Patent Publication Number: US-2012041544-A1

Title: Stent graft fenestration

Description:
RELATED APPLICATION/S 
     This application claims the benefit of U.S. Provisional Application No. 61/165,946 filed on 2 Apr. 2009 the disclosure of which is incorporated herein by reference in its entirety. The contents of all of the above documents are incorporated by reference as if fully set forth herein. 
    
    
     FIELD AND BACKGROUND OF THE INVENTION 
     The present invention, in some embodiments thereof, relates to endovascular procedures and, more particularly, but not exclusively, to a device and a method for deployment of a stent graft in a blood vessel including at least one branch vessel. 
     In-situ fenestration may be used during endovascular repair of a blood vessel at junctions with branch vessels. A typical procedure may involve placing a stent graft inside the vessel during which time one or more junctions are covered by the stent. During this time, blood flow into a branch vessel is interrupted, potentially exposing a patient undergoing the endovascular procedure to risk of complications and even death. Once the stent graft is in place, fenestration may be performed at each of the one or more junctions allowing blood flow to be restored into the one or more branch vessels. 
     Methods are known in the art for maintaining blood flow into the branch vessel during the endovascular procedure. Some methods may include use of a prefenestrated stent graft. Others may include separate conduits for allowing blood flow into the branch vessel. Two examples of the latter are described below. 
     WO 2007/082343 A1 “METHOD AND DEVICE FOR GRAFT FENESTRATION” relates to, “The present invention provides a method of creating fenestrations in situ through a body wall of a covered stent or endograft lumen. The fenestration is aligned with a side branch of the body lumen. The created fenestration of the graft ( 4 ) is in communication with a side branch. That is the patent or open side branch permits fluid communication from the main lumen across the stented or endograft lumen. Tools ( 41 ,  61 ,  51 ,  51 B,  62 ) are described to carry out these fenestrations for either a graft ( 4 ) or a side branch that is communication with a graft ( 4 ) in vivo. Further these tools are described to carry out these methods for both in situ branch tissue and graft fenestration and alignment of the fenestrations The present invention provides a method for in situ fenestration, the method including the steps of: positioning a graft ( 4 ) or graft unit ( 4 ) in situ within a body lumen ( 1 ) and forming an initial void or space ( 6 ) between graft unit ( 4 ) and the inner wall ( 11 ) of the body lumen ( 1 ). The present invention also provides a catheter ( 41 ,  61 ) including a: a) a distal tip ( 62 ,  51 ,  51 B) that can perform a piercing and opening action; and or b) a distal tip ( 62 ,  51 ,  51 B) rotates by means of a drive shaft ( 52 ,  53 ) within the catheter ( 61 ) to cut and or open a tissue or graft ( 4 ) to form fenestration; and or c) a stabilization means ( 55 ,  42 A,  42 B,  51 ,  51 B) to stabilize the position of the catheter ( 41 ,  61 ) during fenestration.” 
     Ohrlander et al. disclose in “The Chimney Graft: A Technique for Preserving or Rescuing Aortic Branch Vessels in Stent-Graft Sealing Zones”, Journal of Cardiovascular Therapy; August 2008; 15, 427-432; “A covered stent is deployed parallel to the main aortic stent-graft, protruding somewhat proximally, like a chimney, to preserve flow to a vital side branch covered by the aortic stent-graft. Use of a chimney graft makes it possible to use standard off-the-shelf stent-grafts to instantly treat lesions with inadequate fixation zones, providing an alternative to fenestrated stent-grafts in urgent cases, in aneurysms with challenging neck morphology, and for reconstituting an aortic side branch unintentionally compromised during endovascular repair. This technique has been used successfully in 10 patients, combining chimney grafts in the renal, superior mesenteric, left subclavian, left common carotid, and innominate arteries with stent-grafts in the abdominal (n=6) or thoracic (n=4) aorta. There has been no late chimney graft-related endoleak on imaging studies up to 8 months.” 
     SUMMARY OF THE INVENTION 
     According to an aspect of some embodiments of the present invention there is provided a method of deploying a stent graft in a blood vessel with at least one side branch vessel, comprising (a) forming a blood flow conduit between the branch vessel and the blood vessel such that a vessel section of the conduit is axially located inside the blood vessel and a branch section is positioned inside the branch vessel, (b) deploying the stent graft inside the blood vessel so that blood flow into the at least one side branch is blocked by the stent graft and continues through the blood flow conduit, (c) forming an opening suitable for allowing blood flow between the blood vessel and the branch vessel, and (d) interrupting blood flow in the vessel section of the conduit. 
     According to some embodiments of the present invention, the method comprises forming the blood flow conduit with a stent adapted to transport blood from the blood vessel to the at least one side branch vessel. Optionally, the stent is a self-expanding stent. Optionally, the stent is a balloon-expandable stent. 
     According to some embodiments of the present invention, the method comprises parallely locating the vessel section between an inner wall of the blood vessel and the deployed stent graft. 
     According to some embodiments of the present invention, the method comprises forming the blood flow conduit such that the vessel section resists a compressive force exerted by the deployed stent graft. 
     According to some embodiments of the present invention, the method comprises interrupting blood flow in the vessel section by collapsing the vessel section. Optionally, the method comprises collapsing the vessel section under a compressive force exerted by the deployed stent graft when the stent graft is expanded. Optionally, the method comprises expanding the stent graft with an expandable balloon. 
     According to some embodiments of the present invention, the method comprises interrupting blood flow in the vessel section by mechanically manipulating the stent. Optionally, mechanically manipulating the stent comprises sliding a slip knot to cause disengagement of wires connected to the knot causing collapse of at least the vessel section. Optionally, mechanically manipulating the stent comprises pushing a joint to cause disengagement of wires connected to the joint causing collapse of at least the vessel section. Optionally, mechanically manipulating the stent comprises retrieving a rod supporting wires causing collapse of at least the vessel section. 
     According to some embodiments of the present invention, the method comprises forming the blood flow conduit such that blood flow through the conduit is uninterrupted when the branch section and the vessel section are angled with respect to one another. Optionally, an angle between the branch section and the vessel section ranges from 20°-180°. 
     According to some embodiments of the present invention, the method comprises forming the opening by initially inserting a fenestration device through the vessel section and making a perforation in the conduit and the stent graft. Optionally, the method comprises forming the opening by initially inserting a fenestration device through the stent graft and making a perforation in the conduit and the stent graft. Optionally, the method further comprises inserting an expansion balloon into the perforation and expanding the balloon to increase the size of the perforation to that of the opening. Optionally, the method comprises inserting the balloon from the branch vessel. Optionally, the method comprises inserting the balloon from the blood vessel. 
