AbstractBackgroundUnexpected high levels of atrial fibrosis are found in individuals with no history of atrial fibrillation (AF). The temporal behavior of atrial fibrosis in this population is still unknown. We sought to investigate the progression and predictors of atrial fibrosis in non‐AF individuals.MethodsNon‐AF individuals at baseline who underwent late gadolinium enhancement magnetic resonance imaging (LGE‐MRI) for assessment of left atrial (LA) fibrosis at least twice were retrospectively included in this study. The incidence of AF was assessed using review of medical records.ResultsIn 42 non‐AF patients (15 females, 65.9 ± 8.6 years old), all patients had a detectable level of LA fibrosis at baseline, ranging from 4.5% to 28.8%, with a mean of 12.9 ± 5.9%. LA fibrosis in the second LGE‐MRI was significantly higher in all patients compared to the first measurement (mean value of 12.9 ± 5.9% vs. 17.34 ± 6.8%; p < .05). Congestive heart failure was a significant clinical predictor of atrial fibrosis progression. The seven patients (16.6%) who developed new‐onset AF during follow‐up showed a significantly higher degree of LA fibrosis on their second MRI, compared to individuals who stayed in sinus rhythm (20.5 ± 6.9% vs. 16.7 ± 6.7%, p < .05).ConclusionAtrial fibrotic remodeling is a dynamic process that is progressively increasing in non‐AF patients, accentuated by congestive heart failure. The higher extent of LA remodeling observed in patients who developed AF could highlight either the fact that AF is an expression of a highly dynamic left atrial substrate, or that remodeling processes are accelerated by AF.