Abstract:
An inflow conduit assembly for conducting blood from a ventricle to a Ventricular Assistance Device (VAD) is provided. The assembly includes a rigid tube including an angled heart engaging end for insertion into a ventricle. The angled heart engaging end defines a long side for placement adjacent a heart septum. The tube includes an orifice end for attachment to the VAD, and the inflow conduit assembly further includes a coupling for attaching the orifice end of the tube to the VAD. The coupling is movable between a rotatable position wherein the tube is rotatable relative to the VAD, and a locked position wherein the tube is immobile relative to the VAD.

Description:
FIELD OF INVENTION 
     The present invention relates to mechanical circulatory devices, and in particular to a conduit for a ventricular assist device. 
     BACKGROUND OF THE INVENTION 
     Mechanical Circulatory Devices (MCDs) such as artificial hearts, Ventricular Assist Devices (VADs) and other blood circulating systems have become increasingly recognized as life saving devices for patients whose heart is diseased or has been injured by trauma or heart attack or other causes. VADs in particular, are recognized as a major life saving modality for assisting patients who suffer from congestive heart failure. 
     VADs must be connected to the natural heart of patients. In order to connect a VAD to a natural heart of a patient, a conduit assembly is used. The conduit assembly has a tubular tip body. The tip body is inserted into the heart. For proper functioning, the tip body should penetrates the heart wall so that the tip of the tip body comes out of the heart wall. If the tip body does not penetrate long enough, the heart muscle tissue surrounding the open end of the tip body grows and closes over the opening of the tip body. Thus, the blood flow is blocked. 
     By penetrating the heart wall, the closing of the opening of the tip body by the heart muscle may be avoided. However, the penetrated tip body may interfere with the septum wall separating two blood chambers of the natural heart. The septum wall may interfere the blood flow coming into the opening of the tip body, and in a worst case, it could totally close the opening of the tip body. 
     Therefore, there is a need of a tip body for a conduit assembly which can prevent such interference of the septum wall of the heart. 
     SUMMARY OF THE INVENTION 
     According to the invention, an inflow conduit assembly for conducting blood from a ventricle to a VAD having an orifice surrounded by an orifice Rim includes a rigid tube. The rigid tube includes an angled heart engaging end for insertion into a ventricle. The angled heart engaging end defines a long side for placement adjacent a heart septum. The angled heart engaging end has an outer surface defining at least one hole for draining blood from the ventricle. 
     According to one aspect of the invention, the tube includes an orifice end for attachment to the VAD, and the inflow conduit assembly further includes a coupling for attaching the orifice end of the tube to the VAD. The coupling is movable between a rotatable position wherein the tube is rotatable relative to the VAD, and a locked position wherein the tube is immobile relative to the VAD. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be further understood from the following detailed description, with reference to the drawings in which: 
     FIG. 1 is a schematical side view of a VAD in use to which an embodiment of the present invention is applied; 
     FIG. 2A illustrates a lateral, exploded view of an inflow conduit assembly in accordance with an embodiment of the invention; 
     FIG. 2B illustrates a lateral, exploded view of an outflow conduit assembly in accordance with an embodiment of the invention; 
     FIG. 3 is a lateral cross-section of the tip body of the inflow conduit assembly in FIG. 2A; 
     FIG. 4A is a lateral view of the valve assembly in accordance with an embodiment of the present invention; 
     FIG. 4B is a lateral view of a modified tissue valve; 
     FIG. 4C is a perspective view of the valve enclosure in accordance with the embodiment in FIG. 4A; 
     FIG. 4D is a bottom cross-sectional view of the outflow suture assembly in accordance with the embodiment in FIG. 4A; 
     FIG. 4E is a cross-sectional view of the outflow suture assembly in FIG. 4D; 
     FIG. 4F is a lateral cross-sectional view of the inflow suture assembly in accordance with the embodiment in FIG. 4A; 
     FIG. 5A is a perspective view of the inflow end of the valve assembly, depicting the suturing technique, in accordance with an embodiment of the invention; 
     FIG. 5B is a perspective view of the outflow end of the valve assembly, depicting the suturing technique, in accordance with an embodiment of the invention; 
     FIG. 6 is a partial cross-sectional view of the inflow elbow conduit; and 
     FIG. 7 is a partial cross-sectional view of another inflow elbow conduit. 
     Similar references are used in different figures to denote similar components. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Mechanical Circulatory Devices (MCDs) include artificial hearts and Ventricular Assist Devices (VADs). An artificial heart is used in place of a natural heart. A VAD is used where a patient&#39;s natural heart that is diseased or injured is still partially functioning. A VAD is connected to such a natural heart and assists its functioning. Hereinafter the present invention is mainly described referring to VADs. However, the invention may be also applied to artificial hearts, other than those aspects respecting to connection with a natural heart. 
     FIG. 1 shows a VAD  2  in use to which an embodiment of the present invention is suitably applied. The VAD  2  has a blood chamber  5  having an inflow orifice  6  and an outflow orifice  7 . At the inflow orifice  6 , an inflow conduit assembly  100  is provided to connect the blood chamber  5  to a natural heart  1  of a patient. At the outflow orifice  7 , an outflow conduit assembly  200  is provided to connect the blood chamber  5  to the thoracic aorta  3 . The outflow conduit assembly  200  may be connected to a different part of the blood circulation system. 
     In operation, blood is pumped from the heart  1  into the blood chamber  5  of VAD  2  through the inflow conduit assembly  100 . The VAD  2  then pumps the blood out of the blood chamber  5  into the thoracic aorta  3  through the outflow conduit assembly  200 . 
