Statistics
Descriptive results are displayed as mean±SEM or median (interquartile range) for continuous variables, according to the normality of the distributions. Categorical data are described as number (percentage). Continuous variables were compared using the paired Student t-test. Receiver operating characteristic (ROC) curves were constructed to determine the cut-off value, sensitivity (Se), and specificity (Spe) of the delta PR interval. Two-sided p values <0.05 were considered statistically significant. Statistical analyses were performed using SPSS Inc. Released 2007. SPSS for Windows, Version 16.0. Chicago, SPSS Inc.