Abstract:
A method is provided for preventing leakage of blood from a vessel. The method includes inserting a portion of an apparatus into a puncture tract extending through tissue to a puncture in the vessel; the apparatus including a thrombogenic matrix disposed in a distal portion of the apparatus. The method also includes deploying the thrombogenic matrix from the distal portion of the apparatus and into the puncture tract, the thrombogenic matrix being exposed to blood and compressively engaging the tissue surrounding the vessel to prevent leakage of blood.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation application of U.S. patent application Ser. No. 13/615,551, filed Sep. , 13 2012, which is a continuation application of U.S. patent application Ser. No. 12/853,139, filed Aug. 9, 2010, now U.S. Pat. No. 8,323,311, which is a continuation application of U.S. patent application Ser. No. 10/523,219, filed Oct. 19, 2005, now U.S. Pat. No. 7,771,454, which is a 371 Nationalization of PCT/EP2003/008246, filed Jul. 25, 2003, which claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 60/401,226, filed Aug. 1, 2002, the disclosures of which are incorporated herein by this reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. The Field of the Invention 
         [0003]    The present invention relates to apparatus for sealing puncture tracts. More specifically, the invention relates to apparatus that seals a puncture tract by forming and extruding an autologous plug therein. 
         [0004]    2. The Background of the Invention 
         [0005]    A large number of medical diagnostic and therapeutic procedures involve the percutaneous introduction of instrumentation into the blood vessel. For example, coronary angioplasty, angiography, atherectomy, stenting, and numerous other procedures often involve accessing the vasculature through placement of a catheter or other device in a patient&#39;s femoral artery or other blood vessel. Once the procedure is completed and the catheter or other diagnostic or therapeutic device is removed, bleeding from the resultant vascular puncture must be stopped. 
         [0006]    Traditionally, a medical practitioner applies external pressure to the puncture site to stem bleeding until hemostasis occurs (i.e. when the clotting and tissue rebuilding have sealed the puncture). This method, however, presents numerous problems. In some instances, this pressure must be applied for up to an hour or more, during which time the patient is uncomfortably immobilized. In addition, there exists a risk of hematoma since bleeding from the puncture may continue until sufficient clotting occurs, particularly if the patient moves during the clotting process. Furthermore, application of external pressure to stop bleeding may be unsuitable for patients with substantial amounts of subcutaneous adipose tissue since the skin surface may be a considerable distance from the puncture site, thereby rendering external compression less effective. 
         [0007]    Another traditional approach to subcutaneous puncture closure comprises having a medical practitioner internally suture the vessel puncture. This method, however, often requires a complex procedure and requires considerable skill by the medical practitioner. 
         [0008]    Mechanical occlusion devices have been proposed for sealing, e.g., atrial septal defects, and typically comprise two expandable disks that sealingly compress tissue surrounding the hole. One such device is described in U.S. Pat. No. 5,425,744 to Fagan et al. A significant drawback to the Fagan device is that, when deployed into a vessel, the device may protrude into the blood stream, thereby disturbing blood flow and causing thrombosis in the vessel. 
         [0009]    Apparatus and methods also are known in which a plug is introduced into the vessel puncture, to cover the puncture and promote hemostasis. Various types of plugs have been proposed. One example is described in U.S. Pat. No. 5,061,274 to Kensey, comprising a plug made from animal-derived collagen. Such apparatus may be unsuitable for some patients due to an adverse immunological reaction to animal-derived collagen, which could lead to anaphylactic shock. 
         [0010]    U.S. Pat. No. 6,159,232 to Nowakowski describes an apparatus substantially disposed outside a patient&#39;s body that activates a clotting cascade within blood, and then introduces the treated blood to the wound site to complete clotting and promote hemostasis. Disadvantageously, the apparatus described in that patent comprises a multiplicity of primarily standard, off-the-shelf components that a medical practitioner would have to assemble prior to use. This greatly is complicates the procedure, and increases opportunities for human error and contamination. Furthermore, the apparatus resulting from the assembly of the numerous individual components may be unwieldy to use and expensive. 
         [0011]    In view of these drawbacks, it would be desirable to provide apparatus for sealing a puncture tract by forming and extruding an autologous plug within the puncture tract. 
         [0012]    It also would be desirable to provide apparatus for sealing a puncture tract that are easy to use, and decrease opportunities for error and contamination. 
         [0013]    It further would be desirable to provide apparatus for sealing a puncture tract that facilitate placement of the apparatus relative to a vessel. 
         [0014]    It still further would be desirable to provide apparatus for sealing a puncture tract that prevent leakage of blood congealing agents into a vessel during delivery thereof. 
       BRIEF SUMMARY OF THE INVENTION 
       [0015]    In view of the foregoing, it is an object of the present invention to provide apparatus for sealing a puncture tract by forming and extruding an autologous plug within the puncture tract. 
         [0016]    It also is an object of the present invention to provide apparatus for sealing a puncture tract that are easy to use, and decrease opportunities for error and contamination. 
         [0017]    It further is an object of the present invention to provide apparatus for sealing a puncture tract that facilitate placement of the apparatus relative to a vessel. 
         [0018]    It even further is an object of the present invention to provide apparatus for sealing a puncture tract that prevent leakage of blood congealing agents into a vessel during delivery thereof. 
         [0019]    These and other objects of the present invention are accomplished by providing apparatus for sealing a puncture tract by forming and extruding an autologous plug within the puncture tract. More specifically, the apparatus of the present invention forms the autologous plug by drawing blood into the apparatus from a vessel in fluid communication with the puncture tract, and supplying a blood congealing agent to the drawn blood. Consequently, a plug of clotted blood forms within the apparatus, which then may be extruded out of the apparatus and disposed along at least a portion of the length of the puncture tract. 
