Artificial heart valve was later changed to use silicone-coated material. The first implantation of mechanical heart valve to human was performed by Dr. Hufnagel on 11 September 1952, using the valve that he developed. This event accelerated the development of other artificial heart valves. Artificial heart valve An artificial heart valve is a device implanted in the heart of a patient with valvular heart disease. When one of the four heart valves malfunctions, the medical choice may be to replace the natural valve with an artificial valve. This requires open-heart surgery. Valves are integral to the normal physiological functioning of the human heart.
MD Helicopters MD 500 in 1953. Images and analyses done regarding North Korea's MD 500 helicopters show that they have been modified significantly to serve as light attack helicopters, such as modification work on the helicopters for them to be mounted with Soviet-designed AT-3 Sagger anti-tank wire-guided missiles. The MD 500 is widely operated by private individuals, companies and law enforcement agencies around the world. MD Helicopters MD 500 The MD Helicopters MD 500 series is an American family of light utility civilian and military helicopters. The MD 500 was developed from the Hughes 500, a civilian version of the US Army's OH-6A Cayuse/Loach.