Abstract:
Methods and apparatus for making an anastomotic connection between tubular fluid conduits in a patient. A connector may provided having an annular structure configured for placement partially within one of the tubular fluid conduits and for annular enlargement by expansion of an expandable structure positioned within an interior portion of the connector. The connector may be configured for plastic annular enlargement, and have members with free end portions that are configured to penetrate a wall of the tubular fluid conduits at locations that are annularly spaced around the connection. A portion of the connector may be selectively deflected radially out from a remainder of the connector in response to expansion of the expandable structure disposed inside the connector. An axial portion of the connector may be adapted for insertion within an axial end of a first one of the tubular fluid conduits, and an axial portion of the connector may be adapted for insertion through an opening in a wall of a second one of the tubular fluid conduits.

Description:
This application is a continuation of U.S. application Ser. No. 08/745,618, filed Nov. 7, 1996, U.S. Pat. No. 5,976,178. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to grafts for use in the repair, replacement, or supplement of a medical patient&#39;s natural body organ structures or tissues. The invention also relates to methods for making graft structures. The invention further relates to methods and apparatus for delivering a graft to an operative site in a patient, and for installing the graft at that site. Some aspects of the invention may have other uses such as for viewing the interior of a patient, providing access to the interior of a patient for other procedures, etc. An example of the possible uses of the invention is a minimally invasive cardiac bypass procedure. This example will be considered in detail, but it will be understood that various aspects of the invention have many other possible uses. 
     Several procedures are known for revascularizing the human heart in order to treat a patient with one or more occluded coronary arteries. The earliest of these procedures to be developed involves exposing the heart by means of a midline sternotomy. Following surgical exposure of the heart, the patient&#39;s aorta and vena cava are connected to a heart/lung machine to sustain vital functions during the procedure. The beating of the heart is stopped to facilitate performance of the procedure. Typically, a suitable blood vessel such as a length of the patient&#39;s saphenous (leg) vein is harvested for use as a graft. The graft is used to create a new, uninterrupted channel between a blood source, such as the aorta, and the occluded coronary artery or arteries downstream from the arterial occlusion or occlusions. 
     A variation of the above procedure involves relocating a mammary artery of the patient to a coronary artery. 
     Although the above-described sternotomy procedures are increasingly successful, the high degree of invasiveness of these procedures and the requirement of these procedures for general anesthesia are significant disadvantages. Indeed, these disadvantages preclude use of sternotomy procedures on many patients. 
     More recently, less invasive procedures have been developed for revascularizing the heart. An example of these procedures is known as thoracostomy, which involves surgical creation of ports in the patient&#39;s chest to obtain access to the thoracic cavity. Specially designed instruments are inserted through the ports to allow the surgeon to revascularize the heart without the trauma of a midline sternotomy. Drugs may be administered to the patient to slow the heart during the procedure. Some thoracostomy procedures involve relocating a mammary artery to a coronary artery to provide a bypass around an occlusion in the coronary artery. 
     Thoracostomy bypass procedures are less traumatic than sternotomy bypass procedures, but they are still too traumatic for some patients. Also, the number of required bypasses may exceed the number of mammary arteries, thereby rendering thoracostomy procedures inadequate to fully treat many patients. 
     Another technique for revascularizing the human heart involves gaining access to the thoracic cavity by making incisions between the patient&#39;s ribs. This procedure is known as thoracotomy. It is also substantially less traumatic than midline sternotomy, but it is still too traumatic for some patients. 
     In view of the foregoing, it is an object of this invention to provide less traumatic methods and apparatus for revascularizing a patient. 
     It is another object of the invention to provide minimally invasive methods and apparatus for repairing, replacing, or supplementing the blood vessels or other body organ tubing or tissues of a patient. 
     It is still another object of the invention to provide improved graft structures for use in the repair, replacement, or supplementing of natural body organ structures or tissues, and to provide methods for making such graft structures. 
     It is yet another object of the invention to provide improved methods and apparatus for transporting or delivering and installing graft structures for use in the repair, replacement, or supplementing of natural body organ structures or tissues of a patient. 
     SUMMARY OF THE INVENTION 
     These and other objects of the invention are accomplished in accordance with the principles of the invention by providing methods and apparatus for substantially non-surgically installing a new length of tubing in a patient between two sections of the patient&#39;s existing body organ tubing, the new length of tubing being delivered to the operative site by passing along existing tubing, but installed at the operative site so that it is at least partly outside the existing tubing. (As used herein, references to a patient&#39;s existing body organ tubing or the like include both natural and previously installed graft tubing (whether natural, artificial, or both). A previous installation of graft tubing may have occurred in a previous procedure or earlier in a current and on-going procedure. References to a length of tubing also include plural lengths of tubing.) At one end of the operative site, the new length of tubing is caused to extend out through an opening made in the existing tubing. The outwardly extending end portion of the new tubing is guided to the other end of the operative site. At that other end another opening is made in the existing tubing and the extending end portion of the new tubing is attached to the existing tubing via that opening. The other end portion of the new tubing (remote from the extending portion) is similarly attached to the existing tubing at the first-described opening. The new tubing installation is now complete, and the apparatus used to make the installation can be withdrawn from the patient. 
     In the most preferred embodiment, all or substantially all necessary apparatus is inserted into the patient via the patient&#39;s existing body organ tubing. In addition, all or substantially all apparatus functions at the operative site are remotely controlled by the physician (a term used herein to also include supporting technicians) from outside the patient&#39;s body. 
     Preferred apparatus in accordance with the invention includes a first elongated instrument for extending through the patient&#39;s existing body organ tubing to a first end of the operative site, and a second elongated instrument for similarly extending through the patient&#39;s existing tubing to a second end of the operative site. Each instrument includes a structure capable of penetrating the existing tubing at the associated end of the operative site. In addition, these structures are capable of interengaging with one another outside the existing tubing to provide a substantially continuous structural path from outside the patient, along the patient&#39;s existing tubing, and then outside that tubing from one end to the other of the operative site. This structure is used to guide the new length of tubing into the patient and into position at the operative site. 
     At least one of the elongated instruments preferably includes mechanisms for fastening each end portion of the new length of tubing to the adjacent existing body organ tubing. For example, these mechanisms may activate fasteners on or associated with the new tubing. 
     The new tubing may be artificial graft tubing. Alternatively, the new tubing may be natural body organ tubing (e.g., tubing harvested from another location in the patient&#39;s body). As still another alternative, the new tubing may be a combination of artificial and natural tubing (e.g., natural tubing disposed substantially concentrically inside artificial tubing). 
     A preferred form of artificial tubing includes a tube frame of a first highly elastic material (such as nitinol) covered with a second highly elastic material (such as silicone rubber) to substantially fill in the apertures in the frame. This combination produces an artificial graft that is distensible like natural body organ tubing such as a natural artery. The covering on the frame is preferably made porous to a predetermined degree to improve its bio-utility in this context. A preferred method of providing such porosity is to make the covering from an elastic material that is mixed with particles of a material that can be removed (e.g., by vaporization) after the covering has been applied to the mesh. When the particles are removed, voids are left in the covering that give it the desired porosity. 
     The artificial grafts of this invention may be coated (in the case of tubular grafts, on the inside and/or outside) to still further enhance their bioutility. Examples of suitable coatings are medicated coatings, hydrophylic coatings, smoothing coatings, collagen coatings, human cell seeding coatings, etc. The above-described preferred porosity of the graft covering helps the graft to retain these coatings. Additional advantages of the artificial grafts of this invention are their elasticity and distensibility (mentioned above), their ability to be deployed through tubes of smaller diameter (after which they automatically return to their full diameter), the possibility of making them modular, their ability to accept natural body organ tubing concentrically inside themselves, their ability to support development of an endothelial layer, their compatibility with MRI procedures, their ability to be made fluoroscopically visible, etc. 
     Although grafts in the form of tubing are described above, certain aspects of the invention are equally applicable to other graft procedures and to grafts having other shapes. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a simplified longitudinal sectional view showing a portion of an illustrative procedure and related apparatus in accordance with this invention. 
     FIG. 2 is a simplified longitudinal sectional view showing a portion of a more particular illustrative procedure and related apparatus in accordance with the invention. 