     According to some embodiments of the present invention, the method comprises leaving at least a portion of the conductor inside the blood vessel and/or branch vessel. Optionally, the method comprises biodegrading the at least a portion of the conductor. According to an aspect of some embodiments of the present invention there is provided a blood flow conductor comprising a vessel section and a branch section connected together by a bendable section, wherein at least the vessel section is adapted to be collapsed after deployment in the aorta and is strong enough to maintain structural rigidity when compressed between a deployed stent graft and the aortic wall. 
     According to some embodiments of the present invention, the blood flow conductor comprises a stent. Optionally, the stent is a self-expanding stent. Optionally, the stent comprises one or more wires configured to act as struts for maintaining the structural rigidity. Optionally, the one or more wires are coil shaped. Optionally, the one or more wires comprise a shape memory alloy. 
     According to some embodiments of the present invention, the stent is a balloon-expandable stent. Optionally, the vessel section of the stent is pliable. 
     According to some embodiments of the present invention, the blood flow conductor comprises a sheath for transporting the stent to a location for deployment in the aorta. Optionally, the stent is adapted to be folded into the sheath following collapse of at least the vessel section. 
     According to some embodiments of the present invention, the vessel section is adapted to be axially displaced in the aorta. Optionally, the branch section is adapted to be inserted in a branch vessel. Optionally, the bendable section is adapted to bend through an angle ranging from 20°-180°. Additionally or alternatively, the bendable section is kink-resistant. 
     According to some embodiments of the present invention, the blood flow conductor comprises a wire adapted to collapse the vessel section when pulled in a proximal direction. Optionally, the blood flow conductor comprises a sliding knot for collapsing the vessel section. Optionally, the blood flow conductor comprises a breakable joint for collapsing the vessel section. Additionally or alternatively, the blood flow conductor comprises a hook for collapsing the vessel section. 
     According to some embodiments of the present invention, the blood flow conductor comprises at any one point a circular cross-section. 
     According to some embodiments of the present invention, the blood flow conductor comprises a diameter ranging from 3 mm-15 mm. 
     According to an aspect of some embodiments of the present invention there is provided a medical kit comprising an aortic stent graft; and a blood flow conductor comprising a vessel section and a branch section connected together by a bendable section, wherein at least the vessel section is adapted to be collapsed after deployment in the aorta and is strong enough to maintain structural rigidity when compressed between a deployed stent graft and the aortic wall. 
     According to some embodiments of the present invention, the medical kit comprises a fenestration device for making a fenestration in the stent graft and the conductor. Optionally, the fenestration device comprises a catheter adapted to accommodate a needle for perforating the stent graft and the conductor. Optionally, the fenestration device includes at least one expandable balloon for bending a tip of the catheter. 
     According to some embodiments of the present invention, the medical kit comprises a guide wire for directing the fenestration device to a fenestration location. Optionally, the guide wire is adapted to perforate the stent graft and the conductor. Optionally, the guide wire is adapted to be inserted from the branch section of the conductor for perforating the stent graft and the conductor. Optionally, the guide wire is adapted to be inserted from the vessel section of the conductor for perforating the stent graft and the conductor. Additionally or alternatively, the guide wire is adapted to be inserted from the stent graft for perforating the stent graft and the conductor. 
     According to some embodiments of the present invention, the medical kit comprises a branch stent and/or a branch stent graft for inserting through the fenestration and in the branch vessel. 
     Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced. 
       In the drawings: 
         FIGS. 1-17  schematically illustrate an exemplary implementation of the method of deployment of an exemplary stent graft in a blood vessel including at least one branch vessel using an exemplary branching scaffold, according to an embodiment of the present invention; 
         FIGS. 18-33  schematically illustrate an exemplary implementation of the method of deployment of an exemplary stent graft in a blood vessel including at least one branch vessel, using an exemplary stent, according to some embodiments of the present invention; 
         FIGS. 34-36  schematically illustrate an exemplary branching scaffold and a method of loss of structural rigidity in the scaffold, according to some embodiments of the present invention; 
         FIGS. 37-40  schematically illustrate an exemplary branching scaffold and a method of loss of structural rigidity in the scaffold, according to some embodiments of the present invention; 
         FIGS. 41-43  schematically illustrate an exemplary branching scaffold and a method of loss of structural rigidity in the scaffold, according to some embodiments of the present invention; 
         FIG. 44  schematically illustrates an exemplary branching scaffold, according to some embodiments of the present invention; 
         FIG. 45  schematically illustrates an exemplary branching scaffold, according to some embodiments of the present invention; 
         FIG. 46  schematically illustrates a fenestration device, according to some embodiments of the present invention; 
         FIG. 47  schematically illustrates a fenestration device, according to some embodiments of the present invention; 
         FIG. 48  schematically illustrates a fenestration device, according to some embodiments of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     The present invention, in some embodiments thereof, relates to endovascular procedures and, more particularly, but not exclusively, to a device and a method for deployment of a stent graft in a blood vessel including at least one branch vessel. 
     An aspect of some embodiments of the present invention relates to a method of deploying a stent graft in a blood vessel including at least one branch vessel by, in the following order, (a) forming a conduit for blood flow from the blood vessel into the branch vessel, (b) deploying the stent graft inside the blood vessel, (c) forming an opening connecting the stent graft with the conduit to allow blood flow between the blood vessel and the branch vessel through the opening (fenestration), and (d) interrupting blood flow in a vessel section of the conduit. Optionally, the blood flow is interrupted by collapsing the vessel section internally. Optionally, the vessel section collapses to a thickness of less than 2 mm, less than 1.5 mm, less than 1 mm, less than 0.5 mm, less than 0.2 mm, less than 0.1 mm, less than 0.05 mm, less than 0.02 mm, less than 0.01 mm. Optionally, the stent graft is an aortic stent graft. Optionally, the stent graft is any type of stent graft used for endovascular repair of an aneurysm. Optionally, the stent graft is any type of stent graft used in endovascular treatment of stenosis. Optionally, the stent graft is any type of conductor having characteristics suitable for transporting blood from the blood vessel into the branch vessel, for example, from the aorta into any aortic branch vessel. Optionally, the conductor is a removable stent or a removable stent graft. Additionally or alternatively, the blood flow conduit is formed from the blood vessel into the branch vessel. Optionally, the blood flow conduit is formed from the branch vessel into the blood vessel. Optionally, a blood flow conduit is formed for each branch vessel in a blood vessel comprising a plurality of branch vessels. Optionally, at least a portion of the conductor is adapted to remain in the blood vessel (following vessel section collapse) and/or the branch vessel. Additionally or alternatively, the stent graft is adapted to biodegrade (following vessel section collapse). 
