Circ: Women: ST-segment depression & beyond
Compared to men, women with coronary heart disease present differently, have higher mortality rates and undergo fewer tests. "Given these gender differences... critical steps should be taken to identify women at the earliest stage of presentation so that appropriate therapeutic strategies can be implemented," according to research in the Dec. 14 issue of Circulation.

Priya Kohli, MD, from Northwestern University in Evanston, Ill., and Martha Gulati, MD, from Ohio State University in Columbus, Ohio, said that identifying women with coronary artery disease (CAD) can be a diagnostic challenge.

Women tend to present with symptoms and CAD at older ages, their symptoms are more atypical and they have a lower prevalence of obstructive CAD compared with men.

Kohli and Gulati reviewed the literature regarding exercise stress testing in women, with a focus beyond ST-segment depression alone.

While ST-segment depression that occurs with exercise stress testing reflects ischemia, it is considered less accurate in identifying CAD in women than in men, they noted. The sensitivity and specificity for the diagnosis of CAD in women range from 31 to 71 percent and 66 to 86 percent, respectively. The test also has a lower positive predictive value in women, but a similar negative predictive value as in men.

These differences between women and men can be due to women having "baseline ST- and T-wave changes, making interpretation of ECG changes with exercise difficult." In addition, estrogen may account for differences in women.

As women are generally older when presenting for stress testing, a decreased exercise tolerance may limit the ability to accurately identify women with CAD as well.

"Although ST-segment depression with exercise provides some diagnostic information in women, these same ECG changes do not appear to provide strong prognostic value in women," the researchers said.

Several studies, large and small, have not found correlations between ST-segment depression with exercise stress testing and cardiovascular mortality or all-cause mortality.

Kohli and Gulati noted that exercise capacity, an estimate of the maximal oxygen uptake for a given workload (expressed in METs), has been shown to be an independent predictor of the presence of CAD in women.

In some studies, maximal exercise capacity, when added to ST-segment depression, was among the best stress testing variables for predicting the presence of CAD. Those who achieved 10 METs had a very low prevalence of significant ischemia, but those who achieved 7 METs were more likely to have significant ischemia.

Exercise capacity has strong prognostic implications in asymptomatic and symptomatic women as well. In studies, exercise capacity was the only exercise stress testing variable that was an independent predictor of mortality. For every 1-MET increase in exercise capacity, there was a 25 percent reduction in risk of all-cause mortality and a 23 percent reduction in risk of cardiac events for women.

The ability for women to reach heart rate (HR) target has diagnostic and prognostic value. In small studies, the inability to reach 85 percent of the maximum age-predicted HR with exercise was associated with higher likelihood of CAD. In a larger study, Kohli and Gulati pointed out that for every 1-bpm increase in peak HR with exercise achieved, there was a 3 percent reduction in all-cause mortality.

HR recovery also has prognostic value in women, as well as men. In one study, noted by Kohli and Gulati, an abnormal HR recovery – defined as a decrease in the HR of less than 12 bpm in the first minute of recovery – was an independent predictor for all-cause mortality.

Both exercise stress echo and stress SPECT imaging have well-documented limitations in women, including artifacts from breast tissue and/or body habitus. "Despite these limitations, both the diagnostic accuracy and prognostic value of stress SPECT and stress echocardiography exceed those of exercise ECG alone, with no significant differences between men and women," they wrote.

Researchers concluded, "In the current climate of rising healthcare costs, it is important to critically evaluate the manner in which to appropriately use exercise stress testing in women to make accurate diagnostic assessments, reduce radiation exposure, and ensure appropriate allocation of medical resources."