Abstract:
Embodiments of a guide and flexible sleeve for use with catheters for ablation or other medical procedures are disclosed. An exemplary catheter comprises a guide element having a proximal end and a distal end, the distal end configurable in a desired shape. A flexible sleeve is conformable to the guide element so that the flexible sleeve slides over the guide element, the flexible sleeve has a proximal end and a distal end. A controller couples to the flexible sleeve. The controller operates to move the flexible sleeve at least part way between the distal end of the guide element and the proximal end of the guide element. At least one ablation element disposed at the distal end of the flexible sleeve operates to form a substantially continuous ablative lesion when the flexible sleeve is in contact with a contiguous volume of target tissue.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    a. Field of the Invention 
         [0002]    This invention relates generally to medical instruments, and, more specifically, to a guide and flexible sleeve for use with catheters for ablation or other medical procedures. 
         [0003]    b. Background Art 
         [0004]    Catheters are flexible, tubular devices that are widely used by physicians performing medical procedures to gain access into interior regions of the body. Careful and precise positioning of the catheters within the body is important to successfully completing such medical procedures. It is well known that benefits can be and/or are gained by using catheters to form lesions in tissue if the depth and location of the lesions being formed can be controlled. For example, it can be desirable to elevate tissue temperature to around 50° C. until lesions are formed via coagulation necrosis, which changes the electrical properties of the tissue. Lesions can be and/or are formed at specific locations in cardiac tissue via coagulation necrosis to lessen or eliminate undesirable atrial fibrillation. 
         [0005]    Several difficulties can be and/or are encountered, however, when attempting to form lesions at specific locations using some existing ablation electrodes. One such difficulty encountered with existing ablation catheters is how to locate the tissue and maintain catheter contact with the tissue at the desired location during the procedure. These assessments are not readily determined using conventional fluoroscopy techniques. Instead, the physician locates and maintains contact between the catheter and the tissue based on his/her experience using the catheter. Such experience only comes with time, and can be and/or are quickly lost if the physician does not use the catheter on a regular basis. In addition, when forming lesions in a heart, the beating of the heart further complicates matters, making it difficult to maintain sufficient contact pressure in a fixed location between the catheter and the tissue for a sufficient length of time to form a desired lesion. If the contact between the catheter and the tissue cannot be properly maintained, a quality lesion is unlikely to be created. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    It is desirable to be able to maintain contact and create desired lesions in tissue, including in a moving surface (e.g., the heart wall). In various embodiments, a guide and flexible sleeve for use with catheters for ablation or other medical procedures are disclosed. The guide can be and/or is preformed (i.e., prior to the procedure) to a desired shape (e.g., a circular shape). Once positioned adjacent a tissue to be ablated, one or more ablation element can be and/or are activated and the flexible sleeve can be and/or is retracted from a distal end of the guide to form a lesion substantially conforming to the shape of the guide that is in contact with the tissue. The catheters disclosed herein can be and/or are used to make spot or linear lesions along the length of the guide according to the shape of the guide. 
         [0007]    In an exemplary embodiment, a catheter can comprise a guide element having a proximal end and a distal end, the distal end configurable in a desired shape. A flexible sleeve is conformable to the guide element so that the flexible sleeve slides over the guide element, the flexible sleeve has a proximal end and a distal end. A controller is attached to the flexible sleeve. The controller is operable to move the flexible sleeve at least part way between the distal end of the guide element and the proximal end of the guide element. At least one ablation element is provided at the distal end of the flexible sleeve. The at least one ablation element is operable to form an ablative lesion when the flexible sleeve is in contact with a target tissue. 
         [0008]    In another exemplary embodiment, a catheter comprises a unitary flexible tubing having a proximal end and a distal end defining substantially an entire length of the catheter. A guide element is provided having a proximal end and a distal end, the distal end preformed in a desired shape. A flexible sleeve is conformable to the guide element so that the flexible sleeve slides over the guide element, the flexible sleeve having a proximal end and a distal end, the combination guide element and flexible sleeve insertable through the unitary flexible tubing. A controller is attached to the flexible sleeve and extending through the unitary flexible tubing for operation outside of a patient&#39;s body, the controller operable to affect travel of the flexible sleeve over the guide element in two directions. At least one ablation element is provided at the distal end of the flexible sleeve, the at least one ablation element operable to form an ablative lesion when the flexible sleeve is in contact with a target tissue. 
