Abstract:
A guide wire is disclosed which has a radiopaque distal lip and three or nor discrete highly radiopaque sections separated by relatively non-radiopaque sections. The highly radiopaque sections may be formed of coils and may have a width greater than their diameter. A method of marking the position of an intravascular anatomical feature (e.g., a stenosis) using the guide wire is also disclosed.

Description:
This is a continuation of application Ser. No. 07/969,047, filed Oct. 30, 1992 which is a continuation of application Ser. No. 07/452,710, filed Dec. 19, 1989 and issued as Pat. No. 5,209,730 dated May 11, 1993. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the field of angioplasty and in particular, to new and improved catheters for performing balloon angioplasty procedures on blood vessels. 
     2. Description of the Prior Art 
     Angioplasty has gained wide acceptance in recent years as an efficient and effective method for treating vascular diseases. Angioplasty is widely used in the treatment of stenosis within the coronary arteries, although it has been used for the treatment of stenosis in other areas of the vascular system. 
     The most widely used method of angioplasty makes use of a dilatation catheter which has an inflatable balloon member at a distal end and an inner lumen for acceptance of a guide wire (or only called an “over-the-wire catheter”). The guide wire is typically about 175 cm in length, and is threaded through the vascular system by tracking radiopaque markers contained at a distal tip of the guide wire, which are monitored on an x-ray fluoroscope. Once the guide wire is positioned, the dilatation catheter is pushed along the guide wire until its balloon member is across the stenosis. The balloon member is subsequently inflated with liquid, exerting pressure radially and outwardly against the stenosis, causing the artery wall to stretch and re-establishing an acceptable blood flow through the artery. 
     An area of stenosis is normally transparent to x-ray fluoroscope viewing, but can be seen by a periodic injection of dye into the artery. This periodic injection allows a limited time fluoroscopic viewing of the restricted artery flow caused by the stenosis, allowing the guide wire to be positioned across the stenosis and into a distal artery, which provides support for the dilatation catheter. However, because dye injections cause surgical complications, physicians disfavor injecting additional dye into the artery in order to properly position the balloon member. On the other hand, physicians want to complete the operation as quickly as possible in order to minimize radiation exposure to the patient and staff. Thus, physicians do not want to spend a large amount of time trying to locate the stenosis. Therefore, there is a need for a method to properly mark a stenosis in order to timely position the balloon member without injecting additional dye. 
     In addition to properly positioning a first balloon member across the stenosis, some surgical procedures require the use of more than one dilatation catheter. For example, the balloon member of the first catheter might have a profile that is too large to fit into the stenosis. Using an extendable or exchange (300 cm in length) guide wire, a physician can exchange the first balloon member with a dilatation catheter having a second balloon member with a smaller profile, while attempting to maintain the guide wire in its position across the stenosis. 
     A dilatation catheter normally contains one or more markers to allow its balloon member to be located on a fluoroscope. To position the balloon member without the use of additional dye, a method must be used whereby the stenosis can be pinpointed while the stenosis is temporarily displayed. One method is to use a grease pen to mark the location of the stenosis on the screen of the fluoroscope. Another method is to take a picture of the fluoroscope screen while the stenosis can be seen and then use the picture to later position the balloon member across the stenosis. 
     As can be readily appreciated, these methods of positioning a balloon member are generally time consuming and relatively inaccurate. Also, they require the patient to remain perfectly still in order to have the location marked on the screen correspond to the actual location of the stenosis. Keeping the patient still is especially difficult when a second dilatation catheter is needed to perform the procedure because of the additional time required to complete the catheter exchange on the guide wire. Therefore, there is a need for an accurate method of positioning a balloon member of an over-the-wire dilatation catheter across a stenosis in a timely fashion and without injecting additional dye to locate the stenosis. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention is a guide wire which has a radiopaque distal tip and three or more discrete highly radiopaque sections separated by relatively non-radiopaque sections on the distal portion. The highly radiopaque sections may be formed of coils and may have a width greater than their diameter. Similarly, the relatively non-radiopaque sections may have a width greater than their diameter- The radiopaque sections may be 1 mm in width and may be spaced 1.5 cm apart The distal tip of the guide wire may be a coil and the proximal portion may be a solid metal core. 