     The inflow conduit assembly  100  comprises one or more conduits or tubes. A proximal tube  175  that is connected to the inflow orifice  6  is made to be rigid to provide strength and durability of the conduit assembly  100 . The proximal tube  175  is preferably curved to minimize interference with adjacent organs. In order to connect such a curved rigid tube  175 , the conduit assembly  100  uses a coupling  180  which is movable between a rotatable position and a locked position. In the rotatable position, the proximal tube  175  can be rotated about its axis relative to the VAD  2  so that it can be positioned at a desired angle to avoid interference with adjacent organs. The axis of the proximal tube  175  curves as the tube  175  covers. The tube  175  rotates about the axis at the section engaging with the VAD  2 . The VAD  2  may have one or more extension tubes. In that case, the tube  175  rotates about the axis at the section engaging with the nearest extension tube. After the angle of the proximal tube  175  is decided, the coupling  180  is moved to the locked position so that the proximal tube  175  is immovably locked relative to the VAD  2 . Similar couplings arc used for connection of other components as described later. 
     FIG. 2A shows a lateral exploded view of the inflow conduit assembly  100  in accordance with an embodiment of the invention. In this embodiment, the inflow conduit assembly  100  is connected to the VAD  2  by a coupling comprising a gland nut  180  and a corresponding threaded connector  191 . 
     The inflow conduit assembly  100  comprises two basic components, an apical tip assembly  110  and an inflow elbow assembly  170 . The apical tip assembly  110  and the inflow elbow assembly  170  are adapted to be connected together. 
     The inflow conduit elbow assembly  170  comprises an inflow elbow tube or conduit  175  with a female threaded coupling or gland nut  160  at one end and a further female threaded gland nut  180  at the other end. 
     The inflow elbow conduit  175  is rigid and generally curved along its length. Its shape is dictated by the desire of minimizing interference with adjacent organs. The inflow elbow conduit  175  presented in FIG. 2A has only one bend, however other shapes such as an S-shaped inflow elbow conduit may also be used. 
     On the VAD  2 , an inflow plug  190  is mounted at the inflow orifice  6 . The inflow plug  190  comprises an inflow port extension  6   a  having a rim  193  and a male threaded connector  191  for coupling to the gland nut  180 . The inflow plug  190  also has a flange  192  on its base surface near the inflow orifice  6 . The flange  192  has a cross-shaped outer surface. It serves in gripping onto the inflow plug  190  when the gland nut  180  is being tightened. 
     The gland nut  180  provides a rotatable union effect during the fitting procedure. That is, the gland nut  180  moves between a rotatable position and a locked position. At the rotatable position, the gland nut  180  allows the inflow elbow conduit  175  to rotate about its axis into any rotated position relative to the VAD  2 , when the VAD  2  is implanted. This allows flexibility in positioning of the conduit assembly  100 . The positioning flexibility is advantageous, considering the difference in anatomies from patient to patient. The positioning flexibility is also useful during experiments performed on calves, for example, which present even a more dramatic difference in anatomy by comparison to the human anatomy. During the fitting of the VAD  2 , an optimal position for the inflow elbow conduit  175  is determined. Then, the inflow elbow conduit  175  is locked in this position by tightening the gland nut  180  to the locked position. The optimal position of the inflow elbow conduit  175  defines a predetermined way into which the inflow conduit is to be fitted within its anatomical environment. 
     In order to achieve tight sealing, it is preferable that an end  183  of the inflow elbow conduit  175  closely mates the rim  193  of the inflow port extension  6   a.  One or more sealing rings may be used between the rim  193  of the inflow port extension  6   a  and the end  183  of the inflow elbow conduit  175  for tight sealing. 
     In order to facilitate the rotation of the inflow elbow conduit  175 , it is preferable that the mating surfaces of rim  193  of the inflow port extension  6   a  and the end  183  of the inflow elbow conduit  175  are smooth. It is also preferable that the rim  193  of the inflow port extension  6   a  and the end  183  of the inflow elbow conduit  175  are flat in a plane perpendicular to the axis of the inflow elbow conduit  175 . It is also preferable that they have coincidental circular shapes so that the inflow elbow conduit  175  may be rotated at any desired angle. However, they may have unsmooth surfaces, such as a saw like shape, or non-circular shapes, such as octagonal shapes, as long as those surfaces can achieve desired sealing effects at different rotational angles, with or without the aid of other sealing member. 
     The gland nut  180  may include bulges  182  on its external envelope surface. One of the purposes of the bulges  182  is to aid in gripping, by hand or by a wrench, onto the nuts  180 , during the fitting procedure. An alternative embodiment contemplates small cavities or holes instead of the bulges, to be gripped by a special instrument. Such an embodiment may be preferred because of the edges on the bulges  182 . 
     The gland nut  180  is preferably manufactured to very high tolerances to ensure an extremely smooth seam between the component pieces. A biolization coating is added, to make the seam as non-thrombogenic as possible. 
     As shown in FIG. 6, it is common that the VAD  2  uses an elastic bag  8  to form the blood chamber  5 . It is preferable to extend the open end  9  of the elastic bag  8  over the rim  193  of the inflow port extension  6   a  to prevent leakage of blood from the open end  9 . The bended open end  9  is held by the engaging surface  183  of the inflow elbow conduit  175 . In order to provide a constant blood flow, the inner diameter of the elbow conduit  175  is adjusted to be smaller than that of the inflow plug  190  for twice of the thickness of the elastic bag  8 . By adjusting the inner diameter of the elbow conduit  175 , the inner wall of the elbow conduit  175  may be aligned with the inner surface of the elastic bag  8 . However, in this arrangement, due to the thickness of the elastic bag  8 , the elastic bag  8  creates a ring space  185  having a semi triangle cross sectional shape is created at the bended comer of the elastic bag  8 . This space  185  tends to cause turbulence in the blood flow. In order to prevent such turbulence, it is preferable to provide a washer  186  to mask the space  185 . 
