A NOVEL LIVER T1 MAPPING SEQUENCE (PROFIT1): TOWARDS EARLY DETECTION OF FONTAN ASSOCIATED LIVER DISEASE

BACKGROUND The Fontan procedure is the final surgical stage for congenital heart disease (CHD) patients with single ventricles. Systemic venous return is routed directly to the lungs while the ventricle pumps arterial blood to the body. One long-term complication is known as Fontan-associated liver disease (FALD). Liver damage is due to a combination of chronic congestion from increased venous pressures and ischemic damage during the multiple surgeries a single ventricle patient undergoes. Fibrotic myocardial remodeling may further increase backup and contribute to liver pathology. Liver biopsy is the gold standard for diagnosis of FALD but is invasive and may not detect heterogenous disease. MRI T1 mapping (longitudinal relaxation time) of the liver provides quantitative assessment of fluid overload and diffuse fibrosis that may overcome these limitations. Our hypothesis is that liver T1 will be elevated in Fontan patients compared to corrected biventricular CHD and normal controls. METHODS AND RESULTS Cross-sectional cohort study of 33 patients within three cohorts: 11 Fontans, 12 biventricular CHD, and 10 controls with structurally normal hearts. Liver T1 was measured with a new water-specific T1 mapping method (PROFIT1 – Proton Density Fat Fraction Imaging with Water-Specific T1) from three axial slices at the widest dimension of the liver (free-breathing acquisition). Whole-liver average values were calculated, excluding blood vessels. Ventricular volumes and ejection fraction (EF) were calculated from the systemic ventricle. Myocardial native T1 mapping (MOLLI) at a mid-ventricular short axis were quantified in both the septum and free wall of the systemic or dominant ventricle. Cohort means were compared with Kruskal Wallis test and Dunn's posthoc test and association was determined with Spearman correlation coefficient. The Fontan cohort had higher liver T1 (795±59 ms) compared to control (668±62 ms; p=0.002) and CHD (672±54 ms; p=0.0007); control and CHD did not differ (Figure 1A). Fontans also had a significantly lower mean EF compared to CHD and controls (p=0.001); there were no significant differences in myocardial T1 between the 3 groups (Table 1). Liver T1 did, however, correlate with septal myocardial T1 within the whole dataset (Figure 1B; r=0.810; p=0.02); liver T1 did not correlate with EF. CONCLUSION T1 mapping with PROFIT1 appears feasible and discriminates Fontan patients from CHD and control. Furthermore, increased liver T1 also was associated with negative cardiac indicators suggesting an association between liver fibrosis and myocardial fibrosis. PROFIT1 is a fast, patient-friendly approach that may provide an early, non-invasive means to detect FALD.