Ventricular assist device with valved blood conduit and method of making

Abstract

A ventricular assist device includes a pair of valved conduits and a pumping portion connected by these conduits into the circulatory system of a host patient. The pumping portion and valved conduits are constructed and configured to minimize the number of material-surface transitions which blood must cross in flowing through the device. Also, the valved conduits include porcine xenograft valves, which are externally supported by stenting structure located outside of the blood-contacting flow path of the device. A flexible shape-retaining inner wall member of the valved conduits is impervious to blood, but defines a porous inner surface on which a stable biological interface may form. Also, this inner wall member is shaped with sinuses which do not replicate either the porcine sinuses from which the xenograft valves were taken, or human aortic sinuses. However, the sinuses of the inner wall member are configured to provide effective valve action by the formation of vigorous vortices in the blood flow downstream of these valves, and to avoid the formation of clots on the blood-contacting surfaces of the valved conduits.

We claim:  
     
         1 . A ventricular assist device comprising: 
 a pumping portion including a unitary flexible wall member having a singular blood-contacting inner surface entirely defining a variable-volume chamber for receiving and discharging-blood, said unitary flexible wall member also defining one of an inflow port and an outflow port for respective flow of blood to and from said variable-volume chamber; and    a flexible conduit member having a side wall defining a second blood-contacting inner surface, said flexible conduit member communicating blood between the variable-volume chamber and the circulatory system of a host organism, said side wall of said flexible conduit member sealingly engaging said unitary flexible wall member at a respective one of said inflow and outflow ports;    whereby flowing blood of said host organism, in passing through said flexible conduit and said variable-volume chamber of said pumping portion, contacts only the first and the second blood-contacting inner surfaces.    
     
     
         2 . The ventricular assist device of    claim 1    further including a prosthetic valve disposed within said flexible conduit member for limiting blood flow therein to a single direction, and a stenting structure for said prosthetic valve disposed outside of said flexible conduit member.  
     
     
         3 . The ventricular assist device of    claim 2    further including sutures attaching said prosthetic valve to said stenting structure through said side wall of said flexible conduit member, whereby blood flowing through said flexible conduit member contacts only said second blood-contacting inner surface, said prosthetic valve, and said sutures.  
     
     
         4 . The ventricular assist device of    claim 2    wherein said prosthetic valve is a natural tissue xenograft valve.  
     
     
         5 . The ventricular assist device of    claim 4    wherein said natural tissue xenograft valve is a porcine xenograft.  
     
     
         6 . The ventricular assist device of    claim 2    wherein said prosthetic valve includes at least a pair of valve leaflets, said flexible conduit member further defining a like number of sinuses downstream of and axially aligning with said prosthetic valve leaflets.  
     
     
         7 . The ventricular assist device of    claim 6    wherein said sinuses of said flexible conduit are smaller than human natural aortic valve sinuses.  
     
     
         8 . The ventricular assist device of    claim 6    wherein said sinuses of said flexible conduit define a portion of said second blood-contacting surface, and downstream of said prosthetic valve said sinus-portion of said second surface rejoins at an acute glancing angle a substantially-cylindrical remainder portion of said second surface.  
     
     
         9 . The ventricular assist device of    claim 6    wherein said sinuses of said flexible conduit have an aspect ratio of at least 1.3.  
     
     
         10 . The ventricular assist device of    claim 9    wherein said sinuses of said flexible conduit have an aspect ratio in the range from about 1.3 to about 1.6 or more.  
     
     
         11 . The ventricular assist device of    claim 6    wherein said sinuses of said flexible conduit have an aspect ratio of substantially 1.45.  
     
     
         12 . The ventricular assist device of    claim 1    additionally including an elongate conduit member connecting with said flexible conduit member, said elongate conduit member at one end thereof fluidly communicating with said host organism's circulatory system and at an opposite end fluidly communicating with said flexible conduit member to communicate blood from said host's circulatory system to or from said variable-volume chamber, said inner wall of said flexible conduit member directly sealingly engaging said elongate conduit member at an end of the latter.  
     
     
         13 . The ventricular assist device of    claim 1    further including a tubular housing supportingly receiving said flexible conduit member, said housing defining at least one perforation therethrough outwardly exposing said flexible conduit member to body fluids of said host organism.  
     