         [0020]    In a preferred embodiment, the apparatus of the present invention comprises a housing dimensioned to be inserted at least partially into the puncture tract. The housing comprises inner and outer tubes that define an annular lumen. The inner tube comprises a central lumen in which an autologous plug is formed that is then extruded to occlude the puncture tract. The device also comprises a plunger slidably disposed within the central lumen to facilitate drawing blood from the vessel into the central lumen, and extruding the plug from the central lumen into the puncture tract. In alternative embodiments, the annular lumen and/or the outer tube may be omitted. 
         [0021]    To isolate a mixture of blood and blood congealing agent from the vessel during formation of the autologous plug, the device further comprises a closure element, such as a pledget, an iris closure, an alignment closure, or a membrane that is permeable to blood but impermeable to the blood congealing agent. 
         [0022]    To initiate clotting of the drawn blood within the central lumen, a blood congealing agent, such as, e.g., thrombin, fibrin or human factor VIII, may be introduced thereto by injection from an external source, or by pre-coating the central lumen. Alternatively, the central lumen may be lined or pre-loaded with a matrix that is preferably biodegradable, e.g., gauze, bio-compatible foam or spun fiber, or platinum or thermo-resistive wires may be disposed within the wall of the inner tube for contact with the blood therein. 
         [0023]    Disposition of the autologous plug formed from the coagulated blood into the puncture tract seals the puncture tract and vessel from leakage. The tissue surrounding the puncture tract compressively engages the autologous plug along its length, generating frictional forces that prevent the plug from becoming dislodged into the vessel. These and other objects and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0024]    Further features of the present invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments, in which: 
           [0025]      FIG. 1  is a schematic side-sectional view of a vascular puncture tract; 
           [0026]      FIG. 2  is a schematic perspective view of is apparatus of the present invention; 
           [0027]      FIG. 3  is a schematic side-sectional view of the apparatus of  FIG. 2 ; 
           [0028]      FIGS. 4A-4E  are schematic side-sectional views describing an exemplary method of using the apparatus of  FIGS. 2 and 3 ; 
           [0029]      FIGS. 5A-5E  are schematic side-sectional and end views of alternative embodiments of apparatus of the present invention; 
           [0030]      FIG. 6  is a schematic side-sectional view of another alternative embodiment of the apparatus of the present invention; 
           [0031]      FIGS. 7A and 7B  are, respectively, a schematic exploded perspective view and a schematic side-sectional view of an iris closure of the apparatus of  FIG. 6 ; 
           [0032]      FIG. 8A-8C  are schematic plane views of an inner tube and the iris closure, respectively, of the apparatus of  FIGS. 6 and 7 ; 
           [0033]      FIGS. 9A-9D  are schematic side-sectional views describing an exemplary method of using the apparatus of  FIGS. 6-8 ; 
           [0034]      FIGS. 10A and 10B  are schematic side-sectional views of alternative embodiments of the apparatus of  FIGS. 6-9 ; 
           [0035]      FIG. 11  is a schematic side-sectional view of a still further embodiment of the apparatus of the present invention; 
           [0036]      FIGS. 12A and 12B  are schematic cross-sectional views of an alignment closure of the apparatus of  FIG. 11 ; and 
           [0037]      FIGS. 13A and 13B  are, respectively, a schematic side-sectional view and a schematic end view of yet another alternative embodiment of the apparatus of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]    Upon completion of a medical diagnostic or therapeutic procedure involving percutaneous introduction of instrumentation into blood vessel V, removal of the instrumentation from the patient leaves puncture tract TR. As seen in  FIG. 1 , puncture tract TR extends through subcutaneous tissue T and terminates at puncture P. The apparatus of the present invention is directed to a device for sealing puncture tract TR by facilitating formation and disposition of an autologous plug within the puncture tract. More specifically, the apparatus facilitates formation of the plug by drawing blood into a lumen of the apparatus, and providing a blood congealing agent to the blood therein, which causes the blood to clot and form an autologous plug within the lumen. The autologous plug is extruded from the lumen to seal puncture tract TR, thereby sealing vessel V from blood leakage. 
         [0039]    An illustrative embodiment of device  10  of the present invention is shown in  FIGS. 2 and 3 . Device  10  comprises housing  12  having manifold  14 , injection port  16 , and distal opening  18 , plunger  20  having head  21  and shank  23  disposed for axial translation within housing  12 , and pledget  22 . Pledget  22  may be disposed within and is removably coupled to housing  12 . As described in greater detail hereinbelow, fluid communication between distal opening  18  and injection port  16  permits a medical practitioner to easily determine when device  10  has been advanced is within puncture tract TR to a position just proximal to vessel V. 
         [0040]    Housing  12  further comprises inner tube  24  and outer tube  28 , which may be distally tapered to provide an atraumatic bumper for advancement of device  10  through puncture tract TR, or may be distally angled for flush alignment with an angled puncture tract TR, such as the puncture tract of  FIG. 1  Inner and outer tubes  24  and  28  form annular lumen  30 , which is in fluid communication with manifold  14  and injection port  16  Annular lumen  30  extends along the length of inner tube  24  and is in fluid communication with central lumen  26 , via plurality of apertures  32 . Apertures  32  are disposed through and along the axial length of inner tube  24 . Optional gap  34  is defined between the distal ends of inner and outer tubes  24  and  28 . 
