Patent Publication Number: US-2005124877-A1

Title: Device and method for supporting placement of a therapeutic device in a blood vessel

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention pertains to medical equipment and techniques, and more particularly, to a device and method for supporting a therapeutic device (such as a catheter) during the ablation of obstructions within tubular anatomical structures such as blood vessels.  
      2. Description of the Prior Art  
      A number of ultrasound systems and devices have heretofore been proposed for use in ablating or removing obstructive material from blood vessels. Ultrasound catheters have been utilized to ablate various types of obstructions from blood vessels of humans and animals. Successful applications of ultrasound energy to smaller blood vessels, such as the coronary arteries, requires the use of relatively small diameter ultrasound catheters which are sufficiently small and flexible to undergo transluminal advancement through the tortuous vasculature of the aortic arch and coronary tree.  
      A common problem experienced by these ultrasound catheters relates to the need for accurately positioning the ultrasound device inside a patient&#39;s vasculature, and in particular, where the vasculature contains smaller and more tortuous vessels. For example, guide catheters are typically used to assist therapeutic devices (such as angioplasty catheters, including ultrasound catheters) in accessing either left or right coronary artery sites. The guide catheters provide support for these catheters, not only during the access, but also during a therapeutic procedure. Maneuvering of therapeutic catheters and placement of these catheters at a treatment site (e.g., a lesion) is usually performed under fluoroscopy with dye injections to assess and observe the placement. During this maneuvering and placement, the catheter must be able to traverse tortuous pathways through blood vessels in the least traumatic manner possible.  
      Accurate placement of therapeutic catheters is very important from a safety perspective and helps to avoid perforations, dissections, and other unwanted MACE events. Accurate placement of therapeutic catheters is also important for efficacy and procedure time.  
      Conventional guide catheters cannot help to facilitate accurate placement of a catheter at a specific location in a blood vessel. Accurate placement sometimes requires that the catheter be rotated and manipulated when inside a vessel. However, it is often not possible to accurately place a catheter at a desired location by manipulating the catheter only. The guide catheter manipulations to facilitate the catheter placement are basically impossible due to its ostial engagement. Any manipulation of the guide catheter will cause the guide catheter to disengage from the ostium.  
      Thus, there still exists a need for a device and a method for facilitating accurate placement of a therapeutic device (such as a catheter) at a specific location in a blood vessel.  
     SUMMARY OF THE DISCLOSURE  
      It is an object of the present invention to provide a device for facilitating accurate placement of a therapeutic device at a specific location in a blood vessel.  
      It is another object of the present invention to provide a method for accurate placement of a therapeutic device at a specific location in a blood vessel.  
      It is yet another object of the present invention to provide a device for supporting the placement of an ultrasound catheter inside a blood vessel.  
      In order to accomplish the objects of the present invention, there is provided a therapeutic system that includes a guide catheter having a lumen, a sheath having an elongate body that has a lumen and an angled distal end, with the sheath extending through the lumen of the guide catheter, and a catheter extending through the lumen of the sheath. The sheath can be advanced independently beyond the distal end of the catheter, or retracted proximal from the distal end of the catheter. The sheath can also be torqued to redirect the angled distal end of the sheath. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective view of a therapeutic ultrasound system according to the present invention.  
       FIG. 2  is a perspective view of an intermediate sheath that can be used to support the placement of an ultrasound catheter of the system of  FIG. 1 .  
       FIG. 3  is a cross-sectional view of the intermediate sheath of  FIG. 2 .  
       FIG. 4A  illustrates how a catheter is placed in a conventional procedure.  
       FIGS. 4B-4E  illustrate how the sheath of the present invention supports the placement of an ultrasound catheter of the system of  FIG. 1 .  
       FIG. 5A  is an exploded cross-sectional view of the valved fitting of the system of  FIG. 1 .  
       FIG. 5B  is an assembled cross-sectional view of the valved fitting of the system of  FIG. 1 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The following detailed description is of the best presently contemplated modes of carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating general principles of embodiments of the invention. The scope of the invention is best defined by the appended claims. In certain instances, detailed descriptions of well-known devices, compositions, components, mechanisms and methods are omitted so as to not obscure the description of the present invention with unnecessary detail.  
