Patent Publication Number: US-6991615-B2

Title: Grafted network incorporating a multiple channel fluid flow connector

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of our co-pending application Ser. No. 10/698,253, filed Oct. 31, 2003 and entitled “GRAFTED NETWORK INCORPORATING A MULTIPLE CHANNEL FLUID FLOW CONNECTOR”, which itself is a continuation-in-part of our co-pending application Ser. No. 10/634,200, filed Aug. 5, 2003, entitled “GRAFTED NETWORK INCORPORATING A MULTIPLE CHANNEL FLUID FLOW CONNECTOR”, the contents of each is incorporated herein in its entirety. 

   FIELD OF THE INVENTION 
   The present invention relates to vascular graft networks generally, and more particularly to coronary graft networks incorporating one or more graft connectors that are specifically configured to efficiently transport bypass blood flow from a source to one or more delivery locations, which graft connectors may be directly implanted to the patient&#39;s vasculature at specific designated bypass locations. 
   BACKGROUND OF THE INVENTION 
   Coronary bypass surgery has become a common procedure, and is normally indicated for conditions requiring replacement and/or reconfiguration due to blockage of the coronary blood flow within a patient. To achieve such a bypass, grafts are surgically implanted to divert blood flow from a relatively high volume and pressure flow regime to a portion of the diseased vascular member downstream from the blockage therein. In typical bypass procedures, a section of the vascular system in a patient&#39;s body that has become impaired or inoperative through disease or other defects may be treated so as to improve flow to those portions previously being supplied with an inadequate or limited supply of blood. In order to create the graft bypass, biocompatible graft material is preferably employed, which graft material may be, for example, vascular members harvested from other portions of the patient&#39;s body or from other animals, or biocompatible artificial materials such as, for example, forms of polytetrafluoroethylene (commonly referred to as Teflon®). 
   While bypass procedures have been undertaken for some period of time, one particular and time consuming step is that of suturing the graft elements to respective portions of the patient&#39;s vasculature. Because of the physical properties of, in particular, artificial biocompatible graft material, suturing of such graft material is often times difficult to complete. The procedure is one which requires great dexterity, and when done at the site, is frequently in a zone with limited accessibility. Graft systems proposed to date have drawbacks with regard to ease of implantation and securement into the patient&#39;s vasculature. 
   An additional issue that is not satisfactorily addressed in existing bypass techniques is the inability of such techniques to effectively maintain flow and pressure from a blood flow source such as the aorta to the vascular member in which the bypass procedure is conducted. Specifically, the blood supply stream is typically in a high-pressure flow environment, while the vascular member subject to bypass flow is typically a low-pressure blood flow environment. Accordingly, the substantial pressure drop between the respective bypass blood flow locations generally results in low flow volumes to the artery or other vascular member to which bypass flow is directed. Previous attempts to provide sustained flow volumes to respective vascular members from a relatively high pressure source have been met with limited success, in that such systems proposed to date are difficult to manufacture and implement, and particularly difficult to produce positive reproducible implantation results. In particular, such prior systems fail to provide components that may be quickly and effectively implanted in the surgical process. 
   It is therefore a principle object of the present invention to provide a grafted network for consistently delivering sufficient blood flow volumes to respective vascular members in a bypass procedure. 
   It is a further object of the present invention to provide a grafted network incorporating distinct connector means for effectively channeling bypass blood flow into respective vascular members while minimizing damage to such vascular members and to such bypass blood flow. 
   It is a yet further object of the present invention to provide a grafted network incorporating one or more graft segments in combination with one or more distinct connector means for operably channeling bypass blood flow into respective vascular members. 
   It is another object of the present invention to provide a grafted network incorporating a plurality of graft segments, one or more distinct connector devices, and a flow restricting means for maintaining a desired level of blood flow pressure and volume through upstream graft segments and such connector devices into respective vascular members receiving bypass blood flow thereto. 
   It is a still further object of the present invention to provide a grafted network which may be expediently surgically implanted within the patient&#39;s body. 
   SUMMARY OF THE INVENTION 
   By means of the present invention, a grafted network is provided for enabling one or more coronary bypass procedures to be performed from a single relatively high fluid pressure source location. In addition, the grafted network of the present invention allows the bypass procedure to be performed directly at particular sites in the targeted vascular members requiring bypass blood flow thereto, with each of the direct sites being supplied with blood flow from a common singular bypass blood flow stream. Moreover, the grafted network of the present invention includes means for maintaining the supply bypass blood flow stream at high pressure while minimizing any turbulent flow effects through the grafted network, so as to consistently provide adequate bypass blood pressure and flow volume to each of the vascular members receiving such flow. 
