Abstract:
A medical device including a catheter and a telescoping mandrel with a tip electrode extending therethrough, the telescoping mandrel being moveable relative to the catheter shaft to extend from the catheter shaft distal end, thereby positioning the tip electrode at a distance from the catheter shaft distal end.

Description:
FIELD OF THE INVENTION  
         [0001]    This invention relates to medical devices for performing diagnostic, mapping, ablation, and other procedures and, more particularly, to a medical device including a telescoping tip electrode.  
         BACKGROUND OF THE INVENTION  
         [0002]    Catheters are often used in medical procedures to provide physical access to remote locations within a patient via relatively small passageways, reducing the need for traditional invasive surgery. The catheter tube also can be inserted into an artery or other passageway through a relatively small incision in the patient&#39;s body, and threaded through the patient&#39;s system of blood vessels to reach the desired target.  
           [0003]    Various types of catheters are used in various procedures, both diagnostic and therapeutic. One general type of catheter used for both diagnostic and therapeutic applications is a cardiac electrode catheter. The diagnostic uses for a cardiac electrode catheter include recording and mapping of the electrical signals generated in the course of normal (or abnormal) heart function. Therapeutic applications include pacing, or generating and placing the appropriate electrical signals in order to stimulate the patient&#39;s heart to beat in a specified manner, and ablation. In an ablation procedure, electrical or radio-frequency energy is applied through an electrode catheter to form lesions in a desired portion of the patient&#39;s heart, for example the right atrium. When properly made, such lesions alter the conductive characteristics of portions of the patient&#39;s heart, thereby controlling the symptoms of arrhythmias, such as supra-ventricular tachycardia, ventricular tachycardia, atrial flutter, atrial fibrillation, and other arrhythmias.  
           [0004]    Such cardiac electrode catheters are typically placed within a desired portion of the patient&#39;s heart or arterial system by making a small incision in the patient&#39;s body at a location where a suitable artery or vein is relatively close to the patient&#39;s skin. The catheter is inserted through the incision into the artery and manipulated into position by threading it through a sequence of arteries, which may include branches, turns and other obstructions.  
           [0005]    Once the cardiac electrode catheter has been maneuvered into the region of interest, one or more electrodes at the distal end of the catheter are placed against the anatomical feature or area sought to be diagnosed or treated. This can be a difficult procedure. The electrophysiologist manipulating the catheter typically can only do so by operating a system of controls at the proximal end of the catheter shaft. The catheter can be advanced and withdrawn longitudinally by pushing and pulling on the catheter shaft, and can be rotated about its axis by rotating a control at the proximal end. Both of these operations are rendered even more difficult by the likelihood that the catheter must be threaded through an extremely tortuous path to reach the target area. To facilitate maneuvering through tight and sinuous sequences of arterial or venous passageways, catheters have been developed with a predetermined portion of their distal ends having pre-shaped curves or dynamically alterably curves. However, the length of the distal end subject to curvature is fixed. As a result, a family of related catheters are developed with the primary difference between each family being the length of the curvable distal end. Variations in the length of the curvable distal ends provide variations in the curve radus. The range of radius is usually defined by the intended anatomical location and patient-to-patient variation. In order to change the curve radius during a procedure, a new member of the catheter family must be used. As a result, the electrophysiologist using the catheter may be required to make an alternative choice during the procedure if the originally selected fixed curve radius device is inappropriate to reach the desired location. This increases the length of the procedure and thereby the risk to the patient. Accordingly, there is a need for improving the navigation of the catheter to the treatment site by avoiding switching catheter devices in order to obtain a different curve radius.  
           [0006]    Finally, once the tip of the catheter has reached the target area, the electrodes at the distal end of the catheter are placed in proximity to the anatomical feature, and diagnosis or treatment can begin. At this point, the electrophysiologist faces another difficultly of establishing and maintaining good contact with the treatment site tissue because only the most distal point of the electrode is likely to make contact with the tissue. Therefore, there is a need to improve the contact that a distal tip electrode makes with the treatment site.  
