Quantification of epicardial adipose tissue: correlation of surface area and volume measurements.

OBJECTIVES

Epicardial adipose tissue (EAT) is an important structure both as an active secretor of hormones and cytokines that play a role in the development of atherosclerosis, as well as its potential as a cardiac risk marker. The purpose of this article was to determine an easy but accurate quantification of EAT for routine clinical use.

METHODS AND RESULTS

We randomly selected coronary computed tomography angiographies of 60 patients (20 lean, 20 overweight, and 20 obese) derived from a larger study. Systolic and diastolic surface areas (SAs) were measured at two axial levels: a) fat pocket (FP) between right atrium and right ventricular outflow tract at origin of right coronary artery (RCA-FP) and b) FP anterior to right ventricular free wall (RVFW-FP) at coronary sinus ostium level. Maximum RVFW-FP thickness and total diastolic EAT volume were measured. EAT SA and thickness measurements were correlated to EAT volume and compared. Both interobserver and intraobserver reliability were assessed for SA and thickness with the intraclass correlation coefficient (ICC) as well as mean relative difference ± standard deviation (SD). Differences between systolic and diastolic SA measurements were also evaluated. Diastolic RCA-FP showed the highest SA correlation with volume (ρ = 0.92) and compared to the correlation of EAT thickness with volume (ρ=0.59) demonstrated the largest difference in correlation (+ 0.33, P < .0001). Systolic RCA-FP, systolic RVFW-FP, and diastolic RVFW-FP correlations to volume were less than diastolic RCA-FP (ρ = 0.84, ρ = 0.82, ρ = 0.86 respectively), but all correlations were statistically significantly higher than EAT thickness with volume. Values of systolic SA were mildly higher than diastolic SA for the RCA-FP (relative difference ± SD = 1.8 ± 21%, P = .8), but significantly higher for the RVFW-FP (relative difference ± SD = 17 ± 35%, P < .0001). Both systolic and diastolic SA measurements showed excellent reproducibility (ICC >0.95). However, for EAT thickness, the inter-observer reliability was comparatively low (ICC = 0.66).

CONCLUSION

Diastolic RCA-FP SA is a quick, reproducible estimate of total EAT and compared to EAT thickness demonstrates a significantly better correlation with EAT volume.