Patent Publication Number: US-2021186603-A1

Title: Lasso Catheter with Balloon

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to invasive catheters, and specifically to an invasive medical catheter comprising a lasso-shaped distal and a balloon that can be inflated to increase the diameter of the lasso-shaped distal end. 
     BACKGROUND OF THE INVENTION 
     Ablation of myocardial tissue is well known as a treatment for cardiac arrhythmias. In radio-frequency (RF) ablation, for example, a catheter is inserted into the heart and brought into contact with tissue at a target location. RF energy is then applied through an electrode on the catheter in order to create a lesion for the purpose of breaking arrhythmogenic current paths in the tissue. In some ablation procedures used to treat atrial arrhythmias (particularly for atrial fibrillation), a lasso catheter can be used to perform circumferential ablation of the ostia of the pulmonary veins. 
     U.S. Pat. No. 9,265,575 to Coe et al., describes a balloon catheter neuromodulation system. The balloon catheter includes a bipolar electrode pair, wherein at least one of the bipolar electrode pair is configured to be positioned to be expanded into contact with an inner wall of the hepatic artery branch upon expansion of the at least one expandable balloon. 
     U.S. Patent Application 2016/0235477 to Shutaro describes a balloon catheter ablation system. The system includes a highly directional pressure sensor that is provided coaxially in an anterior portion of a catheter shaft within a balloon. This enables monitoring a pressing force against the balloon onto the tissue, a temperature of the balloon, impedances, potentials, and an energization time. Additionally, providing the directional pressure sensor inside the balloon enables a pressing force from the balloon onto the tissue to be monitored with accuracy without being influenced by the swirl&#39;s liquid, thereby securing effective ablation of the target tissues. 
     U.S. Patent Application 2015/0141982 to Lee describes a multi-electrode balloon catheter with circumferential and point electrodes. The balloon catheter includes outer and inner balloon member, which can be elastic or inelastic. This allows the members to inflate and expand outwardly under an internal force and to deflate and collapse when the force is absent or removed. The internal force is provided by introduction of an inflation medium into a cavity of the inner balloon member. 
     U.S. Pat. No. 5,984,917 to Fleischman et al., describes a device and method for remote insertion of a closed loop of a lasso-shaped catheter. The device includes a catheter mechanism used to expand a metallic mesh during insertion over an inverted appendage. 
     U.S. Pat. No. 5,984,917 to Grunewald describes a catheter with multiple electrode assemblies for use at or near tubular regions of the heart. The catheter includes a distal electrode assembly and a proximal electrode assembly. The distal electrode assembly has an elongated member defining a longitudinal axis and a plurality of spines surrounding the member and converging at their proximal and distal ends, where each spine has at least one electrode and a curvature so that the spine bows radially outwardly from the member. The proximal electrode assembly has a proximal electrode assembly has an elongated member configured with a generally radial portion and a generally circular portion generally transverse to the catheter axis, where the generally circular portion comprising a plurality of electrodes. 
     U.S. Pat. No. 5,984,917 to Fleischman et al., describes a device and method for remote insertion of a lasso portion (i.e., assembly) of a catheter. The catheter includes a flexible catheter body having a distal tip portion. A lumen or tubular guide is provided for allowing the lasso to be freely axially movable so that the lasso can be expanded or contracted. 
     U.S. Pat. No. 5,984,917 to Ditter et al., describes a catheter with a variable arcuate distal section. The catheter includes a mandrel contained within a hollow support member, the distal end has a generally circular form, and an operator can expand or even significantly straighten the form of the distal assembly by advancing the mandrel through the hollow support member. 
     The description above is presented as a general overview of related art in this field and should not be construed as an admission that any of the information it contains constitutes prior art against the present patent application. 
