Guidewire tip construction

Abstract

A guidewire for use in guiding a catheter has a tip construction that includes a core wire within a helical coil. The core wire has a distal tip segment that is tapered and is further impressed with a pair of opposed flattened surfaces extending along the taper, the surfaces lying at an angle to each other and defining a progressively flattened tip having increased width in a distal direction to define a duck-bill configuration. The tip construction provides improved column strength at the tip to resist guidewire prolapse while providing excellent torsional and flexibility characteristics.

Having thus described the invention what I desire to claim and secure by Letters Patent is:  
     
       1. In a guidewire adapted for use with a catheter, the guidewire including a helical coil at its distal end and a core wire having a longitudinal axis and extending through the helical coil, the improvement comprising: 
       the core wire having a distal tip portion that is tapered and includes a pair of opposed flattened surfaces along the tapered portion, the flattened surfaces extending distally at an angle outward to the longitudinal axis of the core wire, the juncture of the flattened and unflattened surfaces being free of sharp cross-sectional transitions.  
     
     
       2. In a guidewire as defined in claim  1 , the improvement further comprising: 
       tip portion being substantially shoulderless.  
     
     
       3. In a guidewire as defined in claim  1 , the improvement further comprising the flattened surfaces each having a proximal end and a distal end, the proximal ends of the flattened surfaces being narrower in width than the distal ends. 
     
     
       4. In a guidewire as defined in claim  3 , the improvement further comprising: 
       the width of the flattened surfaces increasing progressively from the proximal to the distal ends of said surfaces.  
     
     
       5. In a guidewire as defined in claim  3 , the improvement further comprising: 
       the width of the flattened surfaces at the distal end of the distal tip portion being greater than the diameter of the distal tip portion immediately adjacent the proximal end of the flattened surfaces.  
     
     
       6. In a guidewire as defined in claim  5 , the improvement further comprising: 
       the width of the flattened surface at the tip of the helical coil occupying the major portion of the inner diameter of the helical coil.  
     
     
       7. In a guidewire as defined in claim  6 , the improvement further comprising: 
       the width of the flattened surface occupying substantially the full inner diameter of the coil at the tip of the coil.  
     
     
       8. In a guidewire as defined in claim  5 , the improvement further comprising: 
       the ratio of the width to the thickness of the flattened surfaces, at their distal ends, being not less than about 5 to 1.  
     
     
       9. In a guidewire as defined in claim  5 , the improvement further comprising: 
       the ratio of the width to the thickness of the flattened surfaces, at their distal ends, being not less than about 7 to 1.  
     
     
       10. In a guidewire as defined in claim  1 , the improvement further comprising: 
       the coil being attached securely to the distal tip portion of the core wire at a location that intersects the flattened surfaces.  
     
     
       11. In a guidewire as defined in claim  10 , the improvement further comprising: 
       the attachment being defined at a distal braze joint.  
     
     
       12. In a guidewire as defined in any one of claims  1 - 11  wherein said guidewire comprises an angioplasty guidewire. 
     
     
       13. A guidewire for use with a catheter comprising: 
       an elongate flexible shaft having a proximal end and a distal end;  
       a helical coil mounted about the distal portion of the shaft, the portion of the shaft extending through the helical coil defining a core wire;  
       the helical coil being attached to the shaft at the proximal end of the helical coil;  
       the core wire having a distal tip portion that is tapered and includes a pair of opposed flattened surfaces along the tapered portion, the flattened surfaces extending distally at an angle outward to the longitudinal axis of the core wire, the juncture of the flattened and unflattened surfaces being free of sharp cross-sectional transitions.  
     
     
       14. In a guidewire as defined in claim  13 , the improvement further comprising: 
       tip portion being substantially shoulderless.  
     
     
       15. In a guidewire as defined in claim  13 , the improvement further comprising the flattened surfaces each having a proximal end and a distal end, the proximal ends of the flattened surfaces being narrower in width than the distal ends. 
     
     
       16. In a guidewire as defined in claim  15 , the improvement further comprising: 
       the width of the flattened surfaces increasing progressively from the proximal to the distal ends of said surfaces.  
     
     
       17. In a guidewire as defined in claim  15 , the improvement further comprising: 
       the width of the flattened surfaces at the distal end of the distal tip portion being greater than the diameter of the distal tip portion immediately adjacent the proximal end of the flattened surfaces.  
     
     
       18. In a guidewire as defined in claim  17 , the improvement further comprising: 
       the width of the flattened surface at the tip of the helical coil occupying the major portion of the inner diameter of the helical coil.  
     
     
       19. In a guidewire as defined in claim  18 , The improvement further comprising: 
       the width of the flattened surface occupying substantially the full inner diameter of the coil at the tip of the coil.  
     
     
       20. In a guidewire as defined in claim  17 , the improvement further comprising: 
       the ratio of the width to the thickness of the flattened surfaces, at their distal ends, being not less than about 5 to 1.  
     
     
       21. In a guidewire as defined in claim  17 , the improvement further comprising: 
       the ratio of the width to the thickness of the flattened surfaces, at their distal ends, being not less than about 7 to 1.  
     
