BioProsthetic Heart values: Impact of implantation on   biomaterials

Biomaterials are an any surface, which that interacts with the biological systems. These biomaterials are used in the range of science such as biological, chemical, physical. This prosthetic heart values are used in the treatment of the diseased and difunctional. These prothetic values are classified into 2 ways such as the MHV's and BHV's.

            The MHV's Standard form is Mechanical Heart Values.which is made up of synthetic material, and also more durable. BHV's Standard Form is Bioprosthetic Heart Values. These are made up of biological tisues and mainly used for the implant functionality.

            The classification of the bioprosthetic values are in 4ways: these are mainly done in homograft and xenograft. The Homograft is for the human. And where as in the case of Xenograft is for animal issues. This homograft is mainly occurs in the childrens. The xenograft is developed from the animal tissues. Bovine pericardial valve are the design's whicah are similar to porcine value, which imitates the tricuspid aortic valve. Stentless valves are in MHV's (Mechanical Heart values), these are made by removing the porcine aortic root and adjacent aorta en-block.

            The changes of the biomaterials are broadly classified inti two components such as Biological Component and Non-Biological Component. The tissues are removed from the heart such as Porcine, Bovine or Cadavertic are cleaned, sized and fixed in different ways. This leads to the changes in biomaterials.

            The Handlings of the biological tissues are harvested by processing within 24hrs. the handling the tissue values are treated with antimineralisation agents to reduce the tissue certification. In handling this tissues BHF failure may occur due to general causes of the factors that are specified for the particular device.

            The valve and preimplanation factors are classified by the folowing:

Cryopreservation:

            In this allograft cryopreserved are stored for more than one year tend to have and thin flat cusps with obliterature of the usual corrugations. This process in the tissues are rapidly done by frozen to under 90 degree C in Liquid nitrogen.

 Fixation in Glutaraldehyde:

            In this BHV's are fixed in glutaraldehyde to reduce the immunogenicity. This fication may causes because of the cross-linking of the collagen, which masks the antigens leading to reduced antigen presentation and chemical stabilization. This may also leads to the membrane damage leading to the calcium flux.

Fixation Pressure:

            This fixation is done by BHV under an high pressure of 80mmHg. By which it crimp geometry of collagen and causes fragmentation, stiffening and kinks in the valve. Some of them prostheses are now fixed at physiological pressure of under 4mmHg in an effort of minimize.

Antimineralisation treatment:

            This treatmenty is done for the third generation valves with antimineralizing agents and reduce Cusp calcification. This treatment binds covalently to the bioprosthetic tissue and prevent calcium.

Design

            In this profile BHv supports stent is sewn to the aortic annulus. The height to the diameter ratio of thevalve is reduced from 0.7 to 0.41. the second generation BHV's have an flexible stent and redesigned cusps to cushion for the mechanical pressure. 

Stentless Value:

            In these values there is greater proximity and increased are of contact between xenograft and the host tissue. This leads to an calcification of the aortic wall attached to the stent valve, thereby causing aortic root stiffening, altered hemodynamics.

            These MHV's are more durable than BHV's, because their thromebogenic property and need for long term anticoglant therapy. The BHV failure is mainly may occur due to general factors specific toeach particular device. The pericardial valves are an excellent hemodynamics adbn good durability. They may fail due to the tissue generation, cusp tears and mineralization because of design related.

            The mechanical heart values have past 50 years of the witnesed remarkable process in the development of safe and favourable for the hemodynamically mechanical heart valves. Dr. John Gibbon had performed the first sucessfully closure of an intracardiac defect on May6, 1953 with heart lung machine.

            The time and print of the constraints permit the description of only approximately one third of the mechanical valves. This describes the valve design and materials, production dates and approximate implant volumes for each and every valve. They are some of valves such as caged ball valves, this is mainly used or led to the animal implants with a ball valve similar to that depicated. In this the methacrylate ball could be inserted in the descending thoracic aorta during a brief cross clamp period because of the ingenioyus fixation rings.

Harken Soroff ball valve concered that the ball could impinge on the aortic wall and therefore he designed his valve with a second outer concentric cage. Even though the silicone balls in these early Harken valves did not have the benefit of the "heat curing process" that would be developed in the mid 1960s.

Starr-Edwards Ball value had a new idea for a new heart valve to a young cardiac surgeon at the university of oregon. The valve concept was a simple one a design based on an 1858 wine bottle stopper. The evolution of the starrEdwards ball values can be succinctlythe fou valves.

Debakery-Surgitool Ball value was developed by Dr. Michael De Bakery and harry Cromie of Surgitool and was introduced in 1967. The pyrolyte ball was intended to limit ball variance. Unfortunately the relatively hard ball and soft titanium cage led. Braunwald- cutter ball value had worked jointly with the cutter laboratories to develop a cloth covered caged ball valve. The struts were covered with a knit Dacron tubing and the inflow ring with an ultrathin polypropylene mesh fabric.