Patent Publication Number: US-2004049225-A1

Title: Aspiration catheter

Description:
BACKGROUND OF THE INVENTION  
       [0001] This invention generally relates to catheters, and particularly intravascular aspiration catheters.  
       [0002] Release of embolic debris during treatment of diseased blood vessels is a significant and potentially deadly problem. For example, pieces of a lesion in an occluded blood vessel may become dislodged during treatment of the occlusion during a balloon angioplasty procedure. In balloon angioplasty, a dilatation catheter having an inflatable balloon on a distal shaft section is advanced into the patient&#39;s vessel until the balloon is properly positioned across the lesion, and the dilatation balloon is inflated one or more times to a predetermined size so that the lesion is compressed against the arterial wall and the wall expanded to open up the vascular passageway. Dislodged pieces of the lesion can move downstream and completely block another portion of the blood vessel, thus causing myocardial infarction when used in the coronary anatomy or a stroke when used in the neural or carotid anatomy. Similarly, during delivery and deployment of an intravascular prosthesis such as a stent used to strengthen the dilated vessel, the stent struts may sheer off pieces of the lesion. In an atherectomy procedure in which the lesion is cut away from the blood vessel wall by the mechanical cutting apparatus of the atherectomy catheter, failure to capture and remove all the biological debris from the blood vessel can similarly result in an embolic event. Additionally, during treatment of diseased vessels by laser ablation in which the lesion is vaporized, one difficulty has been ensuring complete vaporization of all the biological material dislodged during the process.  
       [0003] Embolic protection devices, which have been developed to address the problem of capturing and removing embolic debris, include a filter or occlusion balloon placed downstream from the treatment site to trap embolic debris before it reaches the smaller blood vessels downstream. However, there have been problems associated with filtering systems. For example, the filter can become clogged with debris, so that blood circulation past the clogged filter will be insufficient for the downstream vessels and organs. If a filter should become clogged when in use in the carotid arteries, blood flow could be diminished to the vessels leading to the brain, and the physician administering the procedure may be unaware that the filtering device is clogged and that there is little or no blood flowing to the brain. Similarly, the debris trapped by the occlusion balloon must be completely removed from the blood stream to avoid the potential for injury to the patient. Aspiration or vacuum catheters have been suggested for removing embolic debris by suction of the debris from the bloodstream. However, there have been complications with such systems. The aspiration catheter may not always remove all of the embolic material from the bloodstream, and overly powerful suction could cause problems to the patient&#39;s vasculature.  
       [0004] Accordingly, it would be a significant advance to provide a catheter providing improved embolic protection during treatment of a stenosed blood vessel. This invention satisfies these and other needs.  
       SUMMARY OF THE INVENTION  
       [0005] The invention is directed to a catheter which has an elongated shaft having a first lumen extending from a proximal shaft section to the distal end of the shaft with a distal port at the shaft distal end, and having a second lumen extending in at least a distal shaft section to a distal port located proximal to the distal port of the first lumen.  
       [0006] In a presently preferred embodiment, the catheter is an aspiration catheter with a vacuum source in fluid communication with the first lumen, providing improved removal of embolic debris from within a patient&#39;s body lumen. In accordance with the invention, the distal most end of the catheter defines the distal port of the aspiration lumen (i.e., first lumen), and facilitates positioning the aspiration port as close as possible to the embolic debris to be removed. Although discussed primarily in terms of an aspiration catheter, it should be understood that the first lumen can alternatively be connected to a source of fluid, so that the catheter is configured for fluid delivery, as for example as a perfusion or drug delivery catheter, or the delivery of contrast media used to visualize the anatomy under x-ray.  
       [0007] The second lumen is configured to slidably receive a device such as a guidewire or an embolic protection device. In use, the catheter is typically advanced over the previously introduced device within a patient&#39;s body lumen until the distal end of the catheter is positioned at the desired location within the body lumen. In a presently preferred embodiment, the device over which the catheter is advanced is an embolic protection device such as an occlusion balloon catheter or a filter catheter having a trap or filter on a distal section thereof. However, the catheter of the invention may be used with a variety of conventional embolic protection devices, see for example U.S. Pat. Nos. 6,398,756 and 6,383,206, incorporated by reference herein, for details regarding balloon occlusion and filter type embolic protection devices.  
