Abstract:
Devices, systems and methods for transvascular interstitial interventions, including transvascular, catheter based vascular bypass, transmyocardial revascularization, bypass grafting of blood vessels, and interstitial surgical/interventional procedures wherein a catheter is advanced translumenally through the vasculature to a desired location and an operative instrument is passed through the wall of a blood vessel and to a target location (e.g. another blood vessel, an organ, a tumor, another anatomical structure) such that one or more operative devices may be advanced to the target location to perform the desired operative or interventional procedure.

Description:
RELATED APPLICATIONS 
     This patent application is filed with a claim of priority to U.S. Provisional Patent Application Ser. No. 60/010,614 filed on Feb. 2, 1996, the entire disclosure of which is expressly incorporated herein by reference. 
     Also, filed contemporaneously herewith are three (3) separate applications entitled METHODS AND APPARATUS FOR BLOCKING FLOW THROUGH BLOOD VESSELS, METHODS AND APPARATUS FOR ANASTOMOSIS OF ANATOMICAL CONDUITS, and CATHETERS AND RELATED DEVICES FOR FORMING PASSAGEWAYS BETWEEN BLOOD VESSELS OR OTHER ANATOMICAL STRUCTURES, each of which includes subject matter which was initially included in U.S. Provisional Patent Application Ser. No. 60/010,614 and claims priority to that provisional application. 
    
    
     BACKGROUND OF THE INVENTION 
     i. Percutaneous Transvascular Arterial Bypass 
     Atherosclerosis is a progressive disease process in which the flow within the lumen of an artery becomes restricted by a blockage, typically referred to as an atherosclerotic plaque. In the heart, as well as the periphery, a blockage of an artery can result in pain, disfunction and even death. Numerous methods have been employed over the years to revascularize the tissue downstream of an arterial blockage. These methods include bypass grafting using artificial, in-situ venous, or transplanted venous grafts, as well as angioplasty, atherectomy and most recently, laser transmyocardial revascularization. Bypass grafting has been extremely successful; however, the procedure requires extensive surgery. Recently, newer techniques such as the transthoracic endoscopic procedure being pursued by the companies, Heartport, Inc. and Cardiothoracic Systems, Inc., illustrate the need for a less invasive method of bypassing coronary vessels. These procedures are very difficult to perform, and may not be widely applicable. While transmyocardial laser revascularization, a technique in which small holes are drilled through the wall of the heart, looks promising, the method of action is not yet well understood, and problems exist with the use of laser energy to create the channels. Yet clinicians are still very interested in the technique because it has the potential to be minimally invasive, and does not require the patient to be placed on cardiopulmonary bypass. 
     In the 1970s several cardiovascular surgeons experimented with the use of cardiac veins for revascularization. The procedure was for use on patients which had severally diffuse stenotic coronary vessels. The technique involved using an intervening graft from the internal mammary artery or an aortic attachment to a saphenous vein. Instead of sewing the grafts to the distal coronary artery, the grafts were attached to the coronary or cardiac vein in the same location. The proximal portion of the vein was then ligated to prevent a shunt, and the patient was then taken off cardiopulmonary bypass, and the chest was closed. In this model, the veins were “arterialized”, allowing flow in a retrograde fashion in an effort to bring oxygenated blood to the venules and capillaries of the heart. The success of this technique varied greatly, and was for the most part abandoned. Problems included stenosis at the anastomosis, intracardiac hemorrhages from ruptured venules, and thrombosis of the grafts. 
     The devices, systems and methods proposed in this disclosure suggest a new method of percutaneous revascularization. Here, the cardiac veins may either be arterialized, or may be simply used as bypass grafts. There is no literature to suggest that this has ever been attempted. While in-situ bypass grafts have been made in periphery, still an incision is made to attach and ligate the vein ends. Another procedure which bears some resemblance to this technique is called the TIPS procedure transjugular intrahepatic portosystemic shunt. In this procedure a stent is advanced into liver tissue to connect the portal vein to the inferior vena cava. While this procedure can be accomplished percutaneously, it is not for the purpose of revascularization of an organ or to bypass a blockage within a vessel, does not permit retrograde flow within either of the two vessels, is not performed with an accompanying embolization, and requires the use of a stent. Further, the devices and methods used in that setting are too large and do not have the directional capability necessary for use in smaller vessels such as those found in the heart. 
     ii. Transvascular Intervascular Interstitial Surgery 
     Open surgery was for many years the only way to gain access to tissues to perform a surgical maneuver. With the advent of optics, various endoscopic procedures were developed. Initially, these procedures utilized natural orifices such as the urinary tract, oral cavity, nasal canal and anus. Most recently, new techniques using transabdominal and transthoracic ports have been developed. These thorascopic or laporoscopic procedures essentially use instruments which are long shafted versions of their counterparts in open surgery. General anesthesia is usually required, and there are still several smaller wounds which require healing. 
     Another problem that exists with this approach is the identification of anatomically consistent reference points. For precise surgery, such as in the brain, a frame is usually attached to the patients head to provide this reference. More recently, a “frameless” system has been developed which utilizes a much smaller frame mounted with several light emitting diodes (LEDs). The LEDs are correlated to LEDs on the instrument itself using three cameras mounted to the ceiling. This aids in the correlation of the frame to the landmarks, and assures proper positioning of the instrument. While this seems like an extensive effort, it underlines the importance of gaining access to the exact location desired. 
     Traditionally, the vascular system has been entered for the sole purpose of addressing a vascular problem. Angioplasty, atherectomy, stents, laser angioplasty, thrombolysis and even intracardiac biopsy devices have all been designated for intravascular use. 
     iii. Intraluminal Closure 
     To date, there are several available schemes for closing off openings, vessels or tubular structures within the body involved in, for instance, the revascularization process. One method utilizes externally applied apparatuses such as staples, clips, sutures or devices which compress the opening externally and apply energy to weld them shut, for example, the Keppinger Forceps. While these methods are very successful, they all require access to the structure from the outside. However, this may not always be possible during certain catheter based inventions. 
     Another method, compatible with the catheter approach, involves the application of intraluminal devices such as detachable coils, balloons, injectable glues or emboli. These solutions are all limited by the requirement that a foreign object must be used to create a blockage. Moreover, the presences of a foreign object within the body, may at a later time, cause other problems. For example, these devices may become dislodged, or may cause a sever tissue reaction which can be of significant concern. 
     SUMMARY OF THE INVENTION 
     A device, system and method are provided for utilizing the vascular system as a conduit through which an intervention can be rendered within and beyond the vascular wall. In accordance with one embodiment, a device is introduced into the vascular system at a convenient entry point and is advanced to a particular target location at which point an opening is created to allow the passage of the device or another device or devices through or around the port into the space beyond the interior of the vessel. In one embodiment, a system is used to act as an access port to the space through which a procedure may be performed. Such a procedure may be worthwhile for cooling or ablating a volume of tissue, injecting or infusing a drug, substance or material, cutting, manipulating or retrieving tissue, providing access for endoscopic visualization or diagnosis, the placement of an implantable or temporary device, creating an alternative tract through which blood may be conducted for the purpose of revascularization or for performing some other surgical procedure. In another embodiment, the system is used to achieve an extraliminal percutaneous bypass. More particularly, the system is used to simultaneously achieve a second opening in an adjacent vessel proximate to the first opening so that an anastomosis channel may be created between the two vessels or conduits for the passage of blood therethrough. Such a procedure may be useful for creating alternative vascular channels to provide alternative revascularization routes, such as in the heart between the coronary arteries and cardiac veins, or in the periphery between adjacent veins, conduits and/or arteries. In one embodiment of the invention, the vessel with the second opening may be an in-situ vessel, a natural or artificial graft segment, or a transplanted vessel, all of which having been joined to the vessel with the first opening in a side-to-side manner. In other words, the two adjacent vessels, each having a substantially same size opening created by the system, may be maintained in approximation in a relatively parallel manner rather than the conventional end-to-side manner. With further specificity, such a system may be used to bypass coronary arteries and provide for cardiac venous arterialization, or segmental grafting. In addition, the stability of vascular supply orientation to anatomic landmarks provides a simple method of repeatedly accessing perivascular structures under imaging or other guidance. This may be particularly useful for accessing areas within the brain, kidney, lung, liver, spleen as well as in other tissues, and represents a significant advantage over tissue marking localization, external frames or so-called “frameless” external instrument orientation systems. In a further embodiment, the system is used to create an opening in the vessel proximally, tunneling through the tissue adjacent to the vessel, and re-entering the vessel at a distal point. This may be useful for providing an alternate path for blood flow around a lesion with a vessel. A final embodiment of the invention includes a system for closing off an opening such as a lumen of a vessel subsequent to the creation of an alternate revascularization route through which blood may flow around a diseased lesion. The system may use a suction mechanism to first pull the walls of the vessel so that the lumen may be temporarily closed. The system then provides means to securely fix the walls against one another to close off the lumen. 