     
         14 . The ventricular assist device of    claim 13    additionally including means for resiliently retaining said flexible conduit member in sealing engagement with said flexible wall member at said respective one of said inflow or outflow ports.  
     
     
         15 . The ventricular assist device of    claim 14    wherein said means for resiliently retaining sealing engagement of said flexible conduit member with said flexible wall member includes said pumping portion having a respective housing defining a recess into which said flexible conduit and tubular housing thereof is received to sealingly engage said flexible wall member, said tubular housing carrying means for engaging and securing axially with said pump portion housing and urging said flexible conduit into sealing engagement with said flexible wall member, and resilient means interposing axially between said means for engaging and said tubular housing for allowing a limited amount of axial relative movement therebetween.  
     
     
         16 . The ventricular assist device of    claim 15    wherein said means for resiliently retaining sealing engagement of said flexible conduit member with said flexible wall includes said tubular housing rotationally carrying a collar which threadably engages into said recess of said pump portion housing to urge a flange portion of said tubular housing into engagement with said pump portion housing, and a circumferentially extending axially-resilient washer member interposed axially between said collar and said flange of said tubular housing.  
     
     
         17 . The ventricular assist device of    claim 16    wherein said axially-resilient washer member includes a metallic wave washer.  
     
     
         18 . The ventricular assist device of    claim 12    further including said elongate conduit member including on an inner blood-contacting surface thereof a bio-degradable organic coating for rendering said elongate conduit initially more leak resistant post-implantation with respect to blood loss from said organism's circulatory system.  
     
     
         19 . The ventricular assist device of    claim 18    wherein said tubular housing further includes means for sealingly connecting with said elongate conduit member while sealingly accommodating change of dimension thereof as said biodegradable coating is absorbed by said host organism.  
     
     
         20 . The ventricular assist device of    claim 19    wherein said means for sealingly connecting includes said tubular housing defining a tapered seating feature to which an end of said elongate conduit sealingly connects, a shoulder on said elongate conduit, and a threaded ring engaging both said shoulder and said tubular housing to threadingly urge said elongate conduit into sealing engagement with said seating feature, and an axially-resilient washer member interposing axially between said shoulder and said ring to take up axial dimension lost by said elongate conduit in response to absorption of said bio-degradable coating.  
     
     
         21 . The ventricular assist device of    claim 20    wherein said axially-resilient washer member includes a metallic wave washer.  
     
     
         22 . A shape-retaining flexible conduit for carrying blood in a living organism, said conduit comprising:  
       fabric sheet material defining a tubular body having an inner surface bounding a flow path for said blood and an outer surface, at said outer surface said tubular body carrying an impermeable coating of biologically-compatible polymeric material penetrating into said fabric toward but short of said inner surface, said impermeable polymeric coating being continuous axially and circumferentially to render said tubular body impervious to blood, and said inner fabric surface remaining porous to provide for attachment of a stable biological interface thereon.  
     
     
         23 . The flexible conduit of    claim 22    further including valve means disposed in said conduit flow path for limiting blood flow therein to a single direction.  
     
     
         24 . The flexible conduit of    claim 23    wherein said valve means includes a prosthetic valve.  
     
     
         25 . The flexible conduit of    claim 24    wherein said prosthetic valve is a porcine xenograft.  
     
     
         26 . The flexible conduit of    claim 23    further including a stenting structure for supporting said valve means, said stenting structure being disposed outside of said polymeric coating and being isolated thereby from contact with said blood.  
     
     
         27 . The flexible conduit of    claim 24    wherein said prosthetic valve includes at least a pair of valve leaflets, said flexible conduit member further defining a like number of sinuses downstream of and axially aligning with said prosthetic valve leaflets.  
     
     
         28 . The flexible conduit of    claim 27    wherein said sinuses of said flexible conduit are smaller than human natural aortic valve sinuses.  
     
     
         29 . The flexible conduit of    claim 28    wherein said sinuses of said flexible conduit define a portion of said inner surface, and downstream of said prosthetic valve said sinus-portion of said inner surface rejoining at an acute glancing angle a substantially-cylindrical remainder portion of said inner surface.  
     
     
         30 . The flexible conduit of    claim 28    wherein said sinuses have an aspect ratio of at least 1.3.  
     
