artery becomes furred up or partially blocked with fatty material called atheroma, that artery cannot then supply enough blood to the heart muscle to meet its needs during exertion or activity. The muscle 'cramps', causing chest pain. This is known as angina . If the poor blood supply to the heart worsens, so that chest pains start to happen more easily and with less exertion, it's known as unstable angina . This requires increasing levels of heart medication or active surgical intervention such as an angioplasty or heart bypass surgery. When a coronary artery is completely blocked and no blood or oxygen reaches the heart muscle served by that artery, it causes a heart attack . This also causes chest pain as the heart muscle served by that artery dies. Depending on which part of the heart muscle is affected and the severity of damage to the heart muscle, the effects of a heart attack can range from a good recovery to instant death. Heart disease is the biggest killer in the UK, often causing death before the person reaches hospital. The materials in this web site are in no way intended to replace the professional medical care, advice, diagnosis or treatment of a doctor. The web site does not have answers to all problems. Answers to specific problems may not apply to everyone. If you notice medical symptoms or feel ill, you should consult your doctor - for further information see our Terms and conditions .