     In accordance with one particular embodiment of the invention, there are provided methods and devices for transmyocardial revascularization, whereby transmyocardial passageways or bore holes are formed between one or more coronary blood vessels and one or more chambers of the heart, such that blood from the chamber(s) of the heart will flow through the transmyocardial passageways, thereby enhancing the perfusion of that region of the myocardium. In some instances, this may be accomplished by passing a passageway-forming catheter of the present invention through the coronary sinus and into a coronary vein. Thereafter, the passageway-forming catheter is utilized to form a plurality of transmyocardial passageways or bore holes from the coronary vein into a chamber of the left heart, preferably the left ventricle. Thereafter, the passageway-forming catheter is removed and the coronary vein is permitted to remain without occlusion, embolization or ligation, such that oxygenated blood from the left the left ventricle will flow freely through the transmyocardial passageways, through the coronary vein, and back into the coronary sinus. In this manner, a continual and unobstructed flow of arterial blood will be permitted to pass from the left ventricle, through the transmyocardial passageways, thereby providing for enhanced oxygenation and profusion of that region of the myocardium. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an anterior, perspective view of a human heart wherein catheters have been inserted to perform a translumenal coronary revascularization procedure wherein a segment of coronary vein is utilized as a bypass conduit for bypassing an obstruction in a coronary artery. 
     FIG. 1 a  is an enlarged, sectional view of the adjacent coronary artery and coronary vein within segment  1   a  of FIG.  1 . 
     FIG. 2 is an enlarged, partial sectional view through a portion of the heart shown in FIG.  1 . 
     FIG. 3 a  is a perspective view of a passageway-forming catheter apparatus of the present invention having a first embodiment of an orientation marker system formed thereon. 
     FIG. 3 b  is a perspective view of the catheter shown in FIG. 3 a , wherein the catheter has been rotated ninety degrees relative to the showing of FIG. 3 a.    
     FIG. 3 c  is a perspective view of another passageway-forming catheter of the present invention having a second embodiment of an orientation marking scheme formed thereon. 
     FIG. 3 d  is a perspective view of the catheter of FIG. 3 c , wherein the catheter has been rotated ninety degrees relative to the showing of FIG. 3 c.    
     FIG. 3 e  is a cross sectional view through another catheter of the present invention having a third embodiment of an orientation marking system formed thereon. 
     FIG. 3 f  is a partial perspective view of the catheter shown in FIG. 3 e , wherein the catheter has been rotated approximately forty-five degrees relative to the showing of FIG. 3 e.    
     FIG. 4 is a perspective view of a procedure for attaching a bypass graft to a coronary artery, in accordance with the present invention. 
     FIG. 5 is an enlarged view of the distal portion of a passageway-forming probe apparatus utilized to form a passageway and connection between the graft and the coronary artery in the procedure shown in FIG.  4 . 
     FIG. 6 is an enlarged cut away perspective view of segment  6  of FIG.  4 . 
     FIG. 6 a  is an enlarged view of the passageway and connection formed between the graft and the coronary artery in the procedure of FIG.  4 . 
     FIG. 7 is a perspective view of a portion of the human thorax showing a method for performing a minimally invasive in situ bypass procedure to bypass an obstruction in a coronary or peripheral blood vessel. 
     FIG. 8 is a perspective cut away view of an adjacent artery and vein having an introducer and access catheter of the present invention inserted thereinto for use in performing an in situ bypass procedure whereby blood from one of the blood vessels is caused to flow into the lumen of the other blood vessel. 
     FIG. 9 is a cut away perspective showing of the final result of either an in situ bypass or bypass grafting procedure, in accordance with the present invention. 
     FIG. 10 is a longitudinal sectional view of two adjacent blood vessels having a blood flow passageway formed therebetween in accordance with the present invention, and a lumen blocking apparatus disposed within the lumen of the bypass vessel to facilitate the flow of shunted blood in the desired direction through the bypass vessel. 
     FIG. 11 a  is a longitudinal sectional showing of a delivery catheter having a self expanding embolization device in the nature of a gel foam sponge positioned within the lumen of the catheter, and advanced over a prepositioned guide wire. 
     FIG. 11 b  shows the catheter of FIG. 11 a  wherein the self expanding embolization device in the nature of a gel foam sponge is being advanced out of the distal end of the catheter and over the guide wire. 
     FIG. 12 a  is a perspective view of a one way valved stent apparatus which is usable to facilitate one way flow through the passageways formed between blood vessels or other anatomical structures, in accordance with the methods of the present invention. 
     FIG. 12 b  is a side view of the apparatus of FIG. 12 a.    
     FIG. 13 is a longitudinal sectional view of adjacent blood vessels having a blood flow passageway or anastomosis channel formed therebetween in accordance with the present invention, and having a protrusive stent disposed within the passageway or channel and extending into the lumens of the blood vessels, such protrusive stent being optionally formed, wholly or in part, of a relatively dense material which will block the natural flow of blood through the lumen of at least one of the blood vessels. 
     FIG. 14 is a longitudinal perspective view of adjacent blood vessels having a blood flow passageway (i.e., an anastomosis channel) formed therebetween and having a non-protrusive stent mounted within the blood flow passageway (i.e., an anastomosis channel) to maintain the dimensions of the blood flow passageway (i.e., an anastomosis channel). 
     FIG. 15 is a longitudinal sectional view of adjacent blood vessels having a blood flow passageway or an anastomosis channel formed therebetween in accordance with the present invention, such blood flow passageway or anastomosis channel being dilated by a balloon which has been advanced over a guide wire for the purpose of dilating the passageway or an anastomosis channel. 
     FIG. 16 is a longitudinal sectional showing of two adjacent blood vessels having an initial puncture tract or channel formed therebetween in accordance with the present invention, and further showing an energy emitting vaporization catheter being advanced over a guide wire which has been passed through the initially created puncture tract or channel, such vaporizing catheter being operable to form a finished blood passageway or an anastomosis channel having the desired dimensions. 
     FIG. 17 is a longitudinal sectional showing of an adjacent blood vessels having a blood flow passageway or anastomosis channel formed therebetween in accordance with the present invention, and wherein a welding catheter system of the present invention is used to weld or fuse the tissue which surrounds the blood flow passageway or anastomosis channel, thereby establishing a firm connection between the openings formed in the adjacently situated blood vessels. 
     FIG. 18 is a longitudinal sectional view of adjacent blood vessels having a blood flow passageway or an anastomosis channel formed therebetween in accordance with the present invention, and having a polymer stent covering the walls of the passageway or an anastomosis channel. 
     FIG. 19 is a longitudinal sectional showing of adjacent blood vessels having a blood flow passageway or anastomosis channel formed therebetween, and having a stapling catheter of the present invention positioned within such passageway or channel to install staples to connect the blood vessels and hold the passageway or channel in the desired alignment. 
