Commissurotomy of a stenotic mitral valve on the closed heart was the beginning of the cardiosurgery. It helped hundreds of thousands of patients. At present in mitral stenosis surgery with extracorporeal circulation is recommended. The idea to eliminate the stenosis of the mitral valve by the closed route was adopted in percutaneous transvenous commissurolysis. The author discusses the submitted paper the development of mitral stenosis surgery at the cardiosurgical department in Hradec Králové during 45 years since the first commissurotomy implemented in 1951 by academician Bedrna.