Patent Application
20240293177
The present disclosure relates generally to tissue ablation systems and methods. In particular, the present disclosure relates to electroporation systems and methods with automatic phrenic nerve monitoring.
It is generally known that ablation therapy may be used to treat various conditions afflicting the human anatomy. For example, ablation therapy may be used in the treatment of atrial arrhythmias. When tissue is ablated, or at least subjected to ablative energy generated by an ablation generator and delivered by an ablation catheter, lesions form in the tissue. Electrodes mounted on or in ablation catheters are used to cause tissue destruction in cardiac tissue to correct conditions such as atrial arrhythmia (including, but not limited to, ectopic atrial tachycardia, atrial fibrillation, and atrial flutter).
Arrhythmia (i.e., irregular heart rhythm) can create a variety of dangerous conditions including loss of synchronous atrioventricular contractions and stasis of blood flow which can lead to a variety of ailments and even death. It is believed that the primary cause of atrial arrhythmia is stray electrical signals within the left or right atrium of the heart. The ablation catheter imparts ablative energy (e.g., radiofrequency energy, cryoablation, lasers, chemicals, high-intensity focused ultrasound, etc.) to cardiac tissue to create a lesion in the cardiac tissue. This lesion disrupts undesirable electrical pathways and thereby limits or prevents stray electrical signals that lead to arrhythmias.
Electroporation is a non-thermal ablation technique that involves applying strong electric-fields that induce pore formation in the cellular membrane. The electric field may be induced by applying a relatively short duration pulse which may last, for instance, from a nanosecond to several milliseconds. Such a pulse may be repeated to form a pulse train. When such an electric field is applied to tissue in an in vivo setting, the cells in the tissue are subjected to trans-membrane potential, which opens the pores on the cell wall. Electroporation may be reversible (i.e., the temporally opened pores will reseal) or irreversible (i.e., the pores will remain open). For example, in the field of gene therapy, reversible electroporation (i.e., temporarily open pores) is used to transfect high molecular weight therapeutic vectors into the cells. In other therapeutic applications, a suitably configured pulse train alone may be used to cause cell destruction, for instance by causing irreversible electroporation.
For example, pulsed field ablation (PFA) may be used to perform instantaneous pulmonary vein isolation (PVI). PFA generally involves delivering high voltage pulses from electrodes disposed on a catheter. For example, voltage pulses may range from less than about 500 volts to about 3,000 volts or higher. These fields may be applied between pairs of electrodes (bipolar therapy) or between one or more electrodes and a return patch (monopolar therapy).
Although PFA is non-thermal and demonstrates a high degree of tissue selectivity, which may improve the safety of ablation procedures, there are still practical challenges that must be considered to maintain the improved safety profile. For example, the voltage threshold for cardiac cells is approximately 400 Volts/centimeter (V/cm). In some PFA systems, the therapy spans between electrodes and protrudes deep into the tissue, which may result in voltage gradients surpassing 400 V/cm at locations near the electrodes. If these electrodes are proximate to the phrenic nerve, which provides innervation for the diaphragm, there is a potential for acute phrenic stunning and/or long-term phrenic damage. Accordingly, to reduce the potential for phrenic impact, a physician may avoid ablating in areas near the phrenic nerve or use a lower dosage when ablating near the phrenic nerve.
Traditional methods for detecting phrenic nerve stimulation include placing electrodes in the heart, generating a pacing stimulus in the electrodes, and visually assessing diaphragm stimulation. If there is evidence of diaphragm capture, the physician may assume that the stimulated electrodes are on or near the phrenic nerve. The physician may then use this information to select a lower dosage waveform or to disable specific electrodes. Although straightforward, these traditional methods are time consuming and may be imprecise. As such, there is a need for more efficient and accurate phrenic nerve detection systems and methods.
In one aspect, a method for phrenic nerve stimulation detection is disclosed. The method includes delivering a plurality of pacing pulses between an associated pair of electrodes of a plurality of electrodes, and, for each of the plurality of pacing pulses, measuring a corresponding diaphragm movement during delivery of the pacing pulse. The method further includes determining, for each of the plurality of pacing pulses, based on the corresponding measured diaphragm movement, whether the pacing pulse results in phrenic nerve capture, and recording, for each pacing pulse that results in phrenic nerve capture, the pair of electrodes associated with that pacing pulse.