         [0041]    Fluid communication between injection port  16  and central lumen  26  permits a blood congealing agent to be injected through injection port  16 , e.g., a luer valve, into blood drawn within central lumen  26 . Mixture and chemical interaction between the blood congealing agent, e.g., thrombin, fibrin and/or human factor VIII, and the blood initiates a clotting reaction that congeals the blood into an autologous plug. The plug is extruded from central lumen  26  into puncture tract TR to seal the vessel puncture. 
         [0042]    In a preferred embodiment, central lumen  26  has a diameter equal to that of distal opening  18 . Once an autologous plug is formed within central lumen  26 , it is extruded into puncture tract TR, where the plug engages compliant tissue T surrounding the puncture tract along its length, thereby retaining the plug within the puncture tract. 
         [0043]    Engagement between the is plug and tissue may be increased by enlarging the diameter of central lumen  26  and distal opening  18 , thereby permitting an increase in the diameter and surface area of the autologous plug that is formed and extruded. The diameter of shank  23  of plunger  20  is selected so that shank  23  may be translated within central lumen  26 , yet prevents blood leakage around proximal opening  36  of central lumen  26 . 
         [0044]    As shown in  FIGS. 2 and 3 , the diameter of central lumen  26  also is dimensioned to permit thread  38  to be translatably disposed between plunger  20  and inner tube  24 . Alternatively, plunger  20  may be provided with a thread lumen (not shown) through which thread  38  may be translatably disposed. Thread  38  exits housing  12  through proximal opening  36 , and is distally attached to loop  40  of pledget  22 . Pledget  22  includes disk  42 , to which loop  40  is coupled, preferably rigidly. 
         [0045]    In a preferred embodiment, disk  42  is elliptically shaped, and has major and minor axes that permit disk  42  to completely cover puncture P when disposed therein. Accordingly, when pledget  22  is engaged to the inner wall of vessel V within puncture p, immediate hemostasis may be achieved. If the minor axis of disk  42  is greater than the diameter of central lumen  26 , disk  42  may be made of a material that permits disk  42  to be elastically deformed to fit within central lumen  26  during delivery of the pledget to vessel V. Once ejected from central lumen  26 , disk  42  elastically recovers its elliptical shape. Of course, in addition to elliptical shapes, it will be evident to one of ordinary skill in the art that disk  42  may comprise other shapes, e.g., circular or oblong, so long as disk  42  can completely occlude puncture P when disposed therein. 
         [0046]    In accordance with one aspect of the present invention, pledget  22  and thread  38  are made of biodegradable materials, e.g., polyglycolic acid. This permits pledget  22  and thread  38  to be resorbed and excreted from the body along with resorption of the autologous plug, after puncture P and tract TR have healed. It will be evident to one of ordinary skill in the art that by controlling parameters such as the degree of polymerization and crystallization, the biodegradable material may be engineered to comprise properties that permit disk  42  to elastically deform when inserted into central lumen  26  during delivery, and to degrade at a predetermined rate. 
         [0047]    Referring now to  FIG. 4 , an exemplary method of using device  10  of the present invention is described. Housing  12  of device  10  optionally may comprise a cross-sectional area greater than that of puncture tract TR, and an introducer sheath (not shown) optionally may be used to introduce device  10  into the puncture tract. If housing  12  is sized such that its cross-sectional area does not exceed that of the puncture tract, the autologous plug formed within central lumen  26  and extruded into the puncture tract, as described hereinbelow, is expected to engage puncture tract TR, e.g. frictionally, via tissue rebound that decreases the diameter of the puncture tract after removal of device  10 . 
         [0048]      FIG. 4A  illustrates device  10  disposed within puncture tract TR, for example, after the introducer sheath has been removed. Pledget  22  is disposed in the distal region of central lumen  26 , and plunger  20  is disposed proximal to pledget  22  within central lumen  26 . Device  10  is inserted into puncture tract TR and distally advanced therethrough until distal opening  18  is disposed just proximal of vessel V within puncture P. Positioning of device  10  may be confirmed by backbleed of blood B from injection port  16 . Specifically, when distal opening  18  is advanced to a position just proximal of vessel V, blood B enters distal opening  18  and backbleeds through gap  34  and annular lumen  30 , into manifold  14  and out of injection port  16 . 
         [0049]    Once device  10  is properly positioned just proximal of vessel V, plunger  20  is distally advanced. Because plunger  20  is disposed proximal pledget  22  within central lumen  26  and the diameter of shank  23  is only slightly less than the diameter of central lumen  26 , distal advancement of plunger  20  also urges pledget  22  into vessel V. Preferably, plunger  20  contacts manifold  14  when pledget  22  has been completely advanced into vessel V. Because disk  42  of pledget  22  is elliptical, disk  42  will tend to align itself with its major axis parallel to the flow of blood, as shown in  FIG. 4B . 
         [0050]    Thereafter, plunger  20  is actuated in the proximal direction to draw blood B from vessel V into central lumen  26 . Due to the presence of apertures  32  and gap  34 , blood also may be drawn into annular lumen  30  and/or manifold  14 . Any air within device  10  may escape therefrom through an air vent (not shown), and/or injection port  16 . 
         [0051]    Once central lumen  26  is filled with blood, a proximal force is applied to the proximal ends of thread  38  disposed outside of puncture tract TR to engage pledget  22  against the inner wall of vessel V, thereby sealing the puncture tract from the vessel and providing immediate hemostasis. Thereafter, source S of a blood congealing agent, such as thrombin, fibrin and/or human factor VIII, is coupled to injection port  16 , and blood congealing agent A is injected into manifold  14 . From manifold  14 , agent A is introduced into blood present in annular lumen  30 , and into central lumen  26  via apertures  32  and gap  34 , where it initiates clotting of the blood therein. Due to the engagement of pledget  22  against the inner wall of vessel V, the blood congealing agent will not leak into vessel V. 