         [0009]    In yet another exemplary embodiment, a catheter comprises a flexible tubing defining substantially an entire length of the catheter. Guide means is provided having a proximal end and a distal end, the distal end preformed in a desired shape. A flexible sleeve is conformable to the guide means so that the flexible sleeve slides over the guide means, the flexible sleeve having a proximal end and a distal end, the guide means and flexible sleeve insertable through the flexible tubing for positioning adjacent a tissue. Control means is attached to the flexible sleeve and extending through the flexible tubing for operation outside of a patient&#39;s body to move the flexible sleeve back and forth over the guide means. Ablation means is provided at the distal end of the flexible sleeve, the ablation means operable to form an ablative lesion when the flexible sleeve is in contact with a target tissue. 
         [0010]    In still further embodiments, the guide element is a guide wire and/or a mapping catheter. The guide element can be and/or are preformed in the desired shape. The desired shape of the guide cancan be and/or are, e.g., circular. A collar can be and/or are provided on the distal end of the guide element, the collar stopping travel of the flexible sleeve when the flexible sleeve comes into contact with the collar. The guide element can include an irrigation conduit with at least one irrigation port. 
         [0011]    In still further embodiments, the flexible sleeve is positioned at the distal end of the guide element initially during an ablation procedure, and the guide element is retracted toward the proximal end of the guide element during the ablation procedure, wherein retrograde motion creates a lesion on the tissue substantially conforming to the desired shape of the guide element. The flexible sleeve can include an insulated portion and an active portion. The insulated portion is provided over a conducting portion. The conducting portion is electrically connected to the active portion, the conducting portion delivering electrical energy to the active portion, and the active portion is the ablation element. 
         [0012]    In other embodiments, the ablative element includes at least one electrode mounted to an outer surface of the flexible portion. At least one sensor can be and/or are mounted to an outer surface of the flexible portion. For example, the sensor can be and/or are a thermistor, thermocouple, a mapping sensor, or a contact sensor. 
         [0013]    Still other features of a guide for catheters are disclosed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  illustrates a first exemplary catheter. 
           [0015]      FIG. 2  is a magnified view of a distal end portion of the catheter shown in  FIG. 1 . 
           [0016]      FIGS. 3   a - d  show the tip assembly  14  as it can be and/or are moved over the guide element. 
           [0017]      FIG. 4  shows another embodiment of the tip assembly. 
           [0018]      FIG. 5  shows another embodiment of the tip assembly. 
           [0019]      FIG. 6  shows a close up view of another tip assembly  314  which might be implemented with an irrigated catheter. 
           [0020]      FIG. 7  shows another flexible sleeve which can be and/or are implemented with a tip assembly. 
           [0021]      FIG. 8  shows a tip assembly having a guide element and the flexible sleeve from  FIG. 7 . 
           [0022]      FIGS. 9   a - b  shows the flexible sleeve in (a) a fully extended position relative to the guide element; and (b) in a fully retracted position relative to the guide element. 
           [0023]      FIGS. 10   a - e  shows the tip assembly from  FIG. 8  and illustrates how the flexible sleeve can be and/or are moved over the guide element. 
           [0024]      FIG. 11  shows another tip assembly having a generally linear configuration. 
           [0025]      FIG. 12  shows another tip assembly having a generally flattened semi-circular configuration. 
           [0026]      FIGS. 13   a - b  show another tip assembly having a guide wire guide element and a flexible sleeve, wherein (a) shows the flexible sleeve a fully extended position relative to the guide element; and (b) in a fully retracted position relative to the guide element. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    Exemplary embodiments of a guide and flexible sleeve for use with catheters for ablation or other medical procedures, along with methods for creating ablative lesions, are depicted in the figures. Exemplary systems comprise a catheter which can be and/or are inserted into the patient, e.g., an ablation catheter for forming ablative lesions inside the patient&#39;s heart. During an exemplary ablation procedure, a user (e.g., the patient&#39;s physician or a technician) can insert the catheter into one of the patient&#39;s blood vessels, e.g., through the leg or the patient&#39;s neck. The user, guided by a real-time fluoroscopy imaging device, moves the catheter into the patient&#39;s heart. 
