Patent Publication Number: US-2023149075-A1

Title: Catheter with Stretchable Irrigation Tube

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation application of U.S. patent application Ser. No. 16/863,980 filed Apr. 30, 2020, the entire contents of which is incorporated herein by reference as if fully set forth below. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to medical devices, and in particular, but not exclusively to, catheters. 
     BACKGROUND 
     A wide range of medical procedures involve placing probes, such as catheters, within a patient&#39;s body. Location sensing systems have been developed for tracking such probes. Magnetic location sensing is one of the methods known in the art. In magnetic location sensing, magnetic field generators are typically placed at known locations external to the patient. A magnetic field sensor within the distal end of the probe generates electrical signals in response to these magnetic fields, which are processed to determine the coordinate locations of the distal end of the probe. These methods and systems are described in U.S. Pat. Nos. 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and 6,332,089, in PCT International Publication No. WO 1996/005768, and in U.S. Patent Application Publications Nos. 2002/0065455, issued as U.S. Pat. No. 6,690,963 on Feb. 10, 2004, and 2003/0120150 issued as U.S. Pat. No. 7,729,742 on Jun. 1, 2010, and 2004/0068178, now abandoned. Locations may also be tracked using impedance or current based systems. 
     One medical procedure in which these types of probes or catheters have proved extremely useful is in the treatment of cardiac arrhythmias Cardiac arrhythmias and atrial fibrillation in particular, persist as common and dangerous medical ailments, especially in the aging population. 
     Diagnosis and treatment of cardiac arrhythmias include mapping the electrical properties of heart tissue, especially the endocardium, and selectively ablating cardiac tissue by application of energy. Such ablation can cease or modify the propagation of unwanted electrical signals from one portion of the heart to another. The ablation process destroys the unwanted electrical pathways by formation of non-conducting lesions. Various energy delivery modalities have been disclosed for forming lesions, and include use of microwave, laser and more commonly, radiofrequency energies to create conduction blocks along the cardiac tissue wall. In a two-step procedure, mapping followed by ablation, electrical activity at points within the heart is typically sensed and measured by advancing a catheter containing one or more electrical sensors into the heart, and acquiring data at a multiplicity of points. These data are then utilized to select the endocardial target areas at which the ablation is to be performed. 
     Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral vein, and then guided into the chamber of the heart of concern. A typical ablation procedure involves the insertion of a catheter having a one or more electrodes at its distal end into a heart chamber. A reference electrode may be provided, generally taped to the skin of the patient or by means of a second catheter that is positioned in or near the heart. RF (radio frequency) current is applied through the tip electrode(s) of the ablating catheter, and current flows through the media that surrounds it, i.e., blood and tissue, between the tip electrode(s) and an indifferent electrode. The distribution of current depends on the amount of electrode surface in contact with the tissue as compared to blood, which has a higher conductivity than the tissue. Heating of the tissue occurs due to its electrical resistance. The tissue is heated sufficiently to cause cellular destruction in the cardiac tissue resulting in formation of a lesion within the cardiac tissue which is electrically non-conductive. 
     US Patent Publication 2019/0117301 of Steinke, et al., issued as U.S. Pat. No. 11,382,688 on Jul. 12, 2022, describes a catheter and catheter system for treatment of a blood vessel of a patient include an elongate flexible catheter body with a radially expandable structure. A plurality of electrodes or other electrosurgical energy delivery surfaces can radially engage material to be treated when the structure expands. A material detector near the distal end of the catheter body may measure circumferential material distribution, and a power source selectively energizes the electrodes to eccentrically treat of a body lumen. 
     U.S. Pat. No. 9,757,180 to Gelfand, et al., describes systems, devices, and methods for treating a patient having a sympathetically mediated disease associated at least in part with augmented peripheral chemoreflex or heightened sympathetic activation. The treatments include ablating one or more peripheral chemoreceptors or associated afferent nerves to reduce or remove afferent neural signals from the peripheral chemoreceptor. 
