Lisette van Dam

Clinical and CT characteristics of COVID-19 associated PE 12 181 INTRODUCTION COVID-19 infections are associated with frequent activation of the coagulation system. This so-called COVID-19 coagulopathy has been shown to be predictive of poor outcome and excess mortality. 1-6 Moreover, COVID-19 illness is associated with high rates of venous thromboembolism, particularly acute pulmonary embolism (PE). 7-14 This high rate of venous thromboembolic complications is likely related to the COVID-19 coagulopathy, in combination with well-known strong thrombotic risk factors including inflammation, hypoxia and immobilisation, which all become more pronounced in critically ill patients. Based on autopsy studies, it has been proposed that the inflammatory process in the microcirculation of the lung may cause in situ immunothrombosis. 15,16 This suggests an alternative explanation to the conventional thromboembolic pathomechanism of PE. 17 To investigate this hypothesis, we set out to determine the clinical and computed tomography (CT) characteristics of acute PE in COVID-19 patients and compare these to the characteristics of acute PE in patients without COVID-19 pneumonia. METHODS Patients and design We included all adult patients admitted to the Leiden University Medical Center (LUMC) with polymerase chain reaction (PCR) proven COVID-19 infection and computed tomography pulmonary angiography (CTPA) proven acute PE between March 19 th and April 14 th . Additionally, we studied a convenience control cohort, in whom all radiological parameters had been assessed as part of an ongoing observational study. This control group consisted of 100 consecutive adult patients with CTPA confirmed PE, diagnosed between July 2017 and October 2019 in the LUMC, before the COVID-19 outbreak. In both cases and controls, CTPA was ordered only upon clinically suspected PE. In patients not admitted to the intensive care unit (ICU) and with suspected acute PE, the YEARS algorithm was applied and CTPA was performed only if the D-dimer level was above the threshold. 18 In patients admitted to the ICU and with suspected acute PE, CTPA was directly ordered without prior clinical probability scoring and/or D-dimer testing. This study was approved by the Institutional Review Board of the LUMC for observational studies.