In their hearts, it seems, men and women really are different.

The same invasive treatments for acute heart problems that can save lives in men may actually harm women, although reasons for this are unclear, researchers told the European Society of Cardiology annual meeting on Monday.

A small-scale analysis involving 184 women patients by Swedish doctors found eight deaths among those receiving aggressive treatment, compared to just one death after a year in a group given more conservative care.

“We should be cautious about these results but, taken together with findings from previous studies, it suggests that results from men do not necessarily apply to women,” said lead researcher Eva Swahn of University Hospital, Linkoping, Sweden.

“Women should be equally treated but equal doesn’t mean the same,” she added.

Men and women are usually lumped together in clinical studies, so the latest findings - based on a sub-analysis of a larger trial assessing GlaxoSmithKline’s drug Arixtra - gives a rare perspective on gender differences.

Swahn’s study involved women with an average age of 68. They were divided into two equal groups and either given a routine invasive heart X-ray, followed by a heart procedure if needed, or simply monitored and only X-rayed if they showed symptoms.

A total of 58 percent of the first group received either bypass surgery or angioplasty, a non-surgical alternative in which a tiny balloon is inflated in a clogged coronary artery, while only 31 percent of the second group had such procedures.

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One clear difference was that major bleedings were more frequent in the early invasive group and Swahn said it was possible that women had a higher bleeding tendency, making invasive procedures more dangerous.

Daniel Jones, cardiologist at the University of Mississippi Medical Center and president of the American Heart Association, said the results were inconclusive but did underline the need for more research. “I don’t think it’s surprising that there are probably differences in the way we ought to be managing women from men. We cannot pretend that research done in men can easily be extrapolated to women,” he said.

Doctors have long been aware of that differences between ethnic groups can be significant and Jones said it was logical there should be gender variations as well.

African Americans, for example, do not respond as well to a group of blood pressure pills called angiotensin-converting enzyme (ACE) inhibitors as Caucasians.

At the same time, scientists are starting to unscramble some fundamental genetic differences between the sexes.

A team at the University of California Los Angeles published results of a study on mice last year showing how thousands of genes behave differently in the same organs of males and females, and scientists believe the same is almost certainly true of humans.