     Referring back to FIG. 2A, the apical tip assembly  110  comprises a tubular tip body  112 , a skirt  118  and an end section  120 . The tubular tip body  112  is designed for insertion into the heart of the patient. The end section  120  is designed to stay outside the heart. The tip assembly  110  is sutured to the heart by the skirt  118 . 
     FIG. 3 is a lateral cross-sectional view of the tip body  112 . The tip body  112  has a tip section  115 . The tip section  115  is preferably rigid for insertion into the natural heart  1  through the heart muscle as shown in FIG.  1 . The length H of the tip body  112  is selected to be long enough to protrude the cardiac tissue of the heart wall, but not interfere with the heart muscle pumping action. 
     For proper functioning, the length H of the tip section  115  is preferably larger than the thickness of the heart wall through which it penetrates. If the tip body  112  is too short and it does not protrude the heart wall, the heart muscle tissue surrounding the open end of the tip body  112  grows and closes over the opening of the tip body  112 , thereby blocking the flow of blood from the heart. Based on human and animal experiments and observations, this length H is preferably between 1.5 and 3.5 cm. The inside diameter of the tip body  112  must allow sufficient blood flow to pass with acceptable velocities. If it is too slow, the blood flow can cause low washout. If it is too fast, the blood flow is disturbed causing turbulence. In order to let sufficient flow discharge for various body sizes and activities, a diameter D 1  of 13 to 30 mm is recommended. The smaller end of the range may be suitable for small body sizes, and the larger one for larger body sizes. 
     The protruding tip section  115  has the above advantages. However, it tends to cause blood pooling around the protruding tip section  115 . That is, around the tip section  115  near the hart wall, the blood flow becomes stagnant. In order to reduce such blood pooling, it is preferable to provide the tip section  115  with drainage holes  114  on its wall. The size of the holes  114  is such that the blood flows therethrough without clotting. It is preferably approximately 3 mm. The holes are preferably spaced approximately at a regular distance around the circumference of the tip section  115 . They may be provided approximately at every centimeter around the circumference of the tip section  115 . The provision of the holes  114  prevents or reduces the risk of stasis and thrombosis. 
     It is preferable that the open end  113  of the tip section  115  is angled relative to the axis of the tubular tip body  112 . Thus, the tip section  115  has a longest side  115   a  having a length h a  and a shortest side  115   b  having a length h b , as shown in FIG.  3 . If the open end  113  of the tip section  115  is flat in a plane perpendicular to the axis of the tip section  115 , the septum wall separating two blood chambers of the natural heart may interfere the flow of blood, and it could totally close the opening of the tip section  115 . By angling the open end  113 , such interference by the septum wall can be avoided. 
     When implanting the VAD assembly, the tip section  115  is fitted to rest with the longest side  115   a  against the septum wall of the heart. Thus, the longest side  115   a  is defined as the septum wall of the VAD assembly. The shortest side  115   b  of the tip section  115  is defined as the free wall. 
     In order to properly align the tip section  115 , the tip assembly  110  further includes a male threaded connection  120  which forms a union coupled with the female threaded gland nut  160  of the inflow elbow assembly  170  as shown in FIG.  2 A. The gland nut  160  is similar to the gland nut  180  described above. By the gland nut  160  and the male threaded connection  120 , the tubular tip body  112  and the inflow elbow conduit  175  are rigidly fixed to one another in any relative angular position. The gland nut  160  may include bulges  162  on its external envelope surface, similar to the bulges  182  on the gland nut  180 . 
     It is preferable that the tip body  112  accommodates a valve inset or assembly  140  to regulate the blood flow as described below. In order to accommodate the valve assembly  140  without generating disturbance in the blood flow, it is preferable that the tubular apical tip body  112  is cylindrical and presents a variable internal cross-section such that an essentially constant blood flow diameter is achieved when all parts of the conduit assembly arc fitted together. The tip body  112  may comprise two sections of internal diameters D 1  and D 2 , respectively, as shown in FIG.  3 . An internal ridge  116  may be provided to achieve the change in the internal cross-section. Referring also to FIG. 2A, the valve assembly  140  has an external diameter smaller than D 2  but larger than D 1 . Thus, it slides into the enlarged elongated cylindrical opening within the apical tip body  112  up to the ridge  116 . Preferably, the internal diameter of the valve assembly  140  is approximately equal to D 1 , for achieving an essentially constant blood flow diameter. This is important for the prevention of clot formation in the conduit. From literature and experimental studies, it is seen that an absolute blood flow diameter close to 23 mm is well suited to optimize the prevention of effects leading to clotting. 
     The end section  120  of the tip body  112  may be provided with a hexagonal outer cross section  122 . The hexed region  122  is intended to provide stability while fitting the VAD  2  inside the patient. Stability may be provided through a wrench action for example, so that the torque applied to the natural heart  1  during fitting is minimized. 
