Follistatin-like 3 is Elevated in Patients with Atrial Fibrillation but is Unchanged Following Ablative Therapy

Background: Atrial fibrillation (AF) is a common disorder associated with increased morbidity and mortality. Radiofrequency ablation is a potentially curative treatment option for AF in the recent years. Follistatin-like 3 (FSTL-3) is a secreted protein that has regulatory roles in fibrosis, inflammation and tissue repair and has not been investigated in AF. Atrial fibrosis is involved in the pathogenesis of AF; thus we hypothesised that: 1) AF is associated with elevated FSTL-3, 2) conversion to sinus rhythm following ablation lowers FSTL-3 after 6 months follow-up. Methods/Results: 24 patients with chronic AF (mean age 67 ± 12 yrs), awaiting AF ablation were recruited into the study. FSTL-3 levels were quantitated in stored plasma, using commercially available ELISA (R&D systems). Plasma concentrations of FSTL-3 levels were compared between: 1) AF group vs age-matched heathy control group (n = 79) (mean age 68 ± 6yrs), and 2) in the AF groups before and 6 months after AF ablation. Plasma FSTL-3 levels were significantly higher in the AF groups (mean 7056 ± 557.6 (SEM) pg/mL) vs. the healthy control group (5888 ± 141.7 (SEM) pg/mL) (p < 0.01), but did not change 6 months post ablation (7056 ± 557.6 vs 7541 ± 520.5 (SEM) pg/mL; p = 0.17). Conclusions: In this study, we found that FSTL-3 levels are increased in patients with AF, consistent with the notion that AF is associated with fibrosis and inflammation. However, removing the physical presence of AF with ablation did not change FSTL-3 after 6 months of follow-up. More long-term data and larger studies are required to investigate role of FSTL-3 in atrial fibrosis.