FGF23 and cardiac arrhythmia: High FGF23 levels and klotho deficiency are postulated as key risk factors for the development of uremic cardiomyopathy (2, 23, 25, 31, 52) and increase of FGF23 is further associated with poor outcome in patients with heart failure, cardiogenic shock, or arrhythmia at normal kidney function (4–8).