Complex sentence: By 1946, Smithy had devised a valvulotome to cut away scar tissue from the aortic valve and had made a presentation on the subject at an American College of Surgeons (ACS) forum.
Split into simpler sentences: By 1946, Smithy had devised what he called a valvulotome, which he used to cut away scar tissue from the aortic valve. He made a presentation on the subject at an American College of Surgeons (ACS) forum.