     FIGS. 19 a - 19   c  show, in step-wise fashion, the manner in which the stapling catheter of FIG. 19 is utilized to install the staples within the blood flow passageway or anastomosis channel. 
     FIG. 20 is a longitudinal sectional view to adjacent blood vessels having a blood flow passageway or anastomosis channel formed therebetween, and having a clip-installing catheter device of the present invention passed through the passageway or anastomosis channel to install a clip therewithin. 
     FIG. 20 a  is a longitudinal section view of the blood vessels shown in FIG. 20, having a clip of the present invention installed within the blood flow passageway or anastomosis channel formed between the blood vessels. 
     FIG. 21 is a longitudinal sectional showing of adjacent blood vessels having a blood flow passageway or anastomosis channel of the present invention formed therebetween, and an alternative embodiment of a welding catheter device passed through such passageway or channel to fuse or weld or tissue surrounding the channel. 
     FIG. 22 is a longitudinal sectional showing of an adjacent coronary artery and coronary vein, wherein an in-situ coronary bypass procedure of the present invention has been completed. 
     FIG. 23 a  is a longitudinal sectional view of a blood vessel wherein a TVIS access port of the present invention has been percutaneously inserted. 
     FIG. 23 b  is a longitudinal sectional showing of a blood vessel having another embodiment of a TVIS access port of the present invention, which includes an optional balloon, inserted thereinto. 
     FIG. 24 is a longitudinal sectional showing of a blood vessel having a TVIS guide catheter of the present invention positioned therewithin, and a TVIS device (i.e., passageway forming catheter) advanced through such guide catheter. 
     FIG. 25 is a perspective view of another embodiment of a TVIS catheter of the present invention, having an active imaging component formed or mounted thereon. 
     FIG. 26 is a longitudinal section showing of adjacent blood vessels having an initial puncture tract formed therebetween and a catheter borne retrograde tissue cutting assembly of the present invention positioned therewithin to enlarge the initial puncture tract to form the desired anastomosis channel or blood flow passageway. 
     FIG. 27 is a longitudinal sectional showing of a blood vessel having another embodiment of a TVIS guide catheter incorporating proximal and distal isolation balloons. 
     FIG. 28 a  is a longitudinal sectional showing of an obstructed artery and an adjacent area of tissue, with a TVIS guide catheter and TVIS device of the present invention being advanced through the adjacent tissue to form an interstitial tunnel or blood flow passageway around the obstruction. 
     FIG. 28 b  is a longitudinal sectional showing of the blood vessel of FIG. 28 a , following formation of the interstitial tunnel around the obstruction. 
     FIG. 29 a  is a sectional showing of a coronary blood vessel and an adjacent segment of myocardium, wherein a TVIS catheter or probe of the present invention have been advanced into the coronary blood vessel and is being used to form an interstitial channel in the myocardium to enhance perfusion of that region of the myocardium. 
     FIG. 29 b  is a sectional showing of a coronary blood vessel and an adjacent segment of myocardium, wherein an alternative TVIS catheter or probe of the present invention have been advanced into the coronary blood vessel and is being used to form an interstitial channel in the myocardium to enhance perfusion of that region of the myocardium. 
     FIG. 29 c  is a sectional showing of a bifurcated coronary blood vessel wherein a TVIS catheter of the present invention has been positioned, such TVIS catheter being utilized to form a series of interstitial channels to enhance perfusion of that region of the myocardium. 
     FIG. 29 d  is sectional showing of a coronary vein and an adjacent segment of myocardium which forms a wall of the left ventricle of the heart, and a series of transmyocardial blood flow passageways having been formed between the coronary vein and the left ventricle in accordance with the present invention, and the coronary vein remaining unobstructed and unlighted such that oxygenated blood may flow from the left ventricle, through the transmyocardial channels, through the coronary vein and into the coronary sinus thereby providing for continual enhanced perfusion of that region of the myocardium. 
     FIG. 29 d ′ is a longitudinal sectional view through the coronary vein shown in FIG. 29 d.    
     FIG. 30 is a longitudinal section showing of a blood vessel having a TVIS catheter and ancillary devices positioned therewith in accordance with the present invention. 
     FIG. 31 a  is a longitudinal sectional view of a portion of TVIS catheter of the present invention having a locking guide wire passed therethrough. 
     FIG. 31 b  is a perspective showing of the locking guide wire apparatus shown in FIG. 31 a.    
     FIG. 32 a  is a perspective showing of a portion of a TVIS catheter of the present invention having a deflectable or curvable distal portion. 
     FIG. 32 b  is a plan view of the TVIS catheter of FIG. 32 a  in a non-curved, straight configuration. 
     FIG. 33 a  is a longitudinal perspective showing of adjacent blood vessels wherein an alternative TVIS catheter device of the present invention is being utilized to form a passageway or anastomosis channel between the blood vessels by emission of a vaporizing energy beam. 
     FIG. 33 b  is a longitudinal perspective showing of adjacent blood vessels having an initial puncture tract or passageway formed therebetween, and a device of the present invention passed therethrough for widening or enlargement of the initial puncture tract or channel. 
     FIG. 34 a  is a longitudinal sectional view of the distal tip of a TVIS catheter device of the present invention having a tissue-penetrating probe formed of shaped memory material retracted thereinto. 
     FIG. 34 b  is a longitudinal sectional showing of adjacent blood vessels having the TVIS catheter of FIG. 34 a  advanced thereto, and showing the shaped memory tissue-penetrating probe being advanced out of the distal end of the catheter to form an initial puncture tract or passageway between the blood vessels. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The invention herein utilizes the vascular system as a perfect conduit to any region of the body. The devices, system s and methods described herein provide a new way that the interstitial space can be accessed for surgical purposes. The invention described herein provides a system for gaining percutaneous access to any part of the body through the vascular system, and provides the basic set of instrumentation for accomplishing several surgical and medical end points. 
     The present invention provides a percutaneous means for revascularizing an organ fed by a diseased vessel. In accordance with further embodiments of the present invention, a complete multiple coronary artery bypass may be accomplished without cracking open the chest, general anesthesia or cardiopulmonary bypass. 
     In order to provide an overall understanding of the present invention, the method of the invention will be discussed with reference to the device&#39;s use to bypass a lesion within the coronary artery in the heart percutaneously. However, it will be understood by persons of ordinary skill in the art that the general method, system and device as described herein are equally applicable to the surgical manipulation of any perivascular structures. This invention represents a new concept in minimally invasive surgery which is that the vascular system may be used purely as a conduit to a desired surgical point. Under the proper guidance, at that surgical point, the perivascular space can be penetrated by a device so as to allow for the insertion of various instrumentation to create a surgical effect. Some examples of these procedures may include but are not limited to: transvascular intracranial access and subsequent therapeutic or diagnostic intervention to various perivascular tumors, hemorrhages, stroke affected areas and diseased zones; transvascular tissue biopsies from the brain, heart, kidney, liver, lung or bone; transvascular implantation of drugs, materials or devices such as sensors, radioactive seeds, ferromagnetic particles, balloons, cells or genetic material, and transvascular bypass. 
     Referring to FIG. 1, a typical coronary sinus guide catheter  4  is shown having been advanced up the vena cava  7  and into the heart  1 . Although not shown, the guide catheter  4  has been advanced into the coronary sinus within the right atrium of the heart  1 . This guide catheter  4  will be of the type generally known in the art to include a tip of sufficient compliance and size to assure a traumatic insertion into the coronary sinus, with a balloon at its distal end to permit the retrograde injection of contrast to permit imaging of the cardiac venous system. The transvascular interstitial (TVIS) guide catheter  5  is inserted through the guide catheter  4  and advanced through one cardiac vein  3  over a guide wire  28  to a desired point adjacent to a coronary artery  2 . The figure shows a TVIS probe  27  being advanced through the TVIS guide catheter  5  through an opening in the cardiac vein  3  to a desired point in the coronary artery  2 . 