     FIG. 3 is a simplified longitudinal sectional view showing an illustrative embodiment of a portion of the FIG. 2 apparatus in more detail. 
     FIG. 3 a  is a view similar to FIG. 3 showing an alternative illustrative embodiment of the FIG. 3 apparatus. 
     FIG. 4 is a simplified elevational view showing an illustrative embodiment of a portion of the FIG. 3 apparatus in still more detail. 
     FIG. 5 is a simplified longitudinal sectional view showing another portion of an illustrative procedure and related apparatus in accordance with this invention. 
     FIG. 6 is a view similar to FIG. 2 showing a later stage in the illustrative procedure depicted in part by FIG. 2, together with related apparatus, all in accordance with this invention. 
     FIG. 7 a  is a simplified longitudinal sectional view of an illustrative embodiment of a portion of the FIG. 6 apparatus in more detail. 
     FIG. 7 b  is a simplified elevational view of a portion of the FIG. 7 a  apparatus, but with the depicted elements in a different physical relationship to one another. 
     FIG. 7 c  is a simplified longitudinal sectional view of an alternative embodiment of one component of the FIG. 7 a  apparatus. 
     FIG. 7 d  is a simplified longitudinal sectional view of an alternative embodiment of another component of the FIG. 7 a  apparatus. 
     FIG. 7 e  is a simplified elevational view of another alternative embodiment of the component shown in FIG. 7 d.    
     FIG. 7 f  is a simplified elevational view of an alternative embodiment of still another component shown in FIG. 7 a.    
     FIG. 7 g  is a simplified elevational view of an alternative embodiment of yet another component shown in FIG. 7 a.    
     FIG. 8 is a simplified longitudinal sectional view similar to a portion of FIG. 6 showing a still later stage in the illustrative procedure depicted in part by FIG.  6 . 
     FIG. 8 a  is a simplified sectional view of the apparatus shown in FIG. 8 without the associated tissue structure being present. 
     FIG. 9 is a simplified cross sectional view of an illustrative embodiment of further illustrative apparatus in accordance with this invention. 
     FIG. 10 is a simplified longitudinal sectional view of an illustrative embodiment of a portion of the FIG. 9 apparatus. 
     FIG. 10 a  is a view similar to FIG. 10 showing a possible alternative construction of the FIG. 10 apparatus. 
     FIG. 10 b  is another view similar to FIG. 10 showing another possible alternative construction of the FIG. 10 apparatus. 
     FIG. 10 c  is another view similar to FIG. 10 showing still another possible alternative construction of the FIG. 10 apparatus. 
     FIG. 11 is a view similar to FIG. 6 showing an even later stage in the illustrative procedure depicted in part by FIG. 8, together with related apparatus, all in accordance with this invention. 
     FIG. 12 is a view similar to a portion of FIG. 11, but in somewhat more detail, showing a still later stage in the illustrative procedure depicted in part by FIG.  11 . 
     FIG. 12 a  is a view similar to FIG. 12 showing a possible alternative construction of the FIG. 12 apparatus. 
     FIG. 13 is a view similar to FIG. 12 showing an even later stage in the illustrative procedure depicted in part by FIG.  12 . 
     FIG. 14 is a view similar to FIG. 11 showing a still later stage in the illustrative procedure depicted in part by FIG.  13 . 
     FIG. 15 is a simplified longitudinal sectional view of an illustrative embodiment of a portion of still further illustrative apparatus in accordance with this invention. 
     FIG. 15 a  is a simplified elevational view of a structure which can be used to provide part of the apparatus shown in FIG.  15 . 
     FIG. 15 b  is a view similar to FIG. 15 a  showing more of the structure of which FIG. 15 a  is a part. 
     FIG. 15 c  is a view similar to FIG. 15 b  showing the FIG. 15 b  structure in another operational condition. 
     FIG. 15 d  is a simplified elevational view of an alternative structure which can be used to provide part of the apparatus shown in FIG.  15 . 
     FIG. 15 e  is a view similar to FIG. 15 d  showing the FIG. 15 d  structure in another operational condition. 
     FIG. 15 f  is a simplified longitudinal sectional view of another alternative structure which can be used to provide part of the apparatus shown in FIG.  15 . 
     FIG. 15 g  is a view similar to FIG. 15 f  showing the FIG. 15 f  structure in another operational condition. 
     FIG. 16 is a simplified elevational view of an illustrative embodiment of one component of the FIG. 15 apparatus. 
     FIG. 17 is a simplified longitudinal sectional view of an illustrative embodiment of another portion of the FIG. 15 apparatus. 
     FIG. 18 is a view similar to a portion of FIG. 14 showing an even later stage in the illustrative procedure depicted in part by FIG.  14 . 
     FIG. 19 is a view similar to FIG. 18 showing a still later stage in the FIG. 18 procedure. 
     FIG. 20 is a view similar to FIG. 19 showing an even later stage in the FIG. 19 procedure. 
     FIG. 21 is a view similar to another portion of FIG. 14 showing a still later stage in the FIG. 20 procedure. 
     FIG. 22 is a view similar to FIG. 21 showing an even later stage in the FIG. 21 procedure. 
     FIG. 22 a  is a view similar to FIG. 22 showing a still later stage in the FIG. 22 procedure. 
     FIG. 22 b  is a view similar to FIG. 22 a  showing an even later stage in the FIG. 22 a  procedure. 
     FIG. 23 is a view similar to FIG. 22 b  showing a still later stage in the FIG. 22 b  procedure. 
     FIG. 24 is a view similar to FIG. 23 showing an even later stage in the FIG. 23 procedure. 
     FIG. 25 is a simplified longitudinal sectional view of an illustrative embodiment of a portion of more apparatus in accordance with this invention. 
     FIG. 26 is a view similar to FIG. 20 showing a later stage in the FIG. 24 procedure. 
     FIG. 27 is a view similar to FIG. 26 showing a still later stage in the FIG. 26 procedure. 
     FIG. 28 is a view similar to FIG. 24 showing an even later stage in the FIG. 27 procedure. 
     FIG. 29 is a view similar to FIG. 28 showing a still later stage in the FIG. 28 procedure. 
     FIG. 30 is a view similar to FIG. 29 showing an even later stage in the FIG. 29 procedure. 
     FIG. 31 is a view similar to FIG. 14 showing the end result of the procedure depicted in part by FIG.  30 . 
     FIG. 32 is a simplified longitudinal sectional view showing an end result similar to FIG. 31 but in a different context. 
     FIG. 33 is a simplified longitudinal sectional view showing a possible alternative construction of portions of the apparatus showing in FIG.  15 . 
     FIG. 34 is a simplified elevational view (partly in section) showing another possible alternative construction of portions of the FIG. 15 apparatus. 
     FIG. 35 is a simplified longitudinal sectional view of the FIG. 34 apparatus in another operating condition. 
     FIG. 36 is a simplified elevational view of apparatus which can be used as an alternative to certain apparatus components shown in FIGS. 15 and 17. 
     FIG. 37 is a simplified elevational view (partly in section) showing additional components with the FIG. 36 apparatus. 
     FIG. 38 is a simplified longitudinal sectional view showing still another possible alternative construction of portions of the FIG. 15 apparatus. 
     FIG. 39 is a simplified elevational view showing in more detail a possible construction of a portion of the FIG. 38 apparatus. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Because the present invention has a number of different applications, each of which may warrant some modifications of such parameters as instrument size and shape, it is believed best to describe certain aspects of the invention with reference to relatively generic schematic drawings. To keep the discussion from becoming too abstract, however, and as an aid to better comprehension and appreciation of the invention, references will frequently be made to specific uses of the invention. Most often these references will be to use of the invention to provide a bypass around an occlusion or obstruction (generically referred to as a narrowing) in a patient&#39;s coronary artery, and in particular a bypass from the aorta to a point along the coronary artery which is downstream from the coronary artery narrowing. It is emphasized again, however, that this is only one of many possible applications of the invention. 