         [0028]    When the catheter reaches the patient&#39;s heart, sensors at the distal portion of the catheter can be and/or are implemented to electrically map the myocardium (i.e., muscular tissue in the heart wall) and locate a target tissue. After locating the target tissue, the user moves the catheter into contact with the target tissue before applying ablative energy to form an ablative lesion or lesions. Implementing the guide having a preformed shape and sliding the flexible sleeve over the guide during the ablation procedure, the user is able to provide the appropriate level of contact at the target area in order to form quality ablative lesions without damaging surrounding tissue in the heart or other tissues or anatomical structures elsewhere in the patient&#39;s body. 
         [0029]    Accordingly, embodiments of the present invention provide a number of advantages, including, for example, the ability to apply a reasonable amount of ablative energy to a target tissue while mitigating tissue contact problems. The invention also facilitates enhanced tissue contact in difficult environments (e.g., during lesion formation on a moving surface inside a beating heart, and adjacent other sensitive tissues or anatomical structures). 
         [0030]      FIG. 1  illustrates one type of an exemplary single-use catheter  10  generally including a flexible tubing  12 , a tip assembly  14 , a Y connector  16 , a luer device  18 , and an electrical connector  20 . The electrical connector  20  establishes electrical connection with a power source (not shown) that operates ablative element(s) and/or sensors at the tip assembly  14  to perform, for example, ablation procedures, mapping or pacing procedures, or to perform other aspects of a medical procedure. 
         [0031]    Although it will become evident that aspects of the exemplary catheter  10  are applicable to a variety of medical procedures and end uses, the invention will be described principally in the context of a specific example of an ablation catheter. Specifically, the catheter  10  as shown in  FIG. 1  is believed to be particularly advantageous as an ablation catheter for creating endocardial lesions during cardiac ablation procedures to treat arrhythmias, and also for cardiac electrophysiological mapping and delivering diagnostic pacing stimuli. However, the invention and the appended claims are not intended to be limited to any specific type of catheter (e.g., steering catheters can also be used), including but not limited to specific examples or embodiments described herein, except when explicitly defined as such in the appended claims. 
         [0032]    The Y-connector  16  separates a fluid tube  22  from electrical lead wires extending between the tip assembly  14  and the electrical connector  20 . That is, the fluid tube  22  and the lead wires forward of the Y-connector  16  pass internally through The tubing  12 , while aft of the Y-connector  16 , the fluid tube  22  and the wire leads are exposed and separated for connection to a fluid source (not shown) and a power source, respectively. The electrical connector  20  can be and/or is a known connector that can be and/or is engaged to a power source or power supply with, for example, plug-in connection. One suitable electrical connector is a  14  pin REDEL® plastic connector commercially available from LEMO of Rohnert Park, Calif., although other connectors from various manufacturers can likewise be utilized. 
         [0033]    The luer device  18  in the depicted embodiment, as known in the art, can be and/or is used to open or close a flow path so that fluid can be and/or is passed through the Y-connector  16  and the tubing  12  to the tip assembly  14  for irrigation purposes. The luer device  18  can be and/or is considered optional for certain procedures. 
         [0034]    The flexible tubing  12  includes a proximal end  24  coupled to the Y-connector  16 , a distal end  26  coupled to the tip assembly  14 , and an axial length extending between the proximal and distal ends  24  and  26 . In general, the flexible tubing  12  can be and/or is fabricated according to known processes, such as extrusion processes. The tubing  12  can be and/or is fabricated from any suitable tubing material known in the art of medical instruments, such as engineered nylon resins and plastics, including but not limited to PEBAX® tubing of Ato Fina Chemicals, France. 
         [0035]    In an exemplary embodiment, the tubing  12  includes a first portion  28  of the tubing  12  between the Y connector and the tip assembly  14 , and a second portion  30  of the tubing  12  including the distal or end portion of the tubing  12  extending to the tip assembly  14 . In an exemplary embodiment, the first portion  28  and the second portion can be and/or are fabricated from different materials, grades of materials, and/or thicknesses of materials for enhanced performance and flexibility of the tubing  12  in use of the catheter assembly  10 , as will be explained in more detail below. It is noted, however, that although the tubing  12  can have different portions or “zones”, the tubing  12  is manufactured as a unitary piece. 
         [0036]    For example, in one embodiment, the first portion  28  of the tubing  12  can include, for example a braided material that is comparatively rigid and kink resistant. The first portion  28  can be and/or is formed with different portions of braided material, semi-soft material, and soft material fused to one another so that the first portion  28  becomes increasingly flexible along the axial length as the tube portion  28  approaches the second portion  30 . The second portion  30  of the tubing  12  can include a soft and flexible material. In the illustrated embodiment, each of the tubing portions  28  and  30  share a common outside diameter of, for example, 7 French, although in other embodiments, the tubing portions  28  and  30  can be and/or are another size. 
