Statistical analysis
Continuous variables are presented using mean and standard deviation or
median and interquartile range.
Categorical data are presented as
numbers and percentages. Random-effect meta-analysis was performed
because of the observational design of the included studies. HRs and
95%CI adjusted by Cox multivariate analysis was considered the effect
size, which evaluate the risk of all-cause mortality between CRT-D and
CRT-P. Heterogeneity among studies was assessed by the Cochran’s Q test
and was considered significant when P < 0.10. The
I2 statistic was used to evaluate the proportion of
variance caused by heterogeneity in observed variance. Subgroup analyses
were performed in accordance to the differences of follow-up duration,
indication of CRT-D, region of research center and year of publication
between studies. Sensitivity analysis was performed by removing one
study at a time. Publication bias was estimated using funnel plots and
the regression test of Egger or Begg. Statistical analyses were all
performed with STATA 14 (Stata Corp LP, College Station, Texas).