NPPB and atrial fibrillation: According to the ROC curve analysis, the best threshold values of AF duration, pre-operative serum BNP level, pre-operative heart rate and LAD were 66.5 months (39.7% sensitivity, 89.0% specificity and 55.3% accuracy), 251 pg/ml (60.3% sensitivity, 71.4% specificity and 67.2% accuracy), 82 beats/min (75.1% sensitivity, 81.5% specificity and 75.8% accuracy) and 67.9 mm (31.8% sensitivity, 91.4% specificity and 68.7% accuracy), respectively (Table 3).