*4.1. Clinical Features and Mortality*

CARDS typically occurs early (usually within 14 days after initial symptoms) in the disease course of COVID-19 with patients becoming critically ill due to the rapid onset of respiratory failure. CARDS is diagnosed when a patient has a confirmed SARS-CoV-2 infection and develops ARDS, according to the Berlin 2012 ARDS diagnostic criteria [15]. These criteria include (1) new or worsening acute respiratory failure within 1 week of a known clinical insult, (2) bilateral opacities, not fully explained by effusions, lobar/lung collapse, or nodules, and (3) respiratory failure not fully explained by cardiac failure or fluid overload.

Compared to ARDS from other causes, CARDS has a worse outcome. Bellani et al. reported hospital mortality in ARDS patients of 34.9% for mild, 40.3% for moderate, and 46.1% for severe ARDS [16]. In CARDS, mortality of 52.4% has been reported [17].

## *4.2. Risk Factors*

Risk factors for the development of CARDS and progression from CARDS to death included older age, neutrophilia, organ, and coagulation dysfunction (e.g., higher lactate dehydrogenase and D-dimer) [17]. High fever (≥39 ◦C) was associated with a higher likelihood of CARDS development but a lower likelihood of death [17]. Treatment with methylprednisolone decreased the risk of death [17]. The main causes of death in CARDS are respiratory failure (53%) followed by combined respiratory and cardiac failure (33%), while myocardial damage and circulatory failure were shown in 7% of patients [17].