     U.S. Pat. No. 9,474,486 to Eliason, et al., describes an electrophysiology catheter. In one embodiment, the catheter includes an elongated, deformable shaft having a proximal end and a distal end and a basket electrode assembly coupled to the distal end of the shaft. The basket electrode assembly has a proximal end and a distal end and is configured to assume a compressed state and an expanded state. The electrode assembly further includes one or more tubular splines having a plurality of electrodes disposed thereon and a plurality of conductors. Each of the plurality of conductors extends through the tubular spline from a corresponding one of the plurality of electrodes to the proximal end of the basket electrode assembly. The tubular splines are configured to assume a non-planar (e.g., a twisted or helical) shape in the expanded state. 
     International Patent Publication WO 2019/074733 of St. Jude Medical Cardiology Div. Inc. describes high-density mapping catheters with an array of mapping electrodes. These catheters can be used for diagnosing and treating cardiac arrhythmias, for example. The catheters are adapted to contact tissue and comprise a flexible framework including the electrode array. The array of electrodes may be formed from a plurality of columns of longitudinally-aligned and rows of laterally-aligned electrodes. 
     U.S. Pat. No. 10,362,952 to Basu, et al., describes a catheter for diagnosing and ablating tissue that has a stabilized spine electrode assembly. The stabilized spine electrode assembly has at least two spines secured to the catheter body at their proximal ends and at least one tether, secured between locations distal of the proximal ends of adjacent spines. The spines have a collapsed arrangement in which the spines are arranged generally along a longitudinal axis of the catheter body and an expanded arrangement in which at least a portion of each spine bows radially outwards from the longitudinal axis and the at least one tether exerts tension on the adjacent spines. 
     SUMMARY OF THE INVENTION 
     There is provided in accordance with an embodiment of the present disclosure, a medical system including a catheter configured to be inserted into a body part of a living subject, and including a deflectable element having a distal end, an expandable distal end assembly disposed at the distal end of the deflectable element, and including a plurality of electrodes, a distal portion, and a proximal portion, and configured to expand from a collapsed form to an expanded deployed form, and a stretchable irrigation tube disposed between the distal portion and the proximal portion, and including a plurality of irrigation holes, and configured to stretch longitudinally when the distal end assembly is collapsed from the expanded deployed form to the collapsed form. 
     Further in accordance with an embodiment of the present disclosure the irrigation holes are disposed radially around the irrigation tube. 
     Still further in accordance with an embodiment of the present disclosure the irrigation holes are disposed longitudinally along the irrigation tube. 
     Additionally, in accordance with an embodiment of the present disclosure the irrigation holes are disposed longitudinally along the irrigation tube. 
     Moreover in accordance with an embodiment of the present disclosure, the system includes an ablation power generator configured to be connected to the catheter, and apply an electrical signal to the electrodes, an irrigation reservoir configured to store irrigation fluid, and a pump configured to be connected to the irrigation reservoir and the catheter, and to pump the irrigation fluid from the irrigation reservoir through the irrigation holes of the irrigation tube. 
     Further in accordance with an embodiment of the present disclosure a relaxed state of the distal end assembly is the expanded deployed form, the distal end assembly being configured to collapse into the collapsed form when the catheter is retracted in a sheath. 
     Still further in accordance with an embodiment of the present disclosure a relaxed state of the distal end assembly is the collapsed form, the system further including a puller element disposed inside the deflectable element and the stretchable irrigation tube, and connected to the distal portion of the distal end assembly, and configured when pulled to expand the distal end assembly from the collapsed form to the expanded deployed form. 
     Additionally, in accordance with an embodiment of the present disclosure the distal end assembly includes a basket assembly. 
     Moreover, in accordance with an embodiment of the present disclosure the basket assembly includes a plurality of splines. 
     Further in accordance with an embodiment of the present disclosure the splines include Nitinol. 
     Still further in accordance with an embodiment of the present disclosure the stretchable irrigation tube includes a biocompatible stretchable material. 
     Additionally, in accordance with an embodiment of the present disclosure the holes include laser drilled holes. 
     Moreover, in accordance with an embodiment of the present disclosure the biocompatible stretchable material includes Polyether block amide (PEBA). 
     Further in accordance with an embodiment of the present disclosure the biocompatible stretchable material is a porous material that includes pores forming at least some of the holes. 