     The apical tip assembly  10  is attached to the natural heart  1  by means of the skirt  1118 . The skirt  118  is mounted on the tip body  112  between the tip section  115  and the end section  120 . The material from which the skirt  118  is manufactured is a flexible material, with tissue compatible characteristics. Many materials presenting such properties are known in the art. A commonly used material is a woven polyester velour. The shape of the skirt  118  may be circular or any other shapes. In a preferred embodiment, the skirt  118  is made of a flexible but strong material, it has approximately 1 to 12 cm in width. It is glued to the tip body  112  and sutured in place to the inside of the heart muscle. The procedure of suturing the skirt  118  is similar to that known in the art as ventricular apical cannulation. The skirt  118  is sufficiently flexible to conform to the curvature of the natural heart  1  and can be pierced with relative ease by a surgical needle. Once sutured in place, the heart tissue will grow and surround the skirt  118 , thus making an extremely strong bond. 
     In the embodiment of FIG. 2A, the inflow conduit assembly  100  presents a completely rigid structure to blood flowing through it. The use of a rigid structure prevents the conduit from collapsing, breaking or twisting under the various compression, tensile, torque forces and negative pressures exerted upon it. While the embodiment of FIG. 2A has a completely rigid structure, it may also include an elastic tubular member when less pressures are exerted, e.g., between the tip assembly  110  and the elbow assembly  170 . A diseased heart is generally swelled. Such a diseased heat tends to shrink as the disease is being cured. The elastic tubular member absorbs such changes in the size of the heart, and maintains the proper connection between the heart and the VAD  2 . 
     As to the material of rigid components, it is preferable to use titanium for several reasons. There is evidence to support the idea that the use of titanium provides the conduit systems  100  and  200  with non-thrombogenic properties. Specifically, titanium, when exposed to oxygen, becomes titanium oxide, which is also believed to be non-thrombogenic. In order to improve the blood compatibility of titanium oxide, the interior surface of the conduit systems  100  and  200  may be coated with a gelatin coating. This technique is known as biolization. 
     Titanium is one of the strongest metals for its weight. It has proven to be durable, extremely strong and resistive to stress. Therefore, the use of titanium allows for the manufacturing of very thin conduits, of reduced size and small weight. The use of titanium for over 60 years in humans for such things as hip joints, finger joints, orthopaedics and prosthesis shows evidence of tissue compatibility and non-thrombogenic properties. 
     Referring now to FIG. 2B, the outflow conduit assembly  200  comprises two basic components, an outflow conduit  210  and an outflow elbow assembly  270 , adapted to be connected together. Blood flows through the assembly  200  as shown by arrow B. 
     In the embodiment presented in FIG. 2B, the outflow conduit  210  comprises a tubular conduit section  215 , having an outflow end  217  and an inflow end  218 . The outflow end  217  is adapted to be sutured onto an artery or similar vessel. The inflow end  218  comprises a female threaded coupling or gland nut  260 . The gland nut  260  is similar to the gland nut  180  of the inflow conduit elbow assembly  100  in FIG.  2 A. The conduit section  215  is made of a flexible, tissue compatible material, such as a woven polyester velour. It is manufactured sufficiently long so that it can be cut at a desired length during the fitting procedure, either in a patient, or in an animal during experimental studies. Referring to FIG. 1, the outflow end  217  of the conduit section  215  is shown sutured to the thoracic aorta  3 . 
     The outflow conduit elbow assembly  270  is rigid and similar to the inflow elbow assembly  170  in FIG.  2 A. In the embodiment presented in FIG. 2B, the outflow conduit elbow assembly  270  includes a gland nut  280  at its inflow end, and a male threaded connector  273  at the other end. The gland nut  280  is similar in function to the gland nut  180  in the inflow conduit elbow assembly  170  in FIG.  2 A. The gland nut  280  is adapted to be coupled to a plug provided on the VAD  2  at the outflow orifice  7 , similar to plug  190 . Thus, the outflow elbow assembly  270  may be rotated around the axis of the elbow conduit, and then fixed at a desired angle relative to the VAD  2 . The male threaded connector  273  may include a hexagonal region  274  for gripping while tightening the gland nut  260 . In addition, the elbow assembly  270  may further include an enlarged elongated cylindrical opening within it, to receive a valve assembly  240 . 
     Preferably, the length and orientation of the components of the conduit systems  100  and  200  are chosen so as to minimize compression on adjacent organs and great vessels, once the MCD is implanted within an anatomical environment. Optimal sizes, geometries and orientations of the various parts of the conduit systems  100  and  200  may be determined based on study of both the literature and the anatomy of the human chest, as well as taking actual measurements during both intra-operative procedures and from fresh cadavers. 
     The outflow elbow assembly  270  may also include an enlarged elongated cylindrical opening similar to that in the apical tip assembly  110  shown in FIG. 2A for receiving a valve assembly  240 . 
     Referring back to FIG. 2A, the valve assembly  140  having a one-way valve is provided in the tip assembly  110  of the inflow conduit assembly  100 . The one-way valve assembly  140  prevents back flow of the blood from the blood chamber  5  to the heart. Traditionally, such a one-way valve was provided at the inflow orifice  6 . However, it often generated undesired flow patterns in the blood flow. Compared to the inflow port location, within the conduit assembly  100 , the blood flow is more stable. Thus, by providing the valve in the conduit assembly  100 , the disturbance in the blood flow by the provision of the valve is reduced. 
     Similarly, the outflow conduit assembly  200  is provided with the valve assembly  240  having a one-way valve in the elbow conduit assembly  270 , as shown in FIG.  2 B. The valve assemblies  140  and  240  may be identical to each other. By using identical valve assemblies for the inflow and outflow conduit assemblies  100  and  200 , these assemblies may be inserted in either conduit. This leads to an easier, more effective, fitting procedure. The valve assemblies will be described hereinafter referring only to valve assembly  140 , for simplicity. 
