Abstract:
This invention relates to catheter delivery systems, and more specifically, to a tubular device with improved torque and flexure characteristics. The present invention is a tubular device having improved torque and flexure characteristics which uses a series of permanently interlocking independent segments to provide the necessary torque and flexure characteristics.

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S)  
         [0001]    None.  
         BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to catheter delivery systems, and more specifically to a tubular device with improved torque and flexure characteristics.  
           [0003]    Catheters, catheter guidewires, and flexible delivery devices have been used for several years to reach and provide treatment at target locations within the human body. For example, occlusion devices that seal heart defects are delivered to the treatment site via catheter, and balloon angioplasty is performed via catheter. Many designs for catheters and guidewires exist. The most important features of a catheter, guidewire, or delivery device are flexibility (so that it can navigate the winding human vasculature), and torque (so a physician can exert force sufficient to steer the device.) Most catheters are made of flexible plastic tubing and come in a variety of lengths and diameters. Most guidewires consist of a metal outer tube comprised of a metal coil coupled with an inner wire.  
           [0004]    In practice, physicians generally use a guidewire first to reach the desired location in the body. Upon insertion, the guidewire is tracked with either X-ray technology or ultrasound as the physician maneuvers it to the target location within the patient&#39;s body. A catheter can then be advanced over the guidewire after the guidewire has reached the treatment site. The guidewire may be left in place or removed while treatment is accomplished via the catheter.  
           [0005]    When the physician navigates to the treatment site, the guidewire must have sufficient flexibility to accomplish the sharp and numerous turns in the body&#39;s vasculature. If, however, the guidewire is too flexible, the resistance caused by surface contact with the body&#39;s vasculature and the numerous sharp turns will cause the guidewire to buckle and the physician will be unable to reach the treatment site. If the guidewire is too stiff, it will not be able to withstand the demanding angles of the vasculature and likewise will not be able to reach the treatment site. Thus there is a need in the art for a delivery tool that possesses both flexibility and navigability.  
         BRIEF SUMMARY OF THE INVENTION  
         [0006]    The present invention is a medical device, such as a guidewire or delivery device, having improved torque and flexure characteristics. This device uses a series of permanently interlocking independent segments to provide flexibility, pushability, pullability, and necessary torque characteristics. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a perspective side view of a tubular device extending through a catheter.  
         [0008]    [0008]FIG. 2 is a perspective side view of a portion of a tubular device having dovetailed independent interlocking segments.  
         [0009]    [0009]FIG. 3 is a perspective side view of two dovetail cut independent interlocking segments.  
         [0010]    [0010]FIG. 4 is a perspective side view of one dovetail cut independent segment.  
         [0011]    [0011]FIG. 5 a - 5   d  are enlarged perspective side views of a tooth of an independent interlocking segment which is experiencing pushing forces, pulling forces and left and right twisting forces, respectively.  
         [0012]    [0012]FIG. 6 is a perspective side view of a portion of the tubular device having rounded dovetailed independent interlocking segments.  
         [0013]    [0013]FIG. 7 is a diagram showing how flexure is programable by varying the number of segments per given length. 
     
    
     DETAILED DESCRIPTION  
       [0014]    [0014]FIG. 1 is a perspective side view of a tubular device  10  extending through a catheter  12 . The tubular device  10  is comprised of a plurality of independent interlocking segments  14  separated by channels  16 . The segments  14  comprise a series of dovetail cut interlocking teeth  18  shaped so that the segments  14  do not disconnect from one another. The segments  14  are separated by channels  16  which can expand axially to give the device  10  increased flexibility or compress axially for increased rigidity. An end segment  20  terminates the device  10  and may be modified to provide an attachment site for additional devices.  
         [0015]    The delivery device  10  is constructed of a plurality of segments  14  cut from a single tube. The segments  14  of the delivery device  10  are formed by making a series of cuts the tube. The tube is preferably surgical hypotubing made of stainless steel, nickel titanium, or another suitable material.  
         [0016]    The diameter of the tubing varies depending on use. In certain circumstances a tube of tapering or variable diameter may be more effective. For example, if the user prefers that the distal end (the end furthest away from the user) have a very small diameter, the tube may be tapered so that the diameter of the distal end is smaller than that of the proximal end (the end closest to the user). If the device  10  is going to be used in conjunction with a catheter  12 , as shown in FIG. 1, the diameter of the device  10  should be similar to the diameter of the catheter  12  so that the device  10  does not have much room to buckle if the device  10  encounters resistance while it is being advanced.  
