Patent Application
20190159800
The present application generally relates to systems and methods for creating ablation zones in human tissue. More specifically, the present application relates to the treatment of atrial fibrillation of the heart by using ultrasound energy. While the present application emphasizes treatment of atrial fibrillation, one of skill in the art will appreciate that this it not intended to be limiting, and that the systems and methods disclosed herein may also be used to treat other arrhythmias such as ventricular fibrillation.
The condition of atrial fibrillation is characterized by the abnormal (usually very rapid) beating of the left atrium of the heart which is out of synch with the normal synchronous movement (‘normal sinus rhythm’) of the heart muscle. In normal sinus rhythm, the electrical impulses originate in the sino-atrial node (‘SA node’) which resides in the right atrium. The abnormal beating of the atrial heart muscle is known as ‘fibrillation’ and is caused by electrical impulses originating instead at points other than the SA node, for example, in the pulmonary veins (PV).
There are pharmacological treatments for this condition with varying degree of success. In addition, there are surgical interventions aimed at removing the aberrant electrical pathways from PV to the left atrium (‘LA’) such as the ‘Cox-Maze III Procedure’. This procedure has been shown to be 99% effective but requires special surgical skills and is time consuming. Thus, there has been considerable effort to copy the Cox-Maze procedure using a less invasive percutaneous catheter-based approach. Less invasive treatments have been developed which involve use of some form of energy to ablate (or kill) the tissue surrounding the aberrant focal point where the abnormal signals originate in PV. The most common methodology is the use of radio-frequency (‘RF’) electrical energy to heat the muscle tissue and thereby ablate it. The aberrant electrical impulses are then prevented from traveling from PV to the atrium (achieving the ‘conduction block’) and thus avoiding the fibrillation of the atrial muscle. Other energy sources, such as microwave, laser, and ultrasound have been utilized to achieve the conduction block. In addition, techniques such as cryoablation, administration of ethanol, and the like have also been used. Some of these methods and devices are described below.
There has been considerable effort in developing catheter based systems for the treatment of AF using radiofrequency (RF) energy. One such method includes a catheter having distal and proximal electrodes at the catheter tip. The catheter can be bent in a coil shape, and positioned inside a pulmonary vein. The tissue of the inner wall of the PV is ablated in an attempt to kill the source of the aberrant heart activity.
Another source used in ablation is microwave energy. One such intraoperative device consists of a probe with a malleable antenna which has the ability to ablate the atrial tissue.
Still another catheter based method utilizes the cryogenic technique where the tissue of the atrium is frozen below a temperature of −60 degrees C. This results in killing of the tissue in the vicinity of the PV thereby eliminating the pathway for the aberrant signals causing the AF. Cryo-based techniques have also been a part of the partial Maze procedures described above. More recently, Dr. Cox and his group have used cryoprobes (cryo-Maze) to duplicate the essentials of the Cox-Maze III procedure.
More recent approaches for the treatment of AF involve the use of ultrasound energy. The target tissue of the region surrounding the pulmonary vein is heated with ultrasound energy emitted by one or more ultrasound transducers. One such approach includes a catheter distal tip portion equipped with a balloon and containing an ultrasound element. The balloon serves as an anchoring means to secure the tip of the catheter in the pulmonary vein. The balloon portion of the catheter is positioned in the selected pulmonary vein and the balloon is inflated with a fluid which is transparent to ultrasound energy. The transducer emits the ultrasound energy which travels to the target tissue in or near the pulmonary vein and ablates it. The intended therapy is to destroy the electrical conduction path around a pulmonary vein and thereby restore the normal sinus rhythm. The therapy involves the creation of a multiplicity of lesions around individual pulmonary veins as required.
Yet another catheter device using ultrasound energy includes a catheter having a tip with an array of ultrasound elements in a grid pattern for the purpose of creating a three dimensional image of the target tissue. An ablating ultrasound transducer is provided which is in the shape of a ring which encircles the imaging grid. The ablating transducer emits a ring of ultrasound energy at 10 MHz frequency.
