When Christiaan Barnard performed the first heart transplant in 1967, it was initially seen as remarkable scientific achievement, but overtime both the medical community and the general public were forced to re-evaluate heart transplants. The medical community quickly realized that the first transplants were little more than dangerous and unpredictable experiments. These operations were almost uniformly unsuccessful. They failed because the surgical procedure was extremely complex, the patients were prone to develop life threatening infections and organ rejection was incredibly common. Ultimately, heart transplants raised deep medical, ethical and even religious concerns that the medical community was forced to address.
In the early 1950s, doctors in the United States and the Soviet Union began experimenting with heart transplants in animals. These surgeries were uniformly unsuccessful. Physicians were forced to induce hypothermia in their test subjects to prevent permanent brain damage, but many of these subjects died because it took too long to connect the heart to the cardiovascular system. The few subjects that survived typically only lived a few hours.
The creation of the oxygenator pump (the heart lung machine) in 1953 by John H. Gibson finally gave surgeons enough time to complete the transplant without killing their patient. The oxygenator pump temporarily bypasses the heart and lungs by both exposing the blood to oxygen and pumping it through the body. Instead of inducing hypothermia, the surgeon could use the oxygenator pump to keep the patient alive and safely work much more slowly. This device dramatically improved the chances that a heart transplant could succeed.