         [0052]    After a period of time, the blood within central lumen  26  solidifies into autologous plug PL, with thread  38  embedded therein. In a preferred embodiment, autologous plug PL comprises a substantially cylindrical rod. Autologous plug PL then may be extruded from device  10  by actuation of plunger  20  and proximal retraction of device  10  from puncture tract TR. 
         [0053]    Once autologous plug PL is extruded from device  10 , it engages compliant tissue T surrounding puncture tract TR, which is expected to retract or rebound after removal of device  10 , thereby establishing a compressive normal pressure between autologous plug PL and tissue T that reduces a risk of the plug becoming dislodged into vessel V. Any extraneous portion of autologous plug PL and thread  38  that proximally protrudes from puncture tract TR may be excised. 
         [0054]    Referring now to  FIG. 5A , an alternative embodiment of the present invention is described. Unlike the previous embodiment, device  44  omits manifold  14  and injection port  16 , and retains plunger  20 , pledget  22 , and thread  38 . Device  44  further comprises housing  52  having inner and outer tubes  46  and  48 , which form annular lumen  50  that extends along the length of inner tube  46  Annular lumen  50  may be fluidically communicative with central lumen  52  via optional plurality of apertures  54 , which may be disposed through and along the axial length of inner tube  46 . Gap  56  is defined between the distal ends of inner and outer tubes  46  and  48 . 
         [0055]    Preferably, outer tube  48  is made from a transparent polymer. In use, this permits a medical practitioner to visually confirm proper placement of device  44  just proximal to vessel V. Specifically, when device  44  is advanced within puncture tract TR to a position just proximal of the vessel, blood backbleeds through opening  58  and gap  56  into annular lumen  50 . If outer tube  48  is transparent, visual confirmation may be made. Air within annular lumen  50  may be evacuated through an air vent (not shown) in fluid communication with annular lumen  50 . 
         [0056]    The blood congealing agent of device  44  includes matrix  60  that is preferably biodegradable. Matrix  60  may comprise, for example, a gauze, a biologically compatible foam, and/or a spun fiber, such as a mass of a loosely spun fiber, e.g. polyglycolic acid. Matrix  60  promotes coagulation of blood upon contact and mixture therewith and optionally may be coated with, e.g., thrombin, fibrin and/or human factor VIII. Matrix  60  may comprise optional inner lumen  62  for disposition of thread  38  of pledget  22  through the matrix. 
         [0057]    During delivery of device  44  into puncture tract TR, matrix  60  is disposed within central lumen  52  between plunger  20  and pledget  22 . Once backbleed of blood into annular lumen  50  confirms that device  44  is positioned just proximal of vessel V, plunger  20  may be distally translated to advance pledget  22  into vessel V. This position, which may be indicated by a marker (not shown) on shaft  23  of plunger  20 , corresponds to placement of matrix  60  just proximal of gap  56 . 
         [0058]    Thereafter, plunger  20  is proximally retracted to draw blood into device  44 . Blood enters through opening  58  and saturates matrix  60  as it flows therethrough into the proximal portion of central lumen  52 . Blood also may be drawn into annular lumen  50  via gap  56 , and introduced into central lumen  52  via apertures  54 , if present. Apertures  54  preferably are disposed along the length of inner tube  46 , such that blood may evenly distribute along the length of central lumen  52 , thereby evenly permeating matrix  60 . Upon contact and mixture of the blood and the matrix, the blood congeals into an autologous plug that integrates matrix  60  therein. The resultant autologous plug is extruded from device  44  and disposed within puncture tract TR to compressively engage the surrounding tissue, thereby preventing leakage of blood therefrom. 
         [0059]    Referring now to  FIG. 5B , an alternative embodiment of device  44  is described. Housing  65  of device  64  is similar to that of the previous embodiment, except that apertures  54  are omitted from inner tube  68  of the present embodiment. Device  64  also comprises plunger  66 , pledget  22 , and flange  70  that facilitates translation of housing  65  within puncture tract TR, and actuation of plunger  66  relative to housing  65 . In the present embodiment, plunger  66  comprises injection port  72  disposed at the proximal end, shank  74  that is translatably disposed within central lumen  52 , and injection lumen  76  disposed therethrough. Injection port  72  may comprise a coupling, such as a luer valve, that can be releasably joined to a source of blood congealing agent (not shown). Thus, instead of injecting blood congealing agent into a manifold as with device  10 , device  64  permits injection directly into plunger  66 , thereby eliminating apertures  32  from device  10  and reserving annular lumen  50  solely to provide visual confirmation of placement of device  64  relative to vessel V. It should be noted that injection lumen  76  also may be used as a thread lumen through which thread  38  attached to pledget  22  may be advanced (not shown). 
         [0060]    In yet another alternative embodiment of the present invention, inner wall  77  of inner tube  68  may be pre-coated with a blood congealing agent, e.g., thrombin, fibrin and/or human factor VIII, or lined with a matrix that is preferably biodegradable (e.g., gauze or biologically compatible foam). This eliminates the need to separately introduce a fluid blood congealing agent into the blood isolated within central lumen  52 , thereby eliminating the need for injection lumen  76  in plunger  66 . Coagulation of blood further may be enhanced by contact with platinum wires  78 , or convection and conduction of heat from thermo-resistive wires  78  disposed within inner tube  68 , as shown in the inset of  FIG. 5B . If thermo-resistive wires are provided, they may be proximally connected to a power source (not shown). 
