Study population
We retrospectively analyzed 49 patients with ARDS caused by COVID-19 pneumonia (age ≥18 years) who were admitted to the ICU of the First Affiliated Hospital of Harbin Medical University from February to March 2020. The novel coronavirus nucleic acid test results were positive in all patients. The diagnosis of ARDS was based on the Berlin definition [10]. According to the Guidelines for diagnosis and treatment of novel coronavirus pneumonia (Trial Version 5) [11], all selected patients were divided into severe and critically severe group. Patients with polypnea (respiratory rate ≥ 30 times/min), decreased oxygen saturation (≤ 93% at rest), PaO2/ FiO2≤300mmHg or exacerbation of lung imaging more than 50% within 24-48 hours were classified as severe type, and those with respiratory failure requiring mechanical ventilation, shock or other organ failure were classified as critically severe type. Patients with no echocardiographic windows, or who had congenital heart disease, cardiac valvular disease or acute myocardial infarction were excluded. All 49 patients were enrolled for final analysis, including 35 severe and 14 critically severe cases. Age, gender, underlying disease, APACHE Ⅱ score within 24 hours of hospitalization, heart rate (HR) and mean arterial pressure (MAP) during echocardiographic examination were recorded. Age-matched healthy volunteers (n = 25) were recruited serving as a control group.