Study selection and quality assessment
Two reviewers (MA and AK) screened independently and blindly the
potential eligibility of each of the abstracts and titles that result
from executing the search strategy using a systematic review software
(Covidence, London, UK). The reviewers evaluated the abstracts for
inclusion and exclusion criteria, in case that all are not disclosed in
abstract methods, the study was classified as potentially eligible and
the complete article was examined to determine inclusion. Subsequently,
disagreements were solved by consensus. Then, both reviewers evaluated
the full text versions of all potentially eligible studies. Inclusion
criteria are: (1) studies contains data of echocardiographic parameters
in two groups; group with sleep apnea disorder and a control group (2)
studies with data of echocardiographic parameters in different groups
with varying sleep apnea severity.
Echocardiographic parameters needed for inclusion were prespecified
according to the update published in 2016 by the American Society of
Echocardiography (ASE) and the European Association of Cardiovascular
Imaging (EACVI) for the evaluation of Left Ventricular Diastolic
Function by Echocardiography(6). Any study with at least one parameter
was included. The parameters commonly found were mitral valve
deceleration time, isovolumic relaxation time, the ratio of early mitral
inflow velocity to mitral annular early diastolic velocity E/e’, left
atrial volume index (> 34 mL/m2), the ratio of early to
late mitral inflow velocities E/A ( > 14), and left
ventricular mass index.
Diagnosis of sleep apnea was considered according to the guidelines of
American Academy of Sleep Medicine Clinical Practice Guideline (7). The
sleep disorder group consisted of symptomatic patients who had an
in-laboratory polysomnography (PSG) or home sleep apnea testing (HSAT)
confirmation of sleep apnea with an apnea hypopnea index (AHI) greater
than 5.