from march 1977 to january 1981 , at the `` '' de gasperis '' '' cardiosurgery center , this prosthesis has been implanted in 644 patients : 283 for mitral valve replacement , 240 for aortic valve replacement , and 121 for the replacement of both mitral and aortic valves .
C0003506
r aortic valve replaceme
C0003501
aortic valv