Patent Publication Number: US-2021177420-A1

Title: Implantable flow connector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional Patent Application which claims the benefit of U.S. patent application Ser. No. 15/017,620, filed Feb. 6, 2016 and is a continuation of U.S. application Ser. No. 13/792,012, filed Mar. 9, 2013 which claims benefits to U.S. Provisional application No. 61/624,375, filed Apr. 15, 2012 and is a continuation in part of U.S. application Ser. No. 13/716,179, filed Dec. 16, 2012 now U.S. Pat. No. 8,961,446, which is a continuation of U.S. application Ser. No. 12/185,811, filed Aug. 4, 2008, now U.S. Pat. No. 8,366,651, which claims the benefit of U.S. Provisional Application No. 60/953,570, filed Aug. 2, 2007. The entire contents of each of these applications are hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     Field of the Invention 
     The present invention relates generally to implantable medical devices and, more particularly, to implantable flow connectors. 
     Related Art 
     The mammalian body has numerous tissue-enclosed body spaces. For example, body conduits such as blood vessels, lymph and tear ducts, bowels, urethra, etc., have a lumen through which fluid is carried to facilitate circulation, excretion or other fluid transfer function. Tissue-enclosed body spaces also include body reservoirs such as the stomach, bladder, gall bladder, lymph nodes, etc., which temporarily or permanently retain fluid. 
     It is often necessary or desirable to directly or indirectly connect body spaces to one another, to other areas in the body, or to an external or implantable medical device such as a sensor, pump, drug delivery system, or other permanently or temporarily implanted therapeutic device. For example, when vessels are damaged, severed or occluded due to physiological conditions, surgical intervention, or disease, certain sections of those vessels are typically bypassed to allow for the free and continuous flow of fluids. For example, an anastomosis is commonly performed for the purpose of connecting different blood vessels together to optimize or redirect blood flow around a damaged or occluded portion of a vessel or to redirect arterial flow into the venous system for enabling dialysis access. 
     In the context of the peripheral vascular and/or the cardiovascular system, atherosclerosis may cause partial or complete occlusion of an arterial vessel. This may result in restricted blood flow which may compromise perfusion to the tissue served by the blood flow. In the case of an occluded coronary vessel, for example, an area of the heart&#39;s myocardium would be compromised, which may lead to a myocardial infarction or other ischemic heart syndrome such as congestive heart failure. In the case of peripheral vascular atherosclerotic disease, occluded vessels lead to ischemic syndromes such as threatened limbs, stroke and other morbidities. Many cases, such a blockage or restriction in the blood flow leading to the heart or peripheral vessels, may be treated by a surgical procedure known as an artery bypass graft procedure. 
     A bypass procedure involves establishing an alternate blood supply path to bypass a diseased section of a diseased or compromised artery. In the bypass procedure, a surgeon typically dissects one end of a source or “pedicled” artery (such as the internal mammary artery in the case of coronary artery bypass), or a free vessel segment (typically the saphenous vein in the leg), to use as a graft conduit to bypass the obstruction in the affected artery to restore normal blood flow. The graft vessel is connected to the obstructed vessel by means of an anastomosis procedure wherein an opening in the graft vessel is sutured to the obstructed vessel at an arteriotomy site made within the obstructed vessel. There are other indications for vessel anastomoses including revascularizing diseased arteries by creating a side-to side anastomosis between the distal end of the artery and an adjacent vein, thereby allowing the portion of the vein distal the occlusion to become “arterialized.” Another indication includes arterial revascularization by “arterializing” a vein through creation of a conduit downstream of the occlusive disease. 
     The creation of an arteriovenous (AV) fistula is another instance where two body conduits are joined together and involves surgically joining an artery to a vein. AV fistulas are formed for a variety of reasons, one being to provide vascular access for hemodialysis patients. In such an application, the most common site for creation of the AV fistula is the upper extremity, though the lower extremity may also be used. Various surgical techniques and methods may be employed to create the AV fistula. Another indication for creation of an AV fistula is the connection of major vessels such as the aorta and the vena cava in patients with chronic obstruction pulmonary disease (COPD). 
     The patency of an anastomosis contributes to a successful bypass or AV fistula, both by acute and long-term evaluation. Patency may be compromised due to technical, biomechanical or pathophysiological causes. Among the technical and biomechanical causes for compromised patency are poorly achieved anastomoses due to, for example, poor technique, trauma, thrombosis, intimal hyperplasia or adverse biological responses to the anastomosis. Improperly anastomosed vessels may lead to leakage, create thrombus and/or lead to further stenosis at the communication site, possibly requiring re-operation or further intervention. As such, forming an anastomosis is a critical procedure in bypass or AV fistula surgery, requiring precision and accuracy on the part of the surgeon. 
     A common traditional approach for forming an anastomosis is to suture together natural or artificial openings in the vessels. To do so, according to one approach, a surgeon delicately sews the vessels together being careful not to suture too tightly so as to tear the delicate tissue, nor to suture too loosely so as to permit leakage of fluid from the anastomosis, In addition to creating a surgical field in which it is difficult to see, leakage of fluid from the anastomosis can cause serious acute or chronic complications, which may be fatal. In addition to the inherent inconsistencies in suture tightness, incision length, placement of the suture, stitch size, and reproducibility, suturing an anastomosis can be very time consuming. This difficulty is compounded by the relatively small dimensions of the vessels involved or the diseased state of the vessel when creating an AV fistula. 
     SUMMARY 
     In accordance with one aspect of the present invention, an implantable flow connector for fluidly coupling a source tissue-enclosed body space with a destination conduit is provided. The flow connector includes a conduit having a lumen terminating at a first orifice at a first end of the conduit implantable in the source body space through an opening formed in a tissue wall of the source body space, and a second end of the conduit having a second orifice implantable in the destination conduit through an opening at an end of the destination conduit, and a circumferential flange radially extending from the conduit, proximate the conduit first end, configured to be implanted in the source body space adjacent an opening in the tissue wall of the source body space such that the conduit extends through the opening. 
     In accordance with another aspect of the present invention, a system for coupling a first space within the body of a patient with a second space within the body of the patient is provided. The system comprises a retention device and a flow connector. The flow connector is insertable into the first and second spaces within the body and has a conduit having a lumen having a first orifice at a first portion of the conduit and a second orifice at a second portion of the conduit, the conduit providing communication between the first and second spaces within the body. The retention device retains the conduit with respect to the first space within the body and is engageable with the first space within the body. 
     Preferably, the retention device is movable to a reduced profile position for insertion. 
     In some embodiments, the retention device includes a first set of engaging elements extending therefrom configured to penetrate a wall of the first space within the body and/or a second set of engaging elements extending therefrom configured to penetrate a wall of the second space within the body. 
     In some embodiments, the flow connector is positioned within an opening in the retention device and in a placement position the retention device is positioned between an outer surface of the flow connector and an inner surface of the second space within the body. The flow connector can apply an outwardly directed radial force to the retention device. In other embodiments, the retention device is positioned about an outer surface of the second space within the body and in a placement position the second body space is positioned between an outer surface of the flow connector and an inner surface of the retention device. 
     The flow connector preferably includes a flange extending radially outwardly and insertable into the first body space. The flange can include first and second lateral sections and first and second longitudinal sections, the first and second lateral sections configured to cooperate with walls of the first space such that the flange sealingly conforms to an inner surface of a tissue wall adjacent an opening in the first space. The first and second longitudinal sections can extend further radially from the conduit than the first and second lateral sections. 
     In some embodiments, the retention device comprises an inner component and an outer component wherein at least one of the inner and outer components is relatively slidable with respect to the other component. The outer component can include a compression member to provide a proximal force on the inner body member. The inner body member can be movable from a first configuration to a second spread configuration to provide an axial opening therein for side receipt of the second body space. 
     In some embodiments, the retention device includes a proximal component and a distal component wherein the proximal component is engageable with the first body space and the distal component is engageable with the second body space, the proximal and distal components interlocking. 
     The various retention devices disclosed herein can include a plurality of struts and the plurality of struts can in some embodiments form closed geometric shapes. 
     In accordance with another aspect of the present invention, a system for coupling a first space within the body of a patient with a second space within the body of the patient is provided comprising a flow connector having a conduit having a lumen having a first orifice at a first portion of the conduit and a second orifice at a second portion of the conduit, the conduit configured to be implanted into the second space within the body to provide communication between the first and second spaces within the body. The system of this aspect also includes a retention device having an opening to receive the conduit, the retention device having a first set of engaging members to engage the first space within the body and a second set of engaging members to engage the second space within the body, the retention device maintaining the conduit in position with respect to at least of the first and second body spaces. The first set of engaging members can comprise a first set of penetrating elements with penetrating tips protruding radially therefrom to penetrate a wall of the first space within the body and the second set of engaging elements can comprise penetrating elements configured to pierce a wall of the second space within the body when the second space is positioned over the retention device. 
     In some embodiments, in a placement position the retention device is disposed between an outer surface of the conduit and an inner wall of the second space within the body. 
     The retention device is preferably movable to a reduced profile configuration for insertion. 
     In some embodiments, the retention device comprises first and second components movable from a spaced position to an engaged position, the first set of engaging members extending from the first component and the second set of engaging elements extending from the second component. 
     In some embodiments, the first set of engaging members extends toward a proximal end of the retention device. 
     In some embodiments, the flow connector includes a flange extending radially from the first portion of the conduit and is configured to be implanted in the first space within the body 
     in accordance with another aspect of the present invention, a system is provided for coupling a first space within the body of a patient with a second space within the body of the patient comprising a flow connector insertable into the first and second spaces within the body, the flow connector having a conduit having a lumen having a first orifice at a first portion of the conduit and a second orifice at a second portion of the conduit, the conduit providing communication between the first and second spaces within the body. The system of this aspect includes a retention device for retaining the conduit within the second space within the body, the retention device including a plurality of struts and having an axial opening to receive and engage the flow connector 
     Preferably, the retention device is movable to a reduced profile position for insertion. 
     In some embodiments, the retention device is movable to an expanded open position to receive the flow connector therein. 
     In accordance with another aspect of the present invention, a system for fluidly coupling a first space within the body of a patient with a second space within the body of the patient is provided comprising a first device, a second device engageable with the first device, and a flow connector having a conduit having a lumen having a first orifice at a first portion of the conduit and a second orifice at a second portion of the conduit, the conduit configured to be implanted into the second space within the body to provide communication between the first and second spaces within the body. The first device engages with at least one of the flow connector and the first space within the body and the second device engages with at least one of the flow connector and second space within the body. 
     In some embodiments, a first plurality of engaging elements extend from the first device to engage a wall of the first body space and a second plurality of engaging elements extend from the second device to engage a wall of the second body space. 
     In some embodiments, the second device is positioned over the first device and internal of the second body space. In some embodiments, at least one of the first and second devices can be slidable relative to the other device and the second device can be positioned external of the second body space. The first device can extend distally of the first device when the first and second devices are interlocked. 
     In accordance with another aspect of the present invention, an implantable flow connector implantable into a body of a patient for fluidly coupling a first space within the body of the patient with a second space within the body of the patient is provided. The implantable flow connector comprises a conduit having a lumen having a first orifice at a first portion of the conduit and a second orifice at a second portion of the conduit, the conduit configured to be implanted into the second space within the body to provide fluid flow between the first and second spaces within the body, and a retention portion having radially extending wall engaging portions, the retention device engageable with the first and second spaces within the body. 
     In some embodiments, the retention portion is embedded in a wall of the conduit. 
     The retention portion can include a plurality of struts with radially extending penetrating elements. The flow connector can include a flange extending radially from the conduit. 
     In accordance with another aspect of the present invention, a system for coupling a first space within the body of a patient with a second space within the body of the patient is provided, the system comprising a flow connector having a conduit and a flange, the conduit having a lumen having a first orifice at a first portion of the conduit and a second orifice at a second portion of the conduit, the conduit configured to be implanted into the second space within the body to provide communication between the first and second spaces within the body, the conduit dimensioned to receive the second space within the body thereover, the flange extending radially from the first portion of the conduit and configured to be implanted in the first space within the body, and a retention device having an opening to receive the first body space such that in a placement position the first space within the body is positioned between an external wall of the flow connector and an internal wall of the retention device, the retention device having a plurality of anchoring tabs at a distal portion positionable external of the first space within the body. Preferably, the anchoring tabs provide an anchor for suture passed through the first space within the body. 
     In accordance with another aspect of the present invention, a retention device for retaining a first body space and a second body space is provided, the retention device comprising a first set of engaging members extending from the first component to engage the first body space and a second set of engaging members extending from the second component to engage the second body space to retain the first and second body spaces to couple the first and second body spaces. In some embodiments, the retention device enables fluid coupling of the first and second body spaces. A non-porous material can be attached internal and/or external of the retention device to enable fluid coupling of the first and second body spaces. 
     In some embodiments, the retention device comprises a first component and a second component, the first component movable relative to the second component, and a first set of engaging members can extend from the first component and the second set of engaging members can extend from the second component. Preferably, the first and second engaging members have tissue penetrating tips. In some embodiments, the first and second components releasably interlock. The first and second components can interlock by a protrusion on one of the components engaging an opening in the other component. 
     In some embodiments, the retention device is formed of a plurality of struts and has an axial opening. 
     The present invention also includes method of implanting the flow connector. In accordance with one method of the present invention a method of implanting and securing an implantable flow connector in a body of a patient for providing communication of a first space within the body of the patient with a second space within the body of the patient is provided comprising the steps of a) providing a flow connector having a lumen having a first orifice at a first portion of the conduit and a second orifice at a second portion. b) providing a retention device having a proximal portion and a distal portion, c) inserting the retention device into the first space within the body, d) subsequently inserting the flow connector through an opening in the retention device so the second portion of the flow connector extends into the first space within the body; and e) placing the second space within the body over the retention device. 
     In some embodiments, the step of inserting the retention device into the first space within the body comprises compressing the retention device to reduce its outer diameter. 