   In a particular embodiment of the invention, one or more graft segments configured to operably transport bypass blood flow from a singular supply location to one or more delivery locations in a grafted network are provided in combination with one or more multiple channel blood flow connectors for directing such bypass blood flow in the grafted network to one or more vascular members. The blood flow connectors are configured for coupling, for example, first and second graft segments to a first vascular member defining a first blood flow delivery location. The blood flow connector preferably includes a supply conduit and a delivery conduit integrally formed therewith and adjacently disposed with respect to one another, with the supply conduit and the delivery conduit each having a distinct lumen formed therewithin. The supply conduit of the blood flow connector preferably includes at least a first open end, and more preferably first and second opposed open ends having annular recessed portions and annular lips for operably attaching respective open ends of the first and second graft segments thereto. The supply lumen and the delivery lumen are fluidly connected to one another through cooperating apertures in respective outer walls of the supply conduit and the delivery conduit at an intersection therebetween so as to provide for immediate bypass blood flow from the supply lumen to the delivery lumen. The delivery conduit includes at least one open end portion extending from the intersection and beyond an outer perpendicular tangential plane of the supply conduit outer wall at a lateral side thereof with respect to the intersection, such that a first open end of the delivery conduit is laterally spaced from, and extends beyond, a perpendicular tangent plane of the supply conduit outer wall. The delivery conduit is preferably configured for operable implantation directly into the targeted vascular member so as to provide bypass blood flow thereto. The delivery conduit may be specifically sized to provide internal structural support for the targeted vascular member when the delivery conduit is implanted therein. Such internal structural support is preferably provided without damage to the vascular member, as commonly occurs with stent devices. 
   In preferred embodiments of the present invention, a throttle device is provided in the grafted network downstream from the most-downstream bypass location, and adjacent to the low pressure vessel or anatomical site. The throttle device is operably coupled to the grafted network and is disposed between the last blood flow connector and a terminal delivery location for the grafted network of the present invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front perspective view of a grafted network of the present invention employing a plurality of multiple channel blood flow connectors. 
       FIG. 2  is a schematic view of certain elements of the grafted network of the present invention. 
       FIG. 3  is a front elevational view of a blood flow connector device of the present invention. 
       FIG. 4  is a bottom view of the connector device illustrated in  FIG. 3 . 
       FIG. 5  is a front elevational view of a throttle device of the present invention. 
       FIG. 6  is a side cross-sectional view of the throttle device illustrated in  FIG. 5 . 
       FIG. 7  is a partial cut-away view of a blood flow connector device of the present invention. 
       FIG. 8  is a partial cut-away view of a blood flow connector device of the present invention. 
       FIG. 9  is a partial cross-sectional view of a portion of the blood flow connector device of the present invention. 
       FIG. 10  is a partial cutaway view of a blood flow connector device of the present invention. 
       FIG. 11  is a perspective view of a blood flow connector device of the present invention. 
       FIG. 12  is a perspective view of a blood flow connector device of the present invention. 
       FIG. 13  is a side-elevation view of a blood flow connector device of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The objects and advantages enumerated above together with other objects, features, and advances represented by the present invention will now be presented in terms of detailed embodiments described with reference to the attached drawing figures which are intended to be representative of various possible configurations of the invention. Other embodiments and aspects of the invention are recognized as being within the grasp of those having ordinary skill in the art. 
   With reference to the enclosed drawing figures, and first to  FIG. 1 , a grafted network  10  includes a first graft segment  11  that is preferably attached by suture to a relatively high-pressure blood flow environment such as the aorta of a patient&#39;s heart, such as at location  12 . Such location  12  comprises a singular supply location for directing blood through network  10  to one or more vascular members, such as coronary arteries  14 . 
   As illustrated in  FIG. 1 , first graft segment  11  is preferably secured to connector  13 , which is described in greater detail hereinbelow. Connector  13  is preferably configured so as to direct a portion of the blood flow passing from supply location  12  and through first graft segment  11  into a respective coronary artery  14 . To accomplish the desired channeling of at least a portion of the blood flow, connector  13  preferably includes distinct conduits associated therewith, with at least one of such conduits being implantable into the respective vascular member, and particularly into coronary artery  14 . Preferably, a second graft segment  16  is operably coupled to a downstream side of connector  13 , with connector  13  being configured to convey a portion of the blood flow within first graft segment  11  to second graft segment  16 . In the embodiment illustrated in  FIG. 1 , second graft segment  16  is operably coupled to a second connector  13 A to thereby operably convey a portion of the blood flow within second graft segment  16  into a second artery  14  to which second connector  13 A is operably coupled. 
   In preferred embodiments of the present invention, grafted network  10  further includes a third graft segment  18  which is operably coupled to a downstream end of second connector  13 A so as to transport remaining blood flow therefrom. In some embodiments, third graft segment  18  is operably coupled to a terminal delivery location  20  through suturing or the like. Terminal delivery location  20  may be a vascular member, and is preferably a relatively low pressure vessel or anatomical site such as an atrium or vena cava of the patient&#39;s heart. In preferred embodiments, however, and as illustrated in  FIG. 2 , a flow restricting means  22  is operably disposed between terminal delivery location  20  and the final and most downstream connector  13  in network  10 . Flow restricting means  22  is preferably a distinct throttle device that is secured within a respective grafted segment  18 , and is configured to restrict the volume of flow passing therethrough so as to maintain relatively higher pressure upstream therefrom. In addition, blood flow exiting flow restricting means  22  is preferably at a relatively low fluid pressure so as to blend into the blood channels formed by the atrium or vena cava without excessive turbulent flow effects. Of course, graft segment portion  24  which transports blood flow from a downstream end of flow restricting means  22  to terminal delivery location  20 , carries only that blood which does not otherwise pass from network  10  to a respective coronary artery  14 . 
