Abstract Body (Do not enter title and authors here): Background: Cardiovascular magnetic resonance imaging (CMR) can estimate diffuse myocardial fibrosis using extracellular volume fraction (ECV) quantification.
Objectives: This study aimed to explore associations between and prognostic value of myocardial and hepatic fibrosis after tetralogy of Fallot repair (rTOF).
Methods: Adults with rTOF were prospectively enrolled along with healthy controls. Patients were categorized by hemodynamic load (pulmonary stenosis and/or pulmonary regurgitation). Available clinical data were recorded at study entry. Myocardial and hepatic ECV were calculated from pre/post-contrast T1 maps. The primary outcome was a composite of death, resuscitated sudden death, sustained ventricular tachycardia (VT) or VT requiring invasive therapy, and/or heart failure requiring hospital admission. Multivariable modelling was used to examine the association between CMR measures and adverse cardiovascular events.

Results: We studied n=181 patients (56% male; median age 33 years [IQR 26–47]) and n=20 age/sex-matched controls. Hepatic and myocardial fibrosis measures were correlated (r=0.031, p<0.001). Diffuse hepatic fibrosis was higher in rTOF patients as compared with controls (586±69 versus 531±75 msec, p=0.006) with statistically significant differences between hemodynamic load type (p=0.04). Right ventricular (RV) native T1 in rTOF was increased as compared with controls (1081±76 versus 997±743 msec, p<0.001) with a trend towards significant differences when stratified by hemodynamic load (p=0.09). Late gadolinium enhancement (LGE) was seen in the RV in 46% (n=83) and in the left ventricle (LV) in 37% (n=66). At median follow-up 2.1 years (IQR 0.7-2.7), the composite outcome occurred in 9% (n=17). Independent predictors of adverse cardiovascular events on multivariable models, adjusted for age and sex, were RV end-systolic volume (HR 1.43, 95%CI 1.09-1.99, p=0.02), RV native T1 (HR 1.15, 95%CI 1.07-1.25, p<0.01) and LV LGE (HR 3.15, 95%CI 1.06-10.13, p<0.04); hepatic fibrosis was not associated with outcome.

Conclusion: In rTOF, myocardial and hepatic fibrosis were modestly correlated. As compared with controls, myocardial and hepatic fibrosis was increased in rTOF. Diffuse myocardial fibrosis in the RV (native T1) and replacement fibrosis in the LV (LGE) were independently associated with cardiovascular outcomes, although hepatic fibrosis was not. These findings should be validated in larger populations with longer follow-up.