     In some embodiments, the blood flow conduit is formed by a blood flow conductor adapted to transport blood from the blood vessel to the branch vessel. Optionally, the blood flow conductor includes a stent. Optionally, the conductor includes a vessel section axially positioned inside the blood vessel and a branch section positioned inside the branch vessel. Additionally or alternatively, the vessel section and the branch section are joined together by a bendable section. Optionally, the conductor includes a length ranging from 3 cm-20 cm, for example, 3 cm-6 cm, 6 cm-10 cm, 10 cm-15 cm, 15 cm-20 cm. Optionally, a length of the vessel section and a length of the branch section are different. Optionally, the length of the vessel section and the branch section are the same. Additionally or alternatively, the length of the vessel section is less than 15 cm, less than 12 cm, less than 9 cm, less than 6 cm, less than 3 cm. Optionally, the length of the branch section is less than 15 cm, less than 12 cm, less than 9 cm, less than 6 cm, less than 3 cm. Optionally, a length of the bendable section is less than 10 cm, less than 6 cm, less than 3 cm, less than 1 cm. 
     In some embodiments, the blood flow conductor includes a metal coverage area ranging from 1%-35% of total surface coverage, for example 1%-10%, 10%-15%, 15%-25%, 25%-35%. Optionally, a total surface coverage ranges from 10%-95%, for example, 10%-25%, 25%-45%, 45%-70%, 70%-95%. Optionally, a strut thickness in the conductor ranges from 200 μm-800 μm, for example, 200 μm-350 μm, 350 μm-550 μm, 550 μm-800 μm. Optionally, a strut width in the conductor ranges from 200 μm-800 μm, for example, 200 μm-350 μm, 350 μm-550 μm, 550-800 μm. Optionally, strut thickness and/or strut width is greater than 800 200 μm-800 μm, for example, 200 μm-350 μm, 350 μm-550 μm, 550 μm-800 μm. 
     In some embodiments, the blood flow conductor includes solid walls so that there is no blood flow through the walls. Optionally, the conductor includes 100% surface coverage. Optionally, the conductor includes a biodegradable material. Optionally, the conductor includes a biocompatible material. 
     In some embodiments, the vessel section is parallely positioned inside the blood vessel between the deployed stent graft and an inner wall of the blood vessel. Optionally, the vessel section has a structural rigidity adapted to resist a compressive force radially exerted by the stent graft and by an inner wall of the blood vessel. Additionally or alternatively, the structural rigidity prevents deformation of the vessel section. Optionally, the vessel section maintains a patency. Optionally, the vessel section is adapted to lose structural rigidity and collapse under the compressive force exerted by the stent graft when expanded by an inflatable balloon placed inside the stent graft, hereinafter referred to as balloon-expanded stent. Optionally, collapse of the vessel section interrupts blood flow through the vessel section. Additionally or alternatively, the vessel section is adapted to collapse under the compressive force exerted by the stent graft when expanded by stent expanding means other than an inflatable balloon, for example, by the introduction of large diameter object (larger diameter than the stent graft) into the stent graft. Optionally, the vessel section is adapted to lose structural rigidity and/or collapse through mechanical manipulation, for example, by acting on mechanical elements forming the conductor such as, for example, a wire, a rod, a slip knot, a joint, a hook, or any combination thereof. Optionally, pulling or cutting at least one wire causes a loss of structural rigidity in the vessel section. Optionally, pulling or cutting the at least one wire causes the vessel section to collapse. Optionally, release of a slip knot causes loss of structural rigidity and/or collapse of the vessel section. Optionally, pulling or pushing on a rod causes loss of structural rigidity and/or collapse of the vessel section. Optionally, removal of a stiffener tube inserted in the vessel section causes loss of structural and/or collapse of the vessel section. Additionally or alternatively, exposure to body temperature and/or body fluids over a predetermined period of time causes the vessel section to lose structural rigidity and/or collapse. Optionally, structural rigidity is also lost in the branch section. 
     In some embodiments, the branch section is fitted inside the branch vessel and is adapted to adhere to the inner wall of the branch vessel. Optionally, the branch section is adapted to remain stationary inside the branch vessel. Optionally, the branch section includes a lumen for accommodating a branch vessel stent graft. Optionally, a branch stent graft is implanted in the branch vessel following fenestration of the branch section and the stent graft. 
     In some embodiments, the bendable section is adapted to bend through an angle greater than 90°, for example, in a range between 0°-100° inclusive, 0°-120° inclusive, 0°-150° inclusive, 0°-180 inclusive, without kink so that blood flow through the section is uninterrupted regardless of the angle of bend. °. Optionally, the bendable section is adapted to bend through an angle in a range from 20°-180°, for example 20°-160°. Additionally or alternatively, bending of the bendable section without kink includes a reduction in the cross-sectional area of the section of less than 10%, less than 20%, less than 30%, less than 40%, less than 50%, less than 60%. Optionally, the bendable section is suitable for fenestration. 
     In some embodiments, the blood flow conductor includes a circular cross section at any point along its whole length. Optionally, the conductor is cylindrically shaped. Optionally, a diameter of the conductor ranges from 3 mm-15 mm, for example 3 mm-5 mm, 5 mm-8 mm, 8 mm-12 mm, 12 mm-15 mm. Optionally, the vessel section diameter is of a first diameter and the branch section of a different second diameter. Optionally, the cross-sectional shape of the conductor is non-circular, for example, elliptical, oval. 
     In some embodiments, the blood flow conduit is formed by a self expanding stent. This self expanding stent, which may be also be referred to as a “branching scaffold”, may be made from a metal, for example, an elastic metal such as a shape memory alloy. Optionally, the shape memory alloy includes nitinol and/or stainless steel. Optionally, the branching scaffold includes any bio-compatible and/or bio-degradable material. The branching scaffold may include one or more wires adapted to act as struts for enabling the vessel section to resist the compressive force of the stent graft. Optionally, the one or more wires are coil-shaped (helical). Optionally, the one or more wires are intertwined. Optionally, the one or more wires are spaced for accommodating the fenestration. Optionally, the one or more wires are arranged in any shape or form suitable for resisting the compressive force of the stent graft and the inner wall, enable fenestration, and allow for collapsing of the vessel section as previously described. Additionally or alternatively, the branching scaffold includes the bendable section joining the vessel section of the scaffold with the branch section of the scaffold. Optionally, a branch stent graft inserted through the fenestration is accommodated inside the branch section. 
