Patent Application
20200345413
The present description relates generally to electrophysiology catheters, and in particular, irrigated ablation catheters.
Electrical activity at a point in the heart is typically measured by advancing a multiple-electrode catheter to measure electrical activity at multiple points in the heart chamber simultaneously. A record derived from time varying electrical potentials as measured by one or more electrodes is known as an electrogram. Electrograms may be measured by unipolar or bipolar leads, and are used, e.g., to determine onset of electrical propagation at a point, known as local activation time. Various electrode designs are known for different purposes. In particular, catheters having basket-shaped electrode arrays are known and described, for example, in U.S. Pat. No. 5,772,590, the disclosure of which is incorporated herein by reference.
An electrogram is bi-phasic as well as being a global signal. Thus, sensors in a cardiac chamber may detect far-field electrical activity, i.e., the ambient electrical activity originating away from the sensors, which can distort or obscure local electrical activity, i.e., signals originating at or near the sensor location. Thus, in some instances, it is desirable to obtain a local signal in the form of a monophasic action potential signal. Monophasic action potentials (MAPs) are extracellularly recorded wave forms that can reproduce the repolarization time course of transmembrane action potentials (TAPs) with high fidelity. Applicants recognized that there is a need to provide a catheter that can obtain a local signal in the form of a MAP signal.
MAP has been used in electrophysiology to allow for a better understanding at a cellular level of the tissue response. The MAP can reproduce the repolarization time course of transmembrane action potentials (TAPs) with high fidelity with the use of an active electrode and an inactive electrode. Embodiments of the present invention include a catheter with microelectrodes and thermocouples so that the microelectrodes can be utilized to cause a localized therapeutic trauma on the tissue to study MAP on the local tissue.
Embodiments of the present invention obtain MAP signals by using an aspiration catheter with a sensing catheter to create a localized trauma in tissue which causes a response in measurable signals from the tissue. The MAP signal is used to show effects of drugs, diseased or healthy tissues, among other diagnosticable indicators. Embodiments of the present invention also obtain MAP signals by using a catheter to apply pressure on the tissues to obtain reversible localized injury on the tissue. Either of these techniques allows a health care provider to infer the cellular level response (i.e., signals) due to a local trauma so that a therapeutic response can be devised.
Embodiments of the present invention include a catheter with multi-microelectrodes with thermocouples to obtain MAP signals by using contact force-applying microelectrodes to provide an optimum force on the tissue (for a reversible localized injury) while measuring the response signals from the tissue with the force-applying microelectrodes. The MAP signals can be measured as well as with the non-force-applying microelectrodes.
The microelectrodes allow for consistent force application due to a contact force sensor via the smaller surface area in which the microelectrodes are applied against, along with a roughened or fractured surface that allow for extraction of high signal to noise electrical signals from the localized tissue injury.
In some embodiments, a catheter comprises:
an elongated catheter shaft;
a distal section, including;
In some embodiments, the distal sensing portion has a spherical configuration.
In some embodiments, the distal sensing portion protrudes a predetermined distance from a distal end of the ablation electrode.
In some embodiments, the distal sensing portion has a fractured surface.
In some embodiments, the distal sensing portion has a coating from the group consisting of silver chloride, iridium oxide and titanium oxide.
In some embodiments, the distal sensing portion has an etched surface.
In some embodiments, the distal sensing portion has a width ranging between about 0.014 mm and 0.015 mm.
In some embodiments, the distal sensing portion is configured to cause reversible localized injury to tissue.
In some embodiments, the distal section includes a plurality of microelectrodes, each microelectrode has a respective distal sensing portion and a respective proximal portion, the respective proximal portion extending through a respective bore formed in the side wall of the ablation electrode.
In some embodiments, the side wall of the ablation electrode includes at least one blind passage and at least one thermocouple wire pair in the blind passage.
In some embodiments, the thermocouple wire pair has a nonlinear configuration so as to provide at least one contact surface with an interior surface of the blind passage.
In some embodiments, a method of using a catheter with multiple microelectrodes, comprises:
In some embodiments, the method further comprises:
These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:
The following detailed description should be read with reference to the drawings, in which like elements in different drawings are identically numbered. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.
As used herein, the terms “about” or “approximately” for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein. More specifically, “about” or “approximately” may refer to the range of values ±20% of the recited value, e.g. “about 90%” may refer to the range of values from 71% to 99%. In addition, as used herein, the terms “patient,” “host,” “user,” and “subject” refer to any human or animal subject and are not intended to limit the systems or methods to human use, although use of the subject invention in a human patient represents a preferred embodiment.