In all above approaches, the inventions involve the ablation of tissue inside a pulmonary vein or of the tissue at the location of the ostium. This may require complex positioning and guiding of the treatment devices to the target site. The ablation is achieved by means of contact between the device and the tissue. Therefore, it would be advantageous to provide an ablation system that does not require such precise positioning and tissue contact and that can create a conduction block in the atrium adjacent the pulmonary vein or around a plurality of pulmonary veins in a single treatment. Moreover, it would be desirable to provide a device and methods of ablation where three dimensional movement of the tip is controlled such that one can create a contiguous lesion in the tissue of desired shape in the wall of the chamber, e.g. the atrium of the heart. Furthermore, the movement of the ultrasound beam is controlled in a manner such that the beam is presented to the target tissue substantially at a right angle to maximize the efficiency of the ablation process. It would also be desirable to provide an ablation system that is easy to use, easy to manufacture and that is lower in cost than current commercial systems.
Patents related to the treatment of atrial fibrillation include, but are not limited to the following: U.S. Pat. Nos. 6,997,925; 6,996,908; 6,966,908; 6,964,660; 6,955,173; 6,954,977; 6,953,460; 6,949,097; 6,929,639; 6,872,205; 6,814,733; 6,780,183; 6,666,858; 6,652,515; 6,635,054; 6,605,084; 6,547,788; 6,514,249; 6,502,576; 6,416,511; 6,383,151; 6,305,378; 6,254,599; 6,245,064; 6,164,283; 6,161,543; 6,117,101; 6,064,902; 6,052,576; 6,024,740; 6,012,457; 5,405,346; 5,314,466; 5,295,484; 5,246,438; and 4,641,649.
Patent Publications related to the treatment of atrial fibrillation include, but are not limited to International PCT Publication No. WO 99/02096; and U.S. Patent Publication No. 2005/0267453.
Scientific publications related to the treatment of atrial fibrillation include, but are not limited to: Haissaguerre, M. et al., Spontaneous Initiation of Atrial Fibrillation by Ectopic Beats Originating in the Pulmonary Veins, New England J. Med., Vol. 339:659-666; J. L. Cox et al., The Development of the Maze Procedure for the Treatment of Atrial Fibrillation, Seminars in Thoracic & Cardiovascular Surgery, 2000; 12: 2-14; J. L. Cox et al., Electrophysiologic Basis, Surgical Development, and Clinical Results of the Maze Procedure for Atrial Flutter and Atrial Fibrillation, Advances in Cardiac Surgery, 1995; 6: 1-67; J. L. Cox et al., Modification of the Maze Procedure for Atrial Flutter and Atrial Fibrillation. II, Surgical Technique of the Maze III Procedure, Journal of Thoracic & Cardiovascular Surgery, 1995; 110:485-95; J. L. Cox, N. Ad, T. Palazzo, et al. Current Status of the Maze Procedure for the Treatment of Atrial Fibrillation, Seminars in Thoracic & Cardiovascular Surgery, 2000; 12: 15-19; M. Levinson, Endocardial Microwave Ablation: A New Surgical Approach for Atrial Fibrillation; The Heart Surgery Forum, 2006; Maessen et al., Beating Heart Surgical Treatment of Atrial Fibrillation with Microwave Ablation, Ann Thorac Surg 74: 1160-8, 2002; A. M. Gillinov, E. H. Blackstone and P. M. McCarthy, Atrial Fibrillation: Current Surgical Options and their Assessment, Annals of Thoracic Surgery 2002; 74:2210-7; Sueda T., Nagata H., Orihashi K., et al., Efficacy of a Simple Left Atrial Procedure for Chronic Atrial Fibrillation in Mitral Valve Operations, Ann Thorac Surg 1997; 63:1070-1075; Sueda T., Nagata H., Shikata H., et al.; Simple Left Atrial Procedure for Chronic Atrial Fibrillation Associated with Mitral Valve Disease, Ann Thorac Surg 1996; 62:1796-1800; Nathan H., Eliakim M., The Junction Between the Left Atrium and the Pulmonary Veins, An Anatomic Study of Human Hearts, Circulation 1966; 34:412-422; Cox J. L., Schuessler R. B., Boineau J. P., The Development of the Maze Procedure for the Treatment of Atrial Fibrillation, Semin Thorac Cardiovasc Surg 2000; 12:2-14; and Gentry et al., Integrated Catheter for 3-D Intracardiac Echocardiography and Ultrasound Ablation, IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 51, No. 7, pp 799-807.
