Coronary Heart Disease And Bypass Surgeries Biology Essay


Coronary heart disease is the finest cause of cardiovascular mortality worldwide and it is assumed with ≥4.5 million deaths occurring in the developing world (5). It is estimated that the coronary heart disease mortality rates will increase from 1990 to 2020, with approximately 82% of the value is credited to the developing world (2). Coronary heart disease, also known as coronary artery disease, is a state which plaque builds up at the wall of the coronary artery. The function of the coronary artery is to supply the heart muscles with oxygen-rich blood. Coronary heart disease is the result of atherosclerosis. As people become older, their blood vessels walls are naturally grow a bit stiffer and harder, the flexibility is reduced. Atherosclerosis (hardening of the arteries) happens when hardened masses composed of lipids, dead cells, fibrous tissues and platelets gather in the arteries. A plaque is then formed. With some time the plaque grows larger and it can block the blood flow through artery. The plaque may breaks off and migrates to the other sites by the artery. This small piece of circulating plaque is known as embolism. Embolism can cause severe result of oxygen-deprived tissue and tissue death by blocking blood flow at its destination. If embolism occurs at the coronary artery, then another plaque tends to build up and narrowed the artery and this is the cause of the coronary heart disease.

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Since the disease can cause death, what are the treatments that are available to treat and reduced the symptoms of this disease?

Diagram 1 : The condition of artery narrowed by plaque (269)



Coronary artery bypass surgery is a surgical procedure performed to upgrade or restore the blood supply to the heart, relieve angina and reduced the risk of death due to coronary heart disease. The goal of this surgery is to create a new path for blood flow when one or more of the coronary arteries become blocked. CABG involves removing of a healthy blood vessel from the other parts of the body, for instance, artery from the chest or vein from the leg, and grafting it onto the heart to circumvent the blocked artery. Annually, there are about 28, 000 CABG operations are performed in UK (7).

The procedure starts with the anesthetist injects the patient with induction agent to make the patient unconscious. Anesthetist secures the inserted endotracheal tube and the mechanical ventilation is started. The surgeon examined the heart after open the chest via a median sternotomy. The bypass grafts are harvested from other part of body. Heparin is given to the patient in order to prevent the blood from clotting once the harvesting is done. CABG can be performed in two ways (18). The surgeon will place the devices to stabilize the heart if the patient has to undergo the "off-pump" surgery. During "off-pump" surgery, the heart beats on its own. The other way is "on-pump" surgery, where the heart is stopped. A machine is used to substitute the heart and lung throughout the operation. One end of the graft is attached to the coronary artery beyond the blockage and the other end is tied to the aorta. Then, the stabilizing devices are removed. To reverse the effect of heparin, the patient is given protamine. The sternum is wired as the one before the operation is done and the incisions are sutured closed. After the operation, the patient is moved to the intensive care unit (ICU) for few days to monitor the progress after operation and recover before the patient can go home.

Diagram 2 : The alternative path for the blocked artery (570)


A 2008 medical paper published in The European Heart Journal detailed a 30-year follow-up study of 1,041 patients who underwent CABG between 1971 and 1980. The 10, 20, and 30-year survival rates were 77 percent, 40 percent, and 15 percent, respectively. "The overall average life expectancy was 17.6 years," reported the researchers.

"Coronary bypass operations are performed half a million times a year with an overall success rate of almost 98 percent"

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CABG considerably upgrades the symptoms of angina and quality of life. With CABG surgery, the result of the candidates for the surgery shows an excellent result. About 85% of the patients having remarkable lessen the symptoms, lower the risk for future heart attacks and a decrease chance of dying within 10 years after the surgery (9). The other benefit of CABG is the bypass can be done in several arteries blockages. It also provides benefits to the patients who have many blocked arteries, blockages in the left main artery or weakened heart muscles. In addition, CABG is a better choice for the patients who have other disease than coronary heart disease such as diabetes.

The most common problem that occur after the surgery include angina. About 4 out of 100 patients will experience severe angina shortly after the surgery (4). The successful rate of the surgery might be decreased if it is repeated (8). The anesthetist needs to use anesthetic to make the patient unconscious. This would be a problem that some patients are afraid about because they might feel sick due to the use of general anesthetic. Other than that, a permanent scar might leave at the part where the graft was taken. In some cases, the scar might fade but it would take time. Some problems arise when the surgery is taking place. The problems are the unexpected reactions to anesthetic, excessive bleeding or developing blood clot. Excessive bleeding can result in death. Another risk is the patient might expose to the infection at the breastbone or the sternum. This is a serious problem as another operation will be needed to stabilize the sternum together with antibiotic therapy. However risks can be reduced if the patients take all the medications as instructed.


Depression is a common thing for the patients who have CHD. It is the risk factor of coronary heart disease. The patients' family must help them in reducing the depression because the risk of having CHD decrease if depression can be controlled.