In another aspect, a system for phrenic stimulation detection is disclosed. The system includes a catheter comprising a proximal end, a distal end, and a plurality of electrodes disposed on the distal end, at least one energy generator connected to the plurality of electrodes, a memory device, and at least one processor. The at least one processor is programmed to cause the at least one energy generator to deliver a plurality of pacing pulses, each pacing pulse delivered between an associated pair of electrodes of the plurality of electrodes. For each of the plurality of pacing pulses, the at least one processor is programmed to measure a corresponding diaphragm movement during delivery of the pacing pulse. The at least one processor is further programmed to determine, for each of the plurality of pacing pulses, based on the corresponding measured diaphragm movement, whether the pacing pulse results in phrenic nerve capture. For each pacing pulse that results in phrenic nerve capture, the pair of electrodes associated with that pacing pulse is recorded in the memory.
The foregoing and other aspects, features, details, utilities, and advantages of the present disclosure will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.
The present disclosure provides systems and methods for automatic detection of phrenic nerve stimulation. A plurality of pacing pulses are delivered between an associated pair of electrodes of a plurality of electrodes. Next, for each of the plurality of pacing pulses, a corresponding diaphragm movement during delivery of the pacing pulse is measured. For each of the plurality of pacing pulses, it is determined, based on the corresponding measured diaphragm movement, whether the pacing pulse results in phrenic nerve capture. For each pacing pulse that results in phrenic nerve capture, the pair of electrodes associated with that pacing pulse is recorded.
System 10 may be used for irreversible electroporation (IRE) to destroy tissue. In particular, system 10 may be used for electroporation-induced therapy that includes delivering electrical current in such a manner as to directly cause an irreversible loss of plasma membrane (cell wall) integrity leading to its breakdown and cell destruction. This mechanism of cell destruction may be viewed as an “outside-in” process, meaning that the disruption of the outside plasma membrane of the cell causes detrimental effects to the inside of the cell. Typically, for classical plasma membrane electroporation, electric current is delivered as a pulsed electric field in the form of short-duration pulses (e.g., having a 10 nanosecond (ns) to 100 millisecond (ms) duration) between closely spaced electrodes capable of delivering an electric field strength of about 0.1 to 3.0 kilovolts/centimeter (kV/cm). In some alternative embodiments, the electric field strength may be higher (e.g., greater than or equal to 3.0 kV/cm). System 10 may be used for high output (e.g., high voltage and/or high current) electroporation procedures. Further, system 10 may be used with a loop catheter such as that depicted in
In one embodiment, stimulation is delivered selectively (e.g., between pairs of electrodes) on catheter 14. Further, the electrodes on catheter 14 may be switchable between being connected to a 3D mapping system and being connected to an electroporation generator.
Irreversible electroporation through a multi-electrode catheter may enable pulmonary vein isolation in as few as one shock per vein, which may produce much shorter procedure times compared to sequentially positioning a radiofrequency (RF) ablation tip around a vein.
It should be understood that while the energization strategies are described as involving DC pulses, embodiments may use variations and remain within the spirit and scope of the disclosure. For example, exponentially-decaying pulses, exponentially-increasing pulses, and combinations may be used. Further, in some embodiments, AC pulses may also be used.
Further, it should be understood that the mechanism of cell destruction in electroporation is not primarily due to heating effects, but rather to cell membrane disruption through application of a high-voltage electric field. Thus, electroporation may avoid some possible thermal effects that may occur when using radio frequency (RF) energy. This “cold therapy” thus has desirable characteristics.
With this background, and now referring again to
In the illustrated embodiment, return electrodes 18, 20, and 21 are patch electrodes. It should be understood that the illustration of a single patch electrode is diagrammatic only (for clarity) and that such sub-systems to which these patch electrodes are connected may, and typically will, include more than one patch (body surface) electrode, and may include split patch electrodes (as described herein). In other embodiments, return electrodes 18, 20, and 21 may be any other type of electrode suitable for use as a return electrode including, for example, one or more catheter electrodes. Return electrodes that are catheter electrodes may be part of electrode assembly 12 or part of a separate catheter or device (not shown). System 10 may further include a main computer system 32 (including an electronic control unit 50 and data storage-memory 52), which may be integrated with localization and navigation system 30 in certain embodiments. System 32 may further include conventional interface components, such as various user input/output mechanisms 34A and a display 34B, among other components.
