FGF23 and atrial fibrillation: Accordingly, at baseline, both serum NT-proBNP levels (525 pg/ml versus 220 pg/ml, respectively) and median plasma FGF23 (64.5 RU/ml versus 38.6 RU/ml, respectively) were higher in our cohort compared with the cohort studied by Seiler et al. Although we were unable to confirm an association between FGF23 and impaired cardiac function, we observed a significant association between FGF23 and atrial fibrillation, as Seiler et al. recently reported [19].