The study also showed the risk factors that predict whether or not these women are likely to experience future cardiac difficulties differ somewhat from men.
Dr. Michael Shlipak, an assistant professor of medicine, epidemiology and biostatistics at the San Francisco Veteran Affairs Medical Center, says his research team was disappointed but not surprised by the findings.
"It was a minority of women who had adequate treatment," he says. "Prevention is hard because you never see the benefits, but you see the side effects" of the medications the women receive.
For example, only 83 percent of the women in the study were receiving aspirin or other antiplatelet therapy. Many women, particularly older women, experience gastrointestinal bleeding when they take these drugs, which may deter physicians from treating them. "That's the paradox that drives us away from using preventive medicine," Shlipak says.
Other medications that were given too infrequently in this group include beta blockers (33 percent), angiotensin-converting enzyme inhibitors (18 percent), and lipid-lowering drugs (53 percent).
The worst news may be that women identified as being the most ill and high-risk for heart attack or death were also the least likely to be treated to prevent those occurrences, Shlipak adds. "All women with established cardiac disease would benefit from preventive therapy. Women at highest risk tend to be the frailest and the least likely to receive preventive medication."
Women and men with heart disease shared many risk factors for heart attack or cardiovascular death. However, there were some differences, and many ranked differently in how important they were, Shlipak says.
For the study, appearing in the Jan. 21 issue of the Annals of Internal Medicine, the researchers used data from 2,763 postmenopausal women with known heart disease in the Heart and Estrogen/Progestin Replacement Study (HERS). During the average 4.1 years of follow-up, 361 of the women had nonfatal heart attacks or died of coronary heart disease (CHD). Of the 232 women with nonfatal heart attacks, 24 subsequently died of CHD.
The researchers found moderate alcohol consumption and regular exercise were protective, and, surprisingly, age was not a strong predictor of more cardiac trouble.
Nonwhite women with cardiac disease were twice as likely as white women to have a CHD event. The reason for this is not known, Shlipak says.
Other risk factors identified as being predictive of cardiac events included treated diabetes, congestive heart failure, a history of at least two heart attacks and angina. High blood pressure, waist-to-hip ratio, high LDL (the "bad") and low HDL (the "good") cholesterol, and triglyceride levels were also associated with more CHD events.
The more risk factors a woman had, the more likely she was to suffer another cardiac event. The annual rate of coronary events was 1.3 percent in women with no risk factors, but 8.7 percent in women with five or more risk factors.
"The surprising things were the traditional risk factors [for cardiac events in men] were less strongly predictive in this group," Shlipak says. Kidney insufficiency and elevated lipoprotein levels, for instance, were found to be much more relevant for women than for men.
Elevated lipoproteins have not been identified as of primary importance in preventing subsequent cardiac events in men, agrees Dr. Stephen Smith, director of the inpatient cardiovascular clinic at Henry Ford Health Systems in Detroit. However, the most salient point of the study, he says, is the reminder that "it's not always the same risk factors for the same people at the same age."
Smith admits that most physicians probably think they do well even though they could do better. "I think I'll pay more attention to it," he says. "It needs to be in the front of the brain."
It helps if patients know what makes them more likely to suffer future problems so they can talk to their doctor about any concerns, Shlipak adds. "A well-educated patient is great prevention."