Abstract:
Method and apparatus for utilizing the vascular system as a conduit to reach other vascular and extravascular locations within the body. Included are methods for revascularization wherein the extravascular passageways are formed to permit blood flow between vascular locations. Also included are methods for performing transvascular interstitial surgery (TVIS) wherein extravascular passageways are formed from a blood vessel to another vascular or non-vascular intracorporeal location. Also disclosed are devices usable for forming extravascular passageways in accordance with the invention, or for modifying, valving, maintaining or closing such passageways.

Description:
RELATED APPLICATIONS 
     This application is a continuation of copending U.S. patent application Ser. No. 10/640,998 filed Aug. 14, 2003 now U.S. Pat. No. 7,407,506 which is a continuation of U.S. patent application Ser. No. 09/181,701 filed Oct. 28, 1998 now issued as U.S. Pat. No. 6,746,464 which is a division of U.S. patent application Ser. No. 08/730,496 filed Oct. 11, 1996 now issued as U.S. Pat. No. 5,830,222 which claims priority to U.S. Provisional Patent Application No. 60/005,164 filed Oct. 13, 1995. 
    
    
     BACKGROUND OF THE INVENTION 
     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 company, 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 is 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 severely 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 chest was closed. In this model, the vein were ‘arterialized’, allowing flow in a retrograde fashion in a 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 been ever been attempted. While in-situ bypass grafts have been made in the 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. 
     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 laparoscopic 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 aid 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 designed for intravascular use. 
     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 a 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 used 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 alternatives 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 opening in an adjacent vessel proximate to the first opening to allow the passage of blood through the channel created by the device. 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. 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 in other tissues, and represents a significant advantage over tissue marking localization, external frames or so-called “frameless” external instrument orientation systems. In a final 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic showing of a human heart wherein a blood flow channel has been formed between a coronary artery and a coronary vein in accordance with one embodiment of the present invention. 
         FIG. 2  is a sectional view through two adjacent blood vessel with a tissue penetrating catheter device of the present invention positioned in one of the blood vessels and being used to form a penetration into the adjacent blood vessel. 
         FIG. 3  is a sectional view through an obstructed artery and an adjacent vein, wherein a blood flow channel has been formed between the artery and the vein and an embolization device has been positioned in the vein, proximal to the blood flow channel, to cause arterial blood to flow through the blood flow channel, into the lumen of the vein, and through the lumen of the vein in a directional opposite normal venous flow. 
         FIG. 4  is a sectional view through an obstructed artery and an adjacent vein, wherein a blood flow channel has been formed between the artery and the vein and a connector apparatus, which may optionally be covered, has been placed within the blood flow channel and protrudes into the lumens of the artery and vein. 
         FIG. 4   a  is a sectional view through an obstructed artery and an adjacent vein, wherein a blood flow channel has been formed between the artery and the vein and a connector apparatus, which may optionally be covered, has been placed within the blood flow channel only. 
         FIG. 5  is a sectional view through an obstructed artery and an adjacent vein, wherein a penetration tract has been formed between the artery and the vein and a dilation apparatus has been introduced into the penetration tract to enlarge the penetration tract to form a blood flow channel. 
         FIG. 6  is a sectional view through an obstructed artery and an adjacent vein, wherein a penetration tract has been formed between the artery and the vein and an energy-emitting channel sizing device has been introduced into the penetration tract to enlarge the penetration tract to form a blood flow channel. 
         FIG. 7  is a sectional view through an obstructed artery and an adjacent vein, wherein a penetration tract or blood flow channel has been formed between the artery and the vein and a polymer stent has been positioned within the penetration tract of blood flow channel. 
         FIG. 8  is a sectional view through an obstructed artery and an adjacent vein, wherein a blood flow passageway has been formed between the artery and the vein and a welding catheter system has been inserted through the blood flow passageway and is being used to cause local tissue fusion in accordance with one embodiment of the present invention. 
         FIGS. 9   a - 9   c  are a step-by-step showing of the placement of connector apparatus between openings formed in adjacent blood vessels, in accordance with one embodiment of the present invention. 
         FIG. 10   a  is a partial side elevational view of a catheter and guidewire wherein a collagen sponge type embolization device is positioned within and deployable from the catheter to embolize the lumen of a blood vessel in accordance with one aspect of the present invention. 
         FIG. 10   b  is a showing of the catheter device and guidewire of  FIG. 10   a , wherein the collagen sponge type embolization device has been partially advanced out of the distal end of the catheter in an over-the-wire fashion. 
         FIG. 11   a  is a perspective view of an embodiment of a one-way valve stent of the present invention. 
