<p>Purpose: Epicardial adipose tissue (EAT) is ectopic fat surrounding the coronary arteries. Our previous study reported that EAT in the anterior interventricular groove (EAT-AIG) can be visualized and used as a marker of coronary artery disease. This study was conducted at a single center; thus, it was not a multicenter validation study. Here we conducted a multicenter trial to determine interobserver variability of EAT-AIG measurements.</p><p>Subjects and Methods: To examine the interobserver variability, three sonographers at different cardiovascular hospitals measured the EAT-AIG thickness in 12 volunteers (mean age: 61±22 years, 8 males). The measurement of EAT-AIG thickness was performed using a linear ultrasound probe (Vivid E9). To measure EAT-AIG thickness, we used a modified low parasternal long-axis view. EAT-AIG thickness was measured as the distance from the myocardium to the visceral layer of the epicardium, perpendicular to the pericardium. All sonographers were blinded to each other’s interpretation. We used Bland–Altman analysis and the intraclass correlation coefficient (ICC) to determine the variation of EAT-AIG thicknesses among the three sonographers.</p><p>Results and Discussion: There was a good correlation between all of the measurements. The measurements of EAT-AIG thickness by the three sonographers were highly correlated (ICC: 0.90, 95% confidence interval: 0.78–0.97, p＜0.01). However, we found one case which we determined to be an outlier. The outlier measurement of EAT-AIG thickness was measured in the apical view and not in the modified low parasternal long-axis view.</p><p>Conclusions: Echocardiographic measurements of EAT-AIG thickness significantly varied, with linear measurements showing the least variability among the three sonographers. These findings should considered when evaluating the clinical and scientific significance of longitudinal, repeated measurements of EAT-AIG thickness.</p>