Electroporation generator 26 is configured to energize the electrode element(s) in accordance with an electroporation energization strategy, which may be predetermined or may be user-selectable. For electroporation therapy, generator 26 may be configured to produce an electric current that is delivered via electrode assembly 12 as a pulsed electric field in the form of short-duration DC pulses (e.g., a nanoseconds to several milliseconds duration, or any duration suitable for electroporation) between closely spaced electrodes capable of delivering an electric field strength (i.e., at the tissue site) of about 0.1 to 3.0 kV/cm. In some alternative embodiments, the electric field strength may be higher (e.g., greater than or equal to 2.0 kV/cm). The amplitude and pulse width needed for irreversible electroporation are inversely related. That is, as pulse widths are decreased, the amplitude may generally be increased to achieve chronaxie.
Electroporation generator 26, sometimes also referred to herein as a DC energy source, is a biphasic electroporation generator 26 configured to generate a series of DC energy pulses that all produce current in two directions (i.e., positive and negative pulses). In other embodiments, electroporation generator is a monophasic or polyphasic electroporation generator. In some embodiments, electroporation generator 26 is configured to output energy in DC pulses at selectable energy levels, such as fifty joules, one hundred joules, two hundred joules, and the like. Other embodiments may have more or fewer energy settings and the values of the available setting may be the same or different. For successful electroporation, some embodiments utilize the two hundred joule output level. For example, electroporation generator 26 may output a DC pulse having a peak magnitude from about 300 Volts (V) to about 3,200 V. Other embodiments may output any other suitable positive or negative voltage.
In some embodiments, a variable impedance 27 allows the impedance of system 10 to be varied to limit arcing. Moreover, variable impedance 27 may be used to change one or more characteristics, such as amplitude, duration, pulse shape, and the like, of an output of electroporation generator 26. Although illustrated as a separate component, variable impedance 27 may be incorporated in catheter 14 or generator 26.
With continued reference to
In the illustrative embodiment, catheter 14 includes a cable connector or interface 40, a handle 42, and a shaft 44 having a proximal end 46 and a distal 48 end. Catheter 14 may also include other conventional components not illustrated herein such as a temperature sensor, additional electrodes, and corresponding conductors or leads. Connector 40 provides mechanical and electrical connection(s) for cable 56 extending from generator 26. Connector 40 may include conventional components known in the art and as shown is disposed at the proximal end of catheter 14.
Handle 42 provides a location for the clinician to hold catheter 14 and may further provide means for steering or the guiding shaft 44 within body 17. For example, handle 42 may include means to change the length of a guidewire extending through catheter 14 to distal end 48 of shaft 44 or means to steer shaft 44. Moreover, in some embodiments, handle 42 may be configured to vary the shape, size, and/or orientation of a portion of the catheter, and it will be understood that the construction of handle 42 may vary. In an alternate embodiment, catheter 14 may be robotically driven or controlled. Accordingly, rather than a clinician manipulating a handle to advance/retract and/or steer or guide catheter 14 (and shaft 44 thereof in particular), a robot is used to manipulate catheter 14. Shaft 44 is an elongated, tubular, flexible member configured for movement within body 17. Shaft 44 is configured to support electrode assembly 12 as well as contain associated conductors, and possibly additional electronics used for signal processing or conditioning. Shaft 44 may also permit transport, delivery and/or removal of fluids (including irrigation fluids and bodily fluids), medicines, biologics, and/or surgical tools or instruments. Shaft 44 may be made from conventional materials such as polyurethane and defines one or more lumens configured to house and/or transport electrical conductors, fluids or surgical tools, as described herein. Shaft 44 may be introduced into a blood vessel or other structure within body 17 through a conventional introducer. Shaft 44 may then be advanced/retracted and/or steered or guided through body 17 to a desired location such as the site of tissue 16, including through the use of guidewires or other means known in the art.