     In some embodiments, the step of inserting the retention device includes placing the retention device in a delivery cannula wherein it is compressed and then releasing the retention device from the cannula so it returns to a non-compressed position. 
     In some embodiments, the retention device includes a first set of engaging elements with penetrating tips penetrating the first space within the body when the distal portion of the retention device is in a placement position within the first space within the body and/or a second set of engaging elements with penetrating tips penetrating a wall of the second space within the body when the second space within the body is in a placement position over the retention device. 
     The second portion of the flow connector can include a flange extending radially from the connector and engaging an inner wall of the first space within the body. 
     In some embodiments, the retention device includes a first component and a second component, and the method further includes the step of interlocking the first and second components. In some embodiments, the first component is distal of the second component and the second component engages the first space within the body and the first component engages the second space within the body. 
     In some embodiments, one of the first and second components has at least one locking tab and the other component has at least one slot, and the step of interlocking the components includes the step of causing the at least one locking tab to locking engage the at least one slot, and preferably the components can be released after locking if desired. 
     In some embodiments, the step of inserting the flow connector through an opening in the retention device includes the step of placing the flow connector in a reduced profile position within a delivery member and inserting the delivery member through the opening in the retention device. 
     In some embodiments, the first space within the body is a source body space and a proximal portion of the flow connector is inserted through an opening formed in a tissue wall of the source body space, and the second space within the body is a destination element and a distal portion of the flow connector is insertable into the destination element through an opening in a surface of the destination element. 
     In accordance with another aspect of the present invention, a method for forming a sutureless anastomosis between a first space within a body of a patient and a second space within the body of the patient is provided, the method comprising the steps of a) providing a flow connector having a lumen having a first orifice at a first portion of the conduit and a second orifice at a second portion, b) providing a retention device having a plurality of penetrating members engageable with the wall of at least one of the spaces within the body; and c) positioning the flow connector internally of the retention device. 
     In some embodiments, the flow connector includes a flange extending radially outwardly from the second portion, and the flange of the flow connector can be positioned in the first space within the body and the first orifice can be positioned within the second space within the body. 
     The method can further comprise the step of inserting the retention device into the first space within the body wherein the step of positioning the flow connector internally of the retention device occurs subsequent to the step of inserting the retention device into the first space within the body. The step of positioning the flow connector internally of the retention device can further comprise the step of opening the retention device to provide a side entry to receive the flow connector therein. 
     The method may further comprise the step of placing the second space within the body over an external wall of the retention device, and this step can occur in some embodiments subsequent to the step of positioning the flow connector internally of the retention device. 
     In some embodiments, the retention device includes first and second components, and the method further comprises the step of interlocking the first and second components to secure the components together and to maintain a fluid connection between the first space within the body and the second space within the body. The step of interlocking the components can include the step of sliding the first component over the second component. 
     In accordance with another aspect of the present invention, a method of implanting and securing an implantable flow connector in a body of a patient for providing communication of a first space within the body of the patient with a second space within the body of the patient is provided, the method comprising a) providing a flow connector having a lumen having a first orifice at a first portion of the conduit, a second orifice at a second portion and a retention portion, the retention portion having a first plurality of penetrating members to engage the first body space, b) inserting the flow connector into the first space within the body, and c) placing the second space within the body over the flow connector. 
     A second plurality of penetrating members can be positioned proximal of the first plurality of penetrating members to penetrate the second body space when positioned over the flow connector. 
     In some embodiments, the step of placing the second space within the body over the retention device occurs subsequent to the step of inserting the flow connector into the first space within the body. 
     In accordance with another aspect of the present invention, a method of implanting and securing an implantable flow connector in a body of a patient for providing communication of a first space within the body of the patient with a second space within the body of the patient is provided, the method comprising the steps of a) providing a flow connector having a lumen having a first orifice at a first portion of the conduit and a second orifice at a second portion, b) providing a retention device having a proximal portion and a distal portion, c) inserting a proximal portion of the flow connector into the first body space, d) placing the second space within the body over the flow connector and e) subsequently placing the retention device over the second space within the body. 
     The step of placing the retention device over the second space within the body can comprise the step of opening the retention device to provide a side entry for the second space within the body. 
     In some embodiments, the retention device has an outer component and an inner component, wherein the outer component engages the first space within the body, and the method may further comprise the step of moving one of the first and second components relative to the other component to interlock the first and second components. 
     In some embodiments, the step of placing the retention device over the second body space places a plurality of suture tabs on an external surface of the first body space. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention are described herein in conjunction with the accompanying drawings, in which: 
         FIG. 1A  is a side view of one embodiment of a flow connector of the present invention; 
         FIG. 1B  is a modified top view of the embodiment of the present invention illustrated in  FIG. 1A  taken along cross-section line  1 B- 1 B in  FIG. 1A ; 
         FIG. 1C  is an isometric view of another embodiment of the flow connector of the present invention; 
         FIG. 1D  is another isometric view of the embodiment of e flow connector illustrated in  FIG. 1C ; 
         FIG. 1E  is yet another isometric view of the embodiment of the flow connector illustrated in  FIG. 1C ; 
         FIG. 1F  is a further isometric view of the embodiment of the flow connector illustrated in  FIG. 1C ; 
         FIG. 2A  is a cross-sectional view of a first tissue-enclosed body space in a recipient having one embodiment of the present invention implanted therein; 
         FIG. 2B  is another cross-sectional view of a first tissue-enclosed body space in a recipient having one embodiment of the present invention implanted therein; 
         FIG. 3  is a perspective view of another embodiment of the flow connector of the present invention illustrated with respect to a tissue-enclosed body space into which the flow connector of the present invention is to be implanted; 
         FIG. 4  is a perspective view of one embodiment of the present invention with an imaginary plane having an imaginary midline; 
         FIG. 5  is a cross-sectional view of one embodiment of the present invention with an imaginary plane having an imaginary midline; 
         FIG. 6  illustrates a bottom view of another embodiment of the flow connector of the present invention; 
         FIG. 7A  illustrates a perspective view of an alternate embodiment of the flow connector of the present invention having shorter longitudinal sections than the embodiment illustrated in  FIG. 1A ; 
         FIG. 7B  illustrates a perspective top view of the embodiment of the flow connector illustrated in  FIG. 7A ; 
         FIG. 8A  is a simplified side of another embodiment of the present invention, 
         FIG. 8B  is a simplified bottom view of another embodiment of the present invention, 
         FIG. 9A  is a high level flowchart of a method for implanting a flow connector according to one embodiment of the present invention; 
         FIG. 9B  is a detailed flowchart of one method for implanting the flow connector of the present invention, in accordance with one embodiment of the present invention; 
         FIG. 10A  illustrates tying off all branches from the second tissue-enclosed body space, according to one embodiment of the present invention; 
         FIG. 10B  illustrates occluding flow of liquids within the second tissue-enclosed body space; 
         FIG. 10C  illustrates marking an orientation line along the second tissue-enclosed body space and also forming an artificial opening on the second tissue-enclosed body space; 
         FIG. 10D  illustrates inserting a flow connector according to one embodiment of the present invention in the second tissue-enclosed body space; 
         FIG. 10E  illustrates a flow connector according to one embodiment of the present invention inserted and secured in a second tissue-enclosed body space with a portion of the second tissue-enclosed body space removed; 
         FIG. 10F  illustrates marking a position on the first tissue-enclosed body space where an opening will be formed; 
         FIG. 10G  illustrates a first issue-enclosed body space after an artificial opening is manually formed; 
         FIG. 10H  illustrates a first tissue-enclosed body space connected to a second tissue-enclosed body space via one embodiment of the present invention; 
         FIG. 11A  illustrates a simplified schematic view of a portion of the second interface according to one embodiment of the present invention; 
         FIG. 11B  illustrates a perspective view of a portion of the second interface according to a further embodiment of the present invention; 
         FIG. 11C  illustrates a cross-sectional view of a portion of the second interface according to another embodiment of the present invention; 
         FIG. 11D  illustrates a cross-sectional view of a portion of the second interface according to a yet further embodiment of the present invention; 
         FIG. 11E  illustrates a cross-sectional view of a portion of the second interface according to another embodiment of the present invention; 
         FIG. 11F  illustrates a cross-sectional view of a portion of the second interface according to yet another embodiment of the present invention; 
         FIG. 11G  illustrates a cross-sectional view of a portion of the second interface according to a further embodiment of the present invention; 
         FIG. 11H  illustrates a cross-sectional view of a portion of the second interface according to a yet further embodiment of the present invention; 
         FIG. 11I  illustrates a cross-sectional view of a portion of the second interface according to another embodiment of the present invention; 
         FIG. 11J  illustrates a cross-sectional view of a portion of the second interface according to yet another embodiment of the present invention; 
         FIG. 11K  illustrates a perspective view of a portion of the second interface according to one embodiment of the present invention; 
         FIG. 11L  illustrates a perspective view of a portion of the second interface according to another embodiment of the present invention; 
         FIG. 11M  illustrates a perspective view of a portion of the second interface according to yet another embodiment of the present invention; 
         FIG. 11N  illustrates a perspective view of a portion of the second interface according to a yet further embodiment of the present invention; 
         FIG. 11O  illustrates a perspective view of a portion of the second interface according to another embodiment of the present invention; 
         FIG. 11P  illustrates a perspective view of a portion of the second interface according to yet another embodiment of the present invention; 
         FIG. 11Q  illustrates a perspective view of a portion of the second interface according to a further embodiment of the present invention; 
         FIG. 12A  illustrates another embodiment of the present invention in which the second interface further comprises barbs; 
         FIG. 12B  illustrates yet another embodiment of the present invention in which the second interface comprises an elbow as well as a retention collar; 
         FIG. 13  is a cross-sectional view of a second interface according to one embodiment of the present invention in which the outer diameter increases while the wall thickness of the second interface remains substantially constant; 
         FIG. 14  is a cross-sectional view of a second interface according to yet another embodiment of the present invention in which the outer diameter remains substantially constant while the wall thickness decreases; 
         FIG. 15  is a cross-sectional view of a second interface according to yet another embodiment of the present invention in which the distal end of the second interface is uneven; 
         FIG. 16  illustrates an embodiment according to the present invention in which the first interface and second interface are formed separately and then joined together before implantation; 
         FIG. 17A  is a perspective view of the second interface of a flow connector according to one embodiment of the present invention in its naturally collapsed state prior to implantation; 
         FIG. 17B  is a perspective view of the second interface of a flow connector according to one embodiment of the present invention in its expanded state after implantation and forced expansion; 
         FIG. 18A  is a perspective view of the second interface of a flow connector according to yet another embodiment of the present invention in its naturally expanded state prior to implantation; 
         FIG. 18B  is a perspective view of the second interface of a flow connector according to yet another embodiment of the present invention in its forced collapsed state, ready for implantation in the recipient; 
         FIG. 19  is a perspective view of one embodiment of the present invention in which an artificial conduit and two flow connectors are provided for implantation in a recipient; 
         FIG. 20  is a perspective view of a first embodiment of a retention device for use with the flow connector; 
         FIG. 21  is a top view of the retention device of  FIG. 20 ; 
         FIG. 22  is a perspective view of the retention device of  FIG. 20 ; 
         FIG. 23  is a perspective view of the retention device of  FIG. 20  shown prior to insertion through the opening in the first body space, e.g. artery, and shown in a reduced profile position within an insertion cannula; 
         FIG. 24  is a perspective view of the retention device of  FIG. 20  shown inserted through the opening in the artery; 
         FIG. 25  is a view similar to  FIG. 24  showing expansion of the retention device when removed from the insertion cannula; 
         FIG. 26  is a perspective view illustrating a flow connector being inserted in a reduced profile configuration within a delivery sheath (cannula) through the axial opening of the retention device and into the artery; 
         FIG. 27  illustrates the flow connector released from the delivery sheath to expand within the axial opening in the retention device; 
         FIG. 28  is a view similar to  FIG. 27  showing proximal movement of the flow connector and retention device so the hooks of the retention device penetrate the wall of the artery adjacent the opening in the artery; 
         FIG. 29  is a view similar to  FIG. 28  showing the second body space, e.g. a vein, prior to placement over the retention device of  FIG. 20 ; 
         FIG. 30  illustrates the vein of  FIG. 29  being placed over the retention device, with the tines of the retention device penetrating through the wall of the vein; 
         FIG. 31  is a perspective view of an alternate embodiment of the retention device of the present invention; 
         FIG. 32  is a perspective view of another alternate embodiment of the retention device of the present invention showing both the inner and outer member; 
         FIG. 33  is a perspective view of the retention device of  FIG. 32  with the outer member shown separated from the inner member; 
         FIG. 34  is a front view of the inner member of the retention device of  FIG. 32 ; 
         FIG. 35  is a side view of the inner member of the retention device of  FIG. 32 ; 
         FIG. 36  is a rear view of the inner member of the retention device of FIG. 
