What Can Go Wrong With The Heart

A healthy heart gives the body a good blood supply so that all parts get enough food and oxygen. However, several things can go wrong with the heart. For example, a few people are born with a faulty heart. Many more people start their lives with a healthy heart, but later it becomes diseased. Some heart disease is caused by infections which may be treated with modern drugs and recovery can be quick. An example is rheumatic heart disease.

By far the most common type of heart disease occurs when one (or more) of the coronary arteries becomes partly or almost completely blocked. This is called coronary heart disease. A good way to treat coronary heart disease is to by-pass the blocked bit of coronary artery. Usually, pieces of one of the veins in the leg are used to make the by-pass. The leg does not suffer, because there are plenty of other veins there to share the job of carrying the blood.

For this operation to be successful, the heart must be stopped and by-passed completely. However, the heart is really two pumps. One delivers blood to the lungs. The other delivers blood to the rest of the body. Therefore, in order to make the operation simpler, the lungs are by-passed as well. This means that only one artificial pump is needed and an artificial oxygenator is used instead of the lungs.

The circulation diagram can be modified to show what is needed. Normal body temperature is 37 °C. Cooling the body to about 30 °C reduces the activity in all parts. Therefore less oxygen is needed. The heart is kept much cooler and treated with various chemicals which stop its muscular activity. Therefore it is not damaged when its blood supply is cut off. There is no great leakage of blood when the coronary artery is cut, because there is very little blood in it. Also, the heart has stopped beating and is perfectly still. This enables the surgeon to put the stitches in exactly the right places.

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What’s Cardiac Arrest

All parts of the body need a continuous supply of blood. For example, if the blood supply to the brain stops for longer than three minutes it becomes damaged. Other parts of the body can go without a blood supply for longer without being damaged. However, the muscular walls of the heart itself are quickly damaged if their blood supply is stopped.

Hospitals are always prepared for cardiac arrests. In a large hospital, there will usually be three or four doctors called the crash team. Their job is to get to any patient with a cardiac arrest as soon as possible. The problem is that hospitals are large, busy places. These doctors may be a long way from the patient. To overcome this, each member of the crash team carries a special bleep for emergencies. The bleeps are small radios which are tuned to a special transmitter at the hospital switchboard. There are telephones all over the hospital. If a patient has a cardiac arrest someone, usually a nurse, calls the switchboard. The switchboard operator presses a button and all the emergency bleeps make a loud bleeping noise. This noise can easily be heard by those who carry the bleeps. At the same time, the operator can tell the doctors, over the radio, where the patient is. The members of the crash team stop what they are doing. They go as quickly as possible to the cardiac arrest patient. When they arrive, they try to get the heart beating again. They may use drugs or a special electric shock machine. If these fail, an operation may be needed.

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Coronary Heart Disease

Many things can go wrong with the blood circulation. By far the most common disorder occurs when a fatty substance collects in the walls of the arteries making them narrower.

This kind of arterial disease is very serious if it occurs in the arteries leading to the brain. In this case it can cause a stroke because the brain gets insufficient oxygen. The person collapses. They might recover, but if they do the brain is often permanently damaged. Arterial disease in the coronary arteries is also serious.

The coronary arteries carry blood to the muscles in the walls of the heart. If these arteries become narrower, it may lead to a heart attack. When the coronary arteries become narrower this is called coronary heart disease or ischaemic heart disease. Coronary heart disease kills more people than anything else in Britain today. Death is caused, in this case, when the heart stops beating properly (a heart attack) and the blood supply to the brain stops. It is often very sudden and very unexpected. Some people survive one heart attack only to be killed later by another one.

Coronary heart disease is much more common in smokers than in non-smokers. Smokers who give up smoking after surviving a heart attack are less likely to have another heart attack than those who continue to smoke. Nearly all people with arterial disease of the legs are smokers. For these people, walking becomes painful and many of them get gangrene so that one or both legs have to be amputated (cut off). Gangrene is caused by lack of food and oxygen. In this case it is caused by the blocked leg arteries.

No one knows why the fatty material collects in the walls of the arteries. There seem to be several things which increase the risk of this type of arterial disease. They are: smoking, high blood pressure, obesity, high levels of a fatty substance (cholesterol) in the blood, lack of exercise, stress (worry), and old age. The disease is also more common in some families than it is in others. It is more common in men than in women up to the age of 50. After this age, it is equally common in men and women.