         [0037]    Additionally, and as shown in  FIG. 1 , the first portion  28  extends for the vast majority of the axial length of the tubing  12  between the proximal end  24  and distal end  26 . The second portion  30  of the tubing  12  extends for a much shorter length than the first portion  28 . By way of example only, in a specific embodiment the first portion  28  extends for an axial length of about 126.3 cm, the second portion  30  extends for an axial length of about 0.8 cm to 2.2 cm, although other relative lengths of the tube portions can likewise be employed in other embodiments. The different relative lengths of the tube portions  28  and  30 , as well as the different flexible properties of the tube portions  28  and  30 , allows the tip assembly  14  to be more precisely positioned within a patient&#39;s body, while also avoiding problems of kinks and excessive deflection of the tubing  12  along the majority of its length during use and handling. 
         [0038]    Also in exemplary embodiments, the catheter  10  can be constructed to have different flexibilities along the length of tubing  12 , particularly in the distal region. Typically, the distal end  26  (where the tip assembly  14  is located) is desired to be the most flexible. The proximal end  28  is desired to have less flexibility. Still additional portions can be and/or are provided, with the proximal portions having less and less flexibility. 
         [0039]    The flexibility can be determined by material properties and/or thickness. Thus, the tubing  12  can be made to have varying material properties along its length toward the distal end, so that the different portions will have different flexibilities. The shaft can also decrease in thickness toward the distal end  26 . A thinner wall of the tubing  12  results in greater flexibility, while a thicker wall of the tubing  12  results in less flexibility. Flexibility can change either continuously/gradually or in abrupt steps. 
         [0040]    The unitary construction of the flexible tubing of the catheter  10  is believed to provide manufacturing benefits, and also performance benefits, in relation to conventional, and more complicated, catheter constructions for use with stereotactic systems. The catheter  10  can be manufactured without joints, ensuring high reliability and safety of the catheter  10 . The unitary tubing is easier to manufacture, and takes less time to manufacture. Eliminating junctions in the shaft also reduces or altogether eliminates undesirable stiffness. The unitary flexible tubing can extend along substantially the entire length of the catheter body, and can have a distal end to be coupled to the tip assembly  14  and a proximal end to be coupled to a handle (not shown). Alternatively, the unitary flexible tubing can extend along a portion of the catheter body, but can be and/or is attached to additional components to form the entire length of the catheter body. For example, the unitary flexible tubing with no fused connections can be and/or is fused with another flexible tubing to form the entire length of the catheter body. 
         [0041]    In operation, the distal end of the catheter  10  including the tip assembly  14  is navigated to the site in the body where a medical procedure, such as an atrial mapping, pacing and ablation are to occur. The distal end can extend, for example, into a heart chamber of a patient. Once the distal end is in the chamber, imaging techniques can be and/or are utilized to precisely position the tip assembly  14  for performance of the procedure at a specific location, as will be described in more detail below. 
         [0042]    It is noted that other components typical of systems which are conventionally implemented for tissue ablation or for other therapeutic procedures implemented via catheters (e.g., delivery of a drug or therapeutic agent) are not shown or described herein for purposes of brevity. Such components can nevertheless also be provided as part of, or for use with, the catheter  10 . For example, these systems commonly include or are used in conjunction with an ECG recording system, and/or various controls for performing the ablation procedure. Such components are well understood in the medical devices arts and therefore further explanation is not necessary for a complete understanding of the invention. 
         [0043]      FIG. 2  is a magnified view of a tip assembly  14  of the catheter  10  shown in  FIG. 1 . The tip assembly  14  can be and/or is coupled to the tube portion  12  at one end and provide through a sheath (not shown) for insertion through the patient&#39;s body. 
         [0044]    The tip assembly  14  can include a guide element  32  having a proximal end  34  and a distal end  36 . The length of the guide element  32  extending between the proximal end  34  and the distal end  36  of the tip assembly  14  can be and/or is configurable in a desired shape. For example, guide element  32  can be and/or is a guide wire which is formed in a helical, circular shape, as shown in  FIG. 2 . Of course any suitable shape can be and/or is employed (e.g., semi-circular, oval, rectangular, triangular, etc.). 