     FIG. 2 shows, in more detail, the various functions and components which could be included on the TVIS guide catheter  5 . Here the TVIS guide catheter  5  is shown within a cardiac vein  3  being advanced over guide wire  28 . A balloon  21  is provided on TVIS guide catheter  5  for the purpose of blocking flow, stabilizing the catheter within the lumen, or dilating the passageway. TVIS guide catheter  5  is also provided with either or both active orientation detection means  23  and passive orientation detection means  22 . The passive orientation means  22  may be configured of any of a known set of materials which would allow for the radiographic, fluoroscopic, magnetic, sonographic or electromagnetic detection of the position and orientation of the distal portion of the TVIS guide catheter  5  within the body. These materials include but are not limited to any radiopaque material such as barium or steel, any ferromagnetic material such as those with iron, or any material or composite which provides sufficient interference to sound waves such as trapped air bubbles, scored metal or several laminates. The active orientation detection means  23  permits the proper 360 degree orientation of the distal portion on the TVIS guide catheter  5  within the lumen of the vessel, in this case cardiac vein  3 . This active orientation means  23  can utilize any one but is not limited to one of the following technological schemes: the active orientation means  23  may be a simple piezo-electric, wire or silicon based slab capable of sending and receiving a signal to detect the presence or velocity of flow within an adjacent vessel; this same device could be an array of receivers in relation to a transmitter for the purposes of providing an image of the surrounding tissue; this same device could also be a simple transmitter capable of sending a signal to guide wire  202  positioned in this case within the coronary artery  2  where guide wire  202  is further modified to include a small receiver/transmitter  203  and wire bundle  204  capable of returning a signal to the operator upon detection of the signal emitted by active orientation means  23 ; the reverse system is also applicable where the small receiver/transmitter  203  sends a signal to active orientation means  23 ; the same could also be said for orientation means  23  to send or receive signals to or from any of a series of known signal generators including sonic, electromagnetic, light or radiation signals. The TVIS guide catheter  5  is provided in this case with an additional opening to allow for the selective injection of contrast or fluid into the vessel, in this case cardiac vein  3 . Once the orientation of the TVIS guide catheter  5  is assured, the TVIS probe  27  and TVIS sheath  26  may be advanced through the wall of the cardiac vein  3  into the interstitial space  29  and into the coronary artery  2 . The TVIS probe  27  and TVIS sheath  26  do not necessarily need to be advanced simultaneously and may have the following configurations: the TVIS sheath  26  may be a sharp tipped or semi rigid cannula capable of being inserted into the tissue alone; the TVIS probe  27  may be a relatively rigid wire, antenna, light guide or energy guide capable of being inserted into the tissue alone with the support of TVIS sheath  26 ; or further the TVIS probe  27  and TVIS sheath  26  may be operatively linked where the two are inserted together into the tissue. The TVIS probe  27  and/or the TVIS sheath  26  provide the initial connection between the two vessels, the cardiac vein  3  and coronary artery  2 . In one embodiment of the invention, the TVIS sheath  26  may be made from stainless steel, nitinol or a polymer material. Once the TVIS sheath  26  is placed, a more floppy guide wire can be placed through it to permit the advancement of additional instrumentation in the case where another lumen is to be entered. Alternatively, no guide wire may be necessary if the interstitial space is being entered to perform a different type of procedure. This procedure may be used to create a bypass path from coronary artery  2  around a coronary stenosis  201 , into the cardiac vein  3  and in some cases, back into the coronary artery  2 . To further ensure accurate formation of a bypass path across two adjacent vessels, for example, a coronary artery to a cardiac vein, a catheter which has been inserted into one of the two vessels may be provided with a plurality of passive orientation detection means shown in FIG. 2 to correctly orient the direction of a TVIS probe. By way of example, each of the passive orientation detection means  4200  and  4201 , as shown in FIG. 3 a , may be situated on opposite sides of catheter  4202 . In a preferred embodiment, detection means  4200  and  4201  are placed along a diameter across catheter  4202 . In this manner, when the catheter  4202  is rotated about axis Z and the passive orientation detection means  4200  and  4201  subsequently become correspondingly aligned relative to one another, as seen in FIG. 3 b , TVIS probe  4203  may be properly oriented within one vessel (not shown) so as to later forma bypass path across the adjacent vessels. Moreover, the passive orientation detection means  4200  and  4201  are positioned on catheter  4202  in such a manner that when viewed from the perspective of FIG. 3 b  (i.e., when the passive orientation detection means are in corresponding alignment with one another) they are in linear alignment with a distal portion  4204  of TVIS probe  4203  along axis Z. 
     In an alternate embodiment, the passive orientation detection means may be configured with a design as shown in FIGS. 42 c  and  42   d . As illustrated, passive orientation detection means may comprise a substantially circular portion  4205  and a portion  4206  diametrically situated across catheter  4202 . In other words, portion  4206  and the center of circular portion  4205  are situated along one diameter across the catheter  4202 . To properly align the TVIS probe  4203  and its distal portion  4204  within a vessel for bypass path formation across to an adjacent vessel, catheter  4202  is rotated about the Z axis until portion  4206  and circular portion  4205  are concentrically aligned when viewed from the perspective of FIG.  3 D. 
     In a further embodiment, the passive orientation detection means may be provided as shown in FIGS. 3 e  and  3   f  to include a plurality of segments, for instance, segments  4206  and  4207 . When segments  4206  and  4207  are viewed from one end of catheter  4202 , as illustrated in FIG. 3 e , they are substantially parallel along a diameter of catheter  4202 . However, when looking at catheter  4202  from a side view, as seen in FIG. 3 f , segments  4206  and  4207  are not diametrically aligned as seen in FIGS. 3 a  and  3   b . Rather, these segments are offset from one another such that when catheter  4202  is rotated about axis Z to properly orient the TVIS probe (not shown) within the vessel, segments  4206  and  4207 , and the distal portion  4204  of the TVIS probe are essentially aligned in series. 
     Although only three different embodiments for the passive orientation detection means are shown, it should be appreciated that, for instance, other geometrical designs may be provided on the catheter such that when visualization of a particular geometry occurs, it may be said that a proper orientation of the TVIS probe has been achieved. Non-geometrical embodiments may also be provided so long as such an embodiment provides a proper orientation of the TVIS probe to form a bypass path from within one vessel to an adjacent vessel. 
     In accordance with a further embodiment of the present invention, a bypass vessel, as illustrated in FIG. 4, may be attached to a coronary vessel with a stenosis in a side-to-side manner so as to provide an extraliminal percutaneous bypass path around the coronary stenosis. To understand the particular method, the discussion is provided with reference to devices for generally performing an extraliminal percutaneous bypass of a coronary vessel or an arterial vessel in the periphery using a graft segment, an in-situ vessel or a transplanted vessel. 
     FIG. 4 illustrates a procedure using an artificial or biological graft segment to bypass either a coronary vessel or an arterial vessel in the periphery. An artificial or biological graft segment  3101  may be positioned against a vessel  3106  within the body, and in this instance, in the heart  3107 . Graft segment  3101  may be made from an artificial material such as PTFE or Dacron, or a biological material such as mammary artery, saphenous vein or other suitable tubular conduit. As shown in FIG. 4, a probe  3102  may be inserted through an entry point  3105  on graft segment  3101 . Alternatively, probe  3102  may be inserted either within graft segment  3101  through one of its ends, or along side graft segment  3101  through a side branch. Purse stringed sutures  3104  are positioned about entry point  3105  to permit, upon completion of the procedure, rapid closure of the hole created by the entry point  3105 . Probe  3102  is positioned about entry point  3105  to permit, upon completion of the procedure, rapid closure of the hole created by the entry point  3105 . Probe  3102  is positioned within a body wall  3108  through port  3109  and has handle  3110  to permit control and modification of tip  3103 . Handle  3110  may be connected to a range of external devices  3111  such as fluid irrigation/suction, radio frequency (RF) energy, ultrasound imaging hardware, doppler hardware, endoscopic imaging apparatuses, other energy sources such as microwaves or lasers, and mechanical actuation means. The purpose of probe  3102  is to provide mechanical support and, if necessary, to detect the proper location for the graft to be placed. A grasper  3112  is also shown in FIG. 4 assisting in the placement and stabilization of the graft segment  3101 . Once positioned correctly, stay sutures or an attachment agent  3113  such as a surgical adhesive may be used to hold the graft in place against the vessel  3106  during subsequent maneuvers. Although the procedure is discussed in connection with the heart, it should be appreciated that the procedure is equally applicable to arterial vessels in the periphery. 
