"Brock performed the first successful valvotomies for isolated pulmonary stenosis in 1948. He gained access to the blood-filled beating heart through a small incision in the right ventricle through which he passed a valvulotome that was used to enlarge the opening of the stenotic value" (W. Bruce Fye). See Brock's book, The anatomy of congenital pulmonary stenosis, London, 1957.