The present application generally relates to systems and methods for creating ablation zones in human tissue. More specifically, the present application relates to the treatment of atrial fibrillation of the heart by using ultrasound energy.
In a first aspect of the present invention, a tissue ablation system for treating fibrillation in a patient comprises a steerable interventional catheter having an energy source that emits a beam of energy that ablates tissue and creates a conduction block therein. The conduction block blocks aberrant electrical pathways in the tissue so as to reduce or eliminate the fibrillation. A handle is disposed near a proximal end of the interventional catheter and has an actuation mechanism for steering the interventional catheter. A console is used to control the system and provides power thereto. A display pod is electrically coupled with the console and has a display panel to display system information to a physician or other operators and allows the operators to control the system. A catheter pod is releasably coupled with the handle both electrically and mechanically, and also electrically coupled with the display pod.
The system may also include a bedside monitor or a connection thereto. The power contained in the beam of energy may be in the range of 2 to 10 watts. A distal portion of the interventional catheter may comprise a plurality of resilient shaping wires. The shaping wires may form a shepherd's hook along the interventional catheter when the distal portion is unconstrained. The distal portion may be substantially linear when constrained. The system may have a plurality of actuatable wires coupled with a distal portion of the catheter. Actuation of the wires may deflect the catheter from a substantially linear configuration to a configuration having a shepherd's hook along the catheter. The system may further comprise a single use, sterile adaptor disposed between a proximal end of the handle and the catheter pod. The adaptor may be electrically and mechanically coupled with the handle and the catheter pod. The adaptor may permit the handle to be connected to and unconnected from the catheter pod while maintaining sterility thereof.
In another aspect of the present invention, a tissue ablation system for treating fibrillation in a patient comprises a steerable elongate flexible shaft having a proximal end and a distal end, and a housing coupled to the elongate flexible shaft near the distal end thereof. An energy source is disposed adjacent the housing and is adapted to emit a beam of energy to ablate tissue and create a conduction block therein. The conduction block blocks aberrant electrical pathways in the tissue so as to reduce or eliminate the fibrillation. The system may further comprise a fluid flowing through the housing and in fluid communication with the energy source. The housing may be closed at a distal end thereof, or the housing may comprise one or more apertures near a distal end thereof to allow the fluid to exit the housing. The apertures may allow flow of fluid out of the housing but fluid outside the housing may be inhibited from entering into the housing via the apertures. The housing may also comprise a castellated distal region, and the housing may be substantially cylindrical. At least a portion of the housing may be transparent to the beam of energy. The housing may be resilient and deflects when pressed against the tissue. One or more electrodes or whiskers may be disposed in the housing for contacting the tissue. The housing may also include a flow deflector for directing fluid flow past the energy source. The power contained in the beam of energy may be in the range from 2 to 10 watts. Also, a distal portion of the elongate flexible shaft may comprise a plurality of resilient shaping wires that form a shepherd's hook along the shaft when the distal portion is unconstrained. The distal portion may be substantially linear when constrained. The system may have a plurality of actuatable wires coupled with a distal portion of the shaft. Actuation of the wires may deflect the shaft from a substantially linear configuration to a configuration having a shepherd's hook along the shaft.
In still another aspect of the present invention, a tissue ablation catheter for treating fibrillation in a patient comprises a steerable shaft having a central lumen extending between a proximal end and a distal end thereof, and an elongate flexible shaft slidably disposed in the lumen. The shaft has a proximal end and a distal end. A housing is coupled to the elongate flexible shaft near the distal end thereof and an energy source is disposed adjacent the housing. The energy source is adapted to emit a beam of energy to ablate tissue and create a conduction block therein. The conduction block blocks aberrant electrical pathways in the tissue so as to reduce or eliminate the fibrillation. Steering the shaft directs the energy beam to different regions of the tissue.
