DISCUSSION
A COVID-19 autopsy study revealed pulmonary embolism as a direct cause of death in one third of cases and found unexpected deep venous thrombosis in over 50% cases (6). Severe pro-inflammatory and pro-thrombotic state is a plausible explanation of hypercoagulability associated with COVID-19 infection (7). Endothelial injury is also postulated as a potential cause for in situ thrombosis (8). It is not yet well known how long this hypercoagulable state persists after recovery from COVID-19 infection.
Our patient failed to continue anticoagulation after hospital discharge and developed acute pulmonary embolism with coexistence of thrombus-in-transit 28 days after initial COVID-19 symptom onset. These floating thrombi are in transit from the legs to the pulmonary arteries and hence can embolize at any time, thus necessitating emergency treatment (9). Due to its transient nature, thrombus-in-transit is a rare finding. When the foramen ovale is patent, the floating thrombi may extend through the ‘hole’ and may cause stroke by paradoxical embolism.
As for port-discharge thromboprophylaxis, there is still not enough data on patients who survived severe COVID-19 infection. At this time, the survivors of severe COVID-19 infection are recommended to follow a general guideline (5,10). This case highlights the risk of thromboembolic phenomena for prolonged periods of times after recovering from acute respiratory distress syndrome associated with COVID-19. More data is needed to determine the optimal duration of anticoagulation treatment.