     SUMMARY OF THE INVENTION 
     There is provided, in accordance with an embodiment of the present invention, a medical apparatus, including an insertion tube having a distal end configured for insertion into a body cavity and containing a lumen passing through the insertion tube, a flexible probe configured to be deployed from the distal end of the insertion tube and to assume an arcuate shape upon deployment within the body cavity, a plurality of electrodes distributed along the probe, and a balloon configured to have a portion of the balloon surrounded by the arcuate-shaped probe and to be inflated by passage of a fluid through the lumen while the probe is deployed in the body cavity. 
     In some embodiments, the balloon, when inflated, exerts an outward force against the arcuate-shaped probe so as to press the electrodes against tissue in the body cavity. 
     In further embodiments, the body cavity includes a pulmonary vein, and the tissue includes intravenous tissue. In one embodiment, inflating the balloon forms a seal between the balloon and the intravenous tissue so as to prevent blood flowing through the pulmonary vein from coming in contact with the electrodes. 
     In additional embodiments, a given electrode is configured to convey ablation energy to tissue in the body cavity in contact with the given electrode. 
     In supplementary embodiments, a given electrode includes perforations configured to deliver an irrigation fluid to the tissue. 
     In other embodiments, a given electrode is configured to generate a signal indicating an electrical potential in tissue in the body cavity in contact with the electrode. 
     In supplementary embodiments, the medical apparatus may also include an extender shaft contained within the insertion tube, affixed to a distal end of the balloon, and configured to position the balloon within the arcuate-shaped probe when extended from the insertion tube. In one embodiment, the medical apparatus may additionally include a position transducer affixed to the extender shaft. 
     In some embodiments, the arcuate shape has a radius of curvature between 15 mm and 30 mm. 
     There is also provided, in accordance with an embodiment of the present invention, a method for fabricating a catheter including providing an insertion tube having a distal end configured for insertion into a body cavity and containing a lumen passing through the insertion tube, providing a flexible probe configured to be deployed from the distal end of the insertion tube and to assume an arcuate shape upon deployment within the body cavity, distributing a plurality of electrodes along the probe and providing a balloon configured to have a portion of the balloon surrounded by the arcuate-shaped probe and to be inflated by passage of a fluid through the lumen while the probe is deployed in the body cavity. 
     There is additionally provided, in accordance with an embodiment of the present invention, method for treatment, including inserting, into a body cavity, an insertion tube having a distal end containing a lumen passing through the insertion tube, deploying, into the body cavity from the distal end, an arcuate shaped flexible probe including a plurality of electrodes, deploying, from the insertion tube, a balloon to within the arcuate-shaped probe, inflating, by passing a fluid through the lumen, the balloon, thereby exerting an outward force against the arcuate-shaped probe so as press the electrodes against tissue in the body cavity, and performing, using the electrodes, a medical procedure on the tissue. 
     In one embodiment, inflating the balloon exerts an outward force against the arcuate-shaped probe so as to press the electrodes against tissue in the body cavity. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
         FIG. 1  is a schematic, pictorial illustration of a medical system comprising a catheter and a control console, in accordance with an embodiment of the present invention; 
         FIG. 2  is a schematic cutaway view of a distal end of the catheter comprising a medical probe having an arcuate-shaped end section and a balloon that can be deployed within the arcuate-shaped end section, in accordance with an embodiment of the present invention; 
         FIG. 3  is a flow diagram that schematically illustrates a method of performing a medical procedure using the arcuate-shaped end section and the balloon, in accordance with an embodiment of the present invention; 
         FIG. 4  is a schematic pictorial illustration of the distal end of the catheter positioned in a pulmonary vein, in accordance with an embodiment of the present invention; 
         FIG. 5  is a schematic pictorial illustration of the arcuate-shaped end section of the medical probe deployed within the pulmonary vein, in accordance with an embodiment of the present invention; and 
         FIG. 6  is a schematic pictorial illustration of the balloon deployed within the arcuate-shaped end section, in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Ablation and mapping are examples of medical procedures that can be performed on a pulmonary vein by electrodes distributed on a lasso catheter. However, even when the lasso catheter is positioned correctly within the pulmonary vein, all the electrodes of lasso catheter may not contact the tissue of the vein. Additionally, even if there is contact, the contact may not be good enough for ablation and/or for good signal acquisition (i.e., for mapping). 
