any suitable distance, such as in the range 5mm to 20mm, for example 11 mm. The magnetic sensor 50 (e.g., a magnetic coil sensor) may be disposed at any suitable location. In the example of fig. 2, magnetic sensor 50 is shown closer to a distal one of electrodes 52. The insertion tube 22 may have any suitable outer diameter, for example in the range 1mm to 6mm, for example 2.5 mm.

The elongate resilient distal section 35 is secured to the distal end 56 of the insertion tube 22. The elongate resilient distal section 35 has an outer surface 58. The elongate elastic distal section 35 may be constructed of any suitable material, for example, a flexible polymer, such as polyurethane or polyether block amide. The resilient distal section 35 defines a loop when deployed within the heart and is configured to open and close (or tighten and loosen) the loop. As used in the present specification and claims, the term "loop" is defined as the elongated resilient distal section 35 bending at least 180 degrees around a bend and forming a closed bend, or a partially overlapping bend, or a partially open loop.

The loop shape may be formed by a resilient or deflectable element, such as a nitinol ridge (not shown), disposed within the lumen of the elongate resilient distal section 35, which allows the elongate resilient distal section 35 to be straight during insertion into the heart 26 (fig. 1) and to form a loop once the elongate resilient distal section 35 exits the sheath 23 (fig. 1). The collar may be contracted by pulling the resilient element, for example, using manipulator 32 (fig. 1). In some exemplary embodiments, the elongate resilient distal section 35 may be formed as an inflatable element.

The open loop (fig. 3) and closed loop (fig. 2) may have any suitable diameter. In some exemplary embodiments, the open loop has a diameter between 10mm and 35mm and the closed loop has a diameter between 5mm and 25 mm. In some exemplary embodiments, the distal section has an open diameter of 25.4mm and a closed diameter of 15.24 mm.

Each electrode structure 48 is disposed on and projects from an outer surface 58 of the elongate resilient distal section 35. The electrode structure 48 (only some labeled for simplicity) may be attached to the elongate resilient distal section 35 using a suitable adhesive and/or polyurethane for securing the edges of the electrode structure 48 to the elongate resilient distal section 35.

The catheter 40 may include any suitable number of electrode structures 48 depending on the width of each electrode structure 48, the length of the elongate resilient distal section 35, and the desired flexibility of the distal section 35. Too much electrode structure 48 may make the distal section 35 too inflexible. Fig. 2 and 3 show ten electrode structures 48 disposed on the distal section. In other exemplary embodiments, the number of electrode structures 48 disposed on the distal section 35 may include any suitable number, for example, in the range of 4 to 30.

The electrode structures 48 may be evenly or unevenly spaced along the distal segment 35. In some exemplary embodiments, the center-to-center spacing between electrode structures 48, as measured along the arc, is 7mm, but any suitable value may be employed, for example, in the range of 3mm to 30 mm. The distance from the center of the most-distal electrode structure 48 to the tip 60 of the distal section 35 may be any suitable value, for example in the range of 1mm to 20mm, for example 7 mm.

In some exemplary embodiments, as shown in inset 66 (which illustrates a cross-sectional view taken along line a: a of fig. 3), each electrode structure 48 includes one electrode 62 with a thermally conductive material 64 disposed between the electrode 62 and the outer surface 58. The thermally conductive material 64 may be any suitable thermally conductive material such as, but not limited to, platinum, palladium, gold, or a thermally conductive epoxy. In some exemplary embodiments, the thermally conductive material 64 is first wrapped around the outer surface 58 of the elongate resilient distal segment 35, and then the electrode 62 is wrapped around the thermally conductive material 64. In other exemplary embodiments, the electrode 62 is first secured around the outer surface 58 (either as a single piece or from two halves that are subsequently joined together) and then a thermally conductive material 64 is injected through holes (not shown) in the electrode 62 beneath the electrode 62.

Reference is now made to fig. 4A-4D, which are cross-sectional views of an alternative electrode configuration 48 of the lasso catheter 40 taken along line a: a of fig. 3. Common features of the various electrode structures 48 shown in fig. 4A-4D are first described below.

Each electrode structure 48 includes a respective primary electrode 68 and at least one respective secondary electrode 70 extending around outer surface 58. Each electrode structure 48 also includes a respective electrically insulating material 72 disposed about outer surface 58 and between a respective primary electrode 68 and a respective secondary electrode 70. The term "corresponding" with reference to primary electrode 68, secondary electrode 70, and electrically insulating material 72 is used to describe primary electrode 68, secondary electrode 70, and electrically insulating material 72 of the same electrode structure 48. The respective primary electrodes 68 protrude from the outer surface 58 to a greater extent than the respective secondary electrodes 70 and the respective electrically insulating material 72.

