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.