         FIG. 11   b  is a side elevational view of the one-way valve stent of  FIG. 11   b.    
         FIG. 12  is a sectional view through an obstructed artery and an adjacent vessel, wherein a percutaneous in-situ bypass procedure has been performed to bypass the obstruction in the artery. 
         FIG. 13  is a broken, sectional view of a blood vessel being used in the performance of transvascular interstitial surgery TVIS procedure in accordance with one aspect of the present invention. 
         FIG. 14  is a partial sectional view of a blood vessel having a deflectable-tipped penetration catheter device of the present invention being used to puncture outwardly through the wall of the blood vessel. 
         FIG. 15  is a partial perspective view of another deflectable-tipped penetration catheter device of the present invention incorporating an optional active imaging apparatus and an optional flush channel. 
         FIG. 16  is a sectional view through two adjacent blood vessels, wherein penetration tract has been formed between the blood vessels and pull back channel sizing device has been advanced through the penetration tract and is being used to enlarge the penetration tract to form a blood flow channel. 
         FIG. 17  is a partial sectional view of a blood vessel having a dual balloon penetration catheter device of the present invention position within the lumen of the blood vessel and being used to penetrate outwardly through the wall of the blood vessel. 
         FIG. 18   a  is a partial sectional view of an obstructed artery wherein a catheter device of the present invention has been inserted and is being used to tunnel around the obstruction in accordance with one type of transluminal bypass procedure of the present invention. 
         FIG. 18   b  is a partial sectional view of the obstructed artery of  FIG. 18  after the transluminal bypass procedure has been completed. 
         FIG. 19  is a partial sectional view of a coronary blood vessel wherein one embodiment of a penetration catheter of the present invention has been inserted and is being used to perform a transcoronary transmyocardial revascularization procedure in accordance with the present invention. 
         FIG. 19   a  is a partial view of a coronary blood vessel wherein a deflectable-tipped embodiment of a penetration catheter of the present invention has been inserted and is being used to perform a transcoronary transmyocardial revascularization procedure in accordance with the present invention. 
         FIG. 19   b  is a partial sectional view of a coronary blood vessel wherein one embodiment of a penetration catheter of the present invention has been inserted and is being used to form a series of transmyocardial revascularization channels in accordance with the present invention. 
         FIG. 20  is a partial sectional view of another apparatus of the present invention being deployed and implanted so as to hold together opening formed in the walls of adjacent blood vessels. 
         FIG. 20   a  is a side view of the device of  FIG. 20  after the device has been fully deployed and implanted. 
         FIG. 21  is a view of a welding device. 
         FIGS. 22   a - 22   e  are a step-by-step showing of a method for implanting another connector device of the present to hold together openings formed in the walls of adjacent blood vessels. 
         FIG. 23  is a partial sectional view of a blood vessel wherein a penetration catheter device of this invention is being used to penetrate outwardly through the wall of the blood vessel and a dilator, sheath and guidewire are being advanced through the tissue penetrator. 
         FIG. 24   a  is a longitudinal sectional view of a penetration catheter of the present invention in combination with a locking or anchorable guidewire. 
         FIG. 24   b  is a side view of the locking or anchorable guidewire of  FIG. 24   a.    
         FIG. 25   a  is a partial perspective view of another embodiment of a penetration catheter of the present invention, having a pre-curved configuration. 
         FIG. 25   b  is a perspective view of the pre-curved penetration catheter device of  FIG. 25   a  being constrained to a straight configuration. 
         FIG. 26  is a is a partial sectional view of two blood vessel wherein an energy emitting embodiment of a penetration catheter of the present invention has been inserted and is being used to form a penetration tract or blood flow channel between the blood vessels. 
         FIG. 27  is a partial sectional view of two blood vessels wherein a penetration tract has been formed between the blood vessels and a cutting-type channel sizing device has been advanced through the penetrating tract and is being used to enlarged the penetration tract to create a blood flow channel in accordance with one aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The invention herein utilizes the vascular system as a perfect conduit to any region of the body. The devices, systems and methods described here 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 effect 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-effected 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. 
     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 will be of the type generally known in the art to include a tip of sufficient compliance and size to assure atraumatic 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 surgery (TVIS) guide catheter  5  is inserted through the guide catheter 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 guidewire  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 . Persons of ordinary skill in the art could identify that the passive orientation means  22  may be configured of any of a known set of materials which would allow for the radiographic, fluoroscopic, magnetic or sonographic 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 S 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 piezoelectric, 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 relationship 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 guidewire  202  positioned in this case within the coronary artery  2 —where guidewire  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 . Once the TVIS sheath  26  is placed, a more floppy guidewire can be placed through it to permit the advancement of additional instrumentation in the case where another lumen is to be entered. Alternatively, no guidewire 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 prevent coronary blood from shunting directly back into the right atrium through the coronary sinus, it is necessary to block flow at one or more points within the cardiac vein. Referring to  FIG. 3 , once the hole is made, 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 tissue track  36 . This maneuver ensures that coronary arterial flow  34  passes through tissue track  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 . Those skilled in the art will recognize that 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. 3  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. 10A-10B  and  11 A- 11 B depict two additional schemes of embolization devices in accordance with the invention which also may have utility to accomplish the desired closure. 
