Development And Consequences Of Atheromatous Plaques Biology Essay

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Cardiovascular Disease (CVD) is the broad term given to cover a range of diseases that affect the heart and circulation. Angina (chest pains), Myocardial Infarction (heart attack) and Stroke are all examples of a CVD. (British Heart Foundation n.d, online)

The above diseases are linked to a condition called Atherosclerosis. Atherosclerosis literally translates as "hardening of the arteries" and is a build-up of yellowish fatty deposits (plaques) on the inside of arteries. (Fullick et al, 2008) These plaques develop because as well as transportation of oxygen, the blood also carries out the function of carrying nutrients to the tissues in the body and complications can arise as a result of this. The nutrients that are important in CVDs are Fats (Lipids). As blood is mostly made up of water, and fat and water don't mix, the body binds the fat to something else in order to be carried by the blood. This is done by binding the lipids with protein to form particles known as lipoproteins. There are different types of lipoproteins and those that have a detrimental effect in terms of CVDs are known as low density lipoproteins (LDLs). It is their role to take blood lipids, in particular cholesterol to the body's cells. The job of high density lipoproteins (HDLs) is to take away cholesterol from the cells and therefore are often referred to as 'good' cholesterol. Cholesterol is an important constituent of all the cells in the body; its roles include the making of hormones and substances in the nervous system. Problems with cholesterol arise when the liver is unable to dispose of it satisfactorily, and as a result builds up in the blood and when carried by the LDLs, sticks to the arteries (DOH, 1994). The previously smooth lining of the arteries start to develop fatty streaks as the cholesterol circulates in the body. This usually begins in late childhood and continues throughout life. The reason why atherosclerosis usually occurs in arteries rather than veins is because the blood flows fast under high pressure, thus putting more strain on the endothelium lining. The pressure in veins is lower and therefore causes less damage to the endothelium.

Once the damage has occurred, the body's inflammatory response commences and white blood cells arrive at the site of the damage. The cells accumulate chemicals from the blood, in particular cholesterol. This leads to a fatty deposit known as an atheroma forming on the endothelial lining of the artery. Fibrous tissue and calcium salts are also prone to build around the atheroma , turning it into a hardened plaque. As a result of this, part of the artery wall also hardens and is less elastic than it should be, hence the name atherosclerosis (Which? Consumer Guides, 1991). The following diagram illustrates the development of atherosclerosis:

Source - Edexcel Biology

As a result of the plaque, the lumen of the artery becomes much smaller, this increases the blood pressure and makes it more difficult for the heart to pump blood around the body. Because of the raised blood pressure, endothelial lining damage is more likely to occur in other areas, and more plaques will form causing a further rise in blood pressure. Also because substances such as calcium can stick to plaques, this can make them hard and brittle. Therefore the plaques are susceptible to cracking and sometimes bleeding occurs inside the artery. As a result of this bleeding, blood forms clots to stop the bleeding and help heal the cut. The formation of these clots makes the plaques even bigger, and takes up more room inside the artery and leaves less room for the blood to flow through. Atherosclerosis can affect any artery in the body, including arteries in the heart, brain, arms, legs, and pelvis. As a result, different diseases may develop based on which arteries are affected. For instance, stroke occurs when an artery in the brain bursts so that blood leaks into brain tissue (brain haemorrhage) or when there is a blockage in a brain artery due to atherosclerosis or a thrombus (blood clot). The brain tissue which is affected by this is starved of oxygen and dies (cerebral infarction). A heart attack (Myocardial infarction) is when a large branch of a coronary artery is obstructed by a blood clot, part of the heart muscle is deprived of oxygen and dies.

It is not uncommon for the disease to be asymptomatic (The illness may be present, but the patient does not experience any symptoms) in the early stages of development. This is known as silent ischemia in coronary heart disease, when there is not enough oxygen-rich blood supplied to the heart muscle to meet the heart's needs. However as the disease progresses and the heart deteriorates, some symptoms will become obvious. These include:

Cardiac arrest, which will normally manifest after a prior heart attack but can occur as a primary symptom.


Angina pectoris or chest pain which will not persist when resting.

An overall feeling of discomfort.

Shortness of breath that will normally occur after physical activity or when lying flat.

An irregular heartbeat.

Feeling dizzy and light-headed.

Feeling general weakness after any kind of additional activity.

Heart palpitations.

Pain in the jaw, shoulder blades and left arm that is provoked by exercise or by resting.

