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KS5 Biology Lesson Plan 8 – Heart and Circulation Science at Work in Healthcare Post – 16 Science Education Pack Resource Sheet 8.2 – Heart Disease Heart disease Every three minutes a British adult dies from heart disease. In fact, the UK has one of the highest rates of heart disease in the world. But it isn’t just about heart attacks; there are a range of different conditions which come under the label of heart disease. Your hard-working heart Your heart is a complex organ that works incredibly hard. On average your heart will pump around about 100 000 times a day, moving 8 tonnes of blood. That’s 2.5 billion times and 200 000 tonnes of blood in an average lifetime! People who smoke or have a poor diet and do not exercise increase the risk of heart disease interfering with this process. The result can be serious illness or death. Although modern healthcare has allowed the development of a wide range of tests and treatments which can alleviate the symptoms and save lives, the most effective measure is to prevent the onset of heart disease by leading a healthy lifestyle. Heart failure Heart failure occurs when the heart fails to pump blood as it should. This means that the blood cannot deliver the supplies of oxygen and glucose that the cells need to function properly. Blood can collect in the veins, causing swelling in the feet ankles and legs. This is called oedema. Sufferers can also experience shortness of breath, tiredness, a general feeling of being run-down, confusion and the inability to think clearly. Heart failure can be caused by blocked arteries, damage caused by a previous heart attack, high blood pressure (hypertension), diseases of the heart muscles or valves and other infections. Heart attack (Myocardial infarction) Technically speaking, all heart disease is a form of heart failure. Because of their speed and severity, heart attacks could be described as acute heart failure. KS5 Biology Lesson Plan 8 – Heart and Circulation Science at Work in Healthcare Post – 16 Science Education Pack Heart attacks occur when the blood supply to a part of the heart muscle is blocked. This causes damage to the affected muscle and can be fatal. Heart attacks are most frequently caused by plaque. Plaque is a mixture of cholesterol, fat and blood cells. This can build up on the walls of arteries due to poor diet, lack of exercise or smoking and restrict the flow of blood. Pieces of plaque may tear free and can lodge in one of the heart’s blood vessels. When this happens, the blood supply to the heart is affected and you have what is known as a coronary thrombosis or a coronary occlusion. Coronary arteries can also sometimes go into spasm or temporarily contract, causing a similar effect. Some patients may not be aware that they have actually had a heart attack until they are examined as they may not have any of the symptoms mentioned above. Angina Angina occurs when the coronary arteries have been so narrowed by atherosclerosis (the build up of plaque) that they cannot supply enough blood to the heart muscle when it needs to beat faster. Angina is felt as a pain, heaviness or tightening of the chest which can spread to the arms, neck, jaw, face, stomach or back. It is usually brought on by exercise, emotional stress or high temperatures. Ventricular Hypertrophy This is a condition where the heart enlarges and weakens. It is caused by long term high blood pressure (hypertension) which in turn can be caused by a high salt diet and diabetes. Arrythmia An average resting heart rate can be between 60 and 100 beats per minute for an adult. Sometimes, the rhythm of this beating can be disturbed when the heart’s in-built pacemaker, the sino-atrial node, develops an abnormality. This can result in a heart rate which is either too low or too high. A slow heart rate is called bradycardia and can cause fainting, dizziness and fatigue. A heart beat which is too fast is called tachycardia and can also cause fainting, dizziness and fatigue as well as palpitations. KS5 Biology Lesson Plan 8 – Heart and Circulation Science at Work in Healthcare Post – 16 Science Education Pack Rapid beating of the ventricles can lead to ventricular fibrillation, where the ventricles simply quiver and cannot pump any blood. This can lead to collapse and sudden death unless rapidly treated by defibrillation. This technique uses a device called a defibrillator to deliver an electrical shock to the heart. This has the effect of Fig 1. A paramedic demonstrates a portable defibrillator depolarising a critical mass of heart muscle, allowing the sino-atrial node to re-establish a normal heart rhythm. In some circumstances, areas of the heart other than the sino-atrial node may also start an electrical impulse. This impulse does not follow the normal electrical pathway and can also cause arrhythmia. Diseases of the heart muscle Heart disease is called cardiomyopathy and there are several different types: Hypertrophic cardiomyopathy – in the majority of cases this is a hereditary disease where the heart muscle thickens and stiffens. This may cause the heart valves to leak and reduce the blood holding volume of the heart. Dilated cardiomyopathy – the heart cavity stretches and becomes enlarged. The heart is weakened and cannot pump normally resulting in breathlessness as fluid builds up in the lungs. This condition can be caused by a virus, autoimmune diseases or excessive consumption of alcohol. Restrictive Cardiomyopathy – the myocardium or middle layer of the heart cavity wall becomes stiff and restricts the filling of the ventricles with blood. KS5 Biology Lesson Plan 8 – Heart and Circulation Science at Work in Healthcare Post – 16 Science Education Pack Diseases of the heart valves The heart valves are crucial in making sure that blood flows around the heart in the correct direction. If they fail to work correctly, by either not opening fully (valve stenosis) or by not closing properly (valve regurgitation) it can result in a build up of fluid in the lungs or lower part of the body. Symptoms can include tiredness or breathlessness, dizziness and fainting. Heart valve disease is often congenital, meaning that it is present at birth. The valves are formed from two parts rather than the normal three, causing excessive wearing and thickening of the valve. Heart valve disease can also be the result of an infection which can cause damage to the valves in a very short period of time. Acute infections, sometimes as a result of a tooth abscess, are also a cause of heart valve disease.