       FIG. 10A  depicts a compressed collagen sponge  101  located within an outer sheath  102 , capable of being delivered over guidewire  51 . Once the guidewire  51  is advanced into vessel which is to be embolized, outer sheath  102  is withdrawn over inner core  103  to permit collagen sponge  101  to expand into the vessel as seen in  FIG. 10B . Once completely delivered, the guidewire  51  and the catheter assembly  102  and  103  are withdrawn, leaving the sponge in place. 
       FIG. 11A  depicts a one-way valve 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. 11B , 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 value-like action. 
     In a further embodiment, an embolization device may not be necessary, as shown in  FIG. 4 . A stent  41  is placed through tissue track  36  such that coronary portion  41   a  and venous portion  41   b  are positioned as shown. Stent  41  may be covered by a material, a dense mesh or a matrix of cells, such that coronary flow  34  cannot easily flow through the side wall of stent  41  towards stenosis  201 , but instead is re-routed through stent  41  into cardiac vein  3  to produce retrograde cardiac venous flow  35 . In this figure, the position of the stent suggests that the TVIS guide catheter had been placed within the coronary artery  2 , and the tissue track  36  was created in the arterial to venous direction This would allow for the proper positioning of a guidewire and subsequently the stent to allow for the device to be oriented in the arterial to venous direction. It should be clear that it is also possible for a similar stent to be placed downstream (in a location, for example, corresponding to region  1203  in  FIG. 12  accessed through vein  3 ) from the venous to arterial direction to permit a complete bypass of the stenosis  201  in the coronary artery  2 . Stent  41  must have the capability of being dimensioned such that proximal portion  41   a  and distal portion  41   b  may be expanded into shape which closely approximates the respective wall of the vessel into which it is placed. Alternatively, as shown in  FIG. 4   a , the stent  410  may be placed such that proximal portion  410   a  and distal portion  410   b  do not block flow, but simply act to maintain the dimensions of tissue track  36 . 
       FIG. 5  shows how tissue track  36  can be dilated by a standard balloon  52  advanced over guidewire  51  for the purpose of ensuring that tissue track  36  is wide enough to receive the flow. Further, this step may be necessary to properly dimension the tissue track  36  prior to insertion of other devices such as the stent  41  seen in  FIG. 4 , or stent  410  seen in  FIG. 4   a.    
     A stent may not be necessary to maintain the size of tissue track  36  if enough material can be removed or ablated between coronary artery  2  and cardiac vein  3 . In  FIG. 6 , a vaporization catheter  63  is shown being advanced over guidewire  51 . Here, energy  61  is delivered to the tissue track  36  through the distal portion  62  of the vaporization catheter  63  to create a properly dimensioned correction 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 radiofrequency (RF), microwave, ultrasound, hot-wire, or radiation. 
     Stents such as those shown in  FIGS. 4 and 4   a  may be necessary to control dimensions of the tissue track  36  from expanding under pressure, or closing as a result of restenosis. Another method of maintaining the dimensions of tissue track  36  permanently or temporarily during the healing and remodeling process is shown in  FIG. 7 . Here a polymer stent  71  is shown covering the walls of tissue track  36 . Such a polymer stent  71  may be placed either by insertion and dilation using a balloon catheter, or may created in-situ using various methods known in the art and practiced by a company by the name of FOCAL™ 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. 
     It may be possible that the creation of a tissue track is undesirable, due to the high likelihood that problems such as restenosis or pseudoaneurysm complicate the procedure. This problem may be overcome using methods such as those shown in  FIGS. 8 ,  9 ,  9   a ,  9   b ,  9   c ,  22 ,  22   a  and  23 . 
     In  FIG. 8 , a welding catheter system is used which consists of proximal welding catheter  81  and distal welding catheter  86 . After the tissue track is created through interstitial space  29  between cardiac vein  3  and coronary artery  2 , guidewire  51  is inserted. Distal welding catheter  86  is then advanced over guidewire  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 position, opposing the 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 , 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. 9   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 tissue track  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 tissue track  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. 9   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. 9B , 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. 9B ), 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. 9C , 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. 
