Threshold for the Upper Normal Limit of Indexed Epicardial Fat Volume: Derivation in a Healthy Population and Validation in an Outcome-Based Study

Epicardial fat volume (EFV) quantified on noncontrast cardiac computed tomography relates to cardiovascular prognosis. We sought to define the upper normal limit of body surface area (BSA)-indexed EFV (EFVi) in a healthy population and to validate it as a predictor of major adverse cardiovascular events (MACE). We analyzed noncontrast cardiac computed tomography scans of 226 healthy subjects with a low Framingham Risk Score (FRS; <= 6%) performed for coronary calcium scoring (CCS). EFV was quantified using validated software and indexed to BSA. We defined the 95th percentile as the upper normal limit. Subsequently, we reanalyzed a separate cohort of 232 participants from a previously published case-control study with 4-year follow-bp and 58 cases of MACE to test the additive value of an abnormally high EFVi for predicting MACE. Of the 226 healthy participants 51% were men (mean age 52 +/- 9 years). EFV correlated to BSA (r = 0.373, p < 0.0001). Median, range, and 25th and 75th percentiles of the non-normally distributed EFVi were 33.3, 10.8 to 96.6, and 24.5 and 45.5 cm(3)/m(2). The 95th percentile definition of the upper normal limit of EFVi was 68.1 cm(3)/m(2). For prediction of MACE, EFVi values higher than the newly defined threshold emerged as a significant and independent predictor after controlling for confounders (odds ratio 2.8,95% confidence interval 1.3 to 6.4, p = 0.012) and trended in its additive value to the combination of CCS >= 400 and FRS (area under the receiver operating characteristic curve 0.714 vs 0.675, p = 0.1277). In conclusion, in a healthy population we determined 68.1 cm(3)/m(2) as the 95th percentile threshold for abnormally high EFVi. EFVi exceeding this value independently predicted MACE and trended to add to CCS and FRS in this prediction. (C) 2011 Elsevier Inc. All rights reserved. (Am J Cardiol 2011;108:1680-1685)