Patent Publication Number: US-2003225434-A1

Title: Microcatheter

Description:
[0001] This invention was made with Government support under Small Business Independent Research Grant HL60320, awarded by the National Institutes of Health. The Government has certain rights in the invention. 
    
    
     
       TECHNICAL FIELD  
       [0002] This invention pertains to a catheter device. More particularly, this invention pertains to microcatheters adapted to navigate within narrow vessels such as cerebral vessels.  
       BACKGROUND  
       [0003] Strokes are the leading cause of disability among adults in the United States, and are the third leading cause of death. A stroke occurs when blood flow to one or more regions of the brain is interrupted causing brain cells to die. The extent of damage is dependent upon the part of the brain affected. Common symptoms of a stroke include loss of mental capacity, changes in vision or speech, loss of muscle control and coordination, dizziness, loss of sensation and weakness.  
       [0004] A stroke is most commonly caused by atherosclerosis. Atherosclerosis is the accumulation of plaque (i.e., fatty deposits) within blood vessels. A stroke occurs when plaque accumulates within a cerebral vessel to the extent that blood flow is substantially blocked. Blood clots that form in the brain, or emboli that become lodged in vessels of the brain, can also block blood flow to portions of the brain thereby causing a stroke. Occasionally, a stroke is caused by bleeding within the brain (e.g., rupture of a cerebral aneurysm).  
       [0005] Catheters have been developed for diagnosing and treating strokes. Since cerebral vessels are small in diameter, catheters for accessing cerebral vessels typically are relatively flexible and small in diameter. This type of catheter is often referred to as a “microcatheter.” Example microcatheters are disclosed in U.S. Pat. Nos. 5,919,171; 6,296,631; and 6,306,124.  
       SUMMARY  
       [0006] The present disclosure relates generally to catheters and catheter systems. The disclosure provides examples of different inventive concepts that may be used separately or in combination with one another. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0007]FIG. 1 illustrates a catheter that is an embodiment of one or more aspects of the present invention;  
     [0008]FIG. 2 is an enlarged view of a tip section of the catheter of FIG. 1;  
     [0009]FIG. 3 is an enlarged view of a balloon section of the catheter of FIG. 1;  
     [0010]FIG. 4 is an enlarged view of an inflation hub section of the catheter of FIG. 1;  
     [0011]FIG. 5 is an illustration of a vascular system of a human brain with a guidewire inserted within the vasculature;  
     [0012]FIG. 6 is an enlarged view of a treatment area of the brain of FIG. 5, a distal end of the guidewire is shown adjacent to the treatment area;  
     [0013]FIG. 7 illustrates the treatment area of FIG. 6 with a guide catheter placed over the guidewire;  
     [0014]FIG. 8 illustrates the treatment area of FIG. 6 with the guidewire removed from the guide catheter thereby leaving only the guide catheter;  
     [0015]FIG. 9 illustrates the treatment area of FIG. 8 with a balloon catheter inserted into the guide catheter;  
     [0016]FIG. 10 illustrates the treatment area of FIG. 9 with the balloon expanded to open an occlusion in the depicted vessel; and  
     [0017]FIG. 11 illustrates the vessel of FIG. 10 after the occlusion has been opened. 
    
    
     DETAILED DESCRIPTION  
     [0018] With reference now the various drawing figures in which identical elements are numbered identically throughout, a description of a preferred embodiment will now be provided. The embodiment illustrates examples of numerous inventive aspects. The inventive aspects are not intended to be limited to the specific examples shown and described herein, and can be practiced in other configurations as will be appreciated by one of skill in the art.  
     [0019]FIG. 1 shows an example of a catheter  20  made in accordance with the teachings of the present inventions. The catheter  20  includes a flexible distal tip  22 , a balloon  24 , an elongate body  26  and an inflation hub  28 . The flexible distal tip  22  helps guide the catheter through tortuous vessels throughout the body or through other catheters (e.g., guide catheters). The balloon  24  can be used open occluded vessels. The elongate body  26  allows the user to maneuver the distal tip  22  and defines a lumen  30  that traverses the elongate body  26 . The inflation hub  28  is on the proximal end of the catheter  20  and is used to provide fluid to the lumen  30  for inflating the balloon  24 . The inflation hub  28  also provides a grasping location for allowing a user to push the catheter to an appropriate treatment location within a patient&#39;s vasculature.  
