Pediatric Fontan patients are at risk for myocardial fibrotic remodeling and dysfunction.

Background: Patients with single ventricle (SV) circulations are at risk for ventricular dysfunction. This study investigates whether there is evidence of increased myocardial fibrosis and myocardial dysfunction in children after the Fontan operation.

Methods: Consecutive children after the Fontan operation who underwent cardiac magnetic resonance (CMR) T1 relaxometry with a modified look-locker inversion recovery approach were included in this retrospective study. Native T1 times (T1) and extracellular volume fractions (ECV) in the free wall of the dominant ventricle (left, SLV; right, SRV) were compared with controls and correlated with hemodynamic and clinical parameters.

Results: Twenty-one SV patients (9.7±4.6years; 13 SLV; 8 SRV) and 24 healthy control children (13.9±2.6years, p=0.002) were included. T1 and ECV were higher in SRV patients than in controls (1036±46ms vs 974±27ms, p<0.001; 28±4% vs 22±3%, p=0.002) and SLV patients (978±39ms, p=0.002; 23±5%, p=0.012) while there was no difference between SLV patients and controls. Age at bidirectional cavopulmonary connection was correlated with T1 (R=0.55, p=0.015), while systolic blood pressure (R=-0.68, p<0.001) and body weight (R=-0.54, p=0.012) inversely correlated with ECV. T1 negatively correlated with radial and circumferential strain by CMR feature tracking.

Conclusions: Fontan patients with a SRV show increased CMR markers of diffuse myocardial fibrosis, which are associated with decreased myocardial contractility. Whether their increased fibrosis burden conveys a greater risk for long-term complications in this population remains to be investigated.