         FIG. 37  is a top view of the retention device of  FIG. 32  in the normal placement configuration; 
         FIG. 38  is a top view of the retention device of  FIG. 32  shown starting to be spread to an open position for receiving the second body space, e.g. a vein; 
         FIG. 39  is a top view of the retention device of  FIG. 32  shown in the open (spread) position for receiving the vein; 
         FIG. 40  illustrates a flow connector positioned within the first body space, e.g. an artery, a vein positioned over the flow connector, and the retention device of  FIG. 32  being moved toward the vein for positioning thereover; 
         FIG. 41  illustrates the retention device of  FIG. 32  positioned over the vein and flow connector and further showing the distal portion of the outer body member secured to the artery and the outer and inner members interlocked; 
         FIG. 42  is a perspective view of another alternate embodiment of the retention device of the present invention, the retention device embedded in a flow connector; 
         FIG. 43  is a top view of the retention device of  FIG. 42 ; 
         FIG. 44  is front view of the retention device of  FIG. 42 ; 
         FIG. 45  illustrates the distal portion of the retention device of  FIG. 42  placed within a first body space, e.g., an artery, and further showing a vein placed over the retention device with the tines of the retention device penetrating the wall of the vein; 
         FIG. 46  is a view similar to  FIG. 45  illustrating the retention device of  FIG. 42  pulled proximally so the hooks of the retention device penetrate the wall of the artery around the opening; 
         FIG. 47  is a perspective view of an alternate embodiment of the retention device of the present invention illustrating the proximal and distal connectors separated; 
         FIG. 48  is a top view of the distal connector of  FIG. 47 ; 
         FIG. 49  illustrates the distal connector of  FIG. 47  positioned within the artery and the proximal connector of  FIG. 47  being moved toward the distal connector and having a second body space, e.g. a vein (shown in cross-section) positioned thereover; 
         FIG. 50  is a view similar to  FIG. 49  showing the proximal connector interlocked with the distal connector; 
         FIG. 51  is a view similar to  FIG. 50  showing the retention device and flow connector pulled proximally so the hooks of the distal connector penetrate the wall of the artery around the opening; 
         FIG. 52  is a perspective view of another alternate embodiment of the retention device of the present invention; 
         FIG. 53  is a top view of the retention device of  FIG. 52 ; 
         FIG. 54  is a top view of the retention device shown in the open (spread) position to receive a second body space, e.g. a vein, within the opening; and 
         FIG. 55  illustrates the retention device of  FIG. 52  positioned around a vein having a flow connector therein and abutting an outer surface of the wall of the artery. 
     
    
    
     DETAILED DESCRIPTION 
     Aspects of the present invention are generally directed to an implantable flow connector. Other aspects of the present invention are also directed to an implantable flow connector and a retention device for securing the flow connector. The flow connector of the present invention is configured to be implanted in a tissue-enclosed body space such as a body conduit or body reservoir to provide a flow path for fluid from the source body space to another body space, a man-made or body conduit, an external or implanted medical device, or other destination element. 
     Embodiments of the flow connector comprise a conduit having a lumen that terminates at an orifice on opposing ends of the conduit, and a flange radially extending from one of the two ends of the conduit. The flow connector is configured to be implanted into the source body space via a natural or artificial opening (e.g., a man-made opening) in a region of the tissue wall that defines the body space. The flange surrounds the conduit orifice through which the conduit lumen is fluidically coupled to the interior of the body space, and is configured to be self-retained in the body space. 
     The conduit is also configured to be retained in the noted destination device or body space or body region (collectively and generally referred to herein as the destination element). For example, when the destination element is a tissue-enclosed body space, the conduit is configured to be implanted into the destination body space via a natural or artificial opening in the tissue wall defining that body space. Once implanted, fluid exiting the conduit orifice at the distal end of the flow connector flows into the destination element. As such, the flow connector of the present invention fluidically couples the source body space and destination device or body space. 
     As noted, embodiments of the flow connector of the present invention may be used to fluidically couple any tissue-enclosed body space or implanted medical device to any type of destination including any other tissue-enclosed body space, other areas in the body, or an external or implanted medical device. Embodiments of the flow connector may be configured to be implanted in any tissue-enclosed body space including, but not limited to, body conduits such as blood vessels, lymph ducts, tear ducts, bowels, urethra, etc., which have a lumen through which fluid is carried to facilitate circulation, excretion or other fluid transfer, as well as body reservoirs such as the stomach, bladder, gall bladder, lymph nodes, etc., which temporarily or permanently retain fluid. For ease of description, embodiments of the flow connector described below are specifically configured for implantation to create an arteriovenous (AV) fistula and, more specifically, an AV fistula in the upper or lower extremity to provide vascular access for hemodialysis patients. 
       FIG. 1A  is a side view of one embodiment of a flow connector of the present invention. In  FIG. 1A , flange  102  is a circumferential flange and is configured to radially extend from conduit  104  proximate to its first or proximal end  131  of conduit  104 . Conduit  104  terminates at proximal end  131  of conduit  104  at an orifice. A second orifice is disposed on the opposite side of conduit  104  at its distal end  132 . Flange  102  comprises a contact surface  126 , which is configured to contact an inner surface of the tissue wall defining the source body space of a recipient when it is implanted therein. On the opposite side of flange  102  from contact surface  126  is an exposed surface  128  which is exposed to fluids passing through the source body space (not shown). 
     In one embodiment of the present invention, flange  102  comprises a plurality of circumferentially adjacent sections. For example, a pair of opposing flange sections  112 A and  112 E can be provided. In those embodiments designed for implantation in a body conduit, flange sections  112  are referred to as longitudinal flanges, and flange section  112 A is referred to as heel section  112 A while flange section  112 B is referred to as toe section  112 B. In addition to longitudinal sections  112 , there is a pair of substantially similar lateral sections  114 A,  114 B extending from opposing sides of conduit  104  approximately equidistant from flanges  112 A,  112 B. Circumferentially opposed sections  114 A,  114 B, also referred to herein as lateral sections  114  due to their substantially orthogonal positioning relative to longitudinal sections  112 , are configured to extend from flange  102  as illustrated in  FIGS. 1C-1E , on opposing sides of conduit  104 , and are further configured to extend circumferentially around a longitudinal axis  110  of the source body space in which flange  102  is to be implanted. The circumferential radius of lateral sections  114 A,  114 B is selected based on the radius of curvature of the region of the source body space in which flow connector  100  is to be implanted. In one embodiment, the radius  297  defined from longitudinal axis  110  to contact surface  126  of lateral sections  114 A,  114 B is substantially equal to the radius  298  defined from longitudinal axis  110  to the inner surface of the source body space. In other embodiments, radius  297  defined from longitudinal axis  110  to contact surface  126  of lateral sections  114 A,  114 B is larger than the radius  298  defined from longitudinal axis  110  to the inner surface of the source body space. Furthermore, in those embodiments, flange  102  is constructed of shape-memory material such that external forces exerted on flange  102  made of memory material may cause flange  102  to at least partially bend, but the nature of the memory material will generate forces to return flange  102  to its original shape. In such embodiments where the radius of lateral sections  114 A, B is greater, that radius defined from longitudinal axis  110  to contact surface  126  of lateral sections  114 A, B may be 1 to 10% larger than the radius defined from longitudinal axis  110  to the inner surface of the source body space. The larger radius of lateral sections  114 A, B combined with the nature of the memory material with which it is constructed will generate a chronic outward force when flow connector  100  is implanted within the source body space, which will in turn cause the walls of the source body space to resist the outward force, thereby providing a compression force to lateral sections  114 A, B. The compression force applied to lateral sections  114 A, B in turn urges contact surface  126  of flange  102  towards the opening in the tissue wall of the source body space, thus providing a seal between contact surface  126  of flange  102  and the tissue wall such that fluid within the source body space will not leak after implantation of flow connector  100 . It is to be understood that in one embodiment of the present invention, some fluid from the source body space may or may not leak immediately after implantation. However, with normal physiological healing processes, such leakage will soon thereafter cease as the aforementioned seal will be provided by contact surface  126  on flange  102  with the tissue wall, thereby eliminating the need for additional elements such as glue, sutures etc. in order to stop or prevent fluid leakage. 
     In addition to providing a seal between contact surface  126  and flange  102 , as described above, the larger radius of lateral sections  114 A, B combined with the nature of the memory material with which it is constructed also acts to provide support for flow connector  100 . As used herein, supporting flow connector  100  refers to physically supporting flow connector  100  such that it retains its position within the source body space, after implantation, without other components or objects contributing towards the retaining of its implanted position. 
     In one embodiment of the present invention, lateral sections  114 A, B extend circumferentially around the interior surface of the source body space so as to leave approximately 180° of the source conduit&#39;s interior surface circumferentially uncovered by lateral sections  114 A, B and flow connector  100  generally. By leaving approximately 180° uncovered, obstruction to the flow of fluid within the source body space is minimized while enhancing stability provided by lateral sections  114 A, B to flow connector  100  when implanted. Longitudinal sections  112  are also circumferentially curved with respect to the interior surface of the source body space such that contact surface  126  makes contact with the interior surface of the source body space in a sealing region  116 , thereby providing a fluid tight or hydrophobic seal as well as stability between flow connector  100  and the source body space. 
     Adjacent to sealing region  116  is reinforcement region  118 , configured to provide physical support to flow connector  100  by being constructed and arranged to oppose various explanting or other forces that may be exerted on flange  102  and conduit  104  when flow connector  100  is implanted in the source body conduit. Reinforcement region  118  is configured to have a rigidity that it aids in the opposition of deflection forces, and is therefore less prone to flexing of portions of flange  102  and/or conduit  104 . The rigidity of reinforcement region  118  decreases in a radially-increasing direction thereby aiding in the implantation of flange  102  in the source body space. It should be appreciated that the rigidity may be provided in various ways, according to various embodiments of the present invention. For example, reinforcement region  118  may have a composition with a rigidity which makes it more rigid than sealing region  116  or other portions of flange  102 . For example, in one embodiment of the present invention, sealing region  116  may be manufactured with material having a Shore value of 80 A and reinforcement region  118  may be manufactured with material having a Shore value of 55 D. In other embodiments, reinforcement region  118  may be manufactured with the same material as its adjacent or other sections of flange  102 , but reinforcement region  118  may be configured to be thicker than adjacent sections of flange  102 , thereby making reinforcement region  118  more rigid. By avoiding substantial deflecting or bending, flange  102  remains larger than the aperture in the source body space through which flange  102  was inserted, thus preventing explanting or pull-out from the source body space. As used herein, substantial deflecting by flange  102  refers to the reduction of the surface area of flange  102  to a size allowing flange  102  in its deflected state to fit through aperture in the source body space through which flange  102  was inserted. 
     Reinforcement region  118  is proximal to conduit  104  so as to provide structural integrity to conduit  104  such at the orifice at the proximal end  131  of conduit  104  can withstand a greater amount of compression force than without reinforcement region  118  being present. As will be further discussed below, reinforcement region  118  also may assist in opposing explant forces that may be applied, intentionally or inadvertently, on flow connector  100 . Although reinforcement section  118  is illustrated in  FIGS. 1A-1C  to be substantially contiguous, it is to be understood that in other embodiments of the present invention reinforcement section  118  may not be contiguous but may have multiple reinforcement regions  118  disposed circumferentially around conduit  104 . Similarly, it is to be understood that although reinforcement region  118  is illustrated in  FIG. 1B  is shown as having a similar or at least a corresponding perimeter as that of flange sections  112 ,  114 , in other embodiments of the present invention, reinforcement region  118  may have a perimeter which is shaped differently from that of flange sections  112 ,  114 . 
     Longitudinal sections  112  are configured to facilitate implantation of flow connector  100  while also opposing pullout forces which may otherwise pull flow connector  100  out from the source body space (not shown) after flow connector  100  is implanted. Lateral sections  114 A,  13  are also configured to facilitate implantation and further configured to maintain the position of flow connector  100  with respect to the source body space (not shown) after flow connector  100  is implanted. In one embodiment of the present invention, lateral sections  114 A, B have a radius of curvature substantially identical to the radius of curvature of the source body space into which it is to be implanted. In other embodiments of the present invention, lateral sections  114 A, B has a curvature radius which is slightly larger than the curvature radius of the source body space into which it is to be implanted. When this embodiment is implanted in the source body space, the larger curvature radius of lateral sections  114 A, B will cause the source body space to generate compression forces on the larger lateral sections  114 A, B which will in turn promote the maintenance of the position of flow connector  100  in the source body space. 
       FIG. 1B  is a cross-sectional view along the line  1 B- 1 B noted in  FIG. 1A , in which a substantial portion of the conduit body  130  is shown as if removed for the purpose of showing an unobstructed view of the longitudinal sections  112  and lateral sections  114 . In the embodiment shown in  FIG. 1B , heel section  112 A and toe section  112 B have apices, heel section apex  121  and toe section apex  122 , respectively, when viewed from the perspective illustrated in  FIG. 1B . In this embodiment, heel section apex  121  and toe section apex  122  come to a sharp point which may be helpful in redirecting fluid flowing within the source body space so as to prevent or minimize disturbances in flow shear stress, eddy flow, foil effects, turbulence, resistance, tube wall deformation, and tensile stress/strain distributions that can lead to intimal hyperplasia and other similar or associated conditions. Similarly, as depicted in  FIG. 1A , flange edge  140  may be chamfered to an angle, for example 60°, so as to similarly redirect fluid flowing within the source body space for the same purpose. 
     Multiple cutout regions  124  are disposed between longitudinal sections  112  and lateral sections  114 . Cutout regions  124  represent an absence of material between those flanges  112 ,  114  and are dimensioned and configured to facilitate temporary foldover of flanges  112 ,  114  during implantation of flow connector  100 . Sealing region  116  is also disposed over a portion of cutout regions  124  to ensure that the contact surface  126  around conduit body  130  is sealed with respect to the source body space so that fluids flowing through the source body space remains either within the source body space or through the lumen of conduit  104 . 
     As noted above, flow connector  100  also comprises conduit  104  which is connected to flange  102  along joint region  106 . At joint region  106 , the proximal end  131  of conduit body  130  and flange  102  are joined such that first conduit orifice  120  leads into the lumen of conduit body  130 , as illustrated in  FIGS. 1E and 1F , which shows at least a partial view of exposed surface  128  of flange  102 , as well as first conduit orifice  120  leading into the lumen of conduit body  130 . In the embodiment illustrated in  FIGS. 1A and 1B , conduit portion  106  is depicted largely as comprising a cylindrical conduit body  130 . However, it is to be appreciated by one having ordinary skill in the art that conduit body  130  may have other shaped tubular bodies other than a cylindrical one in other embodiments of the present invention. For example, in other embodiments of the present invention, conduit body  130  may comprise a conduit body  130  with a rectangular or irregular cross section and a similarly shaped longitudinal lumen disposed therein. On the opposite end of conduit body  130  from proximal end  131  is distal end  132  of conduit body  130  as well as second conduit orifice  134  which is disposed at distal end  132 . Second conduit orifice  134  allows fluid flow traveling through the lumen of conduit body  130  to exit through second conduit orifice  134 . For example, in one embodiment of the present invention in which a source body space, such as a vein or artery, is coupled to conduit  104 , fluid flowing through the source body space into which flange  102  is implanted is diverted through first conduit orifice  120 , through the lumen of conduit body  130  and out of second conduit orifice  134  into the source body space. 
