Abstract: A cannula has a longitudinal base member having a first clamping end and a longitudinal arm member pivotally attached to the longitudinal base member and having a second clamping end, the cannula being in a closed position when the first and second clamping ends are brought together. A first clamp member is located at the first clamping end and has a first passage. A second clamp member is rotatably attached to the arm member at the second clamping end and has a second passage. The first and second passages form a combined passage when the clamp is in the closed position. The cannula may have a first locking member positioned on the arm member and a second locking member positioned on the base member. The first and second locking members interact with each other to lock the cannula in the closed position.

Abstract: A surgical clip for a clip applier to ligate vessels. The clip contains two opposing external and internal legs connected in parallel by two external apex and one internal apex to form a Y-shape configuration. As a vessel is ligated and compressed between the two external legs, the vessel attempting to expand from its compressed position, applies outwardly lateral forces to the external legs causing them to rotate outwardly. In response, the two opposing internal legs rotate in an opposing directions to the external legs rotations to maintain the position of the clip over the compressed tubular vessel.

Abstract: A surgical clip for occluding a vein, artery or other body passageway 2 comprises a base portion 3, a pair of resilient limbs 4a, 4b configured to extend generally laterally outwardly from the base portion and each having a free end disposed forward of the base portion, and a reaction portion 9a/b mounted to the base portion 3, the reaction portion defining a generally forwardly directed reaction surface 10 disposed between the base portion 3 and the free ends of the limbs 4a, 4b, the limbs (4a, 4b) being movable under a resilient restoring force from a first, open, condition, in which a gap is provided between the limbs and the reaction portion for receiving the body passageway into the clip, to a second, closed, condition, in which the limbs cooperate with the reaction portion to grip the body passageway to occlude the same.

Abstract: A bypass device for influencing blood pressure, including an implant with a volumetric chamber, having a connector or connecting means for connecting the volumetric chamber to a natural cardiovascular system, and having an adaptor or adaptation means, by which a change in volume of a volume of the volumetric chamber is enabled or effected upon a pressure change in the cardiovascular system or in the volumetric chamber. According to this invention, a change in volume in a lower pressure range between 50 mmHg and a pressure threshold value amounting to at least 100 mmHg amounts to at most 10 cm3, and in an upper pressure range between the pressure threshold value and 150 mmHg amounts to at least 10 cm3. With the device according to this invention, high blood pressure can be reduced in a carefully directed way.

Abstract: Methods and devices for blocking orifices and occluding cavities within a patient are provided. The device in one variation comprises first and second tubular members attached to a collapsible sealing element. The device can be placed through an orifice and the collapsible sealing element can be collapsed to seal the orifice. An embolic may be introduced distal to the sealing element to occlude a cavity. The device may incorporate a locking mechanism which can be engaged to lock the sealing element into the collapsed position. The device may incorporate a valve to prevent flow through the tubular members, for example to prevent egress of the embolic from a cavity. The device can be detached to provide a permanent seal of the orifice, and can retain the embolic within the cavity. The device may be used in conjunction with a stent or other retention device to assist the sealing element in maintaining the seal.

Abstract: An aneurysm closure clip along with a system and method for use by a physician in delivering the closure clip into the vasculature of a patient is disclosed. The closure clip delivery system comprises a delivery tube in the form of a catheter, a guide wire, and a detachable closure clip. The closure clip includes a proximal side and a distal side. The distal side comprises at least two winged elements that interact with the wall of the body vessel to hold the clip in place after delivery. The proximal side includes a seal element and a guide bar. The guide bar is in communication with the guide wire during delivery. The seal element forms a barrier between the aneurysm and the rest of the body vessel, thereby, reducing any pressure exerted on the aneurysm. The seal element and optionally the winged elements include a material layer comprised of bioremodelable material, such as an extracellular matrix material (ECM).

Abstract: Percutaneous medical procedures are provided, which use endovascular instruments to install mechanical closures for closing vessels, such as veins. The mechanical closures can be one or more sutures that are anchored to the vessel walls and then cinched to closed the vessel. The mechanical closures can also be resilient clips or stents that are expanded within the vessel to pierce the vessel walls, and are then contracted to pull the vessel closed. Various techniques for installing the mechanical closures are also described.

