Abstract:
Apparatus and methods for manufacturing a guidewire having a plurality of radiopaque markers are disclosed. In a preferred embodiment, the present invention provides a guidewire having a tapered distal section comprising a plurality of gold markers that are deposited on the guidewire at predetermined intervals, so that the outer surface of the guidewire is substantially smooth. The gold markers provide a fluoroscopic reference for positioning the guidewire and enable accurate sizing of vessel features, such as the length of a lesion.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to improved apparatus for measuring features of vessels. More specifically, the present invention provides a guidewire having a plurality of radiopaque markers useful for sizing the length of a lesion, e.g., within coronary arteries.  
         BACKGROUND OF THE INVENTION  
         [0002]    Patients suffering from atherosclerosis may undergo angioplasty, a procedure involving the use of a balloon-tipped catheter that dilates occluded vessels by compressing atherosclerotic plaque against the vessel wall. Further benefits may be realized if the patient additionally undergoes stenting, a process involving the deployment of tubular prostheses that hold the occluded vessel open and help restore adequate blood flow to the region.  
           [0003]    Guidewires having relatively small diameters and flexible coiled tips may be used to transluminally navigate the tortuous anatomy and locate lesions prior to insertion of the catheter. Additionally, guidewires may be used to size vascular lesions prior to performing interventional procedures to determine the size of the angioplasty balloon or stent to be used in treating the lesion. Accurately assessing the three-dimensional size of a lesion requires a physician to account for lesions that partially extend into a third dimension not visible on a two-dimensional fluoroscopy screen.  
           [0004]    Several previously-known guidewires have been introduced for use in positioning balloon catheters within a vessel and/or sizing vessel characteristics. U.S. Pat. No. 5,174,302 to Palmer describes a guidewire having an initially uniform core section that tapers inward along a distal segment. The distal segment is surrounded by a flexible spring tip that is banded to define portions that are highly radiopaque and portions that are much less radiopaque. The radiopaque bands provide a reference for the physician with regard to positioning the guidewire within the cardiovascular system when used in conjunction with an x-ray imaging system.  
           [0005]    The previously known device described in the foregoing patent has several drawbacks. First, despite having a tapered distal segment of core wire, the overall diameter of the guidewire is substantially equal along its length because the radiopaque-banded spring that wraps around the distal segment adds to the core wire diameter and negates the tapering effect. It therefore would be beneficial to provide a guidewire having a reduced distal diameter that facilitates use in smaller vessels.  
           [0006]    Another drawback associated with the device described in the Palmer patent is that the radiopaque markers are disposed in the coiled spring. While it may be desirable to simultaneously provide the radiopaque guidewire within the stenosis, e.g., as a reference point throughout a stenting procedure, the Palmer device may be difficult to track in real time under fluoroscopy. This is because a distal coil is typically advanced through and disposed distal to the stenosis, not disposed within the stenosis itself, which may make the coil difficult to view throughout the procedure.  
           [0007]    Cook Incorporated offers a measuring guidewire under the tradename GRADUATE®, for use in sizing vessel lumens prior to angioplasty and other interventional procedures. This product has six distal gold markers spaced 1 cm apart and four proximal markers spaced at 5 cm intervals disposed on the distal end of the guidewire.  
           [0008]    One drawback associated with the Cook guidewire is its relatively large diameter. The guidewire diameter is 0.035 inches, and therefore is not suitable for use in coronary arteries. Additionally, the gold marker bands are affixed to the outer diameter of the guidewire, and result in an increased diameter that forms a potentially uneven surface.  
           [0009]    In view of these drawbacks of previously known guidewires, it would be desirable to provide a guidewire having radiopaque markers suitable for accurately sizing the length of a feature, e.g., a lesion, within a vessel.  
           [0010]    It also would be desirable to provide a guidewire having radiopaque markers that is suitable for insertion into smaller vessels, e.g., coronary arteries.  
           [0011]    It still further would be desirable to provide a guidewire having radiopaque markers that form a substantially smooth surface along the guidewire such that the bands do not increase the diameter of the guidewire or create a jagged surface.  
         SUMMARY OF THE INVENTION  
         [0012]    In view of the foregoing, it is an object of the present invention to provide a guidewire having radiopaque markers suitable for accurately sizing the length of a lesion within a vessel.  