     Referring to FIGS. 4A,  5 A and  5 B, the valve assembly  140  comprises a valve enclosure assembly  141  and a one-way modified tissue valve  300 . The valve enclosure assembly  141  comprises a valve enclosure  145 , an outflow suture assembly  142  and an inflow suture assembly  150 . The tissue valve  300  is sutured to the inflow suture assembly  150 . 
     The modified tissue valve  300  is preferably a tricuspid or tri-foliate, having three leaflets  302 . Each leaflet  302  has a semi-triangle shape having a semi-circular base end  303 . The base end  303  is sutured on the inflow suture assembly  150 . The other two ends  304 ,  305  of the leaflet  302  are free ends. Three leaflets  302  are provided so that each free ends  304 ,  305  is located closely to the free end  304 ,  305  of the neighboring leaflet  302 . When the blood flow comes in the direction shown with the arrow B in FIG. 4A, the leaflets  302  open the spaces between the free ends  304 ,  305  by bending along the blood flow. When the blood flow comes in the other direction, the leaflets  302  close the spaces between the free ends  304 ,  305  to block the blood flow. Each leaflet  302  is preferably made of natural or artificial tissue. 
     While blood flows through the tissue valve  300 , the leaflets  302  hits the walls of the conduit within which the valve  300  is mounted by their natural movements as dictated by the blood flow. The tip of the leaflets  302  is therefore impeded and repeatedly contacted against the wall. This may wear, deformation, and eventually tear in the leaflets  302 . 
     In order to reduce the impacts on the leaflets  302 , it is preferable to provide a movable wall  152 . The movable wall  152  is attached onto the enclosure  145  by suturing assemblies  142  and  150 . 
     The movable wall  152  is preferably made of a natural or artificial tissue material. Such material is preferably grafted on a flexible, blood compatible fabric  156 , such as woven polyester velour, for further attachment within valve assembly  140 . 
     FIG. 4B shows the movable wall  152 . The movable wall  152  has a wall annulus  157  bordered by a sinusoidal wall inset  158 . The wall inset  158  forms three peaks  159 , corresponding to the three leaflets  302  of the tissue valve  300 . The wall inset  158  is made of a natural or artificial tissue material. Thus, the wall inset  158  may expand by the blood flow. 
     When blood flows through the tissue valve  300  as shown by arrow B in FIG. 4A, the movable wall  152  moves naturally as the wall inset  158  expands by the blood flow. The movement of the movable wall  152  occurs predominantly in a radial direction as the wall inset  158  is supported by the valve enclosure  145  and the wall annulus  157 . The maximum radial deflection occurs at the points farthest from the center, which are at the peaks  159  of the wall inset  158 . Thus, the tip of the leaflets  302  of the tissue valve  300  does not touch to the movable wall  152 . 
     FIG. 4C shows the valve enclosure  145 . The valve enclosure  145  comprises a cylindrical body defined by an inflow base ring  146  in the plane of the cylinder, an outflow base ring  147  forming a flange at the base of the cylindrical body and three legs  149  joining the two rings to define three side windows  148 . Preferably, the windows  148  are identical, located approximately 120° apart. 
     Referring to FIG. 4A, in accordance with a preferred embodiment of the invention, in assembling the valve assembly  140  the movable wall  152  is sutured onto the valve enclosure assembly  141  by positioning the three peaks  159  of the sinusoidal wall inset  158  in the centers of the three windows  148  of the valve enclosure  145 , respectively. A preferred embodiment also features a vertical distance gap  19  between the peaks  158  and the outflow end of the valve enclosure  145 , for allowing the wall inset  158  freedom in moving vertically, unconstrained by the valve enclosure  145 . Since the maximum deflection of the wall inset  158  occurs at the peaks  159 , this fashion of mounting the valve allows it to function in its normal free state, while also mounted in a rigid structure. 
     The inflow and outflow base rings  146  and  147 , as well as the vertical legs  149 , are provided with holes  20 ,  25  and  30 , respectively, for suturing the movable wall  152  onto the valve enclosure assembly  141  in a manner which will be described below. 
     FIGS. 4A,  4 D,  4 E and  4 F show the inflow suture assembly  150 , which comprises an inflow suture ring cover  151 . The inflow suture ring cover  151  is a rigid ring. It has holes  15  for stitching the tissue valve  300 . The inflow suture ring cover  151  corresponds to the inflow base ring  146  of the valve enclosure  145  (FIG.  4 C). The inflow base ring  146  is wrapped by the suture ring cover  151  around it. The inflow suture ring cover  151  is made from a blood compatible fabric material to be stitched around the inflow base ring  146 , in order to provide an inflow suturing support for the movable wall  152 . 
     Turning back to FIG. 4A, the outflow suture assembly  142  is sutured onto the outflow base ring  147  of the valve enclosure  145 , forming a flange  26 . Flange  26  is designed to fit smoothly into the inflow elbow assembly  170  of FIG.  2 A. The two ends of the valve assembly  140  are distinguished by the flange  26 . The flange  26  is matingly adapted only in one direction into the elbow assembly  170 . Thus, the valve assembly  140  can be installed within assembly  100  in only one way. This feature eliminates the risks of wrongly connecting the valves in the conduits in a wrong direction. The provision of the flange  26  leads to an easier, safer fitting procedure. 
     The outflow suture ring  143  is a rigid ring, of mating size with the outflow base ring  147  of the valve enclosure  145 . The outflow suture ring  143  provides an outflow suturing support for the movable wall  152  in assembling the valve assembly  140 . 