Localization and navigation system 30 may be provided for visualization, mapping and navigation of internal body structures. Localization and navigation system 30 may include conventional apparatus known generally in the art. For example, localization and navigation system 30 may be substantially similar to the EnSite Precision™ System, commercially available from Abbott Laboratories, and as generally shown in commonly assigned U.S. Pat. No. 7,263,397 titled “Method and Apparatus for Catheter Navigation and Location and Mapping in the Heart”, the entire disclosure of which is incorporated herein by reference. In another example, localization and navigation system 30 may be substantially similar to the EnSite X™ Mapping System, as generally shown in U.S. Pat. App. Pub. No. 2020/0138334 titled “Method for Medical Device Localization Based on Magnetic and Impedance Sensors”, the entire disclosure of which is incorporated herein by reference. It should be understood, however, that localization and navigation system 30 is an example only, and is not limiting in nature. Other technologies for locating/navigating a catheter in space (and for visualization) are known, including for example, the CARTO navigation and location system of Biosense Webster, Inc., the Rhythmia® system of Boston Scientific Scimed, Inc., the KODEX® system of Koninklijke Philips N.V., the AURORA® system of Northern Digital Inc., or commonly available fluoroscopy systems.
In this regard, some of the localization, navigation and/or visualization systems may include one or more sensors for producing signals indicative of catheter location information, and may include, for example, one or more electrodes in the case of an impedance-based localization system, or alternatively, one or more coils (i.e., wire windings) configured to detect one or more characteristics of a magnetic field, for example in the case of a magnetic-field based localization system. As yet another example, system 10 may utilize a combination electric field-based and magnetic field-based system as generally shown with reference to U.S. Pat. No. 7,536,218 entitled “Hybrid Magnetic-Based and Impedance Based Position Sensing,” the disclosure of which is incorporated herein by reference in its entirety.
Pulsed field ablation (PFA), which is a methodology for achieving irreversible electroporation, may be implemented using the systems and methods described herein. In some cases, PFA may be used at specific cardiac tissue sites such as the pulmonary veins to perform a pulmonary vein isolation (PVI). In the example embodiment, electric fields are applied between adjacent electrodes (in a bipolar approach). Alternatively, electric fields may be applied between one or more electrodes and a return patch (in a monopolar approach). There are advantages and disadvantages to each of these approaches.
For lesion size and proximity, the monopolar approach has a wider range of effect, and can potentially create deeper lesions with the same applied voltage. Further, the monopolar approach may be able to create lesions from a distance (e.g., generally proximate, but not necessarily contacting tissue). The bipolar approach may create smaller lesions, requiring closer proximity or contact with tissue to create transmural lesions. However, the monopolar approach may create larger lesions than are necessary, while the lesions generated using the bipolar approach may be more localized.
Due to a wider range of effect, the monopolar approach may cause unwanted skeletal muscle and/or nerve activation. In contrast, the bipolar approach has a constrained range of effect proportional to electrode spacing on the lead, and is less likely to depolarize cardiac myocytes or nerve fibers.
To monitor operation of system 10, one or more impedances between catheter electrodes 144 and/or return electrodes 18, 20, and 21 may be measured. For example, for system 10, impedances may be measured as described in U.S. Patent Application Publication No. 2019/0117113, filed on Oct. 23, 2018, U.S. Patent Application Publication No. 2019/0183378, filed on Dec. 19, 2018, and International Patent Application Publication No. WO 2021/236341, filed on May 6, 2021, all of which are incorporated by reference herein in their entirety.
Variable diameter loop 150 is selectively transitionable between an expanded (also referred to as “open”) diameter 160 (shown in
In the embodiment shown, variable diameter loop 150 includes fourteen catheter electrodes 144 substantially evenly spaced around the circumference of variable diameter loop 150 in the expanded configuration. In the retracted configuration, one or more of electrodes 144 may overlap. In other embodiments, other arrangements of catheter electrodes 144 may be implemented. For example, in one embodiment, variable diameter loop 150 includes twelve catheter electrodes 144.
Catheter electrodes 144 are platinum ring electrodes configured to conduct and/or discharge electrical current in the range of one thousand volts and/or ten amperes. In other embodiments, variable diameter loop 150 may include any suitable number of catheter electrodes 144 made of any suitable material. Catheter electrodes 144 may include any catheter electrode suitable to conduct high voltage and/or high current (e.g., in the range of one thousand volts and/or ten amperes). Each catheter electrode 144 is separated from each other catheter electrode by an insulated gap 152. In the example embodiment, each catheter electrode 144 has a same length 164 (shown in
Diameter 160 and catheter electrode 144 spacing may be developed to provide a targeted range of energy density to tissue, as well as to provide sufficient electroporation coverage for different human anatomic geometries. In general, a sufficient number of electrodes 144 with appropriate lengths 164 are desired to provide substantially even and continuous coverage around the circumference of variable diameter loop 150, while still allowing enough flexibility to allow variable diameter loop 150 to expand and contract to vary diameter 160 to the desired extremes.