     Assuming that the invention is to be used to provide a bypass from the aorta around a coronary artery narrowing, the procedure may begin by inserting an elongated instrument into the patient&#39;s circulatory system so that a distal portion of the instrument extends through the coronary artery narrowing to the vicinity of the point along the artery at which it is desired to make the bypass connection. This is illustrated by FIG. 1 which shows elongated instrument  100  entering the patient&#39;s circulatory system  10  at a remote location  12  and passing coaxially along vessels in the circulatory system until its distal end portion  104  passes through narrowing  22  in coronary artery  20  and reaches the downstream portion  24  of the artery to which it is desired to make a bypass connection. For example, the entry location  12  of instrument  100  may be a femoral (leg) artery of the patient, a brachial artery of the patient, or any other suitable entry point. It will be appreciated, however, that entry point  12  is typically remote from the location at which the bypass is to be provided, and that control of instrument  100  throughout its use is from the proximal portion  102  that is outside the patient at all times. 
     For the illustrative procedure being discussed, FIG. 2 shows a preferred embodiment of instrument  100  in more detail. As shown in FIG. 2, instrument  100  may include a catheter tube  110  which is inserted (from location  12  in FIG. 1) via the patient&#39;s aorta  30  to the ostium of coronary artery  20 . Another tubular structure  120  is then extended from the distal end of catheter  110 , through narrowing  22  to location  24 . 
     An illustrative construction of tubular structure  120  is shown in more detail in FIG.  3 . There it will be seen that structure  120  may have two lumens  130  and  140 . Near the distal end of structure  120 , lumen  130  communicates with the interior of an inflatable balloon  132  on one side of structure  120 , while lumen  140  opens out to the opposite side of structure  120 . Lumen  140  contains a longitudinal structure  150  which may be a stylet wire with a sharpened distal tip  152  (see FIG.  4 ). (Although FIG. 4 shows indentations behind tip  152 , those indentations could be eliminated if desired.) Structure  120  may be provided with a distal spring tip  122  to help guide the distal end of structure  120  along coronary artery  20  and through narrowing  22 . A safety ribbon  123  (e.g., of the same material as tip  122 ) may be connected at its proximal end to the distal end of member  120  and at its distal end to the distal end of tip  122  to improve the performance of tip  122  and to help prevent separation of any portion of tip  122  from structure  120  in the event of damage to tip  122 . Structure  120  may have radiologic (e.g., radio-opaque or fluoroscopically viewable) markers  124  at suitable locations to help the physician place the structure where desired in the patient&#39;s body. Catheter  110  may also have radiologic markers  112  for similar use. Balloon  132  is initially deflated. Longitudinal structure  150  is initially retracted within lumen  140 . However, the distal portion of lumen  140  is shaped (as indicated at  142  in FIG. 3) to help guide the distal tip  152  of structure  150  out to the side of structure  120  when structure  150  is pushed distally relative to structure  120 . This is discussed in more detail below. As earlier description suggests, each of components  110 ,  120 , and  150  is separately controllable from outside the patient, generally indicated as region  102  in FIG.  1 . 
     As an alternative to providing balloon  132  as an integral part of one structure  120 , balloon  132  may be provided on another longitudinal structure  120 ′ (FIG. 3 a ) which is substantially parallel to the remaining components described above for structure  120 . Structure  120 ′ may be substantially separate from structure  120 , or it may be attached to structure  120 . 
     After instrument  100  is positioned as shown in FIGS. 1 and 2, a second elongated instrument  200  is similarly introduced into the patient&#39;s circulatory system  10  as shown generally in FIG.  5 . For example, instrument  200  may enter the patient (at  14 ) via a femoral artery, a brachial artery, or any other suitable location, which again is typically remote from the bypass site. If one femoral artery is used to receive instrument  100 , the other femoral artery may be used to receive instrument  200 . Or the same femoral artery may be used to receive both instruments. Or any other combination of entry points may be used for the two instruments. Instrument  200  is inserted until its distal end is adjacent to the point  34  in the circulatory system which it is desired to connect to point  24  via a bypass. This is illustrated in a more specific example in FIG. 6 where the distal end of instrument  200  is shown at location  34  in aorta  30 . The particular location  34  chosen in FIG. 6 is only illustrative, and any other location along aorta  30  may be selected instead. Radiologic markers  206  may be provided on the distal portion of instrument  200  to help the physician position the instrument where desired. Note that FIG. 6 shows portions of instruments  100  and  200  side by side in aorta  30 . 
     An illustrative construction of instrument  200  is shown in more detail in FIG. 7 a . This FIG. shows the distal portions of elements  220 ,  230 ,  240 , and  250  telescoped out from one another and from the distal end of outer member  210  for greater clarity. It will be understood, however, that all of these elements are initially inside of one another and inside outer member  210 . Indeed, member  210  may be initially positioned in the patient without any or all of elements  220 ,  230 ,  240 , and  250  inside, and these elements may then be inserted into member  210 . Moreover, the number of members like  220 ,  230 , etc., may be more or less than the number shown in FIG. 7 a , depending on the requirements of a particular procedure. 
     Outer member  210  may be a catheter-type member. The distal portion of catheter  210  may carry two axially spaced annular balloons  212  and  214 . Proximal balloon  212  is inflatable and deflatable via inflation lumen  216  in catheter  210 . Distal balloon  214  is inflatable and deflatable via inflation lumen  218  in catheter  210 . Lumens  216  and  218  are separate from one another so that balloons  212  and  214  can be separately controlled. Balloons  212  and  214  are shown substantially deflated in FIG. 7 a . The distal end of catheter  210  may be tapered as shown at  211  in FIG. 7 c  to facilitate passage of catheter  210  through an aperture in aorta  30  as will be described below. 
     Coaxially inside catheter  210  is tubular sheath member  220 . Sheath  220  is longitudinally movable relative to catheter  210 . The distal portion of sheath  220  may be tapered as shown at  222  in FIG. 7 d , and/or externally threaded as shown at  224  in FIG. 7 e . Either or both of features  222  and  224  may be provided to facilitate passage of sheath  220  through an aperture in aorta  30  as will be described below. If threads  224  are provided, then sheath  220  is rotatable (either alone or with other components) about the longitudinal axis of instrument  200  in order to enable threads  224  to engage the tissue of the aorta wall and help pull sheath  220  through the aorta wall. 
     Coaxially inside sheath member  220  is power steering tube  230 . Tube  230  is longitudinally movable relative to sheath  220 . Tube  230  may also be rotatable (about the central longitudinal axis of instrument  200 ) relative to sheath  220 , and the distal end of tube  230  may be threaded on the outside (as shown at  232  in FIG. 7 f ) for reasons similar to those for which threading  224  may be provided on sheath  220 . Tube  230  is preferably controllable from its proximal portion (outside the patient) to deflect laterally by a desired amount to help steer, push, or twist instrument  200  to the desired location in the patient. 
     Coaxially inside tube  230  is tube  240 . Tube  240  is longitudinally movable relative to tube  230 , and may be metal (e.g., stainless steel) hypotube, for example. Screw head  242  is mounted on the distal end of tube  240  and is threaded (as indicated at  244 ) on its distal conical surface. Tube  240  is rotatable (about the central longitudinal axis of instrument  200 , either alone or with other elements) in order rotate head  242  and thereby use threads  244  in engagement with the tissue of the aorta wall to help pull head  242  through that wall as will be more fully described below. Because tube  240  is hollow, it can be used for passage of fluid or pressure into or out of the patient. 
     Coaxially inside tube  240  is longitudinal structure  250 . Longitudinal structure  250  is longitudinally movable relative to tube  240 . Structure  250  may also be rotatable (about its longitudinal axis) relative to tube  240  and/or other elements. Structure  250  may be a wire with a distal end portion  252  that is resiliently biased to deflect laterally to one side. Wire portion  252  is kept relatively straight when it is inside tube  240  as shown in FIG. 7 a . But when wire portion  252  is pushed axially out the distal end of tube  240 , it curves to one side as shown in FIG. 7 b . As an alternative or addition to the above-described resilient lateral deflection, the distal portion of structure  250  may be threaded as shown at  254  in FIG. 7 g  to help structure  250  thread its way through the wall of aorta  30 . 
     All of components  210 ,  220 ,  230 ,  240 , and  250  are controlled from outside the patient&#39;s body (i.e., from region  202  in FIG.  5 ). 
     When the distal portion of catheter  210  is at the desired location  34 , proximal balloon  212  is inflated. Even when inflated, proximal balloon  212  is not large enough to block aorta  30 . 