     FIG. 5 illustrates, in detail, the tip of the probe  3102  shown in FIG.  4 . Here a probe shaft is shown terminating in a probe tip  3201 . In one embodiment of the invention, angle  3208 , at which the tip  3201  is positioned relative to the shaft  3207 , may be variable. Alternatively, the relative angle between the tip  3201  and the shaft  3207  may be fixed. On the tip  3201 , detection means  3202  is positioned in or next to (as shown) access means  3205 . The detection means  3202  provides information about the correct positioning of access means  3205  and may be a doppler imager or detector, ultrasonic imager or detector, or other detection means capable of sensing the presence of the desired vascular structure, for instance, a vessel. In cases where the vessel is clearly visible, such a detection scheme may not be necessary. Nevertheless, access means  3205  may be provided with a number of configurations. The configuration shown in FIG. 5 allows for a flexible sheath  3204  to be introduced over the access means, and for a guide wire  3206  to be introduced percutaneously from within. Alternatively, a sharp wire could be used to access the vessel with a flexible sheath over it, permitting the sharp wire to be subsequently exchanged for a more a traumatic guide wire. FIG. 5 further shows graft  3203  in outline around a probe shaft  3207  and tip  3201 . Graft  3203 , as previously indicated, may be an artificial or biological graft segment (or transplanted vessel from a nearby area). Once the probe within the graft  3203  is properly positioned adjacently to a vessel with a stenosis, access means  3205  is used to puncture simultaneously through both the walls of the graft  3203  and the adjacent vessel similar size openings so as to create a channel therebetween. The presence of such an anastomosis channel is preferable as it permits a guide wire to be introduced between the graft and the vessel so that the sizing of the channel and the attachment of the graft to the vessel may subsequently be carried out across the channel. It should be appreciated that any artificial or biological graft segment (or transplanted vessel from a nearby area) may be positioned over or along side such structures as the femoral or popliteal arteries or veins, the coronary arteries or veins, the aorta, the carotid or iliac arteries, the vena cava, or any other tubular structure within the body to perform the indicated bypass. 
     FIG. 6 shows, in accordance with a preferred embodiment of the invention, a procedure for joining, across an anastomosis channel  3305 , two vessels in a side-to-side manner for bypassing a stenosis. Graft  3300 , which may be an artificial or biological segment, or a transplanted vessel from a nearby area, may be positioned against vessel  3307  using probe  3301 , and the scheme described in FIGS. 4 and 5. Graft  3300  may subsequently be affixed in place with an attachment means, for instance, a surgical adhesive  3309 . The attachment means, for example, stay sutures, energy based welding, glues, or magnetism may be used to hold the two vessels in apposition. Since an artificial or biological segment, or a transplanted vessel from a nearby area is used as a bypass conduit in a side-to-side procedure discussed herein, one or both ends of graft  3300  may be terminated with a clip  3303  to prevent leakage of flow therefrom. Over a guide wire  3306 , an attachment delivery device  3302  is introduced to junction  3308  between the graft  3300  and the vessel  3307  to deploy an attachment member thereat. One type of attachment member useable for this purpose is an anastomosis stent  3304  having a clover shape, a complete description of which is set forth in copending U.S. patent application Ser. No. 08/730,327 filed on Oct. 11, 1996, now U.S. Pat. No. 6,190,353 and claiming priority to earlier filed Provisional Application Ser. No. 60/005,164. Alternatively, other channel connector devices may be used, such as those described in PCT International Patent Application No. PCT/US97/01968 entitled METHODS AND APPARATUS FOR CONNECTING OPENINGS FORMED IN ADJACENT BLOOD VESSELS OR OTHER ANATOMICAL STRUCTURES, which is being filed contemporaneously with this application. 
     As illustrated in FIG. 6 a , the anastomosis stent  3304  or other channel connector device is used to provide an extraliminal connection between the lumen of vessel  3307  and the lumen of graft  3300 . In addition, stent  3304  is used to hold the vessel  3307  and the graft  3300  in close approximation and to maintain the size of the anastomosis channel  3305 . However, it should be appreciated that the attachment member (i.e., anastomosis stent) for maintaining the size of the anastomosis channel may be any number of devices, for instance, a stapler, an internal clipper, a stent, or a welder. 
     FIGS. 7 and 8 illustrate an in situ bypass procedure for a coronary vessel or an arterial vessel in the periphery. In an in situ bypass procedure, vessels  3405  and  3406 , one of which is to be bypassed, naturally lie in close proximity to one another, rather than having been brought into that position. Introducer  3400 , as shown in FIG. 7, is initially inserted through port  3109 , across the body wall  3108 , and into one of the two adjacent vessels  3405  and  3406 . An access catheter  3401  is thereafter introduced through introducer  3400  and manipulated so that its tip  3404  is threaded into a proper position within one of the vessels, for example, vessel  3406 . In one embodiment of the invention, access catheter  3401  includes a hub  3402  having a plurality of access ports  3403  so as to permit the introduction or removal of, for example, various devices, energy delivery means, or fluids and gasses. 
     FIG. 8 illustrates, in further detail, the introducer  3400  and access catheter  3501  within vessel  3502  which is to be bypassed. Access catheter  3501 , similar to catheter  5  of FIG. 2, is shown having an optional balloon  3503 , passive detection means  3504 , active detection means  3505 , sheath  3506  and guide wires  3507  and  3509 . In this diagram, the guide wire  3509  has been substituted for a TVIS access probe  27  shown in FIG.  2 . The in-situ bypass procedure discussed in connection herewith, is substantially similar to the procedure set forth in connection with FIGS. 4 and 5. In particular, the initial access within a vessel is accomplished endoscopically. Moreover, the isolation of an adjacently parallel vessel, and the percutaneous procedures for creating an anastomosis connection, and for attaching the vessels are conducted in very much the same way. The essential difference is that in an in-situ situation, a naturally adjacent vessel is used as a bypass conduit rather than an artificial or biological bypass segment. In addition, with an in situ procedure, the use of the active detection means to locate the bypassing vessel may be much more critical, especially if the endoscopic suite is not equipped with fluoroscopy. 
     FIG. 9 illustrates an end result of a side-to-side procedure for either an in situ bypass or a bypass with a grafting segment. In such a procedure, since endoscopic access is readily available, the need for intraluminal blockage to prevent shunting may not be limited to the use of devices similar to an embolization apparatus (a discussion of which is provided hereinafter). Instead, both ends of vessel  3609  may be closed off using parallel sutures  3607  as shown. The parallel sutures  3607  may also be used to isolate a portion of vessel  3609  within which a hole  3608  exists where the introducer had previously been placed. As previously indicated, the introducer may alternatively be placed directly into the end of the graft  3609 , rather than through side hole  3608 , in the event an artificial or biological graft segment is being used in the bypass procedure. As shown in FIG. 9, by joining a bypass vessel  3609  in a side-to-side manner to vessel  3600  which has a diseased lesion  3604 , a small tissue track, such as anastomosis channels  3602  may be created using, for example, a dilating balloon, dissection and exposure, or endoscopic attachment as described earlier. The creation of anastomosis channel  3602  allows for fluid to flow into the bypassing vessel  3609  from vessel  3600  at a proximal location bypassing the lesion  3604 . If it is desirable, another anastomosis channel  3602  may be created downstream of lesion  3604  so that fluid may flow around the lesion  3604 , and back into vessel  3600  at a distal location. An anastomosis device  3603  may be used to maintain the channel  3602  and to maintain the two vessels in approximation. The vessels may also be maintained in approximation by other attachment means indicated above, or by welding the vessels against one another. 