   In some embodiments of the present invention, flow restricting means  22  may be secured between adjacent grafted segments, with a first grafted segment being operably coupled to a first open end of flow restricting means  22 , with a second graft segment being operably coupled to a second downstream open end of flow restricting means  22 . In still further embodiments of the present invention, flow restricting means  22  may be integrally formed within a respective graft segment  18 , such that a portion of graft segment  18  includes a reduced internal diameter profile akin to that of flow restricting means  22 . In such an embodiment, an entire workpiece may be formed through extrusion or other molding processes to produce a single element having a flow restricting means  22  integrally formed therewith. 
   Preferably, network  10  provides a means for efficiently performing one or more bypass procedures with a modular apparatus having any desired number of vascular member connectors  13  and graft segments fluidly coupling such connectors  13  to one another, as well as to at least a singular supply location  12 , and preferably a terminal delivery location  20 . The respective graft segments of network  10  are preferably fabricated from a biocompatible material that is somewhat elastic and is easy to manipulate by the surgeon. A particularly preferred material for use in manufacturing the graft segments is ePTFE, which is a form of polytetrafluoroethylene, and is widely known as a type of Teflon® material. The ePTFE segments are biocompatible, in that the body does not recognize such material as a “foreign” object, and therefore does not react negatively to its presence. Furthermore, the ePTFE material is capable of being formed into tubing of substantially any desired size, and extruded to a desired degree of surface smoothness. The biocompatible characteristics minimizes the likelihood of clot formation, while the intra-wall porosity improves the endothelialization of the ePTFE. Though variants of polytetrafluoroethylene are most desired in forming the graft segments of the present invention, other artificial or natural materials are also contemplated for use in the graft segments. For example, vascular material harvested from a patient&#39;s own body, or vascular materials harvested from other living beings may be used as implantable graft segments in network  10 . A particular disadvantage of utilizing vascular materials harvested from patient&#39;s own body is that of additional recovery time and discomfort for the patient as well as progressive vessel disease incurred as a result of utilizing a vessel previously exposed to physiological effects. Accordingly, artificial biocompatible materials are most preferred to minimize the degree of invasiveness into the patient to accomplish the bypass procedures as to minimize the likelihood of natural blockage issues in the graft material. 
   As is best illustrated in  FIG. 3 , blood flow connector  13  is preferably a distinct unit having a plurality of blood flow channels for operably directing and channeling blood flow to pre-determined locations, most preferably into targeted vascular members. Blood flow connector  13  includes a supply conduit  32  and a delivery conduit  34  integrally formed therewith and adjacently disposed with respect to one another. Though blood flow connector  13  is presently shown and described as having a single supply conduit and a single delivery conduit, variations of such a design are also contemplated by the present invention. Namely, such supply and/or delivery conduits may be branched into a plurality of distinct conduits, or, alternatively, a plurality of individual supply conduits and/or delivery conduits may be integrally formed in adjacent relationship with one another in a single connector unit. 
   Supply conduit  32  includes at least a first open end  38 , and preferably includes first and second opposed open ends  38 ,  40  which, in combination, define an axially extending supply lumen  42  defined within the inner annular wall of supply conduit  32 . Preferably, a respective graft segment  11  is operably secured to first open end  38  of supply conduit  32 . In embodiments of supply conduit  32  incorporating both first and second open ends  38 ,  40 , a second graft segment, such as graft segment  16 , is operably secured to second open end  40 . 
   In preferred embodiments, supply conduit  32  includes annular recessed portions or grooves  46  disposed in an outer surface thereof and adjacent to respective open ends  38 ,  40 . Such recessed portions  46  are specifically configured to assist in obtaining a secure attachment between respective graft segments and supply conduit  32 . As illustrated in  FIG. 3 , annular recessed portions  46  provide a locating zone at which to suture an open end of a respective graft segment therearound, in that such sutures may circumferentially bind open ends of the respective graft segments to respective annular recessed portions  46 . Furthermore, such annular recessed portions  46  define respective outer lips  48  at respective open ends  38 ,  40  of supply conduit  32 . In operation, sutures circumferentially retaining respective graft segments to annular recessed portions  46  are further held axially in place by outer lips  48  which create a friction fit with respect to the graft segments. Annular recessed portions  46  and outer lips  48 , in combination, collectively form coupling means for assisting in the graft sutures process to supply conduit  32 . 