     In some embodiments, the branching scaffold includes a single coiled wire. Optionally, the branching scaffold includes 2-4 coiled wires. Optionally, the number of coiled wires is greater than 4, for example 6-10 wires, 10-20 wires, 20-50 wires, 50-100 wires, or more. Optionally, the scaffold includes a central rod which connects the wires together by a single loop (slip knot) at a distal end of the rod, allowing the wires to disconnect from one another when the knot slides. Optionally, the central rod connects the wires together by a breakable joint allowing the wires to be disconnected from one another. Optionally, the wires are connected together to the rod by a removable hook at the distal end which allows for the wires to disconnect from one another. Additionally or alternatively, the central rod is a wire. Optionally, the wires are connected to the rod by a plurality of loops at different locations along the rod. 
     In some embodiments, the branching scaffold is included in a sheath or sleeve adapted to be inserted into the blood vessel. Optionally, the sheath includes stiffness substantially greater than that of the branching scaffold. Optionally, the sheath is of an external diameter ranging from 1 mm-6 mm, for example 1 mm-2 mm, 2 mm-3 mm, 3 mm-4 mm, 4 mm-5 mm, 5 mm-6 mm. Optionally, the branching scaffold is deployed by extending the rod out of the sheath in a distal direction through the blood vessel and through the junction into the branch vessel. Optionally, the deployment may be through the branch vessel and through the junction into the blood vessel. Additionally or alternatively, the branching scaffold may be retrieved by pulling the rod in a proximal direction into the sheath. Optionally, the branching scaffold is adapted to collapse onto itself so that its diameter is reduced to a dimension suitable to fit the scaffold into the sheath when retrieved. Additionally or alternatively, the branching scaffold is adapted to deform so that the wires and the rod are disconnected from one another, allowing the wires to substantially straighten for retrieving into the sheath. Optionally, only a portion of the wires is retrieved. Optionally, the portion of the wires is those in the branch section. Optionally, the wires remain connected to the rod at a proximal end of the rod. 
     In some embodiments, retrieving the rod causes the vessel section to loose structural rigidity. Optionally, the branch section loses structural rigidity. Optionally, structural rigidity is lost by sliding at least one slip knot (optionally pulling the rod in a proximal direction and the knot slips out). Optionally, structural rigidity is lost by cutting the rod. Optionally, structural rigidity is lost by pushing the rod in a distal direction and breaking a union of the wires to a joint at a distal end of the rod. Optionally, twisting of the rod will cause the wires to unhook from a hook on a distal end of the rod. Additionally or alternatively, structural rigidity is lost by cutting at least one of the wires. Optionally, structural rigidity is lost by pulling at least on one of the wires. Optionally, for branching scaffolds including a thermal shape memory alloy, a temperature change may be induced in the scaffold for causing loss of structural rigidity; for example, a balloon filled with a saline at a suitable temperature may be inserted into the vessel section to cause a reduction in resilience. Optionally, for a biodegradable branching scaffold or a soluble scaffold, structural rigidity is lost after a predetermined period of time has passed. 
     In some embodiments, the blood flow conduit is formed by a balloon-expandable stent. Optionally, a bendable balloon is used to expand the stent. Optionally, the bendable balloon is bendable through the bending angle of the bendable section of the stent. Optionally, the balloon-expandable stent is expanded by stent-expanding means other than a balloon. Optionally, the stent includes materials similar to that in the in the branching scaffold. Optionally, the stent includes a structural rigidity similar to that of the branching scaffold. Additionally or alternatively, the stent includes a vessel section which is substantially pliable, allowing the section to substantially flatten under the compressive force of the balloon-expanded stent graft in the blood vessel so as to interrupt blood flow through the vessel section. Optionally, the vessel section loses structural rigidity by cutting and/or pulling wires included in the stent. Optionally, the vessel section loses structural rigidity by sliding a slip knot. Additionally or alternatively, structural rigidity is lost by removing a rod included in the stent. Optionally, retrieval of at least a portion of the stent causes loss of structural rigidity in the vessel section. Optionally, the vessel section is occluded by a balloon or other implantable occlusion means. Optionally, the stent is included in a sheath which is inserted into the blood vessel. Optionally, the sheath is inserted from the branch vessel. 
     In some embodiments, the blood flow conduit is formed by a stent graft including a fabric or other impervious material such as, for example, Dacron, PTFE, and the like. Optionally the stent characteristics of the stent graft are similar to that of the branching scaffold or the balloon-expandable stent. Optionally, wires in the stent graft have a cross-section so that the aortic wall in not damaged by the wires pressing against it. Additionally or alternatively, the stent graft includes a plain fabric tube. Optionally, the branch section of the stent graft and the stent graft in the blood vessel are anatomosed. Optionally, the vessel section of the stent graft is substantially flattened by the compressive force exerted by the balloon-expanded stent graft in the blood vessel interrupting blood flow through the vessel section. Optionally, blood flow in the vessel section is interrupted by inserting a one way valve into the vessel section following fenestration. Optionally, the valve is adapted to disconnect the fenestration and the branch section of the stent graft from the vessel section to prevent blood flow into the blood vessel through the vessel section. Optionally, blood flow in the vessel section is interrupted with a balloon or other implantable occlusion device. Additionally or alternatively, the stent is a self-expanding stent. Optionally, the stent is a balloon-expandable stent. 
     In some embodiments, the blood flow conduit is formed by a biodegradable, soluble, or bio-modifiable stent (e.g. Poly-l-Lactic Acid or other polymer or erodible, biodegradable metal such as magnesium). Optionally, the stent is a self-expanding stent or a balloon-expandable stent with structural rigidity similar to that of the branching scaffold or the balloon-expandable stent. Optionally, the stent is designed so that its structural rigidity is maintained for a relatively short period of time such as, for example several minutes (for example 15 minutes), an hour, a number of days, or more. Optionally, rapid modification of the structural rigidity of the stent is desired for reducing the stiffness or resilience of vessel section, thereby enabling it to collapse under the force of expanded stent graft in the blood vessel following fenestration. Additionally or alternatively, a stent material is stretchable, tearable or breakable to accommodate the opening. Optionally, substantially complete biodegradation, dissolution and absorption extends over a longer period of time, such as days or months. 
