Guidewire for positioning a catheter against a lumen wall

Abstract

The present invention relates to a guidewire having a shaped three dimensional guide section. In the preferred embodiment the guide section is helical, and exerts an outward radial force on a lumen the guidewire is constrained in. The outward radial force can be measured or calculated according to methods of the present invention. Also described is a system comprising a guidewire and catheter where the force of the catheter exerts on a body lumen can also be calculated. Apparatus and methods of making the guidewire are also disclosed, as well as alternative embodiments of the guidewire.

What is claimed is:  
     
         1 . A portable force resistance meter for determining a catheter resistance value comprising: 
 an aperture for receiving a catheter distal end;    a deflection lever for moving said catheter distal end a quantifiable distance;    a load cell linked to said deflection lever for determining a beam stiffness value for said catheter distal end;    a microprocessor for converting said beam stiffness value into a force resistance value using the quantifiable distance and the length of the catheter distal end; and    a display unit.    
     
     
         2 . A method of determining the outward radial force of a helical guide section comprising the steps of: 
 (a) securing a helical guide section in a force measuring device;    (b) fixing each end of the helical guide section in said force measuring device;    (c) pulling the ends of the helical guide section apart;    (d) measuring the force required to pull the helical guide section apart while tracking the linear displacement of the helical guide section during the pull;    (e) measuring the corresponding radial displacement of the guide section while the guide section is being pulled; and    (f) determining the radial force of the guide section from the measured axial force, the measured linear displacement and the measured radial displacement.    
     
     
         3 . A method of determining the outward radial force of a catheter over a helical guide section comprising the steps of: 
 (a) measuring the beam stiffness of a catheter;    (b) measuring the beam stiffness of a helical guide section;    (c) measuring the axial force required to elongated a helical guide section to one half the helical guide section unconstrained diameter; and    (d) determining P eff .    
     
     
         4 . The method of  claim 2 , wherein said force measuring device is a portable hand held device.  
     
     
         5 . A method of matching a catheter to a guidewire for a medical procedure requiring precision radial positioning comprising the steps of: 
 (a) determining a lumen diameter of a body lumen to be treated;    (b) selecting a catheter to be used in said body lumen;    (c) choosing the effective length of said catheter;    (d) measuring a catheter resistance value of said catheter over said effective length; and    (e) matching a guidewire having a compressible guide section to said catheter resistance value to ensure said guidewire has sufficient outward radial force when compressed to deflect said catheter into said lumen wall.    
     
     
         6 . The method of  claim 5 , wherein step (d) further comprises measuring the beam stiffness in a portable force measuring device and converting the beam stiffness of said catheter into said catheter resistance value.  
     
     
         7 . An apparatus for shape setting a wire with a curved three dimensional guide section, said apparatus comprising: 
 a mandrel having a temperature stable core, at least one screw thread having spaced apart roots capable of mechanically receiving a wire; and    at least one retaining device for securing said wire within said spaced apart roots and preventing said wire from slipping or shifting.    
     
     
         8 . The apparatus of  claim 7 , wherein said mandrel has a minor diameter between 0.5 and 20 mm.  
     
     
         9 . The apparatus of  claim 7 , wherein said mandrel has a non-uniform minor diameter.  
     
     
         10 . The apparatus of  claim 7 , wherein said mandrel has a uniform linear geometry.  
     
     
         11 . The apparatus of  claim 7 , wherein said mandrel has a non-uniform linear geometry.  
     
     
         12 . The apparatus of  claim 7 , wherein the mandrel has a plurality of cross section geometries.  
     
     
         13 . The apparatus of  claim 7 , wherein said cross sectional geometries are any combination of regular and irregular shapes.  
     
     
         14 . The apparatus of  claim 7 , wherein the distance between said roots is between 0.026 mm and 12.7 mm.  
     
     
         15 . The apparatus of  claim 7 , wherein the distance between said roots is preferably between 1 mm and 6 mm.  
     
     
         16 . The apparatus of  claim 7 , wherein said mandrel is hollow.  
     
     
         17 . The apparatus of  claim 7 , wherein said mandrel is made of brass.  
     
     
         18 . The apparatus of  claim 7 , wherein said mandrel is made of any form of steel.  
     