     After proximal balloon  212  has been inflated, wire  250  is pushed distally so that its distal portion emerges from the distal end of tube  240  and penetrates the wall of aorta  30  at location  34 . This anchors the distal portion of instrument  200  to the aorta wall at the desired location. Because of its operation to thus anchor instrument  200 , wire  250  is sometimes referred to as an anchor wire. The rotatability of wire  250 , as well as its resilient lateral deflection (FIG. 7 b ) and/or threads  254  (FIG. 7 g ), may be used to help get the distal end of the wire to the desired location  34  and firmly into the aorta wall at that location in order to achieve the desired anchoring of instrument  200 . 
     When instrument  200  is sufficiently anchored by wire  250 , tubes  230  and  240  are moved in the distal direction relative to wire  250  so that screw head  242  begins to follow wire  250  into and through the aorta wall. During this motion, at least tube  240  is rotated about its longitudinal axis so that threads  244  help to pull head  242  into and through the aorta wall. The distal portion of tube  230  follows head  242  through the aorta wall. If provided, threads  232  and rotation of tube  230  may facilitate transfer of the aorta wall tissue from head  242  to tube  230 . 
     When tube  230  is through the aorta wall, sheath  220  is moved distally relative to tube  230  so that a distal portion of sheath  220  follows tube  230  through the aorta wall. If provided, the distal taper  222  and/or threads  224  and rotation of sheath  220  help the distal portion of sheath  220  through the aorta wall. Then catheter  210  is advanced distally relative to sheath  220  so that a distal portion of catheter  210  follows sheath  220  through the aorta wall. Again, the distal taper  211  of catheter  210  (if provided) helps the distal portion of the catheter through the aorta wall. Inflated proximal balloon  212  prevents more than just the portion of catheter  210  that is distal of balloon  212  from passing through the aorta wall. 
     It should be mentioned that each time another, larger one of elements  240 ,  230 ,  220 , and  210  is pushed through the aorta wall, the previously extended elements can be and preferably are either held stationary or pulled back proximally to prevent them from damaging body tissues outside the aorta. 
     When the distal portion of catheter  210  is through the aorta wall, distal balloon  214 , which is now outside the aorta, is also inflated. The axial spacing between balloons  212  and  214  is preferably small enough so that the aorta wall is clamped between these two balloons as shown in FIG.  8 . For example, if balloons  212  and  214  were inflated without the presence of the aorta wall, their appearance might be as shown in FIG. 8 a . The close spacing of balloons  212  and  214 , as well as their resilient bias toward one another, helps to anchor catheter  210  through the aorta wall and also to seal the aorta wall around the catheter. Balloons  212  and  214  may be inflated by liquid or gas, and they may be specially coated to help improve the seal between catheter  210  and the aorta wall. 
     After the condition of catheter  210  shown in FIG. 8 has been reached, all of components  220 ,  230 ,  240 , and  250  can be withdrawn from the patient by pulling them out of catheter  210  in the proximal direction. 
     The next step in the illustrative procedure being described is to insert an elongated, steerable, endoscopic snare  300  lengthwise into catheter  210 . A simplified cross sectional view of an illustrative steerable endoscopic snare is shown in FIG.  9 . As shown in that FIG., snare  300  includes one or more sheath structures such as  310   a  and  310   b  that are operable by the physician to steer the snare by curvilinearly deflecting it laterally by a desired, variable amount. Within sheaths  310  are such other components as (1) a fiber optic bundle  320  for conveying light from outside the patient to the distal end of snare  300  in order to provide illumination beyond the distal end of the snare, (2) another fiber optic bundle  330  for conveying an image from beyond the distal end of the snare back to optical and/or video equipment outside the patient and usable by the physician to see what is beyond the distal end of the snare, and (3) a snare sheath  340  with the actual snare instrument  350  inside of it. Additional lumens such as  360  may be provided for such purposes as introducing fluid that may help to clear the distal ends of fiber optic bundles  320  and  330 , for introducing fluid for irrigating and/or medicating the patient, for suctioning fluid from the patient, etc. It may not be necessary to provide a separate snare sheath  340 , but rather element  340  may merely be a lumen through the general structure  300  for snare instrument  350 . 
     An illustrative embodiment of the distal portion of snare instrument  350  is shown in FIG.  10 . In this embodiment instrument  350  includes a wire  352  with a snare loop  354  (also of wire) at its distal end. Loop  354  is closed when it is inside snare sheath or lumen  340 . Loop  354  opens resiliently to the shape shown in FIG. 10 when it extends distally beyond the distal end of sheath or lumen  340 . 
     In the alternative embodiment of instrument  350  shown in FIG. 10 a , snare loop  354  is mounted on the distal end of a fiber optic bundle  352 ′. Fiber optic bundle  352 ′ may perform the functions described above for bundle  320  or bundle  330 , thereby integrating those functions into instrument portion  350 . 
     In the further alternative embodiment of instrument  350  shown in FIG. 10 b , snare loop  354  is mounted on the distal end of a tube  352 ″, which can be used to deliver other types of instrumentation to the vicinity of snare loop  354 . For example, tube  352 ″ may be metal (e.g., stainless steel) hypotube, and the other instrumentation delivered via that tube may be a tissue cutter for use in cooperation with snare loop  354  to perform a biopsy. 
     In the still further alternative embodiment shown in FIG. 10 c , snare loop  354  is part of one continuous length of wire  352   a . A possible advantage of the embodiment shown in FIG. 10 c  is that it permits snare loop  354  to be variable in size, determined by how much of wire  352   a  is extended from the distal end of lumen  340 . 
     As shown in FIG. 11, the distal portion of steerable endoscopic snare  300  is extended distally beyond the distal end of catheter  210  and steered by the physician until it is adjacent to the exterior of coronary artery portion  24 . 
     The next step in the illustrative procedure being described is preferably to deploy snare loop  354  by extending it distally from the distal end of structure  300  as shown in FIG.  12 . Alternatively, this step could be performed somewhat later. 
     The next step (also shown in FIG. 12) is to inflate balloon  132  to push tube  120  against the opposite side wall of coronary artery  20  at location  24 . Then stylet wire  150  is moved in the distal direction as shown in FIG. 12 so that its distal tip  152  passes through the wall of the coronary artery. As was mentioned earlier, the distal end of the stylet wire lumen in tube  120  is shaped to help guide stylet wire  150  through the coronary artery wall. After stylet wire  150  is through the coronary artery wall, balloon  132  can be deflated. Balloon  132  may be a perfusion balloon which allows continued blood flow along artery  20  even while the balloon is inflated. 
     It may not be necessary to have a balloon  132  directly opposite the outlet for wire  150 . For example, FIG. 12 a  shows an alternative embodiment in which a perfusion balloon  132 ′ is provided on tube  120  proximally of the outlet for wire  150 . Balloon  132 ′ is inflated when it is desired to stabilize the location of tube  120  in coronary artery  20  (e.g., while the distal portion of wire  150  is being pushed out through the coronary artery wall). Another possibility is for a balloon like  132 ′ to be near the distal end of a balloon catheter from which tube  120  extends distally. Still another possibility may be to omit balloons like  132  and  132 ′ entirely. If a balloon  132  or  132 ′ is provided, it may not be necessary for it to be a perfusion balloon. 
     When the distal portion of stylet wire  150  is outside coronary artery  20 , the next step is to ensure that the distal portion of the wire passes through snare loop  354  as shown in FIG. 12 or FIG. 12 a . This may be facilitated by continued use of the visual observation and steering capabilities of snare  300 . An especially preferred technique is to deploy snare loop  354  so that it is next to coronary artery section  24 . Then when stylet wire  150  emerges from the coronary artery at  24 , it immediately passes through snare loop  354  with no further manipulation being required. 
     Once wire  150  is through snare loop  354 , snare sheath or lumen  340  is moved distally relative to the snare loop. This causes snare loop  354  to close down on wire  150 . Snare sheath or lumen  340  also tends to trap the distal portion of wire  150  and to fold that wire portion back on itself inside sheath or lumen  340  as shown in FIG.  13 . 