     In some embodiments, fenestration is performed under fluoroscopy and angiography, using techniques know in the art. Optionally, the fenestration may be opened in a direction from the stent graft in the blood vessel towards the blood flow conduit. Optionally, the fenestration is opened in a direction from the blood flow conduit towards the stent graft in the blood vessel. Additionally or alternatively, the fenestration is located in the bendable section of the blood flow conduit positioned at the junction of the branch vessel with the blood vessel. Optionally, the bendable section is punctured with a small hole which is then expanded to a size of the fenestration. Optionally, a fenestration device includes a catheter with a retractable (movable) sharp needle to perform the puncture at the site of the opening. Optionally, the needle is a bent hollow needle. Optionally, the needle is a Rosch-Uchida/Ushida needle. Optionally, a guide wire is passed through the needle. Optionally, a stiff guidewire may be used in lieu of the needle. Optionally, the catheter includes a straight shape when in a neutral position. Optionally, the fenestration device is inserted through the same sheath including the branching scaffold or the stent (optionally, a same sheath is used for the branching scaffold and the balloon-expandable stent). Optionally, the fenestration device includes a mechanism for bending the tip of the catheter and pushing it against the wall of the stent graft at the point intended for fenestration. Optionally, the mechanism includes a balloon which extends beyond the tip of the catheter and is adapted to bend the tip. Additionally or alternatively, several balloons are configured asymmetrically to push the catheter tip to one side. Optionally, a small balloon is located on a side of the catheter towards which the catheter bends, and one or more longer balloons are located on an opposing side of the catheter, extending beyond the catheter tip. Additionally or alternatively, the catheter includes one or more wires running along one aspect of its wall. Optionally, the catheter is straight when the wires are in a neutral position. Optionally, the catheter tip is bent to one side when the wires are pushed forward in a distal direction. Additionally or alternatively, the catheter tip is bent when the wires are pulled in a proximal direction. Optionally, the needle may be advanced through the catheter when the catheter tip is at the location of the fenestration for penetrating the graft material. Additionally or alternatively, a guidewire is passed through the needle and into the stent graft. 
     In some embodiments, the blood flow conductor is included in a medical kit for deploying a stent graft in a blood vessel with at least one branch vessel. Optionally, the medical kit includes at least the needle of the fenestration device. Optionally, the fenestration device is included. Additionally or alternatively, a stent graft is included in the medical kit. Optionally, the stent graft is an aortic stent graft. Optionally, the stent graft is any type of stent graft used for endovascular repair of an aneurysm. Optionally, the stent graft is any type of stent graft used in endovascular treatment of stenosis. 
     In some embodiments, a procedure for deploying the stent graft in a blood vessel including at least one branch vessel includes the following steps: 
     (a) Form the blood flow conduit by inserting a blood flow conductor through the junction so that the vessel section is positioned inside the blood vessel and the branch section is in the branch vessel. Insertion of the conduit may be from the blood vessel or from the branch vessel, as determined by the physician. Optionally, the conduit includes the branching scaffold. Optionally, the conduit includes the balloon-expandable stent. Optionally, the conduit includes the stent graft including a fabric or other impervious material such as, for example, Dacron, PTFE, and the like. Optionally, the conduit includes the biodegradable, soluble, or bio-modifiable stent. Additionally or alternatively, for more than one branch vessel, use one conduit of the same type for each branch vessel. Optionally, any combination of the different types of conduits may be used for the plurality of branch vessels.
 
(b) Deploy the stent graft in the blood vessel. Optionally, align the vessel section so that it is parallel to the stent graft. Optionally, align the vessel section so that the opening through which blood flows into the vessel section extends beyond the opening through which blood flows into the stent graft.
 
(c) Insert the fenestration device and manipulate it so that the tip is at the location where the opening is to be made. Optionally, the fenestration device is inserted through the sheath. Optionally, the fenestration device is inserted externally to the sheath. Optionally, the fenestration device is inserted into the conduit from the vessel section. Optionally, the fenestration device is inserted into the conduit from the branch section. Additionally or alternatively, the fenestration device is inserted through the stent graft in the blood vessel. Optionally, the location of the fenestration is in the bendable section.
 
(d) Perforate the location of the fenestration by pushing the needle in the fenestration device. Optionally, the stiff guide wire is used to perforate. Optionally, the perforation is made through both the blood flow conductor and the stent graft in the blood vessel. Optionally, the perforation is made only through the stent graft (as is the case with the branching scaffold). Optionally, methods other than that described herein in step (d), (e), and (f) may be used for fenestration.
 
(e) Manipulate the guide wire so that it passes through the perforation. Optionally, the guide wire is passed from the vessel section or the branch section into the lumen of the stent graft in the blood vessel. Optionally, the guide wire is passed from the lumen of the stent graft in the blood vessel into the vessel section or branch section.
 
(f) Enlarge the fenestration using an instrument adapted to expand the size of the opening to the required size (optionally a size of the branch vessel). Optionally, the mechanism includes an expandable balloon. Optionally, the instrument is guided to the opening using the guide wire.
 
(g) Interrupt blood flow through the vessel section. Optionally, blood flow is interrupted by causing a loss of structural rigidity in the vessel section and expanding the stent graft in the blood vessel. Optionally, the stent graft is expanded by an expandable balloon. Optionally, the loss of structural rigidity is caused by retrieval of the conductor. Optionally, the wire is cut in the conductor. Optionally, the rod is removed in the conduit. Additionally or alternatively, the slip knot is slid in the conduit. Optionally, joint connection to the wires is broken. Optionally, the wires are unhooked. Optionally, partial or whole bio-degradation, bio-dissolution, or bio-modification, or any combination thereof, occurs in the conduit. Optionally, interrupt blood flow in the vessel section using other non-collapsible means, such as, for example, inserting the one-way valve, inserting a balloon, or inserting other implantable means of occlusion. Optionally, blood flow in the vessel section may be interrupted by inserting a branch stent graft into the branch vessel.
 
(h) Optionally, insert a branch stent graft through the fenestration by guiding along a guide wire. Optionally, a stent is inserted. Optionally, the branch stent graft is inserted from the stent graft in the blood vessel. Optionally, the branch stent graft is inserted through the branch vessel in a direction towards the stent graft in the blood vessel. Optionally, the branch stent graft is expanded by unsheathing, balloon expansion, or other suitable method, to create a sealed branch with the stent graft. Optionally, the branch stent graft is manipulated from the direction of the stent graft in the blood vessel. Optionally, the branch stent graft is a balloon-expandable stent graft. Optionally, the balloon is inserted through the fenestration from the stent graft in the blood vessel.
 
     Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. 
     Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details set forth in the following description. The invention is capable of other embodiments or of being practiced or carried out in various ways. 
     Referring now to the drawings,  FIGS. 1-17  schematically illustrate an exemplary implementation of the method of deployment of an exemplary stent graft  116  in a blood vessel  102  including at least one branch vessel  104  using an exemplary branching scaffold  100 , according to an embodiment of the present invention. 
       FIG. 1  shows blood vessel  102  with branch vessel  104  connected to the blood vessel at junction  139 . In some embodiments, blood vessel  102  is the aorta. Optionally, blood vessel  102 , branch vessel  104  and junction  139  include the aortic bifurcation into the iliac arteries; the ascending aorta and coronary arteries; the aortic arch and great vessels; the abdominal aorta and visceral and renal branches; or the iliac bifurcation into internal and external iliac or other arterial branch points. 
