Basket catheter with insulated ablation electrodes

Abstract

To provide a catheter.SOLUTION: A catheter includes a shaft for insertion into an organ of a patient, and an expandable distal-end assembly, which is coupled to the shaft and to an apex of the catheter and includes multiple splines. In at least given one of the multiple splines, at least 60 percent of the length of the given spline is uninsulated and is configured to contact tissue of the organ and to apply radiofrequency (RF) pulses to the tissue.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application is related to even-dated U.S. patent application having attorney docket number BIO6389USNP1 / 1002-2268, entitled "Basket Catheter having insulated ablation electrodes and diagnostic electrodes," the disclosure of which is incorporated herein by reference.

[0002] FIELD OF THEINVENTION The present invention relates generally to medical catheters, and more particularly to ablation catheters having expandable distal ends. [Background technology]

[0003] Basket catheters can be used in a variety of medical applications, such as cardiology. Several types of basket catheters with multiple splines are designed to allow for the sensing and treatment of arrhythmias.

[0004] For example, U.S. Patent Application Publication No. 2014 / 0238175 describes methods, systems, and devices for providing treatment to a target site. The system may include a guide assembly, an expandable support device coupled to a distal end of the guide assembly, and a motion member disposed on the expandable support device. The expandable support device may be configured to transition between a collapsed configuration and an expanded configuration.

[0005] No. 6,292,695 describes a method of controlling cardiac fibrillation, tachycardia, or arrhythmias by use of an electrophysiology catheter having a distal portion housing at least one stimulating electrode, the electrode being stably placed at a selected intravascular location. The electrode is connected to a stimulating means, and stimuli are applied transvascularly across the wall of the blood vessel to the sympathetic or parasympathetic nerves innervating the heart with sufficient intensity to depolarize the nerves and achieve control of the heart.

[0006] US Patent No. 6,421,556 describes systems and methods for diagnosing and treating tissue that deliver electrical energy pulses that temporarily render tissue in an area incapacitated and temporarily electrically unresponsive. These systems and methods detect an electrophysiological effect of the delivered pulse. These systems and methods alter electrophysiological properties of tissue in or near the area based at least in part on the detected electrophysiological effect. The change in electrophysiological properties may be achieved, for example, by tissue ablation or by administration of a drug. In one embodiment, radio frequency energy is used to both temporarily render tissue incapacitated and to ablate the tissue with a common electrode.

[0007] U.S. Patent Application Publication No. 2015 / 0182282 describes various systems and techniques for generating and applying plasma and / or electric fields, alone or in combination with other therapies, to living tissue to treat different tissue conditions, as well as other conditions such as tumors, bacterial infections, etc., while limiting the generation of electrical currents within the tissue.

[0008] US Patent Application Publication No. 2006 / 0100669 shows and describes a system for atrial fibrillation using a basket catheter. Summary of the Invention [Means for solving the problem]

[0009] One embodiment of the present invention described herein provides a catheter including a shaft for insertion into an organ of a patient, and an expandable distal tip assembly coupled to the shaft and a top of the catheter, the distal tip assembly including a plurality of splines, at least a given spline of the plurality of splines being uninsulated over at least 60 percent of the length of the given spline and configured to contact tissue of the organ and apply radio frequency (RF) pulses to the tissue.

[0010] In some embodiments, up to 40 percent of the length of a given spline is insulated and is located between the uninsulated length and the apex. In other embodiments, the insulated length is coated with an electrically insulating layer. In yet other embodiments, at least a given spline comprises a nickel-titanium alloy.

[0011] In one embodiment, the apex has a flat surface perpendicular to the axis of the shaft. In another embodiment, the flat surface is insulated. In yet another embodiment, the catheter includes a bump stop coupled to the apex and configured to limit the minimum distance between the shaft and the apex.

[0012] According to an embodiment of the present invention, there is further provided a method for manufacturing a catheter, the method including receiving the plurality of splines such that at least a given spline of the plurality of splines is uninsulated over at least 60 percent of a length of the given spline and configured to contact tissue of a patient's organ and apply radio frequency (RF) pulses to the tissue, the plurality of splines being assembled together to produce an expandable distal tip assembly, the expandable distal tip assembly being coupled to the shaft and the top of the catheter.