The central lumen may be lined with a spring and a plurality of pullwires may be slidably disposed in pullwire lumens extending between the proximal and distal ends of the steerable shaft. The pullwire lumens may be lined with springs. Any of the springs may be encased in a soft matrix of flexible material. The pullwire lumens may be circumferentially disposed around the central lumen. The power contained in the beam of energy may be in the range of 2 to 10 watts. Additionally, a distal portion of the steerable shaft may comprise a plurality of resilient shaping wires that form a shepherd's hook along the shaft when the distal portion is unconstrained. The distal portion may be substantially linear when constrained. A plurality of actuatable wires may be coupled with a distal portion of the shaft. Actuation of the wires may deflect the shaft from a substantially linear configuration to a configuration having a shepherd's hook along the shaft.
In yet another aspect of the present invention, a tissue ablation catheter for treating atrial fibrillation in a patient comprises a steerable elongate flexible shaft having a proximal end and a distal end, and a housing is coupled to the elongate flexible shaft near the distal end thereof. A non-expandable reflector element is disposed in the housing, and an energy source is disposed adjacent the housing. The reflector element may be a rigid, fixed size element having a planar surface or a curved surface. The energy source is adapted to emit energy, wherein the energy is reflected off the reflector forming a beam of energy directed to tissue. The energy beam ablates the tissue and creates a conduction block therein. The conduction block blocks aberrant electrical pathways in the tissue so as to reduce or eliminate the fibrillation. The power contained in the beam of energy may be in the range of 2 to 10 watts. Additionally, a distal portion of the steerable shaft may comprise a plurality of resilient shaping wires that form a shepherd's hook along the shaft when the distal portion is unconstrained. The distal portion may be substantially linear when constrained. A plurality of actuatable wires may be coupled with a distal portion of the shaft. Actuation of the wires may deflect the shaft from a substantially linear configuration to a configuration having a shepherd's hook along the shaft.
In another aspect of the present invention, a system for ablating tissue in a patient comprises a steerable elongate flexible shaft having a proximal end, a distal end, and a diameter. A housing is coupled to the elongate flexible shaft near the distal end thereof. The housing has a length, and a diameter greater than the diameter of the elongate flexible shaft. An energy source is disposed adjacent the housing and is adapted to emit a beam of energy. The energy beam ablates the tissue and creates a conduction block therein. The conduction block blocks aberrant electrical pathways in the tissue so as to reduce or eliminate fibrillation. The system also includes a sheath having a proximal end and a distal end. The steerable elongate flexible shaft is slidably disposed in the sheath. A curved distal region of the sheath is configured to accommodate passage of the housing therethrough when the distal region of the sheath is deflected into a curve. The distal region may comprise an enlarged region or an aperture cut out of the sheath that accommodates the housing length and diameter.
In another aspect of the present invention, a method for ablating tissue in a patient as a treatment for fibrillation comprises positioning a transseptal sheath across an atrial septum. The transseptal sheath has a lumen extending therethrough. Advancing an interventional catheter through the transseptal sheath lumen disposes at least a portion of the interventional catheter in a left atrium of the patient. The interventional catheter comprises an energy source near a distal end thereof. A target treatment region to be ablated is located and the interventional catheter is steered within the left atrium so that the energy source is moved adjacent the target treatment region and also so that energy emitted from the energy source is directed toward the target treatment region. Tissue in the target region is ablated with the emitted energy thereby creating a conduction block in the tissue that blocks aberrant electrical pathways in the tissue so as to reduce or eliminate the fibrillation. Isolation of the target region from the remainder of the atrium is then confirmed.
The ablating step may comprise ablating the tissue with an ultrasound beam of energy from the energy source having power in the range of 2 to 10 watts. The ablating step may comprise ablating a spot in the tissue, a line, a closed loop path in the tissue, or a path encircling one or more pulmonary veins in the left atrium. The ablating step may also comprise ablating a path encircling at least one left pulmonary vein and at least one right pulmonary vein.