       FIG. 2  shows an exemplary sheath  106  inserted into blood vessel  102  and through junction  139  into branch vessel  104 . Optionally, sheath  106  includes a rod  108  adapted to deploy branching scaffold  100 . Optionally, rod  108  includes a wire. 
       FIG. 3  shows a partial deployment of branching scaffold  100 . Optionally, an exemplary branch section  103  of branching scaffold  100  is deployed inside branch vessel  104 . Optionally, branching scaffold is formed from wires  110 . Optionally, wires  110  are connected together to rod  108  at loop  112  on a distal end of the rod. 
       FIG. 4  shows a full deployment of branching scaffold  100 . Optionally, branch section  103  is deployed in branch vessel  104 , an exemplary vessel section  101  is axially deployed in blood vessel  102 , and an exemplary bendable section  105  joining the vessel section and branch section is deployed at junction  139 . Optionally, vessel section  101  is parallel to stent graft  116 . 
       FIG. 5  shows a deployment of stent graft  116  in blood vessel  102 , following deployment of branching scaffold  100 . Optionally, stent graft  116  pushes vessel section  101  against an inner wall  107  of blood vessel  102 . Optionally, wires  110  acts as struts and provide vessel section  101  with a structural rigidity for resisting a compressive force radially exerted on the section by stent graft  116  and inner wall  107 . Optionally, a conduit lumen  114  is formed between stent graft  116  and inner wall  107  extending from a conduit opening  109  and extending into branch vessel  104  for conducting blood flow from blood vessel  102  through junction  139  into the branch vessel. Optionally, blood flows into a lumen  118  in stent graft  116 . 
       FIG. 6  shows an optional deployment of an exemplary fenestration device  121  for perforating a hole to form a fenestration in bendable section  105  and stent graft  116 . Optionally, fenestration device  121  is inserted through sheath  106  and is manipulated through vessel section  101  to bendable section  105  by a guide wire  132 . Optionally, fenestration device  121  can reach bendable section  105  from other directions, for example, from branch vessel  104 . Optionally, a location where the opening is to be made in stent graft  116  (opposite bendable section  105 ) can be reached through blood vessel  102 . Optionally, fenestration device  121  is guided to the location in bendable section  105  where the opening is to be made. Optionally, fenestration device  121  is manipulated into vessel section  101  without being inserted in sheath  106 . Optionally, fenestration device  121  includes an exemplary catheter  120  and two expandable balloons at a distal end, a small balloon  126  on one side of the catheter and an opposing larger balloon  124 . 
       FIG. 7  shows a catheter tip  128  in catheter  120  positioned at a fenestration location  130  in bendable section  105 . Optionally, catheter tip  128  is bent to position at fenestration location  130  by first expanding small balloon  126  and then large balloon  124 . Optionally, large balloon  124  is supported on one side by inner wall  107  and by small balloon  124  on an opposing side for bending catheter tip  128 . 
       FIG. 8  shows fenestration device  121  having perforated stent graft  116  at fenestration location  130 . Optionally, guide wire  132  is passed through the opening from catheter  120  inside vessel section  101  to lumen  118  in stent graft  116 . 
       FIG. 9  shows catheter  120  retrieved from sheath  106 . Optionally, guide wire  132  extends through vessel section  101  and through the opening in fenestration location  130  in bendable section  105 , passing into lumen  118  in stent graft  116 . 
       FIG. 10  shows an exemplary balloon catheter  134  inserted through sheath  106  and guided by guide wire  132  through the opening at fenestration location  130 . Optionally, a distal end of balloon catheter  134  extends into lumen  118  in stent graft  116 . 
       FIG. 11  shows an exemplary balloon  138  in balloon catheter  134  being expanded in the hole at fenestration location  130 . Optionally, balloon  138  expands the hole in fenestration location  130  to a suitable size for allowing blood flow through the hole between branch vessel  104  and blood vessel  102 . 
       FIG. 12  shows an exemplary suitable opening  131  at fenestration location  130  for allowing blood flow between branch vessel  104  and blood vessel  102 . Optionally, balloon catheter  134  retrieved from sheath  106 . Optionally, guide wire  132  remains in place, passing through vessel section  101  and bendable section  105 , through opening  131  and into lumen  118  in stent graft  116 . 
       FIG. 13  shows guide wire  132  transferred from a prior position in blood vessel  102  and vessel section  101  passing through opening  131  into lumen  118 , to an optionally new position where the wire is in branch vessel  104  and branch section  103  and passes through opening  131  into lumen  118 . Branching scaffold  100  remains in place between stent graft  116  and inner wall  107 . 
       FIG. 14  shows an exemplary catheter  140  inserted through blood vessel  102  through lumen  118  and opening  131 , guided by guide wire  132  into branch vessel  104 . Optionally, catheter  140  is adapted to secure alignment of opening  131  with branch vessel  104 . Optionally, sheath  106  operates on an exemplary slip knot  112  connecting wires  110  to the distal end of rod  108  in branching scaffold  100 . Optionally, rod  108  is pulled in a proximal direction so that slips knot  112  slides out the distal end of the rod, releasing wires  110 . Optionally, the structural rigidity of branching scaffold  100  is lost when wires  110  are released. 
       FIG. 15  shows rod  108  retrieved through sheath  106 . Optionally, slip knot  112  is released (as described above) and wires  110  are disconnected. Optionally, branching scaffold  100  loses structural rigidity. 
       FIG. 16  shows branching scaffold  100  pulled in a proximal direction  142  out of branch vessel  104  and into blood vessel  102 . Optionally, vessel section  101  and bendable section  105  are retrieved into sheath  106 . Optionally, branching scaffold  100  has lost structural rigidity. 
       FIG. 17  shows stent graft  116  fully deployed. Optionally branching scaffold  100  is fully retrieved into sheath  106 . Optionally stent graft  116  is balloon-expanded and fills a space occupied by conduit lumen  114  (see  FIG. 5 ) abutting with inner wall  107 . Optionally, opening  131  is displaced to junction  139  interconnecting branch vessels  104  and blood vessel  102 . Optionally, suitable blood flow exists between blood vessel  102  and branch vessel  104  through opening  131 . Optionally, catheter  140  and guide wire  132  may be removed from the side of blood vessel  102 . Optionally, catheter  140  and guide wire  132  may be removed from the side of branch vessel  104 . Additionally or alternatively, sheath  106  may be removed. 