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Blood Circulation: from Greeks to Harvey

Two thousand years ago, the Greeks thought that blood moved backwards and forwards in the blood vessels rather like waves on a beach. They also believed that blood was gradually used up by the body, and that new blood was made from food, water and air. In 1628, William Harvey, an English doctor who worked at St Bartholomew’s Hospital in London, published a famous book about the heart.

Doctors in Harvey’s day were taught the Greek ideas about blood. They were not expected to study the heart and blood vessels for themselves. It was enough to hear about the Greek ideas and to glance at a few dissected bodies, Harvey was the first doctor to make a really careful study of the heart and blood vessels for himself. He was able to show that the Greeks were wrong. The blood moves in one direction only through the heart and blood vessels. The heart acts as a pump to keep the blood moving.

Harvey discovered the circulation of the blood. He worked out how much blood was pumped out of the heart each minute. He also showed that this was far more than could be made from the food and water taken in. This helped to support his idea that blood moves round the body continuously, and that it is not used up. Harvey was unable to see the smallest blood vessels, which we now call capillaries, but he knew that they must be there. However, soon afterwards in 1661, an Italian scientist named Malpighi used a microscope to examine the lungs of a frog. He was able to see the capillaries. Blood passes from the arteries through the capillaries to the veins. The last link in Harvey’s discoveries about blood circulation was now in place.

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Blood as transport system

You have probably seen blood in a film or filmstrip about blood, or even some fresh blood. But have you ever seen some preserved blood on a microscope slide?

Blood is a liquid with some small solid objects in it. The red blood cells carry oxygen. The white blood cells help the body to fight against infection and diseases. When the skin is cut, the platelets help to form a clot. This stops further bleeding.

The liquid part of the blood is called plasma. Plasma is water with lots of things dissolved in it, for example glucose.

The pump of you heart makes blood run in your blood vessels. One of the most important things that blood does is to carry things around the body. For example, it carries oxygen and glucose to the parts where they are needed. Blood also carries waste products away from the places where they are produced. This is why the blood and the blood vessels are called a transport system.

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Some heart exercises

Here are some exercises for your heart to figure out how fit you are.

Use a box, chair or stool which is about 40-50 cm high for the physical exercise. Carry out the exercise like this. First, step up onto the box and stand on it with both legs straight. Then step down and stand on the floor with both legs straight. Step up and down like this for a total of four minutes. Do not try to go too fast. You should keep going at a steady rate of about one step up every two seconds. Step up and down, without stopping, for four minutes. Then sit down and rest.

Rest for exactly one minute. Then get your partner to take your pulse for 30 seconds. This is your first pulse reading. Write it down in your results table.

Rest for a further 30 seconds. Then get your partner to take your pulse for another 30 seconds. This is your second pulse reading. Write it down. Repeat the previous stage. This gives you a third pulse reading.

Work out your fitness score. Change over and let your partner do the fitness test.

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Your heart is the best pump

We shall start with a couple of questions. Why do we have a heart? What does it do? What’s the pulse?

There are blood vessels all over the body. Some are easy to see, because they are close to the skin surface. Most blood vessels cannot be seen because they are buried deep among the muscles and other tissues. If you press your fingertips against some blood vessels you will feel a regular throbbing movement. This is called the pulse. Blood vessels which have a pulse are called arteries. They carry blood away from the heart. There are various places on the body where the pulse can be felt. The pulse is usually found on a person’s left wrist.

Each pulse throb is caused by a sudden rise in the pressure of the blood in the artery. What do you think causes this sudden rise in pressure of the blood in the artery? Okey, here’s another question: what makes the hot water move through the pipes and radiators of a modern central heating system?

Blood vessels are like pipes. The blood is like water. A pump is needed to move the blood through the blood vessels. This pump is the heart. Every time it beats, the heart forces blood out through the arteries. With each heartbeat there is a rise in pressure. This causes the arteries to swell, which is what you can feel at the pulse points. This explains why pulse rate is the same as heartbeat rate.

Your heart is the best pump ever made. In most people, the heart works all the time, without repair or servicing, for the whole of their lives. The speed at which it beats can be changed, in a few seconds, from about 70 to 140 beats per minute or more. Rates of 200 or more occur during violent exercise. Most important of all, the heart does not damage the blood as this passes through it. Blood is a delicate thing. No man has ever built a pump which is so gentle, so strong and so reliable. But the heart can go wrong if it is not looked after properly.

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