         [0017]    One method of making cuts to form segments  14  is to use a laser. Other suitable cutting methods may also be used to accomplish the cuts, such as using a saw or cutting blade. The method of cutting varies depending on factors such as the size of the tubing and the material used. In an alternate embodiment, the device may be coated with plastic or film when a smooth surface is preferred. The plastic or film must be thin and flexible so that is does not adversely affect the properties of the device  10 .  
         [0018]    [0018]FIG. 2 shows independent interlocking segments  14 , channels  16 , and the end segment  20 . The segments  14  cannot be axially disconnected because they are defined by a dovetail cut design at each end. The segments  14  are shaped so that they interlock, or mate, with the adjacent segments, allowing flexure but not axial disconnection. In FIG. 2 a dovetail cut is shown but invention is not limited to this cut pattern. Another cut pattern which prevents the segments from axially disconnecting and allows flexure would work also.  
         [0019]    By cutting the tube into independent interlocking segments  14  which cannot be axially disconnected because of the cut shape, the segments  14  are able to transmit pushing and pulling forces to adjoining segments  14 . The cut design allows the device  10  to transmit axial pushing and pulling forces and also allows transmission of left and right (or counterclockwise and clockwise) twisting forces between segments  14 . In addition, as a result of this design, the amount of rigidity automatically adjusts based on the amount of resistance the device  10  encounters.  
         [0020]    When the user pushes on the device  10  at the proximal end, as each segment  14  experiences the pushing force, the segment  14  pushes on the distally adjoining segment  14 . Therefore, rigidity is created when the segments  14  experience pushing or pulling forces because the segments  14  are locked together with adjoining segments  14  as the width of the channels  22  decreases. The device  10  becomes more rigid as the channels  16  are compressed because the device  10  becomes more like a solid tube as the segments  14  interlock. However, when the segments  14  are not being pushed or pulled or are not experiencing resistance, the channels  16  can expand, the segments  14  do not lock against each other, and the device  10  is more flexible.  
         [0021]    [0021]FIG. 3 shows an enlarged perspective side view of two segments A, B, each having a proximal end  30  and a distal end  32 , as viewed from left to right. The proximal and distal ends  30 ,  32  are dovetail cut, so that they comprise a plurality of proximal and distal teeth  34 P, 34 D and grooves  36 . The grooves  36  are defined by the teeth  34 P,  34 D. The distal teeth  34 D of segment A fit into the grooves  36  on the adjoining segment B. The distal teeth  34 D of segment A widen at the ends and therefore cannot be pulled out of the grooves  36  on the adjoining segment B.  
         [0022]    The shape of teeth  34 P,  34 D and grooves  36  also prevents the segments A, B from rotating laterally, providing torque when needed. The sides of the teeth  34 P,  34 D and the sides of the grooves  36  provide additional lateral torsion. Because the segments A, B cannot rotate laterally, the pushing or pulling force remains longitudinally directed and the device does not “buckle”.  
         [0023]    In this embodiment, each segment A, B has four teeth  34 D,  34 P on each end. If the diameter of the tube used to construct device  10  is increased, the number of teeth  34 D,  34 P may increase also. In addition, the angle of the dovetail cut may be varied to alter the flexibility of the device.  
         [0024]    [0024]FIG. 4 is an enlarged perspective view of one segment  14 , having a proximal end  30  and a distal end  32 , as viewed from left to right. Also shown are proximal and distal teeth  34 P,  34 D, grooves  36 , and mating surface area  38 . The teeth  34 P,  34 D are relatively aligned with the grooves  36  on the opposite end of the segment  14 .  
         [0025]    By cutting the tube into independent interlocking segments  14  which cannot be axially disconnected because of the cut shape, the segments  14  are able to transmit pushing, pulling, and left and right twisting forces to adjoining segments  14  through their mating surfaces  38 . The thickness of the walls of the tube determines the amount of mating surface area  38  between segments  14 . As the mating surface area  38  is increased, the pushing, pulling, and torsional strength is increased. However, the flexibility of the device decreases as the mating surface  38  increases. Thus, the thickness of the walls of the tube may also be varied according to user needs.  
         [0026]    [0026]FIG. 5 a  through FIG. 5 d  are enlarged perspective side views of a single tooth experiencing pushing and pulling forces and left and right twisting forces. FIGS. 5 a - 5   d  demonstrate how different sides of the teeth engage different sides of the grooves when the tooth experiences either pushing, pulling, or twisting forces.  