     
       22. In a guidewire as defined in claim  14 , the improvement further comprising: 
       the coil being attached securely to the distal tip portion of the core wire at a location that intersects the flattened surfaces.  
     
     
       23. In a guidewire as defined in claim  22 , the improvement further comprising: 
       the attachment being defined at a distal braze joint.  
     
     
       24. In a guidewire as defined in any one of claims  13 — 23  wherein said guidewire comprises an angioplasty guidewire. 
     
     
       25. In a guidewire adapted for use with a catheter, the guidewire including a helical coil at the distal end of the guidewire and a core wire extending through the helical coil to the distal tip, the improvement comprising: 
       the distal portion of the core wire being substantially flat and having a width that spans the major portion of the inner diameter of the helical coil.  
     
     
       26. In a guidewire as defined in claim  1 , the improvement further comprising: 
       the flat tip of the core wire spans substantially the entire inner diameter of the helical coil at the distal tip of the helical coil.  
     
     
       27. In a method for forming a medical guidewire, the improvement comprising: 
       providing a core wire having a tapered distal tip portion;  
       impressing a pair of opposed flattened surfaces along the tapered portion, the flattened surfaces extending distally at an angle outward to the longitudinal axis of the core wire, the juncture of the flattened and unflattened surfaces being free of cross-sectional transitions.  
     
     
       28. The method of claim  27 , comprising inserting the distal tip of the core wire between a pair of dies, bringing the dies together and impressing wedge-like surfaces on the distal tip portion of the core wire. 
     
     
       29. The method of claim  28 , wherein one of the dies is stationary and the second die is moveable toward and away from the stationary die. 
     
     
       30. The method of claim  28 , wherein each die has a channel extending lengthwise of the die and the channels define an elongate working surface and each die having a butting surface which defines the limit to which the dies can be brought together. 
     
     
       31. The method of claim  30 , wherein the elongate working surfaces of the dies have a proximal portion inclined at an angle sought to be impressed on the distal end of the core wire and have distal portions which are more closely parallel to the butting surfaces of the dies. 
     
     
       32. The method of claim  30 , wherein the working surfaces are, finished smoothly. 
     
     
       33. The method of claim  31 , wherein a space between surfaces of the proximal portions of the dies at an opening end of the dies is greater than a maximum diameter of an unflattened tapered distal tip segment of the core wire. 
     
     
       34. The method of claim  29 , comprising subjecting the moveable die to a sharp impact to forcibly bring the dies together and thus deforming the distal tip portion of the core wire. 
     
     
       35. The method of claim  30 , wherein the dies are formed such that a length of the working surface at the proximal end of the dies is spaced from the core wire such that flattened surfaces of the core wire will merge with an unflattened surface of the core wire in a shoulderless transition. 
     
     
       36. In a guidewire adapted for use with a catheter, the guidewire having a proximal end and a distal end, wherein the distal end has a distal tip, the guidewire including a helical coil at the distal end of the guidewire and a core wire extending through the helical coil to the distal tip of the guidewire, the improvement comprising: 
         the core wire having a distal segment with a pair of opposed surfaces that are substantially flat and a distal tip, wherein the thickness of the distal segment of the core wire is progressively tapered toward the distal tip of the core wire without sharp shoulders or cross - sectional transitions.    
     
     
       37. In a guidewire adapted for use with a catheter, the guidewire having a proximal end and a distal end, wherein the distal end has a distal tip, the guidewire including a helical coil at the distal end of the guidewire and a core wire extending through the helical coil to the distal tip of the guidewire, the improvement comprising: 
         the core wire having a distal segment with a pair of opposed surfaces that are substantially parallel and a distal tip, wherein the thickness of the distal segment of the core wire is progressively tapered toward the distal tip of the core wire without sharp shoulders or cross - sectional transitions.    
     
     
       38. In a guidewire adapted for use with a catheter, the guidewire having a proximal end and a distal end, wherein the distal end has a distal tip, the guidewire including a helical coil at the distal end of the guidewire and a core wire extending through the helical coil to the distal tip of the guidewire, the improvement comprising: 
         the core wire having a distal segment with a pair of opposed surfaces that are substantially flat and a distal tip, wherein the thickness of the distal segment of the core wire is progressively tapered toward the distal tip of the core wire without sharp shoulders or cross - sectional transitions and the width of the distal segment of the core wire progressively widens in cross - section to the distal tip of the core wire.    
     
     
       39. In a guidewire adapted for use with a catheter, the guidewire having a proximal end and a distal end, wherein the distal end has a distal tip, the guidewire including a helical coil at the distal end of the guidewire and a core wire extending through the helical coil to the distal tip of the guidewire, the improvement comprising: 
         the core wire having a distal segment with a pair of opposed surfaces that are substantially flat and a distal tip, wherein the thickness of the distal segment of the core wire is progressively tapering to the distal tip of the core wire without sharp shoulders or cross - sectional transitions.    
     
     
       40. In a guidewire as defined in claim  1 , the improvement further comprising: 
       
         the flat tip of the core wire spans substantially the entire inner diameter of the helical coil at the distal tip of the helical coil.