The extent and significance of cardiac remodeling in Fontan patients are unclear. The aim of this study was to measure myocardial fibrosis in single ventricle (SV) and to determine its relationship with Fontan failure.

A prospective cross-sectional study was performed in 25 patients (mean age 32±9 years, 48% male) with SV. Echocardiography, cardiopulmonary exercise test, BNP measurement and cardiac magnetic resonance imaging (CMR) were performed within the same day. Assessment of late gadolinium enhancement in combination with T1 mapping to quantify diffuse myocardial fibrosis with assessment of myocardial extracellular volume (ECV) were performed. Associations between parameters of SV remodeling, BNP and exercise performances were evaluated.

Ten patients (40%) showed clinical signs of Fontan failure. SV volumes and mass were significantly increased in these patients compared to asymptomatic patients (P<0.01), while there was no difference in SV ejection fraction. Compared to asymptomatic Fontan patients, those with failing Fontan had significantly higher native T1 (1030±29ms vs. 982±25ms, P<0.001) and ECV (32% (interquartile range (IQR) 30–36) vs. 27% IQR [25–30], P=0.002). Amongst CMR parameters, only native T1 was significantly correlated with the peak VO2 [r=−0.49, P=0.017] and BNP (r=0.41, P=0.046). No association was observed with echocardiographic parameters of SV systolic and diastolic function.

Diffuse myocardial fibrosis is a determinant of Fontan circulation failure independently of systolic ventricular function.