Postmenopausal women given oestrogen therapy after a first heart attack were just as likely to have another one as those on placebo, say researchers.

Oestrogen therapy does not reduce the overall risk of further cardiac events in postmenopausal women who have survived a heart attack Dr Nicola Cherry

The evidence reinforces the view that HRT should not be prescribed solely to prevent heart attacks despite earlier suggestions that it could protect the heart.

The research, published on the website of medical journal, The Lancet, adds to the growing debate over the health benefits of HRT.

Studies had suggested that some types of HRT might be beneficial in women at risk of heart attack.

However, this has proved controversial. In July, a major US study into the long-term effects of HRT was halted early.

Women taking a certain combination of HRT were found to have a very slight increase in heart disease.

Secondary prevention

The new study found that women given HRT after a heart attack were just as likely to have another attack as those not taking it.

Principal investigator Dr Nicola Cherry said: "Oestrogen therapy does not reduce the overall risk of further cardiac events in postmenopausal women who have survived a heart attack.

Millions of women take HRT

"This study provides insufficient evidence of benefit to alter current guidance against the use of HRT for the secondary prevention of cardiovascular disease."

A team at the University of Manchester looked at 1,000 British women who had survived a heart attack. They were all postmenopausal and aged between 50 and 69.

Half were given oestrogen therapy and the others were given a placebo, for two years.

There was no difference in heart attack rates or deaths from heart attacks at the end of the study.

The overall death rate was slightly lower among women taking HRT but the researchers say this was not statistically significant.

Fiona Kirkwood, cardiac nurse for the British Heart Foundation, said recent randomised studies had shown that combined hormone replacement therapy (oestrogen and progesterone) did not provide any protective benefit to women for coronary heart disease.

She told BBC News Online: "This large study tested oestrogen therapy alone as a treatment option, and demonstrates that this also does not reduce overall risk of further cardiac events in post menopausal women after they have had a heart attack."

Unresolved questions

Experts say there are many outstanding questions about the effects of HRT.

Further studies are being carried out to understand more about how it affects women over long periods of time.

Previous studies had suggested that HRT increases the risk of some cancers, particularly breast cancer, but protects against osteoporosis and coronary heart disease.

However a Women's Health Initiative study, recently found it was linked to a 29% increase in heart attacks and increase in other cardiovascular conditions.