3.7. Statistical analysis
Categorical values are expressed as absolute values and relative frequencies. Continuous variables are expressed as mean ± SD. Tests for significance were conducted using the unpaired t-test or nonparametric test (Mann-Whitney U-test) for continuous variables and the chi-squared test or Fisher’s exact test for categorical variables. When a continuous LACV significantly differed between the two groups, receiver operating characteristic analysis was performed to delineate the cut-off points. Univariate and multivariate Cox proportional hazard models and logistic regression analyses were used to determine the clinical factors that were associated with AF recurrence and a slow LACV, respectively. Survival rates free from atrial tachyarrhythmias were calculated using the Kaplan–Meier method. Survival curves between groups were compared with the two-sided Mantel–Haenszel (log-rank) test. All statistical analyses were performed using commercial software (SPSS version 25 ®, SPSS, Chicago, IL, USA), and statistical significance was defined as P < 0 .05.