Abstract:
A method and apparatus for introducing a stent into a region of a major blood vessel within the human body in a manner which substantially reduces the risk of embolic material escaping to the vessel and causing a blockage at a downstream location. Additionally, the apparatus of the invention includes a uniquely designed stent delivery catheter having a central lumen through which a guide wire travels, the central lumen being provided with a valve means that is operable by the guide wire and when moved into a closed position by withdrawal of the guide wire, functions to prevent the flow of loose debris toward the proximal end of the catheter.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to methods and apparatus for introducing a stent to into a region of a major blood vessel within the patient, such as the carotid artery, the renal artery and the coronary artery.  
           [0003]    2. Discussion of the Prior Art  
           [0004]    A number of procedures have been suggested in the past for opening stenosed or occluded blood vessels in a patient caused by the deposit of plaque or other material on the walls of the blood vessels. For example, angioplasty, is a well known procedure wherein an inflatable balloon is first introduced into the occluded region and then inflated, dilating the stenosed blood vessel in the manner to increase the intraluminal diameter.  
           [0005]    Another well-known prior art procedure involves permanently or temporarily introducing a stent into the stenosed region to open the lumen of the vessel. The stent, which is readily commercially available from various sources, typically comprises a generally cylindrically shaped mesh sleeve made from such materials as stainless steel or nitinol. The unique design of the stent permits it to be radially expanded, while still providing sufficient rigidity to maintain its shape once it has been expanded to a desired size.  
           [0006]    In the practice of the prior art stent emplacement procedures, the stent is introduced into the desired blood vessel using known percutaneous methods. More particularly, a catheter, having the stent affixed thereto, is directed to the region of the blood vessel being treated and is strategically positioned so that the stent is centered across the stenosed region. This done, the balloon is inflated, by introducing gas or fluid, through a lumen in the catheter communicating with the balloon. The controlled inflation of the balloon causes the stent to expand radially outward into engagement with the stenosed material. As the stent expands, the material is forced outward, dilating the lumen of the blood vessel. Once in position, the stent retains its expanded shape, providing an open passage for blood flow. The balloon is then deflated and the catheter withdrawn from the vessel.  
           [0007]    During the stent emplacement procedure, plaque that has been deposited on the walls of the vessel may be set free and when this material travels downstream, it can cause serious complications. By way of example, loose embolic material released within the carotid arteries may travel downstream to the brain, possibly causing stroke, which can lead to permanent injuries and sometimes the death of the patient.  
           [0008]    Thus, there is a need for an apparatus and method for delivering a stent into an arterial occlusion, which effectively prevents loose embolic material from traveling downstream and also prevents blood and embolic material from flowing through the guide wire lumen of the stent delivery catheter a direction toward the proximal end of the catheter.  
           [0009]    In typical prior art balloon angioplasty procedures, a guiding catheter having a preformed distal tip is percutaneously introduced through the femoral artery into the cardiovascular system of a patient in accordance with conventional techniques. The guiding catheter is then advanced within the cardiovascular system until the distal tip is seated in the ostium of a desired coronary artery. A guidewire is positioned within an inner lumen of a dilatation catheter and then both are advanced through the guiding catheter to the distal end thereof. The guidewire is first advanced out of the distal end of the guiding catheter into the patient&#39;s coronary vasculature until the distal end of the guidewire crosses a lesion to be dilated, then the dilatation catheter having an inflatable balloon proximate the distal end thereof is advanced into the patient&#39;s coronary anatomy over the previously introduced guidewire until the balloon of the dilatation catheter is properly positioned across the lesion. Once in position across the lesion, the balloon is inflated to a predetermined pressure to compress the arteriosclerotic plaque of the lesion against the inside of the artery wall and to otherwise expand the inner lumen of the artery. The balloon is then deflated so that blood flow can be resumed through the dilated artery and the dilatation catheter can be removed.  
           [0010]    Applicant is familiar with a prior art distal protection system that is available from Medtronic, Inc of Minneapolis, Minn. that is sold under the name and style “GUARDWIRE PLUS”. This system, which contains the balloon at its the distal tip, is deployed across the lesion and is then inflated to occlude the vessel and prevent migration of embolic particles that may become dislodged during an intervention. The angioplasty balloon and stent systems are then advanced to the treatment side, where the dislodged large particles remain suspended in the occluded vessel. Upon completion of the interventional procedure, another catheter is introduced and the particles are aspirated. This done, the balloon is deflated and removed.  