Most symptoms occur during physical activity or exercise, as this is when blood flow is most essential for the body.

Everybody has some risk of developing atheroma. However, certain 'risk factors' increase the risk. Risk factors include:

Lifestyle risk factors that can be prevented or changed (Fosberry et al, 2000):

Smoking - Multiplies the chance of developing coronary heart disease.

Lack of physical activity (a sedentary lifestyle) - Risk decreases as more exercise is taken. Aerobic activity helps controlling blood cholesterol, diabetes and obesity, and can also help lowering blood pressure.

Obesity - Variety of adaptations/alterations in cardiac structure and function occur as excessive adipose tissue accumulates.

An unhealthy diet and eating too much salt - Risk increases with high intake of saturated fats and salt. Consuming antioxidants, commonly found in fruit and vegetables decreases risk.

Excess alcohol - High intake causes blood pressure to rise and more chance of developing atherosclerosis.

Treatable or partly treatable risk factors:

Hypertension (high blood pressure) - Risk increases with increasing blood pressure.

High cholesterol blood level - Direct relationship between concentration of cholesterol in the blood and risk of coronary heart disease. Anything above 250mg of cholesterol per 100 cm³ of blood is considered to be high

Diabetes - There is an increased risk for sufferers of diabetes.

Fixed risk factors - ones that you cannot alter:

A strong family history. This means if you have a father or brother who developed heart disease or a stroke before they were 55, or in a mother or sister before they were 65.

Being male - Protection is provided by Oestrogen for women which occurs naturally or by hormone replacement therapy.

Age. The older you become, the more likely you are to develop atheroma.

Ethnic group. For example, people who live in the UK with ancestry from India, Pakistan, Bangladesh, or Sri Lanka have an increased risk.

Some risk factors are more 'risky' than others. For example, smoking probably causes a greater risk to health than obesity. Also, risk factors interact. So, if you have two or more risk factors, your health risk is much more increased than if you just have one. For example, a middle aged male smoker who does little physical activity and has a strong family history of heart disease has quite a high risk of developing a cardiovascular disease such as a heart attack or stroke before the age of 60. Research has also shown fibrinogen to be associated with traditional cardiovascular risk factors. Elevation of fibrinogen may provide a mechanism for risk factors to exert their effect. Also, fibrinogen levels were higher among subjects with cardiovascular disease compared with those without disease (Ernst, 1993).

CVDs can be diagnosed using a variety of different methods. An Electrocardiogram (ECG) is a test that records the electrical activity of the heart. With each heart beat, an electrical impulse travels through the heart. This impulse causes the heart muscle to squeeze and pump blood from the heart. An ECG reveals whether:

• The electrical impulse is normal, slow, fast or irregular.

• The heart is too large or overworked.

• There is damage to the heart muscle from a heart attack.

A cardiac stress test follows the same procedure as the above mentioned ECG, however the monitoring takes place while the person is walking on a treadmill rather remaining sitting as is the case in an ECG. Blood pressure is also monitored during the test which starts gentle and incrementally gets more difficult. This test is believed to be more accurate than an ECG as it reveals how the heart copes when under strain.

The cardio angiography is an invasive procedure using a catheter which shows the specific sites of narrowing in coronaries. Dye is injected down the coronary arteries. The arteries and their smaller branches then show up clearly on an X-ray. Blood tests can also be used in order to check cholesterol levels. Chest X-rays shows the size of your heart and whether there is fluid build up around the heart and lungs. Finally an Ejection fraction (EF) test determines how well your heart pumps with each beat.

Treatment for CVDs can be in the form of drugs which can lower blood pressure, decrease the risk of blood clotting, prevent abnormal heart rhythms and decrease concentration of cholesterol in blood. If these treatments are not successful, then coronary artery by-pass may be necessary. This procedure involves using a blood vessel from the leg to replace the diseases vessel. A completer heart transplant is the method used as a last resort, whereby a working heart from a recently deceased person is implanted into the patient. The above treatments can be avoided by reducing the risk of developing a CVD. This can be achieved by making lifestyle changes in the following ways (WHO n.d, online):

Limit energy intake from total fats and shift fat consumption away from saturated fats to unsaturated fats and towards the elimination of trans-fatty acids;

Increase consumption of omega-3 fatty acids from fish oil or plant sources;

Consume a diet high in fruits vegetables, nuts and whole grains, and low in refined grains.

Avoid excessively salty or sugary foods.

At least 30 minutes of regular physical activity daily

Avoid smoking

Maintaining a healthy weight.