   Delivery conduit  34  is preferably adjacently disposed to supply conduit  32 , and preferably is integrally formed with supply conduit  32 . Supply conduit  34  is preferably a hollow body, such that supply conduit  34  contains a distinct supply lumen  52  therewithin. In some embodiments of the present invention, delivery conduit  34  includes coupling means  54  akin to annular recessed portions  46  and outer lips  48 . In other embodiments of the present invention, however, coupling means  54  on delivery conduit  34  includes an annular flange extension disposed about respective end portions of delivery conduit  34 . 
   Preferably, delivery conduit  34  includes at least one open end  56  and end portion  58  laterally extending beyond an outer perpendicular tangential plane of supply conduit  32  at a lateral side thereof with respect to the intersection between supply conduit  32  and delivery conduit  34 , such that when end portion  58  is operably positioned within a respective vascular member such as artery  14 , the surgeon may quickly and easily suture artery  14  to end portion  58  without significant manipulation of connector  13 , and without substantial interference from supply conduit  32  during the suturing process. In embodiments wherein delivery conduit  34  includes only one open end  56 , all blood flow directed into the associated artery  14  exits through open end  56 , as indicated by arrow  60 . In other embodiments of the present invention, delivery conduit  34  includes first and second open ends  56 ,  62 , with second end  62  forming a portion of end portion  64 . Such embodiments are incorporated for applications in which bypass blood flow out from first and second end portions  58 ,  64  of delivery conduit  34  is desired. 
   As is best illustrated in  FIG. 4 , supply conduit  32  and delivery conduit  34  each include respective apertures  33 ,  35  disposed in integrally adjacent outer walls, such that respective apertures  33 ,  35  intersect and superimpose with one another such that supply lumen  42  and delivery lumen  52  are fluidly coupled to one another. Specifically, bypass blood flow entering first open end  38  of supply conduit  32  is transported in and through supply lumen  42 , and to coordinating apertures  33 ,  35  of supply conduit  32  and delivery conduit  34 . At least a portion of such bypass blood flow accordingly passes through coordinating apertures  33 ,  35 , and correspondingly exits through one or more of open ends  56  and/or  62  of delivery lumen  52 . Preferably, respective apertures  33 ,  35  are integrally formed with one another, so as to form a single unitary aperture fluidly coupling supply lumen  42  and delivery lumen  52 . Such coordinating apertures preferably include radiused edges so as to minimize stresses placed upon blood passing therethrough, as well as to minimize turbulent fluid flow effects. Cooperating apertures  33 ,  35 , in combination, define an intersection between supply conduit  32  and delivery conduit  34 , with a central midpoint of such cooperating apertures  33 ,  35  defining a central intersection plane  65  referred to herein. 
   Blood flow connector  13  is preferably fabricated from a biocompatible material that is sufficiently strong and durable to withstand stress forces incorporated during implantation and eventually within the patient&#39;s body. A particularly preferred material for use in blood flow  13  is titanium, though a variety of other materials may be utilized instead. An alternative material for use in the fabrication of connector  13  is a polytetrafluoroethylene such as ePTFE. In addition, other biocompatible materials not specifically stated herein are also contemplated as alternative materials for use in blood flow connector  13  and/or flow restricting means  22 . 
   As illustrated in  FIGS. 1–2 , connector  13  is preferably configured such that delivery conduit  34  may be directly implanted into a selected portion of the patient&#39;s vasculature, and preferably adjacent to, and downstream from, a blockage or other diseased portion of the particular vascular member. In such a manner, grafted network  10  may be implanted and surgically connected to the patient&#39;s vasculature directly, and without separate intravascular procedures. Therefore, the surgeon is able to create a distinct bypass (delivery) location in a selected vascular member by making a relatively small incision thereto at the selected site. The surgeon is then able to manipulate connector  13  so as insert delivery lumen  34  within the respective vascular member for blood conduction thereto. It is a particularly preferred aspect of the present invention to provide delivery conduit  34  with an outer dimension of a size somewhat smaller than the internal diameter of the particular vascular member in which the bypass procedure is being conducted. Preferably, the outer diameter of delivery conduit  34  is about 80% of the corresponding inside diameter of the associated vascular member. The particular sizing described above with respect to delivery conduit  34  is preferred so as to limit damage to the vascular member caused by implantation of delivery conduit therein. 
   In some procedures, a separate and distinct expandable or fixed-configuration stent device is implanted into the vascular member in order to provide structural support to the vascular member after its structure has been compromised by a medical procedure performed thereon. Typical stent devices create substantial expansive forces on the respective vessel walls and in some cases generate excessive internal pressure on the vessel. Accordingly, delivery conduit  34  of the present invention acts both as a means for directing blood flow from grafted network  10  into a particular vascular member, as well as to structurally support such vascular member from therewithin without excessively straining the respective vessel wall. Such structural support operably maintains the associated vascular member in an open orientation and substantially prevents collapse thereof at the implantation location. 
