Lisette van Dam

Chapter 13 196 Perfusion defect quantification may not only be clinically relevant for initial risk stratification of acute PE, but possibly also for prediction of long-term adverse outcomes. Extensive clot burden and perfusion defects at the moment of a PE diagnosis have been associated with residual perfusion defects and with persistent symptoms. Therefore, we hypothesized that the extent of perfusion defects as measured by CTPP at PE diagnosis would predict persistent symptoms and 3-month adverse outcomes, including recurrent PE, PE-related readmission and all-cause mortality. In Chapter 11 , we showed that PDS on CTPP at initial PE diagnosis was not associated to persistent symptoms nor to any of the three adverse outcomes. Future larger studies are needed to determine the value of CTPP to CTPA for the prognostic management of acute PE patients. The year 2020 was characterized by the coronavirus disease 19 (COVID-19) outbreak which has led to worldwide spreading of a highly infectious respiratory disease caused by a new coronavirus known as SARS-CoV-2. COVID-19 infection has been associated with an increased incidence of VTE and in particular PE. However, the pathogenesis of COVID-19 associated PE is currently not fully understood. It has been suggested that these pulmonary emboli may be the result of in-situ immunothrombosis rather than conventional VTE. This hypothesis was based on the results of autopsy studies in patients with COVID-19 pneumonia showing multiple small thrombi in the alveolar capillaries. To test this hypothesis, we assessed the clinical and CT characteristics of PE in patients with COVID-19 and compared these to the characteristics of PE in patients without COVID-19. In Chapter 12 , we showed that the PE in patients with COVID-19 was less extensive and more located in the peripheral lung segments. Also, the mean RV/LV ratio was lower in COVID-19 patients, as was the prevalence of RV/LV ratio > 1. We therefore concluded that COVID-19 associated PE is indeed different from conventional PE, a finding that could support the in-situ immunothrombosis theory. This also suggests a possible different (prophylactic) anticoagulant strategy in this patient group then the conventional VTE treatment. Future studies to the exact pathophysiology of COVID-19 associated PE and most optimal anticoagulant treatment are needed. FUTURE PERSPECTIVES Major technical advances have been made in the diagnostic imaging of VTE. This has led to an increase in the detection of very small and/or incidental thrombi. The