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Introduction
Many advances in the approaches used in the treatment of illnesses affecting the circulatory system have been achieved in the last few decades. They include cardiac transplants from donors, lifestyles changes, bypass, and artificial heart transplants. Bells and Rhoades (2008, p. 209) describe the circulatory system as a fluid transport system for the movement of blood throughout the body . The circulatory system has the following components: the heart which acts as the pump, the arteries that distribute blood to the organs, the capillaries that supply and drain the tissues, the veins that drain the organs, and the blood which acts as the transport medium (Bells et al, p. 209). Systemic and the pulmonary circulation system are the two routes of circulation mostly utilized by the body. Pulmonary circulation supplies oxygen to the lungs while systemic circulation targets the rest of the body organs and extremities. The essay will review the developments in artificial hearts in the last 20 years and the impacts of heart failure on the physiology of the circulatory system and the body as a whole.
Review of the status and advancements of artificial hearts in the last 20 years
According to the Institute of Medicine (US) Committee to Evaluate the Artificial Heart Program of the National Lung and Heart (1991, p.1), heart disease was responsible for almost half of the 700,000 deaths recorded in the country. The main causes of heart failure also called end-stage heart diseases are congenital, high blood pressure, viral cardiomyopathy, and coronary atherosclerosis. The program was initiated in 1964 with the main mandate of developing mechanical circulatory support systems (MCSS) which included ventricular assist devices (VAD) and total artificial hearts (TAH). These systems were for both temporary and long-term use. A VAD is a device that is designed to help the failing heart but does not replace it. Most of the 1990 models of VAD were put into the abdomen and then connected to tubes that allow blood flow from the heart to the other parts of the body. An artificial heart is a prosthetic device that is implanted into the body to replace the whole heart and works in the same way as the VAD.
Denton Clooney has implanted the first mechanical device in 1969 in a hospital in Texas. Although the first patient died after 32 hours, the success of the implantation encouraged doctors to carry more research on cardiac physiology. In 1982, the first artificial heart, the Jarvik 7, was implanted to replace the heart completely in a patient called Bailey Clark. This fete was achieved by William Devries in Utah. In 1982, a second TAH implantation was done in the post-cardiotomy patient. This was to act as a temporary measure as the patient waited for transplantation. The patient succumbed to death eight days later. The death was due to sepsis and failure in multiple organs. In the same year, several patients had TAH implantations owing to various life-threatening cases of heart failure. The five patients had a survival range of four months to 20 months before they developed complications. This necessitated the refining of the devices before they could be used again. Three years later an improved pneumatic TAH was invented at the University of Arizona and was later tested for its applicability as abridge to transplantation (Institute of Medicine (U.S.). Committee, 1991, p. 2)
In 1992, an international audit of all TAH implantation was done with an aim of assessing its success and viability. Between the years 1969 and 1991, a total of 11 models of TAH were in use. These models were connected to monitoring devices to assess the progression of the conditions and also their safety. A total of 221 patients were to undergo these procedures in partly 39 centers dispersed in North America and Europe. 32 percent of the 207 patients, 13 from Eastern Europe were disqualified, died while the device was implanted on their bodies. The results showed dismal performance for most of the devices. The symbolic Jarvik device was found to have the best performance rate. This in turn led to more investigation and testing on the Symbolic Jarvik which had its name changed to pneumatic Cardio West TAH. Surgeons used this device on a total of 114 patients worldwide with the sole intention of improving it as a bridge to transplantation. The investigation was led by surgeons from the renowned University of Arizona where patients benefiting from this program received a complete analysis of their progress. The 24 patients in Arizona had an average duration spent on the device as 53 days. Nineteen of these patients, (83%) had successful transplantations and were alive in 1999 (Expert Panel Review of The NHLB Total Artificial Heart (TAH) Program, 1999, p. 9). The number of complication cases due to bleeding, sepsis, and neurological events after transplantation have greatly reduced over the years. This evidence proved that the possibility of the application of TAH as a successful transplantation device was imminent and achievable in a few years (p. 10).
In 2000, the Abiocor was developed by Abiomed Inc with the support of the national heart, lung, and blood institute. This was designed to save the lives of the patients suffering from heart failure and was ineligible for receiving natural transplants. Other preconditions were a life expectancy of fewer than 30 days and the unavailability of other options for treatment. The Abiocor is a device intended to perform the functions of the normal heart by ensuring the effective circulation of blood in the body. This was a major milestone when the first transplant was done on July 2, 2001, at a Jewish hospital in Kentucky. Several other implants have been done successfully in different hospitals all over the United States. However, the implant only received approval from the FDA in 2006 thus necessitating the first approved implant on June 24, 2009 (Food and Drug Administration, n.d).
In 2004, another artificial implant was approved by the Food and Drug Administration (FDA). The Syncardia temporary Cardio West total artificial heart (TAT-t) was approved on 15th October 2004. This was after 10 years of rigorous clinical investigation and testing. Its commonly used on patients suffering from failing hearts and is experiencing irreversible damage in their ventricles. Patients waiting for donor hearts and those facing high risk to succumb can also receive this type of TAH (Copeland, smith, Arabia, smitten, Nolan, Sethi & Slepian, 2004, p.9). It aims to enhance circulation in the body and ensure liver and kidney functioning are not impaired. However, this implant is contraindicated for patients who do not qualify for a donor heart and those who have partially impaired hearts.