           [0011]    Applicant is also familiar with a prior art, balloon protected flush extraction system offered by the Kensey Nash Corp. of Exton, Pa. under the name and style “TRIACTIV”. This system uses three distinct components, namely a guide wire with the distal protection balloon, a flexible 3 French flush catheter and active peristaltic pump flush and extraction systems. These three features work in concert to provide distal protection with debris extraction. Following stenting the protected space is flushed and any remaining loose debris is extracted.  
           [0012]    Another prior art distal protection device is offered for sale by the Traatek Company of Miami, Fla. under the name and style “PERCUSURGE”. This device is a balloon the occlusion tlrombectomy device approved by the United States Food and Drug Administration for vein graft intervention.  
         SUMMARY OF THE INVENTION  
         [0013]    It is an object of the present invention to provide a novel method and apparatus for introducing a stent into a region of a major blood vessel within the human body in a manner which substantially reduces the risk of embolic material escaping to the vessel and causing a blockage at a downstream location. More particularly it is an object of the invention to provide an apparatus and method to substantially contain loose embolic material within the aorta and the carotid arteries during an interventional procedure and thereby prevent it from reaching the brain.  
           [0014]    Another object of the invention is to provide an apparatus of the aforementioned character which includes a uniquely designed stent delivery catheter having a central lumen through which a guide wire travels, the central lumen being provided with a valve means that is operable by the guide wire and when moved into a closed position by withdrawal of the guide wire functions to prevent bloodflow toward the proximal end of the catheter.  
           [0015]    Another object of the invention is to provide a stent delivery system which includes a stent delivery catheter of a simple construction having mounted proximate the distal end thereof an angioplasty balloon of conventional design. A stent expanding balloon, which carries a readily commercially available type of expandable stent is mounted intermediate of the distal and proximal ends of the catheter.  
           [0016]    Another object of the invention is to provide an apparatus of the character described in the preceding paragraph, which includes a first side lumen for use in inflating the angioplasty balloon and a spaced apart second side lumen for use in inflating the stent expanding balloon.  
           [0017]    Another object of the invention is to provide an apparatus as described in the preceding paragraph in which the cannula is provided with a third lumen that is in communication with the blood vessel via an opening in the cannula wall to permit the aspiration of embolic material residing within the blood vessel.  
           [0018]    By way of summary, the present invention provides a method and apparatus for preventing embolic material from escaping a site of intervention within the carotid artery, the renal artery and like arteries. More specifically, the present invention provides an apparatus and method for introducing a stent into a region of a major blood vessel within the human body exhibiting plaque deposits, thereby opening the occlusion. The method and apparatus of the invention also prevents embolic material from traveling downstream within the blood vessel. Additionally, the apparatus of the invention includes a catheter of novel design that includes a central lumen provided with a uniquely designed check valve that, when moved into a closed position by withdrawal of the guide wire from the catheter lumen, substantially blocks the flow of blood and loose debris through the central lumen of the catheter in a direction toward the proximal end of the catheter. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a generally perspective view of one form of the stent delivery system of the present invention.  
         [0020]    [0020]FIG. 2 is a foreshortened, top view of the stent delivery system shown in FIG. 1.  
         [0021]    [0021]FIG. 3 is a greatly enlarged, cross-sectional view taken along lines  3 - 3  of FIG. 2.  
         [0022]    [0022]FIG. 4 is an enlarged cross sectional view taken along lines  4 - 4  of FIG. 3.  
         [0023]    [0023]FIG. 5 is an enlarged cross sectional view taken along lines  5 - 5  of FIG. 3.  
         [0024]    [0024]FIG. 6 is an enlarged cross sectional view taken along lines  6 - 6  of FIG. 3.  
         [0025]    [0025]FIG. 7 is an enlarged cross sectional view taken along lines  7 - 7  of FIG. 3.  
         [0026]    [0026]FIG. 8 is a greatly enlarged cross sectional view of the area designated in FIG. 3 by the numeral  8 .  
         [0027]    [0027]FIG. 9 is a cross-sectional view taken along lines  9 - 9  of FIG. 8.  
         [0028]    [0028]FIG. 10 is a cross-sectional view similar to FIG. 8, but showing the guide wire withdrawn and the check valve moved into a closed configuration.  
         [0029]    [0029]FIG. 11 is a cross-sectional view taken along lines  11 - 11  of FIG. 10.  
         [0030]    [0030]FIG. 12 is a fragmentary, generally perspective view of the valve means of the form of the invention shown in FIG. 1.  