   The foregoing description of the configuration and sizing of delivery conduit  34  may also be incorporated into supply conduit  32  for a preferred selected securement to respective graft segments. As indicated above, the preferred ePTFE material making up the respective graft segments is somewhat malleable in nature, and can therefore be configurationally modified by the surgeon during the implantation procedure. Preferably, respective open ends of the graft segments being operably secured to supply conduit  32  are modified with an appropriately-sized tool or a manual rolling manipulation that enlarges the inside diameter of an end portion of the respective graft segments being fitted onto respective ends on supply conduit  32 . In such a manner, latent restorative forces within the respective graft segments act to compress upon respective outer surfaces of supply conduit  32 , so as to obtain a snug connection thereto. 
   In preferred embodiments of the present invention, one or more components of the apparatus of the present invention may be coated on at least inner surfaces thereof with biocompatible material or made of mixed biocompatible material to further reduce any biological incompatibility issues. In particular, such biocompatible and/or drug eluting coatings are preferably disposed on at least inner surfaces of connector  13 , though such biocompatible coatings may be placed upon any or all surfaces of grafted network  10 . A particular biocompatible coating contemplated for use in the present invention includes a multi-layer biocompatible coating including silane, polyvinylpyrrolidine (PVP), heparin, and a photo-reactive cross-linking agent. In particular, a first layer contains isopropylalcohol (IPA), a second layer having a hydrophilic material such as PVP and IPA, and a third layer having PVP and heparin. Such a biocompatible coating is for exemplary purposes only, and does not restrict the present invention from utilizing a wide variety of biocompatible coatings on inner and outer surfaces of respective components of the present invention. For example, carbon coatings may be utilized on bio-compatible as well as non bio-compatible components of the present invention through vapor deposition or other known coating processes. 
   Other biocompatible materials may be utilized for various elements of the present invention, including certain mixed or co-extruded materials. A particular example of a co-extruded biocompatible material useful in respective components of the present invention is co-extruded resins of ePTFE and carbon. In addition, pyrolytic carbon may be utilized as a biocompatible material in such components. 
   As shown in  FIG. 9 , at least first end  38  of supply conduit  32  is preferably tapered such that the thickness of supply conduit  32  at first end  38  is less than about 50% of the thickness of central portion  31  of supply conduit  32 . Such a tapered end is an important aspect of the present invention, and is specifically configured for reducing flow stresses on the fluid, as well as minimizing imposition of turbulent flow characteristics to the fluid flow stream. By minimizing such effects, the blood flow passing through connector  13  is less likely to be damaged and/or to coagulate or clot, which could potentially pose a health threat to the patient. Accordingly, the tapered configuration of the present invention specifically enables smooth flow transitions from respective graft segments into, and through connector  13 , as well as eventually into the respective vascular members of the patient. In addition to tapering first end  38  of connector  13 , the present invention contemplates tapering second end  40  of supply conduit  32 , as well as open ends of delivery conduit  34  and flow restricting means  22 . Various combinations of tapered ends of respective components of the present invention may be utilized as desired. 
   An additional aspect of the present invention for assisting and minimizing potentially deleterious effects to blood flow passing through various components of network  10  is in the preferred surface finishing of, in particular, flow connector  13 . Specifically, the surface finish of at least inner surfaces of connector  13 , and preferably of flow restricting means  22 , is about 20–30 μinches, and more preferably between about 24 and about 28 μinches. The above-stated level of surface smoothness is advantageous in the present invention for minimizing hemolysis in the blood flow passing therethrough. 
   As is illustrated in  FIG. 2  and in  FIGS. 5–6 , grafted network  10  preferably includes a flow restrictor means  22  having a contoured inner diameter so as to obtain a throttling effect to fluid passing therethrough. The contoured inner dimension of flow restricting means  22  is shown in dashed lines in  FIG. 2 , and is best represented in the cross-sectional view of  FIG. 6 . Flow restricting means  22  is preferably a distinct unit having an outer surface  25  and an open channel  26  axially extending therethrough. Flow restricting means  22  further includes first and second ends  27 ,  28 , with flow being directed through restricting means  22  from first end  27  through second end  28 . Preferably, flow restricting means  22  includes a converging tapered portion  92  extending from a first end portion  29  to a central throttle portion  94 . As shown in  FIG. 6 , central throttle portion  94  extends between converging inlet tapered portion  92  to diverging outlet tapered portion  96 , which diverging outlet taper portion  96  extends to second end portion  30  of flow restricting means  22 . Although flow restricting means  22  is described as having “tapered” portions for providing desired flow characteristics, the present invention contemplates a variety of inlet portion and outlet portion configurations including parabolic or other formations, so long as inlet portion  92  includes a converging inner diameter, and outlet portion incorporates a diverging inner diameter for flow restricting means  22 . 
