Title of Invention

"Artificial Heart Valve"

Abstract

An artificial heart valve for human patients is disclosed. The valve comprises a valve body having an interior valve surface of generally tubular cross section defining a central passageway for blood flow therethrough, an annulus at one end of the valve body and at least three relatively flexible cusps moveably mounted within said valve body on said annulus to alternately move between an open position to permit blood flow downstream through said valve body and a closed position to prevent blood flow upstream through said valve body, said at least three cusps representing three cut away portion of an imaginary circle in its cross section such that in closed position, the three cusps form substantially a circular cross section closing the valve passageway and prevent flow of blood upstream of said valve body. Said valve body, said annulus and said three cusps are integral with each other and are made of a blood-compatible synthetic material, the exterior of said valve body being sinusoidal so that said valve physically and in terms of its construction resembles a human valve.

Full Text

Artificial Heart Valve Field of the invention The present invention relates to artificial aortic heart valve. More particularly, the present relates to artificial heart valves that simulate human aortic valves and resemble human aortic valve both in terms of design and function. Background of the invention A wide variety of artificial heart valves are known in the prior art for the replacement of natural art valves, which are no longer capable of performing their normal functions. In fact, the prior heart teaches a variety of mechanical or prosthetic heart valves for operating hemodynamically in conjunction with the pumping action of the heart. Typically such valves comprise of a valve body and valve members capable of opening in a single direction. Such valve members or occluders may be in the form of a single leaflet or multiple leaflets. These leaflets are hinge mounted in a such a way that they hinge along eccentric axes to open and close a central blood passageway. In its open position, the prosthetic heart valve should ideally provide a central blood passageway with good flow characteristics so that the blood flows freely through the passageway with minimum drag or obstruction. A prosthetic heart valve mounted at the aortic position should be very responsive to blood flow. It should be capable of opening quickly during the pumping stroke of the heart and closing quickly when the heart relaxes so that regurgitation or reverse flow of the blood is avoided. The opening and closing of the valves should also be soft as the wings of a butterfly so that the patient is not unduly disturbed by the unwanted sounds. The components of the valve are required to be made of bio-compatible material and in the mounted position, should be completely washed by blood so that stagnation of blood in the crevices of the valve and their eventual clotting is avoided. Most importantly, the prosthetic heart valve should be capable of opening and closing countless number of times without jamming or malfunctioning. Towards achieving some of above mentioned requirements, the prior art teaches a variety of designs and construction for heart valves. For example, US Patent 4,272,854 (June 16, 1981) teaches a bileaflet heart valve having an ear extending from each lateral side of each leaflet. The ear pivots in a recess and is guided in part by a knob traveling in a longitudinal slot that is cut more deeply into the sidewall of the valve body. US Patent 4,363,142 (December 14, 1982) discloses a bileaflet heart valve wherein the leaflets have laterally extending ears in the form of generally oval or spherical projections that are received in recesses of complementary design. US Patent 4,373,216 (Febraury 15, 1983) discloses a bileaflet heart valve wherein protrusions extend generally radially inward from a pair of flat sidewall sections of the valve Artificial Heart Valve Field of the invention The present invention relates to artificial aortic heart valve. More particularly, the present relates to artificial heart valves that simulate human aortic valves and resemble human aortic valve both in terms of design and function. Background of the invention A wide variety of artificial heart valves are known in the prior art for the replacement of natural art valves, which are no longer capable of performing their normal functions. In fact, the prior heart teaches a variety of mechanical or prosthetic heart valves for operating hemodynamically in conjunction with the pumping action of the heart. Typically such valves comprise of a valve body and valve members capable of opening in a single direction. Such valve members or occluders may be in the form of a single leaflet or multiple leaflets. These leaflets are hinge mounted in a such a way that they hinge along eccentric axes to open and close a central blood passageway. In its open position, the prosthetic heart valve should ideally provide a central blood passageway with good flow characteristics so that the blood flows freely through the passageway with minimum drag or obstruction. A prosthetic heart valve mounted at the aortic position should be very responsive to blood flow. It should be capable of opening quickly during the pumping stroke of the heart and closing quickly when the heart relaxes so that regurgitation or reverse flow of the blood is avoided. The opening and closing of the valves should also be soft as the wings of a butterfly so that the patient is not unduly disturbed by the unwanted sounds. The components of the valve are required to be made of bio-compatible material and in the mounted position, should be completely washed by blood so that stagnation of blood in the crevices of the valve and their eventual clotting is avoided. Most importantly, the prosthetic heart valve should be capable of opening and closing countless number of times without jamming or malfunctioning. Towards achieving