In some exemplary embodiments, each electrode structure 48 includes two secondary electrodes 70 optionally disposed on either side of a respective primary electrode 68.

As previously mentioned, a problem associated with electroporation is the need to provide electrodes large enough for the current to apply the electroporation signal. The same large electrodes that facilitate electroporation may not be ideal for sensing, for example, for sensing cardiac electrical activity (e.g., Intracardiac Electrograms (IEGM) or for sensing location signals using current or impedance based location tracking systems) because large electrodes may introduce excessive noise in the sensed signals. Providing a plurality of large electrodes for electroporation and smaller electrodes for sensing along the distal section of the catheter may make the distal section too inflexible. Thus, in some exemplary embodiments, each second electrode 70 is generally narrower than the first electrode 68, allowing the primary electrodes 68 to be used for electroporation and the secondary electrodes 70 to be used for sensing. Because primary electrode 68 and secondary electrode 70 are included in a single structure of electrode structure 48, a large electrode for electroporation and a smaller electrode for sensing may be provided along distal section 35 of catheter 40 without making catheter 40 too inflexible.

In some exemplary embodiments, the signal generator 54 (fig. 1) is configured to generate a pulsed signal to be applied by one or more of the primary electrodes 68 to the cardiac tissue to perform electroporation of the cardiac tissue. In some embodiments, the medical system 20 includes an Intracardiac Electrogram (IEGM) module 74 (fig. 1) configured to receive at least one signal sensed by one or more of the secondary electrodes 70 and generate one or more IEGMs for output to the display device 27 (fig. 1).

In some exemplary embodiments, each primary electrode 68 and each secondary electrode 70 is formed from a metal strip that is wrapped around the outer surface 58 of the elongate resilient distal section 35, forming a corresponding metal loop. In other embodiments, each primary electrode 68 and each secondary electrode 70 may be formed of half-rings joined together around the outer surface 58. The primary electrode 68 and the secondary electrode 70 of one of the electrode structures 48 may be connected together by an electrically insulating material 72. The electrically insulating material 72 may also serve as an adhesive to glue the primary electrode 68 to the secondary electrode 70. In other exemplary embodiments, a suitable adhesive may be used to connect primary electrode 68, secondary electrode 70, and electrically insulating material 72.

In some exemplary embodiments, a material holder (or material holders) may be used to hold primary electrode 68 to secondary electrode 70. An electrically insulating material 72 (e.g., epoxy) may then be added between the primary electrode 68 and the secondary electrode 70, thereby further adhering the primary electrode 68 to the secondary electrode 70. After the electrically insulating material 72 is provided, the holder can be removed.

In some exemplary embodiments (see fig. 4B), the electrically insulating material 72 may comprise a strip of material wrapped around the outer surface 58 of the elongate resilient distal segment 35.

In some exemplary embodiments, each electrode structure 48 includes a respective thermally conductive material 76 disposed below the respective primary electrode 68 between the respective primary electrode 68 and the outer surface 58 of the distal segment 35. In some exemplary embodiments, thermally conductive material 76 forms a portion of primary electrode 68 (as shown in fig. 4C and 4D). In other exemplary embodiments, the thermally conductive material 76 is placed as a separate element below the primary electrode 68 (e.g., a ring disposed around the outer surface 58), as shown in fig. 4A and 4B. In some exemplary embodiments, a thermally conductive material 76 is also used as the electrically insulating material 72, as shown in fig. 4B.

Reference is now made to fig. 4A. Exemplary dimensions of the electrode structure 48 are now described with reference to fig. 4A. The dimensions described below may also be applied to other exemplary embodiments, such as the exemplary embodiments described with reference to fig. 4B-4D. Although exemplary dimensions are described below, the dimensions of electrode structure 48 may include any suitable values.

The elongate elastic distal section 35 has an elongation direction 78. The primary electrode 68 has a width 80 measured parallel to the elongation direction 78. Each secondary electrode 70 has a width 82 measured parallel to the direction of elongation 78. Width 80 is greater than width 82. In some exemplary embodiments, width 80 is at least twice the dimension of width 82. In some exemplary embodiments, width 80 is in the range of 2mm to 8mm, and width 82 is in the range of 0.1mm to 1 mm. Each electrode structure 48 has a total width 84, measured parallel to the elongation direction 79, of between 2.5mm and 10 mm.