[0013] The invention will be more fully understood from consideration of the following detailed description taken in conjunction with the drawings, in which: [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic, pictorial illustration of a catheter-based position tracking and ablation system, in accordance with an embodiment of the present invention; [Diagram 2] FIG. 2 is a schematic, pictorial view of a distal end assembly in an extended position, in accordance with an embodiment of the present invention. [Diagram 3] FIG. 2 is a schematic, pictorial view of a distal end assembly in an extended position, in accordance with an embodiment of the present invention. [Figure 4]FIG. 1 is a flow diagram that generally illustrates a method for manufacturing a basket catheter having insulated ablation electrodes, in accordance with an embodiment of the present invention. [Diagram 5] 4 is a flow diagram that generally illustrates a method for ablating tissue using the distal end assembly of FIG. 3, in accordance with an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Overview The embodiments of the invention described below provide several configurations of an improved distal tip assembly for use in a catheter of an ablation system. In some embodiments, the catheter comprises a shaft for inserting the distal tip assembly into a patient's heart, and an expandable distal tip assembly, such as a basket, coupled to the shaft and to the top of the catheter.

[0016] In some embodiments, the distal end assembly comprises a plurality of splines, at least one of which, typically all of the splines, is made of solid nitinol and has at least two portions. A first portion of the spline is uninsulated, conductive, and comprises at least 60 percent of the length of the spline. The first portion is configured to contact cardiac tissue and apply radio frequency (RF) pulses to the tissue.

[0017] In some embodiments, a second portion of the spline is insulated, comprises up to 40 percent of the length of the spline, and is positioned between the non-insulated portion and the top of the catheter. The insulated portion may comprise the nitinol of the spline coated with an electrically insulating layer.

[0018] In some embodiments, the apex is electrically isolated from the splines and has a flat surface perpendicular to the axis (e.g., longitudinal axis) of the shaft. Note that in the above configuration, the first portion is conductive and configured to ablate cardiac tissue, and the second portion and the apex are electrically isolated and configured to provide electrical isolation between non-insulated portions of the splines. In such an embodiment, in an ablation catheter having a first spline and a second spline, each having a first portion and a second portion, a processor of the ablation system is configured to control a radio frequency (RF) pulse generator to apply one or more RF pulses to the first spline without applying RF pulses to the second spline.

[0019] Typically, prior to performing an ablation procedure, mapping of intracardiac signals is performed, for example, to define the target tissue for ablation. In some embodiments, it is possible to use the non-insulated portion of the spline to sense the intracardiac signal. However, the non-insulated portion, which includes at least 60 percent of the spline, may be in contact with a long portion of the cardiac tissue and therefore may not be able to sense the intracardiac signal with a sufficiently high lateral resolution (e.g., about 1.0 mm) to map the tissue prior to ablation.

[0020] In some embodiments, the basket-shaped distal end assembly may include one or more diagnostic electrodes, also referred to herein as sensing electrodes, which in this example are coupled to the electrically isolated portion and / or the tip.

[0021] In some embodiments, one or more of the sensing electrodes are configured to sense a unipolar signal, for example, between the sensing electrode and a reference electrode attached to the skin or any other tissue of the patient.

[0022] In other embodiments, two or more of the sensing electrodes are disposed on the apex and the insulating portion and are configured to sense bipolar signals. For example, the first and second sensing electrodes may be disposed on the insulating portion of the first spline, the third sensing electrode may be disposed on the insulating portion of the second spline, and the fourth sensing electrode may be disposed on the apex. In this configuration, the processor of the ablation system is configured to receive multiple bipolar signals from any pair of the four sensing electrodes. For example, (i) a first bipolar signal between the first electrode and the second electrode, (ii) a second bipolar signal between the second electrode and the third electrode, and (iii) a third bipolar signal between the third sensing electrode and the fourth sensing electrode.

[0023] The disclosed techniques are particularly effective when ablating (i) long, narrow tissues (e.g., when one or more RF pulses are applied to a single spline) or (ii) long, wide tissues (e.g., when RF pulses are applied to multiple splines). Thus, the disclosed techniques may reduce the overall cycle time of an ablation procedure.