some of above mentioned requirements, the prior art teaches a variety of designs and construction for heart valves. For example, US Patent 4,272,854 (June 16, 1981) teaches a bileaflet heart valve having an ear extending from each lateral side of each leaflet. The ear pivots in a recess and is guided in part by a knob traveling in a longitudinal slot that is cut more deeply into the sidewall of the valve body. US Patent 4,363,142 (December 14, 1982) discloses a bileaflet heart valve wherein the leaflets have laterally extending ears in the form of generally oval or spherical projections that are received in recesses of complementary design. US Patent 4,373,216 (Febraury 15, 1983) discloses a bileaflet heart valve wherein protrusions extend generally radially inward from a pair of flat sidewall sections of the valve body guide valve members which have slots in their lateral edges which fit about such protrusions. US Patent 4,451,937 (June 5, 1984) shows a generally similar bileaflet heart valve where the pivot arrangement is formed with a reversal of these parts so that the leaflets have laterally protruding ears which are received within the slot and also in US Patent 4,443,894 (April 24, 1984) wherein the slots are of kidney bean shape. US Patent 4,808,180 (February 28, 1989) discloses a bileaflet heart valve wherein the leaflets each have a semiconical shape. By virtue of such shape, they inherently provide significant resistance to blood flow through the valve in the open position. The leaflets are guided by generally C - shaped rails that protrude from the valve body sidewall and are received in recesses of complementary shape in the lateral edges of the semi-conical leaflets. US Patent 5,207,707 (January 16, 1992) discloses a trileaflet heart valve wherein the leaflets translate between open and closed positions guided by ears. These ears travel along curved grooves carved in "walls of a pivot structure which are open at their downstream ends. US Patents 4,820,299 and 5,123,918 also disclose similar trileaflet prosthetic heart valves. US Patent 5,123,918 illustrates a construction wherein specially configured edge guides arcs are formed in the respective faces of three triangular projections that protrude from the interior surface of the valve body. These arcs extend from the downstream edge of the valve body in a circular section that swings radially inward and then back in a direction toward the interior surface of the valve body and they guide such leaflets in moving between the open and the closed positions. Commercially developed mechanical heart valves have frequently employed valve members oriented at a significant angle to the valve centerline in the open position, so that when backflow of blood begins, it preferentially impinges strongly upon the outflow surfaces of such valve members. This arrangement initially imparts a strong pivotal force component in the direction of the closing movement which contributes to prompt closing and minimal regurgitation. It is now felt that it is particularly important for a mechanical heart valve prosthesis to provide a passageway through which blood can freely flow in the open position with a rriinimum of drag, and to accomplish this desired objective, it is presently believed that valve members should be able to follow the flow and, when required assume orientations parallel or nearly parallel to the longitudinal axis of the passageway. Of course such valves should promptly close with only a small amount of regurgitation and without creating any significant cavitation. According to US Patent No. 6.059,826 (May 9, 2000), it is particularly important for a mechanical heart valve prosthesis to provide a passageway through which blood can freely flow in the open position with a minimum of drag, and to accomplish this desired objective, it is presently believed that valve members should be able to follow the flow and, when required assume orientations parallel or nearly parallel to the longitudinal axis of the passageway. Of course such valves should promptly close with only a small amount of regurgitation and without creating any significant cavitation. Accordingly, US Patent No. 6,059,826 discloses a trileaflet heart valve which includes a generally annular valve body having an interior wall of normally circular cross section into which extend three wedge shaped projections. These wedge shaped projections provide three pairs of flanking flat surfaces between which three leaflets are pivotably supported. While the valve taught by the aforesaid US Patent addresses some of the prior art problems, the major disadvantage associated with the mechanical valves still remains. Mechanical heart valves are quite durable but require continuous anticoagulation therapy to prevent blood clotting. Prior art also teaches a "ball and cage" type prosthetic heart valve which essentially comprises of a ring or annulus the inner diameter of which is substantially equal to the inner diameter of the blood vessel. A ball made of synthetic material sits on the annulus, the diameter of the ball being such that it sits firmly on the annulus but does not pass through it. The misalignment of the ball from the annulus is prevented by a wire cage supported on the annulus in such a manner that the ball is capable of one way vertical movement inside the cage but is incapable of falling off the annulus. Other types of mechanical valves are tilting disc and bileaflet valves but again these valves suffer from the disadvantage that they are expensive and require life long anticoagulation therapy to prevent blood clotting which can be hazardous. Therefore, there has been an increased preference to "bioprosthetic" or tissue valves. Unfortunately, the commonly employed "bioprosthetic" or tissue valves also have their limitations. One of the serious disadvantage reported is the homografts from human donors are extremely difficult to obtain in exact sizes. They are difficult to sterilise and have to undergo numerous tests to rule out chances of infections