Epicardial and hepatic fat in Fontan patients is associated with ventricular changes on cardiac MRI

Background Epicardial and hepatic fat are suspected to play a role in cardiac remodeling. The primary objective of this study was to identify the cardiac MRI (CMR) parameters that are associated with indexed epicardial fat volume (EFV i ) and hepatic steatosis in patients after the Fontan operation. Methods This was a single-center, retrospective analysis of Fontan patients. Epicardial and subcutaneous fat were analyzed with CMR post-processing software, cvi42 (Circle Cardiovascular Imaging, Calgary, Alberta, Canada). Hepatic steatosis was measured with controlled attenuation parameter (CAP) scores via vibration controlled transient elastography. Results The cohort included 81 patients (64% male, median age 16 years). On univariate analysis, EFV i correlated with BMI (ρ=0.52, p<0.001), age (ρ=0.48, p<0.001), EDV i (ρ=0.40, p<0.001), ventricular mass i (ρ=0.39, p<0.001), subcutaneous fat thickness (ρ=0.31, p<0.01), and inferior vena cava (IVC) flow (ρ=0.31, p<0.05). On multivariable regression analysis, BMI (β 2.16, p<0.001) and EDV i (β 0.30, p<0.001) were independently associated with EFV i (R 2 0.47). Males had higher median CAP scores than females (222 vs 196 dB/m; p<0.05). On univariate analysis, CAP scores correlated with BMI (ρ=0.53, p<0.001), subcutaneous fat thickness (ρ=0.48, p<0.001), age (ρ=0.35, p<0.01), EFV i (ρ=0.34, p<0.01), and IVC flow (ρ=0.29, p=0.02). On multivariable analysis, BMI (β 5.8, p<0.001) was independently associated with CAP scores (R 2 =0.28). There were no significant relationships of EFV i or CAP with adverse clinical events. Conclusion BMI is a strong predictor of hepatic and epicardial fat distribution. Epicardial fat volume is also associated with ventricular dilation and may play a role in adverse cardiac remodeling.