     [0020]FIG. 2 shows an enlarged view of the distal tip  22  of the catheter  20 . The distal tip includes a distal-most end piece  32 , a flexible coil section  34  and a safety wire  36 . FIG. 2 shows the safety wire  36  connected to the distal-most end piece  32  (e.g., by an adhesive bond or other means). The distal-most end piece  32  forms a smooth, rounded tip that helps guide the catheter  20  through a vessel. The distal-most end piece  32 , in addition to providing a smooth rounded tip, connects the distal end of the coil section  34  to the safety wire  36 , which traverses the length of the distal tip  22 , and is connected to the elongate body  26 . The distal safety wire  36  protects the patient in the event the distal tip  22  breaks free of the catheter  20 . The distal-most end piece  32  is preferably made of a material such as braze, solder or adhesive.  
     [0021]FIG. 2 shows the coil section  34  of the distal tip  22  including a plurality of continuous helical rings formed by a spiral cut having a varied pitch. It should be noted, however, that this shape is an example only and the distal tip could be any shape, contain different pitches, or have no pitch at all. The depicted cut extends completely through the wall of the tubular elongate body  26 . In other embodiments, the cut can be configured so as to not penetrate completely through the wall of the elongate body  26 . The cut or cuts can be provided by any number of different techniques including laser cutting, etching, electric discharge machining, etc. Further, the term “cut” will be construed to include terms such as grooves, notches, slots, slits or other terms representative of depressions or openings provided by the removal of material from the elongate body  26 . While the distal tip  22  is shown as including continuous helical rings, it will be appreciated that separate discrete cuts such as parallel or angles cuts could also be provided. As depicted, the distal tip  22  is hollow, but could also be solid.  
     [0022]FIG. 3 shows that the coil section  34  of the tip is cut from the elongate body  26 . Thus, for example, the coil section  34  is provided by cutting a spiral cut into a solid length of tube defined at the end of the elongate body  26 . Thus, the distal tip  22  is an integral part of the elongate body  26 . By “integral”, it is meant that the distal tip  22  is unitary or made as a single seamless piece with the elongate body  26 . The material used to construct the elongate body  26  and the distal tip  22  of the catheter is, for example, a metal such as nitinol. The distal tip  22  could also be made of, coated with, be impregnated with or otherwise include a radio opaque material. It should be noted, however, that there are many materials that can be used in the present invention and this discussion relates only to the preferred embodiment by example only and in no way limits the teachings of the invention.  
     [0023] By having the distal tip  22  as an integral part of the elongate body  26 , a separate bond is not required between the distal tip  22  and the main length of the elongate body  26 . By eliminating a bond site on the elongate body  26 , a relatively high degree of flexibility can be provided, especially at the distal tip  22 . The integral connection also provides a relatively strong connection between the tip and the main portion of the elongate body  26 . Moreover, the configuration also assists in maintaining a relatively small diameter. While the integral tip is one inventive aspect disclosed herein, it will be appreciated that other inventive aspects disclosed herein may be practiced with or without a catheter having an integral distal tip.  
     [0024] Referring to FIG. 3, the balloon  24  is shown mounted immediately proximal to the distal tip  22 . The balloon  24  has distal and proximal ends  25 ,  27  that are circumferentially bonded or otherwise connected to the exterior of the elongate member  26 . An interior of the balloon  24  is in fluid communication with the lumen  30  of the elongate member  26 . For example, ports  38  are shown providing fluid communication between the lumen  30  and the interior of the balloon  24 . The balloon  24  can be made of any material conventionally used to make angioplasty balloons. For example, the balloon can be made of a polymeric material such as nylon, PET (Polyethylene Terephthalate or Polyurethane. The balloon is expandable from a deflated diameter (shown by the solid line in FIG. 3) to an expended diameter (shown by the phantom line in FIG. 3). The balloon  24  is inflated by directing fluid through ports  38  into the interior of the balloon  24 . The fluid is provided to the ports  38  by injecting fluid into the lumen  30  through the hub  28 . The balloon is deflated by withdrawing fluid from the balloon through lumen  30 . In one embodiment, the balloon has a deflated outer diameter in the range of 0.025″-0.028″, and an inflated outer diameter in the range of 1.5 mm to 3.0 mm. Preferably, the deflated outer diameter of the balloon is less than 0.028″. More preferably, the deflated outer diameter of the balloon is less than 0.025″.  