[0024] Furthermore, the disclosed techniques reduce the need to attach dedicated ablation electrodes to the expandable catheter, thus improving the mechanical flexibility of the splines and reducing the costs associated with manufacturing the expandable distal end assemblies of the ablation catheter.

[0025] System Description 1 is a schematic, pictorial illustration of a catheter-based position tracking and ablation system 20, in accordance with an embodiment of the present invention. In some embodiments, system 20 comprises a catheter 22, in this example a cardiac catheter, and a control console 24. In the embodiments described herein, catheter 22 may be used for any suitable therapeutic and / or diagnostic purposes, such as ablation of tissue within a heart 26, and for mapping arrhythmias by sensing intracardiac electrical signals.

[0026] In some embodiments, the console 24 comprises a processor 42, typically a general purpose computer, having a front end and interface circuitry suitable for receiving signals from the catheter 22 and controlling other components of the system 20 described herein. The processor 42 may be programmed in software to perform the functions used by the system, and the processor is configured to store data for the software in memory 50. This software may be downloaded to the console 24 in electronic form, for example over a network, or may be provided on a non-transitory tangible medium, such as an optical, magnetic, or electronic storage medium. Alternatively, some or all of the functions of the processor 42 may be performed using an application specific integrated circuit (ASIC) or any suitable type of programmable digital hardware component.

[0027] Reference is now made to inset 25. In some embodiments, catheter 22 comprises a distal tip assembly 40 having multiple splines (shown in detail in Figures 2 and 3 below) and a shaft 23 for inserting distal tip assembly 40 to a target location for ablation of tissue within heart 26. During an ablation procedure, physician 30 inserts catheter 22 through the vascular system of patient 28 lying on table 29. Physician 30 moves distal tip assembly 40 to the target location within heart 26 using a manipulator 32 near the proximal end of catheter 22, which is connected to interface circuitry of a processor 42.

[0028] In some embodiments, the catheter 22 comprises a position sensor 39 of a position tracking system, e.g., coupled to the distal end of the catheter 22 proximate the distal tip assembly 40. In this example, the position sensor 39 comprises a magnetic position sensor, although in other embodiments, any other suitable type of position sensor (e.g., other than magnetic-based) may be used.

[0029] Referring again to the schematic diagram of Figure 1, in some embodiments, during navigation of the distal tip assembly 40 within the heart 26, the processor 42 receives signals from a magnetic position sensor 39 in response to a magnetic field from an external magnetic field generator 36, for example, to determine the position of the distal tip assembly 40 within the heart 26. In some embodiments, the console 24 includes a drive circuit 34 configured to drive the magnetic field generator 36. The magnetic field generator 36 is positioned at a known position external to the patient 28, such as, for example, beneath the table 29.

[0030] In some embodiments, the processor 42 is configured to display, for example on a display 46 of the console 24 , the tracked position of the distal tip assembly 40 superimposed on an image 44 of the heart 26 .

[0031] This method of position sensing using an external magnetic field has been implemented in a variety of medical applications, for example in the CARTO™ system manufactured by Biosense Webster Inc. (Irvine, Calif.), and is described in detail in U.S. Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612, and 6,332,089, WO 96 / 05768, and U.S. Patent Application Publication Nos. 2002 / 0065455(A1), 2003 / 0120150(A1), and 2004 / 0068178(A1), the disclosures of which are all incorporated herein by reference.

[0032] Distal tip assembly having an insulated ablation electrode FIG. 2 is a schematic, pictorial illustration of distal end assembly 40 in an extended position, according to one embodiment of the present invention.

[0033] In some embodiments, the distal tip assembly 40 comprises a plurality of splines 55 made of a solid nickel-titanium alloy, such as solid Nitinol, or any other suitable alloy or material. It is noted that Nitinol is selected for the splines 55 because it is electrically conductive and sufficiently flexible to conform to the tissue intended to be ablated. Thus, any other material selected for the splines 55 must be electrically conductive and sufficiently flexible to conform to said tissue.

