2.3 Statistical analyses
To evaluate the change in LVEF and QRS duration over time, means, standard deviations, and sample sizes were extracted from articles to estimate the overall average values and confidence intervals (CIs). Statistical heterogeneity was conducted by calculating Higgins I2; I2 >50% was considered to indicate significant heterogeneity.22After confirming heterogeneity, we used a random effects model because the populations included in the individual studies were from different populations.23 Potential publication bias was assessed by visual inspection of the funnel plot and the Egger regression asymmetry test. If the P for bias was >0.05, it was judged that there was no publication bias.24 All tests with P-values <0.05 were considered to be statistically significant. Statistical analyses were performed using R programming version 4.0.3 (The R Foundation for Statistical Computing, Vienna, Austria).