   The inner diameter configuration through flow restricting means  22  is preferably designed so as to create a substantial flow pressure decrease between inlet end  27  and outlet end  28 , as well as to create substantial back pressure into grafted network  10  upstream from flow restricting means  22 . Such objectives are accomplished by reducing the diameter through which fluid flow may pass as it exits grafted network  10 . However, it is preferred that the flow restricting means enable such pressure characteristics while maintaining a substantially laminar flow regime throughout flow restricting means  22 . Accordingly, the inner diameter profile of flow restricting means  22  is specifically configured so as to maximize pressure drop therethrough while maintaining substantially laminar flow regime. In particular, inlet taper portion  92  is tapered between about 30° to about 40° with respect to a central axis  99  of flow restricting means  22 , and more preferably between about 35°–40°. Outlet diverging taper portion  96  of the present invention is preferably angled between about 10° and about 20° with respect to axis  99 , and more preferably about 12°–15° with respect to axis  99 . Disposed between such inlet taper portion  92  and outlet taper portion  96  is throat portion  94 , which is a substantially constant-diameter section of open channel between about 1.5 to about 2.0 mm, and more preferably between about 1.6 and about 1.8 mm in diameter. In other embodiments of the present invention, however, throat portion  94  may be somewhat convergent or divergent in inner diameter, or both, such that none or only a portion of throat portion  94  is a constant diameter. 
   In preferred embodiments of the present invention, fluid flow passing through flow restricting means  22  loses between about 90 and 95% of the energy initially carried by the fluid upon exit from source location  12 . Accordingly, flow restrictor means  22  creates a substantial pressure drop from inlet  27  to outlet  28 , thereby effectively maintaining a constant fluid pressure in network  10  upstream from flow restricting means  22 , which pressure is substantially equal to the fluid flow pressure within the relatively high fluid pressure source. In other words, the relatively high fluid pressure to relatively low fluid pressure network provided by flow restrictor means  22  of the present invention enables network  10  to maintain relatively high fluid flow throughout the system. Accordingly, the one or more vascular members being supplied with bypass blood flow are insured of having adequate source flow from network  10  to satisfy the needs of the particular vascular member. 
   In some existing systems for bypass procedures, graft segments are utilized to directly couple an aortic blood source to a respective vascular member requiring bypass blood flow thereto. Due to the generally low pressure environment of the arteries receiving bypass blood flow, blood is not typically supplied under pressure throughout the graft segment. As such, bypass blood flow into the respective arteries can be less than adequate due to the low fluid pressure within the graft segment. By contrast, network  10  of the present invention is maintained under relatively high pressure due to the specifically configured flow restraining means  22 . Accordingly, bypass blood flow is immediately available to respective vascular members  14  through connectors  13  when needed. An additional advantage inherent in network  10  of the present invention is due to the relatively high fluid pressure maintained therewithin. In many current systems, stand-alone graft segments must be spirally reinforced to maintain a predetermined configuration, particularly during times of relatively low internal fluid pressure. Since the respective graft segments of network  10  of the present invention are consistently maintained at relatively high internal fluid pressure, no spiral reinforcement of respective graft segments is required herein. Accordingly, the thickness, and therefore workability and malleability, of the graft segment material may be significantly reduced. Moreover, such reduced thickness graft material further results in cost savings over conventional systems. 
   As described above, flow restricting means  22  may preferably include annular recessed portions  102  disposed on an outer surface thereof adjacent to first and second ends  27 ,  28 . Such annular recessed portions act as locating means for assisting a technician in securing flow restricting means within a respective graft segment by providing locations at which sutures or other securing means may be fixedly positioned. Flow restricting means  22  is preferably a distinct body that is operably positioned and secured within a respective graft segment, such as graft segment  18 , at a location adjacent to terminal delivery location  20 . The distinct body of flow restricting means  22  may be selectively positioned at desired locations within a respective graft segment, such that network  10  is modifiable for particular implantation procedures. 
   In other embodiments of the present invention, open ends of respective graft segments are coupled to first and second ends  27 ,  28  of flow restricting means  22 . Such graft segment ends may preferably be expanded outwardly with the use of a tool having a specific predetermined diameter or a rolling manual manipulation, such that the resulting internal diameter of respective open ends of the graft segments coupled to flow restrictor means  22  through a snug interference fit. Of course, such graft segments are permanently secured to first and second ends  27 ,  28  of flow restricting means  22  through sutures or other permanent attaching means, such as glue or the like. 
   In still further embodiments of the present invention, flow restricting means  22  may be integrally formed with a respective graft segment, in that the graft segment and flow restricting means  22  share common materials and outer surfaces. In such an embodiment, the respective graft segment is provided as being substantially longer than is necessary in typical implantation procedures, such that the surgeon may cut the length of the unit to properly fit within network  10  of the present invention. 
   Flow restricting means  22  is preferably fabricated from a biocompatible material such as ePTFE, but may instead be fabricated from other durable and biocompatible materials, including certain metals. In addition, flow restricting means  22  may include one or more biocompatible coatings disposed on at least inner surfaces thereof for enhancing its compatibility within the body of a patient. 