     Still further in accordance with an embodiment of the present disclosure the biocompatible stretchable material includes expanded Polytetrafluoroethylene (ePTFE). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood from the following detailed description, taken in conjunction with the drawings in which: 
         FIG.  1    is a schematic view of a medical system constructed and operative in accordance with an embodiment of the present invention; 
         FIG.  2    is a schematic view of a catheter in a collapsed form constructed and operative in accordance with an embodiment of the present invention; 
         FIG.  3    is a schematic view of the catheter of  FIG.  2    in a deployed form; 
         FIG.  4    is a cross-sectional view of the catheter of  FIG.  3    along line A:A; 
         FIG.  5    is a more detailed cross-sectional view of the catheter inside block A of  FIG.  4   ; 
         FIG.  6    is a more detailed cross-sectional view of the catheter inside block B of  FIG.  4   ; 
         FIG.  7 A  is a schematic view of a catheter in a collapsed form constructed and operative in accordance with an alternative embodiment of the present invention; and 
         FIG.  7 B  is a schematic view of the catheter of  FIG.  7 A  in a deployed form. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Overview 
     Irrigation is commonly used with catheters to provide cooling during medical procedures such as radio-frequency (RF) ablation, for example. One solution for providing irrigation in a basket-type catheter is to have an irrigation channel run through the catheter which terminates in the middle of the basket. Irrigation fluid may then be pumped through the irrigation channel to the distal end of the irrigation channel where the irrigation fluid exits and provides cooling to tissue in the region of the basket as well as diluting blood locally. However, the irrigation is not very well directed and although it may be sufficient for electroporation, which does not generate much heat, it is generally not sufficient to reduce heat created during RF ablation. An additional problem encountered with basket catheters is that the basket needs to be in a collapsed or semi-collapsed form during insertion into the body and then deployed to its expanded form in a body cavity. The requirement to be able to collapse and expand the basket adds further complications to providing effective irrigation as an irrigation channel may interfere with the expansion and collapsing of the basket. 
     Embodiments of the present invention, provide a catheter with an expandable distal end assembly (such as a basket) including electrodes thereon, with a stretchable irrigation tube fixed between a proximal and distal end of the assembly. The irrigation tube includes holes around the tube to direct irrigation fluid in different directions to provide effective irrigation and cooling. Using a stretchable tube allows the irrigation tube (and therefore the irrigation holes) to extend from the proximal to the distal end of the assembly as the tube stretches and relaxes according to the form of the assembly so that when the assembly is collapsed, the tube is stretched, and when the assembly is expanded, the tube relaxes. 
     In some embodiments, the holes are disposed along the length of the tube and around the circumference of the tube to provide a much more uniform irrigation spray throughout the distal end assembly. The tube may be made formed from any suitable biocompatible stretchable material, such as Polyether block amide (PEBA) (e.g., PEBAX (with a shore D durometer between 25 and 72)), or a stretchable Polyurethane, a silicone polymer, or expanded Polytetrafluoroethylene (ePTFE). Holes may be made in the tube using any suitable method for example, but not limited to, laser drilling. Some materials such as ePTFE may include pores which are formed when the material is pre-stretched or electrospun. The pores may then provide the irrigation holes in the irrigation tube. When the holes are numerous enough (e.g., with a porous tubes), the irrigation fluid may weep from the tube instead of being sprayed. Nevertheless, providing irrigation via weeping provides sufficient irrigation in many applications. 
     In some embodiments, the distal end assembly is collapsed by being retracted into a catheter sheath. In other embodiments, the distal end assembly has a naturally collapsed form and pulling a puller wire causes the distal end assembly to expand. The puller wire may be disposed in the stretchable irrigation tube and is connected to the distal end of the distal end assembly. 
     System Description 
     Reference is now made to  FIG.  1   , which is a schematic view of a medical system  20  constructed and operative in accordance with an embodiment of the present invention. The system  20  includes a catheter  40  configured to be inserted into a body part of a living subject (e.g., a patient  28 ). A physician  30  navigates the catheter  40  (for example, a basket catheter produced Biosense Webster, Inc. of Irvine, Calif., USA), to a target location in a heart  26  of the patient  28 , by manipulating an elongated deflectable element  22  of the catheter  40 , using a manipulator  32  near a proximal end of the catheter  40 , and/or deflection from a sheath  23 . In the pictured embodiment, physician  30  uses catheter  40  to perform electro-anatomical mapping of a cardiac chamber and ablation of cardiac tissue. 