       [0008] The distal end of the catheter of the invention, which defines the distal port of the first lumen, is configured to facilitate aspiration of embolic debris from around and within the embolic protection device. Thus, embolic debris which is otherwise difficult to access can be removed from within the body lumen by positioning the catheter distal end, which has a specially configured shape and which defines the distal port of the aspiration lumen, directly at the location of the debris. For example, in one embodiment, the distal end of the catheter has a wedge or truncated shape configured to fit in the space between the edge of an expanded occlusion balloon and the blood vessel wall. The distal end of the catheter can have a variety of suitable shapes, and in one embodiment the shape of the distal end of the catheter is selected from the group consisting of truncated, tapered, and squared, depending on the embolic protection device used with the catheter of the invention.  
       [0009] In a presently preferred embodiment, the catheter of the invention is a rapid exchange type catheter, so that the second lumen is a relatively short lumen extending in the distal shaft section from a proximal port located distal to the proximal end of the shaft to the distal port located proximal to the distal port of the first lumen. However, in an alternative embodiment, the catheter is an over-the-wire type catheter in which the second lumen proximal port is located at the shaft proximal end. In one embodiment, a support mandrel extends along at least the proximal shaft section, for improving the pushability of the catheter.  
       [0010] The catheter of the invention provides for improved removal of embolic debris trapped by an embolic protection device. Due to the configuration of the ports of the first and second lumens, the distal aspiration port can be positioned in a desired location in a patient&#39;s body lumen for removal of embolic debris from around or within an embolic protection device, to thereby prevent or inhibit debris in the bloodstream from causing a blockage in vessels at downstream locations or a blockage of blood flow through filtering devices. Moreover, the catheter of the invention provides a system and method which is easy for a physician to use. These and other advantages of the invention will become more apparent from the following detailed description of the invention and accompanying exemplary drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0011]FIG. 1 is an elevational view, partially in section, of a catheter which embodies features of the invention, with the catheter over a balloon occlusion catheter in a patient&#39;s body lumen.  
     [0012]FIG. 2 is a transverse cross sectional view of the catheter shown in FIG. 1, taken along line  2 - 2 .  
     [0013]FIG. 3 is a transverse cross sectional view of the catheter shown in FIG. 1, taken along line  3 - 3 .  
     [0014]FIG. 4 is a transverse cross sectional view of the catheter shown in FIG. 1, taken along line  4 - 4 .  
     [0015]FIG. 5 illustrates the distal section of an alternative embodiment of the catheter of FIG. 1, with a tapered distal end, and with the catheter over a filter embolic protection device.  
     [0016]FIG. 6 illustrates the distal section of an alternative embodiment of the catheter of FIG. 1, with a squared distal end. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0017]FIG. 1 illustrates a rapid exchange type catheter  10  embodying features of the invention. Catheter  10  generally comprises an elongated catheter shaft  11  having a proximal end, a distal end, a first lumen  12  extending from the proximal to the distal end of the shaft with a distal port  13  at the shaft distal end. A second lumen  14  extends in a distal shaft section from a proximal port  15  located distal to the proximal end of the shaft to a distal port  16  located proximal to the distal port  13  of the first lumen  12 . In one embodiment, the distal port  16  of the second lumen  14  is spaced about 1 to about 30 mm, preferably about 10 to about 20 mm proximally from the distal port  13  of the first lumen  12 . An adapter  17  on the shaft proximal end is configured to provide access to the first lumen  12 . In the embodiment of FIG. 1, the catheter  10  is an aspiration catheter, and is positioned in a patient&#39;s body lumen  29  for aspiration of material from within the body lumen. The adapter  17  is configured for connecting a vacuum source (not shown) to the aspiration catheter  10 , in fluid communication with the first lumen  12 , for aspiration through the first lumen  12 . The catheter  10  may alternatively be used as a fluid delivery catheter, so that the adapter  17  may be configured for connecting a fluid source (not shown) to the first lumen for delivery of fluid through the first lumen to the body lumen  29 . Although not illustrated, the adapter  17  may have multiple arms for connecting to vacuum and fluid sources. FIGS.  2 - 4  illustrate transverse cross sectional views of the catheter  10 , taken along lines  2 - 2 ,  3 - 3 , and  4 - 4 , respectively. In the embodiment of FIG. 1, the first lumen  12  has an inner diameter larger than the inner diameter of the second lumen  14 . The inner diameter of the first lumen  12  is typically about 0.25 to about 2 mm, preferably about 0.76 to about 1.14 mm, and the inner diameter of the second lumen  14  is typically about 0.25 to about 1.4 mm, preferably about 0.44 to about 1.1 mm. In an alternative embodiment (not shown), the second lumen  14  is larger than the first lumen  12 .  
