Abstract:
Heart valve problems affect more than 100 million people worldwide. According to statistics around 55% valvular diseases are treated by mechanical prosthesis. The first heart valve replaced model was caged-ball valve, more than 50 models of heart valves designed by different companies. Every design has different aspects like valve geometry, total leaflets, materials used for model manufacturing, coating techniques, and coating materials. Human heart consist of four chambers two atria and two ventricles and these chambers contain four valves mitral valve, tricuspid valve, aortic valve, and pulmonary valve. These heart valves control the blood flow and prevents the back flow of blood from one chamber to another. Congenital defect or any other abnormality of heart valves like stenosis or regurgitation causes severe problem in cardiovascular system and lead to death, so to avoid these problems surgeons repair or replace the heart valve by an artificial prosthesis valve. Depend on the patient need and condition, either replaced from biological or mechanical heart valve. Biological valves are made of living tissues whereas mechanical valves manufactured by the manmade materials or normally called biomaterials which are biocompatible and don’t causes any reaction inside the body when they become in direct contact with blood and living tissues.
Evolution of mechanical valve designs significantly consists of valve geometry and improvement in hemodynamics characteristics. Recently available design provides good hemocompatibility, reduced tissue ingrowth and less thrombotic effect as compare to previous designs. Although due to high shear and stress in blood flow causes blood cells damage and clot formation which will leads to failure of prosthesis. Mechanical Heart valves are manufactured by biomaterials like graphite, pyrolytic carbon (PyC) PTFE, PET, titanium and thus these prosthesis present satisfactory strength, durability and longer lifespan in the body. To improve the wear resistance and strength of graphite these valves further coated with pyrolytic carbon by Chemical Vapor deposition (CVD). CVD is a lengthy process in this process thin layer of pyrolytic carbon deposited by the thermal reaction of gaseous mixture. After Coating samples characacterization have been done to validate coatings.
