Abstract:
A system for guiding a cryocatheter through the vasculature of a patient includes a guidewire positioned in the vasculature across a predetermined site. A connector is attached to the distal end of the cryocatheter and is configured to receive the guidewire. The connector is then placed over the guidewire to guide the cryocatheter through the vasculature along the guidewire to the predetermined site. The tip of the cryocatheter can then be used at the predetermined site to cryoablate the tissue or otherwise remove heat from the predetermined site.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention pertains generally to devices and methods for guiding catheters through the vasculature of a patient. More particularly, the present invention pertains to devices and methods for positioning a catheter tip at a predetermined site in the vasculature of a patient. The present invention is particularly, but not exclusively, useful for positioning the tip of a cardiac cryoablation catheter at a predetermined site in the vasculature for surgical procedures requiring effective heat transfer.  
         BACKGROUND OF THE INVENTION  
         [0002]    Guidance and positioning mechanisms are important considerations in the manufacture and operation of an invasive catheter. Specifically, the ability to easily and accurately guide the catheter through a patient&#39;s vasculature to a target site is an essential catheter characteristic. Once the catheter is near the target site, the ability to then accurately position the catheter tip at the target site is also important.  
           [0003]    Several devices have been previously suggested for the purpose of steering a catheter through the vasculature of a patient. For example, U.S. Pat. No. 1,060,665, which issued to Bell on May 6, 1913 for an invention entitled “Catheter”, incorporates a pre-bent stiffening member located at the catheter&#39;s distal end for use of the member&#39;s bending bias in steering the catheter through the vaculature. Recently, more complex devices have relied on a pull-wire to deflect the catheter tip. In general, these mechanisms have included concentric or eccentric pull-wires that generate an eccentrically applied force on the tip of the catheter. For example, U.S. Pat. No. 4,456,017, which issued to Miles for an invention entitled “Coil Spring Guide with Deflectable Tip,” incorporates a concentric core wire for this purpose. In contrast, U.S. Pat. No. 4,586,923, which issued to Gould et al., uses an eccentric wire for the same purpose. Furthermore, devices have also been proposed which will bias the deflection of a catheter tip in a predetermined plane. An example of such a device is disclosed in U.S. Pat. No. 4,886,067, which issued to Palermo for an invention entitled “Steerable Guidewire with a Soft Adjustable Tip.” In the Palermo patent, such a bias is established by flattening the core wire. Another device that is often used for steering a catheter through the vasculature of a patient involves a guidewire that is pre-positioned in the vasculature across a target site. The catheter is then engaged with the guidewire, and is advanced over the guidewire through the vasculature to the target site.  
           [0004]    At the target site, some surgical applications require that the tip of the catheter be accurately positioned. In particular, for cryoablation procedures, the tip of a cryoablation catheter must be accurately positioned to contact tissue at the target site for cryoablating the tissue. Importantly, a cryoablation catheter has unique structural aspects and thermodynamic properties that must be considered in the design of its guidance and positioning mechanism. Specifically, a cryoablation catheter is typically designed with a closed tip portion that forms an expansion chamber. In operation, a cryogenic fluid is introduced into the expansion chamber through a supply line to rapidly cool the tip portion. Consequently, tissue in contact with the tip portion at the target site is cryoablated. Importantly, whatever guidance mechanism may be used to position the tip portion in the vasculature, it must not interfere with the intended operation of the cryoablation catheter.  
           [0005]    Prior art mechanisms for guiding and positioning a catheter generally have not been designed to accommodate the particular structural aspects required for the catheter&#39;s intended application. Accordingly, they have not specifically considered the requirements for operation of a cryoablation catheter. For instance, existing over-the-wire guiding mechanisms that pass a guidewire through the catheter tip cannot be used with a cryoablation catheter because the required closed tip portion of a cryoablation catheter prevents the guidewire from fully extending through the catheter. In any event, the guidewire must not compromise the expansion chamber or interfere with the flow of cryogenic fluid to and from the expansion chamber.  
