Description of included studies
The flow diagram of study selection is shown in Figure 1. Through an
electronic search of three databases (PUBMED, EMBASE and CENTRAL) by
keywords, 4317 citations were screened after 505 duplicates removed.
Full-text review was performed in 47 studies, of which 26 studies did
not meet the inclusion criteria and leaving 21 studies in the final
qualitative and quantitative analysis.
The baseline characteristic of individual studies and patients are
presented in Table 1 and Supplementary Table 1, respectively. In
consideration of different studies from the same research team or
database reporting various endpoints, we selected one with largest
sample size and calculated that a total of 69919 patients were included
in this meta-analysis, and the mean follow-up duration varied from 1.8
to 5 years. All studies included were observational design, in which 5
studies were prospective and the others were retrospective. The majority
of included studies are from centers in European and the USA, and all
patients have received CRT-P or CRT-D between 1999-2017. Trials were
quite variable in association with sample size. The smallest of the
studies included only 135 subjects, and the largest trial enrolled 50084
subjects.
Of those included studies, 17 of them reported adjusted HR of all-cause
mortality [6,8-10,12-14,16,17,19-27], and 4 studies reported HRs
after propensity score matching [8,14,17,19]. Adjusted covariates of
each studies are listed in Supplementary Table 2. CRT-D implantation as
a primary prevention therapy for sudden-cardiac death was clearly stated
in 5 studies [6,12,14,19,25]. We assessed the quality of studies by
using NOS, and only four studies had a score of ≥7 (Supplementary Table
3). Meanwhile, we pooled adjusted HR of all-cause mortality in patients
with NICM, ICM and older age (≥75 years) to explore the optimal
selection of individual device.