         [0031]    [0031]FIG. 13 is a fragmentary, generally diagrammatic, perspective view illustrating the placement of the catheter of the system over the guide wire.  
         [0032]    [0032]FIG. 14 is a generally perspective view of an alternate form of the stent delivery system of the present invention.  
         [0033]    [0033]FIG. 15 is a foreshortened, top view of the stent delivery system shown in FIG. 14.  
         [0034]    [0034]FIG. 16 is a greatly enlarged cross- sectional view taken along lines  16 - 16  of FIG. 15.  
         [0035]    [0035]FIG. 17 is an enlarged cross sectional view taken along lines  17 - 17  of FIG. 16.  
         [0036]    [0036]FIG. 18 is an enlarged cross sectional view taken along lines  18 - 18  of FIG. 16.  
         [0037]    [0037]FIG. 19 is an enlarged cross sectional view taken along lines  19 - 19  of FIG. 16.  
         [0038]    [0038]FIG. 20 is an enlarged cross sectional view taken along lines  20 - 20  of FIG. 16.  
         [0039]    [0039]FIG. 21 is an enlarged cross sectional view taken along lines  21 - 21  of FIG. 16.  
         [0040]    [0040]FIG. 22 is a greatly enlarged cross sectional view of the area designated in FIG. 16 by the numeral  22 . 
     
    
     DESCRIPTION OF THE INVENTION  
       [0041]    Referring to the drawings and particularly to FIGS. 1, 2 and  3 , one form of the catheter system of the invention for balloon angioplasty and stent delivery is there illustrated and generally designated by the numeral  30 . This system here comprises a guide wire  32  and an elongated catheter  34  having a proximal end  34   a , a distal end  34   b  and an axial center line  34   c . Catheter  34  is preferably formed of a biocompatible and hydrophilic compatible material, such as a lubricous polyimide or polyethylene. Other suitable materials for the catheter include nylons, urethanes, and polypropylene that are preferably compatible with coatings such as silicone and various hydrophilic coatings.  
         [0042]    As is best seen by also referring to FIGS. 4, 5 and  6 , in the present form of the invention, catheter  34  is provided with a first passageway  36  through which the guidewire  32  can be slideably moved. As illustrated in FIG. 3, first passageway  36  is coaxially aligned with axial center line  34   c . By way of example, first passageway  36  may have a diameter of about 00.035 inches, has a proximal end  36   a  and a distal end  36   b . As will presently be discussed in greater detail, an important feature of the apparatus of the present invention is a novel valve means that is disposed proximate distal end  36   b  of first passageway  36  for opening and closing the first passageway. Uniquely, this important valve means is movable by the guide wire  32  from a closed position shown in FIGS. 10, 11 and  13  to an open position shown in FIG. 12. When the valve means is in the closed position illustrated in FIGS. 10 and 13, the flow of loose debris such as embolic material through the first passageway  36  toward the proximal end of the catheter is substantially blocked. In the present form of the invention, this important valve means comprises a check valve  37  that is here provided as a partition  37   a  that spans the central passageway in the manner shown in FIG. 10. Uniquely partition  37   a  has a yieldably deformable central portion that is provided with a pair of crossing, perpendicularly extending slits  37   b  (FIG. 11). With this construction, when the guide wire impinges upon the check valve, it will force the slits  37   b  into the open configuration shown in FIG. 12 permitting free passage of the guide wire past the valve means. When the guide wire is retracted, in the manner shown in FIG. 13, the slitted portion of the valve will return to the starting, closed configuration shown in FIGS. 10 and 11. Partition  37   a  can be constructed of any suitable, semi-rigid plastic material.  
         [0043]    Catheter  34  is also provided with a second side passageway or lumen  38  that is spaced apart from first passageway  36 . As best seen in FIG. 3, second passageway  38  has an inlet  38   a  and an outlet  38   b . Additionally, catheter  34  is provided with a third passageway or lumen  40  that is also spaced apart from first passageway  36 . As indicated in FIG. 3, third passageway  40  has an inlet  40   a  and an outlet  40   b.    
         [0044]    Mounted on cannula  34  proximate the distal end thereof is an angioplasty balloon  42 . Balloon  42 , which is of conventional construction, is inflatable through the second passageway  38  with which it is in communication. In a conventional manner, balloon  42  is inflatable at deployment to about the diameter of the body vessel within which the catheter is inserted.  