         [0045]    The tip assembly  14  can also include a flexible sleeve  38  having a proximal end  40  and a distal end  42 . The flexible sleeve  38  is made of a material which enables the flexible sleeve  38  to conform to the shape of the guide element  32  so that the flexible sleeve  38  can be slid over the guide element  32 . In an exemplary embodiment, the flexible sleeve  38  is made of a biologically compatible plastic or polymer material. Alternatively, the flexible sleeve  38  can be and/or is made of any material and provided with a suitable coating (e.g., Teflon® coating). 
         [0046]    The tip assembly  14  is particularly suited for ablation procedures wherein radio frequency waves are delivered at the site of an abnormal pathway in the body. Radiofrequency (RF) energy can therefore be coupled to biological tissue surrounding the catheter tip. Ablation procedures are typically used, for example, within the interior chambers of the heart to thermally ablate cardiac tissue. 
         [0047]    In this regard, the flexible sleeve  38  can include at least one ablation element  44  near the distal end  42  of the flexible sleeve  38 . The ablation element  44  can be and/or is energized for an ablation procedure, as is well known in the medical devices arts, for example, using RF energy. Accordingly, the ablation element  44  is operable to form an ablative lesion when the ablation element  44  on the flexible sleeve  38  are in contact with a target tissue. 
         [0048]    In an exemplary embodiment, the ablation element  44  includes one or more electrodes. In  FIG. 2 , three ring electrodes  46   a - c  are shown. However, any suitable number and/or type of electrodes can be and/or are provided, and will depend at least to some extent on design considerations and the intended end-use. The electrodes  46   a - c  are spaced from one another by dielectric materials as is known in the art. In one example, the electrodes  46   a - c  can be and/or are 8 Fr electrodes that are, for example, 2 mm in height. The electrodes  46   a - c  can be and/or are fabricated from 90% platinum and 10% iridium, or other materials known in the art. The electrodes  46   a - c  can be and/or are visually recognizable under fluoroscopic exposure. While each electrode  46   a - c  is formed as an integral unit, the individual electrodes  46   a - c  can include multiple electrode elements. The electrodes  46   a - c  can additionally be operated to record intracardiac signals and to provide pacing signals. 
         [0049]    A controller  48  can be and/or is operatively associated with the tip assembly. In an exemplary embodiment, the controller  48  can include one or more pull wires  50   a - b  attached to the flexible sleeve  38  and extending through the tubing  12  of the catheter  10  (shown in  FIG. 1 ) and out the electrical connector  20  near the handle  16  of the catheter  10 , so that the pull wires  50   a - b  are operable by the user. The pull wires  50   a - b  can further be connected to a lever arm or rotational device (not shown) that is provided on or near the catheter handle to facilitate positioning and operation by the user. Regardless of the specific implementation, operation of the pull wires  50   a - b  by the user enables the flexible sleeve  38  to travel in two directions, as illustrated by the arrows shown in  FIGS. 3   a  and  3   d . This travel moves the flexible sleeve  38  at least part way between the distal end  36  of the guide element  32  and the proximal end  34  of the guide element  32 . Exemplary movement of the flexible sleeve  38  for an ablation procedure can be and/or is better understood with reference to  FIGS. 3   a - d.    
         [0050]      FIGS. 3   a - d  show the tip assembly  14  as it can be and/or is moved over the guide element  32 . In  FIG. 3   a , the flexible sleeve  38  is shown as it can be and/or is moved into a fully extended position. In the fully extended position, the distal end  42  of the flexible sleeve  38  is at the distal end  36  of the guide element  32  (see  FIG. 2 ). During and exemplary procedure, the flexible sleeve  38  is moved to the fully extended position prior to contacting the tissue and beginning the procedure. Once positioned against the tissue in the desired location, the ablative element  44  can be and/or is activated, e.g., by delivering RF energy to the ring electrodes  46   a - c . Once a sufficient lesion has been formed in the fully extended position, the user can gradually retract the flexible sleeve  38 , e.g., by operating the controller  38  to withdraw the flexible sleeve  38  generally in the direction of arrow  48   a  in  FIG. 3   a  so that the flexible sleeve  38  is in a partially retracted position as illustrated in  FIG. 3   b . The user can continue to retract the flexible sleeve  38  (again, by operating the controller  38 ) to withdraw the flexible sleeve  38  generally in the direction of arrow  48   b  in  FIGS. 3   b  and  38   c  in  FIG. 3   c  so that the flexible sleeve  38  continues to retract as illustrated in  FIG. 3   c , until the flexible sleeve  38  is in a fully retracted position, as illustrated in  FIG. 3   d.    