           [0013]    It is also an object of the present invention to provide a guidewire having a plurality of radiopaque markers that is suitable for insertion into smaller vessels, e.g., coronary arteries.  
           [0014]    It is further an object of the present invention to provide a guidewire having a plurality of radiopaque markers that form a substantially smooth surface along the guidewire such that the bands do not increase the diameter of the guidewire or create an uneven surface.  
           [0015]    These and other objects of the present invention are accomplished by providing a guidewire having proximal and distal sections, and a plurality of radiopaque markers disposed along the distal section at predetermined intervals. The markers may be evenly spaced, for example, 10 mm apart, to enable a physician to accurately assess the size of a vessel feature, such as a lesion.  
           [0016]    In a preferred embodiment, the guidewire comprises a core wire having a constant diameter proximal section and a tapered distal section having a plurality of radiopaque marker bands, preferably inset into indentations formed in the outer surface of the core wire to provide a substantially smooth surface. The guidewire also may include a lubricious surface, such as polytetrafluoroethelene (“PTFE”) disposed on its outer surface.  
           [0017]    The guidewire of the present invention is manufactured by first masking the tapered distal section of core wire. The desired locations for the radiopaque markers then are selected, and the mask removed from the core wire at those selected locations to expose the core wire, e.g., by mechanically abrading or chemically removing the masking. A radiopaque material, preferably gold, then is deposited, such as by electroplating or vacuum deposition, on the distal section so that the selected, exposed regions of core wire are coated, while the mask prevents coating of other regions of the core wire. The mask then is removed.  
           [0018]    Preferably, small indentations may be provided in the core wife, e.g., by grinding or chemically etching the core wire prior to deposition of the radiopaque material, so that no additional diameter is added to the guidewire. A lubricious coating then may be applied to further ensure a smooth, nonstick surface.  
           [0019]    In an alternative embodiment, a sheath having a plurality of radiopaque markers disposed at predetermined intervals along its distal section may be used in combination with a traditional guidewire. In this embodiment, the traditional guidewire navigates the tortuous vasculature and crosses the lesion, then the sheath is distally advanced over the guidewire and the length of the lesion is assessed using the radiopaque markers of the sheath.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments, in which:  
         [0021]    [0021]FIG. 1 illustrates a guidewire constructed in accordance with the principles of the present invention;  
         [0022]    [0022]FIG. 2 illustrates the apparatus of the present invention positioned within an occluded vessel;  
         [0023]    FIGS.  3  describe a method of manufacturing apparatus in accordance with the present invention; and  
         [0024]    FIGS.  4  describe an alternative embodiment for measuring features of a vessel using a sheath having a plurality of radiopaque markers; and  
         [0025]    FIGS.  5  describe an alternative embodiment for measuring features of a vessel using a sheath in a rapid-exchange manner. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0026]    Referring to FIG. 1, guidewire  20  constructed in accordance with principles of the present invention is described. Guidewire  20  comprises core wire  30  having proximal section  22 , distal section  24 , and optionally, reduced diameter distalmost section  33 .  
         [0027]    Along proximal section  22 , core wire  30  spans a length L 1  that comprises the majority of the overall length of guidewire  20 . Proximal section  22  may comprise a constant diameter d 1 , preferably 0.014 inches. Along distal section  24 , core wire  30  may taper inward gradually over a length L 2 . In a preferred embodiment, L 2  spans approximately 30 cm, and core wire  30  tapers uniformly to a final diameter d 2 , preferably about 0.005 inches.  
         [0028]    Distal section  24  comprises plurality of radiopaque markers  28 . In a preferred embodiment, radiopaque markers  28  are spaced at equal intervals L 4 , for example, spaced apart 10 mm center-to-center, and the markers are 1 mm in length, as represented by length L 5 . Radiopaque markers  28  preferably consist of a gold layer that is electroplated or otherwise deposited onto core wire  30  according to manufacturing techniques described hereinbelow.  
         [0029]    Guidewire  20  may further comprise a reduced diameter, distalmost section  33  having core wire diameter d 3 . Core wire diameter d 3  preferably is between about 0.001 and 0.003 inches. Coil  26  may be affixed to distalmost section  33 , such that the added diameter of coil  26  to reduced core wire diameter d 3  does not substantially increase the overall diameter of section  33  relative to diameter d 2 .  
