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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.