One of the commonest diseases to affect the heart is coronary heart disease (CHD). It's usually caused by atherosclerosis, a build up of fatty materials within the walls of the arteries.
In CHD, the arteries that supply the heart with oxygen and nutrients become narrowed by atherosclerosis. This restricts the supply of blood and oxygen to the heart, particularly during exertion when there are more demands on the heart muscle.
What are the symptoms of CHD?
The main symptom is angina, caused by insufficient oxygen reaching the heart muscle because of reduced blood flow.
Angina is a feeling of heaviness, tightness or pain in the middle of your chest that may extend to, or just affect, your arms (especially the left), neck, jaw, face, back or abdomen.
It's most often experienced during exertion - if you run for a bus, for example, or climb stairs. It may occur in cold weather, after a heavy meal, or when you're feeling stressed. It can subside once you stop what you're doing and rest, or take medication.
Other CHD symptoms
The following symptoms are by no means always owing to CHD, and could be harmless or caused by other medical conditions. However, if you experience any of them it's a good idea to make an appointment to see your doctor:
- Unusual breathlessness when doing light activity or at rest, or breathlessness that comes on suddenly.
- Palpitations - awareness of your heart beat or a feeling of having a rapid and unusually forceful heart beat, especially if they last for several hours or recur over several days and/or cause chest pain, breathlessness or dizziness.
- Fainting - although not always a serious symptom, fainting is due to insufficient oxygen reaching the brain, so you should report it to your doctor.
- Fluid retention or puffiness (the medical term is oedema) is an abnormal accumulation of fluid in the tissues of the ankles, legs, lungs or abdomen, for example. Although a mild degree of ankle oedema may be quite normal - for example, on a hot day - it can be a sign that the heart isn’t pumping as well as it should (this is known as heart failure). Fluid retention in the lungs, or pulmonary oedema, can cause intense shortness of breath, and may be life-threatening.
- Bluish-tinged fingernails or lips (known medically as cyanosis) can be the result of too little oxygen in the blood.
- Fatigue is a common symptom of heart disease, but has numerous causes, including depression. It's always worth seeing your doctor if you feel unusually tired, especially if this is combined with symptoms that can’t be explained.
Heart attack?
Unfortunately, for many people the first indication that something’s wrong is a heart attack.
This happens when the blood supply to a part of the heart muscle is completely interrupted or stops, usually when a blood clot forms in a diseased coronary artery that's already become narrowed by atherosclerosis.
The pain of a heart attack is often severe, and is frequently described as a central, crushing type of pain - like a tight band around the chest. Unlike angina, the pain doesn't subside when you rest.
Sometimes it can be mild, and is mistaken for indigestion. Some people have a heart attack without experiencing pain.
Other heart attack symptoms include sweating, light-headedness, nausea or breathlessness which, again, aren’t alleviated by rest.
If you suspect you, or someone else, is having a heart attack, seek medical help immediately by calling 999. Modern treatments can restore the blood supply to the heart muscle. The sooner treatment is given, the less permanent damage there will be.
What causes CHD?
The most common cause is atherosclerosis. This is a build up of fatty materials within the walls of the arteries throughout the body, most importantly in the arteries to the tissues of the heart - the coronary arteries.
During this process, the inner lining of the arteries becomes furred with a thick, porridge-like sludge (atheroma), consisting of fatty deposits of cholesterol, cell waste and other substances.
These form raised patches on the artery wall - known as 'plaques' - that narrow the arteries, reducing the space through which blood can flow. At the same time, the blood becomes more prone to clotting.
These growing plaques may block the delivery of nutrients to the artery walls, causing the arteries throughout the circulation to lose their elasticity. In turn, this can lead to high blood pressure, which also increases the risk of CHD.
A heart attack occurs when one of the coronary arteries blocks completely. This final step usually happens when a plaque splits open for some reason, causing a blood clot to form on its surface that obstructs the flow of blood. It’s not yet understood why plaques split open, but inflammation seems to play a part.
When the supply of oxygen and nutrients is completely blocked, the heart muscle and tissue supplied by that artery dies.
Some people are particularly predisposed towards developing atherosclerosis, due to inherited genetic factors. They may have a family history of people dying at a young age from CHD.
An unhealthy diet, lack of exercise, diabetes, high blood pressure and smoking all increase the risk.
Other heart diseases
Other diseases that commonly affect the heart include:
- Infection: bacterial infections are much rarer these days thanks to antibiotics, but can damage the valves of the heart as well as other tissues. Viral infections can damage the heart muscle leading to heart failure, or cause abnormal heart rhythms.
- Congenital heart disease: there's a range of structural abnormalities that can develop in the heart as a baby grows in the womb. These may cause abnormal flow through the heart (for example, through a septal defect or 'hole in the heart') or through the rest of the circulation, and put excessive strain on the infant's heart after it's born.
- Cardiomyopathy: this is disease of the heart muscle and may occur for many different reasons, including CHD, high blood pressure, viral infection, high alcohol intake and thyroid disease.
For many people with heart disease, there are a combination of factors that can cause problems. For example, CHD (most adults have some degree of atherosclerosis, especially if they smoke) and high blood pressure are often found together.
Scientists have yet to unravel all of the causes of heart disease. However, certain risk factors can increase your likelihood of developing it. You can’t do much about some of them, such as your age, gender or ethnic group, but risk factors you do have some control over include what you eat, whether you smoke, and the amount of exercise you take.
Key risk factors include:
Your age
It’s recognised that the risk of developing CHD increases with age. Atherosclerosis takes a long time to develop, and arteries naturally become less elastic as we age, often leading to a greater risk of high blood pressure.
