Patent Publication Number: US-2005131446-A1

Title: Catheter with protected occlusion balloon

Description:
FIELD OF THE INVENTION  
      This invention relates generally to catheter systems used in treatment of stenoses within blood vessels. More specifically, the invention relates to a catheter having a distal occlusion balloon that is protected against damage by a treatment instrument proximal to the occlusion balloon.  
     BACKGROUND OF THE INVENTION  
      Human blood vessels often become narrowed or blocked by atherosclerotic plaque, thrombi or other deposits. Such stenoses reduce the blood-carrying capacity of the vessel and can cause serious and permanent injury, even death. When significant stenosis is detected, medical interventions are performed to prevent major adverse events such as myocardial infarction, stroke or death. Besides surgical modalities, there are less-invasive transluminal catheterization techniques, such as balloon angioplasty, atherectomy, deployment of stents and introduction of medication by infusion. These catheter-based treatments carry a risk of dislodging particles of the stenotic material, which can move downstream to cause an embolism. Thus, there is a need to contain and remove such embolic debris.  
      Systems of catheters and/or guidewires are used in the treatment of stenoses and emboli containment within blood vessels. Before moving an interventional catheter into a stenosis, a distal protection catheter can be advanced through the stenosis into a position such that an occlusion balloon can be inflated distal to the stenosis. The distal protection catheter typically also serves as a guidewire for a treatment catheter that slides there over. As described in U.S. Pat. No. 6,569,148, for example, an inflated distal occlusion balloon can block distal blood flow to prevent distal embolization by particulate debris entrained in the blood. Such occlusion balloons are thin-walled and fragile, and are subject to damage from treatment catheters approaching from the proximal side of the balloon. It is challenging to avoid such contact with occlusion balloons because catheterization procedures take place under the visual limitations of fluoroscopy, sometimes in the coronary arteries of a beating heart. The consequence of damage to an occlusion balloon may be that it leaks and deflates, releasing any captured embolic particles, thus defeating the purpose of the distal protection catheter. It is desirable to protect a distal occlusion balloon from being damaged by a treatment catheter approaching from the proximal side of the occlusion balloon.  
     SUMMARY OF THE INVENTION  
      The present invention addresses the need to prevent treatment instruments from sliding forward into contact with the occlusion balloon of a distal protection catheter. It will be appreciated that, as used herein, the term “catheter” is broadly used to refer to a number of medical instruments, including without limitation, occlusion catheters or guidewires, therapy catheters and the like.  
      One aspect of the present invention provides a catheter for treating a vascular condition. The catheter includes an elongate catheter shaft, an occlusion balloon disposed on a distal region of the catheter and a stop member disposed on the catheter shaft proximal the occlusion balloon.  
      A second aspect of this invention provides a system for treating a vascular condition including an occlusion balloon catheter having a stop member disposed on the catheter proximal the occlusion balloon, and a treatment instrument.  