The steering step may comprise actuating a plurality of pullwires disposed in the interventional catheter so as to bend a distal portion of the interventional catheter along at least two axes. Steering may also comprise unconstraining a distal portion of the interventional catheter so that shaping wires in the interventional catheter cause the catheter to resiliently take on a shepherd's hook shape. The steering step may comprises actuating a plurality of actuatable wires coupled with a distal portion of the interventional catheter, thereby deflecting the catheter from a substantially linear configuration to a configuration having a shepherd's hook along the catheter. The locating step may comprise actuating the interventional catheter in a raster pattern, and the locating step may also comprise locating a pulmonary vein.
In yet another aspect of the present invention, a method for ablating tissue in a patient as a treatment for fibrillation comprises positioning a transseptal sheath having a lumen therethrough, across an atrial septum, and advancing an interventional catheter through the transseptal sheath such that at least a portion of the interventional catheter is disposed in a left atrium. Ostia of the left pulmonary veins are then located and a first contiguous lesion path encircling at least one ostium of the left pulmonary veins is defined. Tissue along the first defined lesion path is ablated and then the interventional catheter may be positioned adjacent the right pulmonary veins so that the ostia of the right pulmonary veins may be located. A second contiguous lesion path encircling at least one ostium of the right pulmonary veins is defined and tissue along the second path is ablated. Tissue between the first and the second lesion paths is ablated such that a first substantially linear path contiguous with both the first and second lesion paths is created. Also, a second substantially linear path contiguous with the first substantially linear path and extending toward the mitral valve is ablated. Isolation of the left and right pulmonary veins is confirmed. The ablation paths create a conduction block in the tissue that blocks aberrant electrical pathways in the tissue so as to reduce or eliminate the fibrillation.
The step of locating the ostia of the right or left pulmonary veins may comprise actuating the interventional catheter in a raster pattern. Ablating tissue along the first or the second defined lesion paths may comprise ablating the tissue with a beam of ultrasound energy in the range of 2 to 10 watts. The interventional catheter may be actuated to move the catheter distal end in a closed loop. The first or the second defined lesion paths may be modified. Positioning of the interventional catheter adjacent the right pulmonary veins may comprise unconstraining a distal portion of the interventional catheter so that shaping wires in the interventional catheter cause the catheter to resiliently take on a shepherd's hook shape. Positioning of the interventional catheter adjacent the right pulmonary veins may comprise actuating a plurality of actuatable wires coupled with a distal portion of the interventional catheter thereby deflecting the catheter from a substantially linear configuration to a configuration having a shepherd's hook along the catheter.
These and other embodiments are described in further detail in the following description related to the appended drawing figures.
An exemplary embodiment of an ablation system is shown in
Catheter 10 is introduced into the right atrium 44 through a sheath 46 having a bend 140 near the distal end. The housing 16 of the catheter 10 can be manipulated inside the right atrial chamber 44 to position the catheter adjacent various regions of the chamber such as the right pulmonary veins RPV, left pulmonary veins LPV, or the mitral valve MV. As discussed later, the housing 16 emits an energy beam 52 towards the atrial tissue 48. The beam can be directed in any desired path inside the atrium 44 by the combination of various movements of the tubes 18 and 20.
A. Catheter.
Housing 16 contains an energy emitting element 50 in the form of a transducer subassembly 64 at its proximal side such that there is a pocket 66 between the transducer subassembly 64 and the castle-head 58.
As shown in detail in
Still referring to
Tubing 18 also provides for a fluid flow path from the port 26 to the housing 16. The fluid is sterilized, and can be water, saline, or any other such physiologically compatible fluid. The fluid flows through the housing 16 as shown by fluid flow lines 60. The purpose of the flowing fluid is two-fold. First, it provides cooling for the transducer 68 while it is emitting the energy beam 52. Said fluid can be at any appropriate temperature so as to provide efficient cooling of the transducer 68. Secondly, the flowing fluid maintains a fluid pocket 66 which provides for a separation barrier between the transducer and the surrounding blood. This is important as the transducer may be at a higher temperature while emitting the beam 52, and any blood in contact with the transducer may form a thrombus which is not a desirable occurrence. In addition, any clot formation on the transducer would diminish the power output of the transducer. Thus a fluid column in front of the transducer avoids a clot formation, and keeps the transducer at a lower temperature to help it function efficiently.
