Abstract:
A branch graft stent system includes a tubular primary graft having a branch graft opening which when deployed is located in alignment with a side branch vessel emanating from the primary vessel in which a branch graft is deployed. A connector (flange) member forms a perimeter of the branch graft opening and is constructed so that the connector member is substantially flush with the wall of the tubular primary graft. The tubular branch graft has a first expandable ring and a second expandable ring spaced apart from each other as part of a connection section located at a proximal end of the tubular branch graft. The first expandable ring, the second expandable ring, and graft or other material spaced between the first expandable ring and the second expandable ring when engaged with the perimeter of the branch graft opening of the primary graft, the assembly forms a flexible sealed connection between the primary graft and branch graft lumens to continue to exclude the aneurysm while providing a conduit for blood flow to the branch vessel. A distal end of the branch graft can be anchored by a balloon expandable or a self-expanding stent to the wall of the branch vessel beyond the aneurysm.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to endoluminal medical devices and procedures, and more particularly to branch vessel grafts secondarily attached to a main vessel stent graft using a system of rings coupled to the branch graft for a sealed branch vessel graft connection to a main stent graft.  
       BACKGROUND OF THE INVENTION  
       [0002]     Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts formed of biocompatible materials (e.g., Dacron or expanded, porous polytetrafluoroethylene (PTFE) tubing) have been employed to replace or bypass damaged or occluded natural blood vessels. A graft material supported by framework is known as a stent graft. In general, the use of stent grafts for treatment or isolation of vascular aneurysms and vessel walls which have been thinned or thickened by disease (endoluminal repair or exclusion) are well known. Many stent grafts, are “self-expanding”, i.e., inserted into the vascular system in a compressed or contracted state, and permitted to expand upon removal of a restraint. Self-expanding stent grafts typically employ a wire or tube configured (e.g. bent or cut) to provide an outward radial force and employ a suitable elastic material such as stainless steel or Nitinol (nickel-titanium). Nitinol may additionally employ shape memory properties. The self-expanding stent graft is typically configured in a tubular shape of a slightly greater diameter than the diameter of the blood vessel in which the stent graft is intended to be used. In general, rather than performing an open surgical procedure which is traumatic and invasive to implant a bypass graft, stents and stent grafts are preferably deployed through a less invasive intraluminal delivery, i.e., cutting through the skin to access a lumen or vasculature or percutaneously via successive dilatation, at a convenient (and less traumatic) entry point, and routing the stent graft through the vascular lumen to the site where the prosthesis is to be deployed.  
         [0003]     Intraluminal deployment is typically effected using a delivery catheter with a coaxial inner (plunger member) and an outer (sheath) tubes arranged for relative axial movement. The stent (or stent graft) is compressed and disposed within the distal end of an outer catheter tube in front of a stent stop fixed to the inner member. The catheter is then maneuvered, typically routed though a lumen (e.g., vessel), until the end of the catheter (and the stent graft) is positioned at the intended treatment site. The stent stop on the inner member is then held stationary while the sheath of the delivery catheter is withdrawn. The inner member prevents the stent graft from being withdrawn with the sheath. As the sheath is withdrawn, the stent graft is released from the confines of the sheath and radially expands so that at least a portion of it is in substantially conforming surface contact with a portion of the surrounding interior of the lumen e.g., blood vessel wall or anatomical conduit. As a convention used to describe the ends of devices implanted in the arterial system the proximal end of the stent graft is the end closest to the heart as taken along the path of blood flow from the heart, whereas the distal end is the end furthest away from the heart once deployed. An example of stent graft positioning and deployment is shown in  FIG. 1 , which is a figure taken from U.S. Pat. No. 5,591,195 to Taheri et al.  
         [0004]      FIG. 1  shows an aneurysm  30  in a vascular artery  32  (such as an aorta). A stent graft  34  spanning the aneurysmal sac  36  is show as just having been deployed from a delivery system  38 . The stent graft  34  is constructed of a tubular graft (textile or cloth) material  40  which at each tubular end is radially expanded by zig zag type (Z-type) tubular stents  42 ,  44 . A connecting bar  46  (shown in dashed lines) connects the two end stents  42 ,  44 . The stent graft  34  deployed at the location of the aneurysm  30  creates a separate isolated flow path for blood through the lumen of the stent graft  34  such that the aneurysmal sac  36  of the aneurysm  30  is excluded and is no longer subject to the normal maximum blood pressure experienced in the vascular arterial system at the location of the aneurysm  30 . Depending on the construction of the graft material  40  it may either seal immediately or provide a very slight permeable leakage (blush) which through the biological activity in the blood stream will cause the graft material  42  to be tightly sealed over time.  