         [0061]    In a still further alternative embodiment of device  64 , outer tube  48  may be omitted, thereby eliminating annular lumen  50 , as well as gap  56 . Shown in  FIG. 5C , device  80  may be provided with only a single inner tube  68  having central lumen  52  in which shank  74  of plunger  66  may be translatably disposed. In this embodiment, central lumen  52  or injection lumen  76  of plunger  66  also may serve as a backbleed lumen through which blood may pass for visual confirmation of proper placement of device  80  proximate to vessel V. As discussed previously, injection lumen  76  further may be used as a thread lumen for disposition of thread  38  therethrough. 
         [0062]    As with device  64 , blood congealing agent may be introduced to the blood drawn into central lumen  52  by injection of the blood congealing agent into injection lumen  76 , pre-coating or lining the central lumen with the blood congealing agent, e.g., thrombin, fibrin and/or human factor VIII, or exposing the blood to platinum or thermo-resistive wires. Additional techniques will be apparent to those of skill in the art. 
         [0063]    As shown in  FIGS. 5C-5E , the blood congealing agent also may include matrix  82  that is preferably biodegradable, and which is disposed within central lumen  52  between plunger  66  and pledget  22 . Matrix  82  may comprise a gauze, a biologically compatible foam, and/or a spun fiber, e.g. a mass of loosely spun fiber, such as spun polyglycolic acid. Matrix  82  optionally may be coated with, e.g., thrombin, fibrin and/or human factor VIII. Upon contact and mixture with matrix  82 , blood coagulates into an autologous plug, integrating the matrix and thread  38  therein. 
         [0064]    As shown in  FIG. 5D , matrix  82  preferably has a cross-section that incorporates plurality of longitudinal channels  84  and optional inner lumen  83  for disposition of thread  38  of pledget  22  therethrough. Channels  84  provide fluid communication between opening  86 , disposed at the distal end of inner tube  68 , and the proximal portion of central lumen  52 . This permits blood to backbleed through matrix  82  and either injection lumen  76  or central lumen  52  to provide visual confirmation that device  80  is properly positioned just proximal to vessel V prior to actuation of plunger  66  to introduce pledget  22  within vessel V. Channels  84  also facilitate introduction and distribution of blood along the length of matrix  82 , and into the proximal portion of central lumen  52 . Preferably, matrix  82  expands to a substantially circular cross-section after mixture with the blood, thereby eliminating channels  84 . 
         [0065]    It will be evident to one of ordinary skill in the art that, while  FIG. 5D  illustrates a plurality of channels disposed along the circumference of matrix  82 , channels  84  also may include other configurations, such as lumens  86  disposed through the longitudinal length of the matrix, as shown in  FIG. 5E , or a combination thereof. 
         [0066]    Referring now to  FIG. 6 , a still further alternative embodiment of the present invention is described. Like the embodiment of  FIGS. 2 and 3 , device  90  comprises housing  92  having manifold  94  and injection port  96 , and plunger  98  having head  100  and shank  102  disposed for axial translation within housing  92 . Housing  92  includes inner tube  104  and outer tube  106 , wherein inner tube  104  is rotatable but not axially translatable relative to outer tube  106 . Rotation of inner tube  104  may be facilitated by actuator  107  coupled thereto Annular lumen  108  is formed between inner and outer tubes  104  and  106 , and is in fluid communication with manifold  94  and injection port  96  Annular lumen  108  is in fluid communication with central lumen  110  via plurality of apertures  112 , which is disposed through and along the axial length of inner tube  104 . Gap  114  is defined between the distal ends of inner and outer tubes  104  and  106 . 
         [0067]    As in device  10 , the diameter of central lumen  110  is designed to form an autologous plug therein, that engages tissue T when extruded into puncture tract TR. Shank  102  is slightly smaller than that of central lumen  110  and may be translated therein. 
         [0068]    Instead of having a pledget to isolate blood from, and prevent leakage of blood congealing agent into, vessel V, device  90  includes iris closure  118  disposed at the distal end thereof. As shown in greater detail in  FIGS. 7 and 8 , iris closure  118  comprises iris plate  120  rigidly fixed to the distal end of outer tube  106 , having tracks  122  and opening  124  therethrough. Iris closure  118  further comprises overlapping iris blades  126  that may be selectively actuated, as described hereinbelow, to expose or seal opening  124 . Each iris blade  126  comprises distal bearing  128  and proximal bearing  130 . Distal bearing  128  has a non-circular cross-sectional area, e.g., square, that is keyed to iris track  122 . Distal bearing  128  also has end  131 , e.g., a solder ball, having a diameter greater than the width of iris track  122  to prevent disengagement of distal bearing  128  from the iris track during actuation of iris closure  118 . Proximal bearing  130  is configured to extend through gap  114  and into blind slots  132  disposed in the distal end of inner tube  104 . 
         [0069]    As shown in  FIGS. 7A and 8A , slots  132  radially extend through the thickness of inner tube  104  without penetrating into central lumen  110  or annular lumen  108 . As shown in  FIGS. 7A ,  8 B and  8 C, iris tracks  132  extend from opening  124  of iris plate  120  and curve along their respective lengths. The cross-sectional shapes of distal bearings  128  are keyed to iris tracks  122  so that actuation of distal bearings  128  along the iris tracks rotates distal bearings  128  along the curve of the iris tracks (see  FIG. 8C ). Since iris blades  126  are rigidly affixed to distal bearings  128 , rotation of the distal bearings rotates iris blades  126  therewith, thereby exposing or sealing opening  124  depending on the direction of rotation of iris plate  120  relative to slots  132 , or vice versa. 