         [0030]    Referring to FIG. 2, guidewire  20  constructed in accordance with the present invention is depicted within a vessel V, for example, a coronary artery, having a lesion S that spans a length L 6 . Radiopaque markers  28  of guidewire  20  may be used to measure the length of lesion S under fluoroscopy since the markers are spaced at known, and preferably equal, intervals. For example, the appearance of four radiopaque markers  28  along the length of lesion S may translate into a lesion that is approximately 40 mm in length, assuming that markers  28  are equally spaced at 10 mm intervals, center-to-center.  
         [0031]    Advantageously, several radiopaque markers may be provided along distal section  24  to better assess the characteristics of vessel V. The number of radiopaque markers is dependent on the overall length of tapered distal section  24  and the spacing intervals, L 4 . In a preferred embodiment, when tapered distal section  24  spans 30 cm and radiopaque markers  28  are equally spaced 10 mm apart, core wire  30  may accommodate approximately  30  markers.  
         [0032]    Referring to FIGS. 3, a method of manufacturing apparatus in accordance with principles of the present invention is described. Guidewire  20  comprises a length of core wire  50  having an initially constant diameter along proximal section  52  and distal section  54 . In a preferred embodiment, the initial diameter of core wire  50  is 0.014 inches. Distal section  54  of core wire  50  then is taper-ground such that its diameter gradually decreases, as shown in FIG. 3A. The taper preferably spans the distal 30 cm of core wire  50  and tapers from 0.014 to 0.005 inches.  
         [0033]    Distal section  54  of core wire  50  then is coated using a masking  56 , for example, FEP (Fluorinated Ethylene-Propylene), silicone rubber, paint or another method, as shown in FIG. 3B. A distalmost section L 3  may be set aside, i.e., neither tapered nor masked, for the purpose of subsequently adhering a coil to the distal end of the guidewire.  
         [0034]    Once distal section  54  is masked, the desired locations for the radiopaque markers may be selected. Mask  56  then is removed primarily at the selected locations, e.g., by scraping, abrading or chemically removing the mask at the selected locations, such that distal section  54  comprises exposed regions  58  and masked regions  60 , as shown in FIG. 3C. The dimensions and locations of exposed regions  58  are selected based on the desired positioning of the radiopaque markers, and are preferably 1 mm in length and spaced 10 mm apart, center-to-center.  
         [0035]    A radiopaque material, preferably gold, then is deposited on distal section  54  at exposed regions  58 , for example, by electroplating or vacuum deposition, while masked regions  60  prevent coating of unwanted regions of core wire  50 . More preferably, exposed regions  58  may be reduced in diameter, e.g. by grinding or chemically etching, to form indentations prior to deposition of the radiopaque material. In this manner, the finished guidewire will have a substantially smooth outer surface, with the radiopaque markers substantially flush with the outer diameter of the core wire.  
         [0036]    The remaining mask that covers the masked regions  60  then may be removed, either by use of dissolving chemicals or scraping the layer of masking. Upon removal of the remaining masking, distal section  54  of guidewire  20  comprises radiopaque markers  58  and non-radiopaque regions  59  of core wire  50 , as shown in FIG. 3D.  
         [0037]    Distalmost section L 3  then may be flattened to form reduced diameter distalmost section  55 , as shown in FIG. 3D. The diameter of distalmost section  55  preferably is between about 0.001 and 0.003 inches. The reduced core wire diameter along distalmost section  55  allows coil  62  to be affixed to core wire  50  such that it does not substantially increase the diameter relative to the diameter provided at the distal end of section  54 , which is preferably 0.005 inches. Adhesive  64 , e.g., a solder or weld, may be used to affix coil  62  to section  55  of core wire  50 , as shown in FIG. 3E.  
         [0038]    Coil  62  is configured to transluminally guide apparatus  20  through tortuous vasculature and into the selected vessel. Coil  62  preferably comprises a radiopaque material, e.g., platinum, to facilitate fluoroscopic guidance of the device. Coil  26  may overlap exclusively with section  55  of core wire  50 , or may extend distally beyond core wire  50 . Alternatively, reduced diameter distalmost section  55  may be omitted and coil  62  may be affixed directly to the distal end of section  54 .  
         [0039]    A lubricious coating, preferably, e.g., polytetrafluoroethylene (“PTFE”) is applied to core wire  50  to ensure a smooth surface suitable for vascular insertion.  
