Heart Terms Explained

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Coronary Heart Disease

Heart attacks are commoner in older than in younger people. Under the age of 50, the disease affects more men than women. After the menopause females lose the protection of their hormones. Between 50 and 80 years of age the heart attack rate in women catches up with the rate in men.

How Your Heart Works

The body contains roughly 5 litres (8 pints) of blood, which is continuously re-circulated by the heart. The heart beats around 100,000 times and pumps some 5,000 gallons a day. Like all other muscles, the heart needs a good supply of oxygen rich blood in order to maintain this performance. It receives its bloods supply from the coronary arteries. (see Figure 1)

heart1

Figure 1.

The heart is two separate pumps which work together. The right side receives blood, which has little oxygen and pumps it back to the lungs where the blood is filled with fresh oxygen. The left side of the heart then receives this oxygen rich blood and pumps it into the arterial system which supplies the rest of the body.

A heart attack occurs when one of these coronary arteries becomes blocked - usually by a clot. The blockage deprives part of the heart muscle of blood. This causes pain. It causes pain like that of angina, but unlike angina the pain does not go away after a few minuites of rest. The affected part of the muscle dies without urgent treatment.

Chambers and Valves

The heart is divided into 4 chambers: (see Figure 2)

  1. Right Atrium
  2. Right Ventricle
  3. Left Atrium
  4. Left Ventricle
heart2

Figure 2.

Each chamber has a sort of one-way valve at its exit that prevents blood from flowing backwards. When each chamber contracts the valve at its exit opens. When it is finished contracting the valve closes so that blood does not flow backwards.

  1. Tricuspid valve- is at the exit of the Right Atrium.
  2. Pulmonary valve - is at the exit of the Right Ventricle.
  3. Mitral valve - is at the exit of the Left atrium.
  4. Aortic valve - is at the exit of the Left Ventricle.

When the heart muscle contracts or beats (called systole) it pumps blood out of the heart. The heart contracts in two stages. In the first stage the Right and Left Atria contract at the same time, pumping blood to the Right and Left Ventricles. Then the Ventricles contract together to propel blood out of the heart. Then the heart muscle relaxes (called diastole) before the next heartbeat. This allows blood to fill up the heart again.