     [0025]FIG. 3 shows the safety wire  36  bonded to the elongate body  26  adjacent a proximal safety wire-bonding hole  40 . FIG. 3 also illustrates that the preferred embodiment has marker bands  42 , which overlap the distal and proximal ends  25 ,  27  of the balloon  24 . The marker bands  42  are preferably made of a relatively dense material that is X-ray visible. These marker bands are used to show where the balloon is placed relative to the area within a patient desired to be treated (e.g., via fluoroscopy or X-ray imaging).  
     [0026] Now referring to FIG. 4, the inflation hub  28  is shown. Inflation hub  24  is connected to the elongate body  26  such that the catheter  20  can be maneuvered through a vessel or guide catheter. Fluids can be delivered by way of the inflation hub through the lumen  30  of the elongate body  26  to the balloon  24 . It will be appreciated that the lumen  30  can have any number of different cross-sectional shapes. The lumen  30  is preferably blocked adjacent the balloon  24  to prevent fluids from entering the lumen through the cut of the distal tip  22 . For example, a material such as adhesive or other material can be used to provide a fluid barrier between the lumen  30  and the interior of the distal tip  22 .  
     [0027] The catheter  20  is preferably sized to allow access to relatively small vessels such as cerebral vessels or vessels of organs such as the liver. Example vessels that may be accessed include the internal carotid artery, the posterior communicating artery, the anterior choroidal artery, the middle cerebral artery, the anterior cerebral artery, the artery of hubner, vertebral artery, the basilar artery, posterior cerebral artery, the posterior choroidal artery, the superior cerebella artery, the anterior inferior cerebella artery, and the posterior inferior cerebella artery. To gain access to these types of vessels, the distal tip  22  preferably has an outer diameter in the range of 0.010″-0.014″. In a preferred embodiment, the distal tip  22  has a maximum outer diameter less than 0.014″. In a more preferred embodiment, the distal tip has a maximum outer diameter less than 0.010″. While the distal tip  22  has been depicted as having a constant outer diameter, the diameter could also be tapered or stepped.  
     [0028] To maintain a small outer diameter, it is preferred for the elongate body  26  to include only one lumen (e.g., the lumen  30  for providing fluid to the balloon). It is contemplated that other embodiments may utilize secondary lumen for receiving guidewires. However, the single lumen configuration is preferred so as to maintain the smallest outer diameter possible. In one embodiment, the lumen has a transverse cross-sectional area in the range of 0.00006-0.00007 IN 2 . This cross-sectional area is preferably large enough to allow for the efficient transfer of fluid to the balloon, but small enough for the catheter to maintain a relatively small outside diameter.  
     [0029] The main body (i.e. the portion proximal to the balloon) of the elongate member  26  also preferably has a relatively small diameter. For example, in one embodiment, the outer diameter of the main body may range from 0.012″ to 0.017″. In certain embodiments, the outer diameter of the elongate member  26  can continuously transition so as to be larger adjacent the proximal end and smaller adjacent the distal end. In other embodiments, the elongate member  26  can include several segments having different outer diameters. In such embodiments, the segments preferably step down to smaller diameters as the elongate member  26  extends toward the distal end. The inner diameter of the elongate member  26  can be constant or can vary. In one embodiment, a wall thickness of the elongate member  26  ranges from .0015″ to .004″. The inner diameter of the elongate body  26  is preferably less than 0.017 inch, more preferably less than 0.01 inch, and most preferably less than 0.005 inch. The outside diameter of the elongate body  26 , in one embodiment, ranges from 0.03 inch to 0.025 inch. Preferably, the maximum outer diameter of the elongate body  26  is less than 0.03 inches. More preferably, the maximum outside diameter of the elongate body  26  is less than 0.025 inches.  
