U.S. surgeon and educator chiefly noted for heart-transplant operations. He was also the first to implant an artificial heart in a human. In April 1969 Cooley observed that the heart of a 47-year-old patient would not function adequately after he removed a section of diseased heart muscle. He implanted a mechanical heart made of silicone, which served as a substitute organ for 65 hours until a heart from a human donor was inserted to replace it. Nevertheless, the patient died 38 hours after the second operation because of pneumonia and kidney failure.

Cooley received an M.D. degree from Johns Hopkins University, Baltimore (1944), and joined the medical faculty of Baylor University College of Medicine, Houston, in 1954. In 1969 he left Baylor to found the Texas Heart Institute, of which he became president and surgeon in chief, and from 1975 he served also as professor of clinical surgery at the University of Texas Medical School in Houston. In 1998 Cooley received the National Medal of Technology, the highest honour for technological innovation.