RSNA: CT shows racial differences in CAD

CHICAGO—African-American patients with coronary artery disease (CAD) have much less fat around their hearts compared to Caucasians, researchers reported Nov. 28 at the annual meeting of the Radiological Society of North America (RSNA).

"Prior evidence suggests that increased fat around the heart may be either an independent marker of CAD burden or a predictor of the future risk of acute coronary events," said U. Joseph Schoepf, MD, director of cardiovascular imaging at the Medical University of South Carolina in Charleston.

In 2010, the age-adjusted prevalence of coronary heart disease was 6.5 percent among African-Americans, compared with 5.8 percent among Caucasians.

"You would think that African-Americans, who have a higher prevalence of CAD, would have higher rates of thoracic fat in an acute chest pain setting. However, this was not the case. White patients had significantly higher thoracic fat volumes than African-American patients," Schoepf said in a press release.

The current study was conceived after Schoepf and colleagues reported in 2011 that African-Americans have higher amounts of non-calcified plaque compared to Caucasians. “We didn’t have a way to explain those findings, so we searched for factors to explain those findings,” Schoepf said.

The researchers hypothesized that differences in thoracic adipose tissue between races might be one of the contributing factors, said Paul Apfaltrer, MD, from University Medical Center Mannheim, Heidelberg University, Germany.

Apfaltrer and colleagues evaluated cardiac dual-source CT images of 411 age- and gender-matched African-American and Caucasian patients, quantifying thoracic fat volumes, including epicardial adipose tissue (EAT) and mediastinal adipose tissue. Results showed that while the prevalence of significant stenosis and plaque was similar in African-American and Caucasian patients, African-American patients had less fat around their hearts.

The findings, according to Schoepf and Apfaltrer, are "surprising," given the higher number of cardiac and metabolic disorders among African-Americans despite the presence of less fat in the chest cavity. The researchers suggested that EAT may act as a protective buffer, or that it may be related to plaque maturation including calcification, and could contribute to lower risk of acute coronary events.

“Our finding does not mean that there is not a differential role between races of adipose fat that promotes atherosclerosis. We believe epicardial fat functions in a different way [in African-Americans and Caucasians],” said Schoepf.

The researchers called for additional studies to understand the association between epicardial fat and coronary events. "Understanding the mechanism behind the racial disparities we found may improve the prevention, risk stratification and management of CAD," Schoepf concluded.