Data extraction and quality assessment
All publication pieces of data were extracted: (1) publication
information (the first author’s name, publication year), (2) cohort
demographics (sample size, gender constituent ratio, mean age,
comorbidity), (3) atrial fibrillation (AF) duration, (4) body mass index
(BMI), (5) echocardiographic parameters (left ventricular ejection
fraction (LVEF), (6) left atrial dimension (LAD), (7) procedural data,
including cryoballoon generation (first generation: CB-1, second
generation (advanced): CB-2, third generation (short tip): CB-ST),
balloon dimension (23 or 28mm), balloon location (right superior
pulmonary vein right [RSPV] or inferior pulmonary vein [RIPV]),
time and nadir temperature to rPNI, diaphragmatic protection
(fluoroscopy, palpation, stimulation, including cycle, strength of
impulse, positioning of pacing electrode and CMAP), procedural and
delayed complications of phrenic nerve palsy. Whenever the data of
interest were incomplete, the investigators did not use the study in the
meta-analysis. In some publications, only a selected group was used for
analysis once the same data were found in other publications (example
Aryana 2014 [34], 2015 [6], 2016 [44]; 2014: CB-1/CB-2 2014:
only CB-1 taken from a database; 2015: CB-2 2012-2015.02 CB-2 all taken
from database; 2016: CB-2/CB-ST from 2015.3: all data taken from
database).