         [0070]    In operation, to expose opening  124  from its sealed configuration shown in  FIGS. 7B and 8B , inner tube  104  is rotated, e.g., in the counter-clockwise direction relative to outer tube  106 . This causes slots  132  engaged to proximal bearings  130  to impart a tangential force to each bearing  130 . Since proximal bearings  130  are rigidly affixed to iris blades  126 , the tangential forces imparted to bearings  130  force movement of iris blades  126  and distal bearings  128  along the curve of iris tracks  122 . As illustrated in  FIG. 8C , as distal bearings  128  travel therealong, iris blades  126  rotate with the curve of iris tracks  132 , retracting the blades and exposing opening  124 . Contemporaneously, proximal bearings  130  move along slots  132  in the outwardly radial direction. Rotation of inner tube  104  relative to outer tube  106  terminates when distal bearings  128  contact outer ends  134  of iris tracks  122 . At this point, iris blades  126  have been completely retracted to expose opening  124 . 
         [0071]    To seal opening  124 , inner tube  104  is rotated, e.g., in the clockwise direction relative to outer tube  106 . This forces distal bearings  128  to move along the curve of iris tracks  122  in the inwardly radial direction towards opening  124 , rotating iris blades  126  therewith to seal opening  124 . When distal bearings  128  contact inner ends  136  of iris tracks  122 , iris blades  126  have fully sealed opening  124 . 
         [0072]    While iris blades  126  are shown disposed proximal to iris plate  120  in  FIGS. 6 and 7 , it will be evident to one of ordinary skill in the art that iris blades  126  also may be disposed distal to iris plate  120 , with minor design modifications to proximal bearings  130 . Furthermore, it also will be evident that iris blades  126  may comprise numerous shapes other than the teardrop shape illustrated in  FIGS. 7B ,  8 B and  8 C. 
         [0073]    Referring now to  FIG. 9 , an exemplary method of using device  90  is described. As discussed with reference to device  10 , housing  92  of device  90  optionally may comprise a cross-sectional area greater than that of puncture tract TR. Accordingly, an introducer sheath (not shown) may be used to introduce device  90  into puncture tract TR.  FIG. 9A  illustrates device  90  in its delivery configuration after, for example, the introducer sheath has been removed, with iris blades  126  retracted to expose opening  124  within iris plate  120 , and shank  102  of plunger  98  disposed within central lumen  110  just proximal to gap  114 . This position may be indicated by a marker (not shown) disposed on shank  102 , and permits blood to backbleed through gap  114  into annular lumen  108  to facilitate placement of device  90  relative to vessel V. 
         [0074]    In this delivery configuration, device  90  is inserted into puncture tract TR and distally advanced therethrough until opening  124  is disposed just proximal to vessel V, as may be determined by observation of blood B exiting from injection port  96 . In particular, when opening  124  is advanced to a position just proximal to vessel V, blood B enters opening  124  and backbleeds through gap  114  and annular lumen  108 , into manifold  94  and out of injection port  96 . 
         [0075]    Once device  90  is properly positioned just proximal to vessel V, plunger  98  is actuated in the proximal direction to draw blood B from vessel V into central lumen  110 , as seen in  FIG. 9C . Due to the presence of apertures  112  and gap  114 , blood also may be drawn into annular lumen  108  and/or manifold  94 . Any air within device  90  may be expelled therefrom through an air vent (not shown) and/or injection port  96 . 
         [0076]    Once central lumen  110  is filled with blood B, actuator  107  may be used to rotate inner tube  104  relative to outer tube  106 , actuating iris blades  126  to seal opening  124  in the manner discussed above. 
         [0077]    Source S of blood congealing agent is coupled to injection port  96 , and blood congealing agent A is injected into manifold  94 . From manifold  94 , blood congealing agent A mixes with blood present in annular lumen  108  and into central lumen  110 , via apertures  112  and gap  114 , initiating clotting of the blood. Since opening  124  is sealed, thereby isolating the blood within device  90 , blood congealing agent A will not leak into vessel V. After a period of time, the blood within lumen  110  solidifies into autologous plug PL. Accordingly, in a preferred embodiment, autologous plug PL comprises a cylindrical rod. 
         [0078]    Inner tube  104  then is rotated relative to outer tube  106  to expose opening  124  in the manner discussed above. Autologous plug PL is extruded from central lumen  110  by holding plunger  98  stationary as housing  92  is proximally retracted so that plunger  98  urges autologous plug PL out of lumen  110 , as seen in  FIG. 9D . Any blood contiguously coagulated with autologous plug PL, such as that potentially disposed within annular lumen  108 , apertures  112 , and gap  114 , is expected to shear off when plug PL is extruded out of device  90 . 
         [0079]    Once autologous plug PL is extruded from device  90 , it engages compliant tissue T surrounding puncture tract TR, which is expected to retract or rebound after removal of device  90 , thereby establishing a compressive normal pressure between autologous plug PL and tissue T that reduces a risk of the plug becoming dislodged into vessel V. Any extraneous portion of autologous plug PL that proximally protrudes from puncture tract TR may be excised. 
