Asymptomatic deep vein thromboses in prolonged hospitalized COVID-19 patients

High incidence of venous thromboembolic (VTE) events in coronavirus disease 2019 (COVID-19) patients has been reported despite pharmacologic thromboprophylaxis. We performed prospective bilateral lower extremity ultrasound evaluation of prolonged hospitalized COVID-19 ward patients from our institution without clinical suspicion of deep vein thrombosis (DVT). A total of 102 patient were included in the study. All patients were receiving pharmacologic thromboprophylaxis, the majority in intermediate or therapeutic doses. Asymptomatic DVT was detected in 26/102 (25.5%) patients: 22 had distal and four had proximal DVT, six had bilateral leg involvement. Pulmonary embolism was highly prevalent (17/70, 24.3%) but similarly grouped among patients with and without asymptomatic DVT. In total 37.2% of patients included in the study were recognized as having VTE. Asymptomatic DVT events were more common in intensive care unit (ICU) survivors (60% in postmechanically ventilated ICU survivors, 21.2% in ward patients, 22% in high-flow oxygen treated patients; P = 0.031), in patients with higher modified International Medical Prevention Registry on Venous Thromboembolism (IMPROVE) VTE risk-score (median 3 vs. 2 points with and without DVT; P = 0.021) and higher body temperature on admission (median 38.7 °C vs. 37.7 °C with and without DVT; P = 0.001). No clear associations with Padua VTE risk score, demographic and other clinical characteristics, intensity of thromboprophylaxis, severity of other COVID-19 symptoms, degree of systemic inflammation or D‑dimers on admission were found (P > 0.05 for all analyses). Systematic ultrasound assessment in prolonged hospitalized severe COVID-19 patients prior to hospital discharge is needed, especially in ICU survivors, to timely recognize and appropriately treat patients with asymptomatic DVT.