     
         19 . The apparatus of  claim 7 , wherein said mandrel is made of a ceramic material.  
     
     
         20 . The apparatus of  claim 7 , wherein the retaining device is a clip.  
     
     
         21 . The apparatus of  claim 7 , wherein the retaining device is a tube slidably fit over said mandrel.  
     
     
         22 . A system for shape setting a guidewire comprising: 
 a rotatable chuck;    a mandrel having at least one screw thread engraved along at least a portion of said mandrel axial length;    at least one spring tension arm for providing tension to a core wire as said core wire is wrapped around a mandrel; and    a heating element for heating said core wire to a shape setting temperature.    
     
     
         23 . The system of  claim 22 , wherein said rotatable chuck is mounted on a lathe.  
     
     
         24 . The system of  claim 22 , further comprising an automated operation of the core wire winding and heating process through a series of stepper motors .  
     
     
         25 . The system of  claim 22 , wherein said spring tension arm is a restraining means for securing said core wire about said mandrel.  
     
     
         26 . The system of  claim 24 , wherein the automated operation is handled by a computer.  
     
     
         27 . A method of manufacturing a guidewire with a curved three dimensional guide section comprising the steps of: 
 (a) wrapping a core wire around a mandrel;    (b) securing the core wire about the mandrel;    (c) heating the mandrel assembly to a temperature between 300 degrees C. and 800 degrees C.;    (d) stopping the heating;    (e) cooling the mandrel assembly to room temperature; and    (f) unwrapping the core wire from the mandrel.    
     
     
         28 . The method of manufacturing a guidewire as in  claim 27 , further comprising the steps of: 
 (g) coating the core wire with a biocompatible material;    (h) attaching a filament wire to the core wire; and    (i) providing an atraumatic tip at the distal end.    
     
     
         29 . The method of  claim 27 , wherein step (a) comprises a core wire composed at least partially of a shape memory material.  
     
     
         30 . The method of  claim 27 , wherein step (a) comprises a core wire composed at least partially of a shape memory alloy.  
     
     
         31 . The method of  claim 27 , wherein step (a) comprises a core wire composed of nickel-titanium.  
     
     
         32 . The method of  claim 27 , wherein step (a) comprises a core wire composed of stainless steel with a shape memory material laminate coating.  
     
     
         33 . The method of  claim 27 , wherein step (a) comprises a core wire composed of a stainless steel and shape memory sandwich.  
     
     
         34 . The method of  claim 27 , wherein step (a) comprises a core wire composed of at least one wire within a shape memory material matrix, said shape memory matrix being formed in particular to operate as a guidewire.  
     
     
         35 . The method of  claim 27 , wherein step (a) further comprises a core wire having a diameter between 0.0005″ and 0.020″.  
     
     
         36 . The method of  claim 27 , wherein the mandrel further comprises a fixed channel for providing a predetermined shape setting.  
     
     
         37 . The method of  claim 36 , further comprising a mandrel minor diameter between 0.5 mm and 20 mm.  
     
     
         38 . The method of  claim 37 , wherein the mandrel preferably comprises a mandrel diameter of 1 to 6 mm.  
     
     
         39 . The method of  claim 27 , wherein step (a) further comprises ensuring the core wire is wound such that there is no slack in the wire coils.  
     
     
         40 . The method of  claim 27 , wherein step (b) further comprises a means for securing the wire about the mandrel to assure the core wire does not unravel or slip.  
     
     
         41 . The method of  claim 27 , wherein step (c) further comprises heating the mandrel assembly to a temperature between 450 and 550 degrees C.  
     
     
         42 . The method of  claim 41 , wherein the mandrel assembly remains at temperature from 1 to 10 minutes.  
     
     
         43 . The method of  claim 27 , wherein step (e) further comprises quenching the mandrel assembly.  
     
     
         44 . The method of  claim 28 , wherein step (g) is omitted.  
     
     
         45 . The method of  claim 28 , wherein step (h) is omitted.  
     
     
         46 . The method of  claim 28 , wherein step (i) is omitted.  
     
     
         47 . The method of  claim 28 , wherein step (g) further comprises coating the core wire with a laminate material for reducing the guidewire coefficient of friction.  
     
     
         48 . The method of  claim 28 , wherein step (i) further comprises attaching an atraumatic element to said core wire.