         [0080]    Referring now to  FIG. 10A , a further is alternative embodiment of the present invention is described. Device  140  is similar to the preceding embodiment, except manifold  94  and apertures  112  have been omitted. Device  140  includes iris closure  142  having iris blades  146  operably engaged to iris plate  148 , which includes opening  150  and a plurality of iris tracks similar to those described in  FIGS. 7 and 8 . Iris closure  142  is disposed on the distal end of housing  152  having inner tube  154 , outer tube  156  which is rotatable but not axially translatable relative to inner tube  154 , and annular lumen  158  disposed therebetween. Operated in the same manner as described previously with reference to  FIGS. 7 and 8 , rotation of inner tube  154 , which may be facilitated by actuator  159  coupled thereto, actuates iris closure  142  to expose or seal opening  150 , depending on the direction of rotation of inner tube  154  relative to outer tube  156 . The distal ends of inner and outer tubes  154  and  156  define gap  160 , which provides fluid communication among opening  150 , annular lumen  158  and central lumen  162  of inner tube  154 . 
         [0081]    Preferably, outer tube  156  is made from a transparent polymer to facilitate visual confirmation of the advancement of device  140  to a position just proximal to vessel V in puncture tract TR. In use, when opening  150  is disposed just proximal to vessel V, blood backbleeds through opening  150  and gap  160  into annular lumen  158 . Air within annular lumen  158  may be evacuated through an air vent (not shown) in fluid communication therewith. 
         [0082]    Device  140  also comprises plunger  164  and flange  166  that facilitates insertion of housing  152  within puncture tract TR. In the present embodiment, plunger  164  comprises injection port  168  disposed at the proximal end, shank  170  that is configured to be translatably disposed within central lumen  162 , and injection lumen  172  disposed therethrough. Injection port  168  may comprise a coupling, such as a luer valve, that can be releasably joined to a source of blood congealing agent (not shown). Accordingly, instead of injecting blood congealing agent into a manifold as in the preceding embodiment, device  140  permits injection directly into plunger  164 , thereby eliminating apertures  112  from device  90  and reserving annular lumen  158  solely to provide visual confirmation of the disposition of device  140  just proximal to vessel V. 
         [0083]    In an alternative embodiment of device  140 , inner wall  174  may be pre-coated with a blood congealing agent, e.g., thrombin, fibrin and/or human factor VIII, or lined with a matrix (e.g., gauze, spun fiber or biologically compatible foam). This eliminates the need to introduce a blood congealing agent into the blood isolated within central lumen  162 , thereby eliminating the need for injection lumen  172  in plunger  164 . Coagulation of blood further may be enhanced by contact with platinum wires  176 , or convection and conduction of heat from thermo-resistive wires  176  disposed within inner tube  154 , as shown in the inset of  FIG. 10A . Alternatively, central lumen  162  may be pre-filled with a matrix to promote coagulation of blood upon contact and mixture therewith, as described hereinabove with respect to FIGS.  5 A and  5 C- 5 E. 
         [0084]    In an alternative embodiment of device  140 , annular lumen  158  and gap  160  may be omitted. Shown in  FIG. 10B , device  178  includes inner and outer tubes  154  and  156  adjacently disposed, and iris closure  142  operably coupled to the distal ends thereof. Central lumen  162  or injection lumen  172  of plunger  164  may serve as a backbleed lumen through which blood may pass for visual confirmation of proper placement of device  178  proximate vessel V. 
         [0085]    As in device  140 , blood congealing agent may be introduced to the blood drawn into central lumen  162  by injection of the blood congealing agent into injection lumen  172 , pre-coating or lining the central lumen with the blood congealing agent, e.g., thrombin, fibrin, human factor VIII, and/or a matrix (e.g., gauze, spun fiber or biologically compatible foam), or exposing the blood to platinum or thermo-resistive wires. Alternatively, central lumen  162  may be pre-filled with a matrix to promote coagulation of blood upon contact and mixture therewith, as described hereinabove with respect to FIGS.  5 A and  5 C- 5 E. 
         [0086]    Referring now to  FIG. 11 , another embodiment of the apparatus of the present invention is described. Device  180  is similar to devices  90  and  140  respectively of  FIGS. 6-8  and  10 , except that the iris closures of those embodiments are replaced by alignment closure  182 . Affixed to the distal end of inner tube  184  is proximal plate  186  having through-wall slots  188 . Affixed to the distal end of outer tube  190  is distal plate  192  having through-wall slots  194  that have a shape identical to that of slots  188 . When slots  188  and  194  are aligned, as shown in  FIGS. 11 and 12A , blood may be drawn into central lumen  196  disposed through the length of inner tube  184 , or an autologous plug may be extruded therethrough. When inner tube  184  is rotated relative to outer tube  190 , distal and proximal plates  192  and  186  respectively obscure slots  188  and  194 , as shown in  FIG. 12B . In this configuration, blood is isolated within central lumen  196 , and blood congealing agent may be supplied to the isolated blood to initiate clotting thereof. 
         [0087]    Optional annular lumen  198  is defined by inner and outer tubes  184  and  190 , and is in fluid communication with central lumen  196  via optional apertures  200  circumferentially disposed through inner tube  184  just proximal to proximal plate  186 . To determine if device  180  has been properly positioned just proximal to vessel V, blood may backbleed through aligned slots  188  and  194  and apertures  200  into annular lumen  198 . Accordingly, during delivery of device  180  into a puncture tract, the maximum distal position to which plunger  202  may be advanced within central lumen  196  is a position just proximal to apertures  200 . This position may be indicated by a marker (not shown) disposed on plunger  202 . As will be apparent to those of skill in the art, rather than having annular lumen  198  for backbleed indication, central lumen  196  of device  180  may serve as a backbleed lumen. Alternatively, a lumen may be provided through plunger  202  for backbleed indication and/or injection of a blood congealing agent, as described with respect to  FIGS. 5B-5C  and  10 A- 10 B. 