     Although the construction of flow connector  100  may vary depending on the one or more source conduits in which flow connector  100  is to be implanted, embodiments of the present invention may differ in terms of the material comprising flow connector  100 , the durometer values of materials selected, thicknesses of the various components of flow connector  100  described herein or shown in the figures, and are considered a part of certain embodiments of the present invention. In one embodiment, flange  102  has a thickness ranging between approximately 0.15 mm and approximately 0.35 mm. Similarly, the outside diameter of conduit body  130  has a similar thickness range between approximately 0.15 mm and 0.50 mm and more preferably, of between approximately 0.30 mm and approximately 0.45 mm. In another embodiment, the outside diameter of conduit body  130  has a thickness of approximately 0.35 mm. The thickness of flange  102  may be decreased as flange  102  is made to extend further which will maintain the pullout forces necessary for flange  100  to be pulled out of the source body space in which it is implanted. Similarly, the thickness of flange  102  may be increased as the flange  102  is made to extend less, 
     As shown in  FIG. 1C-1F  and in cross-section in  FIG. 5 , conduit body  130  may comprise a series of barbs or protrusions  129  which extend radially from conduit body  130 . In one embodiment of the present invention, the protrusions  129  provide periodic increases in the outside diameter of conduit body  130  so that the source body space within which conduit body  130  is inserted are positioned over conduit body  130  in a friction fit over the increased diameter portions of protrusions  131 . Furthermore, once the source body space is positioned over conduit  104  over protrusions  131 , one or more sutures may be disposed circumferentially around conduit body  130  and in the areas between, conduit body  130  and the outer diameter of protrusions  131 , thereby snugly retaining the source body space in place with respect to conduit  104 . When one or more sutures are thus disposed, the one or more sutures that compress the source body space towards the conduit portion  104  will maintain its position since the diameter of the one or more sutures are fixed to be smaller than the outer diameter of the protrusions, which therefore provides an interference fit to prevent the one or more sutures from translating along the longitudinal axis  108  of conduit body  130 . 
     In certain embodiments of the present invention, conduit body  130 , shown in  FIGS. 2A and 2B  as conduit body  230 , has a conduit recess  236  disposed thereon. Conduit recess  236  is configured such that a source body space, such as source body space  260 , rests within conduit. recess  236  when flange  102 , shown in  FIGS. 2A and 2B  as flange  202 , is positioned within the source body space as described below. In one embodiment of the present invention, conduit recess  236  is configured to have a depth of between 0.5 mm and 1.0 mm in order to accommodate a source body space to allow it to rest therein. In other embodiments of the present invention, recess  236  may be configured to have a deeper recess, for example 1.0 mm. The height of the conduit recess  236 , measured from flange  202  toward the distal end of conduit body  204  is approximately 0.8 mm, which will vary depending on the thickness of the source body space  260  which is accommodated within conduit recess  236 , as depicted in  FIG. 2A . Also as shown in  FIG. 2B , conduit  204  of one embodiment of the present invention is shown to be angled approximately 60° from the horizontal axis in the illustration with respect to flange  202 . This angle may vary in other embodiments of the present invention depending on the situation or the needs of the recipient. For example, in other embodiments of the present invention, conduit  204  may be configured with an angle between 10° to 90° from the horizontal axis shown in  FIG. 2B . As one having skill in the art would appreciate, this angle can be from the opposite side as well with respect to flange  202 . 
     As noted previously, flow connector  100 , shown in  FIG. 3  as flow connector  300 , is configured to be at least partially placed within a source body space. In the embodiment illustrated in  FIG. 3 , flange  102  is configured to be positioned through an opening  303  on source body space  360 . More specifically, one or more of heel section  312 A, toe section  312 B, and lateral sections  314 A, B are temporarily deformed or bent with respect to flow connector  100  so that flange  102  can be inserted through opening  303 . Opening  303  may be an existing opening or may be manually and/or intentionally formed, at least in part, to allow flange  102  to be inserted therethrough during the implantation of flow connector  300  within source body space  360 . In the embodiment shown in  FIG. 3 , heel section  312 A is longer than toe section  312 B. The greater length of heel section  312 A is configured to promote stability and the position of flange  102  within source body space  360 . Additionally, the shorter length of toe section  312 B, in the present embodiment of the invention, is configured to promote easier insertion of flange  102 , especially in implantation methods where only lateral sections  314 A, B are temporarily deformed, with longitudinal sections  312  inserted through opening  303  in their substantially extended position. 
     In the embodiment illustrated in  FIG. 3 , the fluid flowing substantially along longitudinal axis  310  through source body space  360  is flowing from the direction of heel section  312 A and flowing towards the direction of toe section  312 B. As is seen in the embodiment illustrated in  FIGS. 1 and 3 , the longitudinal axis  108  of conduit body  130  is angled with respect to the longitudinal axis  310  of source body space  360  at an angle of approximately 60° towards to direction of heel section  312 A. In this embodiment of the present invention, the 60° angled source body space  360  is provided to promote, among other things, a controlled rate and/or volume of fluid flow from source body space  360  into conduit body  330 . In other embodiments of the present invention, that angle may not be 60°, but may instead be some other angle, depending on the placement of flow connector  300  within the recipient or the purpose for which flow connector  300  will be used once implanted. For example, in other embodiments of the present invention, conduit body  330  may be angled 90 or 120° with respect to longitudinal axis  310  in order to achieve a desired rate or volume of flow from source body space  360 . 
     In  FIGS. 4 and 5 , an imaginary plane having a midline  409  is shown with respect to flow connector  400  and longitudinal axis  410  of source body space (not shown), according to one embodiment of the present invention. Midline  409  is parallel with respect to longitudinal axis  410  and is disposed on the exposed surface  128  around first conduit orifice  120 . In the embodiment depicted, longitudinal sections  412  are angled upwards 10° from midline  409  starting at transition points  415  as shown. In other embodiments of the present invention, longitudinal sections  412  may be angled by a different amount, for example between 0 and 15°. The angling of longitudinal sections  412  upwards towards the inner surface of the source body space in which flow connector  400  is implanted will cause to be generated one or more deflection forces as a result of longitudinal sections  412  being pressed into the wall of the source body space. These deflection forces will cause a deflection of longitudinal sections  412  downward such that longitudinal sections  412  will be more parallel with midline  409  and longitudinal axis  410  of the source body space. This deflection downward will permit later flanges  414 A, B to be disposed closer to the inner wall of the source body space than if the deflection did not occur, and will also cause a broader contact between contact surface  126  and the inside wall of the source body space once flow connector  400  is positioned within the source body space.  FIG. 5  illustrates the imaginary line with midline  409 , now shown as midline  509 , as well as the 10° angling of longitudinal sections  412 , now shown as longitudinal sections  512 , with respect to longitudinal axis  510  of the source body space. 
     Embodiments of the present invention include embodiments having different configurations of longitudinal and lateral sections. In the embodiment illustrated in  FIG. 6 , longitudinal sections  612 A and  612 B have about the same dimensions. In  FIG. 6 , heel section  612 A is configured to be longer and to come to a pointed apex as illustrated. Toe section  612 B is configured to be shorter than heel section  612 A and has an apex which is more round than the apex of the heel section  612 A. The shorter length of toe section  612 B is sufficient, in cooperation with longer heel section  612 A, to oppose the pullout forces described previously, while promoting easier insertion of flange  602  into the opening (not shown) of the source body space. In certain embodiments of the present invention, sections  612 A, B are configured to each be approximately 35-65% in length of the outside diameter of first conduit orifice  620 . In alternative embodiments of the present invention, sections  612 A, B are each configured to be approximately 50% in length of the outside diameter of first conduit orifice  620 . 
     Similarly, in the embodiment illustrated in  FIGS. 7A and 7B , longitudinal sections  712  are configured substantially identically to one another. As shown, heel sections  712 A and toe section  712 B are both shorter than in other embodiments shown and described herein.  FIG. 7B  is a view along cross-section line  7 B- 7 B and shows conduit body  730  as if it were partially removed from flow connector  700 . The embodiment of the present invention illustrated in  FIGS. 7A and 7B  is appropriately configured and dimensioned so as to maintain the compensation for pullout forces by longitudinal and lateral sections  712  and  714 , respectively. As noted previously, the thickness of sealing region  116  and reinforcement  118  may of flanges  712 ,  714  may be increased in order to provide make flanges  712 ,  714  more rigid. Alternatively, in other embodiments of the present invention, those components may be constructed of a more rigid material.  FIGS. 7A and 7B  also depicts cutout regions  724  which at least partly promotes flexibility of flanges  712 ,  714  as one or more of flanges  712 ,  714  are temporarily brought together during implantation of flow connector into the recipient&#39;s source body space, 
       FIGS. 8A and 8B  illustrates yet another embodiment of the present invention in which cutout region  824  has zero to little reduction in the material Which comprises the flange  802  of flow connector  800 . Flange  802  may be constructed and dimensioned to be readily bendable upon receiving an external force, such as from a pickup tool being operated by a surgeon, despite having a very minimal or no absence of material in the cutout region  824 . It should be understood by persons having skill in the art that cutout region  824 , and other parts of flange  802  and conduit portion  804  may be modified before or during the implantation procedure, as will be further discussed below. Therefore, cutout region  824 , or longitudinal sections  812  and lateral sections  814  may be modified in vivo to accommodate the dimensions of the source body space or the opening through which flange  802  is to be inserted during implantation of flow connector  800 . 
     In operation, embodiments of the present invention may be implanted in numerous ways. In one particular method of operation as depicted in  FIG. 9A , the source body space is mobilized  900  from other conduits fluidically coupled to the destination body space. The destination body space, for example a vein of a recipient, is ligated and then cut  910  to receive the conduit  104  of flow connector  100 . Once the destination body space has conduit  104  fitted therein, an opening is formed  920  in the source body space. Flange  102  of the flow connector, having the destination body space coupled thereto, is inserted through the formed opening in order to join  930  the source and destination body spaces together. In an alternate method, the flow connector is first inserted through the opening into the source body space and then the destination body space is placed over the flow connector. 
     Expanding on the method outlined above and as further shown in  FIGS. 9B  and  FIGS. 10A-10H  generally, according one embodiment of the present invention, all branches  1003  of other conduits within the body of the recipient are severed or otherwise fluidically decoupled or tied-off  902  from destination body space  1050 , as illustrated in  FIG. 10A . As shown in FIG.  10 B, destination body space  1050  itself is then tied-off or otherwise occluded  911  using a tie or suture  1100 .  FIG. 10C  shows that an orientation line  1102  line is marked on destination body space  1050 , and an opening  1104  is formed along orientation line  1102 . As illustrated in  FIG. 10D , conduit portion  102  of flow connector  1000  is inserted  914  through opening  1104 .  FIG. 10E  illustrates two sutures  1006  which are secured onto destination body space  1050  prior to the occluded end being cut away  916  from the destination body space portion now having flow connector  1000  secured thereto. In  FIG. 10F , a location is identified and marked  922  where an opening in source body space  1060  is to be formed. Once an opening  1112  is formed  924 , as shown in  FIG. 10G , flange  1002  of flow connector  1000  is inserted through opening  1112  and permitted to be securely retained within the walls of source body space  1060  in cooperation with lateral sections  114  and longitudinal sections  112 . 
     A cross-section of a portion of conduit  1404  according to one embodiment of the present invention is illustrated in  FIG. 14 . In  FIG. 14 , the portion shown illustrates a ramp configured to improve the flow from proximal end  1431  to distal end  1432  and out conduit orifice  1434  as it enters the destination element (not shown), for example a blood vessel. In  FIG. 14 , for the portion illustrated, the inside diameter of conduit  1404  gradually increases while the outside diameter of conduit  1404  remains substantially unchanged. By making the inside diameter of conduit  1404  substantially equal to the inside diameter of the destination element, the flow can across the cross-section of orifice  1434  is as uniform or consistent as possible, thus minimizing turbulence and other disturbances in flow which can lead to undesirable biological responses such as intimal hyperplasia. It will be understood that the ramp feature may be provided at either end of conduit  1404 , to provide a smooth flow into and/or out of conduit  1404 . For example, in one embodiment of the present invention, a ramp feature is disposed at both ends of conduit  1404  and promotes a smooth inflow of fluid into conduit  1404  for a limited length of conduit  1404 , followed by a length of conduit  1404  in which the inside diameter remains constant, followed by a final distal length of conduit  1404  wherein a ramp having a gradually increasing inside diameter is provide and facilitates a non-turbulent outflow of the fluid out of conduit orifice  1434 . 
     In other embodiments of the present invention, the outside diameter of conduit  1404  may change from the proximal end  1431  to distal end  1432 . For example, in one embodiment, the outside diameter at each end may decrease gradually along its length. In another embodiment of the present invention, the outside diameter may increase gradually along its length. In yet further embodiments, the outside diameter may increase for some length, before decreasing for another length, and vice versa. As one having ordinary skill in the art will recognize, the outside diameter may be adjusted to be constantly or variably changing to meet specific needs or for specific uses. 
     In certain embodiments of the present invention, the second end of conduit  104  is configured to have an inside diameter approximately equal to the inside diameter of the destination element&#39;s lumen, for example the lumen in a blood vessel. As discussed previously, matching the inside diameters of the distal end of conduit  104  and the destination element at the point in each where fluid flow transitions from one to the other significantly reduces eddy current flow and other disturbances in the flow, which in turn reduces the occurrence of clots, thrombus, intimal hyperplasia, and other conditions which are largely undesirable. In other words, these features enable embodiments of the flow connector of the present invention to restore anatomical blood flow; that is, laminar flow, which is the normal condition for blood flow throughout most of the circulatory system. As one of ordinary skill in the art would appreciate, laminar flow is characterized by concentric layers of blood moving in parallel down the length of a blood vessel. In other words, the highest velocity is found in the center of the vessel while the lowest velocity is found along the vessel wall. 