These advances on artificial hearts have taken 60 years since the first attempt to make an artificial pump was made by William Sewell. Since then, many inventions occurred with the climax coming in the last decade with the invention of total artificial hearts that can sustain life in patients. It is expected that by the year 2011, a fully implantable artificial heart will have been invented( Mudd & Kass, 2008) However, it may only come into use in the year 2013 due to the fact that it has to undergo a rigorous clinical trial before it is approved. This is according to research being carried by two consortiums; one led by Professor Alan Carpenter, a French cardiac specialist, and another by US surgeons (FDA, n.d, p.5).
Impacts of heart failure on the circulatory system and the body as a whole
There are major impacts to the organs and the body as a whole that are brought by the failure of the heart. Heart failure may occur when the ventricles and the dysfunction of the valve are due to various pathological factors. A failing heart can only pump blood under very minimal pressure thus impacting negatively on the other body organs. The heart is important due to the fact that blood, which it pumps, is the transport medium of oxygen, food substances, metabolites, and hormones. A decrease in pressure in the circulatory translates into a decline of the processes associated with the hormones. Lack of hormones, where they are needed at the right time, leads to derailment in normal physiologic processes such as digestion, biochemical metabolism, homeostasis, and other processes. Failure for proper digestion leads to the body lacking enough food to produce energy to propel normal processes such as walking, breathing, and even thinking. Biochemical pathways are greatly affected meaning that energy requirements are not met due to inadequacy in the conversion of adenosine diphosphate to adenosine triphosphate which is the form of energy utilized to sustain the normal cellular processes (Paul, chap. 10).
Another important function that will be impaired is homeostasis performed by the kidney. The kidney will not be able to reabsorb vital nutrients and water in its tubes owing to the low blood pressure. This will lead to uncontrolled loss of water and micronutrients thus destabilizing the whole body. This occasion the beginning of complications such as kidney and liver failure. The impairment of these organs and the subsequent inability of the body to remove metabolic wastes from the body lead to toxicity in the blood system and set the danger of the patient dying due to organ failure. Although the lung is close to the heart than any other organ, it suffers the biggest owing to its active role in respiration. Most of the oxygen taken in is not absorbed while the carbon dioxide is not taken out leads to panting that is characterized by fast breathing. This scenario can lead to lung collapse due to increased activity without commensurate energy compensation.
A failing heart also means that blood does not reach the trunk and the extremities. Atherosclerosis accelerates the normal hardening of arteries in the body in a process referred to as arteriosclerosis. In this process, lipid materials are usually deposited on the walls of the arteries especially when the blood pressure is too low. This causes vasoconstriction due to the narrowing of the blood vessels while at the same time increasing pressures in the veins. Persistent deposition may lead to clot formation when the platelets accumulate around the affected walls. The clot which is medically called a thrombus may be dislodged and transported to thinner vessels where it causes a blockage hence disrupting blood flow. This disruption in the blood flow is known as infarction and is responsible for causing strokes and some forms of myocardial infarctions (Paulev, 2000, chap. 10). The organs that are cut off from the blood flow develop gangrene that is characterized by the decay of the tissues. This can only be corrected through amputation of the affected limb or removal of internal organs (Paulev, chap 12).
Conclusion
The artificial hearts offered a lifeline for patients waiting for transplants from potential donors. The negative impacts caused by heart failure and the subsequent complications in the transplantation process are the main drivers of these inventions The desire to improve these total artificial hearts saw many investments in the investigation and clinical testing of the devices. the investigations yielded fruits resulting in more improved and safe devices being invented in the last 20 years. The duration the devices can sustain life has also increased dramatically from less than 48 hours to a few years. The invention of a permanent TAH will be the climax of the investigation thus reducing the demand for donors hearts. This will provide relief to the thousands of people who are suffering from cardiac-related disorders worldwide. However, more efforts should be made to enlighten the people on the prevention measures because most of these conditions are caused by modern lifestyles.
References
Copeland J., Smith, R., Arabia F., Nolan P., Sethi G. and Slepian, M. (2004). Cardiac Replacement with a Total Artificial Heart as a Bridge to Transplantation. New England Journal of Medicine, 351:859-67. Web.
Expert Panel. (1999). Review of the NHLBI Total Artificial Heart (TAH) Washington D.C.: National Academy Press. Web.
Food and Drug Administration. (2009). Medical Devices. Web.
Institute of Medicine (U.S.) Committee to Evaluate the Artificial Heart Program of the National Lung and Heart. (1991). The Artificial Heart: Prototypes, Policies, and Patients. Washington D.C.: National Academy Press.
Mudd, J and Kass, D. (2008). Review Article Tackling heart failure in the twenty-first Century. Nature of international weekly journal of science. Vol. 451, 919-928.
Paulev, E. (2000). Medical Physiology and Pathophysiology: Essentials and clinical Problems. Copenhagen: Copenhagen Medical Publishers.
Rhoades, R. and Bell, R. 2008. Medical physiology: Principles for Clinical Medicine. Baltimore; Lippincott Williams and Wilkins.
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