The Heart-Lung Machine

For patients whose hearts are in disrepair, cardiac surgery of some form may be the only effective means of correcting the situation. Until the 20th century, successful heart surgery was unthinkable because it was not possible to see inside a heart that was beating and filled with blood. Because of research on dogs and other animals, the 1950's saw an exciting blossoming of advances in cardiac surgery which continues to this day

After decades of work, in 1953 a heart-lung machine was developed that was able to take over temporarily for the heart and lungs. Blood can be re-routed through this machine, bypassing the heart so that surgeons can work inside it. Blood enters the machine from veins that empty into the heart. This blood is returning from its circuit of the body, having given up its oxygen for carbon dioxide. Normally, the heart would pump it to the lungs, where carbon dioxide would be exchanged for fresh oxygen. The heart-lung machine performs this same exchange in an oxygenator. When it has finished this "artificial breathing," it pumps the blood back into the body through an artery. Since its development almost forty years ago, thousands of human and animal hearts have been repaired while this life-saving machine took over for them during surgery.

The Cardiac Pacemaker

When disease or injury impairs the heart's pacemaker, the heartbeat is disrupted, causing dizziness and sometimes even convulsions or death. A heart can stop beating altogether if the pacemaker fails. Pacemakers are one of the best-known devices for helping this type of an ailing heart. The first pacemaker was a large cart about the size of a wheelbarrow. A smaller pacemaker was developed in the early 1950's in Boston and was worn externally in a shirt pocket. The prevalence of infection as a result of this design required that an implantable pacemaker be developed. Today, programmable pacemakers that last years before needing to be upgraded are used on both humans and animals.

The heart valves are like tiny trap doors that connect the different parts of the heart. They are made of flaps of tissue that fit closely together. The valves keep the blood moving in one direction and regulate its flow. In the 1950's, Dr. Michael DeBakey developed artificial veins and arteries, which he perfected and tested in dogs. Artificial heart valves, made from Dacron and other synthetic materials, or pig valves, are now in frequent use to repair defective valves.