Development of extracorporeal oxygenator used in open-heart surgery. First successful open heart surgery in New York State.


SUNY Downstate Medical Center


Clarence Dennis, MD, MA, PhD, SUNY Downstate Medical Center, professor and chair of surgery, 1951-1972.


Dennis pioneered the heart-lung bypass machine and attempted the world’s first open heart operation supported by such a device in April, 1951, while at the University of Minnesota. Five months later, in September 1951, he transferred to SUNY Downstate Medical Center and continued his research on the technology and surgical techniques that would make surgical treatment of heart disease possible. The heart-lung machine was one of the most important medical technologies developed in the post-World War II era, making possible a vast expansion in the surgical treatment of heart disease. One of Dennis’s heart-lung machines is housed in the Smithsonian.


1950s. In 1951, while at the University of Minnesota, Dennis performed the first ever open heart surgery using the machine he invented; the surgery was unsuccessful. In 1955, he performed his first successful open-heart surgery using the machine at Downstate’s affiliate, Kings County Hospital Center.  The operation was the second successful open heart surgery to be performed in the United States and the first such operation in New York State.