[0034] In some embodiments, at least a given spline 55, typically each spline 55 of the distal end assembly 40, has a conductive portion, referred to herein as portion 66, that is configured to function as an ablation electrode for ablation of tissue at a target location within the heart 26.

[0035] In some embodiments, portion 66 comprises at least 60 percent of the length of spline 55. Portion 66 is not insulated (e.g., is conductive as described above) and is configured to contact tissue of heart 26 and to apply radio frequency (RF) pulses to the cardiac tissue during an ablation procedure.

[0036] In other embodiments, portion 66 may include any other suitable portion of the length of spline 55 .

[0037] In some embodiments, at least a given spline 55 as discussed above, and typically each spline 55 of the distal end assembly 40, has a portion 77 that is up to 40 percent of the length of the respective (e.g., given) spline 55. Portion 77 is insulated and is positioned between portion 66 and a top 88 of catheter 22.

[0038] In some embodiments, portion 77 is configured to provide electrical insulation between portions 66 of splines 55, at least at apex 88, which is typically electrically insulated from the splines. In other embodiments, apex 88 may include a conductive material and function as an additional ablation electrode for distal tip assembly 40.

[0039] In some embodiments, the top 88 has a flat surface 89 that is typically (but not necessarily) perpendicular to the axis of the shaft 23 .

[0040] It should be noted that portion 66 has a typical length of about 10 mm to 40 mm. Thus, when the plurality of splines 55 is applying a pulse having a predetermined energy and duration, the distal tip assembly 40 penetrates approximately 256 mm into tissue at the target location of the heart 26. 2 The ablation area is configured to:

[0041] In the context of this disclosure and in the claims, the term "about" or "approximately" used in conjunction with any numerical value or range of values ​​is intended to indicate a reasonable tolerance of dimensions that enables a portion of a component or a collection of components to function in accordance with its intended purpose as described herein. More specifically, "about" or "approximately" may refer to a range of values ​​of ±20% of the recited value, e.g., "about 90%" may refer to a range of values ​​of 71% to 99%.

[0042] In some embodiments, the distal end assembly 40 includes a coupling element (in this example, a ring 54) that is coupled to a proximal end of a spline 55 and configured to threadably engage the shaft 23 to provide a coupling between the shaft 23 and the distal end assembly 40. Note that each spline 55 is electrically connected to the catheter 22, for example, via a wire (not shown) extending from the proximal end of each spline 55. Thus, the processor 42 may control the electrical connection between the console 24 and each portion 66 of the spline 55. This controlled and selective connectivity is important for applying RF pulses to the tissue of the heart 26 via a selected spline 55, as well as for receiving intracardiac electrical signals from a selected electrode (e.g., portion 66 or other electrode described in FIG. 3 below) that is placed in contact with the tissue of the heart 26.

[0043] In some embodiments, the distal tip assembly 40 is in a collapsed position and all of the splines 55 are straight when the physician 30 moves the distal end of the catheter 22 to a target location within the heart 26. Once the distal tip assembly 40 is positioned at a target location within the heart 26, the physician 30 typically reduces the distance between the ring 54 and the apices 88 (e.g., by pulling the apices 88 towards the ring 54, or by pushing the ring 54 towards the apices 88, or using any other technique) to place the distal tip assembly 40 in an expanded position in which the splines 55 are bent, as shown in FIG.

[0044] In some embodiments, the distal end assembly 40 includes a bump stop 91 coupled to the apex 88 and configured to control the minimum distance between the shaft 23 and the apex 88. That is, the bump stop 91 is fixed at a proximal position of the apex 88 such that the bump stop 91 faces the distal end of the shaft 23. In the extended position shown in the example of FIG. 2, the distal end assembly 40 may have a gap distance 92 (measured along the longitudinal axis 70) between the distal end of the shaft 23 and the bump stop 91. The gap distance 92 can be anywhere from about 1 mm to 13 mm, depending on the overall diameter of the catheter. In one preferred embodiment, the distance of the gap 92 is about 3 mm as measured along the longitudinal axis 70. In such an embodiment, as the physician 30 further reduces the distance between the ring 54 and the apex 88, the bump stop 91 is configured to contact the tip of the shaft 23 such that the gap distance 92 is non-existent (i.e., equal to zero), thereby limiting the minimum distance between the shaft 23 and the apex 88. In other words, the bump stop 91 is configured to act as a hard stop and prevent the basket distal assembly 40 from becoming completely flat, thereby preventing the Nitinol base from buckling.