     Other types of flow disturbances may include, but are not limited to, dead flow areas where a swirling or other types of flow pattern which deviates from a generally linear flow are formed by too steep of a step or diameter change with respect to certain factors such as the rate of flow, the viscosity of the fluid, the inside diameters of conduit  104  and the destination element, among others. In one embodiment of the present invention, conduit  104  has a chamfered distal end  132  or a gradually tapering distal end  132  in which the inside diameter gradually increases approaching the opening of the destination conduit. In another embodiment of the present invention, conduit  104  terminates at orifice  134  proximal the destination conduit at a knife-edge, where the wall thickness immediately proximal to the destination element approaches zero. 
     As illustrated in  FIGS. 1F and 13-15 , the inside surface of conduit  104  (also  1304 ,  1404 ,  1504 ), is a substantially frictionless surface configured to allow fluid flow over the surface without undergoing friction. This smooth surface minimizes or eliminates turbulence which might otherwise be generated during the flow through conduit  104 . 
       FIG. 12B  illustrates another embodiment of the present invention in which bend  1260  is provided at a point along conduit  1204 . The internal surface of bend  1260  in conduit  1204  redirects fluid flowing through conduit  1204 , from flange  1202  to the destination elements, for example a blood vessel. In the embodiment illustrated in  FIG. 12B , a first pre-bend longitudinal axis  1266  is shown as well as a second post-bend longitudinal axis  1268 . In the illustrated embodiment, fluid flowing from flange  1202  through a first pre-bend portion  1265  is redirected by bend  1260  before the fluid enters a second post-bend portion  1267 . While the fluid is thus redirected, conduit  1204  at bend  1260  absorbs the force from the fluid flowing towards bend  1260  as it is redirected towards the destination element (not shown), thus avoiding those forces being applied to a body vessel which would otherwise have received the forces. Using embodiments of the present invention having one or more bends  1260  as described, it is possible to provide an improved connection between the source body space and the destination element. For example, where the source body space is a artery and the destination element is a vein, as illustrated according to a different embodiment of the present invention in  FIGS. 10A-10H , flow connector  1200 B may be utilized to connect body space or vein  1050  with body space or artery  1060  but such that vein  1050  need not be bent as shown in  FIG. 10H . Instead, connector  1200 B is configured with a bend  1260  which would extend from artery  1060  and then bend towards the opening in vein  1050  such that vein  1050  remains substantially straight. 
     In further embodiments of the present invention, as illustrated in  FIG. 15 , distal end  1532  of conduit  1504  is beveled such that orifice  1534  at distal end  1532  is not 90° with respect to the longitudinal axis of conduit  1504 . In the embodiment illustrated, the beveled distal end  1532  is approximately 30° from a plane orthogonal to the longitudinal axis of conduit  1504 . However, a person having ordinary skill in the art will appreciate that the angle may be different depending on the situation in which an embodiment of the present invention is to be used. Beveled distal end  1532  facilitates a better transition of fluid flowing through conduit  1504  and exiting at beveled distal end  1532  into the destination element by accommodating a bend in the destination element by allowing an earlier exit of the fluid flow in the direction of the bend in conduit  1504 . For example, the embodiment illustrated in  FIG. 15  has a beveled end  1532  such that orifice  1534  is biased towards the left. This left-facing orifice  1534  may be used where the destination element is coupled to and extends up from conduit  1504  and bends towards the left. In addition to permitting an earlier exit from conduit  1504 , beveled distal end  1532  also minimizes situations where a bend in the destination element, for example a conduit or blood vessel, causes the inside surface of the vessel to become constricted or reduced. 
     In yet further embodiments of the present invention, where the source body space and the destination element have different outside diameters, the outside diameters may be configured to accommodate the different outside diameters. As illustrated in  FIG. 13 , according to one such embodiment of the present invention, the outside diameter of conduit  1304  may vary from its proximal end  1331  to its distal end  1332 . As shown, the inside diameter of conduit  1304  may also increase at the same rate as the change in the outside diameter of conduit  1304 . However, it is to be understood that in other embodiments of the present invention, the inside diameter may change at a different rate, or not at all, as the change in the outside diameter. 
     As shown in  FIGS. 17A , B, and  18 A, B, according to other embodiments of the present invention, flow connector  1700  and  1800  may be configured to be collapsible ( FIGS. 17A , B) or expandable ( FIG. 18A , B) to further accommodate differences in the inside diameters of the source body space and the destination element. Furthermore, the collapsible and expandable embodiments may be used to assist implantation by implanting conduit  1704 ,  1804  while having a reduced physical size and then being forced (or being allowed) to take on a larger shape to fit, for example seal and retain, the destination or source body space. Conduits  1704  and  1804  may be composed of a mesh material which has various joints or hinges or other manipulable series of parts which permit the overall shape of conduit  1704  and  1804  to be manipulated. Expandable conduit  1704  may be configured with a small cross-sectional shape, as illustrated in  FIG. 17A  and later forced to take on and retain an expanded cross-sectional shape, as illustrated in  FIG. 17B . In one embodiment of the present invention, expandable conduit  1704  may be expanded with a balloon inserted into implanted conduit  1704  and expanded. In another embodiment of the present invention, expandable conduit  1704  may have a mechanical expanding force applied at a proximal end  1731  which is communicated through the expanding portion of conduit  1704  in order to open conduit  1704  as illustrated in  FIG. 17B . In the embodiment illustrated, conduit  1704  comprises finger-like portions which overlap one another as illustrated in  FIG. 17A  but which expand and separate as illustrated in  FIG. 17B . It is to be understood that a portion of the finger-like portions may be used to retain the destination body space while a different portion may be used to provide a seal between conduit  1704  and the destination body space. 
     Similarly, collapsible conduit  1804  may be configured with a shape-memory material, in a mesh or other configuration, which is expanded at rest but can be made to collapse when sufficient force is applied to it. As shown in  FIGS. 18A , B, a portion of conduit  1804  may comprise the collapsible portion while another portion may be a non-collapsible portion. In one embodiment of the present invention, collapsible conduit  1804  may be disposed in a delivery tube (not shown) which is configured to receive conduit  1804  in a collapsed position before being inserted and then delivered in a destination body space. In another embodiment of the present invention, delivery tube (not shown) may be made of a resorbable material such that collapsible conduit  1804  may be delivered into the destination body conduit within the resorbable delivery tube. Subsequent to delivery, the resorbable delivery tube begins to be resorbed and cause the collapsible conduit  1804  to be released and permitted to return to its naturally expanded configuration. 
     According to embodiments of the present invention, as illustrated in  FIGS. 11K and 11L , conduit  1104  may be modified or reduced subsequent to factory manufacturing. For example, according to one embodiment of the present invention, conduit  1104  is configured to allow a surgeon in vivo to evaluate the opening in the destination element, for example a vein, into which the distal end of conduit  1104  is to be inserted. After mentally or physically marking where the conduit  1104  is to be reduced, the surgeon cuts away material from distal end  132  in order to better fit flow connector  100  into the destination element. In other embodiments of the present invention, conduit  1104  may be configured with perforations adjacent one or more recesses  1181  or visual markers such as protrusions  1129  which can aid in the measuring of the portion to be cut or removed. In certain embodiments of the present invention, markers on the outside of conduit  1104  facilitate cutting of conduit  1104  at increments of 0.25 mm, 0.5 mm or 1.0 mm, or variations thereof. In other embodiments of the present invention, perforations along conduit  1104  are provided to facilitate in the cutting or otherwise modifying conduit  1104  at those increments of 0.25 mm, 0.5 mm or 1.0 mm, or variations thereof. Conduit  1104  may be constructed of a material that is resiliently flexible, such as silicone or other materials that are resiliently flexible, as will be appreciated by a person having ordinary skill in the art. Alternatively, conduit  1104  may be constructed of one or more materials so as to be rigid or hard, thus necessitating different tools in order to reduce or otherwise modify it than in embodiments of the present in which conduit  1104  is resiliently flexible. 
     Additionally, certain embodiments of the present invention may have one or more active elements in conduit  104  or flange  102  which are configured and arranged to provide one or more therapeutic benefits. For example, in one embodiment of the present invention, flow connector  100  is constructed of a material so that one or more portions of flow connector  100  is radiopaque. In other embodiments of the present invention, the active element is one or more drug compounds or pharmaceutical materials configured to be released by flow connector  100  and to act on into the area near the flow connector or systemically throughout the recipient. In certain embodiments of the present invention, the one or more pharmaceutical materials may be configured to require heat or fluid-contact activation in order to begin its being released. In other embodiments of the present invention, the pharmaceutical materials on flow connector  100  is further configured to be time-released such that the compounds therein are released gradually over a period of time at a constant or varying rates of release. In yet further embodiments of the present invention, the active element comprises pharmaceutical materials disposed within a heat or fluid-contact activated dissolving capsule shell. 
     As shown in  FIG. 12B , other embodiments of the present invention may comprise a malleable conduit  1204  configured to take on and hold a different configuration upon receiving sufficient external force. For example, in one embodiment of the present invention, the surgeon may apply a bending force to conduit  1204  in order to accommodate the source and destination body conduits. Upon receiving sufficient bending force from the surgeon, conduit  1204  will retain the bend and direct or channel fluid flowing therethrough according to the shape, specifically the internal surface, of conduit  1204 . Malleable conduit  1204  is configured from a mesh or other structure having cooperating elements such as shape memory metals which allow malleable conduit  1204  to retain a shape upon receiving the bending force described. 
     Embodiments of the present invention may be configured to aid in the retention of the destination element (not shown) on the distal end  1132  of conduit  1104 . In certain embodiments of the present invention, as illustrated in  FIGS. 11A and 11B , protrusions  1129  are disposed circumferentially around the exterior surface of conduit  1104 .  FIG. 11A  illustrates conduit  1104  in a simplified profile view, and shows the silhouette of radial protrusions  1129  which are disposed around conduit  1104 .  FIG. 11B  illustrates a plurality of extrusions or projections which are disposed on, or extend from, the exterior of conduit  1104 . As shown in  FIG. 11M , according to another embodiment of the present invention, a plurality of radial protrusions  1129  on conduit  1104  may be provided along the substantial length of conduit  1104 , or at least along a section, for example distal end section  1132 . According to another embodiment of the present invention, protrusions  1129  may be disposed on a separate collar and positioned on conduit  1104  prior to implantation of flow connector  1100 . As illustrated in  FIGS. 11P and 11Q , the retention protrusions  1129  need not be uniform or simple. A matrix protrusion configuration  1129  is illustrated in  FIG. 11P , according to another embodiment of the present invention. In a yet further embodiment of the present invention, sinusoidal protrusions  1129  are illustrated in  FIG. 11Q . 
     In other embodiments of the present invention, the retention feature provided on the surface of conduit  1104  may be surface treatments. In an exemplary embodiment of the present invention illustrated in  FIG. 110 , the exterior surface of conduit  1104  may be dimpled or dented such that the treated exterior surface provides retention. Depending on the size of the dimpling or denting surface treatment, the exterior surface can be configured to provide a friction fit on the interior surface of the destination element, for example a blood vessel. Other retention features may be provided on the exterior of conduit  1104 . For example, in another embodiment of the present invention, a plurality of barbs  1229  or other sharp projections are disposed on the exterior of conduit  1204 . Barbs  1229  are configured such that they at least partially pierce the wall of the destination element, for example a blood vessel, in order to retainingly secure the element on conduit  1204 . In other embodiments of the present invention, barbs  1229  pierces through the destination element while retainingly securing the destination element on conduit  1204 . 
     Flow connector  100 ,  200  further comprises a rest surface  136 ,  236  on conduit  104  adjacent the joint region  106 , as illustrated in  FIGS. 1D and 2B  according to yet further embodiments of the present invention. In the embodiment illustrated in  FIG. 1D , rest surface  136  is a recess in the body of conduit  104  configured to receive a wall of the source body space around rest surface  136  once flange  102  is implanted therein. In the embodiment illustrated, rest surface  136  is substantially smooth and free of protrusions  129  described above which are configured to retain the destination element once the destination element is positioned over protrusions  129 . In the embodiment illustrated in  FIGS. 1D and 2B , rest surface  136  is shaped with a curve, and source body space  227  is shown in  FIG. 2B  as conforming to the curved shape of rest surface  136 . However, the degree to which body space  227  is shown to curve in  FIG. 2B  is exaggerated for illustrative purposes and may not always take the degree of curvature depicted. 