      The present invention is illustrated by the accompanying drawings of various embodiments and the detailed description given below. The drawings should not be taken to limit the invention to the specific embodiments, but are for explanation and understanding. The detailed description and drawings are merely illustrative of the invention rather than limiting, the scope of the invention being defined by the appended claims and equivalents thereof. The foregoing aspects and other attendant advantages of the present invention will become more readily appreciated by the detailed description taken in conjunction with the accompanying drawings. The drawings are not to scale. In all the figures, like elements share like reference numbers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a perspective illustration of a catheter having an uninflated protected occlusion balloon, in accordance with a first embodiment of the current invention;  
       FIG. 2  is a perspective illustration of a catheter having an inflated protected occlusion balloon, in accordance with the first embodiment of the current invention;  
       FIG. 3  is a perspective illustration of a catheter having an inflated protected occlusion balloon, in accordance with a second embodiment of the current invention;  
       FIG. 4  is a perspective illustration of a catheter having an uninflated protected occlusion balloon, in accordance with a third embodiment of the current invention;  
       FIG. 5  is a perspective illustration of a catheter having an inflated protected occlusion balloon, in accordance with the third embodiment of the current invention;  
       FIG. 6  is a perspective illustration of a catheter having an uninflated protected occlusion balloon, in accordance with a fourth embodiment of the current invention;  
       FIG. 7  is a perspective illustration of a catheter having an inflated protected occlusion balloon, in accordance with a fourth embodiment of the current invention;  
       FIG. 8  is a side view of a catheter having an uninflated protected occlusion balloon, in accordance with a fifth embodiment of the current invention;  
       FIG. 9  is a side view of a catheter having an inflated protected occlusion balloon, in accordance with a fifth embodiment of the current invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIGS. 1 and 2  are perspective illustrations of system  10  for treating a vascular condition such as stenosis  100  in vessel  30 , in accordance with a first embodiment of the current invention. System  10  includes catheter  15  having an inflation lumen (not shown) there through. Occlusion balloon  20  is mounted about distal region  16  of catheter  15  and is in fluid communication with the inflation lumen through one or more inflation ports, which may be round, oval, or helical in shape, such as spiral cut openings  17 . The inflation lumen originates at the proximal end of catheter  15  and may terminate at the inflation port(s) or extend there beyond to a sealed distal end. Catheter  15  may also have a guidewire lumen extending end-to-end in an over-the-wire embodiment, or the guidewire lumen may extend through only relatively short distal region  16  in a rapid exchange embodiment.  
       FIG. 1  illustrates occlusion balloon  20  in an uninflated condition, wherein occlusion balloon  20  may be snugly collapsed about the shaft of catheter  15 . Occlusion balloon  20  may be made from flexible biocompatible materials having a wide range of elasticity. Such materials may include thermoplastic elastomers, including styrenic TPEs such as styrene-ethylene-butylene-styrene (C-FLEX). Other suitable materials for occlusion balloon  20  are natural rubbers (latex), synthetic rubbers (silicone), or less elastic polymers such as polyesters, polyolefins, polyamides, polyvinyl chloride, and combinations of the above, such as block copolymers. If a relatively inelastic material is used to make occlusion balloon  20 , its uninflated condition may include folds or “wings.” Conversely, an uninflated elastic balloon will collapse tightly about catheter  15  without any folds.  
       FIG. 2  illustrates occlusion balloon  20  inflated into apposition against the inner wall of vessel  30  to block the flow of blood and any embolic material entrained therein. When inflated without constraint, occlusion balloon  20  may be spherical or elongate in shape. Occlusion balloon  20  can be mounted to catheter  15  with adhesive, and with or without clamp rings, as will be understood to those of skill in the field of balloon catheters.  
      System  10  for treating a vascular condition also includes conical stop member  40  mounted about distal region  16  at a location proximal to occlusion balloon  20 . Conical stop member  40  comprises a frustum of a cone with its base facing in the proximal direction (to the left in all figures). Conical stop member  40  may be a hollow rigid funnel, a hollow collapsible funnel or, a solid frustum of a cone. Conical stop member  40  may be spaced a relatively short distance from balloon proximal end  23 , as shown in  FIGS. 1 and 2 . Alternatively, stop member  40  may be contiguous with proximal end  23  of occlusion balloon  20  to minimize the axial space along distal region  16  occupied by combined occlusion balloon  20  and stop member  40 .  
      Conical stop member  40  may be formed of material selected from the group consisting of polyolefins, ethylene vinyl acetate (EVA), polyamides, polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), ionomer (SURLYN), polyethylene block amide copolymer (PEBA), and urethanes.  
      The shaft of catheter  15  may be formed of various polymeric materials commonly used for catheter construction. For catheter  15  to also be used as a guidewire for treatment catheters, it may preferably be formed of a hypotube comprising metal such as stainless steel or TiNi (nitinol), and it may also have a flexible distal tip such as a coil spring (not shown). Catheter  15  may also be provided with a coating on its outer surface. Slippery coatings may be hydrophilic or hydrophobic, such as TEFLON or a silicone composition. Antithrombogenic coatings such as heparin compounds may also be used. Suitable coatings and their application methods are well known in the art. Additional details relative to the catheter systems described herein may be found in U.S. Pat. No. 6,569,148.  