[0045] In some embodiments, the physician 30 may use the manipulator 32 to control the distance between the apex 88 and the ring 54, and therefore the amount of expansion of the distal tip assembly 40. It should be noted that when an RF pulse is applied to the distal tip assembly 40, the portion 66 acts as an ablation electrode and applies an RF pulse to the tissue it contacts, whereas the portion 77 is insulated and therefore does not apply an RF pulse to the tissue. Furthermore, the portion 77 provides electrical isolation between the portions 66 of the distal tip assembly 40. In this configuration, the processor 42 may control the RF pulse generator to apply one or more RF pulses to the first portion 66 of the first spline 55 and no RF pulses to the second portion 66 of the second spline 55.

[0046] A diagnostic electrode coupled to the top of the distal tip assembly. 3 is a schematic, pictorial illustration of a distal end assembly 80 in an extended position, according to another embodiment of the present invention. The distal end assembly 80 may, for example, be substituted for the distal end assembly 40 of FIG.

[0047] In some embodiments, distal end assembly 80 includes a plurality of splines 56, such as splines 56A, 56D, 56E, and 56F, similar to spline 55 of Figure 2 above, each having an insulated portion 77A, 77D, 77E, and 77F, respectively. Each spline 56 of distal end assembly 80 includes a non-insulated portion 66 having the dimensions, mechanical attributes, and electrical attributes described in Figure 2 above.

[0048] In some embodiments, distal tip assembly 80 includes one or more diagnostic electrodes, referred to herein as electrodes 99. In this example, electrodes 99 include (i) electrodes 99A and 99B coupled to portion 77A, (ii) electrode 99C coupled to surface 89 of apex 88, (iii) electrode 99D coupled to portion 77D, (iv) electrode 99E coupled to portion 77E, and (v) electrode 99F coupled to portion 77F. In other embodiments, distal tip assembly 80 may include other suitable numbers of electrodes 99 disposed on any portion 77 and / or apex 88 using any suitable configuration.

[0049] In some embodiments, the electrodes 99 are configured to sense electrical signals within the tissue when placed in contact with the tissue of the heart 26. In the context of this disclosure and claims, the terms "sensing," "mapping," and "diagnosis" are used interchangeably, and sensing electrodes (e.g., electrodes 99) configured to sense intracardiac signals generate signals that are used to map and diagnose the problematic tissue of the heart 26. In such embodiments, the processor 42 is configured to generate an electrophysiological map of the problematic tissue of the heart 26 based on the intracardiac signals received from the electrodes 99.

[0050] In some embodiments, electrodes 99A and 99B are attached to portion 77A of spline 56A and configured to sense a bipolar signal therebetween.

[0051] In some embodiments, bipolar signals may be sensed between electrodes 99E and 99F coupled to portions 77E and 77F of splines 56E and 56F, respectively. Additionally or alternatively, bipolar signals may be sensed between electrode 99C coupled to surface 89 and electrode 99D coupled to portion 77D of spline 56D. In other words, bipolar signals may be sensed (i) between a pair of electrodes disposed on a single spline, and / or (ii) between a pair of electrodes disposed on two different splines, and / or (iii) between an electrode coupled to apex 88 and an electrode coupled to a spline, and / or (iv) between a pair of electrodes (not shown) coupled to apex 88 and at a predetermined distance from each other, as shown, for example, in portion 77A of spline 56A.

[0052] In other embodiments, at least one of the electrodes 99 is configured to sense a unipolar signal relative to a reference electrode (not shown), for example, placed in contact with tissue within the body of the patient 28 or attached to the skin of the patient 28 (not shown).

[0053] In some embodiments, electrodes 99 are coupled to respective portions 77 using any suitable technique, such as by crimping.

[0054] In some embodiments, the distal tip assembly 80 may include electrical wires and / or electrical traces (not shown) configured to provide an electrical connection between each electrode 99 and the processor 42. The electrical wires may be organized in a braid that extends between the console 24 and the shaft 23, at the distal end of the shaft 23, with each electrical wire leading to a respective electrode 99.