         [0051]    It is noted the operation illustrated in  FIG. 3   a - d  is not intended to illustrate discrete positions of the flexible sleeve  38 , but rather to illustrate general movement from a fully extended position (as shown in  FIG. 3   a ) wherein the distal end  42  of the flexible sleeve  38  is at the distal end  36  of the guide element  32 ; to a fully retracted position (as shown in  FIG. 3   d ) wherein the distal end  42  of the flexible sleeve  38  is at the proximal end  34  of the guide element  32 . It is also noted that this motion can be and/or is a “fluid” or “smooth” motion (e.g., where the user moves the flexible sleeve  38  at a constant velocity); or the motion can be and/or is more segmented (e.g., where the user moves the flexible sleeve  38  to various positions and maintains the flexible sleeve  38  at one or more of these positions for a period of time). Specific operation will depend on the desired end-result, among other considerations for lesion formation. 
         [0052]      FIG. 4  shows another embodiment of the tip assembly  114 . It is noted that 100-series reference numbers are used to refer to like components already described above, and therefore cannot be described again here with reference to  FIG. 4 . 
         [0053]    In this embodiment, the tip assembly  114  also includes a flexible sleeve  138  having an ablation element  144  with ring electrodes  146   a - c . The flexible sleeve  138  conforms to a guide element  132 . However, in this embodiment, the guide element  132  includes a collar  150  at the distal end  136 . The collar  150  can have any suitable configuration, such as an end cap, rounded tip, etc. The collar  150  is provided to stop travel of the flexible sleeve  138  when the flexible sleeve  138  comes into contact with the collar  150 . Accordingly, the flexible sleeve  138  does not overrun the guide element  132 . In addition, the user receives tactile feedback so that the user can know when the flexible sleeve  138  is properly positioned in the fully extended position (e.g., as shown in  FIG. 3   a ). 
         [0054]      FIG. 5  shows another embodiment of the tip assembly  214 . It is noted that 200-series reference numbers are used to refer to like components already described above, and therefore cannot be described again here with reference to  FIG. 5 . 
         [0055]    The tip assembly  214  includes a flexible sleeve  238  having an ablation element  244  with ring electrodes  246   a - c . The flexible sleeve  238  conforms to a guide element  232 . In this embodiment, the guide element  232  includes a guide wire  252  provided with a coating  254 . The guide wire  252  can be and/or is a metal, plastic or polymer which can be and/or is either preformed during manufacture or by the user (e.g., prior to introducing the guide wire into the catheter sheath). The coating  254  can be and/or is any coating suitable for use in a biological system (e.g., Teflon® coating). In addition to blunting the distal end  236 , the coating  254  serves as a barrier and keeps the guide wire  252  from being exposed to the tissue. 
         [0056]      FIG. 6  shows a close up view of another tip assembly  314  which might be implemented with an irrigated catheter. In  FIG. 6 , only the distal end  336  of the guide element  332  is shown. It is noted that 300-series reference numbers are used to refer to like components already described above, and therefore cannot be described again here with reference to  FIG. 6 . 
         [0057]    The tip assembly  314  includes a flexible sleeve  338  having an ablation element  344  with ring electrodes  346   a - c . The flexible sleeve  338  conforms to a guide element  332 . In this embodiment, the guide element  332  includes a lumen  356  formed along the length of the central axis of the guide element  332 . The guide element  332  can be and/or is, for example, a braided polyimide tube that maintains the flow path through the lumen  356  in all orientations of the tip assembly  314 , without compromising the flexibility of the tubing. The distal end  336  of the guide element  332  is fitted with an irrigated collar  358  including one or more irrigation ports  360 . The lumen  356  is in fluid communication with the luer  18  ( FIG. 1 ) on one end and with the irrigation ports  360  of the tip assembly  314  at the other. The distal end  336  of the guide element  332  can be and/or is closed. Or the distal end  336  of the guide element  332  can be and/or is open, thereby forming another fluid port. In any event, an irrigation fluid, such as saline, can be and/or is injected through the tip assembly  314 . Fluid can be and/or is enabled to flow through the catheter  10  and be released at the tissue, e.g., to enhance contact and promote ablative coupling with the tissue, as a cooling fluid, as an ablative fluid, or for any other reason where an irrigated catheter can be and/or is used. 
