Artificial Heart Valves Research Paper

Based on the anatomy of the heart, heart tissue, and the heart valves, certain material specifications need to be taken into consideration to ensure that artificial heart valves function like normal healthy heart valves. When one of the four heart valves can no longer function sufficiently it may need to be replaced with an artificial heart valve. There are two main types of artificial heart valves: mechanical, and biological. Mechanical heart valves can be grouped by their method of implantation; percutaneous (needle-puncture) or sternotomy/thoracotomy (surgery). Percutaneous implants include stent framed and not framed. Sternotomy/thoracotomy implants include the ball and cage, tilting disk, bi-leaflet, and tri-leaflet. Biological (tissue)

The xenografts used for heart valves could be pig heart valve or cow pericardium. These materials listed above have their shortcomings but they meet the crucial specifications required for a safe and functioning heart valve. It is crucial that any biomaterial used in heart valve prostheses must keep regurgitation at a minimum. Some valvular regurgitation is inevitable and natural, but it should be kept under 5 ml per beat. Another requirement of the biomaterials used is that the transvalvular pressure gradient is as small as is it can possibly be. This is because whenever a fluid flows through a restriction, in this case a valve, a pressure gradient arises over the restriction. The pressure gradient is due to the increased resistance to flow through the valve. The transvalvular pressure gradient of natural heart valves is low because there is little obstruction in the flow, typically less than 16 mmHg. A major specification of artificial heart valves used is that they are non thrombogenic or at least minimally thrombogenic. The endothelium lining of natural heart valves is normally non thrombogenic. It is important that whatever biomaterial is used is non thrombogenic because a thrombi can form and cause blood clots.