Fat around the heart is significantly associated with CHD risk; the association is independent of conventional risk factors, a case-cohort study has shown. It is a more accurate predictor than other measures of obesity such as BMI and waist circumference.

A total of 998 patients, randomly selected from 6,814 MESA (multi-ethnic study of atherosclerosis) participants who had no history of cardiovascular disease along with 147 MESA participants (26 from those 998 individuals) who developed incident CHD, were studied from 2000 to 2005. The volume of pericardial fat was determined from cardiac CT at baseline.

The presence of pericardial fat was positively correlated with both BMI (correlation coefficient=0.45, p < 0.0001) and waist circumference (correlation coefficient=0.57, p < 0.0001). However, pericardial fat was significantly associated with risk of CHD whereas BMI was not. Waist circumference was weakly associated with risk of CHD. This relationship was not altered by adjustment for other cardiovascular risk factors nor did it differ between the sexes.

Visceral fat has been thought to be a more accurate predictor of cardiovascular and metabolic risk than BMI. This has led to greater attention to waist:hip ratios and the recognition that this is a better marker of obesity than BMI. The MESA study has added further support to this notion. In this study pericardial fat was found to predict future coronary events. Such fat stores may release inflammatory cytokines, which are directly involved in the atherosclerotic process.

What we don't know from this study is the amount of pericardial fat that is associated with excess cardiovascular risk and the amount that can be regarded as normal.

Furthermore, routine measurement of pericardial fat by CT scanning is hardly feasible for cardiovascular risk estimation. Echo can also be used to estimate the degree of pericardial fat and is more readily available than CT. However, I would not advise referring patients for echo simply to estimate pericardial fat but if an echo is being performed for another indication then mention of pericardial adipose in echo reports may give additional information about cardiovascular risk.