     To prevent fluid such as coronary blood from shunting directly back through the bypassing vessel after the percutaneous creation of the anastomosis channel for bypassing the stenosis, it may be necessary to block flow at one or more points within the bypassing vessel. With reference now being made to a coronary bypass in FIG. 10, once a hole is made within cardiac vein  3 , and it is determined that it is of sufficient size, an embolization device, such as an embolization balloon  33 , can be used to block flow in the cardiac vein  3  in a region proximal to anastomosis channel  36 . This maneuver ensures that coronary arterial flow  34  passes through anastomosis channel  36  and results in a retrograde cardiac venous flow indicated by arrows  35   a  and  35   b . The embolization balloon  33  is placed using embolization catheter  31  and upon proper inflation, is detached via a detachable segment  32 . Any one of several devices and materials are available for the purpose of embolization. These include detachable balloons, coils, strands of coagulation producing material, microfibrillar collagen, collagen sponge, cellulose gel or sponge such as Gelfoam, or special stents. FIG. 10 shows how these devices can be used to re-arterialize the venous system distal to the connection. However, as shown in FIG. 12, it is possible to simply provide a bypass path by performing the same procedure in reverse in an appropriate downstream location. It should be mentioned that these embolization devices may also be used to block off any unwanted tributaries branching off from the cardiac vein. FIGS. 4 and 9 are described later in this document. 
     FIGS. 11 a - 11   b  and  12   a - 12   b  depict two additional schemes of embolization device in accordance with the invention which also may have utility to accomplish the desired closure. These embolization devices, as well as others, are described in more detail in PCT International Patent Application No. PCT/US97/01463 entitled METHODS AND APPARATUS FOR BLOCKING FLOW THROUGH BLOOD VESSELS, which is being filed contemporaneously with this application. 
     The embolization device shown in FIG. 11 a  is a compressed collagen sponge  101  located within an outer sheath  102 , capable of being delivered over guide wire  51 . Once the guide wire  51  is advanced into vessel which is to embolized, outer sheath  102  is withdrawn over inner core  103  to permit collagen sponge  101  to expand into the vessel as seen in FIG. 11 b . Once completely delivered, the guide wire  51  and the catheter assembly  102  and  103  are withdrawn, leaving the sponge in place. 
     FIGS. 12 a  and  12   b  depict a one way valved stent  112 . Membrane  111 , disposed within the stent  112 , is configured to be cylindrical at side  116 , yet collapsed upon itself at side  113  to form a one way valve. As seen in longitudinal section FIG. 12 b , this allows flow in the direction of arrow  114  and the advancement of devices in this direction, but prevents flow in the direction of arrow  115  as well as preventing devices from entering from that direction. The one way valve stent  112  can be easily placed over a catheter into the desired location and expanded to fit in position. Once the internal delivery catheters are removed, membrane  111  is allowed to collapse, instantly creating a valve like action. 
     It will be appreciated that the use of the collagen sponge  101  as shown in FIGS. 11 a  and  11   b , or flow blocking or partially flow blocking stents  112  as shown in FIGS. 12 a  and  12   b , are not the only means by which the normal flow of blood through the bypass vessel may be blocked. Indeed, certain energy emitting devices and systems useable for intraluminal welding or sealing of the vessel lumen (which were originally shown in FIGS. 37-40 of Provisional Application Ser. No. 60/010,614 to which this application claims priority) as well as other embolizers or lumen blocking apparatus, are now described and claimed in copending application No. PCT/US97/01463 entitled METHODS AND APPARATUS FOR BLOCKING FLOW THROUGH BLOOD VESSELS, which is being filed contemporaneously with this application, also with a claim of priority to Provisional Application Ser. No. 60/010,614. FIG. 15 shows how anastomosis channel  36  formed in any of the procedures described herein, can be dilated by a standard balloon  52  advanced over guide wire  51  for the purpose of ensuring that anastomosis channel  36  is wide enough to receive the flow. Further, this step may be necessary to properly dimension the anastomosis channel  36  prior to insertion of other devices such as the protrusive stent  41  seen in FIG. 13, or the non-protrusive stent  410  seen in FIG. 13 a.    
     In some cases, a stent may not be necessary to maintain the size of anastomosis channel  36  if enough material can be removed or ablated between coronary artery  2  and cardiac vein  3 . In FIG. 16, a vaporization catheter  63  is shown being advanced over guide wire  51 . Here, energy  61  is delivered to the anastomosis channel  36  through the distal portion  62  of the vaporization catheter  63  to create a properly dimensioned connection between artery and vein. Those skilled in the art will recognize that this vaporization catheter  63  may also be used to deliver thermal, cutting, welding or coagulative energy via several means including but not limited to laser, bipolar or monopolar radio frequency (RF), microwave, ultrasound, hot wire, or radiation. This vaporization catheter  63 , as well as other devices useable to enlarge, modify or debulk an initially formed puncture tract or other channel, are fully described and claimed in copending U.S. patent applications Ser. No. 08/730,327 now U.S. Pat. No. 6,190,353 and Ser. No. 08/730,496, now U.S. Pat. No. 5,830,222 which were filed on Oct. 11, 1996. 
     In cases wherein stenting of the channel is necessary or desirable to maintain its desired dimensions, stents such as those shown in FIGS. 13 and 14 may be placed in the anastomosis channel  36  to control its dimensions, e.g. to prevent the channel  36  from expanding under pressure, constricting due to contraction of the surrounding tissue, or closing as a result of restenosis. 
     Another method of maintaining the dimensions of anastomosis channel  36  permanently or temporarily during the healing and remodeling process is shown in FIG.  18 . Here a polymer stent  71  is shown covering the walls of anastomosis channel  36 . Such a polymer stent  71  may be placed either by insertion and dilation using a balloon catheter, or may be created in-situ using various methods known in the art and practiced by a company by the name of FOCAL (TM) located in Massachusetts. Such a polymer stent  71  may permit the temporary protection from the effects of restenosis or pseudoaneurysm formation, and may dissolve after a period of time to reduce the likelihood of any long lasting tissue reaction effects. 
     In some cases, the creation of an anastomosis channel may be undesirable, due to the high likelihood that problems such as restenosis or pseudoaneurysm will occur. However, the potential for such problems may be minimized or overcome by employing channel connecting methods and such as those shown in FIGS. 17,  19 ,  19   a ,  19   b ,  19   c ,  20  and  20   a . These and other channel connection or clipping devices are more fully described and claimed in U.S. patent application Ser. Nos. 08/730,327 and 08/730,496 which were previously filed on Oct. 11, 1996. 
     In FIG. 17, a welding catheter system is used to establish a firm connection between openings formed in adjacently situated vessels. This welding catheter system consists of a proximal welding catheter  81  and a distal welding catheter  86 . After an anastomosis channel has been created through interstitial space  29  which exists between cardiac vein  3  and coronary artery  2 , a guide wire  51  is inserted through the channel. Distal welding catheter  85  is then advanced over guide wire  51  and distal approximation balloon  89  is inflated. Subsequently, proximal welding catheter  81  may be advanced over the distal welding catheter  86 . At that point, proximal approximation balloon  82  may be inflated, and the two balloons may be pulled into a position, opposing edges of the opening in the coronary artery  2  and cardiac vein  3 . The approximation balloons and welding catheters may be equipped with one or more of the following components: intraweld electrodes  83 , contralateral welding surfaces  87  and  88 , and return electrodes  85  and  84  and a thermocouple  801 . In this configuration, bipolar RF energy may be used to weld the two vessel openings together without the need for additional mechanical attachment devices. Energy will be delivered either between the contralateral welding surfaces  87  and  88  or between the intraweld electrodes  83  and the return electrodes  85  and  84 . In either case, the temperature of the local tissue in and around the approximated two openings is elevated to a desired temperature measured by thermocouple  801 . This temperature is maintained for a certain amount of time during which time the tissue is fused. After fusion, the power is turned off, the balloons are deflated, and the apparatus is removed, leaving the two openings fused around their perimeter. 
