BRIEF REPORT Cardiac arrhythmias in patients hospitalized with COVID-19: The ACOVID study Bochra Zareini, MD, PhD,* Deepthi Rajan, BMSc,* Mohammed El-Sheikh, BMSc,* Mads Hashiba Jensen, BMSc,* Mats Christian Højbjerg Lassen, MD,* Kristoffer Skaarup, BMSc,* Morten Lock Hansen, MD, PhD,* Tor Biering-Sørensen, MD, PhD, MPH,* xx Reza Jabbari, MD, PhD, † Ole Kirk, MD, DMSc, ‡ Jakob Tfelt-Hansen, MD, DMSc, † Olav Wendelboe Nielsen, MD, PhD, DMSc, x Birgitte Lindegaard, MD, PhD, k Niels Tønder, MD, DMSc, { Lars Kliesch Pedersen, MD, PhD, # Charlotte Suppli Ulrik, MD, DMSc,** Peter Ellekvist, MD, †† Jens Ulrik Stæhr Jensen, MD, PhD, †† Morten Schou, MD, PhD,* Gunnar Gislason, MD, PhD,* ‡‡ Morten Lamberts, MD, PhD* From the *Department of Cardiology, Herlev and Gentofte Hospital, Herlev, Denmark, † Department of Cardiology, Rigshospitalet, Copenhagen, Denmark, ‡ Department of Infectious Diseases, Rigshospitalet, Copenhagen, Denmark, x Department of Cardiology, Bispebjerg-Frederiksberg Hospital, Copenhagen, Denmark, k Department of Pulmonary and Infectious Diseases, North Zealand Hospital, Hillerød, Denmark, { Department of Cardiology, North Zealand Hospital, Hillerød, Denmark, # Department of Respiratory Medicine, Bispebjerg-Frederiksberg Hospital, Copenhagen, Denmark, **Department of Clinical Medicine, Hvidovre Hospital, Hvidovre, Denmark, †† Department of Internal Medicine, Herlev and Gentofte Hospital, Copenhagen, Denmark, ‡‡ Danish Heart Association, Copenhagen, Denmark, and xx Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark. Introduction First reports from the initial epicenter of the coronavirus disease 2019 (COVID-19) outbreak in Wuhan, China included case series of rapid clinical deterioration of seem- ingly healthy individuals. 1,2 Based on a cohort of 138 Chinese patients, 16.7% of patients with COVID-19 suffered from unspecified arrhythmias despite cardiac biomarkers be- ing within normal range. In patients admitted to the intensive care unit (ICU), arrhythmias was reported in 44.4% of the patients. But how diagnosis of arrhythmias were made was not clearly specified. 1,3 Regardless of pathophysiological pathways for deterioration, of which proposed mechanisms include myocarditis, depressed cardiac function, worsening of prior cardiovascular disease, or cytokine storm syndrome, 1 phenotypic presentation may be sudden death and arrhyth- mias. 2,4,5 Our main aim was to estimate the type of arrhyth- mias with continuous electrocardiogram (ECG) in patients hospitalized with COVID-19, as well as to describe the following clinical episodes according to arrhythmia presenta- tion: (1) initiation of continuous positive airway pressure and noninvasive ventilation treatment, (2) acute respiratory distress syndrome based on a diagnosis in the patients’ med- ical records, (3) transfer to ICU, (4) in-hospital death, (5) computed tomography scan–verified pulmonary embolism (PE) /deep venous thrombosis (DVT), and (6) discharged alive. Methods The ACOVID (Arrhythmias in hospitalized patients with COVID-19) study is a multicenter prospective cohort study recruiting patients hospitalized with COVID-19 at 6 hospitals in the Greater Copenhagen area. Inclusion criteria were patients hospitalized with laboratory-confirmed test of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and age above 18 years. The exclusion criteria were pregnancy, inability to give informed consent, not willing to participate, and recordings with very high levels of noise (.95%). The study period ran from April 27, 2020 to July 30, 2020. All participants gave written informed consent. The study was conducted in accordance with the second Declaration of Helsinki and approved by the regional ethics committee (registration number: H-20021500) and the Danish Data Protection Agency (registration number: P-2020-384). The study is registered at Clinicaltrials.gov (registration number: NCT04395664). Address reprint requests and correspondence: Dr Bochra Zareini, Depart- ment of Cardiology, Herlev Gentofte, University of Copenhagen, Niels An- dersens vej 65, 2900 Hellerup, Denmark. E-mail address: bochra.zareini. 03@regionh.dk. 2666-5018/© 2021 Heart Rhythm Society. Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). https://doi.org/10.1016/j.hroo.2021.03.008