         [0005]     Stent grafts can also be used in patients diagnosed with aneurysms close to or crossing branch openings to renal arteries or other branch arteries (e.g., celiac, suprarenal, interior mesenteric). Stent graft designs with side openings are designed for use in regions of the aorta from which side branches feed blood to organs like the kidney, spleen, liver, and stomach.  FIGS. 2 and 3  show examples from U.S. Pat. No. 6,030,414 to Taheri, as described therein. Such endovascular grafts have been designed for use where the proximal end of the graft is securely anchored in place, and fenestrations are configured and deployed to avoid blocking or restricting blood flow into the renal arteries. The endovascular graft must be designed, implanted, and maintain position in a manner which does not impair the flow of blood into the branch arteries.  
         [0006]     Stent grafts  50 ,  60  with side openings or fenestrations  52 ,  54 ,  62 ,  64  are shown in  FIGS. 2 and 3 . Such fenestrations  52 ,  54 ,  62 ,  64  do not form discrete conduit(s) through which blood is channeled into each branch artery  51 ,  53 ,  61 ,  63 ,  67 ,  69 . As a result, the edges of the graft surrounding the fenestrations  52 ,  54 ,  62 ,  64  could be prone to: i) the leakage of blood into the space between the outer surface  56 ,  66  of the aortic graft (stent graft  50 , 60 ) and the surrounding aortic wall  55 ,  65 ; or ii) post-implantation migration or movement of the stent graft  50 ,  60  causing misalignment of the fenestration(s)  52 ,  54 ,  62 ,  64  and the branch artery(ies)  51 ,  53 ,  61 ,  63 ,  67 ,  69 —with resultant impairment of flow into the branch artery(ies).  
         [0007]      FIG. 4  shows an alternate prior art configuration for a stent graft  70  having integrally constructed tubular branch members  71 ,  72 ,  73 ,  74 , where the branch tubular members are placed into position using a series of guidewires  76 ,  77 ,  78 ,  79 , where the top (proximal) end  80  fixed by a separately delivered stent (not shown) above the aneurysmal part of the aorta. A full explanation of the mechanism for delivery and final fixation of the stent graft with integral branches (as shown in  FIG. 4 ) can be had by reference to U.S. Pat. No. 6,099,548 to Taheri the disclosure of which is incorporated herein by reference.  
         [0008]      FIGS. 5 and 6  show an alternate arrangement for construction of a branch vessel connection.  FIGS. 5 and 6  are examples taken from U.S. Pat. No. 6,059,824 to Taheri, incorporated herein by reference. In  FIG. 5  the main stent body  90  once properly positioned in the main artery (not shown) has an opening wide annular land portion collar  93  aligned with side branching collateral arteries (not shown). The wide annular land portion collar  93  includes a series of inlets (or indentations)  94   a ,  94   b . A collateral cylindrical stent body  92  is mated to the main stent body  90  through an annular land portion flange located at the proximal end of the collateral cylindrical body  92 . The annular land portion collar  95  includes several detents  96   a ,  96   b  which are sized and spaced about the annular extent of the collateral collar  95  to position, hold and lock the collateral stent cylindrical body  92  mated to the main stent body  90 . The detents, e.g.  96   a ,  96   b , are received in the inlets e.g.  94   a ,  94   b , of the main stent collar  93 . An engagement balloon (not shown) located in the aorta is used to provide the force needed to lock the detents, e.g.,  96   a ,  96   b , and the inlets e.g.,  94   a ,  94   b , together.  
         [0009]      FIGS. 7 and 8  show another prior art arrangement of a branch vessel connection to a stent graft. These Figures are similar to those in U.S. Pat. No. 5,984,955 to Wisselink, incorporated herein by reference. Referring now to  FIGS. 7 and 8  together, a primary graft  100  includes a ring member  104  surrounding a side branch orifice  106  having a frustoconical member  102  extending from the graft  100 . A side branch orifice  106  is aligned with the location of a branch artery (as seen in  FIG. 8 ) and then a branch graft  110  is brought in through the main graft and snapped into position as the small ring member  114  and large ring member  116  at the ends of the tapered proximal portion  112  of the branch graft  110  are pushed into interfering engagement with the frustoconical member  102 .  