     When the condition shown in FIG. 13 is achieved, longitudinal structures  150  and  350  are securely interengaged inside snare sheath or lumen  340 . The next step is to pull wire  352  in the proximal direction all the way out of the patient at location  202  (FIG.  5 ). Because of the interengagement between wires  150  and  352 , withdrawing wire  352  pulls as much additional wire  150  into the patient from external location  102  (FIG.  1 ). When wire  352  has been completely removed from the patient, there is then one continuous wire  150  from outside the patient at  102 , through the patient, to outside the patient at  202 . Wire  150  can now be moved in either longitudinal direction through the patient. This wire or another wire could be used to help pull various apparatus into the patient via the tube or tubes through which the wire passes. 
     After one continuous wire  150  has been established through the patient as described above, steerable endoscopic snare  300  may be withdrawn from the patient by pulling it proximally out of catheter  210 . The condition of the apparatus inside the patient is now as shown in FIG.  14 . Note that the presence of fixed outlets for the wire from the distal portion of tube  120  and the distal end of catheter  210  prevents wire  150  from cutting tissues  20  and  30  when the wire is pulled in either longitudinal direction. The portion of wire  150  extending through the interior of the patient between elements  120  and  210  may have radiologic markers  154  equally spaced along its length. These can be viewed radiologically by the physician to determine the distance between regions  24  and  34  via wire  150 . This helps the physician select the correct length of graft needed between regions  24  and  34 . 
     The next phase of the illustrative procedure being described is to install a new length of tubing between regions  24  and  34 . The new length of tubing may be either an artificial graft, natural body organ tubing harvested from the patient&#39;s body, or a combination of artificial and natural tubing (e.g., natural tubing coaxially inside artificial tubing). In the following discussion it is assumed that the new tubing is to be natural tubing (e.g., a length of the patient&#39;s saphenous vein that has been harvested for this purpose) inside an artificial conduit. When such a combination of natural and artificial conduits is used, both conduits can be delivered and installed simultaneously, or the outer artificial conduit can be delivered and installed first, and then the inner natural conduit can be delivered and installed. The following discussion initially assumes that the latter technique is employed. 
     In accordance with the above-stated assumptions, the next step in the procedure is to use catheter  210  and wire  150  to deliver an artificial conduit so that it extends between regions  24  and  34 . The distal portion of an illustrative assembly  400  for doing this is shown in FIG.  15 . (Several alternative constructions of this portion of the apparatus are shown in later FIGS. and described below.) 
     As shown in FIG. 15 assembly  400  includes a threaded, conical, distal tip  412  mounted on a tubular member  410  (e.g., metal hypotube) through which wire  150  can freely pass. Additional details regarding various possible constructions of tip  412  are provided later with reference to FIGS. 15 a - 15   g , but it should be mentioned here that in this embodiment tip  412  is selectively collapsible to facilitate its withdrawal from the patient after it has served its purpose. Another tubular member  420  is disposed concentrically around tubular member  410 . An inflatable balloon  422  is mounted on the distal end of tubular member  420 . Tubular member  420  includes an axially extending lumen (not shown in FIG. 15) for use in selectively inflating and deflating balloon  422 . Balloon  422  is shown deflated in FIG.  15 . 
     Coaxially around tubular member  420  is an artificial graft conduit  430 . An illustrative embodiment of a suitable conduit  430  is shown in FIG.  16  and includes a tube formed of a frame  432  of a first highly elastic material (such as nitinol) with a covering  434  of a second highly elastic material (e.g., a rubber-like material such as silicone) substantially filling the apertures in the frame. Additional information regarding this possible embodiment of conduit  430  and other artificial graft structures in accordance with the invention is provided in later portions of this specification. Here it will suffice to say that this structure is extremely elastic, flexible, pliable, and resilient. For example, it can be stretched to a small fraction of its original diameter, and it thereafter returns by itself to its original size and shape without damage or permanent deformation of any kind. In addition, this structure is distensible so that it may pulsate very much like natural circulatory system tubing in response to pressure waves in the blood flow. This helps keep the conduit open, especially if it is used by itself as the final graft conduit. At its distal end, extensions of frame  432  are flared out to form resilient hooks or barbs  436 , the purpose of which will become apparent as the description proceeds. Near the proximal end of conduit  430  two axially spaced resilient flaps  438   a  and  438   b  with barbs  439  are provided. The purpose and operation of elements  438  and  439  will also become apparent as the description proceeds. 
     In assembly  400  (see again FIG. 15, and also FIG.  17 ), barbs  436  and flaps  438  are compressed radially inwardly and confined within conduit delivery tube  440 , which coaxially surrounds conduit  430 . Indeed, conduit  430  may be somewhat circumferentially compressed by tube  440 . 
     The portion of assembly  440  at which the proximal end of conduit  430  is located is shown in FIG.  17 . There it will be seen how flaps  438  are confined within conduit delivery tube  440 . FIG. 17 also shows how tubes  410 ,  420 , and  440  extend proximally (to the right as viewed in FIG. 17) from the proximal end of conduit  430  so that the physician can remotely control the distal portion of assembly  400  from outside the patient. 
     To install artificial graft conduit  430  in the patient between regions  24  and  34 , assembly  400  is fed into the patient along wire  150  through catheter  210 . When tip  412  reaches coronary artery portion  24 , tip  412  is threaded into and through the coronary artery wall by rotating tube  410  and therefore tip  412 . (Tube  120  may be pulled back slightly at this time to make sure that it does not obstruct tip  412 .) The passage of tip  412  through the coronary artery wall opens up the aperture in that wall. After tip  412  passes through the artery wall, that wall seals itself against the outside of the distal portion of conduit delivery tube  440  as shown in FIG.  18 . 
     The next step is to push tube  410  and tip  412  distally relative to delivery tube  440 , which is held stationary. Conduit  430  is initially moved distally with components  410  and  412 . This may be done by inflating balloon  422  so that it engages conduit  430 , and then moving tube  420  distally with components  410  and  412 . Distal motion of conduit  430  moves barbs  436  beyond the distal end of delivery tube  440 , thereby allowing the barbs to spring out inside coronary artery  20  as shown in FIG.  19 . This prevents the distal end of conduit  430  from being pulled proximally out of the coronary artery. If balloon  422  was inflated during this phase of the procedure, it may be deflated before beginning the next phase. 
     The next step is to pull delivery tube  440  back slightly so that it is withdrawn from coronary artery  20 . Then tube  420  is moved distally so that balloon  422  is radially inside the annulus of barbs  436 . Balloon  422  is then inflated to ensure that barbs  436  are firmly set in coronary artery  20 . Conditions are now as shown in FIG.  20 . Cross sections of balloon  422  may be L-shaped when inflated (one leg of the L extending parallel to the longitudinal axis of conduit  430 , and the other leg of the L extending radially outward from that longitudinal axis immediately distal of barbs  436 ). This may further help to ensure that barbs  436  fully engage the wall of coronary artery  20 . 
     The next step is to deflate balloon  422 . Then delivery tube  440  is withdrawn proximally until flap  438   a  (but not flap  438   b ) is distal of the distal end of the delivery tube. This allows flap  438   a  to spring radially out as shown in FIG.  21 . Tube  420  is then withdrawn until balloon  422  is just distal of flap  438   a . Then balloon  422  is inflated, producing the condition shown in FIG.  21 . 
     The next steps are (1) to deflate distal balloon  214 , (2) to proximally withdraw catheter  210  a short way, (3) to proximally withdraw tube  420  to press flap  438   a  against the outer surface of the aorta wall, and (4) to proximally withdraw delivery tube  440  by the amount required to allow flap  438   b  to spring out against the interior of catheter  210 , all as shown in FIG.  22 . As a result of the above-described proximal withdrawal of tube  420 , the barbs  439  on flap  438   a  are urged to enter the aorta wall tissue to help maintain engagement between flap  438   a  and the wall of the aorta. Inflated balloon  422  helps to set barbs  439  in the tissue when tube  420  is tugged proximally. 
     The next step is to insert the distal portion of delivery tube  440  into the proximal end of conduit  430  as shown in FIG. 22 a . The distal end of conduit  440  may be inserted all the way to the proximal end of balloon  422  (see FIG. 23 for a depiction of this). A purpose of this step is to subsequently help control the rate at which blood is allowed to begin to flow through conduit  430 . 
