2.5 Statistical analysis
Sample size calculation was based on the preliminary outcome. In
patients undergoing MIAVR with the conventional technique, the mean (SD)
indexed EOA was 0.89 (0.13) cm2/m2,
which was assessed by echocardiography at 30 days after operation. In
patients assigned to the FLS group, we expected to achieve at least 20%
increase of indexed EOA. For a 2-sided α=0.05 and power of 0.90, 35
patients in each group were required.
Database management and statistical analysis were performed using SPSS
25.0 software (IBM-SPSS Inc, Armonk, NY). Continuous variables were
presented as mean and standard deviation, and categorical variables were
shown as percentage and numbers. Continuous variables were compared
using Student’s t test for normally distributed data and the
Mann-Whitney U test for skewed data.
Categorical variables were compared
by Chi-square or fisher exact test.