           [0007]    Another use for electrode tip catheters is to produce linear-type lesions. Where the electrode is fixed to the end of a catheter, the manner of producing a linear-type lesion is to drag the catheter either proximally or distally from the original treatment site in order to produce a linear lesion. However, due to the unpredictable anatomy at the treatment site and along the passageway to which the remainder of the catheter is exposed, a linear lesion can be prevented because of unpredictable movement of the catheter distal end. In addition, to create a continuous lesion, the clinician must be careful not to move the catheter too far between successive ablations. If the clinician should accidentally move the catheter too far, then the lesion created will not be continuous, and the aberrant pathway may not be destroyed, requiring that the patient undergo yet another procedure, which is inefficient and undesirable. Accordingly, it is apparent that there continues to be a need for a device for performing ablations which ensures the creation of accurate linear lesions.  
         SUMMARY OF EMBODIMENTS OF THE INVENTION  
         [0008]    It is an object of an embodiment of this invention to improve the maneuverability of catheters through the tortuous arterial or venous passageways to a treatment site by providing a telescoping tip electrode which can protrude or extend from, or in an alternative, retract into a stabilized main catheter.  
           [0009]    It is an object of an embodiment of this invention to provide that the mandrel on which the telescoping tip is attached and which extends from and retracts to the main catheter body is flexible. As a result, if the mandrel is extended during delivery of the telescoping tip electrode catheter to the treatment site, the flexibility of the mandrel can assist in maneuvering the passageways. In an alternative embodiment, the mandrel on which the telescoping tip is mounted need not be flexible, but rather can be inflexible.  
           [0010]    It is a further object of this invention to improve tissue contact based on the telescoping tip electrode in combination with the telescoping tip portion on which the tip is mounted being made of flexible material and a portion of the catheter proximal of the telescoping tip portion being steerable. Therefore, when the telescoping tip is extended at any distance from the catheter main body and the steerable portion is manipulated to form a curve, the curve portion applies downward pressure to the extended electrode, thereby causing the extended electrode to flex downward against the cardiac tissue to order to improve contact of the electrode with the treatment site. In an alternative embodiment, the catheter main body proximal of the telescoping portion can be a preformed curve, which applies pressure to the telescoping tip when extended from the main catheter body and applied to the tissue.  
           [0011]    It is another object of this invention to provide a linear-type lesion based on a predictable linear path of the tip electrode during extension from and retraction into the main catheter body. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    Other objects and feature of the present invention will become apparent from the following detailed description of the preferred embodiment considered in conjunction with the accompanying drawings. It is understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention.  
         [0013]    [0013]FIGS. 1A to  1 C are three perspective views of a portion of a telescoping tip electrode catheter with a steerable portion of the main catheter body just proximal of the telescoping tip portion according to an embodiment of the present invention;  
         [0014]    [0014]FIG. 2 is a side view of the handle portion and the distal portion including the telescoping tip electrode and steerable portion of the catheter main body according to the FIGS. 1A to  1 C embodiments;  
         [0015]    [0015]FIG. 3 is an exploded perspective view of the telescoping tip electrode according to the FIGS. 1A to  1 C embodiments;  
         [0016]    [0016]FIG. 4 is a first partial cross sectional view of the telescoping tip electrode according to the FIGS. 1A to  1 C embodiments;  
         [0017]    [0017]FIG. 5 is a second partial cross sectional view of the telescoping tip electrode according to the FIGS. 1A to  1 C embodiments;  
         [0018]    [0018]FIG. 6 is a side view of the telescoping tip portion including the mandrel on which the telescoping tip electrode is mounted and the portion of the catheter main body just proximal of the telescoping tip portion according to the FIGS. 1A to  1 C embodiments;  
         [0019]    [0019]FIG. 7 is a partial cross section of the proximal portion of the main catheter body according to the FIGS. 1A to  1 C embodiments;  
         [0020]    [0020]FIG. 8 is a partial cross section of the telescoping tip electrode catheter showing the steering cables for the steerable catheter portion according to the FIGS. 1A to  1 C embodiments;  