     The next step is to proximally withdraw catheter  210  by the amount required to release flap  438   b  to spring out against the interior of the wall of aorta  30  as shown in FIG. 22 b . Catheter  210  may be subsequently pushed back against flap  438   b  as shown in FIG. 23 to help securely engage that flap against the aorta wall. 
     Artificial graft conduit  430  is now fully established between aorta region  34  and coronary artery region  24 . The next steps are therefore to deflate balloon  422  and proximally withdraw tube  420 , to collapse tip  412  and proximally withdraw tube  410 , and to proximally withdraw delivery tube  440 . The proximal end of conduit  430  is now as shown in FIG.  24 . As possible alternatives to what is shown in FIG. 24, the distal end of catheter  210  could be left pressed up against proximal flap  438   b  and/or the distal portion of delivery tube  440  could be left inside the proximal portion of conduit  430 . If the latter possibility is employed, then delivery of the natural graft conduit (described below) can be through tube  440 . 
     Several illustrative embodiments of collapsible tips  412  are shown in FIGS. 15 a - 15   g . In the first embodiment (shown in FIGS. 15 a - 15   c ) a frame of wire struts  412   a  extends radially out and proximally back from the distal end of hypotube  410  (see especially FIG. 15 a ). This frame is covered with a somewhat elastic polymer cover  412   b  (FIG. 15 b ) which is provided with threads as indicated at  412   c . For example, threads  412   c  may be made of one or more spirals of nitinol wire or other metal. When it is desired to collapse tip  412 , another hypotube  410   a  (which is disposed around hypotube  410 ) is shifted distally relative to hypotube  410  to invert and collapse tip  412  as shown in FIG. 15 c.    
     In the alternative embodiment shown in FIGS. 15 d  and  15   e , tip  412  has a central main portion  412   e  attached to hypotube  410 . Around the proximal portion of main portion  412   e  are a plurality of triangular shaped portions  412   f , each of which is connected to main portion  412   e  by a hinge  412   g . The outer surface of the tip is threaded as indicated at  412   h . For example, in this embodiment tip  412  may be made of a plastic polymer material, and hinges  412   g  may be so-called “living” hinges between the various masses of the polymer. As soon as triangular portions  412   f  meet any resistance as tip  412  is withdrawn proximally, they pivot about their hinges  412   g  to the positions shown in FIG. 15 e , thereby greatly reducing the circumferential size of the tip. 
     In the further alternative embodiment shown in FIGS. 15 f  and  15   g , metal struts  412   j  are attached to the distal end of hypotube  410  so that they extend radially out and proximally back. Although not shown in FIGS. 15 f  and  15   g , struts  412   j  are covered with a cover and threads like the cover  412   b  and threads  412   c  shown in FIG. 15 b  and described above. A wire  412   k  connects a proximal portion of each strut  412   j , through an aperture in hypotube  410 , to the distal end of another hypotube  410   b  which is disposed inside hypotube  410 . When wires  412   k  are relaxed as shown in FIG. 15 f , struts  412   j  extend radially out beyond the circumference of delivery tube  440 . When it is desired to collapse tip  412 , hypotube  410   b  is pulled back proximally relative to hypotube  410  as shown in FIG. 15 g . This causes wires  412   k  to pull struts  412   j  in so that the outer circumference of tip  412  is much smaller than the circumference of delivery tube  440 . 
     Again, it should be mentioned that the use of a threaded, collapsible tip  412  as described above is only one of several possibilities. Other alternatives are discussed below after completion of the discussion of the illustrative procedure which is being described and which will now be further considered with reference to FIG.  25  and subsequent FIGS. 
     As has been mentioned, the illustrative procedure being described assumes that natural body conduit (e.g. a length of the patient&#39;s saphenous vein that has been harvested for this purpose) is installed inside artificial conduit  430  after installation of the latter conduit. An illustrative assembly  500  for delivering a length of natural body conduit to installed conduit  430  is shown in FIG.  25 . 
     As shown in FIG. 25, assembly  500  includes a tube  510  disposed around wire  150  so that tube  510  is freely movable in either direction along wire  150 . Tube  510  has an inflatable annular balloon  512   a  near its distal end and another inflatable annular balloon  512   b  spaced in the proximal direction from balloon  512   a . Tube  510  includes separate inflation lumens (not shown) for each of balloons  512  so that the balloons can be separately inflated and deflated. An annular collar structure or ring  520   a  is disposed concentrically around balloon  512   a , and a similar annular collar structure or ring  520   b  is disposed concentrically around balloon  512   b . Balloons  512  may be partly inflated. Each of rings  520  may have radially outwardly extending barbs  522 . A length of natural body conduit  530  (e.g., saphenous vein as mentioned earlier) extends from ring  520   a  to ring  520   b  around the intervening portion of tube  510 . Barbs  522  may extend through the portions of conduit  530  that axially overlap rings  520 . A delivery tube  540  is disposed around conduit  530 . In use, tubes  510  and  540  extend proximally (to the right as viewed in FIG. 25) out of the patient to permit the physician to remotely control the distal portion of assembly  500 . 
     Although not shown in FIG. 25, assembly  500  may include a spring coil (similar to coil  450  in FIG. 36) extending between rings  520  inside of conduit  530  to help hold conduit  530  open and out against delivery tube  540  or subsequently out against conduit  430 . Instead of balloons  512  being both in the same tube  510 , balloon  512   a  may be on a relatively small first tube, while balloon  512   b  is on a larger second tube that concentrically surrounds the proximal portion of the first tube. The first and second tubes are axially movable relative to one another, thereby allowing the distance between balloons  512  to be adjusted for grafts  530  of different lengths. 
     Assembly  500  is employed by placing it on wire  150  leading into catheter  210 . Assembly  500  is then advanced distally along wire  150  through catheter  210  and then into conduit  430  until the distal end of conduit  530  is adjacent the distal end of conduit  430  and the proximal end of conduit  530  is adjacent the proximal end of conduit  430 . The condition of the apparatus at the distal end of assembly  500  is now as shown in FIG.  26 . The condition of the apparatus at the proximal end of conduit  530  is as shown in FIG.  28 . 
     The next step is to proximally withdraw delivery tube  540  so that the distal portion of conduit  530  and distal barbed ring  520   a  are no longer inside the distal portion of delivery tube  540 . Then distal balloon  512   a  is inflated to circumferentially expand ring  520   a  and to set barbs  522  through conduit  530  into the surrounding portion of conduit  430  and coronary artery wall portion  24 . This provides a completed anastomosis of the distal end of conduit  530  to coronary artery  20 . FIG. 27 shows the condition of the apparatus at this stage in the procedure. 
     The next step is to continue to proximally withdraw delivery tube  540  until the proximal end of conduit  530  and proximal ring  520   b  are no longer inside tube  540  (see FIG.  29 ). Then proximal balloon  512   b  is inflated to circumferentially expand ring  520   b  and thereby set barbs  522  through conduit  530  into the surrounding portion of conduit  430  and aorta wall portion  34  (see FIG.  30 ). This provides a completed anastomosis of the proximal end of conduit  530  to aorta  30 . 
     The next step is to deflate balloons  512   a  and  512   b  and proximally withdraw tube  510  and delivery tube  540  from the patient via catheter  210 . Then wire  150  is withdrawn from the patient, either by pulling it proximally from catheter  210  or by pulling it proximally from elements  110  and  120 . Lastly, elements  110 ,  120 , and  210  are all proximally withdrawn from the patient to conclude the procedure. The bypass that is left in the patient is as shown in FIG.  31 . This bypass extends from aorta  30  at location  34  to coronary artery  20  at location  24 . The bypass includes natural body conduit  530  inside artificial graft conduit  430 . One end of the bypass is anchored and anastomosed to coronary artery  20  by barbs  436  and ring  520   a . The other end of the bypass is anchored and anastomosed to aorta  30  by flaps  438  and ring  520   b.    