and donor incompatibility. Therefore, prior art also envisages "xenografts", i.e., bioprosthesis obtained from non human donors such as pigs, cattle, ostriches and kangaroos. Xenografts offer a better alternative to homografts because of their easier availability in higher numbers in variety of sizes. Animal valves are commonly trimmed to size by cutting away the aortic valves between the leaflets and leaving only the tissue to which the leaflets are attached. These tissue are then supported by metallic or plastic stents. These stents are frames which support the tissues that form the valve and are covered by cloth. The stent is often augmented by an annular ring usually sewn to the exterior of the prosthesis to aid in the surgical attachment of the prosthesis to the patient's aorta. These unfortunately occupy space leading to the reduction in size of the patient's annulus which in turn leads to increased blood turbulence. Also, the stents tend to be rigid. As a result, much of the "shock" of the opening and closure of the valves are absorbed by the leaflets, thereby greatly reducing their life. Towards overcoming some of the disadvantages of stents, US Patent No. 6,364,905 (April 2, 2002) discloses stentless valves of mammalian origin. While such stentless valves do overcome some of the disadvantages of the mechanical valves, they are of animal origin and are sometimes liable to be rejected by the patient's body. Also there are increased incidents infections hitherto thought to be unique to animals being transmitted to humans. Thus, prosthetic valves of animal origin always present a severe danger of either passing on some dreadful infection to the patient or being entirely rejected by the patients' body. Chemical treatments to render them inert reduces their life span to less than 20 years rendering them suitable only for patients over 60 years of age. Another alternative is the homografts obtained from human cadavers and autografts obtained from the patients themselves. From a cadaver heart, aortic, pulmonary and Mitral valve homografts may be taken out and sterilised, stored and used for replacement in a patient. However, these valves face a tremendous short supply. These may function for 20 to 25 years. Although, they are the best substitute for the diseased valves, their limited supply and need for technical skills in implanting them make them unavailable to most patients. In addition, tissue valve bank facility has to be developed to sterilise and store these valves. Objects of the invention It is therefore the primary object of the present invention to provide prosthetic valves which overcome the disadvantages of the prior art valves. It is another object of the present invention to provide prosthetic valves which are easy to use, simple to produce and which simulates the functions and appearance of the human heart valve. It is yet another object of the present invention to provide prosthetic valves, which do not employ any metal parts. It is yet another object of the present invention to provide prosthetic valves, which are one piece integral valves incapable of jamming during operation. It is another important object of the present invention to provide prosthetic valves, which are of non animal origin. It is still another important object of the present invention to provide prosthetic valves, which do not require the use of any anti-coagulants. Summary of invention The above and other advantages of the present invention are achieved by the artificial valve of the present invention which simulates and is an exact copy of the natural aortic valve. Accordingly, the present invention provides an artificial heart valve for human patients which comprises, valve body having an interior valve surface of generally tubular cross section defining a central passageway for blood flow therethrough, an annulus at one end of the valve body and at least three relatively flexible cusps moveably mounted within said valve body on said annulus to alternately move between an open position to permit blood flow downstream through said valve body and a closed position to prevent blood flow upstream through said valve body, said at least three cusps representing three cut away portion of an imaginary circle in its cross section such that in closed position, the three cusps form substantially a circular cross section closing the valve passageway and prevent flow of blood upstream of said valve body. The said valve body, said annulus and said three cusps are integral with each other and are made of a blood-compatible synthetic material, the exterior of said valve body being sinusoidal so that said valve physically and in terms of its construction resembles a human valve. In a preferred embodiment, said bio-compatible synthetic material is expanded polytetrafluoroethylene (EPTFE). Detailed description The present invention will now be described in detail with reference to the accompanying drawings wherein: Fig. 1 shows the artificial valve of the present invention in its cross section; Fig. 2 shows a longitudinal section of the valve of the present invention; Fig. 3 shows a vertical view of the valve of the present invention; Fig. 4 shows a perspective view of the valve of the present invention; Fig. 5 shows another view of the valve of the present invention with the cusps in a closed position. As shown in the figures, where like parts are shown by like reference numerals, the valve of the present invention has a valve body 1 made of a bio compatible material such as expanded polytetrafluoroethylene (EPTFE). The valve body has an interior valve surface of generally tubular cross section (Figs. 1 to 3) which defines a central passageway for blood flow therethrough. An annulus 2 made of the same material as the valve body 1 is located at one end of the valve body. The valve comprises at least three relatively flexible cusps 3 moveably mounted within said valve body 1 on said annulus 2 (Figs. 1 to 3) to alternately move between an open position (Fig.4) to permit blood flow downstream