         [0021]    [0021]FIG. 9 is a partial cross section of the telescoping tip electrode catheter showing the steering cables and the steerable catheter portion engaged in a curve according to the FIGS. 1A to  1 C embodiments; and  
         [0022]    [0022]FIG. 10 is a perspective view of the telescoping tip electrode catheter with the steerable portion engaged in a curve and the telescoping tip contacting a treatment site according to the FIGS. 1A to  1 C embodiments. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0023]    [0023]FIGS. 1A to  1 C are three perspective views  10 A,  10 B and  10 C, respectively, of a portion of a telescoping tip electrode catheter  11  with a steerable portion  14  of the main catheter body  16  just proximal of the telescoping tip portion  18  according to an embodiment of the present invention. More particularly, FIG. 1A shows the catheter  12  including a main body portion  16  and a telescoping tip portion  18 . The telescoping tip portion of this FIG. 1A also shows the tip electrode  20 . FIG. 1B shows the steerable portion  14  of the main catheter body  16  just proximal of the telescoping tip portion  18 . The portion  18  includes a partially extended mandrel  22  which extends from and retracts to the main catheter body  16  and to which the telescoping tip electrode  20  attaches. FIG. 1C shows the steerable portion  14  engaged in a curve with a greater degree of curvature than the catheter portion  10 B and the mandrel  22  extended to a greater length than the mandrel  22  in the catheter portion  10 B. In alternative embodiments of the present invention, the tip electrode  22  can be retracted inside the catheter main body  16  rather than being external to the catheter main body  16  when the mandrel  22  is retracted to its full extent.  
         [0024]    [0024]FIG. 2 is a side view of the handle portion  30  and the distal portion of the catheter main body  16  including the telescoping tip electrode  20  and the steerable portion  14  of the catheter main body  16  according to the FIGS. 1A to  1 C embodiments. The handle portion  30  includes a slider mechanism  32  which operates the telescoping tip  18 . The mechanism  32  moves in increments along the longitudinal axis of the catheter  10  and is connected in the interior (not shown) of the catheter  10  to the mandrel  22  for the telescoping tip  20 . Movement of the slider mechanism  32  in either direction similarly causes the mandrel  22  to move in the same direction in order to extend or retract the tip electrode  20 . For example, movement of the slider mechanism  32  proximally causes the mandrel  22  and the tip electrode  20  to retract and movement of the slider mechanism  32  distally causes the mandrel  22  and the tip electrode  20  to extend. The mechanism  32  can also be manipulated to cause partial movement of the mandrel  22  and tip electrode  20  so that partial extension at varying lengths of the tip electrode  20  can be achieved. A slider mechanism which can be used for an embodiment of the present invention is also disclosed in U.S. Pat. No. 6,178,354, to Charles Gibson arid issued on Jan. 23, 2001, which is incorporated herein in its entirety by reference. The handle portion  30  also includes a thumbwheel  34  which operates the steerable portion  14  of the catheter main body. The thumbwheel  34  and operation of the steerable portion  14  is described in U.S. Pat. No. 5,611,777, to Bowden et al. and issued on Mar. 18, 1997, which is incorporated herein in its entirety by reference. The handle portion  30  also connects to a generator device  36  which is proximal of the portion  30 . The generator device portion  36  is used in a conventional manner to connect to a wire which carries power to the tip electrode  20 . Such device  36  and operation is well known to those of ordinary skill in the art and therefore will not be further described herein.  
         [0025]    [0025]FIG. 3 is an exploded perspective view of the telescoping tip electrode  20  according to the FIGS. 1A to  1 C embodiments. In this embodiment, a bipolar electrode  20  is used, including three interlocking portions  38 ,  40  and  42 . Portions  38  and  42  provide an elliptical shape to the electrode  20  and are the conducting portions. Portion  40  can be an electrical insulation. Exemplary materials for the construction of the electrode  2  are platinum, platinum/iridium or gold, etc. An exemplary size of the electrode  20  is 9 French with a length which can vary between about 4 to 8 mm. In alternative embodiments, the electrode  20  size can be smaller than the outer diameter of the main catheter body  16  so that the electrode  20  can retract inside the catheter  10 . In further alternative embodiments, the electrode  20  can be a split electrode or any other type of shape (e.g., square, rectangular or circular) electrode  20  operable to treat tissue in a cardiac or arterial passageway.  
