2-6 Statistical analysis
Descriptive statistics were reported as mean (± SD) or median
(interquartile range) values for continuous variables, and as frequency
(percentage) for the categorical variables. To compare continuous
variables between two groups, the independent t-test or Mann-Whitney U
test was used. The categorical variables were compared between groups
using the chi-squared test. Friedman test was used to compare the
distributions of 3 or more dependent variables. Multivariate analysis
was conducted to identify the predictors of study endpoints by including
significant covariates (i.e., age, sex, atrial fibrillation, admission
INR, functional class, size of thrombus, elapsed time since valve
surgery, redo-operation, recurrent episodes, and treatment types) into
multiple logistic regression analyses. The survival plot and freedom
from recurrence were estimated using the Kaplan-Meier method. The p
<0.05 was considered statistically significant. All
statistical analyses were performed using the SPSS version 21 (IBM,
Armonk, NY).