       FIG. 1  illustrates a therapeutic ultrasound system according to the present invention for use in ablating and removing occlusive material inside the vessel of an animal or human being. The ultrasound system includes an ultrasonic catheter device  10  which has an elongate catheter body having a proximal end  14 , a distal end  16 , and defining at least one main lumen (not shown) extending longitudinally therethrough. The ultrasound catheter device  10  is operatively coupled at its proximal end  14 , by way of a Y-connector  18 , a catheter knob  20  and a slide collar  22 , to an ultrasound transducer (not shown) which is housed inside a transducer housing  24 . The ultrasound transducer is connected to a signal generator (not shown), which sends an electrical signal to the ultrasound transducer. The ultrasound transducer converts the electrical signal to ultrasound energy, which subsequently passes through the catheter device  10  and is delivered to the distal end  16 . Extending longitudinally through the main lumen is an elongate ultrasound transmission member (not shown) having a proximal end which is removably connectable to the ultrasound transducer such that ultrasound energy will pass through the ultrasound transmission member. As such, when the signal generator is actuated, ultrasound energy will pass through the ultrasound transmission member to the distal end  16  of the catheter body. A guidewire  30  may be utilized in conjunction with the catheter device  10 .  
      The ultrasound catheter device  10  can be embodied in the form of any known ultrasound catheter, and will not be described in greater detail herein. Examples of catheter devices  10  that can be utilized in the present invention are illustrated in U.S. Ser. No. 10/211,418, filed Aug. 2, 2002, and entitled “Therapeutic Ultrasound System”, and U.S. Ser. No. 10/601,245, filed Jun. 20, 2003, and entitled “Therapeutic Ultrasound System”, whose disclosures are incorporated by this reference as though set forth fully herein.  
      The frontal portion of the Y-connector  18  is connected to the proximal end  14  of the catheter  10  using techniques that are well-known in the catheter art. An injection pump (not shown) or IV bag (not shown) or syringe (not shown) can be connected, by way of an infusion tube, to an infusion port or sidearm  26  of the Y-connector  18 . The injection pump can be used to infuse coolant fluid (e.g., 0.9% NaCl solution) into and/or through the main lumen of the catheter  10 . Such flow of coolant fluid may be utilized to prevent overheating of the ultrasound transmission member extending longitudinally through the main lumen. Such flow of the coolant fluid through the main lumen of the catheter  10  serves to bathe the outer surface of the ultrasound transmission member, thereby providing for an equilibration of temperature between the coolant fluid and the ultrasound transmission member. Thus, the temperature and/or flow rate of coolant fluid may be adjusted to provide adequate cooling and/or other temperature control of the ultrasound transmission member. For example, the coolant temperature at the distal end  16  of the catheter  10  is preferably in the range of 35-45 degrees Celsius, and is preferably less than 50 degrees Celsius, since tissue de-naturalization normally occurs above 50 degrees Celsius.  
      In addition to the foregoing, the injection pump or syringe may be utilized to infuse a radiographic contrast medium into the catheter  10  for purposes of imaging, as described in greater detail below. Examples of iodinated radiographic contrast media which may be selectively infused into the catheter  10  via the injection pump are commercially available as Angiovist 370 from Berlex Labs, Wayne, N.J. and Hexabrix from Malinkrodt, St. Louis, Mo.  
      The proximal end of the Y-connector  18  is attached to the distal end of the catheter knob  20  by threadably engaging the proximal end of the Y-connector  18  inside a threaded distal bore (not shown) at the distal end of the catheter knob  20 . The construction of the catheter knob  20  and the transducer housing  24  can be same as that illustrated in U.S. Ser. No. 10/666,459, filed Sep. 19, 2003, and entitled “Connector for Securing Ultrasound Catheter to Transducer”, whose disclosure is incorporated by this reference as though set forth fully herein. For example, a sonic connector assembly is housed inside the catheter knob  20  for effectively connecting the ultrasound transmission member to the transducer in a manner which reduces step sonic amplification and provides a smooth connection transition of the transmission member, thereby reducing the stress and fatigue experienced by the transmission member.  
      Referring still to  FIG. 1 , the ultrasound system further includes an intermediate sheath  34  that is adapted to receive the catheter device  10 , and a guide catheter  36  that is adapted to receive the intermediate sheath  34  inside the main lumen of the guide catheter. The guide catheter  36  can be any conventional guide catheter, and shall not be described in greater detail herein.  
