In the study of 301 patients, 64% of African-American patients had this unstable plaque, compared with 41% of Caucasians (p < 0.001).
African-Americans also had less calcified plaque than whites, reported John Nance Jr., MD, a researcher in the department of radiology and radiological sciences at the Medical University of South Carolina in Charleston.
"Calcium scores of African-Americans may under-represent the true extent of atherosclerotic disease," Nance told a news briefing.
Population-based studies consistently demonstrate lower burdens of coronary calcification among blacks, despite an increased risk of cardiovascular events. It's been hypothesized that the increased risk is due to an abundance of noncalcified plaque, which has been shown to be more likely to rupture than stable, calcified disease, he said.
The new study involved patients who underwent noncontrast calcium scoring and contrast-enhanced coronary CT angiography for acute chest pain (33% male; mean age, 55) at the medical center. One hundred and fifty of the subjects were African-American.
Among the findings:
- Caucasian patients were significantly more likely to have calcified plaque than blacks, at 45% versus 26% (p = 0.001).
- African-Americans had an increased noncalcified plaque volume compared to whites (median 2.2 mL versus 1.4 mL, p < 0.001).
- In a multivariate analysis adjusted for diabetes, high cholesterol, body mass index, and other risk factors, African-Americans were 2.45 times more likely to have noncalcified plaque than Caucasians (95% confidence interval: 1.52-4.04).
"Not all plaque is created equal," Nance said.
While an abundance of noncalcified plaque may help explain why blacks have a higher burden of cardiovascular disease despite lower coronary calcium scores, the reasons are unclear, he said.
African-Americans have lower rates of osteoporosis, Nance said, adding that different ethnicities have different rates of calcium metabolism.
Calcium metabolism "could play some role," he said.
The findings imply that patients who have more of these soft plaques should be aggressively treated with lifestyle and dietary modifications, lipid-lowering drugs, and blood pressure medications.
Asked to comment on the findings, David Hovsepian, MD, chief of interventional radiology at Stanford University Medical Center in Stanford, CA, called for prospective controlled trials.
Atherosclerosis is "not just about calcium. Coronary calcium can underestimate the burden of disease," he said.
By Charlene Laino
AuntMinnie.com staff writer
December 1, 2010
Left ventricular mass associated with stroke risk in African Americans, October 9, 2007
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