     In use, the guide wire is inserted into the vasculature of a patient and one of the radiopaque markers is positioned adjacent an anatomical feature inside the vasculature. The position of the radiopaque marker is maintained relative to the anatomical feature, thus marking the position of the feature. A catheter may be advanced over the guide wire and positioned such that the marker band of the catheter is adjacent one of the discrete radiopaque markers on the guide wire. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of an over-the-wire dilatation catheter system in accordance with the present invention. 
     FIG. 2 is an enlarged sectional view of a distal portion of a guide wire and an over-the-wire balloon dilatation catheter combination of the present invention. 
     FIG. 3 is a sectional view as taken on line  3 — 3  of FIG.  2 . 
     FIG. 4 is a sectional view as taken on line  4 — 4  of FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Catheter  10 , as shown in FIGS. 1-4, is an over-the-wire balloon dilatation catheter which includes a manifold  12 , a shaft  14 , a balloon member  16  and a guide wire  18 . 
     Manifold  12 , defining a proximal portion of catheter  10 , provides a means for introducing the guide wire  18  and inflation fluid for the balloon member  16  into the shaft  14 . A thumb screw  20  is threadably mounted on a proximal end of manifold  12  for use in fixing the position of guide wire  18  relative to the manifold  12 , shaft  14  and balloon member  16 . 
     The shaft  14  has an inner tube  22  (see FIG. 2) , which is preferably formed from a plastic material such as polyimide, and is attached to the manifold  12  to extend distally therefrom and define a guide wire lumen  24  for the guide wire  18 . An inner surface of the inner tube  22  is coated with a lubricous material, such as polytetrafluoroethylene, to facilitate movement of the guide wire  18  therethrough. 
     The manifold  12  has a dye injection port  26  between the thumb screw  20  and the proximal end of the inner tube  22 . The dye injection port  26  is in fluid communication with the guide wire lumen  24 , and is adapted for connection to an inflation device (not shown) to provide fluid (e.g., radiopaque dye) under pressure to the guide wire lumen  24 . 
     The shaft  14  also has an outer tube  28 , attached to the manifold  12 , which extends distally therefrom around the inner tube  22 . An annular balloon inflation lumen  30  is thus defined between the outer tube  28  and the inner tube  22 . The manifold  12  has a balloon inflation port  32  which is in fluid communication with the inflation lumen  30  and is adapted for connection to an inflation device (not shown) to provide fluid under pressure to the balloon member  16  via the inflation lumen  30 . 
     The outer tube  28  is an elongated flexible elastic tube, preferably formed of polyimide. An outer surface of the outer tube  28  has a lubricous coating, such as polytetrafluoroethylene, which provides a slippery surface to aid in inserting and removing the catheter  10  into a guide catheter and into a patient&#39;s vascular system. At a distal end  34 , outer tube  28  has a section of reduced diameter to which a proximal or waist segment  36  of balloon member  16  is attached, preferably by an adhesive seal such as epoxy. 
     Balloon member  16 , which is preferably formed from a polymer material such as polyolefin, has the proximal or waist segment  36 , a distensible balloon segment  38  and a small diameter distal segment  40 . Distal segment  40  of the balloon member  16  is bounded to a distal end  42  of the inner tube  22 , also preferably by an adhesive seal such as epoxy. A radiopaque balloon marker  43  is positioned about the inner tube  22  near a longitudinal center of the balloon member  16  at a distance D from a distal end of the catheter  10 . 
