Statistical analysis
Results are presented as mean with standard deviation, median with
interquartile range or frequency. The mean values were compared using
paired t -test. Analysis of the receiver operating characteristic
curve was used to assess the ability of ΔLVEF during dobutamine infusion
for detecting improvement of post-operative LVEF. The optimal cut-off
point was calculated by determining the ΔLVEF during dobutamine infusion
that provided the greatest sum of sensitivity and specificity. In all
analyses, two-tailed P values of <0.05 were considered
statistically significant. All analyses were performed with R
statistical software (R software, version 3.3.0; R Foundation for
Statistical Computing, Vienna, Austria).