fig1 shows the outer shape of the guide member 10 . the guide is sized so that it will be of sufficient length and outer diameter to be readily advanced through blood vessels until its distal end 12 reaches a desired location within the vascular system . it is also sized so that the guide 10 can be received within the guide lumen of a catheter such as an angioplasty balloon catheter ( not shown ) with which it is to used . also shown in fig1 is a knurled handle member 14 which is affixed to the proximal end of the assembly and which can be rotated to apply a desired torque to the distal end 12 . fig2 - 4 show the internal construction of the catheter guide 10 . the guide 10 is seen to include an inner tube 16 , an outer tube 18 , and a formable member 20 which is typically a wire having a memory property . it is not essential to the invention that the member 16 be tubular , but instead , may comprise a long , thin flexible solid wire . in the preferred embodiment , the inner member 16 is tubular in form and may be constructed of stainless steel such as used in forming hypodermic needles and the outer tube 18 may be made of teflon plastic or some other suitable polymer to yield a low coefficient of friction between the exterior wall of tube 16 and the interior wall of tube 18 and a smooth , non - thrombogenic exterior surface . making the outer tube 18 of teflon also yields a low coefficient of friction between the guide and any adjoining blood vessel or catheter wall when being used . similar low coefficients of friction can be obtained if a material other than teflon is used for the outer tube 18 by coating the parts with a suitable hydrophilic polymer which becomes slippery when wetted . an important feature of the present invention is the inclusion of a formable member 20 and its interrelationship with the other components of the design . as best shown in fig2 member 20 is attached to and projects outwardly beyond the distal end of inner tube 16 and may be tapered along its length as illustrated . a secure attachment between tube 16 and member 20 can be achieved through the use of an appropriate adhesive or by crimping the tube 16 to the member 20 . where the inner member 16 is a solid wire rather than a tube , it may include an integrally formed formable member on its distal end . the purpose of member 20 is to provide a means by which the distal end 12 of the guide 10 can be formed so that it can be readily steered through blood vessels by manipulation of the handle member 14 at the proximal end of the guide member . thus , it is important that the member 20 be stiff yet sufficiently flexible and able to retain a desired shape . the use of a radiopaque material for the forming member also proves expedient when fluroscopic techniques are used to view the inserting of the guide member . member 20 and the distal end portion of the center tube 16 is also secured to the outer tube 18 . the manner in which this is achieved is best shown in fig2 and 4 . as shown in fig4 in the preferred embodiment , the distal end of the outer tube 18 is irregular in shape , creating a spline . an adhesive or moldable plastic 21 is then inserted into the gap 22 between member 20 and the splined portion of outer tube 18 . adhesives or moldable plastics which bond well to the material of the member 20 are to be selected because , when such materials set up , they will mechanically coact with the splines of the outer tube 18 to create a positive coupling irrespective of the low coefficient of friction of teflon material . with this construction , upon rotation of the hub 14 connected to the inner tube 16 , tube 16 will rotate within the outer tube 18 and torque necessary for steering the distal end of the guide 10 is directly applied to the distal end portion of the guide member 10 only cause the distal tip end occupied by forming member 20 and the splined portion of outer tube 18 to rotate . given the structure described above , use of the guide member is relatively straight - forward and easily understood . when in use , the distal end of guide member 10 is manually bent by the surgeon to a desired angle or curvature and inserted through a working catheter until the distal end of the guide projects a short distance beyond the distal end of the working catheter . such working catheters have a lumen running their entire length . this lumen is designed to receive the guide member 10 . a conventional introducer is used to insert the guide member 10 and catheter into the blood vessel . the guide member and catheter are then advanced through the blood vessel until the distal end 21 of the guide member reaches a desired location , such as a vascular branch . the guide member is then steered as it is further advanced by manipulating the handle 14 while holding the outer tube 18 of the guide member 10 stationary . the catheter travels with the guide member as the two are advanced . once the guide member 10 has been fully advanced into the desired position within the vessel , the working catheter ( such as one designed for coronary angioplasty ) is advanced further over the guide member until the working portion of the catheter reaches the treatment site . the guide member 10 can then be withdrawn , making the catheter &# 39 ; s lumen available for other uses , such as the profusion of blood or other fluids . with no limitation intended , the outer diameter of the inner tube 16 may be in the range from 0 . 008 to 0 . 038 mills and may have a wall thickness of 0 . 005 mills which , when formed from stainless steel , provides sufficient flexure to the overall guide member 10 while effectively transferring torque to the distal end of the assembly when the knob or handle 14 is rotated . where a solid wire core is used instead of tubular stock for the member 16 , it may comprise a stainless strand having a diameter in the range of form 0 . 008 inches to 0 . 038 inches . this invention has been described herein in considerable detail in order to comply with the patent statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as are required . however , it is to be understood that the invention can be carried out by specifically different equipment and devices , and that various modifications , both as to equipment details and operating procedures , can be accomplished without departing from the scope of the invention itself .
a steerable catheter guide comprised of an outer tube and an inner member surrounded by and rotatable with respect to said outer tube is disclosed . the steerable catheter guide also includes a formable member bonded to said inner member and said outer tube in the area of their respective distal ends . this design causes any rotation of the inner member with respect to the outer member to impart a torque directly to the distal end of the guide making steering much easier and less erratic .