Moreover, serum levels of relaxin-2 were positively correlated with an increase in left atrial diameter, with the risk of HF occurrence and with diverse serum fibrosis-related biomarkers such as TGF-β, procollagen type I C-terminal peptide (PICP), as well as TNF-α, demonstrating a close association between relaxin-2 and the progression of left atrial diameter as well as with fibrotic processes in AF [118]. This evidence concerns the gene RLN2 and atrial fibrillation.