         [0058]    In addition, the irrigated collar  358  further serves a similar function to that of the collar  50  shown in  FIG. 4 , to prevent the flexible sleeve  338  from passing over the irrigated collar  358 . By stopping the flexible sleeve  338  behind the irrigated collar  358 , the flexible sleeve  338  does not block or otherwise interfere with delivery of the fluid at the fluid ports. 
         [0059]    It is noted that the tip assembly  314  shown in  FIG. 6  is provided only as one example of how the tip assembly might be implemented with an irrigated catheter. Of course other embodiments are also contemplated, for example, having multiple fluid ports along the length of the guide element, different fluid ports at different locations and/or for different types of fluids, and so forth. It is also noted that the tip assembly can be and/or is used with any types of fluid, including but not limited to, cooling fluids and/or therapeutic fluids. 
         [0060]      FIG. 7  shows another flexible sleeve  438  which can be and/or is implemented with a tip assembly.  FIG. 8  shows the tip assembly  414  of the catheter  10  shown in  FIG. 1 , wherein the tip assembly  414  includes the flexible sleeve from  FIG. 7  and a guide element  432 . The tip assembly  414  can be and/or is coupled to the tube portion  12  of the catheter  10  in  FIG. 1  at one end, and provided through a sheath (not shown) for insertion into the patient&#39;s body. 
         [0061]    The tip assembly  414  can include a flexible sleeve  438  having a proximal end  440  and a distal end  442 . The flexible sleeve  438  is made of a material which enables the flexible sleeve  438  to conform to the shape of the guide element  432  so that the flexible sleeve  438  can be slid over the guide element  432 . In an exemplary embodiment, the flexible sleeve  438  is made of a biologically compatible plastic or polymer material. Alternatively, the flexible sleeve  438  can be and/or is made of any material and provided with a suitable coating (e.g., Teflon® coating). 
         [0062]    The guide element  432  ( FIG. 8 ) has a proximal end  434  and a distal end  436 . The length of the guide element  432  extending between the proximal end  434  and the distal end  436  of the tip assembly  414  can be and/or is configurable in a desired shape. In this embodiment, the guide element  432  can be and/or is a mapping catheter  470  which is formed in a helical, circular shape, or in any other suitable shape. The mapping catheter  470  can include one or more sensor electrodes  472 . During use, the mapping catheter  470  can be and/or is inserted adjacent the tissue so that the tissue can be mapped. Following the mapping operation, the flexible sleeve  438  can be and/or is advanced to the distal end of the mapping catheter  470  and operated for the ablation procedure. 
         [0063]    In this regard, the flexible sleeve  438  can include an insulated portion  480  and an active portion  482 . The active portion  482  can extend for a length of about 2 mm up to about 8-10 mm, although other lengths can also be utilized depending on design/use considerations. The insulated portion  480  is provided over a conducting portion  484 . The conducting portion  484  is electrically connected to the active portion  482  on one end, and to wiring or other electrical conductors provided through the lumen of the catheter  10  ( FIG. 1 ) so that the conducting portion  484  delivers electrical energy to the active portion  482  of the flexible sleeve  438 . Accordingly, in this embodiment the active portion  482  is the ablation element  444 . The ablation element  444  can be and/or is energized for an ablation procedure, as is well known in the medical devices arts, for example, using RF energy. Accordingly, the ablation element  444  is operable to form an ablative lesion when the ablation element  444  (i.e., the active portion  482  on the flexible sleeve  438  is in contact with a target tissue. 
         [0064]    It is noted that the active portion  482  can have any suitable configuration, including one or more active areas along the length of the flexible sleeve  438 . In addition, any suitable number and/or type of electrodes and/or other sensors can also be provided, and will depend at least to some extent on design considerations and the intended end-use. 
         [0065]    As already discussed above, a controller can be and/or is operatively associated with the tip assembly  414 . The controller can be and/or is operated similarly to that already described above (e.g., including one or more pull wires), and therefore is not shown and described again with reference to the tip assembly  441 . 
         [0066]      FIGS. 9   a - b  shows the flexible sleeve  438  in (a) a fully extended position relative to the guide element  432 ; and (b) in a fully retracted position relative to the guide element  432 .  FIGS. 10   a - e  illustrates how the flexible sleeve  438  can be and/or is moved over the guide element  432  between the extended position and the retracted position. As mentioned above, the tip assembly  414  can have any suitable shape and/or configuration. For purposes of illustration, in  FIGS. 10   a - e , the tip assembly  414  is shown having a more flattened configuration. 