         [0088]    In operation, device  180  is inserted into puncture tract TR with slots  188  and  194  aligned, and plunger  202  disposed just proximal to apertures  200 . Device  180  then is advanced to a position just proximal to vessel V. This position may be visually confirmed by observation of blood that backbleeds through slots  188  and  194  and, for example, apertures  200  into annular lumen  198  and/or out of a proximal injection port (not shown) in fluid communication with annular lumen  198 . Plunger  202  then may be proximally retracted within central lumen  196  to draw blood therein from vessel V. Once central lumen  196  is filled, inner tube  184  is rotated relative to outer tube  190  to obscure slots  188  and  194 , thereby isolating the drawn blood within device  180 . Clotting of the blood may be initiated by introducing blood congealing agent into central lumen  196 . Alternatively, the inner wall of inner tube  184  may be pre-coated with a blood congealing agent, e.g., thrombin, fibrin and/or human factor VIII, lined with a matrix (e.g., gauze, spun fiber or biologically compatible foam), or comprise platinum or thermo-resistive wires that are exposed to the blood therein. When the blood has solidified to form autologous plug PL, inner tube  184  is rotated relative to outer tube  190  to align slots  188  and  194 . Plunger  202  is held stationary as device  180  is proximally retracted from puncture tract TR, thereby urging autologous plug PL from central lumen  196  through slots  188  and  194 . Once disposed within puncture tract TR, the segments of the autologous plug that had been extruded through slots  188  and  194  are urged together due to the compressive pressure of tissue T surrounding the puncture tract. In this manner, puncture tract TR is sealed from leakage of blood. 
         [0089]    Referring now to  FIG. 13 , yet another alternative embodiment of the present invention is described. Device  210  includes housing  212  having inner and outer tubes  214  and  216 , which form annular lumen  218  therebetween. Device  210  also includes plunger  220  translatably disposed within central lumen  222 , and membrane  224 , which is preferably biodegradable. Membrane  224  is disposed over distal opening  226  of central lumen  222  and is releasably attached to inner wall  228  of inner tube  214  so that membrane  224  forms a sock within which is disposed blood congealing agent  230 . Membrane  224  is preferably attached to inner wall  228  with a biodegradable adhesive or suture that permits the membrane to be sheared from inner wall  228  when an axial force is applied to blood congealing agent  230 . 
         [0090]    Membrane  224  is permeable to blood but impermeable to blood congealing agent  230 , thereby permitting blood to be introduced into central lumen  222  and yet isolating the mixture of blood and blood congealing agent from vessel V. Selective permeability may be achieved, for example, by incorporating pores of a predetermined size within membrane  224 . Thus, for example, the pores preferably have a cross-sectional dimension larger than the diameter of blood cells, but smaller than the diameter or cross-sectional dimension of the blood congealing agent, which also preferably may be provided with a predetermined size. Blood cells typically have a diameter of about 60 gm. A pore size greater than about 60 gm is therefore preferred. 
         [0091]    Preferably, blood congealing agent  230  comprises a biodegradable matrix to promote coagulation of blood upon contact and mixture therewith, as described hereinabove with respect to FIGS.  5 A and  5 C- 5 E. Alternatively, blood congealing agent  230  also may comprise powder of a blood congealing substance, such as polyglycolic acid, fibrin, thrombin and/or human factor VIII. 
         [0092]    Outer tube  216  preferably is made from a transparent polymer to permit observation of blood that backbleeds into annular lumen  218  when device  210  is disposed just proximal to vessel V. This provides a medical practitioner with visual confirmation of proper placement of device  210  within puncture tract TR. Optionally, inner tube  214  also may comprise apertures  232  disposed along the length thereof. Apertures  232  provide fluid communication between annular lumen  218  and central lumen  222 . During proximal retraction of plunger  220 , blood may be drawn through apertures  232  and blood permeable membrane  224  into central lumen  222  to more evenly distribute the blood along the length of central lumen  222  and to evenly permeate blood congealing agent  230 . 
         [0093]    In operation, device  210  is introduced into puncture tract TR with plunger  220  disposed within central lumen  222  just proximal to blood congealing agent  230 . Device  210  is distally translated along the puncture tract until backbleeding, e.g. through annular lumen  218 , indicates that the device is properly positioned just proximal to vessel V. Plunger  220  then is actuated in the proximal direction to draw blood into central lumen  222  through membrane  224 , covering distal opening  226 , as well as apertures  232 , if present. Contact and mixture with blood congealing agent  230  coagulates the blood into an autologous plug, integrating blood congealing agent  230  and membrane  224  therein. When plunger  220  is translated in the distal direction to extrude the formed autologous plug from central lumen  222 , the distal force transmitted to the adhesive or suture binding membrane  224  to inner wall  228  shears membrane  224  therefrom. Disposed within puncture tract TR, the autologous plug engages tissue T surrounding the puncture tract to prevent blood leakage from vessel V. 
         [0094]    In an alternative embodiment of device  210 , outer tube  216  and apertures  232  may be omitted, thereby eliminating annular lumen  218 . For backbleed indication to facilitate visual confirmation of the placement of the present device just proximal to vessel V, plunger  220  may be provided with an injection lumen like that described with respect to  FIGS. 5B-5C  and  10 A- 10 B. 
         [0095]    While preferred illustrative embodiments of the invention are described above, it will be apparent to one skilled in the art that various changes and modifications may be made therein without departing from the invention. For example, shorter autologous plugs may be formed that only cover a portion of the length of the puncture tract. Furthermore, various blood congealing agents described hereinabove and known to those in the art may be used in combination in a single embodiment. The appended claims are intended to cover all such changes and modifications that fall within the true spirit and scope of the invention.