     Referring to FIGS. 4A-4E, the valve assembly  140  is assembled as follows: 
     First, the valve enclosure assembly  141  is assembled, by attaching the inflow suture assembly  150  to the outflow suture assembly  142 . As described above, the inflow suture assembly  150  comprises the valve enclosure  145  with the inflow suture ring cover  151  wrapped around the inflow base ring  146  of the valve enclosure  145 . The outflow suture assembly  142  comprises the outflow suture ring  143  with the outflow suture ring cover  144  wrapped around it. 
     Second, the movable wall  152  is placed inside the assembled valve enclosure assembly  141  with its inflow end facing the inflow side of the valve enclosure assembly  141 . 
     Third, the inflow end  153  of the grafted fabric  156  is stitched on the circumference of the inflow suture support provided by the inflow suture ring cover  151  of the inflow suture assembly  150 . 
     Finally, the outflow end  154  of the grafted fabric  156  is stitched on the circumference of the outflow suture support provided by the outflow suture ring cover  144  of the outflow suture assembly  142 . 
     In a preferred embodiment, the suturing technique is such that the suturing material, which may be thrombogenic, does not come into contact with the blood flowing through the conduit assembly. Thus, stitching occurs only on surfaces that do not contact the main blood flow stream, when in operation. A method of assembling the valve assembly  140  and its subassemblies, in accordance with such a preferred embodiment, is described in detail next. 
     Assembling the Outflow Suture Assembly 
     Referring now more specifically to FIGS. 4D and 5B and as previously described, the outflow suture assembly  142  provides a suturing support on the outflow end of the valve enclosure assembly  141 , for the modified tissue valve  152 . The support is provided through the outflow suture ring cover  144  which has to be wrapped and sutured around the outflow suture ring  143 . The ring of sutures around the periphery of the outflow suture assembly  142  thus obtained is herein denoted by I. 
     According to a preferred embodiment of the invention, the assembling of the outflow suture assembly  142  comprises the following substeps: 
     1. A rectangular strip of a biocompatible fabric is cut at a suitable size, for forming the outflow suture ring cover  144 . 
     2. The fabric forming the outflow suture ring cover  144  is wrapped around and held tight against the inside surface of the outflow suture ring  143  with the excess material lying outside the outflow suture ring  143 . 
     3. Using a surgical suture, a first stitch is made at the edge of the fabric forming outflow suture ring cover  144 . When passing the needle, one should preferably make sure that it is directly against the outer surface of the outflow suture ring  143  through both the upper and lower layer of the outflow suture ring cover  144 . The initial knot is started by passing the needle through the two layers twice in the same location. During the second pass, while the needle is still part way through the outflow suture ring cover  144 , the suture line is wrapped around the needle twice, the needle is pulled through the double loop, and then the knot is tightened. 
     4. A stitch is passed back through both layers of the outflow suture ring cover  144  with a stitch length of 5+/−1 mm, still being careful to have the needle directly against the outer surface of the outflow suture ring  143 . Reversing the stitch direction, a stitch is made back through where the stitch initially started. When the stitch comes through the outflow suture cover ring  144 , one makes sure the stitch passes between the previous stitch and the outflow suture ring  143  so that the suture line is not cut by the needle and the stitch remains tight. 
     5. A stitch is passed through both layers of the outflow suture ring cover  144  with a stitch length of 7+/−1 mm. 
     6. With a stitch length of 5+/−1 mm, the direction is reversed and a stitch is passed through the outflow suture ring  143 . A cover is made so that the suture emerges near the previous stitch. Again, for the reverse direction stitch, the needle is passed between the previous suture line and the outflow suture ring  143 . 
     7. The sutures are continued with a stitch length of 5+/−1 mm, continuously ensuring that the outflow suture ring cover  144  stays tight against the inside surface of the outflow suture ring  143 . 
     8. Once the outflow suture ring cover  144  has been sutured around the entire circumference of the outflow suture ring  143 , the outflow suture ring cover  144  is cut to length such that the two edges of the outflow suture ring cover  144  abut against each other. 
     9. Two additional stitches are made across the gap in the outflow suture ring cover  144 , then the suture is tied off with two double finishing knots, a final stitch is passed underneath the knot with each line and then cut the suture at the surface of the outflow suture ring cover  144  using the surgical scissors with the rounded cutting edge. 
     10. The outflow suture ring cover  144  is cut 1.0-2.0 mm outside of the periphery of the completed ring of sutures. 
     11. Using a soldering iron set to 277+/−10° C., the seam is welded along the two edges of the outflow suture ring cover  144  starting at the interior surface and working in the radial direction, being careful not to touch the suture material which could melt and break upon contact. 
     12. In a similar manner, the soldering iron set to 277+/−10° C. is used to weld the seam along the outer periphery of the outflow suture ring assembly  142 . 
     Assembling the Inflow Suture Assembly 
     Referring now more specifically to FIGS. 4A,  4 C,  4 F and  5 A and previously described, the inflow suture assembly  150  provides a suturing support on the inflow end of the valve enclosure assembly  141 . The support is provided by the inflow suture ring cover  151  which has to be wrapped and sutured around the inflow base ring  146  of the valve enclosure  145 . According to a preferred embodiment of the invention, the assembling of the inflow suture assembly  150  comprises the following substeps: 
     A) A first ring of sutures II is made in order to attach the inflow suture ring cover  151  to the inflow base ring  146  of the valve enclosure  145 , by passing a surgical suture through the holes  20  in the inflow base ring  146 . In detail, this may be done as follows: 
     1. A piece of uncrimped fabric shaped into a conduit having a diameter approximately equal to the diameter of the movable wall  152  and to the internal diameter of the valve enclosure  145 , is fed through the valve enclosure  145  and wrapped around the inflow base ring  146  of the valve enclosure  145  such that 5.0+/−1.0 mm is hanging over the outside portion of the valve enclosure  145  and the remainder of the uncrimped fabric conduit is within the valve enclosure  145 . In this embodiment, the uncrimped fabric conduit forms the inflow suture ring cover  151 . 