     [0018] In the embodiment of FIG. 1, a support mandrel  20  extends in a proximal shaft section from the proximal end of the shaft to a location spaced proximal to the proximal port  15  of the second lumen  14 . In alternative embodiment, the support mandrel distal end may be located distal to the proximal port  15  of the second lumen  14 , including for example being located between the proximal port  15  and the distal port  16  of the second lumen  14 . The support mandrel is preferably a solid rod or wire, and is preferably formed of a high strength, flexible material, including metallic materials such as stainless steel, NiTi alloy, MP35N, and cobalt chrome (L605). The support mandrel  20  is in a wall of the shaft  11 , and preferably in a mandrel lumen in the wall, radially adjacent (i.e., alongside) the first lumen  12  in the proximal shaft section. The support mandrel  20  is configured to increase the pushability of the catheter shaft  11 , and typically has a length which is about 40 to about 100% of the length of the catheter shaft  11 .  
     [0019] In the embodiment of FIG. 1, the catheter  10  comprises a first polymeric tubular member  22  defining the first lumen  12 , and a second polymeric tubular member  24  defining the second lumen  14  and secured to the distal section of the first polymeric tubular member  22 , as for example by heat shrink tubing  25  therearound as best illustrated in FIG. 2. The first polymeric tubular member  22  is formed by extruding the tube with the first lumen  12  extending from the proximal to the distal end thereof, and with a blind lumen in a proximal section thereof configured to receive the mandrel  20 . Although illustrated in FIG. 2 as tightly fitting within the mandrel lumen, the mandrel lumen is typically sufficiently large to facilitate sliding the mandrel into the lumen. The mandrel  20  may be secured in place in the mandrel lumen as for example by adhesive or heating the polymeric tubular member  22  therearound, or attached at the mandrel proximal end only, or merely contained in the mandrel lumen and not fixed to the shaft. However, a variety of suitable methods can be used to form the catheter  10 , as are conventionally known, including for example by extruding a tubular member with the lumens  12 ,  14  therein. The first and second polymeric tubular members  22 ,  24  may be formed of the same or different polymeric materials. Although the first polymeric tubular member  22  defining the first lumen  12  is illustrated as a single length of tubing, it should be understood that multiple longitudinal sections of tubing joined together along the length of the catheter  10  can be used, as for example to provide variable or increasing flexibility along the length of the catheter. Additionally, although illustrated in FIG. 3 with a space between the outer tubular member  25  and the tubular members  22 ,  24 , the space may be filled in with polymeric material as for example by polymeric material from the tubular members  22 ,  24 ,  25  flowing into the space during heat bonding thereof. Similarly, although illustrated with circular transverse cross sections a variety of shaft configurations may be used as are conventionally known including semi-circular, oblong, crescent shaped and the like.  
     [0020] The second lumen  14  of catheter  10  is configured to slidably receive a device therein, over which the catheter is advanced within the body lumen  2 , so that the second lumen  14  is open to outside the catheter  10  (i.e., the second lumen distal port  16  is open to allow the catheter  10  to be advanced over a device). The catheter  10  is illustrated in FIG. 1 with an embolic protection device  30  slidably disposed in the second lumen  14 . A variety of suitable conventional devices  30  may be used with the catheter  10  of the invention. In the embodiment of FIG. 1, the embolic protection device  30  is a balloon occlusion catheter comprising an elongated shaft  31  defining an inflation lumen  32  in fluid communication with a balloon  33  on a distal end of the shaft  31 . The balloon occlusion catheter  30  has a guide member  34  comprising a guidewire within lumen  32  and sealingly secured to the distal end of the catheter. In an alternative embodiment (not shown), the guide member  34  is a flexible tip member such as a coil (not shown) secured to the distal end of the shaft  31 , as is conventionally known. FIG. 5 illustrates an alternative embodiment in which the embolic protection device  30  in the catheter second lumen  14  is a filter device comprising a guidewire  41  having a trap  42  on a distal end thereof. In the embodiment of FIG. 5, the trap  42  is a collapsible mesh basket, although a variety of suitable filter type embolic protection devices can be used as are conventionally known. In the embodiment of FIG. 5, the device  30  further comprises an elongated shaft  31  with the guidewire  41  disposed in the shaft lumen, and the guidewire  41  can be moved relative to the shaft  31  to reversibly open or collapse the mesh basket.  