[0055] In some embodiments, when distal tip assembly 80 is placed in contact with tissue of heart 26, one or more of electrodes 99 are configured to generate an electrical potential gradient signal in response to an electrical potential sensed in the tissue of heart 26. A position sensor 39, which is fixed to the distal end of catheter 22 a known distance from each electrode 99, is configured to generate a position signal in response to a sensed external magnetic field.

[0056] In some embodiments, based on (i) the position signal received from the position sensor 39 and (ii) the signals received from one or more electrodes 99, the processor 42 is configured to display, for example on the display 46, an electrophysiological map of the electrical potentials detected by the electrodes 99 at each location within the tissue of the heart 26.

[0057] In some embodiments, based on electrophysiological mapping of tissue of heart 26, physician 30 may position selected spline 56 in contact with tissue within heart 26 where ablation is to occur. Physician 30 and / or processor 42 may then control system 20 to apply RF pulses to ablate tissue of heart 26.

[0058] This particular configuration of system 20 and distal end assemblies 40 and 80 is provided by way of example to explain the particular problems addressed by embodiments of the present invention and to demonstrate the application of these embodiments in improving the performance of such ablation systems, however, embodiments of the present invention are not limited to this particular type of exemplary system, and the principles described herein may be applied to other types of medical systems as well, including, but not limited to, electrosurgical systems and irreversible electroporation (IRE) ablation systems.

[0059] Fabrication of basket-shaped distal end assembly 4 is a flow diagram that generally illustrates a method for manufacturing distal tip assemblies 40 and 820, according to an embodiment of the present invention. The method begins with a spline receiving step 100, which receives a plurality of splines 55 made of Nitinol or any suitable nickel-titanium alloy, or any other alloy suitable for functioning as ablation electrodes, as described above in FIGS. 2A and 2B.

[0060] In a coating step 102, portions 77 of at least one of the splines 55, and typically all of the splines 55, are coated with an electrically insulating layer. In a distal tip assembly fabrication step 104, the distal tip assemblies 40 and 80 are fabricated by (i) connecting the proximal ends of all of the splines 55 to the ring 54, and (ii) connecting the distal ends 77 of all of the splines 55 to the catheter tip 88.

[0061] In other embodiments, one or more of the splines 55 may already be coated with the aforementioned electrically insulating layer in the spline-receiving step 100, and therefore step 102 may be redundant and therefore may be omitted from the method.

[0062] 2B above, one or more electrodes 99 are coupled to the tips 88 and / or portions 77 of one or more splines 55 and connected to electrical wires for conducting signals between one or more (typically all) of the electrodes 99 and the processor 42. Note that step 106 is not performed in the manufacture of the distal tip assembly 40.

[0063] The method concludes with a distal end assembly coupling step 108, in which either the distal end assembly 40 or the distal end assembly 80 is coupled to the shaft 23 along the axis 70, as described above in Figures 2A and 2B. Note that in the manufacture of the distal end assembly 40 after performing step 104, the method proceeds directly to step 108 without performing step 106, which is only performed in the manufacture of the distal end assembly 80.

[0064] In summary, steps 100 , 102 , 104 , and 108 are used in the manufacture of distal tip assembly 40 , and all steps 100 , 102 , 104 , 106 , and 108 are used in the manufacture of distal tip assembly 80 .

[0065] 4 for manufacturing distal tip assemblies 40 and 80 is shown by way of example to explain the particular problems addressed by embodiments of the present invention and to demonstrate the application of these embodiments in manufacturing distal tip assemblies 40 and 80 to improve the performance of system 20. However, embodiments of the present invention are not limited to this particular type of exemplary manufacturing process, and the principles described herein may be similarly applied to other types of distal tip assemblies used in system 20, or other types of medical systems, including, but not limited to, electrosurgical systems and irreversible electroporation (IRE) ablation systems.