     
         31 . The flexible conduit of    claim 30    wherein said sinuses have an aspect ratio in the range from about 1.3 to about 1.6 or more.  
     
     
         32 . The flexible conduit of    claim 31    wherein said sinuses have an aspect ratio of substantially 1.45.  
     
     
         33 . A valved prosthetic conduit for carrying a unidirectional blood flow in a living organism, said valved conduit comprising: 
 a natural-tissue xenograft valve defining a first blood-contacting surface;    a fabric conduit in which said valve is secured and defining a second blood-contacting surface; and    sutures securing said xenograft-tissue valve into said fabric conduit and defining a third blood-contacting surface;    whereby the valved conduit has only the first, the second, and the third blood-contacting surfaces contacted by blood flowing through said conduit.    
     
     
         34 . The valved conduit of    claim 33    further including a stenting structure for said xenograft valve, said stenting structure being disposed outside of said fabric conduit.  
     
     
         35 . The valved conduit of    claim 34    wherein said fabric conduit is impervious to blood, and said fabric conduit isolates said stenting structure from blood contact.  
     
     
         36 . The valved conduit of    claim 33    wherein said fabric conduit is flexible and shape-retaining, said fabric conduit defining plural sinuses downstream of said xenograft valve, and said plural sinuses being the same in number and aligning axially with the natural valve leaflets of said xenograft valve.  
     
     
         37 . The valved conduit of    claim 36    wherein said plural sinuses differ from both the natural sinuses from which said xenograft valve was removed, and from natural human sinuses.  
     
     
         38 . The valved conduit of    claim 37    wherein said sinuses of said flexible conduit are smaller than human natural aortic valve sinuses.  
     
     
         39 . The valved conduit of    claim 38    wherein said sinuses have an aspect ratio of at least 1.3.  
     
     
         40 . The valved conduit of    claim 39    wherein said sinuses have an aspect ratio in the range from about 1.3 to about 1.6 or more.  
     
     
         41 . The valved conduit of    claim 40    wherein said sinuses have an aspect ratio of substantially 1.45.  
     
     
         42 . A method of making a flexible shape-retaining blood-impermeable fabric conduit member with a porous inner surface for use in carrying blood within a living organism and providing for formation of a stable biological interface on said porous inner surface, said method comprising the steps of: 
 forming a tubular porous fabric body having an inner surface and an outer surface;    on said outer surface applying a continuous coating of biologically-compatible blood-impervious polymeric material into said fabric toward but short of said inner surface while maintaining porosity of said inner surface;    employing said coating of polymeric material to render said tubular fabric body impermeable to blood flow; and    forming said fabric conduit member from said fabric body coated with said polymeric material.    
     
     
         43 . The method of    claim 42    including the steps of using a thermoset material as said blood-impervious polymeric material, and curing said thermoset material sufficiently to prevent further mobility of said polymeric material in said fabric before forming said conduit member therefrom.  
     
     
         44 . The method of    claim 43    further including the steps of using a rotational cylindrical mandrel to support said tubular porous fabric body, pressing a movable support surface against said tubular porous fabric body on said mandrel, and feeding a sheet of raw polymeric material between said fabric and said movable support surface as the latter and said mandrel are moved in unison.  
     
     
         45 . The method of    claim 43    additionally including the steps of: 
 further forming said fabric body coated with said polymeric material into a selected shape subsequent to curing of said thermoset material by;  
 providing a mold having a cavity of said selected shape;  
 placing said fabric body into said cavity;  
 inserting a balloon into said fabric body;  
 forcefully inflating said balloon while heating said cavity to require said fabric body to take the shape of said cavity; and  
 cooling said shaped fabric body to cause the latter to retain said selected shape.  
 
