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.
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.