[0066] Performing an Ablation Procedure Using a Basket-Shaped Distal End Assembly 5 is a flow diagram that generally illustrates a method for ablating tissue using distal end assembly 80, in accordance with one embodiment of the present invention. The method begins with a catheter insertion step 200 of inserting distal end assembly 80 into heart 26, which is described in more detail in FIG. 3 below. Essentially, one or more splines 56 of distal end assembly 80 have (i) a portion 66 configured for ablation of tissue of heart 26, and (ii) one or more electrodes, such as electrodes 99A-99F shown in FIG. 3 above, configured for sensing intracardiac electrical signals in tissue of heart 26.

[0067] In the sensing step 202, the physician 30 controls the expansion of the distal end assembly 80 to an expanded position after positioning the distal end assembly 80 adjacent tissue at a target location within the heart 26. The expansion may be performed, for example, by decreasing the distance between the ring 54 and the apex 88. Note that the minimum distance between the ring 54 and the apex 88 is limited by the bump stop 91, as described in FIG. 1 above. In some embodiments, in the sensing step 202, at least one, and typically both, of the apex 88 and the portion 77 (e.g., portions 77A, 77D, 77E, and 77F) are coupled to tissue to sense intracardiac electrical signals.

[0068] Ablation Based on Signals Detected in Step 202 In step 204, the physician 30 manipulates the distal end assembly 80 to couple the portions 66 of one or more splines 56 (e.g., splines 56A, 56D, 56E, and 56F) to the tissue to perform RF ablation. In step 202, the distal end assembly 80 is positioned such that the axis 70 is approximately perpendicular to the tissue to place the surface 89 of the apex 88 in contact with the tissue for sensing. Further, in step 204, the distal end assembly 80 is positioned such that the axis 70 is approximately parallel to the tissue, thus placing one or more portions 66 in contact with the tissue to perform ablation of the tissue.

[0069] In catheter extraction step 206, which concludes the method, after ablation is completed, the physician 30 controls the catheter 22 to collapse the distal end assembly 80 (e.g., by increasing the distance between the ring 54 and the apex 88) and then withdraws the catheter 22 from the body of the patient 28.

[0070] In other embodiments, processor 42 may maintain an electrophysiological mapping of the tissue prior to the ablation procedure, i.e., at least prior to step 202. In such embodiments, ablation step 204 may be performed based on the mapping after catheter insertion step 200, and sensing step 202 may be performed after step 204 to ascertain whether application of additional RF pulses is required after step 204 to complete the ablation procedure. If application of additional RF pulses is required, the method returns to ablation step 204 and then to sensing step 202 for one or more iterations until ablation is complete.

[0071] In an alternative embodiment, the sensing step 202 may be performed before or after the ablation step 204 to sense intracardiac electrical signals for controlling the ablation process as described above.

[0072] Although the embodiments described herein primarily deal with basket catheters, the techniques described herein can also be used with any other suitable medical probe having splines for applying energy to tissue.

[0073] It will be understood that the above described embodiments are given by way of example, and the present invention is not limited to what is specifically shown and described herein above. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described in the above specification, as well as variations and modifications thereof not disclosed in the prior art that would occur to a person skilled in the art upon reading the foregoing description. Documents incorporated by reference into this patent application shall be considered as an integral part of this application, except that if any term is defined in these incorporated documents in a manner that contradicts the definition expressly or impliedly made herein, then only the definition in this specification shall be considered.

[0074] [Embodiment] (1) A catheter comprising: a shaft for insertion into an organ of a patient, the shaft extending along a longitudinal axis; an expandable distal tip assembly coupled to the shaft and the top of the catheter, the expandable distal tip assembly comprising a plurality of splines, at least a given spline of the plurality of splines being uninsulated for at least 60 percent of a length of the given spline, the expandable distal tip assembly being configured to contact tissue of the organ and apply radio frequency (RF) pulses to the tissue; a bump stop coupled to the apex and configured to limit a minimum distance between the shaft and the apex along the longitudinal axis, the bump stop separated from a tip of the shaft by an axial gap between the tip and the bump stop. (2) A catheter as described in embodiment 1, wherein up to 40 percent of the length of the given spline is insulated and is positioned between the uninsulated length and the apex. (3) The catheter of embodiment 2, wherein the insulating length is coated with an electrically insulating layer. (4) A catheter as described in embodiment 1, wherein at least the given spline comprises a nickel-titanium alloy. (5) A catheter as described in embodiment 1, wherein the apex has a flat surface perpendicular to the axis of the shaft.