As mentioned above, length 164 of catheter electrodes 144 may be varied. Increasing length 164 of catheter electrodes 144 may increase coverage of electrodes 144 around the circumference of variable diameter loop 150 while also decreasing current density (by increasing the surface area) on electrodes 144, which may help prevent arcing during electroporation operations. Increasing length 164 too much, however, may prevent variable diameter loop 150 from forming a smooth circular shape and may limit the closed diameter 160 of variable diameter loop 150. Additionally, too great a length 164 may increase the surface area of catheter electrodes 144 to a point that the current density applied to catheter electrodes 144 by a power source is below the minimum current density needed for successful therapy. Conversely, decreasing length 164 decreases the surface area, thereby increasing the current density (assuming no other system changes) on catheter electrodes 144. As discussed above, greater current densities may lead to increased risk of arcing during electroporation, and may result in larger additional system resistances needing to be added to prevent arcing. Moreover, in order to get a desired, even coverage about the circumference of variable diameter loop 150, more catheter electrodes 144 may be needed if length 164 is decreased. Increasing the number of catheter electrodes 144 on variable diameter loop 150 may prevent variable diameter loop 150 from being able to be contracted to a desired minimum diameter 160.
Each spline 204 includes a proximal end 210 coupled to shaft 202 and a distal end 212 coupled to shaft 202. From proximal end 210 to distal end 212, spline 204 has an arcuate shape that extends radially outward.
In this embodiment, each spline 204 includes one or a plurality of individual electrodes 220. For example, each spline 204 may include an elastic material (e.g., Nitinol) covered in a polymer tube 222, with individual electrodes 220 attached to an exterior of polymer tube 222. In the embodiment shown, each spline 204 includes two electrodes 220. Further, as shown in
Alternatively, each spline 204 may include any suitable number and arrangement of electrodes 220. For example, in some embodiments, each spline 204 includes four electrodes 220.
In this embodiment, alternating splines 204 alternate polarities. That is, electrodes 220 on a particular spline 204 have the same polarity, but electrodes 220 on a particular spline 204 have a different polarity than electrodes 220 on adjacent splines 204. Alternatively, any suitable polarization scheme may be used. During delivery, splines 204 may be collapsed in towards shaft 202. Subsequently, to perform ablation, splines 204 are deployed to extend radially outward.
Splines 204 may all have the same length, or at least some of splines 204 may have different lengths. Further, insulating material on each spline 204 may have the same length, or at least some splines 204 may have insulating material with different lengths. In addition, in some embodiments, catheter assembly 200 includes a distal electrode (not shown) positioned distal of splines 204. The distal electrode may be used to perform point ablation (e.g., by creating a bipole between the distal electrode and one of splines 204), and/or may be used for visualization/mapping purposes (e.g., using the distal electrode in combination with an electrode on shaft 202).
Catheter assembly 250 includes a shaft 252 and a plurality of splines 254 surrounding a distal portion 256 of shaft 252. In this embodiment, catheter assembly 250 includes a balloon 258 enclosed by splines 254. Balloon 258 may be selectively inflated to occupy the space between splines 254. Notably, balloon 258 functions as an insulator, and generally reduces energy, which may result in increased lesion size.
Each spline 254 includes a proximal end 260 coupled to shaft 252 and a distal end 262 coupled to shaft 252. From proximal end 260, spline 1004 extends radially outward to an inflection point 264, and then extends radially inward to distal end 262.
A body of each spline 254 is made of an elastic material (e.g., Nitinol), and functions as a relatively large electrode. In this embodiment, alternating splines 254 alternate polarities. That is, each positive spline 254 is positioned between two negative splines 254 and vice-versa. Alternatively, any suitable polarization scheme may be used.
To control the ablation zone of each spline 254, portions of each spline 254 may be covered with insulating material 270 (e.g., heat-shrink or polymer tubing or spray or dip coat with polyimide or PEBAX), and the exposed portions of splines 254 function as electrodes. In the embodiment shown in
During delivery, splines 254 and balloon 258 may be collapsed. To perform ablation, splines 254 are deployed with inflection points 264 extending radially outward, and balloon 258 is selectively inflated to occupy the space between splines 254.