         [0027]    In FIG. 5 a , a distal end tooth  34 D is located in the groove  36  between two proximal end teeth  34 P. Shown are two segments A, B, a distal end tooth  34 D, two proximal end teeth  34 P and a groove  36 . The distal end tooth  34 D is experiencing a pulling force. The distal end tooth  34 D cannot be pulled any further out of the groove  36  because the tooth  34 D is too wide at its top to be pulled any further. Thus, a jam fit is created and the pulling force experienced by the first segment A is transferred to the second segment B.  
         [0028]    In FIG. 5 b  a distal end tooth  34 D is located in the groove  36  between two proximal end teeth  34 P. Shown are two segments A, B, a distal end tooth  34 D, two proximal end teeth  34 P and a groove  36 . The distal end tooth  34 D is experiencing a pushing force. The distal end tooth  34 D cannot be pushed any further into the groove  36  because the tooth  34 D has hit the proximal end of the groove  36 . Thus, a jam fit is created and the pushing force experienced by the first segment A is transferred to the second segment B.  
         [0029]    In FIG. 5 c  a distal end tooth  34 D is located in the groove  36  between two proximal end teeth  34 P. Shown are two segments A, B, a distal end tooth  34  D, two proximal end teeth  34  P and a groove  36 . The distal end tooth  34 D is experiencing a left, or counter-clockwise, twisting force. The distal end tooth  34 D cannot be rotated any further in the groove  36  because the tooth  34 D has been rotated enough to reach the lower end of the groove  36 . Thus, a jam fit is created and the counter-clockwise twisting force experienced by the first segment A is transferred to the second segment B.  
         [0030]    In FIG. 5 c  a distal end tooth  34 D is located in the groove  36  between two proximal end teeth  34 P. Shown are two segments A, B, a distal end tooth  34  D, two proximal end teeth  34  P and a groove  36 . The distal end tooth  34 D is experiencing a right, or clockwise, twisting force. The distal end tooth  34 D cannot be rotated any further in the groove  36  because the tooth  34 D has been rotated enough to reach the upper end of the groove  36 . Thus, a jam fit is created and the clockwise twisting force experienced by the first segment A is transferred to the second segment B.  
         [0031]    [0031]FIG. 6 is a perspective side view of a portion of a device  10 . Shown in FIG. 5 is the device  10 , having independent interlocking segments  40  defined by rounded dovetail cut ends, and channels  42 . The segments  40  remain axially connected because they are defined by a rounded dovetail cut design on each end. The segments  40  are shaped so that they interlock, or mate, with the adjacent segments, allowing flexure but not axial disconnection. Again, the invention is not limited to this cut pattern; another cut pattern which prevents the segments from axially disconnecting and allows flexure would work also.  
         [0032]    As previously mentioned, by cutting the tube into independent interlocking segments  40  which cannot be axially disconnected because of the cut shape, the segments  40  are able to transmit pushing and pulling forces to adjoining segments  40 . Rigidity is created when the segments  40  experience pushing or pulling forces because the segments  40  lock together with adjoining segments  40  as the width of the channels  42  decreases. When the segments  40  are not being pushed or pulled or are not experiencing resistance, the channels  42  expand, the segments  40  do not lock against each other, and the device  10  is more flexible.  
         [0033]    [0033]FIG. 7 is a diagram showing the programmability of the device  10 . Shown is the device  10 , region “A”, and region “B”. Region “A” has fewer cuts per centimeter than region “B” and therefore has fewer segments per centimeter. As the number of segments per given length increases, the flexibility of the device  10  increases. Thus, the number of segments per given length can be varied to accommodate certain demands.  
         [0034]    For example, when a physician attempts to deliver a cardiac occlusion device to the heart via catheter, the end of the delivery device would be very flexible, ideally. Often, the delivery device must be forced into the heart at an angle, which causes the tissue surrounding the defect to become distorted. If the cardiac tissue is distorted, it is difficult to determine whether the device will be properly seated once the delivery device is removed and the tissue returns to its normal state. If the device is not seated properly, blood will continue to flow through the defect and the device may have to be retrieved and re-deployed. In this situation, it is advantageous to have a delivery device that is very flexible at the end that enters the heart. If the end is very flexible, the amount of distortion can be drastically decreased. The amount of cuts per centimeter can be increased at the distal end of the device  10  to give it the necessary flexibility at the distal end.  
         [0035]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.