Just as arterial calcium predicts coronary artery disease, the presence and extent of fat accumulations around the heart may indicate the presence of atherosclerosis.
Dr. Hwan Seok Yong and colleagues at Korea University Guro Hospital in Seoul have established a correlation for the first time between the presence of pericardial adipose tissue and coronary atherosclerosis in patients with a normal body mass.
Their recent assessment of 558 chest pain patients determined that pericardial fat is closely associated with coronary artery plaque even in patients without a weight problem. The study group was pared down to 165 patients after excluding subjects with a body mass index over 30.
Based on their cardiac CT angiography results, patients were assigned to either atherosclerotic plaque-positive or -negative subgroups, then evaluated according to cardiovascular risk factors: age, sex, body mass, smoking, hypertension, diabetes, dyslipidemia, and history of hypertension medication.
Plaques were evaluated in all epicardial segments of the coronary arteries. Pericardial adipose tissue area at the midventricular level was measured using a semiautomated technique on a workstation.
Yong discovered that the area of pericardial adipose tissue is significantly larger among patients who are positive for coronary artery plaque development than in patients whose CT scans are normal (p = 0.019). The only other statistical correlation for plaque development was body mass index. Yong presented the results at the 2008 RSNA meeting.
Session moderator Dr. Melvin Clouse noted that investigators have assumed that severe coronary plaque accumulations in lean patients are related to insulin resistance.
"It may, indeed, be that pericardial fat is as important as visceral plaque," he said.
He urged Yong to perform another study measuring the relationship among pericardial fat, coronary artery plaque, and insulin levels.
Another study has revealed that patients with stenotic coronary artery disease carry more epicardial and intrathoracic fat than do adults with healthy coronary function.
Dr. Gorka Bastarrika and colleagues working with Dr. Joseph Schoepf at the University of South Carolina evaluated 129 chest pain patients who underwent cardiac dual-source CT and conventional coronary catheterization.
Seventy-eight percent of the patients were male, and 51% were female. Their average age was 60.7 years. The same volumetric CT images that were used to evaluate the coronary arteries were also processed through software to calculate epicardial, intrathoracic, and subcutaneous fat volumes.
Bastarrika found a strong correlation between patients with significant coronary artery disease (at least one instance of greater than 50% stenosis) and relatively high amounts of epicardial fat volume (located between the myocardium and pericardium) or intrathoracic fat volume mainly around the midsection of the body, compared with patients without coronary artery disease. Fat volume also correlated with the amount of coronary calcium and a modified Gensini score of plaque burden. A relationship between subcutaneous fat and coronary artery disease and plaque volume was not established.
The findings illustrate the multifactorial pathogenetic processes that cause atherosclerosis, Schoepf said. Researchers have increasingly accepted the idea that epicardial fat surrounding the coronary arteries exposes the vessels to atherogenic cytokines released by hormone-active brown adipose tissue in the fat.
"These results also further the establishment of epicardial fat as an independent risk marker for coronary artery disease, so that epicardial fat measures, which can be obtained by various imaging modalities, may be useful for even finer risk stratification and thus for more rational and informed selection of the appropriate risk modification strategy," Schoepf said.
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