What is Heart Perfusion?

Having any sort of major cardiac surgery, such as coronary artery bypass surgery, a heart valve repair operation, a heart transplant or surgery to repair damaged major blood vessels such as the aorta creates a real challenge for medicine. If the heart is being operated on directly, it can no longer push blood around the body to keep the other tissues and organs supplied with oxygen. If the brain does not get fresh blood, irreversible brain damage tends to occur from about four minutes.

The First Open Heart Operation

Today we think of a heart bypass operation as a serious procedure but one that is done as a standard operation in hospitals in the developed world. It is only since the 1950s that we have had the technology to do this though. If you were born with a congenital heart defect or had a serious valve problem in the 1940s, there was little that could be done to help you. The device that has made open heart surgery possible is the heart and lung machine. This basically takes over all of the functions of the heart and lungs during surgery and perfuses the tissues and organs of the body with fresh blood. The highly skilled medical professional that controls the heart and lung machine is called a perfusionist.

The first perfusionist was Clarence Dennis, a surgeon in the US who carried out the first open heart surgery with a heart lung machine in April 1951. Unfortunately, this was not successful, not because of the heart and lung machine, but because the patient had a heart defect that was too complicated to correct. The first surgery using an external perfusion system was a heart repair on a woman of 18, also in the US, two years later.

Heart Perfusion in Action

The heart and lung machine is a highly complex piece of technology that takes incredible skill to operate, It has two main sections; an oxygenator that supplies the blood running through it with oxygen and a pump that drives the blood back through the tissues and organs of the body. The heart and lung machine is connected directly to the arteries and veins of the patient undergoing surgery and their blood supply is taken over by the machine.

There is some delay in the changeover between the real heart and the heart and lung machine so, to avoid any chance of brain damage, the patients body is cooled to well below normal body temperature. This enables a slower blood flow to be used without any ill effects afterwards.

The Heart Perfusionist

In the early days of heart perfusion, the heart and lung machines were much simpler than they are now and they were operated by a technician who could have been a porter or other hospital technician. As the system has developed, it is now operated by a doctor, often a surgeon who undergoes two years of intensive training in perfusion. Very few colleges offer the course as the number of perfusionists required is fairly limited; one of the best ones is at Nescot College in the UK.

How Long can a Heart Lung Machine be used?

The techniques involved in heart perfusion have developed enormously since the 1950s but this procedure still carries risks, many serious. There have been suggestions that people who have perfusion are more likely to suffer problems with attention span, memory and other neurological functions. The time that a heart and lung machine is used is therefore limited to the few hours that the operation on the heart takes. One patient has survived on a heart and lung machine for 16 days, before getting a suitable donor for a heart transplant, but this is exceptional.