     Embodiments of the present invention provide a medical apparatus that combines an arcuate-shaped (i.e., a lasso-shaped) end section with a balloon that can be used to expand the diameter of the arcuate-shaped end section. As described hereinbelow, the medical apparatus comprises an insertion tube, a flexible probe, a plurality of electrodes distributed along the probe, and a balloon. The flexible probe has a distal end configured for insertion into a body cavity and contains a lumen passing through the insertion tube, and the flexible probe is configured to assume an arcuate shape upon being deployed from the distal end of the insertion tube into the body cavity. The balloon is configured to have a portion of the balloon surrounded by the arcuate-shaped probe, and to be inflated by passage of a fluid through the lumen while the probe is deployed in the body cavity. 
     In some embodiments inflating the balloon exerts an outward force against the arcuate-shaped probe so as press the electrodes against tissue in the body cavity. Therefore, medical systems implementing embodiments of the present invention can reduce, or even completely prevent, contact of the parts of the electrodes that are not facing the vein with the blood pool in the vein. This is advantageous when using the electrodes for medical procedures comprising ablation and/or signal acquisition. 
     System Description 
       FIG. 1  is a schematic, pictorial illustration of a medical system  20  comprising a catheter  22  and a control console  24 , in accordance with an embodiment of the present invention. As described in more detail in  FIG. 2  hereinbelow, catheter  22  comprises a flexible medical probe that assumes an arcuate shape upon deployment from a distal end  26  of the catheter, and a balloon that can be deployed from the distal end and positioned within the arcuate-shaped probe. Medical system  20  may be based, for example, on the CARTO® system, produced by Biosense Webster Inc. of 33 Technology Drive, Irvine, Calif., U.S.A. 
     In embodiments described hereinbelow, catheter  22  can be used for diagnostic or therapeutic treatment. In one embodiment, medical system  20  can use catheter  22  for mapping electrical potentials of a heart  28  of a patient  30 . In another embodiment, medical system  20  can use catheter  22  for ablation of tissue in heart  28 . Alternatively, catheter  22  may be used, mutatis mutandis, for other therapeutic and/or diagnostic purposes in the heart or in other body organs. 
     Catheter  22  comprises an insertion tube  32  and a handle  34  coupled to a proximal end of the insertion tube. By manipulating handle  34 , a medical professional  36  can insert catheter  22  into a body cavity in patient  30 . For example, medical professional  36  can insert catheter  22  through the vascular system of patient  30  so that distal end  26  of catheter  22  enters a chamber of heart  28  or a given pulmonary vein  38  and engages myocardial or intravenous tissue at a desired location or locations. 
     In the configuration shown in  FIG. 1 , system  20  uses magnetic-based position sensing and/or impedance-based location sensing. System  20  can use magnetic-based position sensing to determine position coordinates indicating a location and an orientation of distal end  26  in a coordinate system  40  comprising an X-axis  42 , a Y-axis  44  and a Z-axis  46 , and the medical system can use impedance-based location sensing to determine location coordinates of the distal end in the coordinate system. 
     To implement magnetic based position sensing, control console  24  comprises a driver circuit  48  which drives field generators  50  to generate magnetic fields within the body of patient  30 . Typically, field generators  50  comprise coils, which are placed below the patient&#39;s torso at known positions external to patient  30 . These coils generate magnetic fields in a predefined working volume that contains heart  28 . 