         [0010]     These examples of prior art devices to facilitate flow from an aneurysmal portion of the aorta into branch vessels show the complexity and space/volume requirements needed in the delivery system to deliver and accurately align such prior art systems. The use of fenestrations or openings in a tubular graft requires that a perimeter opening be sealed against the vascular wall to prevent the blood from passing through the tubular graft from continuing to pressurize and enlarge the surrounding aneurysmal sac. Such a main graft a body can be provided with a flange or other fitting which is hard to compress to insert into a delivery catheter for deployment. And once the main stent graft body is in position then branch members need to be positioned with great care to provide a blood tight seal between the main graft body and the branch graft.  
         [0011]     Thus, a need exists for a method and deployment system simplifies alignment and reduces deployment forces needed to make a fluid tight connection between a main stent graft and a branch graft connected to a sidewall thereof. Ideally, such a branch graft is a part of a graft system that can treat aortic aneurysms at a location close to or at the location a smaller vessel branching from the main vessel using a branch that makes a fluid tight connection to a port of the main graft.  
         [0012]     Progress in this field looks to the development of new endovascular grafting systems and methods which a) may be useable for endovascular grafting in regions of a blood vessel (e.g., aorta) from which branch blood vessels (e.g., carotid, innominate, subclavian, intercostal, superior mesenteric, celiac, renal or iliac arteries) extend, and/or b) may enable more aortic aneurysm patients to be considered as candidates for endovascular repair, and/or c) may otherwise advance the state of the art of endovascular grafting to improve patient outcomes or lessen complications.  
       SUMMARY OF THE INVENTION  
       [0013]     A branch graft design according to the present invention provides an improvement in locating and connecting a stent graft to a branch vessel at the location of an aneurysm in the main vessel. A branch graft design includes a tubular branch graft having a proximal end and a distal end and a lumen extending along the tubular branch graft axis longitudinally therethrough. A first self-expanding support ring is coupled to a first annular ring receiving section encircling the tubular branch graft at its proximal end. A second self-expanding support ring is coupled to a second annular ring receiving section circumferentially encircling the tubular branch graft at its proximal end. The second annular ring receiving section is disposed proximally parallel to and a ring receiving section separation length along the branch graft axis from the first annular ring receiving section such that the second annular receiving section is located closer to the distal end of the graft than the first annular ring receiving section. A tubular main graft constructed of a main graft material has a side opening having a perimeter with a substantially flush reinforcing ring or flange. The ring receiving section separation portion of the branch graft material engages the perimeter of the side opening to form a seal between the main graft and the branch graft when the first self expanding support ring which is coupled to the first annular ring receiving section circumferentially encircling the branch graft at the proximal end is disposed inside the side opening of the main graft and the second self expanding support ring is coupled to the second annular ring receiving section circumferentially encircling the graft at the proximal end of the disposed outside a side opening of the branch graft. The support rings may be made of nitinol and configured in a multiple winding hoop or a stent configuration and the support rings can be sewn to the inside or outside of tubular branch graft. The ring receiving separation portion of the branch graft may be made from the same material as the tubular branch graft or of a semi-rigid (still pliable) material different from the material forming the tubular branch graft.  
         [0014]     An embodiment according to the invention further includes a method for deployment of a main stent graft and branch vessel graft comprising the steps of at least partially deploying the main stent graft and aligning a substantially flush branch vessel port of the main stent graft with a branch vessel: deploying the branch vessel graft into the substantially flush branch vessel port wherein that the branch vessel graft is engaged with the substantially flush branch vessel port of the main stent graft by exposing a first ring integral to the branch vessel graft to a first side of the branch vessel port and subsequentially exposing a second ring integral to the branch vessel graft on an opposing side of the branch vessel port.  