Fig. 4A shows that thermally conductive material 76 is formed of a different material than primary electrode 68. The thermally conductive material 76 may be formed as a rectangular strip wrapped around the elongate resilient distal segment 35 with the primary electrode 68 wrapped on top of the thermally conductive material 76. In some exemplary embodiments, the thermally conductive material 76 and/or the primary electrode 68 may be formed as two half rings connected around the elongate resilient distal segment 35. The secondary electrode 70 is connected to the primary electrode 68 via an electrically insulating material 72, which may also act as a binder to connect the primary electrode 68 with the secondary electrode 70. The wall thickness of primary electrode 68 and secondary electrode 70 may have any suitable value, for example, in the range of 0.01mm to 0.25 mm. The thickness of the thermally conductive material 76 may have any suitable value, for example, in the range of 0.01mm to 0.25 mm.

Reference is now made to fig. 4B. Fig. 4B shows electrically insulating material 72 and thermally conductive material 76 as the same element. Electrically insulating material 72 and thermally conductive material 76 may be comprised of an epoxy, such as boron nitride or diamond doped epoxy, and have a thickness in the range of 0.01mm to 0.25 mm. The primary electrode 68 is partially disposed on an electrically insulating material 72 and a thermally conductive material 76. Secondary electrodes 70 are placed on either side of electrically insulating material 72 and thermally conductive material 76. The dimensions of the primary electrode 68 and the secondary electrode 70 are substantially the same as those mentioned with reference to fig. 4A.

Reference is now made to fig. 4C and 4D. Fig. 4C and 4D show that the thermally conductive material 76 and the primary electrode 68 are formed as a unitary piece, whereby the thicker primary electrode 68 dissipates heat formed during electroporation. In some exemplary embodiments, the mass of the unitary piece may be greater than twice the mass of one of the secondary electrodes 70 of the electrode structure 48. The wall thickness of the primary electrode 68 can have any suitable value, for example, in the range of 0.025mm to 0.5 mm. The wall thickness of secondary electrode 70 can have any suitable value, for example, in the range of 0.025mm to 0.5 mm. In some exemplary embodiments, the wall thickness of primary electrode 68 is at least twice the wall thickness of secondary electrode 70.

The primary electrode 68 and the secondary electrode 70 shown in fig. 4C may each be formed as flat electrodes wrapped around the outer surface 58 to form a ring or as two half rings connected together around the elongate resilient distal section 35. Primary electrode 68 shown in fig. 4D has a non-uniform surface and bulges away from outer surface 58 the further toward the center of primary electrode 68.

Reference is now made to fig. 5, which is a schematic illustration of an alternative lasso catheter 86, constructed and operative in accordance with an exemplary embodiment of the present invention. Reference is now made to fig. 6, which is a cross-sectional view of one of the electrode structures 48 of the lasso catheter 86, taken along line B: B of fig. 5. The lasso catheter 86 is substantially identical to the catheter 40 of fig. 1-4, except for the following differences. The elongate resilient distal section 35 includes an inner flush lumen 94 (fig. 6). Each electrode structure 48 (only some labeled for simplicity) includes at least one flushing hole (perforation) 92 (only some labeled for simplicity) formed therethrough. The electrode structures 48 define respective hollow sections 96 between respective ones of the electrode structures 48 and the outer surface 58. The perforations 92 are in fluid communication with the irrigation lumen 94 via a hollow segment 96.

The lasso catheter 86 may be converted from an irrigation catheter to a non-irrigation catheter for performing electroporation, as described below. A thermally conductive material 90 is injected into a hollow section 96 located between each electrode structure 48 and the outer surface 58 of the distal section 35, below each of the electrode structures 48 of the lasso catheter 86. The placement of the thermally conductive material 90 generally prevents the lasso catheter 86 from providing irrigation via the electrode structure 48. Thermally conductive material 90 may be injected under electrode structure 48 via perforations 92. Thermally conductive material 90 is typically formed of a different material (e.g., epoxy or platinum) than electrode structure 48, but may also be formed of the same material as electrode structure 48.

As used herein, the term "about" or "approximately" for any numerical value or range indicates a suitable dimensional tolerance that allows the component or collection of elements to achieve its intended purpose as described herein. More specifically, "about" or "approximately" may refer to a range of values ± 20% of the recited value, e.g., "about 90%" may refer to a range of values from 72% to 108%.

Various features of the invention which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination.

The embodiments described above are cited by way of example, and the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.