     Catheter  40  includes an expandable distal end assembly  35  (e.g., a basket assembly), which is inserted in a folded configuration, through sheath  23 , and only after the catheter  40  exits sheath  23  does the distal end assembly  35  regain its intended functional shape. By containing distal end assembly  35  in a folded configuration, sheath  23  also serves to minimize vascular trauma on its way to the target location. 
     Catheter  40  includes a plurality of electrodes  48  for sensing electrical activity and/or applying ablation power to ablate tissue of the body part. Catheter  40  may incorporate a magnetic sensor (not shown) at the distal edge of deflectable element  22  (i.e., at the proximal edge of the distal end assembly  35 ). Typically, although not necessarily, the magnetic sensor is a Single-Axis Sensor (SAS). A second magnetic sensor (not shown) may be included at any suitable position on the assembly  35 . The second magnetic sensor may be a Triple-Axis Sensor (TAS) or a Dual-Axis Sensor (DAS), or a SAS by way of example only, based for example on sizing considerations. The magnetic sensors and electrodes  48  disposed on the assembly  35  are connected by wires running through deflectable element  22  to various driver circuitries in a console  24 . 
     In some embodiments, system  20  comprises a magnetic-sensing sub-system to estimate an ellipticity of the basket assembly  35  of catheter  40 , as well as its elongation/retraction state, inside a cardiac chamber of heart  26  by estimating the elongation of the basket assembly  35  from the distance between the magnetic sensors. Patient  28  is placed in a magnetic field generated by a pad containing one or more magnetic field generator coils  42 , which are driven by a unit  43 . The magnetic fields generated by coil(s)  42  transmit alternating magnetic fields into a region where the body-part is located. The transmitted alternating magnetic fields generate signals in the magnetic sensors, which are indicative of position and/or direction. The generated signals are transmitted to console  24  and become corresponding electrical inputs to processing circuitry  41 . 
     The method of position and/or direction sensing using external magnetic fields and magnetic sensors, is implemented in various medical applications, for example, in the CARTO® system, produced by Biosense-Webster, 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, in PCT Patent Publication WO 96/05768, and in U.S. Patent Application Publications 2002/0065455 A1, issued as U.S. Pat. No. 6,690,963 on Feb. 10, 2004; 2003/0120150 A1 issued as U.S. Pat. No. 7,729,742 on Jun. 1, 2010, and 2004/0068178 A1, now abandoned. 
     Processing circuitry  41 , typically part of a general-purpose computer, is further connected via a suitable front end and interface circuits  44 , to receive signals from body surface-electrodes  49 . Processing circuitry  41  is connected to body surface-electrodes  49  by wires running through a cable  39  to the chest of patient  28 . 
     In an embodiment, processing circuitry  41  renders to a display  27 , a representation  31  of at least a part of the catheter  40  and a mapped body-part, responsively to computed position coordinates of the catheter  40 . 
     Processing circuitry  41  is typically programmed in software to carry out the functions described herein. The software may be downloaded to the computer in electronic form, over a network, for example, or it may, alternatively or additionally, be provided and/or stored on non-transitory tangible media, such as magnetic, optical, or electronic memory. 
     The medical system  20  may also include an ablation power generator  69  (such as an RF signal generator) configured to be connected to the catheter  40 , and apply an electrical signal to the electrodes  48 . The medical system  20  may also include an irrigation reservoir  71  configured to store irrigation fluid, and a pump  73  configured to be connected to the irrigation reservoir  71  and the catheter  40 , and to pump the irrigation fluid from the irrigation reservoir  71  through irrigation holes of an irrigation tube of the catheter  40  as described in more detail with reference to  FIGS.  2  and  3   . 
     The example illustration shown in  FIG.  1    is chosen purely for the sake of conceptual clarity.  FIG.  1    shows only elements related to the disclosed techniques for the sake of simplicity and clarity. System  20  typically comprises additional modules and elements that are not directly related to the disclosed techniques, and thus are intentionally omitted from  FIG.  1    and from the corresponding description. The elements of system  20  and the methods described herein may be further applied, for example, to control an ablation of tissue of heart  26 . 
     Reference is now made to  FIGS.  2  and  3   .  FIG.  2    is a schematic view of the catheter  40  in a collapsed form constructed and operative in accordance with an embodiment of the present invention.  FIG.  3    is a schematic view of the catheter  40  of  FIG.  2    in a deployed expanded form. 
