FNDC5 and atrial fibrillation: Moreover, the predictive ability of lower levels of irisin regarding poor glycemic control was higher than that of NT-proBNP and had value independent from other parameters including several clinical characteristics (NYHA class III vs. NYHA class I/II), the presence of HFrEF or AF, LVEF, diastolic filling abnormalities and other biomarkers (the HOMA index).