Clarence Dennis

Clarence Dennis (June 16, 1909 – July 11, 2005) was an American cardiothoracic surgeon renowned for his pioneering work on cardiopulmonary bypass (CPB). Born in St. Paul, Minnesota, to a surgeon father, he earned his MD at Johns Hopkins in 1935 and completed his surgical residency at the University of Minnesota. By 1940, he had obtained an MS in physiology and a PhD in surgery, becoming a full professor there.

Dennis began developing his heart-lung pump-oxygenator in 1946 and later collaborated with John Heysham Gibbon, who refined CPB. In 1951, Dennis led a team in the first human CPB operation on a six-year-old girl with a congenital heart defect, but the procedure was unsuccessful due to an unrepairable defect and technician error. After no further successful cases at the University of Minnesota, he moved to SUNY Downstate Medical Center in New York, where his team achieved their first successful CPB operation in 1955.

Dennis became a prominent figure in cardiovascular surgery, using CPB for patients with cardiac shock post-myocardial infarction. He joined NIH in 1972 and later SUNY Stony Brook until retirement in 1988. Returning to St. Paul, he directed the University of Minnesota's Cancer Detection Center, founded by Owen Harding Wangensteen, who initially tasked him with creating a pump-oxygenator in the 1930s. Dennis retired at 86 due to macular degeneration and advanced age, feeling unable to continue his scientific work. He passed away on July 11, 2005, in St. Paul from dementia complications.