     Medical system  20  also comprises a position transducer such as a magnetic field sensor  52  that is associated with catheter  22  and a processor  54  in medical console  24 . The association is described in more detail below, with reference to  FIG. 2 . In response to the magnetic fields from the field generator coils, magnetic field sensor  52  generates and conveys electrical signals indicating a current position (i.e., location and orientation) of distal end  26 , and processor  54  is configured to receive and process the conveyed signals in order to compute, in coordinate system  40 , orientation and location coordinates of the distal end. 
     Magnetic position tracking techniques are described, for example, in U.S. Pat. Nos. 5,391,199, 5,443,489, 6,788,967, 5,558,091, 6,172,499 and 6,177,792. The methods of location sensing described hereinabove are implemented in the above-mentioned CARTO® system and are described in detail in the patents cited above. 
     As described supra, medical system  20  can also use impedance-based location sensing to determine location coordinates of distal end  26  in coordinate system  40 . Control console  24  is connected, by a cable  56 , to body surface electrodes, which typically comprise adhesive skin patches  58  that are affixed to patient  30 . In the configuration shown in  FIG. 1 , cable  56  also connects field generators  50  to console  24 . Control console  24  also comprises a current tracking module  60  that, in conjunction with processor  54 , determines position coordinates of distal end  26  inside heart  28  based on impedances measured between adhesive skin patches  58  and electrodes  62  that are affixed to a medical probe  64 , as shown in  FIG. 2 . 
     Impedance-based position tracking techniques are described, for example, in U.S. Pat. Nos. 5,983,126, 6,456,864 and 5,944,022. The methods of position sensing described hereinabove are implemented in the above-mentioned CARTO® system and are described in detail in the patents cited above. 
     In embodiments described herein, electrodes  62  can also be configured to apply a signal to tissue in heart  28  or a given pulmonary vein  38 , and/or to measure a certain physiological property (e.g., the local surface electrical potential) at a location in the heart or the given pulmonary vein. In additional embodiments, electrodes  62  can be configured to deliver ablation energy to the tissue in heart  28  or a given pulmonary vein  38 . Electrodes  62  are connected to control console  24  by wires (not shown) running through probe  64 . 
     Processor  54  may comprise real-time noise reduction circuitry  66  typically configured as a field programmable gate array (FPGA), followed by an analog-to-digital (A/D) ECG (electrocardiograph) signal conversion integrated circuit  68 . The processor can pass the signal from A/D ECG circuit  68  to another processor and/or can be programmed to perform one or more algorithms disclosed herein, each of the one or more algorithms comprising steps described hereinbelow. The processor uses circuitry  66  and circuit  68 , as well as features of modules which are described in more detail below, in order to perform the one or more algorithms. 
     Control console  24  also comprises an input/output (I/O) communications interface  70  that enables the control console to transfer signals from, and/or transfer signals to magnetic field sensor  52 , electrodes  62  and adhesive skin patches  58 . Based on signals received from magnetic field sensor  52  and/or electrodes  62  and/or adhesive skin patches  58 , processor  54  can generate a map  72  that shows the position of distal end  26  in the patient&#39;s body. 
     During a procedure, processor  54  can present map  72  to medical professional  36  on a display  74 , and store data representing the map in a memory  76 . Memory  76  may comprise any suitable volatile and/or non-volatile memory, such as random-access memory or a hard disk drive. 
     In some embodiments, medical professional  36  can manipulate map  72  using one or more input devices  78 . In alternative embodiments, display  74  may comprise a touchscreen that can be configured to accept inputs from medical professional  36 , in addition to presenting map  72 . 
     In the configuration shown in  FIG. 1 , control console  24  also comprises an ablation module  80 , an inflation module  82  and an irrigation module  84 , whose respective functionalities are described in the description referencing  FIG. 2  hereinbelow. 
       FIG. 2  is a schematic cutaway view of distal end  26  of catheter  22 , in accordance with an embodiment of the present invention. In the configuration shown in  FIG. 2 , catheter  22  comprises medical probe  64 , also termed herein a lasso probe or a lasso catheter, and a balloon probe  90 . Medical probe  64  and balloon probe  60  are contained within insertion tube  32  and are configured to extend from a lumen  92  in the insertion tube at distal end  26 . 