     2. A cylindrical rubber stopper is placed into the valve enclosure&#39;s  145  inflow orifice to hold the inflow suture ring cover  151  in place. 
     3. Using a surgical suture, the suturing of the inflow suture ring cover  151  to the valve enclosure  145  is started through one of the holes  20  in the inflow base ring  146 . Preferably, this stitch should start from the outside traveling towards the inside. 
     4. The suture is then taken through the adjacent hole  20  from the inside out. 
     5. The two ends of the sutures are tied off with two double knots that are made on the inflow suture ring cover  151  in between two holes  20  on the inflow base ring  146  on the external surface of the valve enclosure  145 . The sutures are tied off such that there are approximately equal lengths of suture on either side of the knot. 
     6. The knot is tightened so that it resides over one of the two holes  20  in the inflow base ring  146  that have just been tied off. 
     7. The next suture is started with the last hole  20  that was used coming from the outside in and then bringing the suture back out in the adjacent hole  20  in a similar manner as before. 
     8. Continue making sutures until all holes  20  are stitched. 
     9. Once the final knot has been tied around the periphery of the component, the two ends of the suture are left as they will be used later. 
     B) A second ring of sutures III is made in order to suture the inflow suture ring cover  151  closed where the two portions of the fabric conduit come together. In detail, this may be done as follows: 
     10. The fabric conduit making the inflow suture ring cover  151  is cut to the same length on the internal side of the valve enclosure  145  as the fabric is overhanging on the external side of the valve enclosure  145 . 
     11. The suture line is passed underneath the external layer of the fabric conduit so that it emerges near the edge of the uncrimped fabric conduit using the longer portion of the suture left from point  9 . Then, starting from the outside and working towards the center, a stitch is passed through both layers of the conduit uncrimped fabric to start the stitch. 
     12. As the stitch is being made, a knot is tied to complete each stitch. This can be done by wrapping the suture line around the needle before the needle is completely pulled through the material. 
     13. The suturing is continued around the periphery of the uncrimped fabric conduit with 3-5 mm long stitches located on average ˜2.0-2.5 mm apart. 
     14. When crossing between two of the windows  148  in the valve enclosure  145 , a single stitch is made, that starts at one edge of the window that has just been completed, which passes under the fabric conduit on the external side of the valve enclosure  145 , and emerges at the edge of the next window  148  on the valve enclosure  145 . 
     15. The suture is finished off by making a single stitch back down near the original knot at the bottom of the fabric conduit and then make two double knots, and then feeding the two ends of the suture through the fabric under the knot, and then cutting the ends of the suture. 
     16. Once the suture is completed around the base of the uncrimped fabric conduit making the inflow suture ring cover  151 , a soldering iron at 277+/−10° C. is used to weld the seam shut, being careful not to contact the suture which could melt. 
     Assembling the Valve Enclosure Assembly 
     Referring now more specifically to FIGS. 4C,  4 D and  5 B, as previously described, the assembling of the valve enclosure assembly  141  consists in attaching the inflow suture assembly  150  and the outflow suture assembly  142  together. In this embodiment, this is accomplished by the suture technique described in detail below, the result of which is a new ring of sutures IV, obtained by passing a suture through the holes  15  in the outflow suture assembly  142  and the holes  25  in the outflow base ring  147  of the valve enclosure  145 . 
     1. The assembled outflow suture ring assembly  142  is positioned over the outflow base ring  147  of the valve enclosure  145 , so that their sets of holes,  15  and  25 , respectively, overlap. 
     2. Using a surgical suture, the suture is started by passing a stitch through the holes  15  in the outflow suture ring assembly  142  and through the holes  25  in the outflow base ring  147  of the valve enclosure  145  and then passing the other needle through the adjacent pair of holes  15 ,  25  in the outflow suture ring assembly  142  and the outflow base ring  147 , respectively. 
     3. The two free ends are tied with two double knots and the resulting knot is located directly over one of the hole-pairs  15 ,  25 . 
     4. One end of the suture is passed through the hole-pair  15 ,  25  where the last knot was located and the suture is brought back through the adjacent hole-pair  15 ,  25 . 
     5. The two loose ends of the suture are tied off with two double knots and the knot is located directly over the holes  15 ,  25 . 
     6. The suturing of the outflow suture ring assembly  142  to the valve enclosure assembly  141  is continued through the eighteen hole-pairs  15 ,  25 . 
     7. Once the suturing is completed, the suture line is passed down through the last hole  25  of the valve enclosure  145  but not through the corresponding hole  15  of the outflow suture ring assembly  142 . The suture line is passed between the valve enclosure  145  and the outflow suture ring assembly  142  to the outside edge of the components. The suture is tied off on the outside edge of the outflow suture ring assembly  142  so that the knot is not located on the flat bottom of the component. 
     8. After the knot is tied, a stitch is passed under the knot and then the suture is cut close to the surface using the surgical scissors with the rounded cutting edge. 
     Assembling the Valve Assembly 
     Referring now to FIGS. 4A,  4 B,  5 A and  5 B and as previously described, the final steps in assembling the valve assembly are the suturing of the movable wall  152  inside the assembled valve enclosure assembly  141 . This involves three main steps, as described next: 
     A) The movable wall  152  is placed inside the assembled valve enclosure assembly  141  with its inflow end facing the inflow side of the valve enclosure assembly  141 . In detail, this can be accomplished as follows: 
     1. A suitable movable wall  152  as previously described is removed from sterile water and its grafted fabric  156 , shaped into a conduit, is cut approximately 5 corrugations above and below the tissue valve,  153 ,  154 . 