     Guide wire  18  has a proximal solid wire portion  44  which is preferably formed of a high strength steel or other high strength alloy. The solid wire portion  44  has a tapered distal end  46  which is received within and bonded to a proximal end  47  of a coil spring member  48 , preferably by a braze bond. Spring member  48  defines a distal portion of the guide wire  18 , and is formed from a multiplicity of alternating groups of radiopaque  50  and non-radiopaque  52  spring coils of a high strength steel or other high strength alloy. 
     Radiopaque markers  56  for the guide wire  10  are formed by sandwiching one or more radiopaque spring coils  50  between nonradiopaque spring coils  52 . A radiopaque tip  58  is formed at a distal end of spring member  48  by a plurality of radiopaque spring coils  50 . Proximally from the tip  58 , adjacent radiopaque markers  56  are longitudinally spaced by the same distance D as is between the distal end of the catheter  10  and its balloon marker  43 . The width of the radiopaque markers  56  will depend upon the number of radiopaque spring coils  50  used to form each marker. 
     In a preferred embodiment, the spring member  48  is 25 cm in length. The distance D between the distal end of catheter  10  and the balloon marker  43  is 1.5 cm. Thus, the radiopaque markers  56  are also separated by 1.5 cm (distance D), with the radiopaque marker  56  closest to the radiopaque tip  58  being 1.5 cm from its proximal end. The width of each radiopaque marker  56  is preferably 1 mm. The total length of the guide wire is 175 cm. 
     The basic angioplasty procedure consists of inserting an introducer sheath, or short plastic tube, into a patient&#39;s thigh which provides an opening to the femoral artery. A guide catheter (not shown) is then advanced through the vascular system and into a position at the ostium of either the left or right coronary artery. The guide catheter is a hollow tube which serves as a channel from outside the patient&#39;s body through which catheter  10  can be advanced to the ostium of a coronary artery. 
     Prior to inserting the catheter  10  into the artery, the balloon member  16  is positioned on the guide wire  18  adjacent its distal radiopaque tip  58 . Once in position, the thumbscrew  20  is tightened to fix the balloon member  16  position relative to the guide wire  18 . The balloon member  16  and guide wire  18  assembly is then advanced to the ostium of the coronary artery. Using an inflation device which is connected to the dye injection port  26  or the guide catheter, a radiopaque dye is periodically injected into the artery to allow viewing of a stenosis on a fluoroscope. The thumbscrew  20  is loosened to allow the guide wire  18  to be advanced distally across the stenosis while it can be viewed on the fluoroscope. Of course, the guide wire  18  is also viewable on the fluoroscope. The balloon member  16  remains at the ostium of the coronary artery until the guide wire  18  is advanced to a point beyond the stenosis to provide stability to the catheter  10 . 
     Once the guide wire  18  is properly advanced beyond the stenosis, a physician records the position of the stenosis relative to one of the radiopaque markers  56  on the guide wire  18 . This recording provides a reference point for the stenosis and thus the periodic injection of dye (which had been necessary to locate the stenosis) can be ceased. The guide wire  18  i then held as still as possible across the stenosis while the balloon member  16  is advanced distally over the guide wire  18 . This is done by manually grasping a proximal end of the guide wire  18  outside of the body. The balloon member  16  is advanced until its radiopaque marker  43  is aligned with the stenosis reference marker  56  of the guide wire  18 . After the balloon member  16  is properly positioned with respect to the radiopaque marker  56 , the thumbscrew  20  on the manifold  12  is tightened to prevent movement of the balloon member  16  relative to the guide wire  18 . 
     The balloon member  16  is subsequently inflated via the inflation lumen  30  so that the distensible balloon segment  38  (shown inflated) expands, exerting pressure radially and outwardly against the stenosis and causing the artery wall to stretch. Once the dilation procedure is completed, the balloon member  16  is deflated and removed, re-establishing an acceptable blood flow through the artery. 
     The radiopaque markers  56  of the guide wire  18  allow the proper placement of balloon  16  across the stenosis without the need for additional continuous or even periodic injections of dye. This is advantageous to the patient because surgical complications arise from the dye injections. Also, this method allows the operation to be performed quickly and efficiently, thereby minimizing radiation exposure to the patient and staff. 