The housing 16 can have a variety of configurations. One configuration is shown in
In another configuration, shown in
In another configuration (not illustrated), the fluid 60 in the housing 16 can be administered in a ‘closed-loop’ manner, where the flow of the fluid through the housing is for the purpose of providing cooling to the transducer contained therein. In this configuration, the housing 16 has the acoustically transparent window 98, but does not have the weep holes 96. Tube 18 will then have at least two lumens for the closed loop pathway of the cooling fluid. Alternatively, housing 16 can be filled by a gel-like material which is acoustically transparent, and in this case, the flowing fluid will not be needed.
In yet another configuration, shown in
Another configuration of the housing 16 is shown in
Yet another embodiment of the housing 16 is shown in
The XY tube 20 of
The details of the construction of tube 20 are shown in
Tube 20 can be manipulated in a controlled manner using a multiplicity of pull wires 120. The pull wires 120 can be metal such as steel or nitinol, or composite fibers such as Kevlar. These pull wires terminate at handle 24 in appropriate attachments which are then detachably engaged with the actuators and motors in the catheter pod 30. Motors (not shown) in the catheter pod 30 control the pull wires under the direction of the computer in the console 40 in a prescribed precise manner so as to move the tube 20 precisely in a desired locus. The result is that the energy beam 52 is traversed in the atrial chamber is a specific controlled path such as a line, circle, or any other more complex pattern.
Referring to
The energy emitting element 68 (
The transducer subassembly 64 (
One alternate embodiment of the transducer subassembly is shown in
Referring to
One embodiment of the sheath is shown in
Another embodiment of the sheath of this invention is shown in
The position of the catheter 10 during use in the atrial chamber is shown in
The details of the remaining components of the ablation system, namely, the handle, catheter pod, display pod, and the console, are described below.
B. Console. Referring to
Instrument 214 relies on FPGA 226 (Field Programmable Gate Array) for all time-critical system operations including coordinating all time-critical data transfer activities. In this way the instrument 214 can offer reliable real-time performance, while the operating system of the embedded PC 224 looks after all other routine, non-time-critical activities. The FPGA 226 is programmed with custom firmware to execute functions in response to instructions from the embedded PC 224. For example, the embedded PC will request that the FPGA generate transmit pulse sequences, which are directed through the D/A (digital to analog) converter 228, amplified and buffered by the ultrasound transceiver 230 and directed to the catheter 10, via cables 210 and 206.
Ultrasound transceiver 230 acts as transmitter and receiver of ultrasound signals. It operates on a time-multiplexed basis as either a power transmitter creating an ultrasound beam at the distal end of catheter 10, or as an ultrasound receiver sensing any ultrasound signals returning from the tissue. The ultrasound transceiver 230 can drive up to 25 watts electrical power, and more typically will provide between 2 to 10 watts, and even more preferably 2 to 7 watts, sufficient for typical catheter based applications. As a receiver, the transceiver 230 has sufficient dynamic range to detect returning ultrasound signals, typically over an 80 dB (decibel) dynamic range.
The ultrasound signal returning (backscattered) from the tissue is directed to two parallel receiver paths: linear FQ 232 and log detector 234. Linear FQ signals are derived by phase demodulating the received ultrasound signal to extract both the real and imaginary components (representing the amplitude and phase) of the signal, which are useful in a variety of processing algorithms used to extract signal information while maximizing signal-to-noise ratio. Alternatively, the signal from the log detector 234 provides a simple peak detection of the log-compressed returning ultrasound signal, which is commonly referred to as an “A-mode” signal in ultrasound imaging applications. The appropriate analog signal, FQ or log detected, is selected via multiplexor mux 236 for conversion by A/D (analog to digital) converter 238, and subsequent storage in digital form in memory 240. The ultrasound data stored in memory 240 may include additional information such as a time stamps, motor positions, transmit waveforms, etc. which can be used during the subsequent signal processing accomplished by algorithms running in the embedded PC 224. One such processing example is to determine the gap between the tip of catheter 10 and the atrial wall as the catheter is being moved around, and to present this information on display 216. Another process may be to determine the progress of the lesion depth during ablation. A third may be to determine tissue wall thickness and use this information to control the amount of energy delivered to the tissue. Additionally, the topographical map of the inside surface of the atrium can be presented in a three dimensional rendering at any point during the cardiac cycle.