         [0015]     The embodiment according to the invention can be further described to include a branch graft delivery system comprising a branch graft disposed on a delivery catheter having a sheath surrounding a seal portion of the branch graft. The seal portion of the branch graft includes a first annular self expanding ring section and a second annular self expanding ring section. The ring sections are circumferentially coupled to the graft at first and second locations, respectively, wherein the first and second locations are spaced from each by a cylindrical channel seal forming section. An inner member of the delivery catheter includes a first stop and a second stop each of which extend laterally outward from the inner member to a diameter slightly less than the inside diameter of the delivery sheath. Annular space between the inside diameter of the sheath and the outside diameter of the inner member provides clearance for the thickness of the graft material to fit through and be carried in the annular space, while preventing the first and second annular self expanding support ring sections which are thicker because they contain or are attached to the support ring member from passing through the annular space. When the sheath is positioned to surround a first stop the first annular self expanding ring section is prevented from moving towards the second annular self expanding ring section and when the sheath is positioned to surround the second stop a second annular self expanding ring section is prevented from moving towards the first expanding ring section. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0016]      FIG. 1  is a schematic cross sectional view of a tubular stent graft of the prior art disposed across an aneurysm in an arterial vessel;  
         [0017]      FIG. 2  is a schematic cross sectional view of a prior art stent graft having fenestrations which match side branch openings in a main arterial passage having branch vessels extending from the main vessel;  
         [0018]      FIG. 3  is a schematic cross sectional view of a stent graft deployed across an aneurysm in an aorta, where the stent graft has fenestrations positioned at locations so that branch vessels are fed through the fenestrations;  
         [0019]      FIG. 4  is a schematic cross section showing a position of a stent graft with several integral side branch graft passages in the process of being positioned to exclude blood flow to the aortic aneurysm while providing an artificial lumen to feed the branch vessels that originate in the area of the aortic aneurysm;  
         [0020]      FIGS. 5 and 6  show a pre assembly and post assembly, respectively, pictorial diagram of a main stent body to which a cylindrical collateral stent body is attached in situ;  
         [0021]      FIGS. 7A, 7B  and  8  show close up and schematic cross sectional diagrams of a branch graft connection to a primary a stent graft providing branching connections in an aorta where an aneurysmal sac has created a widening of the aorta at a location of branch vessels;  
         [0022]      FIG. 9  is a schematic cross sectional view of a balloon expandable branch graft configuration on its delivery system;  
         [0023]      FIGS. 10 and 10 A are a schematic cross sectional diagram and a close up view of a tip of a self expanding branch graft configuration on its delivery system;  
         [0024]      FIGS. 11 and 11 A are schematic cross sectional diagrams of a set of hoop or ring like self expanding support rings in a compressed configuration;  
         [0025]      FIG. 12  is a schematic cross sectional of the support rings of the  FIG. 11  in an expanded (post deployed) configuration;  
         [0026]      FIGS. 13A and 13B  are side perspective diagrams showing a ring type self expanding support ring in a compressed ( 13 A) and an expanded ( 13 B) configuration as pictured in  FIGS. 11 and 12 , respectively;  
         [0027]      FIG. 14  is schematic cross section showing an alternate configuration of self expanding support rings where the support rings are configured from a stent of a zig zag configuration, the compressed state of the rings is shown;  
         [0028]      FIGS. 15A, 15B ,  15 C,  15 D,  15 E,  15 F, and  15 G are schematic cross sectional diagrams showing the progressive steps of deployment of a branch graft assembly;  
         [0029]      FIGS. 16A, 16B ,  16 C,  16 D,  16 E,  16 F, and  16 G are schematic cross sectional views of the steps in delivery and deployment of a branch graft into a side branch vessel from a aneurysmal sac where a tubular main graft has already been placed. The steps of deployment as pictured in  FIGS. 16A-16G  provide in situ view of the deployment of the branch graft similar to, though not directly correlating to, the steps of branch deployment pictured in  FIGS. 15A-15G  described above.  
         [0030]      FIG. 17  is a side plan view of a main tubular graft having a side branch opening (fenestration) therein;  
         [0031]      FIG. 18  is a schematic cross sectional view showing one configuration of a side branch graft connected with a tubular main graft;  
         [0032]      FIG. 19  is a schematic cross sectional view showing another configuration of a tubular branch graft connected to a tubular main graft; and  
         [0033]      FIG. 20  is a schematic cross sectional view showing another configuration of a tubular branch graft connected to tubular main graft. 