     The inventive method is also useful in angioplasty procedures which require the use of more than one balloon dilatation catheter. For instance, balloon member  16  of catheter  10  is sometimes too large to fit through the stenosis, or conversely, is so small that upon inflation of the balloon member  16 , the stenosis is not sufficiently dilated. In these situations, balloon member  16  must be exchanged for a balloon member of a different size. If the balloon member  16  was too large to fit through the stenosis, a balloon member with a smaller profile must be used. On the other hand, if upon inflation of the balloon member  16  the stenosis was not sufficiently dilated, a balloon member with a larger inflated profile must be inserted to allow a widening of the dilated coronary artery. 
     In order to exchange balloon member  16  for a different balloon member, the guide wire  18  must be held outside the body (near the femoral artery) so that its position does not move relative to the stenosis. As the guide wire  18  is held in position, the thumbscrew  20  is loosened, allowing the balloon member  16  to be moved proximally along the guide wire  18  and out of the patient&#39;s body. The balloon member  16  is continually withdrawn until it is removed from the body and is completely removed from the proximal end of the guide wire  18 . 
     A second dilatation catheter containing a correctly sized balloon member is then placed on the proximal end of the guide wire  18  and moved distally over the guide wire  18 . The second dilatation catheter also has a radiopaque marker at a known point of its balloon member (preferably at its midpoint), and the second catheter is advanced along the guide wire  18  until the catheter&#39;s marker is aligned as desired with the recorded radiopaque marker  56  on the guide wire  18 . The position of the balloon member of the second catheter is then fixed by again tightening the thumbscrew  22 . During the entire exchange process, the physician attempts to hold the guide wire  18  steady and in place across the stenosis. If desired, dye may be injected to verify the position of the guide wire  18  and its recorded radiopaque marker  56  or the balloon member once it has been advanced to the recorded marker  56 . The second balloon member is then inflated with an inflation medium, applying pressure radially and outwardly to the artery to dilate the stenosis and re-establish an acceptable blood flow through the artery. Upon completion of the angioplasty operation, the second dilatation catheter, guide wire  18 , and guide catheter are removed from the patient&#39;s thigh. 
     By providing a guide wire with known spacings between radiopaque markers thereon, and a balloon dilatation catheter having a similar spacing known between its distal end and a radiopaque marker thereon, the positioning of the catheter balloon relative to the guide wire (which is positioned relative to the artery stenosis) is greatly facilitated. For example, if the fifth marker (from a distal end) on the guide wire is aligned across the narrowest point of the stenosis (as detected fluoroscopy), then the central marker of the balloon is moved over that fifth marker to place the balloon in the most advantageous position for inflation. As can be appreciated, once a marker on the guide wire is identified as across the stenosis, no further dye injections are necessary to align the catheter balloon, except to possibly recheck the guide wire marker location or to verify that balloon inflation has indeed dilated the artery. 
     The use of guide wire marker spacings equal to the distance from the distal end of the catheter to its balloon midpoint further assure the physician of balloon position and alignment by providing three reference points as to where the balloon member will be located when it is positioned across the stenosis. The three reference points are the fifth marker which will indicate the location of the midpoint of the balloon member, and the fourth and sixth markers on the guide wire which will indicate the location of the distal and proximal ends of the balloon member respectively. Thus, a physician can determine precisely how much of the stenosis will be contacted by the balloon member when it is inflated. 
     The balloon dilatation catheter assembly of the present invention thus has considerable advantages over those of the prior art. The invention places a plurality of radiopaque markers at a distal end of the guide wire, which in turn allows a method whereby a balloon member can be positioned properly relative to a stenosis. The radiopaque markers allow for efficient and timely placement of the balloon member without the need to constantly inject additional contrast dye. Consequently, the patient and staff are subject to less radiation exposure and the patient will have fewer complications from dye injections. 
     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.