Thursday, February 14, 2008
ARTIFICAL HEART VALVE
Artificial heart valve
Heart valves are flaps of tissue within the heart. They open and close to allow blood to flow into the correct cardiac areas in the right direction. Blood is supposed to flow from one of the heart's four chambers to the next. Closing a valve prevents any blood from leaking back. When one of the heart's four valves becomes too diseased or damaged to function properly, blood does not reach the proper area in the right volume. The only effective treatment is valve replacement. Valve replacement was not possible until the advent of open-heart surgery in the 1950s. Researchers set out to design a valve that could be easily implanted, have a low rejection rate, would not promote clot formation, and enjoy long-term durability.
American surgeon Charles A. Hufuagel (1916-) inserted a tube-and-float device into a patient's descending aorta in 1952 to prevent aortic backflow. In 1960 Dwight Harken implanted an artificial cardiac aortic valve into a patient. Nina Braunwald replaced a mitral valve with an artificial one shortly after that.
The first completely successful artificial heart valve was designed and implanted in a human patient by surgeons Albert Starr (1926-) and M. L. Edwards in Portland, Oregon in 1961. Their device, the Starr-Edwards valve, is now a standard in the field. The valve is made of a combination of materials and includes a hollow metal ball, an alloy (metal composite) cage, and a Teflon base. Heart valve designers and manufacturers later took advantage of new technologies developed for the space program and included materials like Pyrolite carbon, a strong and durable new substance, in artificial heart valve designs.
There is always the danger of blood clot formation after a valve is implanted. Because of this, patients are required take anticoagulation medication for life. An alternative is to use a porcine (pig) aortic valve, which carries a much lower risk of clot formation. Using this valve does not require anticoagulation medication, but porcine valves do not last as long as mechanical heart valves.
Taken from Discoveries In Medicine
Heart valves are flaps of tissue within the heart. They open and close to allow blood to flow into the correct cardiac areas in the right direction. Blood is supposed to flow from one of the heart's four chambers to the next. Closing a valve prevents any blood from leaking back. When one of the heart's four valves becomes too diseased or damaged to function properly, blood does not reach the proper area in the right volume. The only effective treatment is valve replacement. Valve replacement was not possible until the advent of open-heart surgery in the 1950s. Researchers set out to design a valve that could be easily implanted, have a low rejection rate, would not promote clot formation, and enjoy long-term durability.
American surgeon Charles A. Hufuagel (1916-) inserted a tube-and-float device into a patient's descending aorta in 1952 to prevent aortic backflow. In 1960 Dwight Harken implanted an artificial cardiac aortic valve into a patient. Nina Braunwald replaced a mitral valve with an artificial one shortly after that.
The first completely successful artificial heart valve was designed and implanted in a human patient by surgeons Albert Starr (1926-) and M. L. Edwards in Portland, Oregon in 1961. Their device, the Starr-Edwards valve, is now a standard in the field. The valve is made of a combination of materials and includes a hollow metal ball, an alloy (metal composite) cage, and a Teflon base. Heart valve designers and manufacturers later took advantage of new technologies developed for the space program and included materials like Pyrolite carbon, a strong and durable new substance, in artificial heart valve designs.
There is always the danger of blood clot formation after a valve is implanted. Because of this, patients are required take anticoagulation medication for life. An alternative is to use a porcine (pig) aortic valve, which carries a much lower risk of clot formation. Using this valve does not require anticoagulation medication, but porcine valves do not last as long as mechanical heart valves.
Taken from Discoveries In Medicine
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