Abstract: A closing assembly for a clamping device having first and second jaw members includes a closing mechanism connected between the first and second jaw members, the jaws extending distally from the closing mechanism; and a member for applying a separating force to the first and second jaw members proximally of the closing mechanism, whereby the first and second jaw members can be maintained substantially parallel during closing. The clamp has a very strong clamping force.

Abstract: A device for pinching an opening in a vessel wall, comprising an introducer sheath, a lumen having a distal opening and a bleed hole; an anchoring having a cylindrical shape in a first constrained state and a flared shape in a second unconstrained state; a pincher member slidably disposed between the anchoring member and the introducer sheath comprising at its distal end a plurality of elongate pincher arms, each of the plurality of elongate pincher arms having a free distal end such that when the pincher member distal end is unconstrained, the free distal ends of the elongate pincher arms are biased to expand radially; and an interior support member slidably disposed in the anchoring member comprising a plurality of elongate support legs, each having a free distal end such that when the distal end of the interior support member is unconstrained, the free distal ends curve outwardly.

Abstract: The invention relates to an implant (1) to be used for the occlusion of aneurysms in the region of vessel branches, in particular bifurcation aneurysms (A), with a mesh structure (3, 4), said implant comprising—from proximal to distal—sections (a) to (d) where (a) is a section tapering down proximally in which the mesh structure is brought together to form one or several coupling elements (10), (b) is a fixing section by means of which the implant can be supported on the to wall of a vessel, (c) is a permeable section for the region of the vessel bifurcation, and (d) is a distal section in which the implant is expanded in comparison to section (b) and which is intended for placement into the aneurysm (A), wherein a separation zone (T1, T2) being arranged in the area of sections (c) or (d).

Abstract: A ligation device is disclosed that is capable of containing a fluid, e.g., a biomechanical medium or an antimicrobial solution. The ligation device comprises an upper clip and a lower clip, each having a locking feature that enables the upper clip and the lower clip to be movably attached to each other.

Abstract: A method of applying a surgical clip, wherein the clip has a rigid portion with a pair of opposed first and second leg members having proximal and distal ends and a knee portion formed therebetween. The clip also has an apex with opposed ends joining the proximal ends of the first and second leg members, and a compliant portion formed on an inner surface of at least one of the first and second leg members. The method includes the step of placing the opposed first and second leg members around a tissue to be ligated, and deforming the opposed first and second leg members towards each other. The method further comprises releasing the first and second leg members to cause a separation of the first and second leg members, wherein the separation is less than the total of thickness of the compliant portion and the thickness of the tissue within the first and second leg members.

Abstract: Atrial appendage occlusion systems and methods of using the same. In an exemplary embodiment of a system for occluding an atrial appendage of a heart, the system comprises a first device and a second device, wherein the first device comprises a first tube sized and shaped for insertion into the heart and a balloon coupled to the first tube, wherein the balloon is capable of inflation and deflation, wherein the second device comprises a second tube sized and shaped for insertion into a pericardial space surrounding the heart, the second tube comprising a lumen extending at least partially from a second tube distal end to a second tube proximal end and a loop sized and shaped to fit at least partially within the lumen of the second tube, wherein the loop is capable of protraction from the second tube distal end, and wherein the loop of the second device is configured for placement around the atrial appendage and to be secured around the atrial appendage.

Abstract: An aneurysm closure device having a pair of retention clips joined together. Each of the clips has an aneurysm anchor joined to a root-vessel anchor, and is made of material having a resilient installed state, in which the aneurysm anchor and the root-vessel anchor are urged together, thereby squeezing and being retained by interposed tissue. Also, an aneurysm seal, to seal an aneurysm, bridges the clips, causing the aneurysm to atrophy.

Abstract: An apparatus for regulating the functioning of a patient's organ or duct includes an elongated member having a first end and a second end. A fastener is disposed on the first end of the elongated member. The fastener is configured to engage the second end of the elongated member so that the elongated member forms a loop around the organ or duct. A tension element is disposed for movement within the elongated member. A symmetrical drive system including a drive element associated with and engaging the tension element for causing the tension element to control the tension applied by the elongated member against a patient's body organ or duct is further provided. In accordance with an alternate embodiment an apparatus for regulating the functioning of a patient's organ or duct including an elongated member having a first end and a second end. A fastener is disposed on the first end of the elongated member.