     In FIG. 19 a mechanical stapling method is described to attach the two vascular openings. Stapling catheter  91  has outer sheath  96 , optional heating coils  94  and  97 , staples  95 , and micromachine staple holders  93 . Stapling catheter  91  is advanced through anastomosis channel  36  until the device is well into the coronary artery  2 . The outer diameter of the outer sheath  96  is sized to slightly dilate the anastomosis channel  36  between the two vessels. Outer sheath  96  is pulled back until the full upper halves of staples  95  are exposed. This point of pull back is controlled at the proximal end of the catheter. The staples  95  are composed of either a spring like material such as stainless steel, or super elastic alloy such that they spring into a curved position as seen in FIG. 19 a . This effect may also be accomplished using shape memory materials such as nitinol and adding heat through coil  97 . Once staples&#39;  95  upper halves have achieved their curved state, the stapling catheter  91  can be withdrawn, as shown in FIG. 18 b , allowing the tips of the staples  95  to seat into the circumference of the opening in the coronary artery  2 . Now the outer sheath  96  can be fully withdrawn (as shown in FIG. 19 b ), permitting the lower halves of the staples  95  to seat into the inner aspect of the circumference around the opening of the cardiac vein. Again this effect can be created either passively upon release of the sheath, or actively using heat from heating coil  94 . While the passive approach is more simplified, the active approach allows for the reversal of the device using an injection of cold saline. This may be desirable in cases where the seating of the staples  95  was not accomplished correctly. Finally, once the staples&#39; placement is assured, they may be released by the micromachine staple holders  93  resulting in the configuration shown in FIG. 18 c , wherein staples  95  cause the tissue  36  to be maintained in an open condition. Those skilled in the art will recognize that other than utilizing micromachines, there may be several methods of staple release, including thermal material methods such as solder melting, thermal degradation of a retaining polymer or biomaterial, as well as mechanical methods such as the removal of a retaining wire, balloon expansion of a weak retaining material, or an unlocking motion of the stapling catheter  91  with respect to the staples  95  that could only be accomplished after the staples have been fixed in place. Devices similar to this stapling catheter  91  and staples  95  are described, claimed, and shown in FIGS. 9 f- 9 f ′″ copending U.S. patent application Ser. No. 08/730,327 filed on Oct. 11, 1996. 
     FIGS. 20-20 a  show another embodiment of an apparatus for holding together the openings formed in adjacent vessels. This embodiment utilizes a distal guide catheter  2205  which is inserted over a guide wire  2206 . An upper clip  2204  is held to the distal guide catheter  2205  by a collapsible retaining unit  2207  located near the upper clip  2204 . This assembly is advanced through anastomosis channel  36  until it is completely through. In this case, the collapsible retaining unit  2207  helps to dilate the anastomosis channel  36  since the upper clip  2204  is dimensioned to be slightly larger than the diameter of anastomosis channel  36 . A proximal guide catheter  2201  with a lower clip  2202  at its tip are advanced over the distal guide catheter  2201  towards anastomosis channel  36 . The two clips  2204  and  2202  are then pulled toward each other until tines  2208  of upper clip  2204  penetrate and lock into the receiving holes  2209  located in the lower clip  2202 . Upon successful locking, the collapsible retaining unit  2207  is collapsed and both proximal and distal catheters are withdrawn leaving the clips behind as seen in FIG. 22 a . The collapsible retaining unit may, for example, be a balloon, struts composed of shape memory material, or wire pins controlled at the proximal end of the catheter. A channel connection apparatus similar to that shown in FIGS. 20-20 a  is fully described claimed and shown in FIGS. 9 a -9 a ′ of copendining application Ser. No. 08/730,327 filed on Oct. 11, 1996, and such device is claimed in that application. 
     Another welding device in accordance with an embodiment of the present invention is detailed in FIG.  21 . Here a very similar scheme to that found in FIG. 17 is employed with the exception that energy is released from a central emitter core  2301  into the opposed openings of vessels  2  and  3 . In this case, after the two openings are opposed, by balloons  89  and  81 , a central emitter core is advanced into the center of the catheter assembly  81  and  86  to a position directly at the midpoint of anastomosis channel  36 . Energy is emitted by this central emitter core to produce enough temperature in the local tissues surrounding the device to permit fusion. This energy and the emitter may be of the form of a 360 degree laterally firing laser fiber, microwave or other electromagnetic antennae, or locally mounted ultrasound producing piezoelectric crystal or laser emitter. Thermocouple  801  may also be helpful to define and control the welding process. 
     FIG. 22 depicts the final result after the coronary bypass procedure is complete. Normal coronary flow  34  is bypassed around stenosis  201  through anastomosis channel  1202  into cardiac vein  3  and back into coronary artery  2  through anastomosis channel  1203 . Here a generic embolization device  1201  is shown blocking the upstream and downstream cardiac vein  3  in addition to a tributary vein  1204 . In the case where simply cardiac venous arterialization is desired, only the proximal embolization and attachment would be required. 
     FIGS. 23 a  and  23   b  depict a generalized TVIS access port  1301 . The TVIS port has a housing  130  and an entry port  138  which permits the introduction of various instruments. The entry port  138  may also have the ability to maintain pressure or hemostasis within the catheter alone or when instruments are inserted through it. Catheter  133  has a proximal portion which forms the housing  130  and a distal portion which forms the tip  1302 . The TVIS access port  1301  may also be provided with an imageable marker  139  and a stabilizing balloon  134  located at its distal portion. After the TVIS guide catheter  5  shown in FIG. 5 obtains interstitial access and leaves behind a guide wire, the distal tip of the TVIS access port  1301  is placed percutaneously over the guide wire and advanced to the interstitial location  138 . Upon identification of the marker  139  outside the vessel  132 , the balloon  134  is inflated. Those skilled in the art should recognize that stabilization means at the tip may also include locking wires, expandable cages, and expandable stent like frames. Once the TVIS access port is fixed in location, numerous other devices may be inserted for effecting a medical or therapeutic intervention. These include endoscopes  135 , surgical tools  136  such as needles, cannula, catheter scissors, graspers, or biopsy devices, and energy delivery devices  137  such as laser fibers, bipolar and monopolar RF wires, microwave antennae, radiation delivery devices, and thermal delivery devices. Once one or more TVIS access ports  1301  are placed, various surgical procedures may be conducted completely through the vascular system on tissues in the periphery. 
     FIG. 24 shows another embodiment of a TVIS guide catheter  146  in accordance with the present invention. Here the TVIS guide catheter  146  is shown having an actively deflectable distal tip  145 . In this case, the distal tip  145  is deflected by a shape memory material  142  embedded in the distal tip  145  of the device. When this material is heated by heating coil  147 , the material rapidly bends into a desired configuration. A working channel  143  is provided for the advancement of the desired TVIS device. Here a needle  141  is shown infusing a drug  140  into the perivascular tissue. As discussed previously, the TVIS guide catheter  146  may also include a balloon  144  for stabilization within the vessel, and a passive imaging marker  148 . 
     FIG. 23 depicts the same TVIS catheter  146  with the additional component of an active imaging device  23  as described previously. Also in FIG. 25, the TVIS probe  27  and TVIS sheath  26  are shown exiting the working channel  143  at the distal tip  145 . Further, a flush channel  150  is also shown. 