      During treatment of a patient, catheter  15  may be advanced through the patient&#39;s vasculature, such as vessel  30 , until occlusion balloon  20  and stop member  40  are positioned distal to stenosis  100 . As illustrated in  FIG. 2 , catheter  15  can perform the function of a guidewire to direct treatment instrument  60  into and across stenosis  100 . As mentioned above, treatment instrument  60  may be an interventional catheter for angioplasty, atherectomy, stent deployment, infusion of medication, or aspiration of blood that may be contaminated with dislodged particles from stenosis  100 . Before advancing treatment catheter  60  along catheter  15  into and through stenosis  100 , occlusion balloon  20  is inflated by the delivery of a fluid through the inflation lumen of catheter  15  and inflation ports such as spiral cuts  17 . The inflation fluid may be a dilute radiopaque contrast solution or CO 2  gas.  
      The annular space between catheter  15  and treatment instrument  60  may, optionally, be large enough to provide an intermediate pathway for irrigation, infusion of drugs or aspiration of the treatment area. Stop member  40  has an outer diameter large enough to prevent treatment instrument  60  from sliding forward into contact with occlusion balloon  20 . If treatment instrument  60  slides along catheter  15  distally of stenosis  100 , then conical stop member  40  stops the distal movement of treatment instrument  60  before it can contact, and possibly damage, occlusion balloon  20 . If occlusion balloon  20  were to be damaged during treatment of stenosis  100 , then occlusion balloon  20  could deflate unexpectedly, thus permitting the unplanned resumption of blood flow, which may carry any captured embolic particles downstream to embolize. During a normal treatment, static blood containing any dislodged particles is aspirated after use of treatment catheter  60 . Then, occlusion balloon  20  is deflated to allow uncontaminated blood to begin flowing again, and system  10  is removed from the patient.  
       FIG. 3  is a perspective illustration of system  11  for treating a vascular condition, in accordance with a second embodiment of the current invention. In system  11 , the stop member is stop ring  45  mounted on catheter  15  proximal to occlusion balloon  20 . Stop ring  45  prevents treatment instrument  60  from sliding forward into contact with occlusion balloon  20 . Stop ring  45  may be formed from biocompatible materials having sufficient hardness to resist deformation by an abutting treatment instrument  60 . Examples of such materials include polyolefins, ethylene vinyl acetate (EVA), polyamides, polyesters, ionomers, PEBAX, urethanes, or metals that are radiopaque or radiolucent. Comparable to the first embodiment described above, stop ring  45  may be spaced a relatively short distance from balloon proximal end  23 , as shown in  FIG. 3 , or stop ring  45  may be contiguous with proximal end  23  of occlusion balloon  20 .  
       FIGS. 4 and 5  are perspective illustrations of system  12  for treating a vascular condition, in accordance with a third embodiment of the current invention. In system  12 , the stop member is stop balloon  50  mounted around catheter  15  proximal to occlusion balloon  20 . Stop balloon  50  is in fluid communication through first port  19  with an inflation lumen (not shown) extending through catheter  15 . As in previously described embodiments, occlusion balloon  20  is in fluid communication via second port  18  with an inflation lumen through catheter  15 . Catheter  15  may include separate inflation lumens, or occlusion balloon  20  and stop balloon  50  may be in fluid communication with, and may be inflated through, a single inflation lumen.  FIG. 4  shows occlusion balloon  20  in an uninflated condition, and  FIG. 5 . shows occlusion balloon  20  in an inflated condition. When inflated, occlusion balloon  20  may be in apposition with the inner walls of vessels  30  as small as 2 to 4 mm in diameter, although the present invention can be made for use within larger vessels. Preferably, the uninflated profile of stop balloon  50  is no larger than the uninflated profile of occlusion balloon  20 .  