     The catheter  40  is configured to be inserted into a body part (e.g., the heart  26  ( FIG.  1   )) of a living subject. The deflectable element  22  of the catheter  40  has a distal end  33 . The deflectable element  22  may be produced from any suitable material, for example, polyurethane or polyether block amide. The assembly  35  is disposed distally to the deflectable element  22  and may be connected to the deflectable element  22  via a proximal coupling member  50  at the distal end  33 . The proximal coupling member  50  typically comprises a hollow tube and may be formed from any suitable material, for example, but not limited to polycarbonate with or without glass filler, polyether ether ketone (PEEK) with or without glass filler, polyimide, polyamide, or Polyetherimide (PEI) with or without glass filler. The coupling member  50  may formed as an integral part of the deflectable element  22  or as part of the distal end assembly  35  or as a separate element which connects with the deflectable element  22  and the distal end assembly  35 . 
     The assembly  35 , which may include a basket assembly, may include multiple splines such as flexible strips  55  (only one labeled for the sake of simplicity). In the embodiments of  FIGS.  2  and  3    each flexible strip  55  includes a single electrode  48  (only some labeled for the sake of simplicity). The assembly  35  may include any suitable number of electrodes  48  with multiple electrodes  48  per strip  55 . 
     In the embodiment of  FIGS.  2  and  3   , each flexible strip  55  is formed of Nitinol which is selectively covered with insulating material in the distal and proximal regions  57  (only some labeled for the sake of simplicity) of the flexible strips  55  leaving a central region  59  (only some labeled for the sake of simplicity) of the flexible strips  55  as an electrically active region to perform mapping and/or perform ablation or electroporation, by way of example. The structure of the assembly  35  may vary. For example, flexible strips  55  (or other splines) may include flexible printed circuit boards (PCBs), or a shape-memory alloy such as Nitinol. 
     Embodiments described herein refer mainly to a basket distal-end assembly  35 , purely by way of example. In alternative embodiments, the disclosed techniques can be used with any other suitable type of distal-end assembly. 
     The distal end assembly  35  includes a distal portion  61 , and a proximal portion  63 , and is configured to expand from a collapsed form (shown in  FIG.  2   ) to an expanded deployed form (shown in  FIG.  3   ). 
     The relaxed state of the distal end assembly  35  is the expanded deployed form shown in  FIG.  3   . The distal end assembly  35  is configured to collapse into the collapsed form when the catheter  40  is retracted in a sheath  23  ( FIG.  1   ) and is configured to expand to the expanded deployed form when the catheter  40  is removed from the sheath  23 . The relaxed shape of the distal end assembly  35  may be set by forming the flexible strips  55  from any suitable resilient material such as Nitinol or PEI. 
     The catheter  40  includes a stretchable irrigation tube  65  disposed between the distal portion  61  and the proximal portion  63 . The stretchable irrigation tube  65  includes a plurality of irrigation holes  67  (only some labeled for the sake of simplicity), and is configured to stretch longitudinally when the distal end assembly  35  is collapsed from the expanded deployed form to the collapsed form. The stretchable irrigation tube  65  includes a biocompatible stretchable material, such as Polyether block amide (PEBA) (e.g., PEBAX (with a shore D durometer between 25 and 72-55D)), or a stretchable Polyurethane, a silicone polymer, or expanded Polytetrafluoroethylene (ePTFE). The stretchable irrigation tube  65  may have any suitable dimensions, for example, an outer diameter in the range of 0.5 mm to 3 mm, e.g., 1.5 mm, a wall thickness in the range of 0.01 mm to 0.5 mm, e.g., 0.125 mm. The holes  67  may have any suitable diameter, for example, in the range of approximately 0.01 mm to approximately 0.2 mm, e.g. approximately 0.165 mm. The tube  65  may include any suitable number of discrete holes, for example, between 1 and 200, e.g. 50. The stretchable irrigation tube  65  is shown in  FIG.  3    as a transparent stretchable irrigation tube  65  for the sake of clarity. Alternatively, the stretchable irrigation tube  65  may be translucent or opaque or any suitable combination thereof. The pump  73  ( FIG.  1   ) is configured to pump irrigation fluid from the irrigation reservoir  71  through the irrigation holes  67  of the irrigation tube  65 . 