In addition to controlling and coordinating the performance and processes in instrument 214, the embedded PC 224 controls a variety of input/output ports, I/O 242, to communicate to the keyboard 218, mouse 220, monitors 212 and 216 and for controlling and transferring data between itself, the display pod 204, the catheter pod 202 and the catheter 10.
C. Display Pod. The display pod 204, with internal components shown in
Also located in the display pod 204 is power regulator 252, which is used to compensate and correct for any potential voltage drops occurring through the lengthy cable 210, and to provide well regulated power to the servo motor components 254, 256, and 258 in the catheter pod 202 as shown in
D. Catheter Pod.
Multiplicity of servo motors 262 (motor 1, motor 2, motor 3 etc.) control the movement of the distal end of catheter 10 in the X-Y directions previously discussed, thereby bending the distal end of the catheter into a desired angle. In this implementation, the motors 262 tug on multiplicity of pull wires, which are located symmetrically in individual lumens of the catheter. In this way the distal end 12 of catheter 10 can be bent to the desired 1 and 0 angles (illustrated in
Since the positions of motor 262 and the bending angle Φ and θ of the distal end 12 of catheter 10 are not proportional to each other, a “warping” algorithm is used to compensate and reduce the distortion introduced by the non-linear bending. The details of this algorithm are stored in the console 208, and transferred via FPGA 254 to motor controller 256.
The additional motor 264 is coupled to tube 18 that moves the distal end of catheter 10 in and out, sometimes referred to as “the z axis.” In the 3-D space of the bending tip, this motor 264 controls to the radius r of the locus of the tip, while the other motors 262 and their corresponding pull wires control the Φ and θ positions.
Another feature incorporated in catheter pod 202 is quick release clutch 272. This electro-mechanical component responds to instructions from the console 208 or the emergency stop button 221, and immediately removes any tension from motors 260. This feature allows for easy and safe removal of the catheter 10 from the patient.
Another feature incorporated in the catheter pod is a thermocouple amplifier 274 that provides a cold-junction compensated thermocouple-to-digital converter reference that sends readings from thermocouples in the catheter 10 to the console 208. The temperature of critical components of the catheter 10 can be monitored and the system will react appropriately to out-of-range temperatures. For example, the system can post a warning if the transducer is rising beyond the range of optimal performance, and limit the power delivered to the transducer. Alternatively, a thermocouple located in the path of the saline drip adjacent to the transducer can monitor the adequacy of the drip rate.
Another feature included in the catheter pod 202 is the primary patient isolation 276, used to insure that the patient is protected from dangerous leakage currents under a variety of operating conditions, including fault conditions, consistent with regulatory requirements.
E. Handle.
Another electrical connection from the catheter pod 202 is for the ultrasound transmit/receive signal. This signal passes through signal conditioner 282, which can include noise suppression filters, impedance matching networks and balun (balanced-unbalanced) transformers, all used to maximize the transmit signal delivered to the transducer 64, and to maximize the signal-to-noise ratio of the returning receive signal from the transducer 64.
Encryption engine 284 provides a method of securing the data stored in memory 286. Memory 286 stores data specific to each catheter, and is read by the embedded PC 224 in the console 208. The data could include calibration information regarding transducer performance, mechanical characteristics needed for calibrating steering, manufacturing process and date, and use history unique to each catheter 10.
Thermocouple 86 senses the temperature of the transducer 68, while thermocouple 90 senses the temperature of the cooling fluid that flows past the transducer. Both connect via connections 294 and 296 to a thermocouple amplifier 288 that typically can convert the signal derived from the thermocouples to a digital value of temperature, in a format that can be sent via the router 278 back to the console 208. It is understood that any of a variety of sensors can be used in place of thermocouples, for example thermistors are a useful alternative for this application.
The mechanical connectors 280 couple the motors 260 in the catheter pod 202. If typical rotary motors are used, then rotary to linear converters 298 are used to derive the push-pull motion needed for the pull wires as well as the z axis movement. Alternatively, these rotary to linear converters 298 could be located in the catheter pod 202.