With reference to
As shown in
The operations, functions and acts of system 100 are managed by a system controller 130, comprising a processing unit 132 communicating with a memory 134, wherein is stored software for operation of system 100. In some embodiments, the controller 130 is an industry-standard personal computer comprising a general-purpose computer processing unit. However, in some embodiments, at least some of the operations, functions or acts of the controller are performed using custom-designed hardware and software, such as an application specific integrated circuit (ASIC) or a field programmable gate array (FPGA). In some embodiments, the controller 130 is managed by the operator 19 using a pointing device 136 and a graphic user interface (GUI) 138, which enable the operator to set parameters of system 100. The GUI 138 typically also displays results of the procedure to the operator on a display monitor 140.
The software in memory 134 may be downloaded to the controller in electronic form, over a network, for example. Alternatively or additionally, the software may be provided on non-transitory tangible media, such as optical, magnetic, or electronic storage media.
Electrical components, including electrodes, thermocouples and position (location or orientation) sensors, of the distal section 15 are connected to system controller 130 by conductors that pass through the catheter shaft 12 and the deflection section 14. In addition to being used for ablation, the electrodes may perform other functions, as is known in the art. The system controller 130 may differentiate between the currents for the different functions of the electrical components by frequency multiplexing. For example, radio-frequency (RF) ablation power may be provided at frequencies of the order of hundreds of kHz, while position sensing frequencies may be at frequencies of the order of 1 kHz. A method of evaluating the position of distal section 15 using impedances measured with respect to the electrodes is disclosed in U.S. Pat. No. 8,456,182 titled “Current Localization Tracker,” to Bar-Tal et al., the entire disclosure which is incorporated herein by reference.
As shown in
Typically, during ablation, heat is generated in the one or more electrodes energized by the ablation module 150, as well as in the surrounding region. In order to dissipate the heat and to improve the efficiency of the ablation process, the system controller 130 monitors temperature of different portions/surfaces of the distal section 15 and supplies irrigation fluid to distal section 15. The system controller 130 uses the irrigation module 152 to monitor and control irrigation parameters, such as the rate of flow and the temperature of the irrigation fluid. In some embodiments, the system controller 130 uses the irrigation module 152 in response to the temperature sensing module 156 in managing “hot spots” or uneven heating on the surface of the distal section 15, by controlling and adjusting movable internal components of the distal section 15, as described in detail further below.
The system controller 130 uses the tracking module 154 to monitor the location and orientation of the distal section 15 relative to the patient 11. The monitoring may be implemented by any tracking method known in the art, such as one provided in the Carto3® system manufactured by Biosense Webster of Irvine, Calif. Such a system uses radio-frequency (RF) magnetic transmitter external to patient 11 and responsive elements (e.g., a position sensor 50, see) within distal section 15. Alternatively or additionally, the tracking may be implemented by measuring impedances between
The system controller 130 uses the MAP module 157 to receive and process MAP signals sensed by the microelectrodes in reproducing repolarization time course of transmembrane action potentials (TAPs) with high fidelity with the use of an active electrode and an inactive electrode. As described in detail further below, the MAP signals pre- and post-ablation can provide an indication to an operator of the system as to where and when to move the catheter to create a continuous lesion or line of block.
With reference to
Extending within each bore 26 is a respective microelectrode 17 having an elongated stem 28 and a distal sensing portion 29 that is exposed and configured for contact with tissue. The microelectrode 17 may be constructed of any material, including, for example, platinum iridium. Notably, the stem 28 of each microelectrode 17 is configured to extend a predetermined distance distal of the distal end 24 of the cap electrode 21 so that the distal sensing portion 29 can contact and indent the tissue T with optimum force to cause a reversible localized trauma, but without causing permanent injury, for sensing MAP signals, as shown in
In some embodiments, the distal sensing portion 29 of the microelectrode 17 is configured, for example, having a spherical or bulbous configuration that can be generally fully enveloped by surrounding tissue so as to avoid sensing extracellular or far-field signals. The profile of the microelectrodes serves to cause reversible perforation for studying MAPs at the tissue site. With multiple microelectrodes, multiple separate local tissue area can be studied simultaneously. The configuration of the distal sensing portion may include oval or elliptical configurations. In some embodiments, the distal portion 29 has a width or diameter W of about 0.014 mm and 0.015 mm and the stem 28 has a length of about 0.100 mm. The protrusion distance D of distal sensing portion 29 measured from a distalmost surface of the distal sensing portion 29 to a distal face of the distal end 24 is about 0.023 mm. The protrusion distance enables the microelectrodes access to in depth MAPs of the localized cellular tissue.
