CHICAGO -- African-American patients appear to have more noncalcified plaques -- soft plaques more likely to rupture and lead to heart attacks -- in their coronary arteries than do Caucasians, researchers reported here.
A population-based study of more than 300 patients found that on CT angiography, blacks had significantly more of this unstable plaque than did whites (64% versus 41%, P<0.001), according to John Nance, Jr., MD, of the Medical University of South Carolina in Charleston.
The study also found that blacks also had less calcified plaques compared with whites, so "the calcium scores of African Americans may under-represent the true extent of atherosclerotic disease," Nance said during a press briefing at the annual Radiological Society of North America meeting.
Action Points
- Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
- Point out that this study suggests that noncontrast calcium scoring may significantly underestimate atherosclerotic burden and prognosis in black patients.
Despite typically having lower calcium scores than whites, blacks usually have more clinical disease. Researchers have hypothesized that perhaps they have more noncalcified plaque, which has been shown to be "more likely to rupture than stable, calcified disease," Nance said.
So Nance and colleagues conducted a retrospective study of 301 patients (50% of whom were black) with a mean age of 55, who'd had both calcium scoring and contrast-enhanced CT angiography at the medical center.
They found that African-American patients had a significantly higher prevalence of noncalcified plaques compared with white patients (64% versus 41%, P<0.001).
In contrast, white patients had a significantly higher prevalence of calcified plaques (45% versus 26%, P=0.001).
Blacks also had an increased volume of noncalcified plaque compared with whites (median 2.2 mL versus 1.4 mL, P<0.001).
In a multivariate analysis controlling for diabetes, high cholesterol, and body mass index (BMI), and other risk factors, the relationship remained, showing a 2.45-fold increased risk of a higher noncalcified plaque burden (95% CI 1.52 to 4.04).
"Not all plaque is created equal," Nance remarked. "Noncalcified plaque has been shown to be more vulnerable to rupture."
That could help explain why blacks have a higher burden of cardiovascular disease -- despite having lower coronary calcium scores, but the reasons for this are still unclear, said Nance.
He added that different ethnicities have been shown to have different calcium metabolism, and African Americans are known to have lower rates of osteoporosis. "Calcium metabolism is a dynamic thing, so it could play some role," he commented.
The current 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.
David Hovsepian, MD, of Stanford University, said that the findings are preliminary but still important.
"I don't think any of us would have expected these groups to separate out so well," he told ľֱ. "Using coronary calcium can underestimate the real burden of disease."
Indeed, researchers are still trying to figure out "what to do with calcium screening," Hovsepian said, explaining that newer techniques are revealing that atherosclerotic disease risk is "not just about calcium."
"This opens the door for further research," and prospective controlled trials are needed, Hovsepian added.
Disclosures
Nance reported no conflicts of interest.
A co-author reported relationships with Bracco, GE, Bayer, and Siemens.
Primary Source
Radiological Society of North America
Source Reference: Nance JW, et al "Coronary artery plaque characterization by computed tomography in black and white patients with acute chest pain" RSNA 2010; Abstract VA51-07.