[0075] (6) The catheter of embodiment 5, wherein the flat surface is insulated. (7) The catheter of claim 1, wherein the axial gap comprises a gap distance selected from any value between about 1 mm and about 13 mm. (8) A method for manufacturing a catheter, comprising the steps of: receiving a plurality of splines, at least a given spline of the plurality of splines having at least 60 percent of a length of the given spline uninsulated and configured to contact tissue of a patient's organ and apply radio frequency (RF) pulses to the tissue; assembling the plurality of splines together to produce an expandable distal tip assembly; connecting the expandable distal end assembly to a shaft and to a tip of the catheter, wherein a bump stop is disposed between the shaft and the tip to ensure a gap between the shaft and the tip. (9) The method of embodiment 8, wherein up to 40 percent of the length of the given spline is insulated, and coupling the expandable distal end assembly includes coupling the insulated length to the apex. 10. The method of claim 9, further comprising coating the length of insulation with an electrically insulating layer.

[0076] 11. The method of claim 8, wherein at least the given spline comprises a nickel-titanium alloy. (12) The method of claim 9, wherein connecting the expandable distal end assembly to the apex includes connecting an insulating portion of the spline to a flat surface of the apex perpendicular to the axis of the shaft. 13. The method of claim 12, wherein the flat surface is insulating. (14) The method of embodiment 8, wherein coupling the expandable distal end assembly includes coupling a bump stop to the apex to limit a minimum distance between the shaft and the apex.

Claims

1. A catheter comprising: a shaft for insertion into an organ of a patient, the shaft extending along a longitudinal axis; an expandable distal tip assembly coupled to the shaft and the top of the catheter, the expandable distal tip assembly comprising a plurality of splines, at least a given spline of the plurality of splines having at least 60 percent of a length of the given spline uninsulated, the expandable distal tip assembly configured to contact tissue of the organ and apply radio frequency (RF) pulses to the tissue; a bump stop coupled to the apex and configured to limit a minimum distance between the shaft and the apex along the longitudinal axis, the bump stop separated from a tip of the shaft by an axial gap between the tip and the bump stop.

2. The catheter of claim 1 , wherein up to 40 percent of the length of the given spline is insulated and is located between the uninsulated length and the apex.

3. The catheter of claim 2 , wherein the length of insulation is coated with an electrically insulating layer.

4. The catheter of claim 1 , wherein at least the given spline comprises a nickel-titanium alloy.

5. The catheter of claim 1 , wherein the apex has a flat surface perpendicular to the axis of the shaft.

6. The catheter of claim 5 , wherein the flat surface is insulated.

7. The catheter of claim 1 , wherein the axial gap comprises a gap distance selected from any value between about 1 mm and about 13 mm.

8. 1. A method of manufacturing a catheter, comprising: receiving a plurality of splines, at least a given spline of the plurality of splines having at least 60 percent of a length of the given spline uninsulated and configured to contact tissue of a patient's organ and apply radio frequency (RF) pulses to the tissue; assembling the plurality of splines together to produce an expandable distal tip assembly; and connecting the expandable distal end assembly to a shaft and a tip of the catheter, wherein a bump stop is disposed between the shaft and the tip to ensure a gap between the shaft and the tip.

9. 9. The method of claim 8, wherein up to 40 percent of the length of the given spline is insulated, and coupling the expandable distal end assembly includes coupling the insulated length to the apex.

10. The method of claim 9 including coating the length of insulation with an electrically insulating layer.

11. The method of claim 8, wherein at least the given spline comprises a nickel-titanium alloy.

12. 10. The method of claim 9, wherein coupling the expandable distal end assembly to the apex comprises coupling an insulating portion of the spline to a flat surface of the apex perpendicular to the axis of the shaft.

13. The method of claim 12 , wherein the flat surface is insulating.

14. 10. The method of claim 8, wherein coupling the expandable distal end assembly includes coupling a bump stop to the apex to limit a minimum distance between the shaft and the apex.

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