   Additional embodiments of multiple channel fluid flow connectors of the present invention are illustrated in  FIGS. 7–8 . As shown in  FIG. 7 , flow connector  112  includes a supply conduit  114  and a delivery conduit  116 , with supply conduit  114  and delivery conduit  116  being coupled via intermediate conduit  118 . Preferably, intermediate conduit  118  forms an open passageway between supply conduit  114  and delivery conduit  116  such that supply conduit  114  and delivery conduit  116  are fluidly coupled to one another via intermediate conduit  118 . Preferably, intermediate conduit  118  includes radiused transition points forming flared ends  120 ,  122  for transporting blood flow therethrough with minimal deleterious effects thereon. In particular, flared ends  120 ,  122  extend outwardly from an annular apex  121 ,  123  to respective annular outer ends  129 ,  130 , with such annular outer ends  129 ,  130  having a diameter exceeding the diameter of transfer conduit  118  by between about 0.25 and about 1.5 mm. Such a configuration minimizes turbulent flow effects, as well as transitional corners where damage to blood may occur. 
   A further alternative embodiment is illustrated in  FIG. 8 , wherein transfer conduit  148  is angled with respect to supply conduit  144  in an orientation such that an obtuse angle α of between about 100° and 120° is formed between transfer conduit  148  and first inlet open end  145  of supply conduit  144 . Correspondingly, an acute angle β of between about 60° and about 80° is formed between transfer conduit  148  and second outlet end  146  of supply conduit  144 . In the embodiment illustrated in  FIG. 8 , transfer conduit  148  is so angled such that in-flow of fluid is at least partially directed into delivery conduit  150  through transfer conduit  148  without having to undergo a substantially right-angle flow transition. Thus, fluid flow passing through transfer conduit  148  undergoes a reduced degree of stress imparted thereon to reach delivery conduit  150 . 
   An additional alternative embodiment of the present invention is illustrated in  FIG. 10 , and shows a flared outer end of transfer conduit  178 . Such a flared outer end  180  assists in minimizing turbulent flow effects as blood flow is routed from supply conduit  176  into the targeted vascular member via transfer conduit  178 . 
   An additional embodiment of the present invention is illustrated in  FIG. 11 , with connector  213  having a supply conduit  232  and a delivery conduit  234 , which delivery conduit  234  includes at least first open end portion  258  having an open end  256 . As shown in  FIG. 11 , first open end portion  258  is preferably formed at first open end  256  such that end  257  of delivery conduit  234  is substantially disposed along a plane in an angular relationship to a perpendicular cross-sectional plane of a delivery lumen  252 . Such an angular relationship is preferably between about 10 degrees and about 80 degrees with respect to the cross-sectional plane, and may be in an orientation like that shown in  FIG. 11  or  FIG. 12 . 
   Connector  213  may further include a second open end portion  264  having a tapered second open end  262  which preferably substantially mirrors first open end  256 . The respective tapered open ends  256 ,  262  provide for relatively easy insertion of delivery conduit  234  into a respective coronary artery, in that little or no arterial manipulation is required by the physician in order to insert delivery conduit  234  into place through an opening formed in the respective coronary artery. In particular, there is no operative need for additional instruments to dilate the target artery prior to delivery conduit  234  insertion therein. 
   As further illustrated in  FIGS. 11 and 12 , delivery conduit  234  may include annular recessed portions  272  disposed in an outer surface thereof and adjacent to respective open ends  256 ,  262 . Such recessed portions  272  are specifically configured to assist in obtaining a secure attachment between the target artery tissue and delivery conduit  234 . Moreover, annular recessed portions  272  provide a locating zone at which to optionally suture arterial tissue thereto, in that such sutures may circumferentially bind such arterial tissue to respective annular recessed portions  272 . 
   Referring back to  FIGS. 3 and 4 , first end portion  58  may be somewhat longer than second end portion  64  as measured from central intersection plane  65  to respective ends  54 ,  62 , and may be between about 1 and 4 mm longer than second end portion  64 . Such a configuration assists the surgeon in inserting delivery conduit  34  into the targeted vascular member  14  by reducing the incision size into vascular member  14 . In operation, the surgeon may insert relatively longer end portion  58  into vascular member  14 , and then simply “drop” second end portion  64  therein for complete insertion. In other embodiments of the present invention, second end portion  64  may be relatively longer than first end portion  58 , as measured from intersection plane  65 . 
   In some embodiments of the present invention, at least delivery conduit  34  is fabricated from a selectively expansive material, such that when delivery conduit  34  is implanted within a particular vascular member  14 , the diametrical dimension thereof may be selectively expanded so as to obtain a fluid-tight interference fit within the respective vascular member  14 . Such a selectively expansive material may be in a mesh configuration, and may be, for example, nitanol. Other components of the present invention may also or instead be fabricated from a selectively expansive material. 
   An additional embodiment of the present invention provides for a rotation means disposed between supply conduit  32  and delivery conduit  34 , wherein delivery conduit  34  may be selectively rotated with respect to supply conduit  32 , whereby specific alignment between network  10  and a particular vascular member  14  is less critical, due to the fact that delivery conduit  34  may be rotated into alignment with such vascular member  14  without disturbing grafted network  10 . 
