Microvascular thrombosis is frequent in #COVID19 👉 Using OCT, we documented the presence of microthrombi in pts with CT scan negative for thrombosis ❓What implications of the first in-vivo visualisation of lung #MicroCLOTS? A thread 🧵1/12 🔗 #FOAMcc

2/ A non-negligible part of patients with #COVID19 pneumonia presents high D-dimer level BUT a negative angio-CT for pulmonary embolism 🔸 These patients could present pulmonary microvascular thrombosis, a condition we called #MicroCLOTS in March 2020 🔸

3/ #MicroCLOTS has been proposed as an atypical ARDS working hypothesis with a new mechanism of lung damage in #COVID19 patients: alveolar endothelial damage leading to a progressive endothelial pulmonary syndrome and microvascular thrombosis.

4/ This opened the way to multiple #COVID19 therapeutic intervention (e.g., anticoagulation prophylaxis at emergency department arrival or full anticoagulation in hospitalized patients with or without high D-dimers).

5/ A more sensitive diagnostic technique than the CT scan for the evaluation of small pulmonary arteries could theoretically allow the detection of #MicroCLOTS thus justifying a more potent anticoagulant regimen.

6/ Optical coherence tomography (OCT) is an invasive near-infrared light source-based imaging technique with a resolution of 10–20µm which has shown a good diagnostic properties for pulmonary artery pathologies.

7/ In this paper, we evaluated the presence of microvascular pulmonary thrombosis (#MicroCLOTS) in 13 patients with #COVID19, high D-dimer levels with intravascular optical coherence tomography (OCT) and compared to angio-CT for pulmonary thrombosis.

8/ OCT seems accurate in evaluating the distal pulmonary arteries in hospitalized #COVID19 pts, allowing the first in vivo documentation of distal pulmonary arterial thrombosis (#MicroCLOTS) in patients with negative angio-CT for PE and increased thromboinflammatory markers.

9/ 🔸 In #COVID19 pt with a CT scan negative for pulmonary embolism, OCT detected distal pulmonary thrombus in 44% 🔸 OCT detected distal pulmonary thrombus in all pts with a positive CT scan for PE, even in lung areas where CT scan did not detect any thrombus #MicroCLOTS

10/ These findings confirm the working hypothesis of #MicroCLOTS and reinforce the need for randomized trials evaluating anticoagulant therapy in #COVID19 patients, especially if an increase thromboinflammatory markers is present.

11/ We previously demonstrated that lung thrombosis in #COVID19 patients is not a pulmonary embolism. In COVID-19, there is an almost perfect topographical overlap of filling defects distribution and pneumonia extent.

12/ Also #Alteplase might be of interest to prevent and treat #MicroCLOTS in ARDS.