NPPB and atrial fibrillation: Multivariate Cox regressions analysis highlighted miR−21 and NT-proBNP as predictive markers for AF (miR−21: hazard ratio (HR) 0.16; 95% confidence interval (CI) 0.04–0.7, p = 0.009; NT-proBNP: HR 1.002 95%CI 1.001–1.004, p = 0.006).