     Referring now to the drawings,  FIGS. 18-33  schematically illustrate an exemplary implementation of the method of deployment of an exemplary stent graft  216  in a blood vessel  202  including at least one branch vessel  204 , using an exemplary stent  200 , according to some embodiments of the present invention. Stent  200  may be a balloon-expandable stent. Optionally, stent  200  is a self-expanding stent. Optionally, stent  200  is expandable by expanding means other than a balloon. 
       FIG. 18  shows blood vessel  202  with branch vessel  204  connected to the blood vessel at junction  239 . Blood vessel  202 , branch vessel  204 , and junction  239  may be the same as that shown in  FIG. 1  at  102 ,  104  and  139 . 
       FIG. 19  shows full deployment of stent  200 . Optionally, branch section  203  is deployed in branch vessel  204 , an exemplary vessel section  201  is axially deployed in blood vessel  202 , and an exemplary bendable section  205  joining the vessel section and branch section is deployed at junction  239 . Optionally, vessel section  201  is parallel to stent graft  216 . 
       FIG. 20  shows a deployment of stent graft  216  in blood vessel  202 , following deployment of stent  200 . Optionally, stent graft  216  pushes vessel section  201  against an inner wall  207  of blood vessel  202 . Optionally, vessel section  202  includes a structural rigidity for resisting a compressive force radially exerted on the section by stent graft  216  and inner wall  207 . Stent  200  includes a conduit lumen  214  (between stent graft  216  and inner wall  207 ) extending from a conduit opening  209  and extending into branch vessel  204  for conducting blood flow from blood vessel  202  through junction  239  into the branch vessel. Optionally, blood flows into a lumen  218  in stent graft  216 . Optionally, conduit opening  209  and an opening to stent lumen  218  in stent graft  216  are aligned. 
       FIG. 21  shows a deployment of an exemplary fenestration device  221  for perforating a hole to form a fenestration in bendable section  205  and stent graft  216 . Optionally, fenestration device  221  includes a catheter  220  which is manipulated through vessel section  201  to bendable section  205  by a guide wire  232  (see  FIG. 21 ). Optionally, fenestration device  221  including a catheter tip  228  is guided to a fenestration location  230  in bendable section  205  where an opening is to be made. Optionally, fenestration device  221  can reach bendable section  205  from other directions, for example, from branch vessel  204 . Optionally, fenestration location  230  where the opening is to be made in stent graft  216  can be reached through blood vessel  202 . 
       FIG. 22  shows fenestration device  221  having perforated bendable section  205  and stent graft  216  at fenestration location  230  opening an exemplary hole  231 . Optionally, guide wire  232  is passed through opening  231  from catheter  220  inside vessel section  201  to lumen  218  in stent graft  216 . 
       FIG. 23  shows guide wire  232  extending from inside catheter  220  through vessel section  201  and through opening  231  in bendable section  205  and stent graft  217 , passing into lumen  218  in stent graft  216 . 
       FIG. 24  shows guide wire  232  extending  220  through vessel section  201  and through opening  231  in bendable section  205  and stent graft  217 , passing into lumen  218  in stent graft  216 . Catheter  220  has been removed. 
       FIG. 25  shows guide wire  232  transferred from a prior position in blood vessel  202  and vessel section  201  passing through opening  231  into lumen  218 , to an optionally new position where the wire is in branch vessel  204  and branch section  203  and passes through opening  231  into lumen  218 . Stent  200  remains in place between stent graft  216  and inner wall  207 . 
       FIG. 26  shows an exemplary balloon  238  for expanding a size of opening  231  guided on guide wire  232  to the opening. Optionally, balloon  238  is inserted through blood vessel  202 . Optionally, balloon  238  is inserted through branch vessel  204 . 
       FIGS. 27 and 28  show balloon  238  being expanded inside opening  231 . Optionally, balloon  238  expands opening  231  to a suitable size for allowing blood flow through the opening between branch vessel  204  and blood vessel  202 . Optionally, blood flow through vessel section  201  and bendable section  205  into branch section  203  is interrupted. 
       FIG. 29  shows an exemplary suitable opening  231  for allowing blood flow between branch vessel  204  and blood vessel  202 . Optionally, balloon  238  is deflated and retrieved along guide wire  232 . Optionally, balloon  238  is retrieved through blood vessel  202 . Additionally or alternatively, balloon  238  is retrieved through branch vessel  204 . Optionally, guide wire  232  remains in place, passing through branch section  203  and through opening  231  and into lumen  218  in stent graft  216 . 
       FIG. 30  shows an exemplary balloon  245  for expanding stent graft  216  inserted in blood vessel  202 . Optionally, a guide wire  247  is in guided through blood vessel  202  into lumen  218 . Optionally, balloon  245  is guided along guide wire  247  to a correct position for expanding stent graft  216 . Optionally, balloon  245  is positioned so that, when expanded, vessel section  201  collapses under the compressive force of stent graft  216  on the vessel section. 
       FIG. 31  shows balloon  245  expanded inside stent graft  216 , causing vessel section  201  to collapse under the compressive force of the balloon-expanded stent. Optionally, vessel section  201  collapses into a relatively thin layer between inner wall  206  and balloon-expanded stent graft  216 . Optionally, balloon  245  may be deflated following expansion of stent graft  216  and removed along guide wire  247 . Optionally, guide wire  247  may be removed. 
       FIG. 32  shows stent graft  216  fully deployed. Optionally stent graft  216  fills a space occupied by vessel section  201  to inner wall  207  (except for the crushed vessel section  201  between the wall and the stent graft). Optionally, opening  231  is displaced to junction  239  interconnecting branch vessels  204  and blood vessel  202 . Optionally, suitable blood flow exists between blood vessel  202  and branch vessel  204  through opening  231 . Optionally, guide wire  232  may be removed from the side of blood vessel  102 . Optionally, guide wire  132  may be removed from the side of branch vessel  204 . 
       FIG. 33  shows an optional branch stent graft  249  inserted in branch vessel  204 . Optionally, branch stent graft  249  is advanced over guide wire  232  through stent graft  216 , through fenestration  231  and into branch section  204 . Optionally, branch stent graft  249  is expanded by unsheathing, balloon expansion or other stent expansion methods. Optionally, branch stent graft  249  is mounted over fenestration  231 . Optionally, branch stent graft  249  is inserted from a direction of branch vessel  204 . 
     The foregoing descriptions of exemplary implementations of the method are not intended to be limiting in any way, form or manner. It should be evident to an ordinary person skilled in the art that there are numerous other ways, form, or manner of implementing the method. These may include adding steps, deleting steps, skipping steps, and changing a sequence of steps. Furthermore, it should be evident to a person skilled in art that foregoing descriptions of insertion and removal of catheters and/or guide wires, and of expanding stents and stent grafts, are for exemplary purposes only, and that these may be varied, for example, according to established medical practice. 