     2. The movable wall  152  is then inserted into the assembled valve enclosure assembly  141  such that each of the peaks  159  of the wall inset  158  lies centered within the window  148  of the valve enclosure  145  and the peak  159  of the wall inset  158  lies 1-2 mm above the outflow side of the window  148  of the valve enclosure  149 . The movable wall  152  is in the proper orientation when the peaks  159  of the valve leaflets are pointing towards that outflow suture ring assembly  142 . 
     B) The inflow end  153  of the grafted fabric  156  is stitched on the circumference of the inflow suture support provided by the inflow suture ring cover of the inflow suture assembly  150  by creating a new ring of sutures V. In detail, this can be accomplished as follows: 
     3. The movable wall  152  is trimmed so that it is flush to the base surface of the inflow orifice of the valve enclosure assembly  141 . The inflow orifice should preferably be approximately 1.5 corrugations  153  above the inset  158  of the movable wall  152 , as shown in FIG.  4 B. 
     4. While ensuring to keeping the fabric taut, using a surgical suture, the stitch starts by passing a suture from the outer periphery of the valve enclosure assembly  141 , through the inflow suture ring cover  151  and back out through the movable wall  152 , as close to the valve enclosure  145  as possible, and then a double knot is made. Preferably the knot should be located on the outside edge of the valve assembly  140 . 
     5. A continuous stitch, forming a new ring of sutures V, with stitches approximately 5 mm long and 2-3 mm apart is made around the inflow periphery of the valve enclosure assembly  141 , making sure that the stitch lies on the upper surface of the valve enclosure assembly  141 , for a total of approximately 30-50 stitches. 
     6. Once the continuous stitch has returned to the starting position, it shall be tied off with the starting loose end using two double knots. 
     7. After the knot has been tied, both loose ends of the suture are passed through the uncrimped conduit, under the knot and then cut with the surgical scissors with the rounded cutting edge. 
     C) The outflow end of the grafted fabric  156  is stitched on the circumference of the outflow suture support provided by the outflow suture ring cover of the outflow suture assembly  142 , by creating a new ring of sutures VI. In detail, this can be accomplished as follows: 
     9. The valve assembly  140  is turned over and the outflow orifice of the modified tissue valved  152  is trimmed down flush to the outflow suture ring  143  surface using the scalpel, leaving approximately 2.5 graft corrugations  154  between the peaks  159  of the wall inset  158  and the end of the fabric  156  of the movable wall  152 . 
     10. Using a surgical suture a stitch is started by passing the suture line from the outside of the valve assembly  140 , in through the outflow suture ring assembly  142  and out through the fabric  156  of the movable wall  152 . This stitch should be made in between the ring of suture IV holding the outflow suture ring assembly  142  to the valve enclosure  145  and the ring of suture I holding the outflow suture ring assembly  142  together. 
     11. A continuous stitch, forming a new ring of sutures VI, is made with stitches approximately 5 mm in length and 2-3 mm apart around the outflow orifice (for a total of 30-50 stitches) ensuring that the stitch is made on the flat surface of the outflow suture ring assembly  142 . Care must be taken to ensure the grafted fabric  156  conduit is stretched to fit the valve enclosure  145 . 
     12. The suture is finished in a manner similar to that described above for the assembling of the inflow suture assembly  150  in steps 7-9. 
     D) In this embodiment, the movable wall  152  is also attached midways to the valve enclosure, by suturing its grafted fabric to the legs  149  of the valve enclosure, through the holes  30  provided in the legs. In more detail, this can be accomplished as follows: 
     13. The final sutures will be done through the holes  30  in the legs  149  of the valve enclosure  145 . 
     14. A stitch is passed from the outside of the valve enclosure  145 , through one of the holes  30  and the modified valved conduit and then back out the adjacent hole  30 . 
     15. The two free ends of the suture are tied with three double knots and then the free ends of the suture will be cut off leaving approximately 3 mm of length at the end of the lines. 
     16. Steps 14-15 are repeated for all three sets of holes  30  in the legs  149  of the valve enclosure  145 . 
     E) The valve enclosure  145  is visually inspected, and stored in a container. 
     F) A small portion of the graft conduit  156  that was trimmed off at substep 3 (approximately 1×2 cm) is cut and placed this into the container with the valve assembly  140  for future bacteria cultures. 
     Although a suturing technique has been described above in detail, it will to be appreciated by one skilled in the art that this description only pertains to a specific embodiment of the invention. Other suturing techniques may be employed for the assembling of the various components and for attaching the movable wall  152  to the valve enclosure assembly  141 . Moreover, other methods of attachment known in the art, such as glueing, can be used in assembling the various parts of the valve assembly  140  together. 
     Turning back to FIG. 2A, the valve assembly  140  is mounted on the inflow conduit assembly  100  by sliding its inflow end into enlarged elongated cylindrical opening of the apical tip assembly  110 , and its outflow end with flange  26  into the inflow elbow assembly  170 . 
     Referring now to FIG. 2B, as indicated above, the outflow valve assembly  240  is identical in structure to the inflow valve assembly  140 . The outflow valve assembly  240  is mounted into the outflow conduit assembly  200  by sliding its outflow end with flange  27  into the outflow conduit  210  and its inflow end into enlarged elongated cylindrical opening of outflow elbow assembly  270 . 
     Numerous modifications, variations, and adaptations must be made to the particular embodiments of the invention described above, without departing from the scope of the invention, which is defined in the claims.