     [0030] The catheter  20  is preferably long enough to reach a person&#39;s brain when inserted through the patient&#39;s femoral artery. In one embodiment, the length of the catheter from the distal-most tip to the base of the hub is in the range of 150 cm.  
     [0031] A lubricious coating such as a hydrophilic coating can be applied or otherwise provided on the exterior surface of the catheter  20  to facilitate insertion into a patient&#39;s vasculature. The lubricious coating assists in reducing friction in the vasculature. While a polymeric sheath or other cover could be provided over the elongate body  26 , it is preferred to not provide such a sheath so as to maintain a small outer diameter.  
     [0032] FIGS.  5 - 11  illustrate an example method for using the embodiment of FIGS.  1 - 4 . The method includes the step of inserting a guidewire into a patient and maneuvering it to a treatment area having a small vessel diameter (e.g., a cerebral vessel or a vessel of an organ such as the liver). The method also includes the step of inserting a guide catheter (also referred to as a diagnostic catheter) over the guidewire and maneuvering the guide catheter to the treatment area. The method further includes the step of removing the guidewire from within the guide catheter, and directing a catheter in accordance with the principles of the present invention through the guide catheter to the treatment site for providing treatment (e.g., balloon angioplasty) at the treatment site.  
     [0033]FIG. 5 shows a vascular system of a human brain  43 . The vascular system includes a cerebral blood vessel  46  and an occluded vessel  50 . A treatment area or site  48  is located adjacent the occlusion of the occluded vessel  50 . As shown in FIG. 5, a guidewire  44  is positioned within the blood vessel  46  with a distal end of the guidewire  44  being located at the treatment site  48  adjacent the occlusion of the occluded vessel  50 . An enlarged view of the treatment area is shown in FIG. 6.  
     [0034] Once the guidewire  44  has been navigated to the treatment area  48  as shown in FIGS. 5 and 6, a guide catheter  52  is preferably pushed over the guidewire  44  until a distal end of the guide catheter  52  is positioned in close proximity to the occlusion of the occluded vessel  50  (see FIG. 7). Once the guide catheter is positioned as shown in FIG. 7, the guidewire  44  can be removed (see FIG. 8) and a diagnostic procedure can be conducted. For example, a radiopaque fluid capable of being seen under fluoroscopy can be injected through the guide catheter  52  to the treatment area  48  such that blood flow at the treatment area  48  can be viewed under fluoroscopy or X-ray. Alternatively, it may be desirable to provide therapeutic drugs, used for clot dissolving such as Urokinase or TPA (Tissue Plasminogen Activator) to the treatment area  48 .  
     [0035] After blood flow through the treatment area  48  has been diagnosed and the exact nature of the occlusion determined, the catheter  20  can be inserted through the guide catheter  52  until the distal tip  22  reaches the occlusion of the occluded vessel  50 . Once the distal tip  22  is located at the occlusion, the distal tip  22  is preferably forced through the occlusion as shown in FIG. 9 until the balloon  24  is placed inside the occluded area of the occluded vessel  50 .  
     [0036] Once the balloon is positioned as shown in FIG. 9, balloon  24  of the catheter  20  can be inflated to enlarge the occluded area by compressing the plaque of the occlusion against the wall of the vessel (see FIG. 10). After the vessel  50  has been opened, the balloon  24  is deflated and removed from the guide catheter  52 . With the guide catheter  52  still in place, additional diagnostic procedures such as fluoroscopy or localized drug treatment can be conducted. After the final diagnostic and treatment procedures have been conducted at the treatment area  48 , the guide catheter  52  can be removed as shown in FIG. 11.  
     [0037] The above specification provides examples of numerous inventive concepts and features. It will be appreciated that the broad concepts of the present invention are not limited by the specific embodiments shown, but are instead defined by the claims attached hereto. Consequently, the principles of the present disclosure are also applicable to larger vessels, such as coronary vessels.