Blood flow problems in the heart could be to blame for angina-like chest pains which have baffled experts for decades, suggest scientists.

Experts at the Royal Brompton Hospital in London believe they may have tracked down the cause of "cardiac syndrome X".

Patients, mainly menopausal women, who experienced this are normally tested to see if they have angina, which is caused by narrowing of the heart arteries.

However, these tests come up negative - in the past, some of them have been accused of making the pain up.

Other theories included an unusual sensitivity to pain, or abnormalities in the tiny blood vessels supplying the heart muscle.

However, with no obvious problem, treatment is extremely difficult, although drugs such as beta-blockers have been given to some patients.

Scans

The Royal Brompton study, published in the New England Journal of Medicine, used magnetic resonance imaging (MRI) scans to try to spot what was going on during a syndrome X attack.

Before taking a scan, they gave the patients a drug to simulate the effects of exercise.

They found there was reduced blood flow to an area of the inner surface of the heart called the subendocardium, even though blood flow to the heart as a whole appeared completely normal.

Difficult question

It is possible that depriving this region of the heart of oxygenated blood is enough to trigger the pain.

Doctors are now hopeful that the problem can be both diagnosed, and perhaps even treated in future.

Professor Dudley Pennell, a cardiology expert from Imperial College London, said: "This new research shows that advanced technology can solve longstanding difficult questions in cardiology.

"This research gives hope to thousands of chest pain sufferers that in time we may be able to offer not only a proper diagnosis, but effective treatment."

However, the finding may not be as clear cut as hoped.

Reservations

Dr. Julio Panza of Washington Hospital Center in Washington DC, agreed in an accompanying article that the research adds to evidence that syndrome X is a heart disease.

However, he said the drug adenosine, which was given to the patients to simulate the stress of exercise, could have caused the effect seen on MRIs.

Alison Shaw, Cardiac Nurse at the British Heart Foundation, says:

"The term 'Cardiac Syndrome X' describes those people who have anginal chest pain, with positive ECG stress tests but with normal coronary angiograms.

"In other words, there is no evidence of any narrowing of the arteries that might be causing the pain." "This new research, which is also partly funded by the British Heart Foundation shows that the blood flow to the inner lining of the heart may be affected whilst under stress."

"The results are promising and have shown the possible benefits of using non-invasive MRI scanning.

"Hopefully it will also lead to better diagnosis and more specific treatments for people with this condition."