           [0006]    In light of the above, it is an object of the present invention to provide a device and method for advancing a catheter through a patient&#39;s vasculature and for positioning the catheter tip at a predetermined site in the patient. Another object of the present invention is to provide a device and method for guiding a cryoablation catheter through a patient&#39;s vasculature without compromising the expansion chamber in the catheter tip. Still another objection of the present invention is to provide a device and method for guiding and positioning a catheter in the vasculature of a patient that is relatively easy to manufacture, is simple to use, and is comparatively cost effective.  
         SUMMARY OF THE INVENTION  
         [0007]    The present invention is directed to a system and method for guiding a cryocatheter through the vasculature of a patient to position the distal end of the cryocatheter at a predetermined site in the vasculature. As intended for the present invention, the system includes a connector that is incorporated with the distal end of the cryocatheter and is formed with a passageway configured to receive a guidewire. The guidewire is pre-positioned in the vasculature of the patient and leads to the predetermined site. When the connector is engaged with the guidewire, the cryocatheter can be advanced along the guidewire and through the vasculature to position the distal end of the cryocatheter at the predetermined site.  
           [0008]    In detail, the cryocatheter includes a catheter and a tip. The catheter has a proximal end and a distal end, and is formed with a wall surrounding a lumen that extends between the proximal and distal ends of the catheter. The tip has a closed distal end and an open proximal end, and is formed with a wall surrounding a chamber. Structurally, the open proximal end of the tip is attached to the distal end of the catheter so that the chamber formed by the tip is in fluid communication with the lumen of the catheter. Preferably, the tip is substantially cylindrical-shaped and defines a longitudinal axis.  
           [0009]    The system of the present invention further includes a tubular-shaped supply line that has a proximal end and a distal end. The supply line is positioned in the lumen of the catheter with its distal end located in the chamber. With this structure, in addition to the supply line, a fluid return lumen is established inside the catheter between the supply line and the inner wall of the catheter. Furthermore, the proximal end of the supply line is connected to a fluid supply, which is in fluid communication with the chamber through the supply line.  
           [0010]    As indicated above, the present invention envisions a connector that is operationally associated with the tip of the catheter. In one embodiment of the present invention, this connector is an eyelet. For this embodiment, the eyelet has an annular shaped member that is formed with a passageway for receiving the guidewire. Additionally, the eyelet has an extension arm with one end attached to the annular shaped member. In one variation of this embodiment, the other end of the extension arm is fixedly attached directly to the tip.  
           [0011]    In a variation of the “eyelet” embodiment for the present invention, the system also includes a post that extends axially from the closed end of the tip in a distal direction. For this embodiment, a ring is formed at the end of the extension arm opposite the annular shaped member and is configured to surround the post. Additionally, a cap is attached to the distal end of the post to hold the ring on the post, to thereby allow the annular shaped member of the connector to rotate (swivel) around the longitudinal axis.  
           [0012]    In still another embodiment of the present invention, the connector is formed into the wall of the tip. Structurally, for this embodiment of the present invention, the connector is a passageway that is formed between the inner and outer surfaces of the tip wall. More specifically, the passageway extends between a first opening and a second opening, which are located on the outer surface of the tip wall. In yet another embodiment of the present invention, the connector is formed into the wall of the catheter. For this embodiment, the connector is a passageway that is formed between the inner and outer surfaces of the catheter wall. The passageway extends between a first opening and a second opening, which are located on the outer surface of the catheter wall. Importantly, in either case, the passageway should not compromise the expansion chamber or reduce the efficacy of the thermodynamic structure of the tip. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which:  
         [0014]    [0014]FIG. 1 is a perspective view of a system according to the present invention positioned in the vasculature of a patient;  
         [0015]    [0015]FIG. 2 is a perspective view of the catheter tip, shown in combination with one type embodiment of the connector, in accordance with the present invention;  
         [0016]    [0016]FIG. 3A is a cross-sectional view of the catheter tip and the connector as seen along the line  3 - 3  in FIG. 2;  
         [0017]    [0017]FIG. 3B is a cross-sectional view of the catheter tip, in combination with an alternate embodiment for the connector, as the combination would be seen along the line  3 - 3  in FIG. 2;  
         [0018]    [0018]FIG. 3C is a cross-sectional view of a catheter tip, in combination with another alternate embodiment for the connector, as this combination would be seen along the line  3 - 3  in FIG. 2; and  
         [0019]    [0019]FIG. 3D is a cross-sectional view of a catheter tip, in combination with yet another alternate embodiment for the connector, as this combination would be seen along the line  3 - 3  in FIG. 2.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    Referring initially to FIG. 1, a catheter system in accordance with the present invention is shown and is generally designated  10 . In FIG. 1, the system  10  of the present invention is shown positioned in the vasculature of a patient  12 . As shown, the system  10  includes a cryocatheter  14  that has a proximal end  16  and a distal end  18 . Also, as shown, the cryocatheter  14  is positioned at a predetermined site  20  in the vasculature of the patient  12 . The system  10  also includes a guidewire  22  that is positioned in the vasculature of the patient  12  and extends past the predetermined site  20 . Furthermore, the catheter system  10  includes a supply line  24  that has a proximal end  26  and a distal end  28 . The supply line  24  is positioned in the cryocatheter  14  with the distal end  28  of the supply line  24  positioned at the distal end  18  of the cryocatheter  14 . The proximal end  26  of the supply line  24  is connected to a fluid source  30 .  
