Repaired tetralogy of Fallot: characterization of myocardial fibrosis by magnetic resonance imaging

Despite successful surgery in childhood,1 adults with repaired Tetralogy of Fallot (rTOF) remain at risk of late morbidity and premature mortality, predominantly related to heart failure and arrhythmias. Pulmonary regurgitation (PR) drives adverse ventricular remodelling, with pulmonary valve replacement (PVR) as a cornerstone therapy2 with debated timing in asymptomatic patients. Myocardial fibrosis (MF) has emerged as a central substrate of adverse remodelling in congenital heart disease, including rTOF.3 Cardiac magnetic resonance (CMR) enables tissue characterization, distinguishing focal replacement fibrosis by late gadolinium enhancement (LGE) from diffuse myocardial fibrosis (DMF) assessed by mapping techniques. While focal fibrosis has been associated with adverse outcomes in rTOF,4 data on DMF remain limited.5–7 This study aimed to characterize MF in a large multicentre cohort of adults with rTOF, focusing on CMR derived measures of diffuse and focal fibrosis, and also analysing circulating biomarkers of MF. This was a prospective cross-sectional study that included adults (≥18 years) with rTOF recruited at seven tertiary adult congenital heart disease centres in Spain from June 2018 to March 2022. All participants underwent CMR and blood sampling according to the study protocol. Conditions known to influence collagen turnover were excluded. All imaging and biomarker analyses were centrally performed to ensure methodological consistency.