     
    
     DETAILED DESCRIPTION  
       [0034]      FIG. 9  shows a balloon expandable branch graft stent system  120  in accordance with the invention. A catheter having a catheter inner member (inner tube)  122  extends from a proximal end  124  to a distal end  126  of the catheter. A balloon  128  is located at the distal end  126  of the catheter and bonded to the catheter inner member  122  in a balloon to catheter member distal bond region  132 . The proximal end of the balloon  128  is bonded at a balloon to outer member proximal bond region  130  to an outer member  144  that provides a coaxial annular lumen between its inner surface and the outer surface of the catheter inner member  122 . The balloon expandable stent  134  compressed around the balloon  128  is positioned between a stent location proximal marker band  140  and a stent location distal marker band  142  both mounted on the catheter inner member  122 . A tubular graft material  138  is sewn or bonded to the outside of the stent in a stent to graft material bonding section  136 . Tubular graft material  138  extends proximally from the stent  134  to a distal graft ring (hoop-stent) receiving section (pocket)  146  where a self expanding hoop or stent is disposed in a circumferential graft pocket containing a distal coiled nitinol hoop  156 . An outer sheath  160  prevents the distal coiled nitinol hoop  156  from expanding in a radial direction while the axial limits of the distal graft ring receiving pocket  146  limits the axial movement (expansion) of the distal coiled nitinol hoop  156 . Similarly the graft  138  at its proximal end contains a proximal graft ring (hoop-stent) receiving section (pocket)  148  such that the axial length of the tubular graft material  138  extends from the proximal end of the proximal graft ring pocket  148  to the distal end of the stent  134  where it is attached (sewn or bonded) to a graft material  136  in the stent to graft material bonding section  136 . A proximal coiled nitinol hoop  158  is contained within the proximal graft ring hoop receiving section pocket  148 . To maintain the position of the proximal graft pocket  148  with respect to the distal graft pocket  146  and to the distal end of the stent  134  a proximal ring (hoop) stop  152  and a distal ring (hoop) stop  150  are fixed to the outer member (tube)  144  at a distance between ring (hoop) stops  154  spanned by a graft material identified as a ring receiving pockets separation section (sealing section)  153 . The distance between ring hoops stops  154  is dependent upon the main graft wall thickness, the branch vessel diameter, and the main graft wall opening diameter such that the specific dimension described for the distance between hoop ring stops  154  can lengthen or shorten depending on the interaction of the main graft wall thickness the branch vessel diameter and the main graft wall opening and diameter as appropriate for a particular application and branch graft diameter size. The sealing section  153  may be made of graft material or of a more rigid but still pliable material with good surface contact sealing characteristics.  
         [0035]      FIG. 10  is a cross sectional schematic view of a self expanding branch graft stent system  170 . In this system a center member  172  extends to and is fixed to a catheter tip  174 . A stent cup-disc plunger  176  ( FIG. 10A ) is attached to the center member  172  such that a self expanding stent  178  to which a graft material  180  is attached is disposed between the stent cup plunger  176  and the catheter tip  174 . A full length sheath  182  covers the full length of the center member  172  and seats in a perimeter groove on the catheter tip  174 . Similar to the configuration described for the balloon expandable system above, graft material  180  contains a series of pockets to contain the distal expandable ring (hoop-stent)  184  and a similar ring pocket to contain the proximal expandable ring (hoop-stent)  186 . A distal ring (hoop-stent) stop  188  and proximal ring (hoop-stent) stop  190  are fixed to the center member  172  to maintain the pre deployment distance between the distal expandable ring (hoop-stent)  184  and the proximal expandable ring (hoop-stent)  186 .  
         [0036]      FIG. 11  is a close up of a compressed configuration of expandable hoop type ring contained in a branch graft stent system. An outer sheath  194  contains in a compressed configuration a graft material  196  which is sewn or otherwise bonded to pocket material  202  and pocket material  204 , respectively. A distal ring hoop pocket seam of the distal pocket shown as a dashed line  206  is the distal limit of the distal pocket containing a compressed coiled nitinol hoop  198  while a proximal ring hoop pocket seam shown as dashed line  208  of the distal pocket connects the distal pocket material  202  to the graft material  196  to act as a closed pouch to contain the compressed coiled nitinol hoop  198 . Similarly a compressed proximal coiled nitinol hoop  200  is contained within a hoop pocket (pouch) formed by proximal pocket material  204  which is bonded or sewn to the graft material  196  at coaxial circumferentially ring hoop pocket seams, i.e., distal seam of the proximal pocket  210 , and proximal seam of the proximal pocket  212 . A ring receiving pocket separation (seal) section  214  separates the distal seam of the proximal pocket  210  from the proximal seam of the distal pocket  208 .  