         [0021]    Referring now to FIG. 2, the cryocatheter  14  includes a catheter body  32  that has a proximal end  34  (FIG. 1) and a distal end  36 . The cryocatheter  14  also includes a tip  38  that has an open proximal end  40  and a closed distal end  42 . Preferably, the tip  38  has a substantially cylindrical shape that defines a longitudinal axis  43 . In any case, the proximal end  40  of the tip  38  is attached to the distal end  36  of the catheter body  32 . Preferably, the tip  38  is made of a thermally conductive material, and the catheter body  32  is made of a thermally insulating material. Stated differently, the tip  38  conducts heat more effectively than the catheter body  32 . The system  10  also includes a connector  44  that is attached to the distal end  18  of the cryocatheter  14 . As shown, the connector  44  is formed with a passageway  46  for receiving the guidewire  22 . Preferably, the guidewire  22  is a thin elongated rod with a circular cross-section. As will be appreciated by the skilled artisan, the guidewire  22  is flexible enough to pass through the vasculature of the patient  12  and is appropriately dimensioned to pass through the passageway  46  of the connector  44 .  
         [0022]    As shown in FIG. 3A, the catheter body  32  has a wall  48  that surrounds a lumen  50 . As envisioned for the present invention, the lumen  50  extends between the proximal end  34  (FIG. 1) and the distal end  36  of the catheter body  32 . Additionally, the wall  48  of the catheter body  32  has an inner surface  52  and an outer surface  54 . Preferably, the catheter body  32  is a hollow, substantially cylindrical-shaped tube.  
         [0023]    Still referring to FIG. 3A, it can be seen that the tip  38  of the cryocatheter  14  has a wall  56  surrounding an expansion chamber  58 . The proximal end  40  of the tip  38  provides for fluid access to the expansion chamber  58 , and the closed distal end  42  of the tip  38  partially encloses the expansion chamber  58 . Furthermore, the wall  56  of the tip  38  has an inner surface  60  and an outer surface  62 . Structurally, the proximal end  40  of the tip  38  is tightly affixed in a fluid-tight seal to the distal end  36  of the catheter body  32 . Thus, the expansion chamber  58  is in fluid communication with the lumen  50  of the catheter body  32 .  
         [0024]    Still referring to FIG. 3A, it can be seen that the supply line  24  is positioned in the lumen  50  of the catheter body  32  with the distal end  28  of the supply line  24  positioned in the expansion chamber  58  of the tip  38 . With this structure, the supply line  24  establishes fluid communication between the fluid source  30  and the expansion chamber  58  of the tip  38 . Preferably, the supply line  24  is a hollow, substantially cylindrical-shaped tube. Structurally, the supply line  24  and the catheter body  32  form a fluid return  64  in the lumen  50  of the catheter body  32  between the supply line  24  and the inner surface  52  of the wall  48  of the catheter body  32 .  