     Reference is now made to  FIGS. 34-36  which schematically illustrate an exemplary branching scaffold  300  and a method of loss of structural rigidity in the scaffold, according to some embodiments of the present invention. Branching scaffold  300  includes a sheath  306 , a rod  308 , and wires  310  adapted to serve as struts and connected to the rod in a loop  312  (slip knot) at a distal end of the rod. Branching scaffold  300  including sheath  306 , rod  308 , wires  310 , and loop  312  may be similar to that shown in  FIGS. 1-17  at  100 ,  106 ,  108 ,  110 , and  112 . Branching scaffold  300  loses structural rigidity when rod  308  is pulled in a proximal direction  342 , loop  312  sliding out of the rod releasing wires  310 . Optionally, rod  308  and wires  310  can be retrieved into sheath  306 . 
     Reference is now made to  FIGS. 37-40  which schematically illustrate an exemplary branching scaffold  400  and a method of loss of structural rigidity in the scaffold, according to some embodiments of the present invention. Branching scaffold  400  includes a sheath  406 , a rod  408 , and wires  410  adapted to serve as struts and connected to the rod in a joint  412  at a distal end of the rod. Branching scaffold  400  including sheath  406 , rod  408 , and wires  410  may be similar to that shown in  FIGS. 1-17  at  100 ,  106 ,  108 , and  110  with an optional difference that branching scaffold  400  includes joint  412 . Branching scaffold  400  loses structural rigidity when rod  408  is pushed in a distal direction  443 , the rod pushing joint  412  in the distal direction causing wires  410  to break loose from the joint. Optionally, rod  408  and wires  410  can be retrieved into sheath  406 . 
     Reference is now made to  FIGS. 41-43  which schematically illustrate an exemplary branching scaffold  500  and a method of loss of structural rigidity in the scaffold, according to some embodiments of the present invention. Branching scaffold  500  includes a sheath  506 , a rod  508 , and wires  510  adapted to serve as struts and connected to the rod in a hook  512  at a distal end of the rod. Branching scaffold  500  including sheath  506 , rod  508 , and wires  510  may be similar to that shown in  FIGS. 1-17  at  100 ,  106 ,  108 , and  110 , with an optional difference that branching scaffold  500  includes hook  512 . Branching scaffold  500  loses structural rigidity when rod  508  is turned in a twisting direction  542  causing wires  510  to slide off hook  512 . Optionally, rod  508  and wires  510  can be retrieved into sheath  506 . 
     Reference is now made to  FIG. 44  which schematically illustrates an exemplary branching scaffold  600 , according to some embodiments of the present invention. Branching scaffold  600  includes a sheath  606 , a rod  608 , and wires  610  adapted to serve as struts and connected to the rod in a plurality of loops  612  (slip knot). Branching scaffold  600  including sheath  606 , rod  608 , wires  610 , and loops  612  may be similar to that shown in  FIGS. 1-17  at  100 ,  106 ,  108 ,  110 , and  112 , with an optional difference that branching scaffold  600  includes a plurality of loops. Optionally, rod  608  and wires  610  can be retrieved into sheath  606 . 
     Reference is now made to  FIG. 45  which schematically illustrates an exemplary branching scaffold  700 , according to some embodiments of the present invention. Branching scaffold  700  includes a sheath  706 , a rod  708 , wires  710  adapted to serve as struts and connected to the rod in a loop  712  (slip knot) at a distal end of the rod, and a connection point  711  for the wires at a proximal end of the wires. Branching scaffold  700  including sheath  706 , rod  708 , and wires  710 , and loops  712  may be similar to that shown in  FIGS. 1-17  at  100 ,  106 ,  108 ,  110 , and  112 , with an optional difference that branching scaffold  700  includes connection point  711 . Optionally, rod  708  and wires  710  can be retrieved into sheath  706 . 
     Reference is now made to  FIG. 46  which schematically illustrates a fenestration device  821 , according to some embodiments of the present invention. Fenestration device  821 , includes a catheter  820  and a balloon  825  adapted to bend a catheter tip  828  when inflated. Fenestration device  821  including catheter  820  with catheter tip  828  and balloon  825  may be similar to that shown in  FIGS. 1-17  at  121 ,  120 ,  128  and  125  with an optional difference that balloon  825  is a single balloon. 
     Reference is now made to  FIG. 47  which schematically illustrates a fenestration device  921 , according to some embodiments of the present invention. Fenestration device  921  includes a catheter  920 , and a small balloon  926  and a large balloon  924  adapted to bend a catheter tip  928  when inflated. Fenestration device  921  including catheter  920  with catheter tip  928  and balloons  824  and  826  may be similar to that shown in  FIGS. 1-17  at  121 ,  120 ,  128 ,  124  and  126 . 
     Reference is now made to  FIG. 48  which schematically illustrates a fenestration device  1021 , according to some embodiments of the present invention. Fenestration device  1021 , includes a catheter  1020  with one or more wires  1027  running along one aspect of its wall and extending to a catheter tip  1028 . Optionally, catheter tip  1028  is bent to a side when wires  1027  are pushed forward in a distal direction. Optionally, catheter tip  1028  is bent when wire  1027  is pulled in a proximal direction. Fenestration device  1021  including catheter  1020  with catheter tip  1028  may be similar to that shown in  FIGS. 1-17  at  121 ,  120 , and  128  with an optional difference that branching scaffold  1000  includes wire  1027  for bending the catheter tip. 
     The terms “comprises”, “comprising”, “includes”, “including”, “having” and their conjugates mean “including but not limited to”. This term encompasses the terms “consisting of” and “consisting essentially of”. 
     The phrase “consisting essentially of” means that the composition or method may include additional ingredients and/or steps, but only if the additional ingredients and/or steps do not materially alter the basic and novel characteristics of the claimed composition or method. 
     As used herein, the singular form “a”, an and “the” include plural references unless the context clearly dictates otherwise. For example, the term “a compound” or “at least one compound” may include a plurality of compounds, including mixtures thereof. 
     The word “exemplary” is used herein to mean “serving as an example, instance or illustration”. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments. 
     The word “optionally” is used herein to mean “is provided in some embodiments and not provided in other embodiments”. Any particular embodiment of the invention may include a plurality of “optional” features unless such features conflict. 
     Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range. 
     Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging/ranges between” a first indicate number and a second indicate number and “ranging/ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween. 
     As used herein the term “method” refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts. 
     As used herein, the term “treating” includes abrogating, substantially inhibiting, slowing or reversing the progression of a condition, substantially ameliorating clinical or aesthetical symptoms of a condition or substantially preventing the appearance of clinical or aesthetical symptoms of a condition. 
     It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. 
     Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims. 
     All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.