     Medical probe  64  comprises an end section  94  that is affixed to a tubular shaft  96 . End section  94  is configured to form an arcuate shape when deployed from lumen  92  and comprises a plurality of cylinder-shaped electrodes  62  disposed along its length. Electrodes  62  are connected to console  24  by wires  98  running through tubular shaft  96 . 
     In one embodiment, as described supra, medical system  20  can use electrodes  62  and adhesive skin patches  58  to determine location coordinates of end section  94  in patient  30 . In another embodiment, electrodes  62  can be configured to convey (i.e., to processor  54 ) signals indicating electrical potentials in tissue in contact with the electrodes. 
     In a further embodiment as described supra, medical system  20  can use electrodes  62  to ablate tissue in heart  28  and/or a given pulmonary vein  38 . In these embodiments, ablation module  80  can generate and control delivery of ablation energy (e.g., radio-frequency energy) to electrodes  62  via I/O interface  70 . 
     In embodiments where medical system  20  uses electrodes  62  for tissue ablation, the electrodes may have multiple perforations  100  through which irrigation fluid (e.g., a saline solution) may be delivered to the tissue with which the electrodes are in contact during ablation. The irrigation fluid can be delivered via an irrigation lumen  102  that is contained within tubular shaft  96  and connected to irrigation module  84 . Irrigation module  84  is configured to force the irrigation fluid into irrigation lumen  102  at a controllable pumping rate. 
     The arcuate shape of end section  94  may be maintained, for example, by incorporating a thin strut made from a shape memory material, such as Nitinol (not shown in the figures), in the desired shape within the end section. The strut is made sufficiently flexible to permit the end section to straighten during insertion and withdrawal through insertion tube  32 , but to resume its arcuate form when it is unconstrained inside a body cavity of patient  30 . The radius of curvature of end section  94 , when unconstrained (i.e., when deployed from lumen  92 ), is typically between 15 mm and 30 mm. 
     Balloon probe  90  comprises a balloon  104  that is affixed to a tubular shaft  106 . Balloon  104  is typically formed from bio-compatible material such as polyethylene terephthalate (PET), polyurethane, Nylon, or Pebax. 
     In some embodiments, inflation module  82  can pump, via an inflation lumen  108  contained in shaft  106 , a fluid (e.g., normal saline) into balloon  104  so as to inflate the balloon. 
     In the configuration shown in  FIG. 2 , balloon probe  90  comprises an extender shaft  110  and magnetic field sensor  52  is affixed to the extender shaft. Extender shaft  110  is contained within tubular shaft  106  and is coupled to a distal end  112  of balloon  104 . In operation, medical professional  36  can control a length  114  of balloon  104  (i.e., once the balloon is deployed from lumen) by extending or extracting extender shaft  110 , and the medical professional can control a width  116  of the balloon by specifying, to inflation module  82 , a volume of irrigation fluid to deliver into the balloon. 
     While the configuration in  FIG. 2  shows the position transducer comprising magnetic field sensor  52 , other types of position transducers are considered to be within the spirit and scope of the present invention. For example, the position transducer may comprise a pair of additional electrodes that are distributed along extender shaft  110 , which together can be used by current tracking module  60  and processor  54 , typically after a calibration process, to determine location and orientation of distal end  112 . 
     In operation, extender shaft  110  is configured (i.e., when extended from insertion tube  32 ) to deploy balloon  104  from shaft  106 , and to position the balloon such that portions of the balloon are surrounded by arcuate-shaped end section  94 . Additionally, in embodiments of the present invention, medical professional  36  can control a diameter of arcuate-shaped end section  94  by controlling the pressure of the fluid used to inflate the balloon. Inflating balloon  104  increases width  116 , thereby exerting an outward force  120  against arcuate-shaped end section  94  so as to increase the diameter of the arcuate-shaped end section. 