     In some embodiments, the irrigation holes  67  are disposed radially around the irrigation tube  65  and/or longitudinally along the irrigation tube  65 . In other embodiments, the irrigation holes  67  can be disposed such that each hole  67  extends at an angle relative to the longitudinal axis. In one embodiment, each hole may extend at an angle of approximately 90 degrees relative to the longitudinal axis L-L so that the hole is orthogonal with respect to the longitudinal axis L-L. The orientations of the irrigation holes  67  are typically oriented (usually non-parallel to the longitudinal axis L-L) to ensure sufficient coverage of the electrodes with irrigation flow and therefore each irrigation hole  67  may not have the same orientation as its neighbor. 
     In some embodiments, the holes  67  may include laser or mechanically drilled holes. For example, laser drilled holes may be formed in the biocompatible stretchable material, e.g., in PEBA. In some embodiments, the biocompatible stretchable material, e.g., ePTFE, is a porous material that includes pores forming at least some of the holes  67 . 
     Reference is now made to  FIG.  4    is a cross-sectional view of the catheter  40  of  FIG.  3    along line A:A.  FIG.  4    (inside block A) shows the distal ends of the flexible strips  55  (only two labeled for the sake of simplicity) folded over and connected to a distal connector  75 , which in some embodiments is a tube (e.g., polymer tube) or slug (e.g., polymer slug). The distal end of the stretchable irrigation tube  65  is connected to the distal connector  75 . The distal connector  75  is described in more detail with reference to  FIG.  5   . 
     In some embodiments, the flexible strips  55  may be connected to the distal connector  75  without being folded over so that when the distal end assembly  35  is collapsed the flexible strips  55  are approaching a flat formation along their length. 
       FIG.  4    (inside block B) shows that the proximal ends of the flexible strips  55  are connected to the proximal coupling member  50 . The proximal end of the stretchable irrigation tube  65  is connected to (e.g., stretched over) a proximal connector  77  (for example, a polymer slug). The proximal connector  77  is described in more detail with reference to  FIG.  6   .  FIG.  4    also shows an irrigation line  79  (which extends through the deflectable element  22 , the proximal coupling member  50 , and a slot  83  in the proximal connector  77 ) and a position sensor  81  (e.g., a magnetic position sensor). 
     Reference is now made to  FIG.  5    is a more detailed cross-sectional view of the catheter  40  inside block A of  FIG.  4   . The distal end of the stretchable irrigation tube  65  is connected to the distal connector  75 . The flexible strips  55  are secured between the stretchable irrigation tube  65  and a distal securing ring  85 . An adhesive or epoxy layer  86  is disposed between the distal securing ring  85  and the flexible strips  55  thereby securing the securing ring  85  to the flexible strips  55 . The stretchable irrigation tube  65  and the flexible strips  55  may be secured using pressure and/or any suitable adhesive. The distal connector  75  and the distal securing ring  85  may be formed from any suitable material, for example, but not limited to polycarbonate with or without glass filler, PEEK with or without glass filler, or PEI with or without glass filler. The distal connector  75  also functions as a slug to plug the distal end of the stretchable irrigation tube  65 . 
     Reference is now made to  FIG.  6    is a more detailed cross-sectional view of the catheter  40  inside block B of  FIG.  4   . 
       FIG.  6    shows the proximal connector  77  with the slot  83 . The slot  83  allows the irrigation line  79 - 3  and electrical wires (e.g., for connection to one or more electrodes and/or sensors) to traverse the proximal connector  77 . The irrigation line  79 - 2  connects to the irrigation line  79 - 3 , which is narrower so that it fits in the slot  83 . The stretchable irrigation tube  65  is connected to the proximal connector  77  and is shown as being stretched over the proximal connector  77 . The stretchable irrigation tube  65  may be connected to the proximal connector  77  using any suitable connection method. A proximal securing ring  87  is disposed around the stretchable irrigation tube  65  to aid securing the stretchable irrigation tube  65  to the proximal connector  77 . The stretchable tube  65  in  FIG.  6    is shown partially in an “unstretched” configuration, meaning that the tube  65  is not being elongated along the longitudinal axis L-L ( FIG.  7 B ). Irrigation holes  67  are preferably in the form of a generally circular opening of a diameter of approximately 0.165 mm in the unstretched configuration of tube  65 . 
