TUESDAY, July 1 (HealthDay News) -- Contradicting some earlier reports, a new study finds that women who have heart attacks benefit as much as men from the artery-opening procedure called catheterization.

But that benefit is seen only in women whose heart damage is severe enough to be classified as a heart attack, said study author Dr. Michelle O'Donoghue, a member of the TIMI Research Group at Brigham and Women's Hospital in Boston. Those who have suffered a "near heart attack" called unstable angina should be given more conservative treatment.

"There are blood tests we routinely give to see whether someone has had a heart attack, permanent damage to the heart muscle," O'Donoghue said. "When the tests are elevated, they indicate a higher risk. There is greater muscle tissue damage and so greater incentive to go to catheterization."

In that procedure, a thin wire with a balloon at its end, the catheter, is threaded to the site of a clot blocking a heart artery. The balloon is then inflated to open the artery and restore blood flow.

Some studies had found greater risk than benefit for women with suspected heart attacks. But this analysis of eight randomized trials including more than 10,000 patients, 30 percent of them women, found an overall benefit for women for whom a heart attack was diagnosed. The report was published in the July 2 issue of the Journal of the American Medical Association.

Women who had catheterization had a 19 percent lower risk of death, heart attack or rehospitalization than those who had drug treatment, the study found. For men, the risk was 27 percent lower with catheter treatment than with conservative therapy.

But the gains for women were concentrated among those whose blood tests did not show severe heart damage. For those women, the preferred strategy is "first maximize medical therapy, then catheterize only if there is ongoing chest pain or positive results on a stress test," O'Donoghue said.

It's not entirely clear why women should differ from men in this particular cardiac problem, she said. One possibility is that women are more likely to have other conditions that complicate the situation, such as diabetes, O'Donoghue said. "Or they may have a different kind of heart disease, one that affects the smaller blood vessels," she said. Catheterization would not open these small vessels.

Whatever the reason, the study provides evidence to support updated guidelines of the American Heart Association and the American College of Cardiology, which recommend a conservative strategy for women with acute coronary syndromes, the formal name for heart attacks and unstable angina, the researchers reported.

The researchers won praise from Dr. Nanette Wenger, a professor of medicine at Emory University who was in the group that updated the American Heart Association guidelines, for their efforts at getting the data.

"Often, gender-specific analysis is not done," Wenger said of the earlier reports. "They were able to get from the principal investigators of these trials some data not reported in the papers. This supports precisely what we said in the guidelines."

"This is more evidence that we can't use a one-style-fits-all approach when it comes to treating patients with acute coronary syndrome," said Dr. Sidney C. Smith, director of the University of North Carolina Center for Cardiovascular Science and Medicine, who also helped update the guidelines. "We have to consider risk as well as gender. This is an important study, and it provides support for the new guidelines."

More information

The details of catheterization are explained by the American Heart Association.