     In addition to the protrusions described above being used to retain the destination element upon being fit on the protrusions, the protrusions may also be used to receive one or more retaining elements such as sutures or a securing collar, or combinations thereof, as in embodiments illustrated in  FIGS. 10E, 11A-11N .  FIG. 10E  illustrates one embodiment of the present invention in which two sutures are placed on the destination element, in this case a vein, in order to compress the vein towards recesses disposed along the exterior surface of conduit  1004 .  FIG. 11A  illustrates one embodiment in which the plurality of adjacent protrusions  1129  cooperatively form angled recess therebetween into which retaining elements such as sutures  1190 , as illustrated in  FIGS. 11E, 11F, 11I, 11J , can compress the destination element at least partly into. In the embodiment illustrated in  FIG. 11B , the retaining elements can compress the destination element, such as the tissue wall of a vein, in between the spaces between protrusions  1129 . In the embodiments of the present invention illustrated in  FIGS. 11C, 11D, 11G, 11H , a securing collar  1169  may be used with a portion of the destination element, for example the tissue wall of a vein, disposed between securing collar  1169  and conduit  1104  to secure the destination element on conduit  1104 . In certain embodiments of the present invention, the destination element portion may be compressed by securing collar  1169  against the exterior surface of conduit  1104 . In other embodiments of the present invention, securing collar  1169  may press the destination element portion into correspondingly shaped recesses along the exterior surface of conduit  1104  such that an interference fit between the recesses and securing collar  1169  will retain the destination element portion on conduit  1104 . Although a plurality of protrusions  1129  may be disposed along a length of conduit  1104  according to certain embodiments of the present invention, such that a surgeon may have a wide variety of choices of protrusions  1129  to use in order to secure the destination element on conduit  1104 , protrusions  1129  may also be provided at distinct locations in order to simplify conduit  1104 , where the surgeon is provided with a reduced number of protrusions  1129 , for example two as shown in  FIG. 11N  according to one embodiment of the present invention. As shown in  FIG. 11N , protrusions  1129  may flare out from a smooth exterior surface of conduit  1104  such that a securing element such as sutures  1190 , configured with a smaller diameter than protrusions  1129 , may be placed nearer the proximal end  1131  of conduit  1104  such that an interference fit is formed between sutures  1190  and protrusions  1129 . In such embodiments, in addition to the one or more sutures acting to retain the destination element on conduit  1104 , the flare at the distal end of conduit  1104  itself may be sufficient to provide a compression fit to also retain the destination element on conduit  1104 . Such a compression fit also acts to provide a seal to prevent leakage flowing through conduit  1104  into the destination element. In alternative embodiments of the invention, flare portions  1129  (referred to previously as protrusions  1129 ) may be constructed as a separate component from conduit  1104  such that conduit  1104  can rotate 360° about a longitudinal axis of flare portion  1129  while flare portion  1129  remains stationary and secure to the destination element. 
     It is to be understood that embodiments of the present invention may be used to connect flow connector described herein with an artificial conduit  1999 , as illustrated in  FIG. 19 . As shown, a first flow connector  1900  is configured to be coupled to artificial conduit  1999  and retained by securing collar parts  1269 A, B. Securing collar parts  1269 A, B combine to form securing collar  1269 . Securing collar parts  1269 A, B each may be configured with a retention feature such as the recess shown for fitting around a correspondingly configured protrusion on the exterior of conduit. In the embodiment illustrated in  FIG. 19 , each end of artificial conduit  1999  is positioned between each of the conduits  1904  and retaining collars  1269 , wherein each of the flanges  1902  of the flow connectors are implanted without the same or different body spaces, such that the flow connectors  1900  become fluidically coupled. In this manner, flow connectors  1900  may be used in bypass or other procedures which can benefit from one or more flanges which provide fluidic coupling as well as self-sealing and self-supporting features, among others. 
     Alternate embodiments to aid retention of the first and second body spaces on the flow connector and to hold the flow connector in the body spaces to keep the flow connector from migrating are illustrated in  FIGS. 20-55 . These retention devices are described herein as used with vessels, e.g. connecting a vein and artery, but can also be used with grafts, other body conduits, etc. as described above. Therefore, although the terms first and second body spaces (or “spaces within the body”) are used herein, each body space can encompass a vessel, graft, conduit or other natural or artificially implanted enclosed element as described above. Further, although in the methods and devices described herein the first body space can be an artery and the second body space a vein, this is by way of example only since the first body space can be a vein and the second body space can be an artery, or can be grafts, body conduits, etc, described herein. 
     In one approach, illustrated in the embodiments of  FIGS. 20-31 and 47-51 , the securement/retention (or stability) device is placed within the vessel and external of the flow connector so the retention device is positioned between the external wall of the flow connector and the internal wall of the vessel. The flow connector asserts a radial outward force against the retention device which engages the vessel(s) as the outer diameter of the flow connector is slightly greater than the internal diameter of the retention devices. In another approach, illustrated in the embodiments of  FIGS. 32-41 and 52-55 , the securement/retention (or stability) device is placed outside the vessel (or graft or body conduit) so the vessel is positioned between the internal wall of the securement/retention device and the external wall of the flow connector and the retention device applies a radial inward clamping force against the vessel and flow connector as the inner diameter of the retention device is slightly smaller than the outer diameter of the flow connector and/of vessel. Further, in some embodiments, the retention devices are one piece units which lockingly engage with both the first and second body spaces; in other embodiments the retention devices are two pieces with one piece engaging the first body space and the other piece engaging the second body space and then the two retention devices are connected or interlocked. 
     The retention devices of  FIGS. 20-51  provide a sutureless connection of the first and second body spaces and sutureless connection of the flow connector to the body spaces which facilitates and simplifies the procedures and improves the consistency of the anastomosis since reliance on the suturing technique of the surgeon is avoided. However, a surgeon would not be precluded from applying a suture(s) if desired. The retention device of  FIGS. 52-55  enables a sutureless connection to the second body space, e.g., destination element such as a vein, but, has tabs for sutures for securement to the first body space, e.g., a source element such as an artery. Each of these retention devices are described below. 
     Turning first to  FIGS. 20-30 , which illustrates one embodiment of an internal retention device, retention device is designated generally by reference numeral  2010 . Retention device  2010  has a proximal end  2012  and a distal end  2014 , the distal end defined herein in the direction of blood flow—flowing in a distal direction. The device  2010  is preferably composed of a metallic material with sufficient springiness so that it can be compressed (collapsed) to a reduced profile position during delivery and return to its original position once delivered. In some embodiments, the device  2010  can be composed of a shape memory material such as Nitinol. Other materials are also contemplated. 
     The device  2010  is preferably formed from a tube having cutouts therein forming a series of struts. The cutouts can be formed from laser cutting or other methods. The struts form a pattern to create substantially diamond shaped openings  2016 , shown in  FIGS. 20 and 22 . The strut pattern and diamond shaped openings enable collapse of the device  2010  for delivery. The strut pattern includes a first (distal) set of connected V-shaped struts  2020  and a second (proximal) set of connected V-shaped struts  2022 , each set  2020  and  2022  extending around 360 degrees to form a closed ring. The proximal vertices  2025  of the first set of struts  2020  is joined to the distal vertices  2023  of the second set of struts  2022 , designated as region  2024 . For clarity, not all of the struts and vertices are labeled in the drawings as not all identical parts are labeled. 
     At the proximal end  2012  of device  2010 , the strut pattern includes an elongated longitudinally extending strut  2026 , extending from the proximal vertex  2027  of the proximal struts  2022 , and each terminating in a hook  2028 . Each hook  2028  curves radially outwardly from the longitudinally extending strut  2026  and curves in a 180 degree arc so that the penetrating (sharpened) tip  2036  which engages and penetrates the first body space points toward the distal end  2014  of the device  2010 . Other hook configurations and angles are also contemplated to achieve the purpose of engaging and penetrating the wall of the body space for the reasons described below. An example of such alternate configuration is described below and illustrated in  FIG. 31 . Additionally a fewer number of hooks can be provided. Although six V-shaped struts  2020  and  2022  are shown, it is also contemplated that a fewer or greater number of V-shaped struts could be provided. 
     At the distal end  2014  of the device  2010  are a series of tines  2030 . The tines  2030  extend from the distal vertex  2029  of the distal struts  2020 . In the illustrated embodiment, the tines  2030  extend from every other distal vertex  2029  of the distal strut  2020 , however, it is also contemplated that a greater number of tines  2030  could be provided, e.g., extending from each vertex  2029 , or alternatively a fewer number of tines  2030  could be provided. The tines  2030  extend proximally from the distal vertex  2025 , extend radially outwardly, and terminate in sharpened penetrating tips  2032 . Other tine configurations and angles are also contemplated to achieve the purpose of engaging and penetrating the wall of the body space for the reasons described below in conjunction with the method of use. 
     The device  2010 , as well as the other retention devices of  FIGS. 31-55  described hereinbelow, is preferably formed from a cut tube so the struts are integral, however, in alternate embodiments, the struts are formed by separate elements, e.g., wires, strips, etc., that are bonded or welded together to form the strut pattern of  FIG. 20 . 
     In the normal position of the device  2010 , the device  2010  by way of example can have an inner diameter of about 2 mm to about 8 mm, and preferably about 4 mm, and an outer diameter of about 2.2 mm to about 9 mm, and preferably about 4.4 mm. The device  2010  can be compressed to an outer diameter of about 1 mm to about 4 mm, and preferably about 2 mm for delivery and then allowed to expand to its original position. Other diameters are also contemplated. 
     The conduit portion of the flow connector can, by way of example, have an inner diameter of about 1.5 mm to about 7.5 mm, and preferably about 3.5 mm, and an outer diameter of about 2 mm to about 8 mm, and preferably about 4.0 mm. 
     An alternate embodiment of the hook configuration is illustrated in  FIG. 31 . The securement/retention device is designated generally by reference numeral  2050  and is identical to device  2010  except for the hook configuration. Therefore, the retention device  2050  has a first (distal) set of V-shaped struts  2060  and a second (proximal) set of V-shaped struts  2062 , each set  2060  and  2062  extends around 360 degrees to form a closed ring as in device  2010 . The sets  2060  and  2062  are joined at their vertices, designated as region  2064  and form substantially diamond shaped openings  2066 . The device  2060  also has a series of tines  2070  identical to tines  2030  of  FIG. 20  which extend from distal vertices  2068  of distal struts  2060 . Further details of the device  2060 , other than the hooks  2070  will not be further described herein, since device  2060  and  2010  differ only in the hook design. 
     A longitudinally proximally extending strut  2074  extends from the proximal vertices  2072  of the proximal set of struts  2062 . The proximal end of the elongated strut  2074  branches outwardly into opposing directions, forming barb shaped hooks  2076 , rather than the U-shaped hooks of  FIG. 20 . More specifically, each branch  2078  extends outwardly from strut  2074  and then curves distally so the hooks  2076  point in a distal direction. The hooks  2076  terminate in penetrating (sharpened) tips  2079 . Although a hook  2076  extends from each proximal strut  2062 , it is also contemplated that a fewer number of hooks  2076  could be provided. 
     The method of insertion of the flow connector and retention device of  FIG. 20  will now be described with reference to  FIGS. 23-29 . Note the method is described for attaching a vein to an artery, however, connection of spaces within the body including, grafts, other conduits, etc. are also contemplated. The device of  FIG. 31  would be inserted in an identical manner. 
     First, as shown in  FIG. 23 , after an opening A is made in the arterial wall B of the artery, the retention device  2010 , contained in a compressed (collapsed) position within a cannula C to reduce its profile for insertion, is moved toward the vessel opening A. Note in some embodiments, depending on the internal diameter of the cannula and/or the outward extension of the tines  2030 , the tines  2030  are compressed by the cannula wall to a more straightened position. Note also in the compressed position the hooks  2028  maintain their curved configuration. However, it is also contemplated that the hooks in the compressed configuration could be maintained in a more straightened position and return to their curved position when released from the cannula C. Materials such as shape memory Nitinol could be used to achieve this. 
     The cannula C is placed adjacent, in abutment with or slightly into the opening A and a pusher D is advanced distally to advance the device  2010  through the opening A and into the artery lumen as shown in  FIG. 24 . In a preferred method, however, the cannula C would be inserted through the opening A and into the lumen of the artery with the retention device  2010  contained inside and then the pusher D advanced to move the retention device  2010  out of the confines of the cannula. In either case, after the proximal portion of the retention device  2010 , with the hooks  2028 , is positioned within the vessel lumen, the cannula C is removed and the retention device  2010  returns (expands) to its original, non-compressed position as shown in  FIG. 25 . The retention device  2010  preferably applies a radial force around the opening A of the artery to facilitate insertion of the flow connector delivery sheath. 
     With the hooks  2028  within the vessel lumen, the flow connector  100 A is inserted through the axial opening  2031  in retention device  2020  as shown in  FIG. 26 . In the illustrated method, the flow connector  100 A is inserted through the retention device  2010  before the retention device  2010  is pulled away (retracted) for the hooks  2028  to penetrate the vessel wall B. However, it is also contemplated in an alternate insertion method, that the retention device  2010  is first retracted so the hooks  2028  penetrate the vessel wall B prior to insertion of the flow connector  100 A. In this version, cannula C is moved proximally with proximal portions of the retention device  2010  contained therein to move the hooks  2028  distally to penetrate the vessel wall (as in the hook position of  FIG. 28 ) prior to insertion of the flow connector  100 A. 
     Returning to  FIG. 26 , the flow connector  100 A is contained in a folded or collapsed low profile insertion position within a delivery sheath F. Note that the flange  102 A of the flow connector  100 A is positioned within the vessel lumen, extending distally beyond the hooks  2028  of retention device  2010 . The flow connector  100 A, when released from the delivery sheath F by advancement of pusher G, expands toward its original diameter such that the outer diameter is slightly greater than the inner diameter of the retention device  2010  to provide a slight radial outward force against the retention device  2010  to provide an interference fit to hold the two together as shown in  FIG. 27 . In an exemplary embodiment, the outer diameter of the flow connector could be between about 2 mm and about 8 mm, and preferably about 4 mm. With the flow connector  100 A and retention device  2010  held together, the unit is pulled away as shown in  FIG. 28  so the hooks  2028  engage and penetrate the vessel wall adjacent the vessel opening A. As shown, the hooks  2028  surround the opening and extend 360 degrees around the opening. Note in this position, the elongated struts  2026  are positioned external of the vessel B. As noted above, it an alternate embodiment, the hooks would already be in position prior to insertion of the flow connector  100 A. 
     Next the vein V which is intended to be connected to the artery B to provide a fluid connection (communication) is placed over the outer wall of the retention device  2010  as shown in  FIGS. 29 and 30 . That is, the proximal end of the vein V is placed over the retention device  2010 , and pulled (stretched) over the retention device  2010 . Note the tines  2030  can be flexed inwardly by the vein V until in the desired position. Once fully positioned over the retention device  2010 , the penetrating ends  2032  of the tines  2030  penetrate the wall of the vein V to retain the vein V thereon. Thus, the tines  2030  secure the vein V to the retention device  2010  which is secured to the artery B via hooks  2028 . Fluid flow is then allowed between the two vessels, which are now connected to form an end to side anastomosis. Note that the retention device  2020 , by holding the vessels B and V in place also helps to maintain the flow connector  100  in place so the flow connector  100  can maintain the fluid tight seal between the flange  100 A of the implantable flow connector  100  and the wall of the artery B. This seal is described in detail above with respect to the discussion of the flow connector flange. 