In some embodiments, the surface of the distal sensing portion 29 are mechanically prepared so as to minimize signal noise via cleaning methodologies and surface coatings. In some embodiments, a surface of the distal sensing portion 29 is roughened, for example, by plasma etching, or coated with one or more coatings of fracturing substance, for example, silver chloride, iridium oxide or titanium nitride, to provide cracks and crevices on the order of microns to increase the surface area of the distal portion. Iridium oxide can provide up to 100 times greater surface area. Titanium nitride can provide up to 1000 times greater surface area. Mechanical roughening with plasma etching can provide up to 10 times greater surface area. Such fractured surface area allows for extraction of high signal to noise electrical signals from the localized tissue trauma.
Each stem 28 is surrounded by an elongated insulating support member 31 with a lumen 32, for example, a polyimide tube, that is generally coextensive with the stem in the respective bore 26. The member 31 electrically isolates the entirety of the microelectrode 17 from the electrode 21. The fit between the stem 28 and the lumen 32, and the fit between the support member 31 and the bore 26 may be a close or tight fit. A distal end of the insulating support member 31 is configured with a flange 34 to seal the bore 26 and the lumen 32. At a proximal end of stem 28, electrical connection is provided, for example, by welding, to a respective lead wire 35. The proximal opening of each bore 26 leads into the neck 22 of the cap electrode 21 so that the lead wires 35 can extend into the neck 22 and proximally along the deflection section 14 and the catheter shaft 12 toward the control handle 16.
The side wall 23 of the cap electrode 21 also has a plurality of blind passages 36 in equi-angular locations about the center longitudinal axis 27, offset from the locations of the bores 26, each housing a respective thermocouple (TC) wire pair 18 for example a constantan wire and a copper wire pair. In some embodiment, six blind passages 36 are located in the side wall to house six pairs of TC 18, for example, at 15, 75, 135, 195, 255 and 315 degrees about the axis 27. Twisted distal ends of a wire pair forming a distal junction of each TC 18 are housed in a respective tube 39, for example, a hypotube, that has a predetermined length greater than the length of the blind passages. The greater length of the hypotubes and the distal junctions, and a larger diameter of the blind passages 36 enable the hypotubes and the distal junctions to be crammed into a nonlinear shape inside the blind passages so that contact between the hypotubes and the inner wall of blind passages is ensured for more accurate temperature sensing of the cap electrode 21. Proximal opening of each blind passage opens into the neck 22 of the cap electrode 21 so that the wire pairs of the TC 18 can pass into the neck and proximally along the catheter deflection section 14, the catheter shaft 12 and into the control handle 16.
In some embodiments, the insert 20 is configured in part as an irrigation fluid flow diverter with one or more radial channels 37 that provide fluid communication between the chamber 25 and a distal end of an irrigation lumen 52 that extends along the length of the catheter between the distal section 15 and the control handle 16. The irrigation module 152 of the system controller 130 (
The insert 20 occupying the neck 22 of the cap electrode 21 may be formed with a blind hole to receive a distal end of lead wire 55 for energizing the insert 20 and the cap electrode 21. A transverse channel may also be formed through which a safety wire 38 passes to tether the cap electrode 21 to the catheter 10 as a safety measure. In some embodiments, the distal section 15 includes a force sensor 40 whose distal end is connected to the proximal end of the insert. Aspects of a similar force sensor are described in U.S. Pat. No. 8,357,152, to Govari et al., issued Jan. 22, 2013, and in U.S. Patent Application 2011/0130648, to Beeckler et al., filed Nov. 30, 2009, both of whose disclosures are incorporated herein by reference. The force sensor 40 comprises a resilient coupling member 41, which forms a spring joint between distal and proximal ends of the coupling member, with a central lumen 42 therethrough. The coupling member 41 typically has one or more helices 43 cut in the member 41, so that the member 41 behaves as a spring.