         [0025]    A preferred embodiment of the present invention can be described with reference to FIGS. 2 and 3A. In this embodiment, the connector  44  is formed as a swivel to allow the connector  44  to rotate around the longitudinal axis  43 . More specifically, the connector  44  includes an annular shaped member  66  and an extension arm  68 . The annular shaped member  66  is formed to surround the passageway  46  for receiving the guidewire  22  through the passageway  46  to connect the cryocatheter  14  with the guidewire  22 . As shown in FIG. 3A, the extension arm  68  has a first end  70  and a second end  72 . For this embodiment, the first end  70  of the extension arm  68  is formed as a ring  74  and the second end  72  of the extension arm  68  is connected to the annular shaped member  66 . The ring  74  is dimensioned to surround a post  76  that is attached to the tip  38 . More specifically, the post  76  has a proximal end  78  and a distal end  80 . The proximal end  78  of the post  76  is attached to the distal end  42  of tip  38  to extend the post  76  axially away from the tip  38  in a distal direction. A cap  82  is attached to a distal end  80  of the post  76  and is dimensioned to hold the ring  74  on the post  76  and to allow the connector  44  to rotate around the longitudinal axis  43 .  
         [0026]    In another embodiment of the present invention (see FIG. 3B), the first end  70  of the extension arm  68  is fixedly attached to the tip  38  of the cryocatheter  14  to extend its second end  72  radially outward from the longitudinal axis  43 . Preferably, the first end  70  is attached to the proximal end  40  of the tip  38  near the distal end  36  of the catheter body  32 . As with the previously disclosed embodiment, the connector  44  has an annular shaped member  66  that is connected to the second end  72  of the extension arm  68 . Also, as with the other embodiment, the annular shaped member  66  is formed with the passageway  46  for receiving the guidewire  22 .  
         [0027]    Still another embodiment of the present invention is shown in FIG. 3C. In this embodiment, the passageway  46  of the connector  44  is formed into the wall  56  of the tip  38 . In this case, the passageway  46  is formed between the inner surface  60  and the outer surface  62  of the wall  56 . As shown, the outer surface  62  of the wall  56  has a first opening  84  and a second opening  86 . Structurally, the passageway  46  extends between the first opening  84  and the second opening  86  of the wall  48  to receive the guidewire  22  through the passageway  46 . Preferably, the passageway  46  forms a slightly curved path through the wall  48  of the tip  38 .  
         [0028]    Another embodiment of the connector  44  is shown in FIG. 3D. In this embodiment, the passageway  46  of the connector  44  is formed into the wall  48  of the catheter body  32  substantially between the inner surface  52  and the outer surface  54  of the wall  48 . As shown, the outer surface  54  of the wall  48  has a first opening  88  and a second opening  90 . Structurally, the passageway  46  extends between the first opening  88  and the second opening  90  of the wall  48  to receive the guidewire  22 . Preferably, the passageway  46  forms a slightly curved path through the wall  48  of the catheter body  32 .  
         [0029]    The operation of the system  10  can perhaps be best described with reference to FIGS. 1 and 3A. Initially, the guidewire  22  is pre-positioned in the vasculature of the patient  12  to extend past the predetermined site  20 . The guidewire  22  is then threaded through the passageway  46  of the connector  44  to engage the cryocatheter  14  with the guidewire  22 . With the guidewire  22  positioned through the passageway  46  of the connector  44 , the distal end  18  of the cryocatheter  14  is advanced along the guidewire  22  through the vasculature of the patient  12  to position the tip  38  of the cryocatheter  14  at the predetermined site  20 . The tip  38  of the cryocatheter  14  can then be manipulated as necessary. For example, the tip  38  can be engaged with other devices at the predetermined site  20 , or it can be placed into contact with target tissue to perform a surgical cryoablation procedure on the target tissue. In any event, the supply line  24  introduces a cooled fluid from the fluid source  30  into the expansion chamber  58  of the tip  38 . Inside the expansion chamber  58 , the cooled fluid undergoes endothermic expansion to absorb heat from the tip  38  as the cooled fluid is transformed into a gas inside the expansion chamber  58 . The gas is then removed from the chamber  58  through the fluid return  64  to allow the supply line  24  to introduce additional cooled fluid into the chamber  58 . Once a procedure has been completed at the predetermined site  20 , the cryocatheter  14  can be withdrawn from the vasculature over the guidewire  22 .  
         [0030]    While the particular catheter system and method as herein shown and disclosed in detail is fully capable of obtaining the objects and providing the advantages herein before stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or design herein shown other than as described in the appended claims.