     The particular uses of the invention that have been described in detail above are only illustrative of many possible uses of the invention. Other examples include same-vessel bypasses in the coronary area and vessel-to-vessel and same-vessel bypasses in other portions of the circulatory system (including neurological areas, renal areas, urological areas, gynecological areas, and peripheral areas generally). A same-vessel bypass is a bypass that extends from one portion of a vessel to another axially spaced portion of the same vessel. In FIG. 32, bypass  620  is a same-vessel bypass around a narrowing  612  in vessel  610 . For ease of comparison to previously described embodiments, the various components of bypass  620  are identified using the same reference numbers that are used for similar elements in FIG.  31 . The invention is also applicable to procedures similar to any of those mentioned above, but for non-circulatory systems such as urological tubing. 
     It has been mentioned that the collapsible tip structures shown, for example, in FIGS. 15-15 g  are illustrative of only one of several possible approaches to providing a structure that can penetrate the wall of coronary artery  20  from outside the artery. Another example of a suitable structure is shown in FIG.  33 . To facilitate comparison to FIG. 15, FIG. 33 uses reference numbers with primes for elements that are generally similar to elements identified by the corresponding unprimed reference numbers in FIG.  15 . 
     In the embodiment shown in FIG. 33 distal tip  412 ′ has external threads  414  for helping to grip and dilate tissue such as the wall of coronary artery  20  as tip  412 ′ is rotated about wire  150  by rotation of proximally extending tubular shaft  410 ′. Threads  414  continue as threads  442  on the exterior of the distal portion of tube  440 ′. Threads  414  also threadedly engage with threads  444  on the interior of the distal portion of tube  440 ′. Thus when both of structures  410 ′ and  440 ′ are rotated together, threads  414  and  442  tend to pull tip  412 ′ and then the distal portion of tube  440 ′ into and through the wall of coronary artery  20 . In the course of this, threads  412 ′ transfer the tissue to threads  442 . Thereafter, structure  410 ′ can be removed from structure  440 ′ by rotating structure  410 ′ in the direction relative to structure  440 ′ that causes threads  414  and  444  to cooperate to shift tip  412 ′ proximally relative to structure  440 ′. When tip  412 ′ has thus shifted proximally beyond threads  444 , elements  410 ′ and  412 ′ can be pulled proximally out of the patient. Tube  440 ′, which remains in place through the coronary artery wall, can thereafter be used as a guide tube for delivery of a graft structure (such as  430  (FIGS.  15 - 17 )) and associated instrumentation (such as structure  420  (e.g., FIGS.  15  and  17 )) to the operative site. 
     Another illustrative alternative embodiment of some of the instrumentation shown in FIG. 15 is shown in FIGS. 34 and 35. Once again, to facilitate comparison to FIG. 15, FIGS. 34 and 35 use reference numbers with primes for elements that are generally similar to elements identified by the corresponding unprimed reference numbers in FIG.  15 . In the embodiment shown in FIGS. 34 and 35 barbs  436 ′ are connected to the distal end of a serpentine ring  439  which is connected in turn to the distal end of frame  432 ′. Barbs  436 ′ are initially held in the form of a distally pointed cone by yieldable bands  437   a ,  437   b ,  437   c , and  437   d . As elsewhere along graft conduit  430 ′, the spaces between barbs  436 ′ are substantially filled by a highly elastic material such as silicone rubber. Bands  437  may be made of a polymeric or other suitable yieldable material. Alternatively, bands  437  could be serpentine metal members that yield by becoming straighter. Bands  437  are initially strong enough to prevent barbs  436 ′ from flaring radially outward from conduit  430 ′ as the barbs are resiliently biased to do. However, bands  437  can be made to yield by inflating balloon  422 ′ (on the distal end of tube  420 ′) inside the annulus of barbs  436 ′. 
     Barbs  436 ′ can be forced through tissue such as the wall of coronary artery  20  in their initial cone shape. Sufficient pushing force can be applied to the cone of barbs  436 ′ in any of several ways. For example, tube  420 ′ may be metal (e.g., stainless steel) hypotube which can transmit pushing force to the cone of barbs  436 ′ by inflating balloon  422 ′ to trap the base of the cone between balloon  422 ′ and tube  440 . Additional pushing force may then also be applied via tube  440  itself. 
     When a sufficient portion of the height of the cone of barbs  436 ′ is through the coronary artery wall, balloon  422 ′ is inflated inside the cone as shown in FIG. 35 to cause bands  437  to yield. This allows barbs  436 ′ to flare radially outward inside the coronary artery, thereby anchoring the distal end of conduit  430 ′ to the artery. Bands  437  may be made progressively weaker in the distal direction to facilitate prompt yielding of distal bands such as  437   a  and  437   b  in response to relatively little inflation of balloon  422 ′, whereas more proximal bands such as  437   c  and  437   d  do not yield until somewhat later in response to greater inflation of balloon  422 ′. This progression of yielding may help ensure that the annulus of barbs flares out in the desired trumpet-bell shape inside the coronary artery. 
     FIGS. 36 and 37 illustrate another possible use of a cone structure like that shown in FIGS. 34 and 35, as well as illustrating other possible aspects of the invention. These FIGS. illustrate a structure that can be used to deliver an artificial graft conduit, or a natural graft conduit, or both an artificial graft conduit and a natural graft conduit simultaneously (e.g., with the natural conduit coaxially inside the artificial conduit). In the particular case shown in FIGS. 36 and 37 it is assumed that only natural graft conduit is being delivered, but it will be readily apparent that artificial graft conduit could be substituted for or added outside the natural graft conduit. 
     In the embodiment shown in FIGS. 36 and 37 the cone of barbs  436 ′ is mounted on the distal end of a highly elastic coil spring  450 . The proximal end of coil  450  is attached to ring  460 . The cone of barbs  436 ? is provided with additional, relatively short, radially outwardly projecting barbs  436 ″ near the proximal base of the cone. As shown in FIG. 37, barbs  436 ″ extend into and/or through the distal portion of a length of graft tubing  530 , which (as has been mentioned) is assumed in this case to be natural body organ tubing such as saphenous vein. Ring  460  is similarly provided with radially outwardly extending barbs  462  which extend into and/or through the proximal portion of graft conduit  530 . Ring  460  also includes resilient radially outwardly extending annular flaps  438   a  and  438   b  with barbs  439 , all similar to correspondingly numbered elements in FIG.  16 . Spring  450 , which is inside conduit  530  between the cone of barbs  436 ′ and ring  460 , helps to support and hold open the graft conduit. Structure  420 ′ (similar to structure  420 ′ in FIGS. 34 and 35 and including balloon  422 ′ as shown in those FIGS.) is disposed around wire  150  inside structures  436 ′,  450 ,  460 , and  530 . Delivery tube  440  is disposed around conduit  530 . 
     The embodiment shown in FIGS. 36 and 37 illustrates a structure which can be used to deliver and install natural body organ conduit without any full length artificial graft conduit being used. In a manner similar to what is shown in FIGS. 34 and 35, the structure shown in FIG. 37 is delivered to the operative site via wire  150 . The cone of barbs  436 ′ is forced through the wall of coronary artery  20  and then flared radially outward inside the coronary artery to anchor the distal end of the graft conduit to that artery. The distal end of delivery tube  440  is pulled back as needed to aid in attachment of the distal end of the graft structure. Attachment of the proximal end of the graft structure to the wall of aorta  30  is performed similarly to what is shown in FIGS. 21-24. Accordingly, with distal flap  438   a  just outside the wall of aorta  30 , delivery tube  440  is pulled back proximally to expose that flap. Flap  438   a  is thereby released to spring out and engage the outer surface of the aorta wall. After that has occurred, proximal flap  438   b  is adjacent the inner surface of the aorta wall. Tube  440  is pulled back proximally even farther to expose flap  438   b  so that it can spring out and engage the inner surface of the aorta wall. Natural body organ graft  530  is now fully installed in the patient. Structures  436 ′,  450 , and  460  remain in place in the patient to help anchor the ends of graft conduit  530  and to help hold open the medial portion of that conduit. 
     In embodiments like FIGS. 36 and 37, coil  450  is optional. If coil  450  is used, its ends may or may not be attached to structures  436  and/or  460 . 
     A coil like coil  450  can be used in other embodiments of the invention. For example, a coil like  450  could be used between rings  520   a  and  520   b  in embodiments like that shown in FIG. 25 to help hold open graft conduit  530  in that embodiment. 