Your gender
Many people think of CHD as a male problem. In fact, it accounts for the death of more women than any other disease.
The female sex hormone oestrogen protects against CHD during a woman’s reproductive years by creating a more favourable balance of blood fats and contributing to the elasticity and health of arteries.
After the menopause - or following a total hysterectomy in which the ovaries and uterus are removed - this natural protection can disappear.
The contraceptive pill increases a woman’s risk of clotting problems, such as thrombosis or a heart attack. Although the risk is still small, it’s considerably greater if you smoke. You should consult your doctor before taking the pill.
Your genes
If you’ve a family history of CHD or factors predisposing to it, such as high cholesterol (familial hyperlipidaemia) or blood pressure, you're more at risk.
Your ethnic background
If you’re black or Asian you’re more at risk of heart disease, although different underlying risk factors are at play for each group. If you’re Asian, you’ve a higher risk of developing diabetes, which is a risk factor. If you’re black, you’re more at risk of high blood pressure.
Diabetes
If you have diabetes you’re three times more likely to develop CHD. You’re also more likely to have silent ischaemia (painless angina or a heart attack), because diabetes can affect the nerves which send pain messages. This is especially dangerous because as the person doesn’t receive any warning that they have problems, they don’t seek help which may prevent further damage.
Your weight
Even being moderately overweight increases your risk of CHD. This may be because you're more likely to develop diabetes, have raised blood cholesterol levels and high blood pressure. It's also more difficult to be physically active if you are carrying excess pounds.
Your shape
Apple-shaped people who carry fat around their waist are more at risk of CHD than pear-shaped people who carry excess weight around their hips. The tendency to a particular shape is largely inherited, so if one or both your parents are 'apples', it's worth taking particular care over diet and exercise to lose excess fat.
Your activity levels
Watching too much television and taking the car instead of walking both increase your risk of obesity and, consequently, your risk of CHD. Lack of activity also decreases your body's ability to extract oxygen from your blood, weakens your bones (leading to a risk of osteoporosis) and your muscles, and encourages high cholesterol levels.
Blood pressure
Blood pressure is the force of blood in your arteries and is determined by how hard your heart works and the health of your blood vessels.
High blood pressure (or hypertension) is when the pressure is persistently higher than it should be (above 140/90 in healthy individuals), causing increased strain on your arteries. Over time, the force of the blood flowing through the arteries causes the smooth lining to roughen and the walls to become thicker. This causes the arteries to narrow and become less elastic.
Because high blood pressure often has no symptoms it's important to have your blood pressure checked regularly, so you can take steps to reduce it if it's raised, before it leads to heart disease or a stroke.
Your cholesterol
Cholesterol is a waxy, fatty substance made by your liver. It's also present in some foods such as animal fats, eggs and shellfish. Your body needs some cholesterol to produce hormones and to produce the bile needed to digest fat. It's also the main ingredient of cell membranes.
Cholesterol travels around your bloodstream in special proteins called lipoproteins. There are two types: low-density lipoproteins or LDL (also known as 'bad cholesterol'), which carries cholesterol to your body's cells, and high-density lipoproteins or HDL (also known as 'good cholesterol'), which helps clear excess cholesterol from your arteries and carries it back to your liver to be destroyed.
If you have high levels of LDL and low levels of HDL you're more at risk of heart disease.
Factors predisposing towards unhealthy cholesterol levels include eating a diet high in saturated (animal) fats and/or transfats found in processed foods, being overweight, drinking too much alcohol and not doing enough exercise.
Cholesterol and atherosclerosis
Atherosclerosis, a build up of fatty materials within the walls of arteries, is set off when LDL cholesterol undergoes a chemical reaction called oxidation - the same reaction that causes butter to go rancid.
Oxidation is caused by free radicals - harmful molecules produced as a result of the normal metabolism that occurs within the body.
Free radicals also come from ionising radiation from the sun's rays, ozone and nitrous oxide from car exhausts and cigarette smoke. These free radicals contribute to atherosclerosis that results in heart disease.
Smoking
Smoking increases your risk of having a heart attack two-fold or three-fold. In fact, if you're under 50 and smoke, you're five times more likely to die of CHD than a non-smoker.
There are several reasons for this. Nicotine triggers the release of the stress hormone adrenalin, which raises your heart rate and blood pressure, increasing your heart's need for oxygen.
Carbon monoxide, found in tobacco smoke, displaces oxygen from your blood cells, depriving your heart of oxygen. Other chemicals in cigarette smoke trigger the release of free radicals, the harmful molecules involved in the development of atherosclerosis.
Smoking also decreases the level of ‘good fats’ in the body, such as HDL, and may increase blood pressure and make the blood more likely to form clots. Smoking is particularly dangerous when other risk factors such as diabetes or high blood pressure are also present.
Raised homocysteine levels
Some people with CHD have raised levels of a substance called homocysteine, an amino acid (one of the building blocks that make up protein) that your body uses to build tissues.
Raised homocysteine levels are thought to damage the lining of arteries, a crucial step in the development of atherosclerosis. They've been found to be a factor in the oxidation of cholesterol and also appear to increase blood clotting.
Smoking and inactivity lead to raised homocysteine levels, and low levels of folic acid and vitamins B6 and B12, in particular, have also been linked to this.
However, recent studies have failed to show convincingly that high homocysteine levels are associated with an increased risk of CHD, and there's no proof that efforts to lower homocysteine (such as taking folic acid supplements) can protect from atherosclerosis.
Because the evidence remains uncertain, experts are reluctant to designate a raised homocysteine level as a risk factor for CHD until further research provides a clearer answer.
This article was last medically reviewed by Dr Trisha Macnair in March 2007.
First published in June 2001.
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