Dennis, Clarence, 1909-2005

Dr. Clarence Dennis, pioneering heart surgeon and developer of a heart-lung bypass machine, was born to Dr. Wayne and Clara Dennis of St. Paul, Minnesota on June 16, 1909. A health condition prevented Dennis from serving in the military during World War II, so he remained at the University of Minnesota in a variety of instructional and professorial positions in the Department of Surgery. Under the tutelage of the chairman, Dr. Owen H. Wangensteen, Dennis developed an interest in cardiac surgery, particularly the idea of a mechanism to bypass some cardio-pulmonary functions. In 1946 Dennis visited Dr. John H. Gibbon at Jefferson Medical School in Philadelphia; Gibbon had been working on a pump-oxygenator since 1934. The two surgeons traded ideas over the next few years as Dennis began working on similar technology with funding from the National Institutes of Health (NIH). Over the next few years Dennis constructed various apparatuses to provide a suitable substitute for the heart and lungs. Inspired by the success of artificial kidneys, he developed a similar machine; however, it failed to provide enough oxygenation of the blood during bypass. By 1951, Dennis and his staff had developed a pump-oxygenator which led to successful operations on nearly two dozen dogs; this success gave Dennis the confidence to try his machine on a human subject. On April 5, 1951 Dennis, Dr. Richard Varco, and the University of Minnesota Hospital surgical staff performed the world's first open-heart surgery. The machine performed satisfactorily, but the young patient's heart defect proved to be much more severe than originally diagnosed, resulting in her death. In 1972 Dennis took over as Director of the Artificial Heart Program at the National Heart and Lung Institute (NHLI) at NIH. His main task was to study the feasibility of long-term usage of the artificial heart, resulting in a position paper for NIH. He argued in his paper that a lack of adequate staff numbers and expertise, coupled with advances in heart transplantation, would severely hamper the successful implementation of an artificial heart program.

Dr. Clarence Dennis, pioneering heart surgeon and developer of a heart-lung bypass machine, was born to Dr. Warren and Clara Dennis of St. Paul, Minnesota on June 16, 1909. After graduating from St. Paul's Central High School in 1927, Dennis attended Harvard College and earned his bachelor's degree in 1931. Dennis then pursued his medical degree at Johns Hopkins Medical School from 1931 to 1935 before returning to his home state for his surgical residency with Owen Wangensteen at the University of Minnesota at Minneapolis. Wangensteen required residents to earn additional degres, thus Dennis earned his master of science degree in 1938 and his Ph.D. two years later.

A health condition prevented Dennis from serving in the military during World War II, so he remained at the University of Minnesota in a variety of instructional and professorial positions in the Department of Surgery. Under the tutelage of the chairman, Dr. Owen H. Wangensteen, Dennis developed an interest in cardiac surgery, particularly the idea of a mechanism to bypass some cardio-pulmonary functions. In 1946 Dennis visited Dr. John H. Gibbon at Jefferson Medical School in Philadelphia; Gibbon had been working on a pump-oxygenator since 1934. The two surgeons traded ideas over the next few years as Dennis began working on similar technology with funding from the National Institutes of Health (NIH). In fact, Dennis received continual NIH funding from July 1947 until his departure from academic medicine in 1972.

Over the next few years Dennis constructed various apparatuses to provide a suitable substitute for the heart and lungs. Inspired by the success of artificial kidneys, he developed a similar machine; however, it failed to provide enough oxygenation of the blood during bypass. By 1951, Dennis and his staff had developed a pump-oxygenator which led to successful operations on nearly two dozen dogs; this success gave Dennis the confidence to try his machine on a human subject.

On April 5, 1951 Dennis, Dr. Richard Varco, and the University of Minnesota Hospital surgical staff performed the world's first open-heart surgery. The machine performed satisfactorily, but the young patient's heart defect proved to be much more severe than originally diagnosed, resulting in her death. Undaunted, Dennis and the staff tried again a few weeks later, but a technician's error led to the patient's death. However, Dennis's machine achieved its purpose, and work continued on the apparatus even after Dennis moved from Minnesota to assume the chair of the newly-created Department of Surgery at Downstate Medical Center, State University of New York (SUNY).

Spurred on by Dennis's work, Gibbon continued to pursue his own mechanism and performed the world's first successful open-heart surgery in 1953. Dennis's first successful surgery occurred two years later on June 30, 1955. He continued working to perfect his pump-oxygenator at SUNY for another fifteen years, even as the use of the device fell out of favor with heart surgeons as other apparatuses emerged.

In 1972 Dennis took over as Director of the Artificial Heart Program at the National Heart and Lung Institute (NHLI) at NIH. His main task was to study the feasibility of long-term usage of the artificial heart, resulting in a position paper for NIH. He argued in his paper that a lack of adequate staff numbers and expertise, coupled with advances in heart transplantation, would severely hamper the successful implementation of an artificial heart program. Ultimately Dennis concluded that the program was failing to utilize his expertise, so after three years Dennis left NIH for another position in the SUNY system, this time at Stony Brook.

For the next fourteen years Dennis worked at both Stony Brook and the Veterans Administration hospital at Northport. Returning to his medical roots, he conducted studies at the VA hospital on wounds and vagotomies while teaching surgical techniques at SUNY. After a long career as an educator and surgeon, Dennis retired in 1989 to his home state of Minnesota.

The retirement was short-lived, however, as he took a position as Director of the Cancer Detection Center at the University of Minnesota in 1991. There he led the program's efforts to encourage early cancer detection through regular testing and check-ups. Budgetary issues caused the termination of the program in 1996, and Dennis retired for the second and final time.

In addition to his career as a surgeon and educator, Dennis also served as an advocate for medical research, particularly during the anti-vivisection movement of the 1960s and 1970s. Because of his ground-breaking canine and human open heart surgeries Dennis was considered an expert on the necessity of animal testing for medical advancement. As president of the National Society for Medical Research (NSMR), he authored several articles and testified before Congress on the necessity of animal testing in ensuring the success of medical procedures on humans. In addition to the NSMR, Dennis was active in the American College of Surgeons, the Association for the Advancement of Medical Instruments, and the International Surgical Group.