as illustrated in fig1 - 3 , the guidewire system 10 embodying features of the invention has a main section 11 which is adapted to be inserted into a patient &# 39 ; s vascular system and an extension section 12 which can be connected and disconnected to the main section 11 to facilitate the exchange of catheters without the need for removing the main section 10 from the patient &# 39 ; s vascular system . main guidewire 11 generally comprises an elongated shaft 13 with a flexible tip ( not shown ) at its distal end and a smaller diameter portion 14 at its proximal end which is shaped into an undulating or sinusoidal shape . reference is made to u . s . pat . no . 4 , 538 , 622 ( samson et al .) and u . s . pat . no . 4 , 569 , 347 ( frisbie ), which have been previously incorporated herein by reference , for a description of desirable guidewire tip constructions . extension section 12 has an elongated shaft 16 with smaller diameter projection or post 17 at its distal end . the connection 18 between guidewire sections 11 and 12 generally comprise tubular member 19 which is fixed to the distal end of the main section 12 and which receives interfitting undulating member 14 which is on the proximal end of section 11 . tubular member 19 is mounted by suitable means such as welding , brazing , or the like onto the short axial extention 17 of reduced diameter at the distal end of shaft 16 . axial extension or post 17 can be formed by any suitable means such as grinding down the proximal end portion of the shaft 16 to the desired diameter so that it interfits into the end of tubular member 15 . the undulating portion 14 is formed by first grinding the proximal end of main section 11 to a smaller diameter , then formimg the undulations or sinusoidal shape by bending over a mandrel or other suitable means . the maximum effective dimension a of the undulated section should be slightly more than the inner diameter b of tubular connecting piece 17 but preferably not more than 50 % greater than dimension b to provide interference or friction fit which will hold the sections together during catheter exchange but which can be readily disengaged after exchange has been made . preferably no more than a one pound pull should be necessary for disengagement . in a guidewire having a diameter on the order of about 0 . 014 inch , for example , tubular member 19 might have an inner diameter of about 0 . 007 inch and a wall thickness on the order of 0 . 001 inch and the undulating section 14 might have a maximum effective radial dimension of about 0 . 009 inch . in this embodiment , tubular member 19 might have a length on the order of about 2 . 4 - 2 . 5 cm . the main guidewire section is intended for use in positioning a dilatation catheter ( not shown ) in the cardiovascular system of a patient , and it has a length corresponding to the length of a conventional guidewire for this purpose . details of typical dilatation catheters and guidewires can be found in the patents cited previously and incorporated herein . extension section 12 is sufficiently long so that when the guidewire sections 11 and 12 are connected together the guidewire system 10 has an overall length suitable for exchanging catheters without removing the main section 11 from the patient &# 39 ; s vascular system . with a dilatation catheter having a length on the order of 120 - 140 cm , for example , section 11 might have a length of 140 - 175 cm , and section 12 might have a length of 125 - 160 cm . shafts 13 and 16 and tubular member 19 can be fabricated from suitable material , such as stainless steel , nitinol ( 55 % ni - bal . ti ), and the like , and each should have a diameter to allow a dilatation catheter to pass freely over them . it is perferably that the two shafts 13 and 16 be of substantially the same diameter in order to provide a smooth transition between them . in one presently preferred embodiment for use in coronary angioplasty , shafts 13 and 16 have a diameter on the order of about 0 . 014 inch . either or both of the shafts can be provided with a coating of polytetrafluoroethylene , which is sold under the trademark teflon by the dupont corporation , or another suitable low - friction material to facilitate the movement of the catheter over the wire . an alternative embodiment is shown in fig4 wherein the proximal end of main guidewire section 12 which is adapted to be inserted into the tubular member 19 is provided with a smaller diameter portion 30 having protrusions 31 which provide the interference or friction fit to releasably secure together the sections 11 and 12 of the guidewire system 10 . the protrustions can have various shapes such as the semi - spherical shapes shown in fig4 triangular shapes , or other shapes which may provide a suitable fit . in use , the main guidewire section 11 is introduced into the vascular system of a patient with a dilatation catheter through a guiding catheter not shown ) and an introducer ( not shown ). when performing coronary angioplasty , the distal end of the guiding catheter is positioned in the coronary ostium , and the dilatation catheter is advanced so that it is just proximal to the tip of the guiding cathether . the distal tip of the guidewire is advanced beyond the distal tip of the dilatation catheter while the latter is held in place . as the main guidewire section 11 is advanced , it is rotated and steered into the selected artery . the guidewire tip is preferably advanced through the lesion and beyond it , in order to permit the balloon portion of the dilatation catheter to be positioned within the lesion over a more supportive section of the guidewire . once in position , the main guidewire section 11 is held in place and the dilatation catheter is advanced along it until the inflatable balloon thereof is within the lesion . undulating end portion 14 remains outside the patient &# 39 ; s body and outside any adapter which may be connected to the proximal end of the dilatation catheter . to exchange catheters , the main guidewire section 11 is extended by manually pressing the open end of tubular member 19 on the distal end of extension section 12 onto the undulating end 14 . as the tubular member 19 is inserted over the undulating end 14 , either the tubular member 19 or the undulating member 14 or both deform to thereby firmly but releasably hold the two guidewire sections together . the dilatation catheter can then be withdrawn from the patient &# 39 ; s body over the extended guidewire system . a new dilatation catheter may then be introduced over the extension section 12 and advanced along the main guidewire section 11 within the patient &# 39 ; s body until the balloon crosses the lesion . once the proximal end of the new balloon catheter has advanced beyond connection 18 and tubular end portion 19 , section 12 can be removed by grasping the two guidewire sections 11 and 12 on opposite sides of the connection 18 and pulling them apart without disturbing the position of section 11 in the patient &# 39 ; s body . as previously described , the interference or friction fit between the undulating member 14 and the tubular member 19 should be sufficiently strong to hold the two guidewire sections 11 and 12 together while dilatation catheters are being exchanged , but should be capable of separation by a pulling force less than one pound . the invention has a number of important features and advantages . the two sections of the guidewire can be connected together whenever a longer wire is needed , and they can be separated whenever the additional length is not required . the two sections of the guidewire may be connected and disconnected by the physician by simply pressing them together and pulling them apart . this can be done as needed , and no special tools are required either to make the connection or to separate it . thus the catheter exchange is greatly simplified . it is apparent from the foregoing that a new and improved extended guidewire system and method of using the same have been provided . while the present invention has been described herein with the tubular connecting element fixed to the distal end of the guidewire extension section and the male member adapted to be inserted into the open end of the tubular member on the proximal end of the main guidewire section , it is obvious that the tubular element on the distal end of the extension section may be interchanged with the male member on the main guidewire section . moreover , it will be apparent to those familiar with the art , that other modifications and improvements can be made without departing from the scope of the invention as defined by the following claims .
an extendable guidewire system for introducing a dilatation catheter into the cardiovascular system . the guidewire has guidewire and extension sections with a connection therebetween which permits the two sections to be joined together and separated simply by pushing the two sections together and pulling them apart . one of the sections can be used for positioning the catheter within the cardiovascular system , and the other section can be employed to extend the wire to change catheters .