Finally, the tension and motion of the pull wires 300, which are connected to the coupler 118, can be sensed by load sensors 290 and position sensors 292. This information is fed back through the serial interface and router 278 to the motor controller 256 in the catheter pod 202. This feedback will improve the precision of the bending of the distal end, and can sense if the bending at distal end of the catheter is compromised by contact with the atrial wall.
Lesion Formation: The catheter disclosed herein is intended to create lesions of scarred tissue in the wall of the target tissue, often, the atrial wall, by impingement of energy on the wall tissue. The lesion is created when the ultrasound energy is directed towards the target point in the tissue and delivered there for sufficient time to heat the tissue to a temperature where the cells are killed. The energy emitted by the transducer is in the form of a beam, and this beam can be directed and moved around inside the atrial chamber is any desired path. The resulting lesion can thus be a spot, a line, a circle, or any other combination thereof.
Method of use: The desired method of treatment for the atrial fibrillation in the left atrium is to create lines of scar tissue in the atrial wall which would block the conduction of the unwanted signals. The present systems and methods describe the means of creating the scar tissue lines (lesions) in a controlled manner by manipulating an ultrasound beam. By way of example, one such desired lesion set, known as the Maze lesion set, is shown in
1. Place the transseptal sheath across the atrial septum. Advance the catheter through the sheath into the left atrium (LA) as previously shown in
2. Locate the ostia of the LPV by using the ‘raster’ technique. Additional details on this technique are disclosed in copending U.S. patent application Ser. Nos. 12/505,326; 12/695,857; 12/609,759; and Ser. No. 12/609,705; the entire contents of which have previously been incorporated herein by reference.
3. Define a desired contiguous and preferably substantially transmural lesion path 168 encircling the LPV. Optionally, the system may suggest a continuous and transmural lesion path to the user and the user may select the suggested pattern, modify the suggested pattern, or define an alternative continuous pattern.
4. Ablate the tissue along the defined lesion path 168 by moving the catheter as described previously.
5. Advance the catheter further into the LA to deploy the shepherd's hook thereby targeting the RPV as previously shown in
6. Locate the ostia of the RPV using the ‘raster’ technique as described in the previous location step.
7. Define the lesion path 170 encircling the RPV. Optionally, the system may also suggest a contiguous and preferably substantially transmural lesion path to the user and the user may select the suggested pattern, modify the suggested pattern, or define an alternative continuous pattern.
8. Ablate the tissue along the defined lesion path 170 by moving the catheter as described previously.
9. By using the various movements of the tip of the catheter, manipulate the direction of the energy beam to create the connecting lesions 172 and 174.
10. Using conventional mapping techniques, confirm the isolation of the pulmonary veins.
In optional embodiments, the system may automatically perform steps 1-10 above in a continuous fashion.
The above exemplary method describes ablation of tissue in the left atrium. One of skill in the art will of course appreciate that the ablation system described herein may also be used to ablate other tissues such as other regions of the heart (e.g. right atrium, ventricles, adjacent vessels) as well as non-cardiac tissue.
While the above is a complete description of the preferred embodiments of the invention, various alternatives, modifications, and equivalents may be used. Therefore, the above description should not be taken as limiting in scope of the invention which is defined by the appended claims.
The present application is a continuation of U.S. patent application Ser. No. 13/630,750, filed Sep. 28, 2012, which is a continuation of U.S. patent application Ser. No. 12/909,642, filed Oct. 21, 2010, which claims the benefit of U.S. Provisional App. No. 61/254,997, filed Oct. 26, 2009, the entire contents of each are incorporated herein by reference. The present application is related to U.S. patent application Ser. Nos. 11/747,862; 11/747,867; 12/480,929; 12/480,256; 12/483,174; 12/482,640; 12/505,326; 12/505,335; 12/620,287; 12/695,857; 12/609,759; 12/609,274; and Ser. No. 12/609,705, the entire contents of which are incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61254997 | Oct 2009 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 13630750 | Sep 2012 | US |
| Child | 16265265 | US | |
| Parent | 12909642 | Oct 2010 | US |
| Child | 13630750 | US |
