Most people have a gradual deterioration over many, many years

Anne Sherling, Cardiomyopathy Association

The immune system turns in on itself, and starts to attack the muscles of the heart.

Anne Sherling, administrator for the Cardiomyopathy Association, told BBC News Online: "A number of families have children awaiting a heart transplant, but we have hundreds of people who are living with dilated cardiomyopathy who do not require a transplant.

"In many cases the condition can be controlled with medicine, and over a period of time the patient can make a good recovery."

Ms Sherling said it was "relatively rare" for people to require an immediate transplant after contracting the disease.

She said: "Most people have a gradual deterioration over many, many years, or their deterioration is managed with medication so that they can carry on relatively normal lives."

In 1999, 207 patients underwent heart transplants in the UK. Of those, 12 were under the age of six, and another seven aged 6-11.

At the end of February 174 people were waiting for surgery, and another 93 were waiting for heart and lung transplantation.

There is a severe shortage of donor organs of all types for transplant. However, the government has so far rejected calls, reiterated this week by the Royal College of Nursing, for an opt-out scheme under which organs would be taken from dead people unless specific objections were raised.

There are four main types of cardiomyopathy. One form, hypertrophic cardiomyopathy is the single biggest cause of sudden death among young people under the age of 25.