The presence of an obstruction in the outflow tract of the right ventricle (RV) consists of a relatively common defect, present in 20% to 30% of cyanotic congenital heart diseases. The extreme degree of pulmonary obstruction is pulmonary atresia (anatomical discontinuity between RV - Pulmonary Artery), present in approximately 5% of patients with heart defects. In these situations, surgical treatment may require the use of a prosthesis or implantation of a valved conduit to reconstruct the pulmonary valve and outflow tract of the RV. Different valve replacements have been proposed, including the fresh aortic homografts, pulmonary heterografts, pig or bovine pericardial prostheses. Amongst the valved conduits we have: bovine pericardial grafts, porcine pulmonary graft, bovine jugular containing Dacron prostheses, aortic homograft, or more recently, pulmonary homografts. Mechanical prostheses were virtually abandoned. Whichever type of replacement valve used, many studies have reported calcification or tissue degeneration associated to pseudo-intimal proliferation and progressive obstruction of the conduit , , , ,  with the need for reoperation, the incidence of which may vary between 14% and 30% at 5 years and 32% to 100% at 10 years. , , , ,  In 1991, we began a new experience in the Cardiovascular Division of the Federal University of São Paulo (Unifesp), using 2 models of biological prostheses: heterografts (swine) treated with glutaraldehyde and formaldehyde , adding in recent years other 2 models. These 4 different prostheses were implanted in 203 children with heart defects that required reconstruction of the pulmonary valve and right ventricular outflow tract.  The late outcome of these patients is represented by actuarial Kaplan & Meier curve: The survival of these patients was 86.6% operated and free reoperations in 68.3% of cases, in 180 months of median rate of follow-up. (Figure 1 ) The most frequent cause of reoperations was calcification, tissue degeneration and loss of function due to growth of the patient.
The implantation of a bioprosthetic porcine valve in a patient, is considered as a form of living tissue transplantation. Xenotransplantation, which usually has a very aggressive form of rejection by the immune system of the patient. Aiming to reduce this type of immunogenicity, bioprostheses are fixed in glutaraldehyde solution, with the intention of transforming the tissue graft immunologically inert.
However, bioprostheses that were fixed in glutaraldehyde also have the propensity to calcify. This calcification is a major contributor for dysfunction of cardiac bioprostheses due to the pre-treatment of biological tissue with glutaraldehyde to devitalize the cells ceasing residual cells that become the primary sites for deposition of calcium phosphate. The reaction of calcium with the extracellular fluid associated with the reactions of phosphorus to the cell membrane causes pathological calcification of bioprostheses.
Despite the deterioration of the heterograft keeps the order of 35% to 45% in 15 and 20 years, respectively. There are always isolated cases with long postoperative course, without compromising tissue or calcification of porcine bioprostheses. .
During the last decade there was an excellent immediate biocompatibility of
More than 50 years of research has been devoted to this area, which led to an understanding of the synthesis, structure and properties of these fascinating materials. In general, the
2. Objectives of research
The objectives of this study are:
To build a heart prosthesis of
Drawing in 3D of a human aortic valve, obtained from an examination of Angio-Computerized Tomography (Angio-CT)
Matrix of the prosthesis.
Prepare of segmented polyurethane (SPU).
Manufacture of prosthesis by injection of SPU in the matrix.
2.2. Building a model of segmented
Design of the prosthesis in 3 D and Manufacturing of Moulds:
The 3-D drawing for manufacturing of the
We considered internal and external diameter, shape of the ring and stem where they operate the valve leaflets.
The valve leaflets were preserved, an angle of 120° from the place of central coaptation to the base of the valve ring deployment. Each leaflet has a thickness in the central region of the free edge of 0.2 mm and 0.5 mm in the rest of the extension. The program to be used for the design of this prosthesis is generated by Solid Works software, the computer program generates mesh and solid parametric.
Modeling of the Ring and Membrane
From pre-established dimensions by Angio-CT, the software was modeled using the ring and the membranes of the 3 cusps. figures 2,3,4
Drawing of the Ring
Making the Matrix
The array was fabricated on a machine called "Vertical Machining Center". It is nothing more than a machine tool with computer numerical control. Utilizing cutting tool, and stainless steel plant directly. Figures: 5,6,7
Manufacturing segmented polyurethane prostheses
Among the polymeric materials used in clinical practice,
Manufacturing prostheses by injection of PCU matrix
In this design, it is intended to prepare
The membranes obtained under different conditions are identified, using the techniques of X-ray diffractometry, differential scanning calorimetry and dynamic mechanical thermal analysis, among others. Additionally, ultrasound technique allows the analysis for the presence of defects in 100% of the membranes to be employed in the construction of prosthetic heart
3.1. Durability of
polyurethaneprosthesis tested “ in vitro”