BBC News Online talks to Louise Rainey, who was just 37 when she was diagnosed with coronary heart disease and told she needed a heart bypass operation.

"I first noticed something was wrong at around Christmas time, 2001.

"I began to get pains in my chest whenever I did anything which needed particular exertion, such as walking very fast or running for the bus.

"I thought it was some sort of chest infection."

Louise, who lives in London with her husband and daughters Ella, three, and Lois, one, was just 37 at the time.

The doctors said it just happens to some people

She added: "I just ignored it for several months because most of the time I felt fine."

Eventually Louise, who works as a public relations officer, went to see her GP in January 2002.

"I said I had chest pains, and she looked a bit aghast and said it would be my heart that would be causing the problem.

"I wasn't really worried. But then she said I should go down to the hospital immediately - and that got me a little bit worried."

Fearing the worst

She was seen at Hammersmith's Hospital Rapid Access Chest Clinic.

Tests were carried out, including an ECG - an electrocardiogram - where the rhythm and activity of the heart is recorded, and an angiogram which shows if arteries have narrowed.

Louise said the angiogram provided the final answer as to what was wrong: "It was immediately obvious there was a blockage."

She was offered the choice of angioplasty, where a balloon is inserted into the artery and inflated to squash the fatty tissue responsible for the narrowing or a heart bypass.

"Because it was a fairly serious narrowing and it was in a place that wasn't easy to get to I decided to have the bypass."

She added: "I still assumed everything was going to be all right, but you do obviously fear for the worst and worry for the kids."

No family history

Louise's operation took place in March last year, and it has enabled her to get back to normal.

She is back at work, makes sure she exercises regularly and eats healthily.

But no one is sure why she became ill.

She said: "My cholesterol was low, I'd never had blood pressure problems and there was no family history of heart problems.

"The doctors said it just happens to some people."

Louise added: "I worried about breast cancer, and things like that which you tend to worry about as a youngish woman.

"I never really thought about of heart disease as a major worry, except for older people.

"I think I'd probably have led a healthier lifestyle before, if I had thought about it."