      Stop balloon  50  is conveniently inflatable and deflatable, like occlusion balloon  20 . However, by using thicker and/or stronger material, stop balloon  50  is relatively more resistant to damage from abutting treatment instruments  60 . Stop balloon  50  may be formed from the same group of materials described above with respect to making occlusion balloon  20 ; Namely, thermoplastic elastomers, including styrenic TPEs such as styrene-ethylene-butylene-styrene (C-FLEX), natural rubbers (latex), synthetic rubbers (silicone), polyesters, polyolefins, polyamides, polyvinyl chloride, and combinations of the above, such as block copolymers.  
      During treatment of a patient, catheter  15  may be advanced through the patient&#39;s vasculature, such as vessel  30 , until occlusion balloon  20  and stop balloon  50  are positioned distal to stenosis  100 . As illustrated in  FIG. 5  and comparable to system  10  above, catheter  15  can also perform the function of a guidewire to direct treatment instrument  60  into and across stenosis  100 . Before advancing treatment catheter  60  into and through stenosis  100 , occlusion balloon  20  and balloon stop  50  are inflated by the delivery of a fluid through one or more inflation lumens in catheter  15  and inflation ports  18  and  19 , respectively. The inflation fluid may be a dilute radiopaque contrast solution or CO 2  gas. As discussed above, the annular space between catheter  15  and treatment instrument  60  may provide an intermediate pathway for irrigation, infusion of drugs or aspiration of the treatment area.  
      Balloon stop  50  has an inflated diameter large enough to prevent treatment instrument  60  from sliding forward into contact with occlusion balloon  20 . To perform its stop function, inflated balloon stop  50  does not need to contact the inner wall of vessel  30 , although such contact may occur, especially in tortuous vessels. Thus, the inflated diameter of balloon stop  50  is typically smaller than the inflated diameter of occlusion balloon  20 . The inflated shape of stop balloon  50  may be spherical or elongate. In one embodiment, stop balloon  50  may have an inflated diameter of about 0.020 inches (0.51 mm) and a length of about 2 mm with proximal and distal ends of stop balloon  50  each being affixed to the shaft of catheter  15  along a length of approximately 1 mm. Stop balloon  50  can be mounted to catheter  15  with adhesive, and with or without clamp rings, as will be understood to those of skill in the field of balloon catheters. Comparable to the embodiments described above, balloon stop  50  may be spaced a relatively short distance from balloon proximal end  23 , as shown in  FIGS. 4 and 5 , or balloon stop member  55  may be contiguous with proximal end  23  of occlusion balloon  20 , as will be described below.  
       FIGS. 6 and 7  are perspective illustrations of system  13  for treating a vascular condition, in accordance with a fourth embodiment of the current invention. In system  13 , the stop member is stop balloon  55  mounted around catheter  15  proximal to occlusion balloon  20 . Proximal end  23  of occlusion balloon  20  and distal end  55  of stop balloon  50  may overlap each other. Alternatively, stop balloon  55  and occlusion balloon  20  may be formed integrally, wherein stop balloon  55  has a relatively greater wall thickness of the same material. When inflated, such an integral balloon arrangement may optionally have a narrowed waist region between stop balloon  55  and occlusion balloon  20 . The inflation lumen (not shown) of catheter  15  communicates with both stop balloon  50  and occlusion balloon  20  through spiral cut openings  17 . Thus, both stop balloon  50  and occlusion balloon  20  are inflated simultaneously upon delivery of a fluid through the inflation lumen of catheter  15 . The fluid may be a dilute radiopaque contrast solution or CO 2  gas. In an alternative embodiment (not shown), second port  18  under occlusion balloon  20  and first port  19  under stop balloon  55  may be used instead of spiral cut openings  17 . As in previously described embodiments of the invention, stop balloon  55  prevents treatment instrument  60  from sliding forward into contact with occlusion balloon  20 .  
