NPPB and atrial fibrillation: Several studies investigated the implications of biomarkers such as TGF-β1, ferritin, PTH, CA – 125, micro RNAs, N-terminal pro-B type natriuretic peptide (NT-proBNP), and b type natriuretic peptide (BNP) as a surrogate marker of fibrosis in AF patients [18–22].