      Referring to  FIGS. 2 and 3 , the sheath  34  has an elongate body  38  with a main lumen  46  extending therethrough for receiving the ultrasound catheter  10 . The elongate body  38  has a preshaped angled distal end  40  and a valved fitting  42  provided at the proximal end  44 . The distal end  40  is angled by an angle of between 10 degrees and 90 degrees. The angled distal end  40  facilitates the redirection of the ultrasound catheter  10  disposed inside the main lumen  46 , which can be controlled by applying a torque input (see arrows  48  in  FIG. 2 ) to the proximal end  44 . This torque input is transmitted to a torque output (see arrows  50  in  FIG. 2 ) at the distal end  40 . The operation of the sheath  34  will be described in greater detail hereinbelow.  
      Referring to  FIGS. 5A and 5B , the valved fitting  42  is connected to the proximal end  44  of the elongate body  38  by adhesive bond. The valved fitting  42  functions to prevent backflow of blood out of the sheath  34  and around the ultrasound catheter  10  at its proximal end  14 . The valved fitting  42  has a distal portion  81  which is connected to the sheath  34  at its proximal end  44  by a conventional glue bond. The distal portion  81  has an inner bore  82 . A standard O-ring  83  (which can be made of rubber or silicone) is positioned inside the bore  82 . A proximal cup  4  is positioned on the end of the valved fitting  42 . The distal portion  81  and the proximal cup  84  are connected together via internal threads  85  positioned inside the bore  82  and external threads  86  positioned on the proximal cup  84 .  
      Threading the distal portion  81  and the proximal cup  84  together will squeeze the O-ring  83 , thereby providing a seal around the catheter  10  which is extended through the bore  82 .  FIG. 5B  illustrates the fully assembled sheath  34 .  
      Referring to  FIG. 3 , the elongate body  38  includes a main shaft member  60  that can be formed of an outer polymeric material  62  having a reinforcing layer  64  embedded therein. The reinforcing layer  64  can be a braid, a coil, a double coil, an opposite wound coil, or the like. The reinforcing layer  64  can be embodied in the form of stainless steel or a superelastic alloy. An inner lubricious polymeric material  69  lines the inner walls of the main lumen  46 . The elongate body  38  also includes a distal shaft member  68  extending distal of the main shaft member  60 , with the outer diameter of the distal shaft member  68  being smaller than the outer diameter of the main shaft member  60 . This is because a smaller diameter provides a lower profile of the sheath  34  on its distal end for better access to a tortuous blood vessel. The distal shaft member  68  can be formed of a polymeric material  70  that is free of any reinforcements. The distal end  40  is angled, with the length of the angled portion being about 5 mm to 30 mm. The hardness of the polymeric material  70  at the distal shaft member  68  can be the same as the hardness of the polymeric material  62  at the main shaft member  60 . Examples of the polymeric materials  62 ,  70  can include, but are not limited to, nylon and urethane. The outer surface of the elongate body  38  can be coated with a lubricious coating  76  to facilitate smooth tracking of the sheath  34  through the lumen of the guide catheter  36  and the vasculature of the patient.  
      In use, the catheter  10  is positioned inside the lumen  46  of the sheath  34 , and the combined catheter  10  and sheath  34  is introduced into the vasculature of a patient over a guide wire  30  through a conventional guide catheter  36 . As the combined catheter  10  and sheath  34  is advanced through the vasculature, the sheath  34  may be independently advanced distally to or beyond the distal tip of the catheter  10  when additional support or redirection is needed. Alternatively, the sheath  34  may be retracted proximal from the distal tip of the catheter  10  if needed.  
       FIGS. 4A-4E  illustrate how the sheath  34  can facilitate accurate placement of the catheter  10 .  FIG. 4A  illustrates the conventional placement of a catheter  10  without the sheath  34 . In this case, the catheter  10  typically prefers to track into vessels or branches that are straight ahead of it. Therefore, it would be difficult to navigate the catheter  10  into one of the branches shown in  FIG. 4A . On the other hand, as shown in  FIGS. 4B and 4C , the elongated body  38  of the sheath  34  can be torqued so that the angled distal end  40  can be easily navigated into a branch. Then, as shown in  FIGS. 4D and 4E , the catheter  10  can be steered or directed by the enclosing sheath  34  into the desired branch. Here, the sheath  34  can be rotated independently by 360 degrees and its angled distal end  40  positioned in a desired branch location.  
      Although the present invention is being described in connection with an ultrasound catheter  10 , the catheter  10  can be any type of catheter, including but not limited to a balloon angioplasty catheter, an atherectomy catheter, or diagnostic catheters, among others.  
      While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention.