Factors that affect the Development of Coronary Heart Disease

In today’s society, peoples understanding of medical issues are vastly increasing. Treatments, cures and vaccines for various diseases and disorders are being developed constantly, and yet, “coronary heart disease remains the number one killer in the world, it kills 260,000 people a year”(1) Therefore it is my aim throughout this essay to identify and expand on the factors that affect the development of coronary heart disease (CHD).

“Coronary Heart Disease involves atherosclerosis of the coronary arteries.” (2) Atherosclerosis is the result of an atheroma forming in an artery or the hardening of the arteries. This involves the deposition of atherosclerotic plaques, which narrow the diameter of the artery. These plaques are usually collections of connection tissue, fats and smooth muscle cells. The plaque project into the lumen, the passageway of the artery, and interfere with the flow of blood. (see figure one). In conjunction with the reduction of blood flow, blood clots are more likely to form as the lumen progressively becomes narrower. It is the heart cells themselves that are reliant upon the oxygen and nutrients that a sufficient blood flow provides therefore without such a blood flow they are unable to function properly. Consequently a myocardial infraction (heart attack) can occur as a result of the arteries becoming blocked and the absence of a sufficient blood supply.

Figure 1 - The development of an atheroma forming (3)

The factors that affect the development of CHD can be classified into both modifiable and non-modifiable factors. However all risk factors do more than just add to one another. There is a virtual multiplication effect in victims with more than one risk factor. The table below highlights that the more risks a person has, the higher their chance is of developing CHD.

Figure 2 (4)

The modifiable risk factors of CHD are “smoking, raised cholesterol levels from the diet, physical inactivity, high blood pressure and stress.” (5) By studying each of these in turn, a better understanding of how these factors effect the development of CHD can be obtained.

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Smoking is strongly related to the high risk of CHD. Cigarette smoke that enters the lungs and is ultimately absorbed into the blood stream, contains; “carbon monoxide, radioactive polonium, nicotine, arsenious oxide, benzopyrene, and levels of radon and molybdenum that are twenty times the allowable limit for ambient adrenaline.” (6) “The increase in adrenaline and noradrenalin increases blood pressure and heart rate by about 10% for an hour, per cigarette.” (7) In simpler words, nicotine causes the heart to beat more vigorously. It causes vasoconstriction, which in turn increases blood pressure. Carbon monoxide, on the other hand, reduces the red blood cells ability to carry oxygen to the body cells in haemoglobin.(a group of globular proteins that act as oxygen carriers in blood) It poisons the normal transport systems of cell membranes lining the coronary arteries. This protective lining breaks down, exposing the undersurface to the ravages of the passing blood, with all its clotting factors as well as cholesterol.

All these chemicals however cause blood platelets to become ‘stickier’ and this increases the chance of blood clots forming (see figure three). Quitting smoking will help in reducing the risk of CHD, but the risk will never be as low as a non-smoker (a person that has never smoked)

Figure 3 - Chemicals in smoking causing blood platelets to become stickier. (8)

The next factor to be studied, cholesterol, has become one of the most important medical issues in the last decade. “Reducing cholesterol intake can directly decrease one’s risk of developing heart disease, and people today are more conscious of what they eat.”(9) Cholesterol ultimately causes atherosclerosis therefore a cholesterol-rich diet increases the risk of an atheroma forming. The reason for this is that “cholesterol is a type of lipid which unites with proteins in the blood to form lipoproteins.” (10) There are two types of lipoprotein, low-density lipoproteins (LDL) that increase the risk of developing atheromas and high-density lipoproteins (HDL), which do not contribute to atheromas. Instead they can decrease the dangers LDL cholesterol has upon a person’s health. “Eating a cholesterol-rich diet will increase the amount of LDL in the blood” (11) especially if the diet consists of animal and dairy fats. Physical activity however increases the amount of HDL, which helps to reduce the dangers of LDL. Furthermore the risk of high blood pressure and obesity, which both contribute to the development of CHD, is also decreased with regular exercise. In addition the risk of CHD is further increased if a person is clinically obese. This is due to the fact that an atheroma is more likely to form in the coronary arteries due to the high amount of cholesterol present. This will eventually lead to atherosclerosis.

High blood pressure is the next risk factor to be studied and it increases the risk of CHD in many ways. High blood pressure simply means the heart has to ‘work harder’ to pump the blood around the body. This is done by “an increase in cardiac output and by contraction of the muscle in the middle layer of the arteries” (12). A condition called hypertension is then seen to occur when blood pressure remains at a high level and it is this condition that can greatly increase the risk of CHD. This is because arteries respond to high blood pressure by making their muscular layers become thicker, narrowing the lumen, and increasing blood pressure by a further extent. The continuously increasing blood pressure compresses the tiny vessels that feed the artery wall, causing structural changes in these tiny arteries. Microscopic fracture lines then begin to propagate through the arterial wall. The cells lining the arteries are compressed and injured. Therefore they can no longer act as an adequate barrier to cholesterol and other substances collecting in the inner walls of the blood vessels. Additionally as the blood pressure increases and the endothelium becomes damaged, the risk of an atheroma forming is increased.

As well as stress having a significant influence upon blood pressure, it is also an important risk factor for CHD. However its direct relevance toward the development of CHD has been often questioned, “it has been surprisingly difficult to prove this link scientifically” (13). BUPA Healthcare suggests, “Stress is difficult to assess, but anything that makes excessive demands on you – especially work – seems to be associated with high blood pressure” (14). The production of the hormone adrenaline is stimulated by acute stress. The production of this hormone causes the body to release extra sugars and fats into the blood stream. This in turn makes the blood stickier which proves that not only does constant stress increase the chance of an atheroma forming but blood clotting as well. All this ultimately increases the risk of CHD.

So far it is only the modifiable factors that contribute to heart disease that have been analysed. The non-modifiable factors that effect the development of coronary heart disease are “genetic factors, diabetes mellitus, gender and age.” (15)

Genetic factors have proven to have an influence on the risk of CHD. “People with parents who suffered CHD are more likely to develop it themselves” (16). We all carry approximately 50 genes that affect the function and structure of the heart and blood vessels. Genetics can determine one’s risk of having heart disease. CHD does tend to run in families and a reason for this is that parents may pass on genes to their children that render them more liable to develop high blood pressure have high a cholesterol level or have diabetes mellitus.

The next non-modifiable factor to be studied is diabetes mellitus and the effect it can have upon the development of coronary heart disease. “Diabetics are at least twice as likely to develop angina (a severe pain in the chest) than nondiabetics” (17) Diabetes causes metabolic injury to the lining of arteries, as a result, the tiny blood vessels that nourish the walls of medium size arteries throughout the body, including the coronary arteries, become defective. These microscopic vessels become blocked, impeding the delivery of blood to the lining of the larger arteries, causing them to deteriorate and atherosclerosis results.

Finally there is also a trend in the age and gender risk factors. “Males who are under the age of fifty-five are more likely to develop CHD than women” (18) for instance. In continuance the risk of women developing CHD does seem to increase after they encounter the menopause. “The exact reason why women are protected from CHD before the menopause is not known for sure, but it does seem likely that this is related to hormones that disappear once menstruation stops” (19) Nevertheless the risk of CHD is roughly even at the age of seventy-five and above, regardless of the gender.

In conclusion, there are many factors mentioned above that can increase the risk of a person developing CHD. However in conjunction with that fact, there are many ways in which people can reduce the risk of CHD which basically involves avoiding many of these possible risk factors. It is clear to say that by reducing the risk of an atheroma forming, a person can lower their chance of developing CHD. Therefore people should not smoke, exercise regularly, eat a low cholesterol diet, avoid excessive consumption of alcohol and refrain from living any hectic form of lifestyle to avoid stress. The more risks that a person has in their life; the more chance they have of developing CHD.