     [0021] In the embodiment of FIG. 1, a distal tip member  26  is secured to the distal end of the first polymeric tubular member  22 , and is formed of a soft polymeric material to provide an atraumatic distal leading end of the catheter  10 . Radiopaque material may be included in or on the distal tip member, or a radiopaque marker band (not shown) provided on the distal tip member, for visualization under x-ray during the medical procedure. The distal tip member  26  defines the distal end of the shaft  11  and the distal port  13  of the first lumen  12 . The distal tip member  26  is fusion or adhesively bonded to the distal end of the tubular member  22 , and a variety of suitable junctions may be used including a butt joint as shown, or a lap joint.  
     [0022] The distal end of the catheter shaft  11  has a shape configured to facilitate positioning the distal end adjacent to embolic debris trapped by the embolic protection device  30  for removing the debris by suctioning the debris through the first lumen  12 . In the embodiment of FIG. 1, the distal end has a truncated shape configured to fit in the space around the sides of the inflated balloon  33  of device  30  between the balloon  33  and the wall of the body lumen  29  to remove embolic debris  50  therefrom. However, the shaft distal end defining the distal port  13  of the first lumen  12  can have a variety of suitable shapes depending on the location of the debris to be removed. For example, FIG. 5 illustrates an alternative embodiment of catheter  10  having a distal end with a tapered shape configured for removing the debris from within the trap  42  of device  30 , and FIG. 6 illustrates a distal end with a squared shape. Although not illustrated, the distal end of the shaft  11  can be advanced into the trap  42 , with the tapered distal end defining the distal port  13  adjacent to embolic debris in the trap  42  for removal of the debris from the trap  42 . The tapered shape facilitates positioning the port  13  at the back (i.e., downstream end) of the trap  42 .  
     [0023] When the catheter  10  of the invention is used in an aspiration procedure, the embolic protection device  30  is in place in the body lumen  29 , adjacent to an intravascular catheter such as an angioplasty or atherectomy catheter (not shown) during treatment of a stenosed region of the body lumen  29 . Dislodged pieces of biological debris which are trapped by the embolic protection device are removed from the body lumen by the catheter  10  of the invention. Specifically, the catheter  10  of the invention is advanced over previously introduced embolic protection device  30  by placing the proximal end of the device  30 , extending outside the patient, in the distal port  16  of the second lumen  14  of the catheter  10 , and slidably advancing the catheter  10  over the device  30  to position the distal port  13  of the aspiration lumen  12  adjacent to the embolic debris trapped by the device  30 .  
     [0024] To the extent not previously discussed herein, the various catheter components may be formed and joined by conventional materials and methods. The shaft can be formed by conventional techniques, such as by extruding and necking materials found useful in intravascular catheters such a polyethylenes, polyvinyl chloride, polyesters, polyamides, polyimides, polyurethanes, and composite materials. Distal tip member  26  is preferably formed of a polymeric material having a lower Shore durometer hardness than the polymeric material forming the first tubular member  22 .  
     [0025] The length of the catheter  10  is generally about 30 to about 160 centimeters (cm), and typically about 90 cm for use in the coronary anatomy. The shaft proximal section has an outer diameter (OD) of about 0.030 to about 0.120 inch (0.76 to 3.05 mm), and the shaft distal section has an OD of about 0.015 to about 0.11 inch (0.38 to 2.8 mm). The mandrel typically has a length of about 20 to about 160 cm, and an OD of about 0.2 to about 1.14 mm.  
     [0026] While the present invention has been described herein in terms of certain preferred embodiments, those skilled in the art will recognize that modifications and improvements may be made without departing from the scope of the invention. Moreover, while individual features of one embodiment of the invention may be discussed or shown in the drawings of the one embodiment and not in other embodiments, it should be apparent that individual features of one embodiment may be combined with one or more features of another embodiment or features from a plurality of embodiments. For example, while the catheter distal end having a truncated shape is illustrated with the occlusion balloon embolic protection device, it should be understood that any of the distal end shapes may be used with a variety of embolic protection devices including the embolic protection devices described herein.