The combination of balloon 258 and splines 254 facilitates straightforward delivery and deployment of catheter assembly 250. Further, balloon 258 drives more energy into ablated tissue, and stabilizes splines 254 to prevent lateral movement. In addition, using splines 254 as electrodes instead of individual smaller electrodes may facilitate reducing the cost and increasing the reliability of catheter assembly 250.
Splines 254 may all have the same length, or at least some of splines 254 may have different lengths. Further, insulating material 270 on each spline 254 may have the same length, or at least some splines 254 may have insulating material 270 with different lengths. In addition, in some embodiments, catheter assembly 250 includes a distal electrode (not shown) positioned distal of splines 254. The distal electrode may be used to perform point ablation (e.g., by creating a bipole between the distal electrode and one of splines 254), and/or may be used for visualization/mapping purposes (e.g., using the distal electrode in combination with an electrode on shaft 252).
Catheter assembly 280 includes a plurality of splines 284 extending from a proximal end 286 to a distal end 288. Each spline 284 includes a plurality of electrodes 290. In the embodiment shown in
Using catheter assembly 280, lesions may be generated at individual electrodes 290 using a monopolar approach (e.g., by applying a voltage between individual electrodes 290 and a return patch) or generated between pairs of electrodes 290 using a bipolar approach. Lesions may be generating within an anatomy by selectively energizing electrodes in a particular configuration and/or pattern (e.g., including energizing individual electrodes 290 independent of one another, or energizing multiple electrodes 290 simultaneously).
Those of skill the art will appreciate that catheter assembly 146 (shown in
For electroporation therapy, waveforms are generated using a pulse generator (e.g., electroporation generator 26 (shown in
To generate different waveforms, the pulse generator selectively connects different electrodes to different voltage levels. In at least some known systems, a first subset of electrodes is selectively connectable to a first voltage level (e.g., a positive voltage), and a second subset of electrodes is selectively connectable to a second voltage level (e.g., a negative voltage).
The voltage threshold for cardiac cells is approximately 400 Volts/centimeter (V/cm) (e.g., field strengths below 400 V/cm may be insufficient to damage cardiac cells). In general, PFA therapy spans between electrodes and protrudes deep into the tissue, with voltage gradients surpassing 400 V/cm generally being achieved at locations near the electrodes. Given the relatively high field strength during PFA, if these electrodes are sufficiently proximate the phrenic nerve, which provides innervation for the diaphragm, there is potential for acute phrenic stunning and/or long-term phrenic damage as a result of the therapy. Accordingly, to reduce the potential for phrenic impact, a physician may avoid ablating in areas near the phrenic nerve or use a lower dosage when ablating near the phrenic nerve. Methods for automatic phrenic nerve monitoring are described herein. The automatic phrenic nerve monitoring may be implemented using, for example, system 10 (shown in
Diaphragm movement may be measured using any suitable systems or methods. For example, in some embodiments, diaphragm movement is measured using one or more imaging systems. For example, in some embodiments, diaphragm movement is measured using a fluoroscopy system, a transesophageal echocardiogram (TEE) system, and/or an intracardiac echocardiography (ICE) system. Additionally, or alternatively, diaphragm movement is measured using a video or still images from a video, followed by imaging processing (e.g., processing the video and/or images through an algorithm).
In some embodiments, diaphragm movement is measured using a navigation system. In further embodiments, diaphragm movement is measured using a three-dimensional navigation system. For example, in some embodiments, diaphragm movement is measured using a magnetic-based, impedance-based, fiber optic-based, and/or radiofrequency-based navigation system.
Returning to
At block 506, pacing pulses are delivered to sequentially to the electrodes of electrode assembly 12. In a bipolar approach, the pacing pulses may be applied between pairs of electrodes on electrode assembly 12. The pairs of electrodes may include electrodes that are adjacent to each other. In a monopolar approach, the pacing pulses are delivered to a single electrode of electrode assembly 12. The pacing pulses may be delivered sequentially to the electrodes of electrode assembly 12 for a predetermined period of time. For example, in some embodiments, the pacing pulses are delivered for a period of 500 milliseconds (ms) or less.
