Predicting Disease by Imaging Fat Layer Around Heart

The size of the layer of fat around the heart can be measured by imaging techniques such as computed tomography (CT) or magnetic resonance imaging (MRI).

The investigators, from Emory University School of Medicine (Atlanta, GA, USA), presented their results from two studies at the American College of Cardiology meeting in Atlanta, GA, USA, in March 2010. "This information may be used as a ‘gate keeper,' in that it could help a cardiologist decide whether a patient should go on to have a nuclear stress test,” said Paolo Raggi, M.D., professor of medicine (cardiology) and radiology and director of Emory's cardiac imaging center.

The first study, presented by cardiology fellow Nikolaos Alexopoulos, M.D., now at the University of Athens (Greece), demonstrated that patients with a larger volume of epicardial adipose tissue tend to have the types of atherosclerotic plaques cardiologists deem most dangerous: noncalcified plaques.

Calcium tends to build up in atherosclerotic plaques. Even though the heart's overall coronary calcium burden is a good predictor of heart disease, calcium in an individual plaque does not necessarily mean imminent trouble, according to Dr. Raggi. Researchers have been learning that noncalcified plaques indicate active buildup in that coronary artery, and studies suggest that the fat around the heart secretes more inflammatory hormones, compared to the fat just under the skin does.

"Release of inflammatory factors from epicardial adipose tissue may be promoting an active atherosclerotic process, and this is indicated by the presence of noncalcified plaques,” Dr. Raggi stated.

Emory researchers examined 214 patients through cardiac CT, and performed coronary artery scoring as well as assessing the patients' epicardial adipose tissue volume and the plaque in their coronary arteries. The epicardial adipose tissue volume was highest in the patients with noncalcified plaques (about 60% more than those with calcified plaques were).

The second study presented by Emory cardiology fellow Matthew Janik, M.D., measured epicardial fat in patients receiving a nuclear stress test. The 382 patients had chest pain but did not have known cardiovascular disease. A nuclear stress test captured signs of inducible ischemia: deficiencies in blood flow in the heart muscle. Here, the researchers found that the presence of ischemia correlated more closely with epicardial adipose tissue volume than with the coronary calcium score.

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Emory University School of Medicine
University of Athens