Abstract: This document relates to methods and materials involved in fastening or constricting. For example, devices (e.g., adjustable vascular pedicle constricting devices) configured to allow a user (e.g., a surgeon) to apply a band element at least partially around a desired structure (e.g., tissue such as a vascular pedicle) in a manner that allows the degree of constriction to be adjustable are provided.

Abstract: Method and system is disclosed for using a sensory vascular clip. The sensory vascular clip is configured to open and close and includes first and second clamping portions, each having a pinching surface, a coil spring for pressing said pinching surfaces together when the clip is in a closed position, the coil spring including at least one coil loop, a first and second branch resiliently connected to the coil spring, wherein the first and the second branch cross over each other at a crossing point, a transmitter, and a sensor configured to detect signals from the transmitter.

Abstract: A surgical clip forming apparatus includes an unformed surgical clip having a head section including an upper portion and a lower portion separated from each other to define a first space therebetween in a first configuration, a left leg section including a proximal end and a distal end and a right leg section including a proximal end and a distal end. The surgical clip forming apparatus includes an anvil configured to engage the head section of the surgical clip and a pair of forming pins positioned adjacent the proximal ends of the left and right legs for securing the head section of the unformed surgical clip against the anvil. When a force is applied to the anvil, the upper portion compresses toward the lower portion. The unformed surgical clip transforms into a “T-shaped” clip or a formed clip in a second configuration, after the force has been applied to the anvil.

Abstract: An environmentally sensitive hydrogel material swells or collapses in response to a parameter such as pH level associated with consumption of food by a patient. This swelling or collapsing is harnessed to treat morbid obesity or some other condition of the patient. The swelling or collapsing of the hydrogel may be used to tighten a gastric band or gastric valve when the patient starts eating; then loosen the band or valve when the patient is between meals. The swelling or collapsing of the hydrogel may also be used to increase the size of a space occupying device in the patient's stomach when the patient starts eating; then decrease the size of the space occupying device when the patient is between meals. The swelling or collapsing of the hydrogel may also be used to selectively restrict the absorption of nutrients within a patient's gastrointestinal tract, such as in the duodenum.

Abstract: A device for occluding a blood vessel, comprises a blunt dissection needle and a first occlusion clip releasably mounted to a distal end of the blunt dissection needle, the first occlusion clip being biased to assume a clamped configuration in combination with a retaining element which, in a first configuration, retains the first occlusion clip in an insertion position against an outer surface of the blunt dissection needle and, in a second configuration, releases the first occlusion clip to assume the clamped configuration.

Abstract: Vessel occlusion method including the steps of positioning a coil anchor in a large diameter blood vessel, wherein the coil anchor includes a radially expandable sidewall, a proximal opening dimensioned to receive an embolic coil, a distal opening, and the coil anchor further comprising at least one coil retaining element configured to retain an embolic coil within the blood vessel. The vessel occlusion method further including the steps of expanding the coil anchor within the blood vessel; and delivering at least one embolic coil into the blood vessel, wherein the retaining element prevents the at least one embolic coil from migrating downstream of the coil anchor.

Abstract: Stimulation of a stretch receptor response to the cardiac cycle is enhanced by constraining a region of a blood vessel wall upstream and/or downstream of a baroreceptor. The constraint may be external or internal and will typically be effected using a circumferential restraint placed over or within the blood vessel.

Abstract: The present disclosure provides a clip for application to a renal artery to induce hypertension. The clip includes a pair of arms between which is formed a slot. The arms are supported by a base portion. The clip may include various curved surfaces to prevent snagging and damage when applied to the renal artery. Also, the clip is preferably constructed of stock titanium rods to have a unitary and stiff construction. Further, the clip includes a pair of cylindrical suture openings that retain a suture passed therethrough after the clip is applied to the renal artery. The suture firmly retains the clip on the artery.

Abstract: An extra-luminal ring (1200) includes a structural member (1202), which assumes a first elongate hollow shape (1206) when in a relaxed state; when deformed to a planar state (1208), generally defines a planar shape (1209) having two first sides (1220A, 1220B) parallel to each other, and two second sides (1222A, 1222B) parallel to each other; and when in the relaxed state, is configured such that the two first sides (1220A, 1220B) are generally straight and parallel with each other, and the two second sides (1222A, 1222B) are curved at least partially around a first longitudinal axis (1230) defined by the first elongate hollow shape (1206).