       FIGS. 8 and 9  are perspective illustrations of system  14  for treating a vascular condition, in accordance with a fifth embodiment of the current invention. In system  14 , the stop member is mesh stop  70  positioned on catheter  15  proximal to occlusion balloon  20 . Distal end  75  of mesh stop  70  is coupled to distal region  16  of catheter  15 . Proximal end  73  of mesh stop  70  is coupled to distal end  85  of actuator sheath  80 , which is sized and shaped to be slidingly disposed about the shaft of catheter  15  to operate mesh stop  70 , as described below. Actuator sheath  80  may be formed from suitable biocompatible tubing such as thermoset polyimide, or metal hypotubing.  
      Mesh stop  70  may be formed from braided metal wires such as TiNi (nitinol) or stainless steel, or from braided polymeric filaments. Ends  73 ,  75  of mesh stop  70  may be attached to catheter  15  and to actuator sheath  80 , respectively, by solder, adhesive or by mechanical attachments such as crimp bands. In response to relative sliding movement between actuator sheath  80  and the shaft of catheter  15 , mesh stop  70  is transformable between the collapsed configuration shown in  FIG. 8  and the expanded configuration shown in  FIG. 9 . Moving of the ends of mesh stop  70  apart or towards each other causes the tubular braid to collapse or expand, respectively, as will be understood by one of skill in the art. Preferably, the collapsed diameter of mesh stop  70  is no larger than the deflated profile of occlusion balloon  20 .  
      During treatment of a patient, catheter  15  and actuator sheath  80  may be advanced through the patient&#39;s vasculature, such as vessel  30 , until occlusion balloon  20  and mesh stop  70  are positioned distal to stenosis  100 . As illustrated in  FIG. 9  and as described above, catheter  15  and surrounding actuator sheath  80  can perform the function of a guidewire to direct treatment instrument  60  into and across stenosis  100 . Before advancing treatment catheter  60  into and through stenosis  100 , occlusion balloon  20  is inflated by the delivery of a fluid through an inflation lumen in catheter  15  and second inflation port  18 .  
      Additionally, prior to advancing treatment catheter  60  into and through stenosis  100 , mesh stop  70  is expanded by pushing actuator sheath  80  distally while pulling catheter  15  proximally, causing the diameter of mesh stop  70  to increase as the length of mesh stop  70  decreases. To protect occlusion balloon  20 , the expanded diameter of mesh stop  70  needs to be only large enough to block advancement of treatment instrument  60 . Thus, the expanded diameter of mesh stop  70  does not need to contact the inner wall of vessel  30 , although such contact may occur, especially in tortuous vessels. Once mesh stop  70  is expanded, sheath  80  may be temporarily held in position with respect to catheter  15  by a friction mechanism (not shown). The friction mechanism may include slight distortions or wave-like bends along a section of catheter  15 . Sheath  80  fits closely around catheter  15  so the slight bends can provide sufficient normal force to hold the two parts in a fixed relative position until the clinician collapses mesh stop  70  by pulling actuator sheath  80  proximally while pushing catheter  15  distally. Actuator sheath  80  may also be held in place by an external mechanical locking mechanism (not shown) provided at the proximal end of catheter  15 . Both mesh stop  70  and occluder balloon  20  are collapsed to remove system  14  from the patient.  
      As in the other embodiments of the current invention described above, mesh stop  70  prevents treatment instrument  60  from sliding distally over catheter  15  and actuator sheath  80  into contact with occlusion balloon  20 . Thus, the fragile occlusion balloon  20  is not damaged. Mesh stop  70  may be spaced a relatively short distance from balloon proximal end  23 , as shown in  FIGS. 9 and 10 , or mesh stop  70  may be contiguous with proximal end  23  of occlusion balloon  20 .  
      Although the embodiments of the invention disclosed herein are presently considered to be preferred, various changes and modifications can be made without departing from the spirit and scope of the invention. The scope of the invention is indicated in the appended claims, and all changes that come within the meaning and range of equivalents are intended to be embraced therein.