     Still another illustrative alternative embodiment of some of the instrumentation shown in FIG. 15 is shown in FIG.  38 . To facilitate comparison to FIG. 15, FIG. 38 uses reference numbers with double primes for elements that are generally similar to elements identified by the corresponding unprimed reference numbers in FIG.  15 . In the embodiment shown in FIG. 38, the distal end of artificial graft conduit  430 ″ is attached to expandable ring  430   a . Elongated barbs  436 ″ extend distally from the distal end of ring  430   a . The distal ends of barbs  436 ″ are turned back in the proximal direction and extend just far enough into the distal end of tube  420 ″ to be releasably retained by that tube. Barbs  436 ″ are resiliently biased to extend radially outward from ring  430   a , but are initially restrained from doing so by the presence of their distal end portions in the distal end of tube  420 ″. Thus barbs  436 ″ initially form a distally pointing cone that can be pushed through tissue such as the wall of coronary artery  20  in the same manner that has been described above in connection with FIGS. 34-37. Structure  420 ″, which may be metal (e.g., stainless steel) hypotube with an inflatable annular balloon  422 ″ near its distal end, may be used to help push the cone through the tissue. 
     After the distal portion of the cone of barbs  436 ″ has been pushed through the wall of coronary artery  20 , tube  420 ″ is shifted proximally relative to the barbs to release the distal end portions of the barbs. This allows barbs  436 ″ to spring radially outward from ring  430   a  inside coronary artery  20 , thereby anchoring the distal end of the graft conduit in the coronary artery. Ring  430   a  can then be circumferentially expanded to increase the size of the connection between coronary artery  20  and the distal portion of the graft conduit. If desired, each of barbs  436 ″ may be twisted 180° as shown in FIG. 39 before it enters the distal end of tube  420 ″. This promotes turning of the extreme distal end portions of the barbs toward the coronary artery wall when the barbs are released from tube  420 ″. 
     Ring  430   a  and barbs  436 ″ may be made of any suitable material such as any 300-series stainless steel (e.g.,  316 L stainless steel). Another material that may be suitable for barbs  436 ″ is nitinol. As in previously described embodiments, the elastic cover  434  that forms part of conduit  430 ″ preferably extends to regions  430   a  and  436 ″. 
     A preferred artificial graft (such as conduit  430  in FIG. 16) in accordance with this invention includes an open frame structure (such as  432  in FIG.  16 ). This frame structure may have any desired shape such as a tube, a flat or contoured sheet, etc. The frame structure may be formed in any suitable way such as by cutting apertures in an initially imperforate structure; forming a mesh of strands of frame material; braiding, knitting, weaving, or felting together strands of frame material; etc. The frame material is preferably an elastic material. Preferred materials are metal, although polymeric materials may also be used. The presently most preferred material is nitinol, and the presently most preferred structure for the frame of a tubular graft is a braid of nitinol wires. 
     The above-described graft frame is preferably covered with a covering of elastic rubber-like material which substantially fills the apertures in the frame as at  434  in FIG.  16 . The covering may be inside the frame structure, outside the frame structure, or both inside and outside the frame structure. Preferred rubber-like materials for the covering are polymeric materials, especially polymeric rubber materials. The presently most preferred rubber-like material is silicone. Examples of other suitable rubber-like materials are stretchable urethane, stretchable PTFE, natural rubber, and the like. For some applications it may be desirable to make the covering porous. Other applications may not benefit from such porosity. Thus the covering can be made either porous or non-porous as desired. 
     The graft structure may include one or more coatings over the above-described covering. In the case of a tubular graft the coating(s) may be inside the tube, outside the tube, or both inside and outside the tube. Possible coating materials include bio-compatible materials and/or drugs. Examples include hydrophylic polymers such as hydrophylic polyurethane (to create a lubricious surface), parylene (a polymer commonly used to coat pacemakers), PTFE (which may be deposited from a PTFE vapor using a process that is sometimes called vapor transport), the drug Heparin (a common anti-coagulant), collagen, human cell seeding, etc. One purpose of such a coating may be to give the coated surface a very high degree of bio-compatibility and/or a very high degree of smoothness. 
     The graft structure may or not include hooks, barbs, flaps, or other similar structures for such purposes as helping to anchor the graft in the body, provide anastomoses between the graft and existing body tubing, etc. Several examples of such structures are shown and described elsewhere in this specification. If provided, such hooks, barbs, flaps, and the like may be extensions of the frame structure or may be molded with or otherwise added to the frame or covering. 
     The most preferred grafts of this invention (e.g., those with a nitinol frame and silicone covering) are highly elastic. The elastic nature of these graft structures allows them to be deployed less invasively (e.g., intravascularly or at least percutaneously). This avoids or reduces the need for surgical implantation. For example, a tubular graft of this construction can be stretched to several times its relaxed length, which greatly reduces its diameter. This facilitates intravascular delivery of the graft. When released from the delivery apparatus, the graft automatically returns to its relaxed length and diameter, with no ill-effects of any kind from its previous deformation. If installed in the circulatory system, the graft is so flexible and elastic that it pulsates in response to pressure waves or pulses in the blood flow. This distensibility of the graft may help prevent blood clots. Coatings that are used on the graft are preferably similarly distensible. 
     In the grafts of this invention that are made with a braided nitinol wire frame and a silicone covering, the preferred wire diameter is in the range from about 0.0005 to about 0.01 inches. An especially preferred wire diameter is about 0.002 inches. The preferred silicone covering thickness is in the range from about 0.00025 to about 0.1 inches. Two covering layers may be used: one inside and one outside the frame structure. If the covering is made porous, the preferred pore size is in the range from about 1 to about 500 microns. An especially preferred pore size is about 30 microns. The preferred covering porosity is in the range from about 50% to about 95%. In other words, from about 50% to about 95% of the volume of the covering is pore space. If any coatings are applied to the graft, they are preferably thinner than the covering. 
     For the preferred grafts of this invention, a preferred manufacturing process in accordance with the invention includes placing or forming the frame structure of the graft on a form (e.g., a rod-like mandrel or tube in the case of the frame for a tubular graft). The form (e.g., mandrel) may be coated with a release agent such as polyvinyl alcohol. The covering is then applied to the frame or the form. The covering is cured, and the frame and covering are removed from the form. Any release agent that remains on the graft is removed. For example, if the release agent is polyvinyl alcohol, it may be removed by boiling the graft in water. If a covering is desired on the inside of the graft, a layer of the covering material may be applied to the form before the frame structure is placed or formed on the form. The form may be provided with a very smooth surface to give the finished graft a correspondingly smooth surface. For example, a very smooth mandrel may be used to give the inside of a tubular graft a very smooth surface. 
     If one or more coatings are desired on the graft, the coating may be done at any suitable time. For example, the coating may be done after the graft has been removed from the form. The coating or coatings may be applied using any suitable technique such as dipping, electrostatic spraying, vapor transport, in vitro cell reproduction, etc. 
     A preferred method in accordance with the invention for making the graft covering porous is to mix particles of another material with the covering material before applying the covering material to the frame. The particulate material is selected as one which is stable or at least relatively stable during curing of the covering on the frame, but which can then be removed from the cured covering to leave the covering with the desired porosity. For example, the particulate material may be a salt such as ammonium carbonate, which is relatively stable at temperatures substantially below about 78° C. but which vaporizes relatively rapidly at an elevated temperature (i.e., about 78° C.) that is not harmful to the cured coating material. Any other particulate material that can be removed by vaporization or solution can be used. For example, the particulate material may be removed by dissolving in water or another solvent, by exposure to air or another vaporization medium, by heat, by vacuum, or by any other suitable means. 
     Porosity of the covering is believed to be beneficial for circulatory system grafts. It may promote growth of a cell structure on the inside wall of the graft. And in all uses, porosity may promote better adherence of the above-mentioned coatings to the graft. 
     It will be understood that the foregoing is only illustrative of the principles of the invention, and that various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention. For example, the order of some steps in the procedures that have been described are not critical and can be changed if desired. The manner in which radiologic elements and techniques are used for observation of the apparatus inside the patient may vary. For example, radiologic fluids may be injected into the patient through various lumens in the apparatus to help monitor the location of various apparatus components in the patient, and/or radiologic markers (of which the above-described markers such as  112 ,  124 , and  154  are examples) may be provided anywhere on the apparatus that may be helpful to the physician.