Abstract: Surgical clips and devices for ligating tissue, as well as methods related to the same, are generally provided. In one exemplary embodiment a surgical clip includes a pair of opposed first and second leg members and a knee portion formed between the leg members' proximal and distal ends. The leg members can include at least one tissue-grasping element formed on respective inner surfaces, and at least one raised area located on a portion of respective generally planer outer surfaces. The clip can also include an apex having opposed ends that join the proximal ends of the first and second leg members and at least one notch formed on an inner surface of the apex. The raised area of the leg members can be disposed distal to the apex and proximal to the knee portion. Other embodiments of clips and methods for ligating tissue are also provided.

Abstract: An aneurysm clip includes a compression spring having a compression axis, a first end, and a second end. A first force receiving surface is coupled to the first end of the spring, and a second force receiving surface is coupled to the second end of the spring. A first arm coupled to the first force receiving surface is approximately parallel to the spring's compression axis. A second arm coupled to the second force receiving surface is approximately parallel to the spring's compression axis. A first clamping leg coupled to the first arm extends approximately perpendicular therefrom, and a second clamping leg coupled to the second arm extends approximately perpendicular therefrom. The first and second clamping legs oppose one another and are biased into contact with one another by the spring.

Abstract: Medical devices and related methods for closing a perforation in a bodily wall The medical device generally includes a suture having opposing first and second ends and a set of visceral anchors. Each visceral anchor includes a crossbar having opposing ends and a suture slidably attached thereto. Each visceral anchor is passed through the bodily wall adjacent the periphery of the perforation. The ends of the suture are tensioned to reduce the distance between the visceral anchors and compress the bodily wall around the perforation. The ends of the suture are secured to maintain the compression of the bodily wall and close the perforation.

Abstract: The present invention relates to vascular clip made of biocompatible, non-metallic material that minimizes artifacts and obscuration of a diagnostic image developed using modalities such as CATSCAN, and MRI. The vascular clip is dimensionally comparable to metal clips, while maintaining sufficient clamping force to stop the flow of blood from an aneurysm, a subarachnoid hemorrhage or bleeding on the brain.

Abstract: A surgical retractor including a slab-shaped member having a first edge and a second opposing edge, wherein a deformable elongate member is provided affixed to said first edge, said elongate member comprising an external wall defining an internal chamber, wherein the external wall is configured to be compressible and moldable to a surface, in particular, a human tissue surface within a surgical incision. A curved flexural handle may be provided attached to the second edge.

Abstract: A surgical clamp in certain embodiments may be configured to operate with a surgical installation tool. The clamp may have two elongated members with a bight portion that joins the two elongated members at a proximal end of the clamp and that may bias the two elongated members in an open position at a distal end. The bight portion may have one or more engagement features, such as a slotted aperture or other engagement or coupling feature. A clasp mechanism at the distal end of the clamp may have a male or first component disposed on or adjacent one of the two elongated members and a female or second component disposed on or adjacent the other of the two elongated members at the distal end of the clamp. The installation tool may include an elongated member with a proximal end and a distal end that has an engagement feature to engage the clamp, such as at the bight portion.

Abstract: Apparatus and methods are provided for thermally and/or mechanically treating tissue, such as valvular structures, to reconfigure or shrink the tissue in a controlled manner. Mechanical clips are implanted over the leaflets of a valve, e.g., in the heart, either alone or after thermal treatment to cause the valve to close more tightly. The clips are delivered by a catheter and may be configured to traverse directly over the valve itself or to lie partially over the periphery of the valve to prevent obstruction of the valve channel. The clips can be coated with drugs or a radiopaque coating. Alternatively, individual anchors with a tensioning element, like a suture, may be used to approximate the valves towards each other. The catheter can also incorporate sensors or energy delivery devices, e.g., transducers, on its distal end.

Abstract: An implantable aneurysm clip including a first arm and an opposed second arm. The first and second arms having corresponding opposed first and second clamping surfaces facing each other, and the first and second arms are movable relative to each other. The first and second clamping surfaces are shiftable between a first, preselected, open resting position in which the first and second clamping surfaces are separated by a first distance and a second open position wherein the first and second clamping surfaces are separated by a second distance. The second distance is greater than the first distance and the first and second clamping surfaces are biased toward the first position by a biasing force.

