COVID-19 has been associated with a higher risk of thrombotic events such as DVT and APE (4–6). Some studies propose that thromboembolic events could be secondary to a systemic procoagulant response (excessive inflammation, hypoxia, platelet activation and endothelial dysfunction) to COVID-19 infection (7,8). The frequency of these complications increases in critically ill patients admitted to the ICU (1,2). Consequently, some groups recommend full-dose anticoagulant therapy for patients with unfavorable evolution and the worst prognosis, especially in those with sepsis, elevated levels of D-dimer and disseminated intravascular coagulopathy (3,9). Another study found a lower mortality rate in critically ill patients receiving anticoagulant therapy (10).
In our study, we found an increased incidence of asymptomatic DVT (60.87%), mostly in the infrapopliteal venous system in selected COVID-19 patients (elevated D-dimer and severe respiratory failure). The presence of APE was also documented in the six patients who underwent CTPA. One of the limitations of our study is the lack of CTPA in all patients.
A recent study also found an increased frequency of distal DVT in up to 85% of COVID-19 ICU patients (5). Other multiple studies reported a high incidence of DVT in critically ill COVID-19 patients; one of them found an incidence of 47%, but all critically patients were included, not only the most serious patients (1). In another study, the incidence was 20%, but they did not specify whether asymptomatic patients were also studied (2).
Although our study has limitations, such as a small sample size, the results suggest a higher incidence of asymptomatic DVT in critically ill COVID-19 patients than reported by other studies in non-COVID-19 critically ill patients, where the incidence was approximately 10% (11,12).
There is no consensus on the use of anticoagulant therapy on asymptomatic infrapopliteal DVT in COVID-19 patients because of the lower probability of thrombus migration into the lungs, and some groups prefer expectant management (13), while others propose using anticoagulant therapy (14). The indication of treatment depends on the clinical context of each patient. In our critically ill COVID-19 patients, documenting DVT helped tip the balance to fully anticoagulated patients.
Therefore, we propose the use of bedside ultrasound to detect DVT, including infrapopliteal DVT, especially in ICU patients who cannot be mobilized to perform CTPA.