"Younger people may feel more pressure - especially younger men - in the workplace and may be more threatened by limitations imposed by their disease" ( Jipan Xie, the lead author of Circulation : Journal of the American Heart Association ) (22). Friends are important in helping and giving support to them in the workplace. Therefore, they won't have any difficulties to perform better in their career. Employers need to understand their condition and suitable accommodation should be provided for them.

Other than that, CHD patients have to control their diet. A person that has CHD should take less oily food and food that rich in fats. Diseases including CHD can cause a poor quality of life to the patients. The symptoms of CHD can affect a person's daily life. For example, CHD patients have a limited exercise capacity compared to a healthy person. If they had too much of exercises, they will experience angina or commonly known as chest pain.

Cost treatments for CHD depend on the treatments that are needed by the patients. For example, the cost for the CABG surgery is expensive. Only some patients can afford to pay the cost for the surgery. There are several aspects that affect the cost. The aspects include type of room you choose to stay in, type of anesthesia used, length of stay in hospital, surgery techniques and medications that the patients will be needed after the surgery (16). In Malaysia, the range cost of CABG is within US $6000 and US $7000 (17). As some patients might come from a moderate family, they would not be able to pay the high cost. Therefore, they have to collect some donation but it would take time. Some families have to borrow money from the relatives as that is maybe the only way for them to get money as the surgery has to be done as soon as possible if the patient is in a critical condition.



The progression of CHD can be slow down by dealing with the risk factors such as high blood pressure, high cholesterol levels, diet and weight. Some drugs are effective at decreasing these risk factors. Antiplatelet drugs are the common drugs that are chosen by the patients. The examples are aspirin and clopidogrel. Once the epithelial wall is damaged, the blood clot forms to heal the damage place. This can lead to CHD as it may burst. If the blood clot does not take place, the risk to have coronary heart disease might be reduced. Aspirin is a chemical substance that can decreases the opportunity of the blood clot to form (10). It works by inhibit platelet cyclooxygenase, a key enzyme in thromboxane A2 (TXA2) generation (10). By inhibiting cyclooxygenase, thromboxane A2 cannot trigger the activation of the platelet and therefore, blood clot can be slow down. In addition, some doctors do believe that patients who have more than one risk factor for this disease should take aspirin daily (11). Aspirin is taken as the symptoms started. The patients take aspirin by chewing it.

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Source: Gasparyan, A. Y. et al. J Am Coll Cardiol 2008;51:1829-1843

Diagram 3 : Mechanism of aspirin in preventing blood clot

The effect of aspirin in blood clotting can be modeled by a simple experiment (12). The effect of warm water on margarine reflects how the aspirin works. As mentioned above, aspirin prevent the activation of platelets, prevent them to stick and hence prevent the risk of CHD. Three straws (blood vessel) and warm coloured water (blood) are used. No blockage is inserted in straw A, in straw B, wool is inserted as blockage. In straw C, margarine is used to model the blood clot. For each straw, the flow of warm water through the straw is observed. The results are as below :






This straw modeled a healthy blood vessel without any blockage



This straw modeled a blood vessel which have a blockage in it, slowing the flow of deoxygenated blood


Slow at first, later become fast

This straw modeled the blood vessel which have blockage in it but then is treated by aspirin

Table 1 : How aspirin works


Balloon angioplasty, also known as percutaneous transluminal coronary angioplasty (PCTA) is a nonsurgical process. The process of inserting the balloon and the stent in the blockage artery takes about 1 to 2 hours to complete (13). A stent is inserted at the blockage, where it acts as a support to make sure that the artery is always opened. As the result, the blood flow can be restored. There are 2 aspects that should be taken care of before stenting can be done to the patient. Size of the artery should not be small and the artery is not blocked completely. The procedures are simple if compared to the coronary bypass grafting.

Diagram 4 : The steps of inserting stent into the artery to open the blockage

Process A shows that a guide wire is used to bring the stent and deflated balloon at the blocked coronary artery. Process B shows that the balloon is inflated. Then, the stent expand pushing the blockage area to become wider and bigger. Process C shows that the catheter and the balloon were removed leaving the stent. The blood flow increases as the stent helps to open the artery vessel.


The website gives information about diseases, conditions and treatments in a language that is easily understand by the general public. All the information in this website is produced by the National Library of Medicine. Therefore, any information given in the site should be reliable. This site also provides the latest treatments of the diseases. Medical videos and illustrations are very useful to help us understand a certain topic better. This useful information can be found in this site. The information in this site is updated daily. In addition, it is free to enter this site. Therefore, finding information by using this site can be done anytime at anywhere.

The website provides detail information about CHD including the symptoms, causes, treatments, preventions and every component has a brief explanation. There is a box containing patient instructions in this site. The box provides more specific explanation and definition about the risks, treatments and prevention steps on CHD. However, some information is too brief. Information given by this site should be correct as some similar facts and information from this source can be found in other sources.