Surgery on the great vessels (e.g., aortic coarctation repair, Blalock-Thomas-Taussig shunt creation, closure of patent ductus arteriosus) became common after the turn of the century. However, operations on the heart valves were unknown until, in 1925, Henry Souttar operated successfully on a young woman with mitral valve stenosis. He made an opening in the appendage of the left atrium and inserted a finger in order to palpate and explore the damaged mitral valve.