     The proximal end of the flexible strips  55  are secured between the proximal coupling member  50  and the position sensor  81  and the irrigation line  79 - 2 . Another securing ring  89  is secured over the proximal coupling member  50  to aid securing of the flexible strips  55  to the proximal coupling member  50 . The flexible strips  55  may be secured to the proximal coupling member  50  using pressure and/or any suitable adhesive. 
     The proximal connector  77 , the proximal securing ring  87 , and the securing ring  89  may be formed from any suitable material, for example, but not limited to polycarbonate with or without glass filler, PEEK with or without glass filler, or PEI with or without glass filler. 
     Reference is now made to  FIGS.  7 A and  7 B .  FIG.  7 A  is a schematic view of a catheter  100  in a collapsed form constructed and operative in accordance with an alternative embodiment of the present invention.  FIG.  7 B  is a schematic view of the catheter  100  of  FIG.  7 A  in a deployed and expanded form having a larger outer profile than the collapsed form of catheter  100 . In the collapsed configuration of the basket catheter  100 , tube  65  is in a “stretched” configuration (designated as elongated tube  65 ′) that elongates tube by about 80% of the original unstretched length of tube  65  to arrive at the elongated tube  65 ′ being longer than the unstretched length of tube  65 . In this configuration, it can be seen in the inset of  FIG.  7 A  of the elongated tube  65 ′ causes the circular irrigation holes  67  (of  FIG.  6   ) to take on a slot like (i.e., rounded rectangular) perimeter  67 ′ of approximately 0.15 mm by 0.5 mm (e.g., opening  67 ′ is approximately 250% increase in area of the original opening  67 ) due to the elongation of tube  65 ′. In the expanded configuration of basket  100  shown in  FIG.  7 B , the tube  65  is not being stretched along longitudinal axis L-L as shown by the inset schematic representation of tube  65 . In the unstretched tube configuration  65  for  FIG.  7 B , the irrigation holes  65  approximates a circular opening to allow irrigation fluid to flow through. In one embodiment, the unstretched length of tube  65  is approximately 6 mm and the elongated length  65 ′ (of the original tube  65 ) is approximately 11 mm. 
     The catheter  100  is substantially the same as the catheter  40  of  FIGS.  1 - 6    apart from the following differences. The relaxed state of the distal end assembly  35  of the catheter  100  is the collapsed form of the distal end assembly  35  shown in  FIG.  7 A , which relaxed state of the basket  100  causes the stretching or elongation of the stretchable tube  65 ′. The relaxed state may be configured by using a resilient material, for example, PEI or a shape-memory alloy such as Nitinol. 
     The catheter  100  includes a puller element  102  (e.g., a puller wire) disposed inside the deflectable element  22  and the stretchable irrigation tube  65 , and connected to the distal portion  61  of the distal end assembly  35 . The puller element  102  may be formed from any suitable material, for example, stainless steel, nitinol, and/or ultra-high-molecular-weight polyethylene (UHMWPE). The puller element  102  may have any suitable outer diameter, for example, in the range of 0.05 mm to 0.5 mm, e.g., 0.175 mm. In some embodiments the puller element  102  is connected to the distal connector  75 . The puller element  102  is configured when pulled to expand the distal end assembly  35  from the collapsed form (shown in  FIG.  7 A ) to the expanded deployed form (shown in  FIG.  7 B ). The puller element  102  may be connected to the manipulator  32  ( FIG.  1   ), which controls the puller element  102  to deploy the assembly  35  and change an ellipticity of the assembly  35  according to the longitudinal displacement of the puller element  102  with respect to the deflectable element  22 . 
     As used herein, the terms “about” or “approximately” for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein. More specifically, “about” or “approximately” may refer to the range of values ±20% of the recited value, e.g. “about 90%” may refer to the range of values from 72% to 108%. 
     Various features of the invention which are, for clarity, described in the contexts of separate embodiments may also be provided in combination in a single embodiment. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment may also be provided separately or in any suitable sub-combination. 
     The embodiments described above are cited by way of example, and the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the invention includes both combinations and sub-combinations 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.