         [0026]    [0026]FIG. 4 is a first partial cross sectional view of the telescoping tip electrode  20  according to the FIGS. 1A to  1 C embodiments. The electrode  20  includes conductors  44  and  46  which provide power to the portions  38  and  42 . Conductors  44  and  46  extend through the mandrel  22  to the generator device  36  (shown in FIG. 2). Also shown is a soldering bonding junction  48  between the electrode  20  and the mandrel  22 .  
         [0027]    [0027]FIG. 5 is a second partial cross sectional view of the telescoping tip electrode  22  according to the FIGS. 1A to  1 C embodiments. Shown are a temperature sensor  50  and circumferential grove  52  around the electrode  20  for sensor placement. The soldering junction  48  is also shown between the electrode  20  and the mandrel  22 . Referring also to FIGS. 1C and 2, an exemplary material for the mandrel  22  is nitinol, MP35N and SST. In alternative embodiments, where the mandrel  22  is not the electrical conductor, the material choices can be expanded to include non-conductive plastics that are durable but flexible, such as polyimide, PEEK or nylon, etc. In one embodiment, the length of the mandrel  22  and telescoping tip  20  portion  18  which extends or retracts from the main catheter body  16  can range in length from greater than 0 cm to about 6 cm or more in length. The diameter of the mandrel  22  can be 7 French for example. In alternative embodiments, the mandrel  22  diameter can be just smaller than the inner diameter of the main catheter body  16  shaft.  
         [0028]    [0028]FIG. 6 is a side view of the telescoping tip portion  18  including the mandrel  22  on which the telescoping tip electrode  20  is mounted (not shown) and the portion of the catheter main body  16  just proximal of the telescoping tip portion  18  according to the FIGS. 1A to  1 C embodiments. The portion of the main catheter body  16  includes a bonding area  60  in which the mechanisms to add in the steerability of the catheter  10  reside. Also shown in this embodiment is a ring electrode  62  for use in bipolar recordings, as is conventional. FIG. 7 is a partial cross section of the proximal portion of the main catheter body  16  according to the FIGS. 1A to  1 C embodiments which shows the bonding area  60  in more detail. More particularly, the area  60  includes a steering anchor  64  and a threaded core assembly  66  for use in controlling the steerable portion  14  of the main catheter body  16 .  
         [0029]    [0029]FIG. 8 is a partial cross section of the telescoping tip electrode catheter  10  showing the steering cables  70  and  72  for the steerable catheter portion  14 . In this embodiment, the steerable portion  14  is located proximal of the distal end of the main catheter body  16 . However, in alternative embodiments, the steerable portion  14  can extend to the distal end of the catheter main body  16 . Curve directional arrows  74  show the potential direction of curvature for the steerable portion  14  in this embodiment. Also shown is mandrel  22  extending through the main catheter body  16  to connect to the slider mechanism  32 , as described in U.S. Pat. No. 6,178,354, as cited above.  
         [0030]    [0030]FIG. 9 is a partial cross section of the telescoping tip electrode catheter  10  showing the steering cables  70  and  72  and the steerable catheter portion  14  engaged in a curve  76  according to the FIGS. 1A to  1 C embodiments.  
         [0031]    [0031]FIG. 10 is a perspective view of the telescoping tip electrode catheter  10  with the steerable portion  14  engaged in a curve and the telescoping tip  20  being extended and contacting a treatment site  78  according to the FIGS. 1A to  1 C embodiments. As a result of the curvature in the steerable portion  14 , additional pressure is applied to the electrode  20  to improve the contact between the electrode  20  and the treatment site  78 .