     FIG. 13  illustrates an additional embodiment of the present invention, with connector  313  including a supply conduit  332  and a delivery conduit  334  integrally formed with one another. First open end portion  358  is illustrated as being somewhat longer than second end portion  364  of delivery conduit  334 , as measured from a central intersection plane. However, such first and second end portions  358 ,  364  may instead be of substantially equal length. 
   A particularly preferred aspect of the embodiment illustrated in  FIG. 13  is in the respective angled relationship between central axis  372  of first end portion  358 , with respect to second central axis  374  of second end portion  364  of delivery conduit  334 . Preferably, respective central axes  372 ,  374  are angled with respect to a normal tangential plane at intersectional point  365  by between about 0° and about 10°. In some embodiments, angle “x” is between about 0° and about 10°, and more preferably between about 1° and about 5°. Angle “y” may be between 0° and about 10°, and more preferably between about 1° and about 5°. 
   Preferably, one or both of first and second end portion  358 ,  364  of delivery conduit  334  are disposed at angles “x” and “y”, respectively, in relation to a normal tangential line of supply conduit  332 . Accordingly, either one or both of first and second end portions  358 ,  364  may be angled out of alignment with such a normal tangential plane. While the embodiment in  FIG. 13  is described with respect angles “x” and “y”, first and/or second end portions  358 ,  364  may instead be formed along a radius of curvature with respect to the tangential line described above. In any case, the configuration of connector  313  in accordance with  FIG. 13  preferably conforms with the curvature of the outer surface of internal body structures against which connector  313  is operably implanted. For example, delivery conduit  334  may be operably implanted into a coronary artery which is located immediately adjacent the outer surface of the patient&#39;s heart. The overall configuration of delivery conduit  334  is therefore customized in order to best conform to the outer surface topography of the patient&#39;s heart where connector  313  will be operably positioned. Such conformity with the outer surface of the heart assists in reducing strain on arterial walls that house delivery conduit  334 , which arterial walls also conform to the surface topography of the patient&#39;s heart. This reduction in tissue strain minimizes the likelihood of deleterious effects caused by the implantation of delivery conduit  334  within a respective artery or other vascular member. 
   Though the connector of the present invention has been illustrated with the supply conduit and the delivery conduit being orthogonally positioned with respect to one another, it is contemplated by the present invention that such a relationship is not critical to the effectiveness thereof. Specifically, it is contemplated by the present invention to position the delivery conduit in orthogonal or non-orthogonal orientations with respect to the supply conduit. Moreover, one or both of the supply conduit and/or the delivery conduit may be curvalinearally arranged with respect to one another. Such modifications in the overall configuration of the connector may be useful in certain applications where an orthogonal orientation is not most appropriate. 
   In preferred embodiments of the present invention, supply conduit  32  is between about 2 mm and about 8 mm in external diameter, and delivery conduit  34  is between about 0.5 mm and about 5 mm in external diameter. In a particularly preferred embodiment of the present invention, supply conduit  32  has an external diameter of about 6 mm, and delivery conduit  34  has an external diameter of about 3 mm. 
   In accordance with the present invention, one or more graft segments are provided for each bypass procedure. In addition, at least one multiple channel fluid flow connector is provided comprising biocompatible material and includes an integrated supply conduit and delivery conduit for channeling blood flow from a relatively high pressure source to a location in, for example, a coronary artery where blood flow correction is needed. The connector devices are typically dual-lumen which provides for direct channeling from the supply conduit to the delivery conduit, and consequently to the targeted vascular member. In the dual-lumen structure of the present invention, a relatively large diameter lumen is employed for that portion of the connector device which is in direct communication with the aortic or other high pressure source, and with the delivery lumen typically being of somewhat lesser overall diameter and being designed for insertion into a slit formed in the targeted vascular member requiring bypass. 
   In preferred embodiments of the present invention, at least one graft segment is pre-attached to an open end of connector  13 , and is of a length which is more than ample for the contemplated use. For example, first graft segment  11  is preferably pre-attached to first end  38  of supply conduit  32  prior to surgery, and preferably prior to shipment from the manufacturing facility. First graft segment  11  is consequently made substantially longer than necessary for connection between vascular member  14  and source location  12 , such that the surgeon may cut first graft segment  11  to size during the surgical process. Thus, the surgeon is able to cut the graft segment to a desired and required length in the course of the procedure, while at the same time not having to disturb the integrity of the previously-prepared secure junction between first graft segment  11  and connector  13 . 
   In the course of the overall procedure, terminal end  20 , including graft segment  24 , are secured in place at the vena cava or other low-pressure site, while continuing the process in the direction of the source, which is normally the aorta. Attachments are made in accordance with conventional protocol, with connector  13  being coupled through a slit formed in the pertinent vascular member to provide bypass flow thereto. 
   The invention has been described herein in considerable detail in order to comply with the patent statutes, and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use embodiments of the invention as required. However, it is to be understood that the invention can be carried out by specifically different devices and that various modifications can be accomplished without departing from the scope of the invention itself.