     
     
         46 . A method of providing for assistance to a selected heart chamber of a living organism having a blood circulatory system, said method comprising the steps of: 
 providing an artificial flow path for a flow of blood leading from said circulatory system and returning to said circulatory system downstream of said selected heart chamber;    providing a variable-volume chamber in said artificial flow path;    providing a pair of like-disposed one-way valves bracketing said variable-volume chamber in said artificial flow path;    providing means securing said pair of one-way valves in respective ones of a pair of portions of said artificial flow path;    expanding and contracting said variable-volume chamber to withdraw blood from said circulatory system, and to return said blood to said circulatory system downstream of said selected heart chamber to assist or replace the function of the heart chamber in circulating said blood in said circulatory system;    using a singular flexible wall member to define said variable-volume chamber;    using a pair of respective artificial conduit members to define said pair of portions of said artificial flow path and to receive said one-way valves; and    sealingly contacting said pair of respective artificial conduit members directly with said singular flexible wall member;    whereby blood from said circulatory system in flowing past said pair of one-way valves and through said variable-volume chamber contacts only said singular flexible wall member, said pair of artificial conduit members, said pair of one-way valves, and said means securing said pair of one-way valves into said pair of artificial conduit members.    
     
     
         47 . A conduit for carrying blood comprising: 
 a tubular body having an inner surface bounding a flow path for said blood;    prosthetic valve means sealingly disposed in said flow path for limiting blood flow therein to a single direction, and including at least one valve leaflet;    said flexible conduit member further defining the same number of sinuses as the number of valve leaflets of said prosthetic valve, each said sinus being downstream of and axially aligning respectively with a respective one leaflet of said prosthetic valve;    wherein each said sinus of said flexible conduit is shallower and longer than a human natural aortic valve sinus.    
     
     
         48 . The conduit of    claim 47    wherein said sinus has an aspect ratio of at least 1.3.  
     
     
         49 . The conduit of    claim 48    wherein said sinus has an aspect ratio in the range from about 1.3 to about 1.6 or more.  
     
     
         50 . The conduit of    claim 49    wherein said sinus has an aspect ratio of substantially 1.45.  
     
     
         51 . The conduit of    claim 47    wherein said prosthetic valve is a porcine xenograft.  
     
     
         52 . The conduit of    claim 47    further including a stenting structure for supporting said prosthetic valve means, said stenting structure being disposed outside of said tubular body and being isolated thereby from contact with blood flowing in said conduit.  
     
     
         53 . The conduit of    claim 47    wherein each said sinus at a downstream termination thereof rejoins a cylindrical projection of said tubular body at an acute glancing angle.  
     
     
         54 . A valved prosthetic conduit for carrying a unidirectional blood flow in a living organism, said valved conduit comprising: 
 a prosthetic valve;    a prosthetic conduit in which said valve is secured;    a stenting structure for said prosthetic valve, said stenting structure being disposed outside of said conduit;    whereby the stenting structure is isolated from contact with flowing blood by said conduit.    
     
     
         55 . The valved conduit of    claim 54    wherein said conduit is impervious to blood and defines a porous inner surface providing for a stable biological interface within said conduit.  
     
     
         56 . The valved conduit of    claim 54    wherein said conduit is formed of flexible and shape-retaining fabric defining plural sinuses downstream of said prosthetic valve, said prosthetic valve including plural valve leaflets and said plural sinuses being the same in number and aligning axially with the valve leaflets of said prosthetic valve.  
     
     
         57 . A blood-carrying conduit apparatus,comprising: 
 a first flexible conduit member defining a flow path for communicating a flow of blood therethrough, and having a flexible side wall defining a blood-contacting inner surface bounding said flow path;    a second blood-carrying member defining a flow path for communicating blood therein;    said side wall including a reentrant portion defining an end surface for said first flexible conduit member;    and means urging said end surface of said conduit member sealingly into engagement with said second blood-carrying member.    
     
     
         58 . The conduit apparatus of    claim 57    wherein said means for urging further including means for resiliently accommodating relative axial movement of said conduit member relative to said second member while maintaining sealing contact therebetween.  
     
     
         59 . The conduit apparatus of    claim 58    wherein said means urging said end surface of said conduit into sealing engagement with said second member includes a collar member circumscribing said conduit member and engaging said second member and a radially extending portion of said conduit member to urge the latter into sealing engagement at said end surface with said second member.  
     
     
         60 . The conduit apparatus of    claim 59    wherein said means for resiliently accommodating relative axial movement of said conduit member relative to said second member includes an axially-resilient element interposing between said collar member and said radially extending portion of said conduit member.  
     
     
         61 . The conduit apparatus of    claim 60    wherein said axially-resilient element includes a circumferentially extending wave washer interposing between said collar and said radially extending portion of said conduit.