       FIG. 22  shows another embodiment for holding together the two openings in both vessels. This embodiment utilized 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 tissue track  36  until it is completely through. In this case, the collapsible retaining unit  2207  helps to dilate the tissue track  36  since the upper clip  2204  is dimensioned to be slightly larger than the diameter of tissue track  36 . A proximal guide catheter  2201  with a lower clip  2202  at its tip are advanced over the distal guide catheter  2201  towards tissue track  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 further welding device in accordance with an embodiment of the present invention is detailed in  FIG. 23 . Here a very similar scheme to that found in  FIG. 8  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 tissue track  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. 12  depicts the final result after the coronary bypass procedure is complete. Normal coronary flow  34  is bypassed around stenosis  201  through tissue track  1202  into cardiac vein  3  and back into coronary artery  2  through tissue track  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. 
       FIG. 13  depicts 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 imagable 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 guidewire, the distal tip of the TVIS access port  1301  is placed percutaneously over the guidewire 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. 14  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. 15  depicts the same TVIS catheter  146  with the additional component of an active imaging device  23  as described previously. Also in  FIG. 15 , 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. 16  depicts another method of creating an accurately sized tissue track  36  in accordance with an embodiment of the present invention. A retrograde tissue cutter catheter assembly  173  is advanced over guidewire  51  through tissue track  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 tissue track  36  until the blade  171  is beyond the opening within artery  2 . Once that position is found, a much larger base catheter  172  is advanced against the proximal opening within vein  3 . The blade  171  and tip  170  are then pulled back against the edges of tissue track  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 tissue track  36  is the size of the outer diameter of the cylindrical blade  171 . 
       FIG. 17  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. 18A and 18B .  FIG. 18A  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  146  creates a tunnel  190  which can be used to allow flow from one point to another point in artery  2  as shown in  FIG. 18B . 
       FIGS. 19 ,  19 A and  19 B depict the use of the device for transmyocardial revascularization in accordance with an embodiment of the present invention.  FIG. 19  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. 19A  depicts how the alternative TVIS guide catheter  146  of  FIG. 18A  may be used to create these elongate channels  2003  within the heart. The TVIS guide catheter  146  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. 19B  depicts TVIS guide catheter  5  creating several channels  2003  transvascularly, permitting blood flow from the vessel directly into the heart. 
       FIG. 22A  depicts a side-to-side fistula stent  2400  in accordance with an embodiment of the present invention. The stent  2400  is fashioned like a clover with the leaves at alternating heights. The two top leaves  2401  and  2403  and the two bottom leaves  2402  and  2404  are placed such that they lie on either side of the vessel edge as shown in  FIG. 22B . Intervening segments  2405  which are perpendicular to the planes of the clovers  2401 - 2404  lie within the channel created by the TVIS devices. The device is deployed from a catheter  2407  over a guidewire  2408  as shown in  FIG. 22C . The stent is wrapped around an inner sheath  2409  such that dover clover leaves  2401  and  2403  are distal and  2402  and  2404  are proximal. As the catheter  2407  is moved relative to sheath  2409 , the two distal clovers  2401  and  2403  are released, the device is withdrawn until the clovers  2401  and  2403  come in contact with inner surface of the distal vessel. Then the catheter  2407  is moved further with respect to the sheath  2409  and the proximal clovers  2402  and  2404  are released onto the inner surface of the proximal vessel as shown in  FIG. 22E . 
       FIG. 23  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, a separate sheath such as the one shown in  FIG. 13  can be advanced.  FIGS. 24A and 24B  show more detail on the components of such a system. Initially, the TVIS catheter is used to place a locking guidewire  2602  into the tissue. The guidewire has a very small locking tie  2604  which serves to anchor it in the tissue during device exchange. Then, over the locking guidewire  2602  the TVIS port introducer assembly shown in  FIG. 24A  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 guidewire  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. 25A and 25B . Here the TVIS catheter  2704  is made with a pre-formed curve seen in  FIG. 25A . When the catheter is constrained as seen in  FIG. 25B  it can be held in a linear position. Guidewire  2701  can be seen exiting the guidewire lumen  2709  when the catheter  2704  is held linearly ( FIG. 25A ) and can exit the side hole  2702  when the catheter is allowed to regain its preformed shape ( FIG. 25B ). 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. 26 . 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 guidewire  2804 , which may be used to block or signal the penetration of the laser energy. 
       FIG. 27  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 guidewire  2903 , the cutting wings  2901  are expanded by moving sheath  2904  relative to central body  2902 . The wings  2901  may be sharp, or the use of additional energy may be used to widen the hole as the device with drawn through the tissue channel.