Artificial heart valve 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. Natural heart valves are evolved to forms that perform the functional requirement of inducing unidirectional blood flow through the valve structure from one chamber of the heart to another. Natural heart valves become dysfunctional for a variety of pathological causes. Some
MD Helicopters MD 600 MD Helicopters MD 600 The MD Helicopters MD 600N is a light utility civilian helicopter designed in the United States. It is a stretched eight-seat development of the five-seat MD 520N helicopter. McDonnell Douglas Helicopter Systems (MD Helicopters since 1999) first announced it was developing a stretched MD 520N in late 1994, at that time designated the MD 630N. The prototype, a modified MD 530F, had made its first flight on November 22, 1994. McDonnell Douglas gave the go-ahead for the production aircraft, redesignated the MD 600N, in March 1995. McDonnell Douglas stretched the MD 520N fuselage by inserting a