Surgery. It is the cutting of the commissures - (the pathologically fused leaflets of the mitral valve as occurs in rheumatic heart disease) so that the leaflets are free to open and close normally.
Incision of valve. Commissurotomy of a cardiac valve is called a valvulotomy, and consists of making one or more incisions at the edges of the commissure formed between the two or three leaflets of the valves. This procedure is performed in order to relieve constrictions, which occurs in valvular stenosis, especially mitral valve stenosis.
Opening the valve. A heart valve commissurotomy is usually performed on a stenotic (tight) mitral valve. This involves open heart surgery and incision of fused mitral valve leaflets. The surgeon usually makes the incision along the same path that separated the leaflets in the past and tries to maintain the integrity of the structure preventing the development of a leaky valve.
Rheumatic heart dis. When one has had bouts of rheumatic fever, they may develop mitral stenosis: the scarring of the mitral leaflets, their attachments and supporting structures leading to heart failure. Commissurotomy is the surgical (open or closed) correction of this problem.