What They Are and Why We Need Them
The human heart emblematizes one of our most important organs. It is about the size of a fist, sits slightly to the left of our chest and is the muscle that plays the central role in pumping blood through our body. This blood then transports oxygen and nutrients towards our body parts and additionally carries unwanted waste products such as carbon dioxide away from them.
A heart can possibly fail due to multiple reasons such as a diseased heart muscle, coronary heart disease or a severe infection of the heart. When someone’s heart fails, that person will be unable to survive for long without getting a replacement heart. The most optional replacement for someone’s heart would be in the form of a transplantation of a donor’s heart. However, there is a growing demand for donor hearts with a pretty constant rate of donations each year. In 2012 for example, there were 3400 patients on the waiting list for a donor heart among European Union countries, with only 2004 patients being able to receive a transplant that year.
A widely used solution to fight against this shortage of donor hearts is the usage of artificial hearts. An artificial heart is a prosthetic device that is implanted into the body in order to replace the original biological heart. These artificial hearts then enable patients to survive while they are awaiting a donor heart. Currently, nonetheless only two different artificial hearts exist that are approved by the Food and Drug Administration (FDA). These include the SynCardia Total Artificial Heart and the AbioCor Replacement Heart, with the most commonly used one being the SynCardia Total Artificial Heart, that is making up 96% of all implants.
How They Work
Artificial hearts are highly complicated machines, that are mainly made out of plastic. The most basic description of their functioning can be described by blood entering the artificial heart through the atrium, what is a blood receiving chamber. The blood is then pumped into the aorta, what is an artery connected to the body, or into the pulmonary artery, what is an artery connected to the lungs. An artery is basically a thin tube that carries oxygen-rich blood away from the heart.
An artificial heart is connected to a control console, that exists in two different designs, by a thin cable. One of them is basically a huge box on wheels, that is moving besides the patients during their hospital stay. The other one occurs in the form of a way smaller box, that can be worn on a belt or a vest and is powered by attached batteries. Only the second one of these two devices may possibly allow a hospital leave.
The two primary mechanisms of powering an artificial heart work through compressed air or electricity, where electricity is the more frequently used method due to its simplicity.
The most significant ascendancy of artificial hearts is assumably their capability to delay the need for a donor’s heart, that most likely is not instantly available. Also, due to their neutral characteristics, they nearly acquire a neglectable chance of getting rejected by the body.
On the other side however, artificial hearts are generally relatively heavy with a mass of about one kilogram. The average adult human heart weights in comparison only about 250 to 350 grams. Additionally, artificial hearts are very expensive with their price ranging from about $100,000 to about $250,000. This is especially true when considering that they are only a temporary solution and that the real donor heart will also have to be implanted later on. Another limiting factor of artificial hearts is their durability. They are usually able to reliable sustain life for up to 18 months with the patient who had an artificial heart for the longest being Pietro Zorzetto, having it implanted for nearly four years. Moreover, another of their central limiting factors is set by battery size and capacity. The batteries cannot be stored inside the artificial heart and have to be recharged constantly. Lastly, patients with artificial hearts have to take blood-thinning medicine in order to stop blood clots from forming, that could then consequently cause a stroke when moving towards the brain.
We have come fairly far in the development of artificial hearts, but there are still enormous improvements that can be made in order to achieve better usability. Currently, engineers are working on the development of small, long-lasting batteries that could be implanted inside the patient’s chest, alongside the actual artificial heart, and then recharged through the patient’s skin. Another task, that will need to be accomplished, is reducing the size of artificial hearts, so that they can be totally implanted inside the body without the need for external devices like batteries or control consoles. Furthermore, there is quite some research in the area of biologically superior materials going on, that then would be used to line the internal chambers of the artificial heart. The goal of these materials lies in the reduction of the tendency for blood to clot. This then would thereupon reduce the essence on relying on blood-thinning medicines.
The biggest future prospect is however far more complex than the other ones mentioned above. It lies in engineering stem cells that would be capable of replacing damaged heart muscle cells and therefore restore the heart muscle functions. If this could be achieved, there would be a drastic decrease in the necessity for artificial hearts and even actual heart transplants. Patients could simply receive some of these genetically engineered stem cells and their heart would recover without the need of any further treatment. At present this remains however still a far cry from becoming reality.
National Heart Foundation of Australia. (2010). Artificial hearts. Retrieved February 27, 2018, from Heart Foundation: https://www.heartfoundation.org.au/images/uploads/publications/Artifical-hearts-information-sheet.pdf
NHS informs. (2017, December 22). Understanding how your heart functions. Retrieved February 27, 2018, from NHS informs: https://www.nhsinform.scot/illnesses-and-conditions/heart-and-blood-vessels/about-the-heart/understanding-how-your-heart-functions
Pavlovic, M. (2015). Bioengineering A Conceptual Approach. Switzerland: Springer International Publishing Switzerland.
SynCardia Systems Inc. (2014, September 12). 7 Things About Artificial Hearts That You Should Know. Retrieved February 27, 2018, from PR Newswire: https://www.prnewswire.com/news-releases/7-things-about-artificial-hearts-that-you-should-know-274872501.html