Abstract: A system for performing a medical operation includes an end effector having first and second arms, each extending from a distal end to a proximal end, the proximal ends being connected to one another, the end effector being movable between a closed configuration wherein the first and second arms are separated from one another by a first distance and an open configuration wherein the first and second arms are separated from one another by a second distance greater than the first distance, a distance between the first and second arms being substantially constant from the proximal ends to the distal ends, wherein the end effector is biased to the open configuration. A first plate element extends from a first surface configured to engage a first wall of the first arm to a second surface configured to contact target tissue in an operative configuration.

Abstract: A vascular closure system includes a vessel closure device with an electrically conductive component. The vessel closure device is configured to be advanced percutaneously to an opening in a blood vessel and to mechanically draw together sides of the opening or occlude the opening. A power source in electrical contact with the vessel closure device provides power to the vessel closure device to thereby heat tissue in an area near the opening to facilitate the closure or healing of the opening. The vessel closure device may be configured to be advanced to the opening over a tubular medical device. The vessel closure device may include a superelastic or shape memory element. The vessel closure device may be in contact with two conductors from the power source and may be configured to heat tissue via direct resistive element heating. Alternatively, one conductor may be connected to the vessel closure device and a second conductor may be connected to a ground pad on the patient.

Abstract: A method for occluding a body vessel in a patient to block or reduce blood flow therethrough includes puncturing a blood vessel wall at a proximal vessel entry site with a hollow needle and extending the needle through the proximal entry site into the vessel lumen. The needle is extended through the vessel lumen and extended through the vessel wall at a distal vessel exit site into the extravascular space surrounding the distal vessel exit site. An expandable biocompatible material, such as expandable extracellular matrix (ECM) material, is then ejected though the distal end of the needle into the extravascular space. Then, while continuing to eject the expandable biocompatible plug material, the distal end of the needle is retracted back through the distal vessel exit site into the vessel lumen, such that the plug material continuously extends between the extravascular space surrounding the distal vessel exit site into the vessel lumen.

Abstract: A ligature delivery device includes a control member, an elongated shaft, and an end effector attached to the distal end of the elongated shaft. An activation mechanism provides an user-operable connection between the control member and the end effector. In several embodiments, the end effector includes a reverse grasping mechanism. Several embodiments of ligature devices are adapted to be deployed endoscopically and/or translumenally using the reverse-grasping delivery device.

Abstract: An arterio-venous graft (16) is provided with a constriction device (20) near its arterial end. The constriction device (20) is used to reduce the flow through the AV graft under normal conditions and to relieve the constriction when high flow through the AV graft is required, such as for vascular access for hemodialysis.

Abstract: Processes for the correction or treatment of a vascular defect or vascularized tumor are provided including introducing an embolus formed of an adhesive to occlude an area of a defect or to prevent blood flow to a tumor. The inventive processes provide simple methods for long-term correction of vascular defects.

Abstract: A surgical clip is provided having two clip arms and a resiliently flexible element via which the two clip arms are connected to each other. The two clip arms each have a first free end, these first free ends being held parallel to and in contact with each other with a predetermined closing force by the resiliently flexible element when the clip is in a rest position. The clip arms are held at a second end opposite the free end on the resiliently flexible element. The clip arms have between their first and second ends sections configured to cross each other. The clip arms further have stop elements configured to complement each other. The stop elements are adapted to be brought in mutual contact when the clip is transferred from the rest position to an application position in which the free ends are spaced apart from each other.

Abstract: In order to provide a surgical clip device with which the closure of vessels is successfully achieved even more safely, particularly in neurosurgery, it is proposed that the surgical clip device be provided with at least two electrically conductive clip parts that are electrically isolated from each other (by an element) and are arranged at a predetermined distance opposite each other.

Abstract: A surgical loop for constricting or ligating, partially or fully, an anatomic conduit during a surgical intervention. The surgical loop includes an elastomeric tubular body, a curved needle that is attached to one free end of the tubular body to facilitate its insertion through a body tissue containing an anatomic conduit, and a pledget which is frictionally engaged and positionable along the length of the tubular body. The pledget is frictionally engaged with a first portion of the tubular body through a closed-perimeter opening. A second portion of the tubular body is subsequently frictionally engaged or restrained with the pledget through a slot. The pledget is configured with a bias structure which maintains the slot in a biased-closed configuration to engage and restrain the second portion of tubular body.