         [0067]    In  FIG. 10   a , the flexible sleeve  438  is shown as it can be and/or is moved into the fully extended position. In the fully extended position (also shown in  FIG. 9   a ), the distal end  442  of the flexible sleeve  438  is at the distal end  436  of the guide element  432 . During and exemplary procedure, the flexible sleeve  438  is moved to the fully extended position prior to contacting the tissue and beginning the procedure. Once positioned against the tissue in the desired location, the ablative element  444  can be and/or is activated, e.g., by delivering RF energy to the active region. Once a sufficient lesion has been formed in the fully extended position, the user can gradually retract the flexible sleeve  438 , e.g., by operating the controller  438  to withdraw the flexible sleeve  438  generally in the direction of arrows  448   a - c  in  FIG. 10   a - c , respectively, so that the flexible sleeve  438  is in a partially retracted position ( FIGS. 10   b  and  10   c ). The user can continue to retract the flexible sleeve  438  so that the flexible sleeve  438  continues to retract until the flexible sleeve  438  is in a fully retracted position, as illustrated in  FIG. 10   d.    
         [0068]    Again, the operation illustrated in  FIG. 10   a - d  is not intended to illustrate discrete positions of the flexible sleeve  438 , but rather to illustrate general movement from a fully extended position (as shown in  FIG. 10   a ) to a fully retracted position (as shown in  FIG. 10   d ). This motion can be and/or is a “fluid” or “smooth” motion (e.g., where the user moves the flexible sleeve  438  at a constant velocity); or the motion can be and/or is more segmented (e.g., where the user maintains the flexible sleeve  438  at one or more of these positions for a period of time before continuing moving the flexible sleeve  438 ). Specific operation will depend on the desired end-result, among other considerations for lesion formation. 
         [0069]      FIG. 11  shows another tip assembly  514  having a generally linear configuration.  FIG. 12  shows another tip assembly  614  having a generally flattened semi-circular configuration.  FIGS. 13   a - b  show another tip assembly  714  having a guide wire  780  guide element  732  and a flexible sleeve  738 . In  FIGS. 13   a  and  13   b , the flexible sleeve  738  is shown as it can be and/or is advanced through the catheter sheath  712  (see also, sheath  12  in  FIG. 1  for reference).  FIG. 13   a  shows the flexible sleeve  738  a fully extended position relative to the guide element  732 .  FIG. 13   b  shows the flexible sleeve  738  in a fully retracted position relative to the guide element  732 . As already discussed above, the tip assemblies  514 ,  614 , and  714  shown in  FIGS. 11 ,  12 , and  13   a - b  can be and/or is coupled through the sheath  712  (or tube portion  12  of the catheter  10  in  FIG. 1 ) at one end, and provided through the sheath  712  for insertion into the patient&#39;s body. 
         [0070]    The tip assemblies  514 ,  614 , and  714  can include guide elements  532 ,  632 ,  732 , respectively, which can be and/or is configurable in a desired shape. The tip assembly  614  can also include a flexible sleeve  538 ,  638 ,  738 . The flexible sleeve  538 ,  638 ,  738  is made of a material which enables the flexible sleeve  538 ,  638 ,  738  to conform to the shape of the guide element  532 ,  632 ,  732  so that the flexible sleeve  538 ,  638 ,  738  can be slid over the guide element  532 ,  632 ,  732 . 
         [0071]    The tip assembly tip assemblies  514 ,  614 , and  714  are particularly suited for ablation procedures wherein radio frequency waves are delivered at the site of an abnormal pathway in the body. Radiofrequency (RF) energy can therefore be coupled to biological tissue surrounding the catheter tip. Ablation procedures are typically used, for example, within the interior chambers of the heart to thermally ablate cardiac tissue. Accordingly, the flexible sleeves  538 ,  638 ,  738  can comprise an ablation element configured as the active portion, e.g., as already described above with reference with  FIGS. 7 and 8 . 
         [0072]    A controller can be and/or is operatively associated with the tip assemblies  514 ,  614 , and  714 . The controller can be and/or is operated similarly to that already described above (e.g., including one or more pull wires), and therefore is not shown and described again with reference to the tip assemblies  514 ,  614 , and  714 . 
         [0073]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.