2.1 Search Strategy
The search was performed using the PubMed, Cochrane and Embase databases
with the start date prior to May 30, 2020. To identify and retrieve all
potentially relevant articles, the search was performed utilizing the
following expression:
[(‘epicardial
adipose tissue’ OR ‘epicardial fat’ OR
‘pericardial
adipose tissue’ OR‘pericardial fat’ OR ‘paracardial adipose tissue’ OR
‘paracardial fat’) AND
(‘atrial
fibrillation’ OR Arrhythmias, Cardiac’)]. Additionally, hand searches
of the reference list of included studies were performed. We conducted
this meta-analysis in accordance with the PRISMA (Preferred Reporting
Items for Systematic Reviews and Meta-Analyses) guidelines. The
systematic review registered in PROSPERO (ID: 219400). As per the
different measuring methods of EAT, eligible studies fall into three
sub-groups, including total EAT volume, EAT thickness and LA-EAT volume.
2.2 Eligibility criteria
Case reports and review articles
were excluded. Only English publications in peer-reviewed journals were
eligible for this meta-analysis if they: (1) reported EAT thickness or
volume with at least one of the following main confounders: age, gender,
hypertension and Body Mass Index
(BMI); (2) reported EAT parameters in two groups of patients with and
without AF occurrence after cardiac surgeries, and 3) measured EAT by
CT, magnetic resonance imaging or echocardiography. The literature
search was independently reviewed by two assessors to ensure full
compliance with the study inclusion criteria. If no agreement could be
reached, it would be decided by a third senior author.
2.3 Study quality assessment
The Strengthening the Reporting of Observational Studies in Epidemiology
(STROBE) Statement 23 was used to evaluate the quality
of the included studies. STROBE consists of 22 items assessing quality
of the information reported in the abstract, including introduction,
study design and setting, statistical evaluation, results, discussion
and findings. The point of STROBE judgment for all included studies was
prepared based on rating scale ranging from 0 to 22 with higher score
resulting in high quality. The STROBE score was independently evaluated
by two investigators. And a third senior author was consulted when there
were discrepancies. In the case of conference abstracts, which are
without full-text, we used another 12-item STROBE checklist. All
quantity scores were included in Table 1.
2.4 Statistical methods
The Cochrane Q test and I squared index were used to evaluate
heterogeneity of individual studies. I2>
50% suggested high heterogeneity. In the case of high heterogeneity, a
random effect model was adopted. Considering the small size of samples,
we used sensitivity analysis to explore probable sources of
heterogeneity. The possibility of publication bias was evaluated through
the Funnel plots and Egger’s regression test.
Statistical analysis was performed
using STATA package vers.16 (StataCorp, College Station, TX, USA).
P<0.05 was considered statistically significant.
3. RESULTS