Abstract: A hemostatic clipping device is provided. The device includes first and second elongate arms, each arm comprising distal and proximal end portions, the arms being connected to allow relative motion between the first and second arms, the distal portion of each of the first and second arms further comprising a track blindly defined from a distal end of each arm toward the proximal portion of each arm. A clip is slidably disposed between the opposed distal portions of each of the first and second arms, the clip comprising first and second fingers each with distal and proximal portions, the proximal portions of the first and second fingers being fixed together to bias the distal portions of the first and second fingers toward each other, the first and second fingers each further comprising a pin extending radially outward from the distal end portion thereof.

Abstract: The invention provides a method and system for transiently occluding a vein that is downstream of an organ such as the brain, where the occlusion increases blood pressure within the vein, and where the increased pressure stimulates a reflex that reduces entry of emboli into that organ.

Abstract: An apparatus for deployment of a hemostatic clip includes a clip assembly releasably coupled to a distal portion of a shaft, wherein the clip assembly includes a capsule releasably coupled to the shaft, clip arms slidably received within the capsule and cooperating with the capsule to provide a first user feedback indicating a decision configuration of the clip assembly and a yoke slidably received within the capsule, the yoke including proximal and distal portions releasably and rotatably connected to one another via a first control wire, a distal end of the distal portion being connected to proximal ends of the clip arms. A second control wire extends from the handle assembly and is coupled to a proximal end of the second portion to move the clip assembly between open and closed configurations.

Abstract: An endovascular device for occluding a vascular aneurysm is disclosed. The device includes a polymeric shell member that, in one embodiment, may be constructed from a bioactive and biocompatible polyurethane-diol-glycosaminoglycan copolymer, and a biocompatible metallic frame member. The copolymer is sufficiently flexible and strong for endovascular delivery into a vascular aneurysm and for use as a polymeric shell for receiving the biocompatible metallic frame member. The biometallic frame member may include one or more components constructed from a NiTi alloy.

Abstract: An endovascular device for occluding a vascular aneurysm is disclosed. The device includes a polymeric shell member that, in one embodiment, may be constructed from a bioactive and biocompatible polyurethane-diol-glycosaminoglycan copolymer, and a liquid embolic agent. The copolymer is sufficiently flexible and strong for endovascular delivery into a vascular aneurysm and for use as a polymeric shell for receiving the liquid embolic agent. Upon activation inside of the polymeric shell within the aneurysm, the liquid embolic agent solidifies enabling biological isolation of the aneurysm and improved patient outcomes.

Abstract: A method for inducing weight loss in a patient, the method comprising: intentionally occluding a blood vessel so as to create hypoperfusion in a gastrointestinal organ serviced by the blood vessel, whereby to interfere with normal gastrointestinal function and thereby induce weight loss in a patient.

Abstract: A vascular clamp, has an operating mechanism, and an actuating tool. The vascular clamp is grasped using a detachable operating mechanism, wherein an actuating tool that can be slid in and out is able to open and close the jaws of the grasped vascular clamp. The vascular clamp includes a coupling arrangement and a continuously adjustable adjustment mechanism for this purpose. In order to grasp the vascular clamp, the operating mechanism includes a gripping mechanism and is equipped with a locking mechanism, which are used to create a detachable connection between the vascular clamp and the operating mechanism. For stepless opening and closing, the actuating tool engages in the adjustment mechanism of the vascular clamp and opens and closes the jaws of the vascular clamp by corresponding rotation of the actuating tool.

Abstract: Implantable devices for placement at a cavity or opening such as an aneurysm are disclosed. The implantable devices, in a deployed condition, have a generally inverted U-shaped profile with a curved or angled framework support structure sized and configured for placement in proximity to tissue surrounding the opening and anchoring legs extending proximally from the framework structure sized and configured to contact the wall of a neighboring lumen at opposed locations. Occlusive and semi-occlusive membranes may be associated with the framework support structure and deployed over the opening to provide exclusion of the opening and flow diversion. Proximal anchoring segments providing additional lumen wall surface area contact for the implantable device following deployment may be incorporated.

Abstract: In a compression sleeve for the local enclosure of a blood vessel or vein area comprising a retaining structure of a biocompatible material, the retaining structure is a flexible mat consisting of a mesh or net-like structure provided with an arrangement holding the retaining structure in a vein enclosing position.