     FIG. 26 depicts another method of creating an accurately sized anastomosis channel  36  in accordance with an embodiment of the present invention. A retrograde tissue cutter catheter assembly  173  is advanced over guide wire  51  through anastomosis channel  36 . The retrograde tissue cutter assembly  173  has a cylindrical blade  171  attached to a dilating tip  170 . The tip  170  is advanced through the anastomosis channel  36  until the blade  171  is beyond the opening within the artery  2 . Once that position is found, a much larger base catheter  172  id advanced against the proximal opening within vein  3 . The blade  171  and tip  170  are then pulled back against the edges of anastomosis channel  36 , capturing tissue within the cylindrical blade  171  as it is pressed against the base catheter  172 . After the assembly  173  is removed, the resulting anastomosis channel  36  is the size of the outer diameter of the cylindrical blade  171 . A similar retrograde tissue cutter assembly is described, claimed and shown in FIG. 8 f  of U.S. patent application Ser. No. 08/730,327 filed on Oct. 11, 1996. 
     FIG. 27 depicts a TVIS guide catheter  182  in accordance with an embodiment of the present invention where a distal balloon  181  and a proximal balloon  180  isolate a section of the artery which is to be penetrated. This may be useful when using the TVIS guide catheter  182  in a high pressure vessel such as an artery. Such a catheter  182  may be used in a manner generally similar to the catheter  5  in FIG.  2 . 
     Another alternative method in accordance with an embodiment of the present invention for bypassing a section of a vessel is depicted in FIGS. 28 a  and  28   b.    
     FIG. 28 a  depicts a TVIS guide catheter  146 , such as described in FIGS. 14 and 15, but here having a distal tip  145  with an actively controlled shape memory material  142 . Here the TVIS guide catheter  146  itself is shown tunneling through surrounding tissue utilizing probe  27  and sheath  26  to guide the way. Ultimately, the catheter  145  creates a tunnel  190  which can be used to allow flow from one point to another point in artery  2  as shown in FIG. 28 b.    
     FIGS. 29 a - 29   d  depict the use of a passageway-forming catheter device for transmyocardial revascularizations in accordance with an embodiment of the present invention. FIG. 29 a  shows how the TVIS guide catheter  5  can be placed within the ventricle  2001  of the heart. The TVIS probe  27  is shown here creating an elongate channel  2003  through the heart muscle  2000 . This channel may result in a direct communication between the ventricle and the small capillary vascular bed within the heart muscle  2000 . FIG. 29 b  depicts how the alternative TVIS guide catheter  146  of FIG. 27 a  may be used to create these elongate channels  2003  within the heart. The TVIS guide catheter  145  is further modified in this case with a balloon tip  2002  for the purpose of covering the channel  2003  during vaporization; the balloon  2002  may be additionally assisted in assuring seating against the ventricle wall  2004  by providing a suction through the catheter  146  to an opening at the distal end of balloon  2002 . Finally, FIG. 29 c  depicts TVIS guide catheter  5  creating several channels  2003  transvascularly, permitting blood flow from the vessel directly into the heart. Guide catheter  5  may use RF, electrical or mechanical energy to create a hole. 
     FIGS. 29 d  and  29   d ′ show an alternative transmyocardial revascularization procedure wherein one of the TVIS guide catheters  5 ,  145  and the associated TVIS probe  27  have been advanced into a coronary vein CV and utilized to form a series of transmyocardial channels  2003   a  which extend from the lumen of the coronary vein CV, through the myocardial wall MW into the underlying left ventricle LV of the heart. Following removal of the guide catheter  5  or  146  and probe  27 , the coronary vein CV remains open and unobstructed such that oxygenated blood may flow from the left ventricle LV, through the transmyocardial channels  2003   a , into the lumen of the coronary vein CV, and through the coronary vein CV into the coronary sinus. In this manner, substantially continuous flow of oxygenated blood will be permitted to pass from the left ventricle LV, through the transmyocardial channels  2003   a , and through the coronary vein CV, thereby providing for substantially continual perfusion of the region of myocardium adjacent those channels  2003   a.    
     FIG. 30 depicts more detail of the various types of devices which may be advanced through the TVIS catheter  146  in accordance with an embodiment of the present invention. Here, a wire  2501  is shown having advanced over it a dilator  2502  and a sheath  2503  through the vessel wall  2504 . 
     Alternatively, as shown in FIGS. 31 a  and  31   b , a separate sheath such as the one shown in FIG. 13 can be advanced. Initially, the TVIs catheter is used to place a locking guide wire  2602  into the tissue. The guide wire has a very small locking tie  2604  which serves to anchor it in the tissue during device exchange. Then, over the locking guide wire  2602  the TVIS port introducer assembly shown in FIG. 30 a  is advanced. The assembly includes a dilator  2601  within a catheter  133 . The catheter  133  is provided with a stabilization means  134  illustrated here as a balloon. After the catheter  133  is in place, and the stabilization means  134  is deployed, the dilator  2601  and the locking guide wire  2602  are removed. Depending on the situation, housing  1301  may or may not be equipped with a valve to prevent backflow into the catheter  133 . Subsequently, various instruments may be inserted into the catheter  133  as described previously. 
     Another embodiment of the TVIS catheter in accordance with the present invention can be seen as item  2704  in FIGS. 32 a  and  32   b . Here the TVIs catheter  2704  is made with a pre-formed curve seen in FIG. 31 a . When the catheter is constrained, as seen in FIG. 31 b , it can be held in a linear position. Guide wire  2701  can be seen exiting the guide wire lumen  2709  when the catheter  2704  is held linearly (FIG. 32 b ) and can exit the side hole  2702  when the catheter is allowed to regain its pre-formed shape (FIG. 32 a ). A TVIS probe  2703  is shown entering another channel and exiting the device at the tip in either position. The catheter  2704  can be used in the manner of other catheters discussed previously but has the benefit of being able to cause the tip to be curved in a desired direction. 
     A further embodiment of a TVIS catheter  2800  in accordance with the present invention is shown in FIG. 33 a . Here the two openings in the vessels are made with a vaporizing energy beam  2805  instead of a probe. This method utilizes an energy guide  2801 , which beams energy at a deflecting plate  2802 , which in turn sends the energy laterally into the tissue. The duration and energy level must be finely set to ensure that the opposite wall of vessel  2  is not damaged. Also shown in the diagram is the optional guide wire  2804 , which may be used to block or signal the penetration of the laser energy. 
     FIG. 33 b  depicts another mechanism for widening or cutting the hole in accordance with an embodiment of the present invention. Here the device is advanced through the tissue channel over guide wire  3003 , the cutting wings  3001  are expanded by moving sheath  3004  relative to central body  3002 . The wings  3001  may be sharp, or the use of additional energy may be used to widen the hole as the device with withdrawn through the tissue channel. 
     A further embodiment of a TVIS catheter in accordance with the present invention is illustrated as item  2900  in FIGS. 34 a  and  34   b . As shown therein, catheter  2900  includes a channel  2901  along its longitudinal axis and terminating in single distal opening  2902 . A TVIS probe  2903  is disposed within the channel  2901  in a linear position. In a preferred embodiment, TVIS probe  2903 , rather than the catheter itself (FIGS. 31 a  and  31   b ) is provided with a shape memory ability such that once it is moved from within channel  2901 , TVIS probe  2903  is capable of resuming its pre-formed curve, as shown in FIG. 29 b , to subsequently form, through a vessel, an opening that is less than 180 degrees relative to the longitudinal axis of the catheter  2900 . A guide wire  2904  may also be movably disposed within the probe  2903 . To this end, once probe  2903  has been moved from within channel  2901  through opening  2902  and has resumed its pre-formed shape, guide wire  2904  may be advanced within the probe  2903  to exit across the same opening  2902 . To form a channel  2905 , it is preferably that guide wire  2904  be withdrawn slightly into the probe  2903  so that the probe&#39;s distal portion  2908  is exposed for penetrating through vessel  2906  across to vessel  2907 . Once probe  2903  is within vessel  2907 , guide wire  2904  may be advanced from within the probe  2903  and into the lumen of vessel  2907 . It should be appreciated that although provided with a pre-formed shape probe  2903 , catheter  2900  nevertheless can be used in the manner of other catheters previously discussed.