     Note that the flow connectors  100   a  illustrated and described herein are substantially identical to the flow connector  100  of  FIG. 1A  in that it has a conduit  104   a  and a flange  102   a,  identical to conduit  104  and flange  102 , except since it does not require suture attachment, it need not be provided with protrusions as shown in  FIG. 1C . 
       FIGS. 47-51  illustrate an alternate embodiment of an internal retention/securement device. In this embodiment, instead of a one piece retention device placed internally, two pieces, one attached to the first space within the body, e.g. the artery (source element), and the other attached to the second space within the body, e.g., the vein (destination element), are provided and are connected in situ. It should be appreciated that if other body spaces are being connected, e.g., artificial grafts or other body conduits, one piece would be attached to one body space and the other piece to the other body space to join the two body spaces. 
     More particularly, the retention device of  FIGS. 47-51  is designated generally by reference numeral  4010 . Retention device  4010  has a first proximal component or member  4012  for attachment to the first body space, e.g., an artery, and a second distal component or member  4040  for attachment to the second body space, e.g., the vein. Proximal component  4012  has a distal end  4018  and a proximal end  4016 . The proximal component  4012  is substantially identical to retention device  2010 , except for the tines  4030 , and has a strut pattern forming a first (distal) set of joined V-shaped struts  4020 , a second (proximal) set of V-shaped struts  4022 , substantially diamond shaped openings  4036 , regions  4037  where the distal vertex of proximal struts  4022  are joined with the proximal vertex of distal struts  4020 , an elongated strut  4026  extending from the proximal vertex  4027  of the proximal struts  4022 , and hooks  4028  with penetrating tips  4029  extending from elongated struts  4026 . Since these components are identical to those of  FIG. 20 , further discussion of these components is not necessary since their configuration, structure and function can be understood by reference to the description of the retention device  2010  of  FIG. 20 . Also note as in the discussion of the other embodiments herein, for clarity, not all identical parts are labeled. 
     Locking members  4030  extend from alternating distal vertices  4031  of the distal struts  4020  and perform a different function than tines  2030  of retention device  2010 . More specifically, locking members  4030 , which extend radially outwardly from device  4010 , are configured to engage slots formed in the distal component  4040  as described below. Note the locking members  4030  can also be configured of sufficient length and have penetrating tips to engage and penetrate the second body space to provide supplemental retention of the second body space. In this configuration, the locking members would then also function as wall penetrating tines and would be similar to tines  2030  of retention device  2010 . 
     The distal component  4040 , like the proximal component  4012 , is formed from a cut tube, preferably laser cut, although other cutting methods are contemplated. Distal component  4040  has a distal end  4042  and a proximal end  4044 . A series of solid wall portions  4045  connected by a web  4046 . The solid wall portions  4045  have substantially triangular regions and substantially rectangular regions. More particularly, the more distal regions are somewhat triangular with sides  4048   a,    4048   b  extending proximally from vertex  4049 . After angling outwardly in triangular-like form, the sides  4048   a,    4048   b  each extend proximally in substantially linear sides  4050   a    4050   b,  forming a substantially rectangular region. Elongated axial slots  4060  extend distally from the proximal edges and terminate in radial slot  4062  to receive locking members  4030  of proximal component  4012  as described below. Alternatively, upper (distal) slot  4064  can receive locking members  4030  of component  4012 , also described below. Structure can also be provided so that the proximal component  4012  interlocks with structure at vertex  4046  of distal component  4040  or with other regions of distal component  4040 . 
     Note that that the components  4012 ,  4040  can be moved in the opposite direction, e.g., distal component  4040  moved distally with respect to proximal component  4012 , to disengage the locking members  4030  to release the components  4012 ,  4040  from the interlocked position to allow removal of the flow connector if desired. 
     A series of interconnecting V-shaped struts  4052 , at distal end  4042 , have distal vertices  4054  and proximal vertices  4056 . Extending proximally and radially outwardly from each of the distal vertices  4054  is a tine  4058  with a penetrating tip  4059 , substantially identical to tines  2030  of retention device  2012  and configured to engage and penetrate the wall of the second body space placed thereover. 
     In use, with reference to  FIGS. 49-51 , proximal component  4012  is inserted through an opening in the first body space, e.g., artery B, in the same manner as described above with respect to  FIGS. 24 and 25 , i.e., inserted through a cannula, like cannula C, so the hooks  4028  are positioned in the lumen of the artery B. The cannula C is then withdrawn in the same manner as described above with respect to  FIG. 25 , and the flow connector  100   a  is inserted through the axial opening in the proximal component  4012  in the same manner as described above in conjunction with  FIG. 26  above, i.e., inserted in a folded or collapsed position through a delivery sheath like delivery sheath F, and then the delivery sheath is withdrawn, leaving the flange  102   a  of the flow connector  100   a  positioned in the lumen of the artery B in the same manner as in  FIG. 27 . This positioning of the flow connector and distal component is shown in  FIG. 49 . 
     A second body space, e.g., a vein V, is placed over the distal component  4040  as in  FIG. 49 , and together placed over the proximal component  4012  as shown in  FIG. 50 . (Note it is also contemplated that the vein V is placed over component  4040  before component  4012  is placed in the artery). The distal and proximal components  4040  and  4012  interlock, preferably releasably interlock, as the locking members  4030  extend through upper (distal) slots  4064  and are held within the widened slot area  4064   a  due to the narrowing of the slot (slot area  4064   b ) above the widened area  4064   a.  That is, as the two components are moved together, the locking members  4030  are forced through the narrowed slot area  4064   b  into the widened slot area  4064   a  (see  FIG. 50 ). It should also be appreciated, that in an alternate embodiment, the locking members  4030  could engage the lower (proximal) slots  4062  and held therein by the proximal wall  4062   a  and narrowed slot  4060 . With the two components  4012  and  4040  interlocked as shown, and with the flow connector  100   a  applying an outward radial force on the retention device  4010 , the device  4010  and flow connector  100   a  are retracted so that penetrating hooks  4029  of hooks  4028  penetrate the wall of the artery B as shown in  FIG. 51 . Note that alternatively, the proximal component  4012  and flow connector  100   a  positioned therein can be retracted first so the hooks penetrate the artery wall, and then the distal component  4040  (with attached vein V) can be interlocked with the proximal component  4012 . In either case, the interlocking of the components  4040  and  4012  retains the flow connector  100   a  and artery B and vein V in position to achieve an end to side anastomosis which fluidly connects the artery B and vein V and maintains the above described fluid tight seal. 
       FIGS. 42-46  illustrate an alternate embodiment of a retention device. In this embodiment, a one piece retention device is provided, however, the flow connector and retention device are provided as a single unit. That is, instead of the user having to place the flow connector through the retention device in a separate step, the flow connector and retention device are already attached so the user can insert the flow connector and retention device together through the vessel opening. In this embodiment, the retention device is encapsulated in a polymer material of the fluid connector so there is no need for a separate retention device or the need for the additional steps of pre-inserting a retention device or of attaching a retention device. 
     The device, or implant, of this embodiment is designated generally by reference numeral  5010  and has an integrated flow connector and retention device. Stated another way, the flow connector  100   b  includes a conduit  104   b  similar to the conduit  104  of  FIG. 1A , a flange  102   b  similar to the flange  102  of  FIG. 1A , and a retention portion  5012  having a strut pattern embedded between the inner and outer walls  107   b,    109   b  of the conduit  104   b.  The flow connector  100   b  is similar to the flow connector  100  of  FIG. 1A  in that it has a conduit  104   b  and a flange  102   b,  identical to conduit  104  and flange  102 , except as in the other embodiments herein that do not require suture attachment, it need not be provided with protrusions as shown in  FIG. 1C . The device  5010  as noted above provides the flow connector  100   b  formed integrally with the retention device  5012 . Such integration can be achieved by various methods such as overmolding, dip forming, etc. Additional details of the flow connector  100   b  are not discussed herein as they are substantially identical to that of flow connector  100 . 
     The retention portion  5012  has a distal end  5014  and a proximal end  5024 . Retention device  5012  is formed from a series of struts forming two rings of substantially diamond shaped openings—substantially diamond shaped openings  5020  being in the distal ring and substantially diamond shaped openings  5022  being in the proximal ring. These openings  5020 ,  5022  are formed by the strut pattern shown in  FIG. 42  which has a first (distal) set of interconnected V-shaped struts  5026 , a second (proximal) set of interconnected V-shaped struts  5028  oriented in the same direction as the distal struts  5026  and an intermediate set of interconnecting V-shaped struts  5030  oriented in the opposite direction of the proximal and distal struts  5028 ,  5026 . The proximal vertices  5032  of the distal struts  5026  are joined to the distal vertices  5034  of intermediate struts  5030  and the distal vertices  5036  of proximal struts  5028  are joined to the proximal vertices  5038  of intermediate struts  5030 . An elongated strut  5040  extends from the proximal vertex  5042  of the proximal struts  5028 , terminating in vessel penetrating hooks  5044  with penetrating tips  5046  similar to hooks  2028  of  FIG. 20 . A set of tines  5048  with penetrating tips  5049  extend radially outwardly and proximally from the distal vertices  5035  of distal struts  5026 . The strut pattern can be formed by cutting, e.g., laser cutting, a tube. Note for clarity, not all identical parts are labeled in the drawings. 
     In use, the device (implant) or implantable flow connector  5010  is inserted into the first space within the body, e.g., artery B, through a delivery sheath, such as delivery sheath F of  FIG. 26 . When delivery sheath F is withdrawn as in the manner described above with respect to the embodiment of  FIGS. 20-31 , the device  5010  moves from its reduced profile insertion position to its original position. With the flange  102   b  positioned in the lumen of the artery B, a second body space, e.g., vein V, is positioned over the device as shown in  FIG. 45 , with the tines  5048  penetrating the wall of the vein V when the vein V is in position. The device  5010  is then pulled proximally as shown in  FIG. 46 , with the hooks  5044  penetrating the wall of the artery B around the opening, e.g., circumferentially around the opening as in the other embodiments described herein, thereby securing together and fluidly coupling the vein V and artery B forming a seal tight end to side anastomosis as with the other embodiments described below. Note that the method also contemplates that the device  5010  is first retracted so the hooks  5044  penetrate the artery wall B, and then the vein V is placed over the device  5010 . 
     Turning now to the embodiments wherein the securement/retention devices are placed external of the body space rather than internal of the body space as in the embodiments described above, reference is initially made to the embodiment of  FIGS. 32-41 . With reference to  FIGS. 32 and 33 , retention device  3010  includes a first outer body member or component  3012  and a second inner body member or component  3014  which are connectable or lockable together as described below. In use, the retention device  3010  is placed on the outer surface of the second body space, e.g., vein, rather than internal of the vein as in the embodiments of  FIGS. 20-31 . The inner body member  3014  receives within its axial opening the second body space which is positioned over the flow connector, and the outer body member  3012  engages the first body space, e.g., the artery, and is slidable along the outer surface of the inner body member  3012  to lockingly engage the inner body member  3012 , thereby securing the flow connector and retaining the first and second body spaces, e.g., the artery and vein, so the flow connector can sealingly fluidly couple the body spaces. The inner and outer members  3012 ,  3014  can be packaged pre-assembled or alternatively assembled by the user. 
     With reference to  FIGS. 32-36 , outer body member  3012  has a proximal portion  3016 , a distal portion  3018  and an intermediate portion  3020 . The outer body member  3012  is substantially C-shaped, extending in an arc of about 180 degrees (although arcs of other degrees are contemplated) and slides along the outer surface of the inner body member  3014 . Outer body member  3012  is preferably formed from a tube, cut to form the illustrated strut pattern, such as by laser cutting or other methods. The strut pattern includes first and second (proximal and distal) radial struts  3022 ,  3024 , separated by axial struts or walls  3026 , forming five closed geometric shapes or windows—two outer windows  3028   a,  two inner windows  3028   b  and an intermediate window  3028   c  between the two inner windows  3028   b.  Outer windows  3028   a  include inner region  3029   a  and outer region  3029   b,  with outer region  3029   b  raised with respect to inner region  3029   a  to form a ledge  3030 . Outer region  3029   b  extends distal of wall  3031  of inner region  3029   a  to form an elongated slot region  3029   c.  The configuration of the windows  3028   a - c  provides for sliding movement of the outer component  3012  with respect to the inner component  3014  in the manner described below. Note the edges of the windows  3028   a - 3028   c  are substantially linear. However, alternatively, one or more of the edges could be radiused, 
     Each of the two inner windows  3028   b  has a compression member, illustratively in the form of a U-shaped spring  3032 , positioned therein, with the base of the U extending proximally and the arms  3036  of the U curving in a somewhat S-shape into the axial struts  3026 . The springs  3032  deflect when the inner and outer components  3014 .  3012  are interlocked in the manner described below. 
     Proximal radial struts  3022  have a distal wall  3022   a  which is configured to engage a portion of the inner body  3014  to limit relative movement of the components as described below. 
     The axial struts  3026  extend proximally beyond the proximal radial strut  3022  and terminate in a hook or spike  3036 , extending radially inwardly to engage the first body space, e.g., the artery, as described below. The hook  3036  terminates in a penetrating (sharpened) tip  3038  configured to penetrate the artery wall from the outside in (in contrast to the hooks  2028  of  FIG. 20  which penetrate the artery from the inside out). Although each axial strut  3026  is shown terminating in a hook  3036 , it is also contemplated that alternatively a fewer number of hooks could be provided such that not all axial struts terminate in hooks. 