         [0040]    Although the marker bands of the present invention are illustratively depicted as circumferential bands, one of ordinary skill in the art will recognize that the sizes and shapes of the radiopaque markers may vary. For example, the radiopaque markers may comprise rectangular shapes, circular shapes, or irregular banded shapes that extend circumferentially around core wire.  
         [0041]    Referring to FIGS.  4 , alternative apparatus and methods for measuring features of vessels are described. In FIG. 4A, sheath  80  having proximal and distal sections comprises plurality of radiopaque markers  82  disposed at predetermined intervals along the distal section. In this embodiment, the proximal end of sheath  80  communicate with proximal hub  84 . In a preferred embodiment, radiopaque markers  82  are spaced at equal intervals L 8 , for example, spaced apart 10 mm center-to-center, and the markers are 1 mm in length, as represented by L 7 . Radiopaque markers  82  preferably consist of a gold layer that is electroplated or otherwise deposited onto sheath  80 , according to manufacturing techniques described in FIGS.  3 B- 3 D hereinabove. Using such techniques, sheath  80  will have a substantially smooth outer surface, with radiopaque markers  82  being substantially flush with outer diameter d 4  of sheath  80 . Sheath  80  preferably comprises a material used in catheter construction, such as polyethylene or polyimide, and has a wall thickness of about 0.001 to 0.005 inches.  
         [0042]    Sheath  80  of FIG. 4A is used in combination with a previously known guidewire having proximal and distal ends to measure features of a vessel. In a first method step, the distal end of traditional guidewire  90  is transluminally inserted into occluded vessel V. The distal end of traditional guidewire  90  preferably crosses lesion S and is ultimately positioned distal to lesion S, as shown in FIG. 4B. The distal end of traditional guidewire  90  preferably comprises coil  92  configured to transluminally navigate tortuous vasculature.  
         [0043]    Sheath  80 , having an inner diameter slightly larger than the outer diameter of guidewire  90 , then is distally advanced over guidewire  90  and positioned within lesion S, as shown in FIG. 4C. Radiopaque markers  82  may be used to measure the length of lesion S under fluoroscopy since the markers are spaced at known, and preferably equal, intervals. Radiopaque markers  82  allow a physician to accurately assess L 7 , even though lesion S may partially extend into a third dimension not visible under two-dimensional fluoroscopy. Upon sizing L 7 , sheath  80  may be removed from the patient&#39;s body and an appropriately-sized angioplasty balloon catheter or stent may be delivered to the site of the lesion via guidewire  90 .  
         [0044]    Referring to FIGS.  5 , apparatus and methods suitable for using a measuring sheath in a rapid-exchange manner are described. In FIG. 5A, sheath  100  comprises plurality of radiopaque markers  102  disposed at predetermined intervals along its length. Sheath  100  and radiopaque markers  102  are provided in accordance with manufacturing techniques described hereinabove. Sheath  100  is coupled to push wire  104 , e.g., a stainless steel wire or shaft having an outer diameter of about 0.014 inches, that is suitable for transmitting forces to sheath  100 . Push wire  104  preferably spans a substantially greater length than sheath  100 , and the proximal end of push wire  104  communicates with proximal hub  106 .  
         [0045]    Sheath  100  of FIG. 5A may used in combination with a previously known guidewire having proximal and distal ends to measure features of a vessel. In a first method step, the distal end of traditional guidewire  110  is transluminally inserted into occluded vessel V. The distal end of traditional guidewire  110  preferably crosses lesion S and is ultimately positioned distal to lesion S, as shown in FIG. 4B.  
         [0046]    Sheath  100 , having an inner diameter slightly larger than the outer diameter of guidewire  110 , is positioned over the proximal end of guidewire  110 . Push wire  104  then is advanced distally and causes sheath  100  to translate distally. Sheath  100  is ultimately positioned within lesion S, as shown in FIG. 4C, and radiopaque markers  102  may be used to measure the length of lesion S under fluoroscopy. The use of push wire  104  advantageously permits guidewire  110  to have a relatively small length, i.e., spanning approximately from the site of the lesion to a location just outside of the patient&#39;s body, such that the apparatus may be used in a rapid-exchange manner. Push wire  104  then may be retracted proximally to remove sheath  100  from the patient&#39;s body upon completion of the step of measuring the vascular feature.  
         [0047]    While preferred illustrative embodiments of the invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention. The appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.