2.1. Study population
After approvals from the local ethics committee (with date 01.02.2021 and number 2021/04-27) and the Turkish Ministry of Health, the retrospective cohort study was conducted in adult ICUs of our center. All adult patients (age ≥ 18 years) diagnosed with COVID-19 infection were included in the study between March 2020 and January 2021. SARS-CoV-2 infection was confirmed by either using reverse transcriptase polymerase chain reaction (RT-PCR) testing on respiratory samples and/or with clinical characteristics, laboratory, and computed tomography findings. The exclusion criteria of the study were having chronic AF diagnosis before COVID-19 diagnosis, presence of cardiac pacemaker/implantable cardioverter-defibrillator, atrial flutter, and NOAF development immediately after cardiopulmonary resuscitation.