     Turning now to the inner body member  3014 , this component has a distal portion  3040 , a proximal portion  3042  and an intermediate portion  3044 . Inner body member  3014  is preferably formed from a tube, cut to form the illustrated strut pattern, such as by laser cutting or other methods. The strut pattern forms a series axially stacked interleaved radially extending fingers  3050 . These interleaved fingers  3050  are positioned in radial openings  3055  formed in inner member  3014  and are positioned in an axial row. Note that the fingers  350  extend in alternating opposite directions so that the first (distalmost) and third fingers extend radially in a first direction and the second and fourth (proximalmost) fingers extend in an opposite second direction. Each of the fingers  3050  terminates in end region  3052  which as shown is spaced from the wall  3054  to form a gap  3056 . Each of the fingers  3050  has a series of elongated axially extending openings  3058  formed therein to reduce the mass of the inner body member  3014  and increase flexibility. Note that for clarity, not all identical features of the components have been labeled in the drawings. 
     The intermediate portion  3044  includes a pair of tool engagement tabs  3060 , located on opposite ends of the inner member  3014 , preferably spaced about 180 degrees apart. The engagement tabs  3060  extend radially outwardly from the inner body member  3014  and are configured to be engaged by a tool to move the inner body member  3014  from its normal position as shown in  FIG. 37  to an open (spread) position shown in  FIG. 39 , thereby opening the inner body member  3014  into a substantially C-shape configuration to provide an opening to receive therein a second body space, e.g., a vein, and attached flow connector as described below in the discussion of the method of use. Note when the inner body member  3014  is moved out of its 360 degree substantially cylindrical configuration, expanded to the position of  FIG. 39 , fingers  3050  move away from walls  3054  (see also  FIG. 38 ), and out of the radial opening  3055  to open the inner body member  3014 . Note the inner body member  3014  is made of material that enables it to return to its normal substantially cylindrical position after it is opened so it can clamp around the circumference of the second body space. One material that can be used is shape memory material, although other materials are also contemplated. 
     A series of ramps  3062  are positioned in the proximal portion  3042  of inner body member  3014 . The ramps  3062  extend radially outwardly from the inner body member  3014  and are spaced apart about the proximal portion. The ramps  3062  include a lower (proximal) edge  3062   a  to engage the distal wall  3022   a  of proximal radial strut  3022 . Note the proximal portion  3042  of inner body member  3014  preferably does not extend about the full 360 degrees as does the intermediate and distal portions  3044  and  3040 . This enables it to better accommodate the connection between the first and second body spaces since the second body space (and flow connector) is preferably connected at an angle to the first body space (see e.g.,  FIGS. 40 and 41 ). Inner body member  3014  further includes a series of reliefs  3072  formed in the proximal portion  3042 . These reliefs  3072  shield the hooks  3036  of the outer body member  3012  during delivery and deployment. Bent guide hooks  3066  of inner body member  3014  extend from the intermediate portion  3044  and engage axial struts  3026  of outer body member  3012  to provide guides for the outer body member  3012  as it slides along the inner body member  3014 . A pair of locking tabs  3070 , with a substantially planar upper surface  3071 , extend radially from the intermediate portion  4044  of the inner body member  3014  and engage the proximal surface of the spring  3032  of outer body member  3012  to lockingly engage the inner and outer body members  3014  and  3012  in the manner described below. 
     As shown in  FIG. 32 , in the initial position of the outer body member  3012  with respect to the inner body member  3014 , the proximal radial strut  3022  is blocked from proximal movement by the radially extending ramps  3060 . Also note in this position, the engagement tabs  3060  are in abutment with the ledges  3030  of outer windows  3028   a  and radially extending locking tabs  3070  of inner body member  3014  are positioned proximally of and out of contact with the U-shaped springs  3032 . Note also in this position, the hooks  3066  of outer body member  3012  are shielded within the reliefs  3072  of inner body member  3014 . Two of the axial struts  3026  are received in the opening formed in bent guide hooks  3066  so that the hooks  3066  serve as guides for the struts  3026  to help maintain alignment of the outer body member  3012  and facilitate its sliding movement with respect to the inner body member  3014 . 
     A series of other cutouts in the body of inner body member  3014  reduce the overall mass of the component and increase its flexibility. 
     Turning now to the method of insertion utilizing the retention device  3010  and with reference to  FIGS. 40 and 41 , the flow connector  100   a  is inserted through an opening in the first body space, e.g., an artery, through a cannula (not shown). The cannula is similar to the cannula C described above in  FIG. 26  and retains the flow connector  100   a  in the collapsed or reduced profile position. Note the insertion of the flow connector  100   a  differs from that of  FIG. 26  since in this embodiment it is being placed in the artery as in  FIGS. 3-5 , and does not pass through a retention device as in  FIG. 26 . Once placed in the artery and positioned so that flange  102   a  engages the internal wall of the artery B, the second body space, e.g., the vein V, is placed over the conduit portion of the flow connector  100   a.  Note that it is also contemplated that alternately the vein V is first placed over the flow connector  100   a  and then the flow connector is inserted into the artery B. 
     Once the flow connector  100   a  and vein V are positioned as shown in  FIG. 40 , retention device  3010  is moved to its open C-shaped position (see  FIG. 39 ) by a tool applying a force to engagement tabs  3060  and then placed about the outer wall of the vein V. The force on the tabs  3060  are then released, allowing the retention device  3010  to return to its normal closed position to clamp about the vein V. (Preferably the inner diameter of the retention device  3010  is slightly smaller than the outer diameter of the vein to provide an interference fit). Consequently, the vein V is positioned between an internal wall of the inner member  3014  and an external wall of the flow connector. (In contrast to the inner retention devices of  FIGS. 20 and 47  which are positioned so that the devices are between the external wall of the flow connector and the internal wall of the vein). 
     Once the retention device  3010  is positioned about the vein V to surround the circumference in a 360 degree arc, the outer body member  3012  is slid distally with respect to the inner member  3014  to lockingly engage the inner body member  3014  to prevent further movement. More specifically, as a force is applied to the outer body member  3012  to slide it proximally, proximal radial strut  3022  is forced over the inclined surface of ramps  3062 , forcing the ramps  3062  radially inwardly, and the axial struts  3076  are maintained in axial alignment by the guide hooks  3066  of inner member  3014 . The outer member  3012  is advanced sufficiently to advance radial strut  3022  past the ramps  3062 . Once passed the ramps, the ramps  3062  return to their initial position and the distal wall  3022   a  of radial strut  3022  engages the proximal surface  3062   a  of ramp  3062 . By this engagement, in this position, distal movement of the outer body member  3012  is prevented. Also, in this position, the U-shape spring  3032  of outer member  3012  and the tabs  3070  of inner member  3014  are engaged, with the tabs  3070  deflecting he springs  3032 , and the springs applying a force to return to their original shape. With this spring/tab and rail/ramp interaction, the outer and inner members  3014 ,  3012  are lockingly, and preferably releasingly lockingly, engaged. Note further that the hooks  3036  of the outer body member  3012  engage and penetrate the wall of the artery, extending through the artery wall from the outside into the inside. Consequently, with the inner and outer components  3014 ,  3012  lockingly engaged, the hooks of the outer component  2012  engaging the arterial wall, and the inner member  3014  clampingly engaging the vein V which is fit over the flow connector, the vein and artery are fluidly and sealingly connected forming a secure end to side anastomosis. 
     Note that the components  3014 ,  3012  can be moved in the opposite direction, e.g., the ramps  3062  pressed inwardly and the outer body member  3012  slid proximally to disengage from the interlocked position to allow removal of the flow connector if desired. 
       FIGS. 52-55  illustrate an alternate embodiment of an external retention device. This device differs from the retention devices of  FIG. 20-51  in that it is configured to receive a suture wherein the embodiments of of  FIGS. 20-51  as noted above, can provide a sutureless system if desired. The external securement/retention device of  FIG. 52  is designated generally by reference numeral  6010  and has a distal portion  6012 , a proximal portion  6014  and an intermediate portion  6016 . Retention device  6016  is somewhat similar to the inner body member  3014  of retention device  3010  of  FIG. 32  in that it has a series of radially extending interleaved fingers  6020 , except it differs from retention device  3010  in various respects. Retention device  6010  does not receive an outer member which is positioned in the first body space. Instead, retention device  6010  has at its proximal portion  6014  a plurality of radially extending tabs  6018  with a proximal undersurface configured to abut the external wall of the first body space, e.g., the artery. As shown, the tabs  6018  lie in a plane angled with respect to a longitudinal axis of the device  6010  to better conform to the outer wall of the first body space since the flow connector (and second body space e preferably positioned at an angle to the first body space as shown in  FIG. 55 . 
     As in the embodiment of  FIG. 32 , device  6010  is preferably formed from a tube, cut to form the illustrated strut pattern, such as by laser cutting or other methods. The strut pattern forms a series axially stacked interleaved radially extending fingers  6020 . These interleaved fingers  6020  are positioned in radial openings  6024  and are positioned in an axial row. The fingers  6020  extend in alternating opposite directions so that the first (distalalmost) and third fingers extend radially in a first direction and the second and fourth (proximalmost) finger extend in an opposite second direction. Each of the fingers  6020  terminates in end region  6022  which as shown is spaced from the wall  6025  to form a gap  6026 . Each of the fingers  6020  has a series of elongated axially extending openings  6028  formed therein to reduce the mass thereof and increase flexibility. Note that for clarity, not all identical features of the device  6010  have been labeled. 
     A series of tabs  6030  which have tips  6032  extending radially inwardly are configured to mate with an anastomotic connector  100   c  similar to the flow connector of  FIG. 1D  in that it has barbs or protrusions extending from the conduit portion. The tabs  6030  preferably engage the overlapping wall of the protrusions. As shown, the tabs  6030  are positioned such that within openings  6031  and  6032  two tabs  6030  extend toward each other. A similar arrangement of tabs  6030  is provided spaced about 90 degrees apart (see  FIG. 53 ). 
     A pair of tool engagement tabs  6034 , located on opposite ends of retention device  6010 , are preferably spaced about 180 degrees apart. The engagement tabs  6034  extend radially outwardly and are configured to be engaged by a tool to move the device  6010  from its normal position as shown in  FIG. 52  to a spread position shown in  FIG. 54  (in the same manner as described above with respect to  FIG. 39 ), thereby opening the device  6010  into a substantially C-shape configuration to provide an opening to receive a second body space, e.g., a vein, and attached flow connector, as described below in the discussion of the method of use. Note when the body is moved out of its 360 degree substantially cylindrical configuration, expanded to the position of  FIG. 54 , fingers  6020  move away from walls  6025 , and out of the openings  6024  to open the body member. Note the device  6010  is made of material that enables it to return to its normal substantially cylindrical position after it is opened so it clamps around the circumference of the second body space as its internal diameter is preferably slightly less than the outer diameter of the second body space. A shape memory material such as Nitinol can be used to achieve this, although other materials are also contemplated. 
     In use, the flow connector, e.g., flow connector  100   c,  similar to the flow connector of  FIG. 1D , is inserted into the first body space, e.g. artery B, with the flange  102   c  positioned in the body lumen in the same manner as in  FIG. 40 . After placement of flow connector  100   c,  the second body space, e.g. the vein, is placed over the flow connector  100   c.  (Alternatively, the vein could be placed over the flow connector before inserted into the artery). Next, tabs  6032  of device  6010  are pressed by a tool (not shown) to open the device  6010  from its substantially closed (substantially cylindrical) configuration to its open position so that the flow connector  100   c  and vein can be placed into the device  6010 . After such placement, the tabs  6032  are released, allowing the device  6010  to return to its original position to extend circumferentially around and clamp the vein against the flow connector with the tabs  6030  engaging the protrusions on the conduit portion of the flow connector  100   c,  thereby securely retaining the vein. The tabs  6018  of device  6010  remain external of the artery B, resting on the outer surface of the arterial wall. A suture  6040  is then applied through the vessel wall, interweaving between the tabs  6018 , i.e., the suture extends over one tab  6018  and into the vessel wall and then out from the vessel wall and over the next tab  6018 , etc., to secure the retention device  6010  to the artery B, thereby maintaining the flow connector  100   c  in position and maintaining a secure fluid connection between the artery B and vein V. 
     The method of implanting the flow connector, attaching the retention device and attaching the vein are described above. It should be appreciated that the retention devices and flow connector can be removed and placed at an alternate location one or multiple times if the user is not satisfied with the original placement. This can be achieved by removal of the retention devices and compression of the flow connector. In certain instances, it might be desirable to remove the flow connector and retention device altogether from the body. This can also be achieved by removing the retention device and compressing the flow connector to reduce its profile for withdrawal from the body. In the embodiments where the retention device includes two interlocking components, the components can be unlocked and separated to a non-interlocked position, and then re-interlocked if desired. This locking/unlocking can be repeated multiple times if necessary. 
     The retention devices disclosed herein can be used with any of the flow connectors described above. Additionally, the retention devices disclosed herein could have structure to engage the protrusions, recesses, or other irregular outer structure of the flow connectors of  FIGS. 11A-11Q . 
     The retention devices described herein can be packaged as a kit with one or more of the flow connectors. However, it is also contemplated that the retention devices can be packaged as a separate unit for utilization with any of the foregoing flow connectors as well as for utilization with other flow connectors or other implants. Still further, in some embodiments, the retention devices described herein can be used itself to couple first and second body spaces without the aforedescribed flow connectors. In these embodiments, the retention device would engage, both the first and second body spaces in the various manners discussed above, such as for example by penetrating members penetrating the wall of the body spaces, to enable fluid coupling of the body spaces or to otherwise join these two body spaces. To enable fluid coupling, in some embodiments, the flow connector can include a non-porous material positioned internal and/or external of the retention device. 
     It is to be understood that although embodiments of the present invention have been largely described as being used to connect two tissue-enclosed body spaces, for example veins and arteries, other embodiments of the present invention may be used to connect a body space to an artificial device, such as a pump, an artificial conduit connected to the flow connector  100  conduit, sensors, plugs, among others. 
     While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. All patents and publications discussed herein are incorporated in their entirety by reference thereto.