through said valve body and a closed position (Fig. 5) to prevent blood flow upstream through said valve body. The said at least three cusps represent approximately one third portion each of an imaginary circle in its cross section such that in closed position, the three cusps form substantially a circular cross section closing the valve passageway and prevent flow of blood upstream of said valve body. It is an important feature of the invention that said valve body, said annulus and said three cusps are integral with each other and are made of a blood-compatible synthetic material. It is another important feature of the invention that the exterior of said valve body is sinusoidal so that said valve physically and in terms of its construction resembles a human valve Thus, the artificial valve of the present invention has the following parts: Annulus, three siemilunar cusps, sinuses and a conduit tube similar to the aortic valve and aorta in a human. It is designed from known dimensions of the above parts in human hearts measured by various imaging techniques such as echocardiography, MRI scanning and the like. The dimension in various age sizes in cadaver hearts is also available from published data. To anchor the valve to the heart the inlet portion of the valve body is extended for 2 -3 mm in a circumferential manner providing a cuff for suture. The extension will be from the same material and will be an integral part of the valve of the present invention. The material for the artificial valve of the present invention is Expanded PolyTetraFluroEthylene (EPTFE). Other inert bio compatible synthetic material may be used but EPTFE is the most preferred material. The valve of the present invention conveniently employs this material to reproduce the entire construction of a human valve without employing any stents or other material. This material has been demonstrated to satisfy the following requirements for synthetic blood conduits such as: (a) chemical inertness; (b) resistance to dilatation; (c) biocompatibility with tissue and blood elements which are prerequisites for such a valve. When used alone in fabricating this valve it will provide uniform structure and will have the above mentioned properties. This integral monomaterial design will eliminate the drawbacks of combining different materials in a design. PTFE is available as a resin. The manufacturing process is by paste extrusion and Die casting. The die is made to exact measurements obtained from normal living and cadaver Aortic and Mitral valves and includes in design all of the components of the design described earlier. It is made in different sizes and lengths to suit each individual patient's needs. Cusps made frm PTFE and mounted on a frame with a cloth sewing ring were tested in earlier experiments. Although the material performed reasonably, the combination of different materials and the design which copies only partially the natural valve design failed to perform satisfactorily. These drawbacks with PTFE valves tested so far are overcome in the present invention using a single material without suture, stent and obstructive sewing rings. Advantages of the invention The valve of the present invention based entirely on natural design using a single, blood compatible material already tested in the human circulation will have the following advantages: (a) in function such a valve will have the natural physical and physiological properties and therefore will function like the natural valve; (b) the material is blood compatible and will not require lifelong anti-coagulation; (c) there is no likelihood of sudden mechanical failure as happens with prosthetic and bioprosthetic valves, because there are no mechanical parts; (d) this will not produce any annoying noise; (e) it allows endothelial growth and therefore, thromboembolic complications are unlikely; (f) it will be less expensive than currently available substitutes (g) it can be impregnated with antibiotics to make it infection resistant; (h) it will not cause genetic abnormalities in the fetus when implanted in pregnant women. We claim: 1. An artificial heart valve for human patients which comprises, valve body having an interior valve surface of generally tubular cross section defining a central passageway for blood flow therethrough, an annulus at one end of the valve body and at least three relatively flexible cusps moveably mounted within said valve body on said annulus to alternately move between an open position to permit blood flow downstream through said valve body and a closed position to prevent blood flow upstream through said valve body, said at least three cusps representing three cut away portion of an imaginary circle in its cross section such that in closed position, the three cusps form substantially a circular cross section closing the valve passageway and prevent flow of blood upstream of said valve body. 2. An artificial heart valve as claimed in claim 1 wherein said valve body, said annulus and said three cusps are integral with each other and are made of a blood-compatible synthetic material. 3. An artificial heart valve as claimed in claim 1 or 2, wherein the exterior of said valve body is sinusoidal. 4. An artificial heart valve as claimed in any preceding claim wherein said valve is made of a chemically inert material with high degree of resistance to dilation. 5. An artificial heart valve as claimed in claim 4 wherein said material is polytetrafluoroethylene. 6. An artificial heart valve for human patients substantially as herein described with reference to and as illustrated in the accompanying drawings.

Documents:

675-del-2002-abstract.pdf

675-del-2002-claims.pdf

675-del-2002-correspondence-others.pdf

675-del-2002-correspondence-po.pdf

675-del-2002-description (complete).pdf

675-del-2002-description (provisional).pdf

675-del-2002-drawings.pdf

675-del-2002-form-1.pdf

675-del-2002-form-19.pdf

675-del-2002-form-2.pdf

675-del-2002-form-3.pdf

675-del-2002-form-4.pdf

675-del-2002-form-5.pdf

675-del-2002-gpa.pdf