         [0045]    Balloon  42  may be formed of a compliant or non-compliant material, such as polyethylene or other standard balloon materials. Suitable materials for the construction of balloon  42  include a copolymer polyolefin material available from E.I. DuPont de Nemours and Co. of Wilmington, Del. By way of example, balloon  42  may have a length of about 1 cm and a wall thickness of between about 0.0007 and about 0.004″.  
         [0046]    Mounted on cannula  34  intermediate the proximal and distal ends thereof is an expandable means for expanding a stent. This expandable means is here provided as a stent balloon  44 . Stent balloon  44 , which is also of conventional construction, is inflatable through the third passageway  40  with which it is in communication. Stent balloon  44  may be manufactured from a substantially flexible and resilient material, such as polyethylene, polyester, latex, silicone, or more preferably polyethylene and polyester. A variety of balloons for stenting procedures are commercially available and have a wide range of known inflated lengths and diameters, allowing an appropriate balloon to be chosen specifically for the particular vessel being treated. By way of example, stent balloon  44  of the apparatus of the present invention may be of a length of between approximately 8 and 30 mm.  
         [0047]    As best seen in FIG. 3, a radially expandable stent  48  is mounted on and circumscribes stent balloon  44 . Stent  48 , which is of conventional construction and is readily commercially available from various sources, may comprise a tube, sheet, wire, mesh or spring. In the present form of the invention, stent  48  comprises a substantially cylindrical wire mesh sleeve that is substantially rigid, yet expandable when subjected to radial pressure. While various materials may be used in the construction of the stent, materials such as stainless steel or nitinol, are preferable with stainless steel being most preferred.  
         [0048]    As will be discussed in greater detail in the paragraphs which follow, in accordance with procedures well known to those skilled in the art, once the stent  48  is in the proper position, a fluid is introduced through the inflation lumen  40  to inflate the balloon  44 . As the balloon  44  expands, the fluid pressure exerted on the stent forces the stent radially outwardly to engage plaque formed on the vessel wall. The expanding stent functions to push the plaque away from the region and to open the vessel. The stent  48 , which generally covers a substantial portion of the plaque, traps it between the stent and the wall of the vessel. Once the stent is in place, balloon  44  is deflated by withdrawing the fluid out of the inflation lumen  40  and the catheter  34  is withdrawn from the patient using conventional methods. The stent  48  remains in place, substantially permanently covering the plaque in the treated region and forming part of the lumen of the vessel. For a purpose presently to be described, an aperture  49  is provided in the cannula wall at a location between the stent balloon  44  and the angioplasty balloon  42  (see FIG. 3).  
         [0049]    As the stenosed region is being opened, by the balloon stent and the stent  48 , plaque may break loose from the wall of the vessel. The various forms of the method of the present invention are specifically directed to taking steps to prevent this type of debris from traveling downstream of the vessel of the patient.  
         [0050]    One form of the method of the invention, which is carried out using the apparatus of the invention shown in FIGS. 1 through 13, comprises the steps of first advancing the guide wire and then the catheter through a vessel of the patient in a conventional manner until the radially expandable stent is disposed proximate the stenosis. This done, fluid is introduced into the inlet of the second passageway to inflate the angioplasty balloon to a position in engagement with the wall of the vessel of the patient to block the downstream passage of emboli past the inflated angioplasty balloon. With the angioplasty balloon in inflated condition, the guide wire is withdrawn from the first passageway of the catheter to move the valve means of the invention into a closed positioned to thereby substantially block blood and loose debris flow through the first passageway of the catheter in a direction toward the proximal end thereof. Next, a fluid is introduced into the inlet of the third passageway to inflate the stent balloon to a position wherein the stent is at least partially imbedded into the wall of the dilated stenosis. With the stent thus properly positioned, the stent balloon is deflated. Next, using the aspirating pump  51 , the fluid and embolic material that is within the artery of the patient is aspirated from the artery via aperture  49  (see FIG. 1). Following the aspirating step, the angioplasty balloon is deflated and the catheter, the stent balloon, the angioplasty balloon and the guide wire are removed from the vessel of the patient.  
         [0051]    Referring next to FIGS. 14 through 22, an alternate, form of the invention is there shown and generally designated by the numeral  50 . This alternate system is similar in many respects to that shown in FIGS. 1 through 13 and like numerals are used in FIGS. 14 through 22 to identify like components. Turning particularly to FIGS. 14, 15 and  16 , this alternate form of the invention can be seen to comprise comprises a guide wire  32  and an elongated catheter  54  having a proximal end  54   a , a distal end  54   b  and an axial center line  54   c . As before, catheter  54  is preferably formed of a biocompatible and hydrophilic compatible material, such as a lubricous polyimide or polyethylene.  