The coupling member 41 is mounted within and covered by a nonconducting, biocompatible sheath 44, which is typically formed from flexible plastic material. Having the outer diameter of the coupling member to be as large as possible, typically increases the sensitivity of force sensor 40. In addition, and as explained below, the relatively large diameter of the tubular coupling member 41, and its relatively thin walls, provide the relatively spacious central lumen 42 through which components pass into and out of the distal section 15. During RF ablation procedures, considerable heat may be generated in the distal section 15 and thus the sheath 44 may comprise a heat-resistant plastic material, such as polyurethane, whose shape and elasticity are not substantially affected by exposure to the heat.
In some embodiments, the force sensor 40 includes a distal coil 45 (
In some embodiments, the distal coil 45 is driven by a current, via a cable (not shown) from the system controller 130 and the force module 148, to generate a magnetic field. This field is received by the proximal coils 46 which are fixed at the same axial distance from the coil 45 but at different angular locations about the longitudinal axis 27, for example, 0, 120, and 240 degrees about the axis 27. Proximal coils 46 generate electrical signals in response to the magnetic field transmitted by the distal coil 45. These signals are conveyed by a cable (not shown) to the system controller 130, which uses the force module 148 to process the signals in order to measure the displacement of spring joint parallel and concentric with axis 27, as well as to measure the angular deflection of the joint from the axis. From the measured displacement and deflection, the system controller 130 is able to evaluate, typically using a previously determined calibration table stored in force module 148, a magnitude and a direction of the force on the spring joint of the coupling member 41. Notably, the force sensor 40 enables the plurality of microelectrodes 17 to apply a consistent force against the tissue, although it is understood that the catheter 10 in some embodiments need not have a force sensor.
The system controller 130 uses the tracking module 154 (
In use, the catheter 10 is introduced into the patient's vascular system and the distal section 15 is advanced to an area of interest, for example, a heart chamber. The system controller 130 accomplishes diagnostic procedures, including mapping. For example, the position sensor 50 generates signals processed by the tracking module 154 in determining location and orientation of the distal section 15. The tip electrode 21, a distal ring electrode 53 and/or a proximal ring electrode 54 sense electrical activity of heart tissue which signals generated are processed by processing unit 132. A 3-D electrophysiology map may be created from these processed signals, and ablation tissue sites are identified and targeted. The system controller 130 may then accomplish therapeutic procedures. For example, the operator maneuvers the distal section 15 so that the tip electrode 21 is in contact with the targeted tissue site. Contact between the tip electrode 21 and tissue results in the application of a force that displaces the distal section 15 relative to the proximal end of the coupling member 41 of the force sensor 40. Such displacement causes the proximal coils 46 to generate signals that are processed by the force module 148, for example, to confirm contact of the distal section 15 and tissue in preparation for ablation.
Before and/or during ablation, the irrigation module 152 controls delivery and rate of delivery of irrigation fluid to the distal section 15 by a pump (not shown) that delivers irrigation fluid from a fluid source (not shown) through the irrigation lumen 52. The ablation module 150 delivers RF energy to the cap electrode 21 which heats the target tissue to form a lesion. One or more of the thermocouples TCs 18 generate signals representative of temperature of respective surrounding tissue and fluids. Depending on the temperature(s) sensed, the system controller 130 may in some embodiments communicate with the ablation module 150 to adjust the power delivery and/or with the irrigation module 152 to adjust the rate of fluid delivery or the position of the flow director 58 to its distal-most position, a more distal position or a less proximal position, as appropriate to avoid hot-spots, charring or thrombosis. Irrigation fluid can therefore be directed to exit the irrigation apertures 33 at one or more selected flow rates.
By pressing one or more microelectrodes 17 against tissue with sufficient force to bury the respective one or more distal sensing portions 29 into the tissue to cause reversible localized trauma or injury, the one or more microelectrodes 17 can detect MAP signals. Three pre-ablation ECG signals detected respectively by the microelectrodes 17, designated μ1-μ2, μ2-μ3, and μ3-μ1, as shown in
and
The method may also include:
The above method may be particularly useful when a continuous lesion or line of block is desired, such as for pulmonary vein isolation.
The preceding description has been presented with reference to certain exemplary embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes to the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention, and that the drawings are not necessarily to scale. Moreover, it is understood that any one feature of an embodiment may be used in lieu of or in addition to feature(s) of other embodiments. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings. Rather, it should be read as consistent with and as support for the following claims which are to have their fullest and fairest scope.
This application claims priority to and the benefit of U.S. Provisional Patent Application No. 62/842,439, filed May 2, 2019, the entire content of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62842439 | May 2019 | US |