     As described hereinabove, end section  94  of medical probe  64  is configured to be deployed from lumen  92 , extender shaft  106  is configured to be deployed from tubular shaft  106 , and balloon  104  is configured to be inflated by fluid delivered via inflation lumen  108 . In one embodiment, medical professional  36  can use input devices  78  to manage one or more of these operations. In another embodiment, handle  34  may comprise one or more controls (not shown) to manage one or more of these operations. 
     Lasso Catheter Deployment and Sizing 
       FIG. 3  is a flow diagram that schematically illustrates a method using catheter  22  to perform a medical procedure in heart  28 , and  FIG. 4  is a schematic pictorial illustration of distal end  26  in a given pulmonary vein  38 , in accordance with an embodiment of the present invention. 
     In an insertion step  130 , medical professional  36  manipulates, using handle  34 , catheter  22  so as to insert distal end  26  into the given pulmonary vein. As shown in  FIG. 4 , when initially inserting distal end  26  into the given pulmonary vein, probes  64  and  90  are typically still recessed (i.e., not deployed) within insertion tube  32 . 
     In a first deployment step  132 , medical professional  36  deploys, from the distal end of insertion tube  32 , end section of medical probe  64  into the given pulmonary vein. As described supra, upon deploying end section  94  from the distal end of insertion tube  32 , the end section assumes an arcuate shape. 
       FIG. 5  is a schematic pictorial illustration showing arcuate-shaped end section  94  deployed into the given pulmonary vein. As shown in  FIG. 5 , upon assuming an arcuate shape, diameter  118  of end section  94  may not be sufficient to enable all electrodes  62  to engage intravenous tissue  150 . 
     In a second deployment step  134 , medical professional  36  deploys balloon  104 , in its uninflated state from the distal end of insertion tube  32  to within arcuate-shaped end section  94 . The balloon is deployed by extending extender shaft  110  distally, and processor  58  checks that the balloon is within section  54  using position measurements from sensor  52 , and positions of electrodes  62 . In some embodiments processor  58  may provide a notification to professional  36 , by any convenient means such as a notice on display  74 , of correct deployment of balloon  104 . 
     In an inflation step  136 , the medical professional conveys an instruction (e.g., using input devices  78 ) to inflation module  82  to inflate the balloon. In embodiments of the present invention, inflating balloon  104  exerts outward force  120  on end section  94  so that all electrodes  62  press against (i.e., engage) intravenous tissue  150 . 
       FIG. 6  is a schematic pictorial illustration showing arcuate-shaped end section  94  deployed into the given pulmonary vein, and balloon  104  deployed within the arcuate-shaped end section and inflated so that outward force  120  presses electrodes  62  against intravenous tissue  150 . As shown in  FIG. 6 , the flexible property of balloon  104  causes the balloon to envelop end section  94  and form a seal between the balloon and intravenous tissue  150  as outward force  120  presses electrodes  62  against the intravenous tissue. Therefore electrodes  62  are in contact with balloon  104  and electrodes  62  but are not in contact with blood  160  flowing through the pulmonary vein. This is advantageous when the electrodes are used for medical procedures such as ablation or signal acquisition, as described hereinbelow. 
     In a treatment selection step  138 , if the medical procedure to be performed is ablation, then in an ablation step  140 , medical professional conveys an instruction to ablation module  80  to deliver ablation energy to electrodes  62 , which in turn, conveys the ablation energy to the intravenous tissue in contact with the electrodes, and the method ends. Returning to step  138 , if the medical procedure to be performed is signal acquisition, then in a mapping step  142 , medical professional  36  conveys an instruction to processor  54  to measure electrical potentials at locations on intravenous tissue  150  that are engaged by electrodes  62 , and the method ends. 
     It will be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.