FGFR4 and atrial fibrillation: Higher levels of FGF-23, common in patients with chronic kidney disease (CKD), are associated with a higher incidence of HF and AF, but the exact mechanism is poorly understood.34 It has been proposed that FGF-23 might induce left ventricular hypertrophy (LVH) by activating fibroblast growth factor receptor 4 on cardiac myocytes,35 and that FGF-23 can trigger LVH and a decline in left atrial emptying fraction, irrespective of the left ventricular structure and function in mice.34