         [0037]      FIG. 11A  is a close up of an alternate compressed configuration of expandable hoop type ring contained in a branch graft stent system of that shown in  FIG. 11 . An outer sheath  194 ′ contains in a compressed configuration graft material  196 ′ which is sewn or otherwise bonded to pocket of pre enlarged material  203  forming a pocket for receiving and setting the maximum diameter of expansion of a compressed coiled nitinol hoop  198 ′. A distal ring hoop pocket seam of the distal pocket shown as a dashed line  206 ′ in the distal limit of the distal pocket containing a compressed coiled nitinol hoop  198  while a proximal ring hoop pocket seam shown as dashed line  208 ′ of the distal pocket connects the distal pocket material  202  to the graft material  196 ′ to act as a closed pouch to contain the compressed coiled nitinol hoop  198 ′. In this instance the graft material  196 ′ which extends between the distal and proximal ring hoop pocket seams  206 ′ and  208 ′ has a bulge (disk creating) diameter which results in an annular fold of graft material that is folded over when the adjacent graft material (as shown in  FIG. 11A ) or tucked inside and not shown as seen or not seen in  FIG. 11 . such that stretching of the graft material by the expanding ring (e.g.,  198 ′) is not needed and does not take place. The angled (or tipped over) orientation of the compressed coiled nitinol hoop  198 ′ shown in  FIG. 11A , shows the position of the end of the hoop in the end of the pocket  203 , as might be experienced if a fully expanded hoop in a graft material pocket were compressed to fit into a delivery sheath (e g.,  194 ′).  
         [0038]      FIG. 12  shows configuration of the coiled nitinol hoops  98 ,  200  in an expanded configuration. The sheath  194  shown in  FIG. 11  having been retracted, the distal nitinol hoop  198  has expanded from its compressed configuration as isolated in  FIG. 13A  shown as  198 ( c ) to an expanded configuration as shown in  FIG. 13B  identified by  198 ( e ). The proximal coiled nitinol hoop  200  is similarly expanded so that the two expanded hoops within the hoop pocket spaces act as expanding discs along the length of the graft material and create an expanding or sealing area at the ring receiving pocket separation section  214  (which may be very short length and have a diameter as large as if not larger than, the main graft opening to which it is intended to seal).  
         [0039]      FIG. 14  shows a self expanding configuration of a self expanding ring stent configuration. An outer sheath  217  contains in a compressed configuration a graft material  218  inside of which, or on the outside of which, is attached or sewn in place a set of distal ( 220 ) and proximal ( 222 ) Z-type self expanding stents. The stents can be sewn to the inside or outside of the graft material or a pocket of material or pocket (pouch) space  224 ,  226  can be provided in which the self expanding stents  220 ,  222  can expand. The pockets  224 ,  226  have axial limits along ring stent pocket seams  228 ,  230 ,  232 ,  234 . The graft material  218  includes a ring receiving pocket separation (seal) section  236  between the two central pockets seam  230 ,  232 .  
         [0040]     One sequence for deployment of a branch graft to be sealed to an opening in a main graft will now discussed by reference to FIGS.  15 A-G and  16 A-G. Irrespective of whether a balloon expandable stent or a self expanding stent is used to anchor the distal end of the graft material in the branch vessel, such a stent can be used solely to anchor the graft or be used multifunctionally to anchor the graft and treat and provide a lesion opening function when there is an occlusion or narrowing in the branch vessel into which the branch graft system is being placed.  
         [0041]     As can be seen in  FIG. 16A  a main vessel endovascular device  264  has been placed across an aneurysm. The endovascular device  264  includes a side branch opening  266  through which a guidewire  260  is threaded into the lumen contained by the branch vessel wall  262 . The balloon expandable branch graft stent system  120  is advanced over the guidewire  260  as seen  FIGS. 16B, 16C , and on into through the branch vessel while continuing to follow the track provided by the guidewire  260  into a position where the radiopaque images of the distal ring (hoop) stop  150  and proximal (hoop) stop  152  straddle the opening  266  (marked by radiopaque markers or some other radiopaque visible marking scheme).  