Returning to
The electrical current of the pacing pulses may be sufficiently high to stimulate the phrenic nerve, but low enough as to not cause any damage to the phrenic nerve. For example, in some embodiments, the pacing pulses are 20 milliamps (mA) or less. In further embodiments, the pacing pulses are in the range of 5-10 mA. Monitoring delivery of the pacing pulses provides information as to the distance between the one or more electrodes being stimulated and the phrenic nerve. In some embodiments, one or more capture thresholds may be determined for electrodes demonstrating phrenic nerve capture. A capture threshold, as used herein, refers to the minimum amount of electrical current necessary to stimulate the phrenic nerve. A capture threshold may be determined before, during, and/or after a therapy application, as discussed in more detail below. Further, a change in the capture threshold may be indicative of an impact of ablation therapy on the phrenic nerve, which may further inform if stunning or damage could occur with future therapy applications.
At block 506, diaphragm movement is measured, the measurements coinciding with the delivery of the pacing pulses with some deterministic delay. Diaphragm movement is measured by any of the systems and methods described above (e.g., one or more sensors, one or more body patches, an imaging system, and/or a navigation system). The diaphragm movement may be continually monitored as the pacing pulses are delivered sequentially to each pair of electrodes of the electrode assembly. For example, as discussed above, in
Returning to
If phrenic nerve capture is detected, the method proceeds to block 510. At block 510, electrode pairs which were determined to have captured the phrenic nerve are logged or recorded. The pacing pulses output by those pairs of electrodes may also be logged or recorded. In some embodiments, this information may be stored in a storage device of the system, such as data storage-memory 52. Additionally, or alternatively, this information may be sent to the localization and navigation system 30 of system 10. Localization and navigation system 30 may use this information to determine phrenic nerve capture locations. Localization and navigation system 30 may further visually identify phrenic nerve capture locations on a user interface on the display 34B. For example, phrenic nerve capture locations may be displayed on a 3D map generated by localization and navigation system 30 and displayed on the user interface of display 34B. The phrenic nerve capture location may be visually identified in relation to catheter 14 and/or the target tissue.
Next, a phrenic nerve safe ablation therapy may be performed at block 512. The ablation therapy may be an electroporation therapy, such as PFA. The phrenic nerve safe ablation therapy may include modifying the pulse parameters or disabling electrodes determined to have caused phrenic nerve capture. For example, if a high voltage waveform is to be used, electrodes determined to have caused phrenic capture may be disabled from applying that waveform. If a low voltage waveform is used, then a modified waveform may be used on electrodes determined to have caused phrenic capture. For example, the modified waveform may include a lower energy waveform that will eliminate or greatly reduce any impact on the phrenic nerve.
For example, in the embodiment illustrated in
Returning to
Returning to
At block 520, it is determined whether the therapy is complete. If the therapy is not complete, method 500 returns to block 504, and catheter 14 remains positioned at the target tissue site or is positioned at another target tissue site. Optionally, one or more additionally ablation therapy applications may be performed before returning to block 504. Therefore, in some embodiments, pacing occurs in between ablation therapy applications. In other embodiments, pacing occurs after a plurality of ablation therapy applications. Once therapy is complete, method 500 ends at block 522.
In some embodiments, one or more capture thresholds may be determined for electrodes demonstrating phrenic nerve capture. A capture threshold may refer to the minimum amount of electrical current necessary to stimulate the phrenic nerve. In some embodiments, a first capture threshold may be determined for an electrode pair demonstrating phrenic nerve capture before an ablation therapy application. A second capture threshold may then be determined for that electrode pair after an ablation therapy application, or in-between bursts during an ablation therapy application. The second capture threshold may be compared to the first capture threshold. If the second capture threshold is greater than the first capture threshold, this may indicate an impact of PFA therapy on the phrenic nerve. For example, this may indicate to a clinician that stunning or damage may occur with further therapy applications. In some embodiments, if there is an increase in capture threshold (i.e., the second capture threshold is greater than the first capture threshold), then the system may automatically stop delivering therapy and/or begin delivering phrenic safe therapy. Additionally, or alternatively, the increase in capture threshold may be indicated on display 34B, and the clinician may determine whether to stop the therapy and/or begin delivering phrenic safe therapy. In some embodiments, an increase in capture threshold may be also accompanied by a visual or audio alarm.
Although certain embodiments of this disclosure have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this disclosure. All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present disclosure, and do not create limitations, particularly as to the position, orientation, or use of the disclosure. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the disclosure as defined in the appended claims.
When introducing elements of the present disclosure or the preferred embodiment(s) thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
This application claims priority to U.S. Provisional Patent Application No. 63/449,373 filed on Mar. 2, 2023, which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63449373 | Mar 2023 | US |