         [0052]    As best seen in FIG. 16, catheter  54  is provided with a first centrally disposed passageway  56  and a pair of side passageways  58  and  60 . Passageway  58  is provided with an inlet port  58   a  and an outlet port  58   b . Guide wire passageway  60 , which is also provided with an inlet port  60   a  and an outlet port  60   b , slidably receives the guide wire  32 . For a purpose presently to be described, passageway  56  is in communication with the vessel of the patient via an aperture  62  provided in a sidewall of the catheter.  
         [0053]    As in the early air described embodiment of the invention, novel valve means, which valve means are identical to that previously described herein, are disposed proximate the distal end  60   b  of passageway  60  for opening and closing the passageway. Like the earlier described valve means, this latter valve means is movable by guide wire  32  from a closed position to an open position shown in FIG. 22. When the valve means is in the closed position, the flow of blood and embolic material through passageway  60  toward the proximal end  60   a  thereof is substantially blocked.  
         [0054]    Mounted on cannula  54  proximate the distal end thereof is an angioplasty balloon  42 . Balloon  42 , which is of the conventional construction previously described, is inflatable through guide wire passageway  60  with which it is in communication (see FIG. 16). In a conventional manner, balloon  42  is inflatable at deployment to about the diameter of the body vessel in which the catheter is inserted.  
         [0055]    Mounted on cannula  54  intermediate the proximal and distal ends thereof is a stent balloon  44 . By way of example, stent balloon  44  is spaced from balloon  42  by a distance of approximately 10 cm. stent balloon  44 , which is of conventional construction previously described, is inflatable through side passageway  58  with which it is in communication. As before, stent balloon  44  may be manufactured from a substantially flexible and resilient material, such as polyethylene, polyester, latex, silicone, or more preferably polyethylene and polyester.  
         [0056]    As best seen in FIG. 16, a radially expandable stent  48  of the character previously described is mounted on and circumscribes stent balloon  44 . As in the earlier described embodiment, stent  44  is substantially rigid, yet expandable when subjected to radial pressure. Once the stent  48  is in the proper position, a fluid is introduced through the side inflation lumen  58  to inflate the balloon  44 . As the balloon  44  expands, the fluid pressure exerted on the stent forces the stent radially outwardly to engage plaque formed on the vessel wall. The expanding stent functions to push the plaque away from the region and to open the vessel. The stent  48 , which substantially covers the plaque, positions it between the stent and the wall of the vessel. Once the stent is in place, balloon  44  is deflated by withdrawing the fluid out of the inflation lumen  58  with the angioplasty balloon still inflated, blood and loose debris is aspirated from the vessel in a conventional manner via aperture  62 . Withdrawal of the guide wire causes the valve means or check valve  37  to close, thereby substantially blocking the flow of loose debris into passageway  60  of the catheter. Following the aspiration step, the catheter if removed from the patient using conventional methods. The stent  48 , of course, remains in place, substantially permanently covering the plaque in the treated region and forming part of the lumen of the vessel.  
         [0057]    An alternate form of the method of the invention is carried out using the apparatus shown in FIGS. 14 through 22. This alternate method of the invention comprises the steps of first advancing the guide wire and the catheter through a vessel of the patient until the radially expandable stent is disposed proximate the stenosis. This done, a fluid is introduced into the inlet of the guide wire passageway to inflate the angioplasty balloon to a position in engagement with the wall of the vessel. With the angioplasty balloon thus inflated, downstream passage of emboli is substantially blocked. Next, the guide wire is withdrawn from the guide wire passageway of the catheter to move the valve means into a closed positioned to substantially block the flow of loose debris through the guide wire passageway of the catheter in a direction toward the proximal end thereof. With the valve means closed, a fluid is next introduced into the inlet of the side passageway to inflate the stent balloon until the stent is properly imbedded into the wall of the dilated stenosis. Following the deflation of the stent balloon, the fluid and embolic material trapped within the artery of the patient is aspirated therefrom via the opening provided in the wall of the catheter. When the aspiration step is completed, the angioplasty balloon can be deflated and the catheter along with the stent balloon, the angioplasty balloon and guide wire can be removed from the vessel of the patient.  
         [0058]    Having now described the invention in detail in accordance with the requirements of the patent statutes, those skilled in this art will have no difficulty in making changes and modifications in the individual parts or their relative assembly in order to meet specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the invention, as set forth in the following claims.