         [0042]     The branch graft stent system  120  extending into the branch vessel has graft material  138  and a stent  134  compressed on a balloon  128  ( FIG. 16C ). Once in position (according to the ring stops  150 ,  152  discussed above) the balloon  128  is inflated such that the bonded section  136  of the graft material sewn or bonded to the outside of the stent  134  comes into engagement with the branch vessel wall  262  ( FIGS. 15A, 16D ). The outer sheath  160  is retracted in a direction shown by the arrow  238  so that as the open distal end of the sheath  160  moves closer to the compressed location of the distal coiled nitinol hoop  156  and distal ring (hoop) stop  150  ( FIG. 15B ). As the outer sheath  160  is further retracted, the distal coiled nitinol hoop  156  is allowed to expand to its unconstrained diameter configuration and is no longer axially constrained by distal ring hoop stop  150  which remains fixed to the catheter outer member ( FIGS. 15C, 16E ). Once the distal hoop is expanded it may be necessary to move the central members of the catheter assembly forward (or distally) so that the proximal ring stop  152  is brought into close proximity to the location of the main vessel stent graft wall  250  opening  266  having a hoop, grommet, or radiopaque marker  252  so that when the proximal end of the stent graft system is deployed in engagement with or sealing with the main vessel stent graft wall, the sealing engagement can take place without kinking or a rolling of the main and branch graft materials as ring expansion and opening containing forces equalize at their point of contact. (Once repositioning of the catheter to improve proximal alignment has occurred, the distal balloon may be expanded, if necessary, to maintain position of the catheter during the next step). The central inner and outer members  122 ,  144  can be moved in a direction shown by arrow  240 ,  244  ( FIGS. 15E, 16F . respectively) once the proximal ring stop  152  is in position (close to, but inside the main vessel branch opening marked by marker  252 ) the outer sheath  160  can be further retracted as shown by the arrow  238  to release the proximal coiled nitinol hoop  158  from the outer sheath  182  and the axial constraints of the proximal ring hoop stop  152 . ( FIGS. 15F, 16G ). Once the branch graft system has been deployed the delivery catheter and guidewire can be removed to leave the branch graft material  138  in a sealing engagement at a ring receiving pocket separation section (sealing section)  153  with the main vessel stent graft wall  250 .  
         [0043]     The sequence for providing a branch graft stent system includes placing a guidewire through a main vessel stent graft side opening or fenestration, tracking a delivery catheter containing the stent graft branch device into position, deploying the stent at the distal end of the device, retracting the sheath to initially release the distally located hoop or stent, repositioning the catheter to promote the release of the proximal or hoop sealing stent at the correct location, retracting the catheter to release the proximal hoop, and removing the device. An inflatable balloon may or may not be used to re expand the stent or sealing portion in a both balloon expandable and self expanding branch stent graft catheter system. Balloon can also be used to expand to expand stent graft opening  250  after branch vessel graft delivery. Note: Balloon can also be used to expand stent graft opening  250  after branch vessel graft delivery.  
         [0044]     Referring now to  FIGS. 17, 18 ,  19 , and  20 , a primary graft  270  is disposed in a primary vessel and has a branch graft opening or port  272  constructed of an insert molded (combination molded) silicone ring that includes enhanced radiopacity by use of known flexible radiopaque materials. The branch graft assembly  271  can be constructed of a tubular graft material with a proximal support spring (stent)  282  and a distal spring (stent)  284  which in an expanded configuration engages the walls of the renal artery  280 . The details of the connection feature between the branch graft assembly  271  and the primary graft  270  include structures, as discussed above, including a proximal ring structure  276  and distal ring structure  278  ( FIG. 18 ).  
         [0045]      FIG. 19  is an alternate configuration of a branch graft assembly having only a distal spring (stent)  290  engaged with the renal artery  280 . The proximal ring structure  286  may include a (radiopaque) marker band or portion  287 . Similarly, a distal ring structure  288  may include a marker band or portion  289 .  
         [0046]      FIG. 20  shows an alternate configuration of a branch graft assembly where the branch is constructed of flexible and/or reinforced material having a threaded or ring like or accordion like elements or crimps to span the aneurysmal sac and seal to the inner walls to the renal artery  280 . The branch graft assembly of  FIG. 20  includes a proximal ring structure  296  and a distal ring structure  298  constructed as described in detail above for the balloon expandable and self expanding assemblies.  
         [0047]     The description above is intended by way of example only and is not intended to limit the spirit and scope of the invention or its equivalent as understood by persons skilled in the art.