To assess gender differences in coronary plaque composition, researchers found that women presented less coronary segments with calcified and mixed plaque than men and had exhibited lower rates of coronary segments with stenosis equal to or fewer than 70 percent. The study was published in the Feb. 15 issue of the American Journal of Cardiology.

“Coronary atherosclerotic plaque compositions, rather than the plaque size or the degree of coronary artery stenosis, has been shown to be an important determinant of the evolution and disruption of the plaque. The greater coronary artery disease (CAD) event rates in men compared to women could be a result of the differences in coronary plaque burden and composition,” wrote lead author Khurram Nasir, MD, of the Johns Hopkins University School of Medicine in Baltimore, and colleagues.

Nasir and colleagues studied the gender differences of coronary plaque composition using multi-detector CT angiography (CTA) results in 416 patients—36 percent women, 64 percent men—with intermediate or high-risk CAD.

“Understanding the gender differences in plaque characteristics might be vital in understanding the gender-related differences in CAD,” the authors wrote.

While researchers took into account demographic data such as history of hypertension, hyperlipidemia, diabetes, smoking and genetic history of CAD, no significant differences were found in terms of gender, but women were more likely than men to have a history of diabetes and CAD.

After performing a CTA and scoring coronary arteries using a 15-segment American Heart Association (AHA) coronary artery classification to evaluate the presence or absence of coronary plaque, researchers found that 51 subjects showed no signs of CAD after multidetector CTA (12 percent). CAD was also completely absent in more women than men--23 percent and 6 percent, respectively.

Of the remaining 365 patients, 17 percent had exclusively noncalcified plaque, 11 percent had calcified plaque and 4 percent exhibited mixed plaque. According to the results, women were less likely than men to have exclusively noncalcified plaque, 13 percent and 27 percent, respectively. In addition, men were more likely to have a combination of plaque subtypes than women, 72 percent and 56 percent, respectively.

“Women overall have less plaque burden and extend previous observations by demonstrating that in the presence of CAD, women have relatively more noncalcified plaques and less calcified and mixed plaques than men,” the authors wrote.

In addition, the study showed women (12 percent) were less likely than men (25 percent) to have at least  one coronary segment with a luminal diameter stenosis less than or equal to 70 percent.

“The potential mechanisms of the presence of a greater proportion of noncalicifed plaque in women are not entirely clear, and additional research is needed to determine whether factors related to endogenous hormonal factors, such as estrogen, might play a role,” Nasir and colleagues wrote.

Also, while researchers found that women had a lower mean number of segments that contained calcified plaques and mixed plaques, there was no similar relationship to noncalcifed plaque.

“The observation in our study that men, who are more likely to experience an acute cardiovascular event, had a greater proportion and burden of mixed plaques compared to women, has strengthened the notion that mixed plaques might be more likely to be associated with an increased risk of cardiovascular events,” the authors said.

Nasir and colleagues acknowledged that study limitations stemmed from not adding asymptomatic subjects to the study mix and not including data on outcomes related to plaque composition to determine which plaque subtypes might be more predictive of events to a specific gender.

The authors concluded that future research must be done to assess whether the “underlying differences in plaque composition might explain that reduced risk of cardiac events in women.”