Blood clots in the lung may be a major cause of COVID-19 deaths
The major fear of COVID-19 infection is the significant fatality associated with it. Even though death from this infection has been relatively low in India and is <1% in Tamil Nadu, given the very large number of people infected, significant numbers continue to die. Based on the data available so far, it is clear that the cause of death in almost all patients is respiratory failure. What is its cause? Unlike what would be expected in a viral infection in the lungs, it is not the pneumonia itself, like in most previous influenza outbreaks, but rather surprisingly it is early and progressive clotting of blood in the lungs (pulmonary thrombosis) which impairs blood supply and gas exchange leading to respiratory failure. This mechanism is supported by several levels of evidence.
First, it has been recognised from the very early reports that very high proportions of patients with COVID-19 infection presenting to hospitals had elevated levels of d-dimer, a general marker of thrombosis in blood vessels.
Those with highly elevated d-dimer levels were more prone to severe respiratory complications and death. In most of these patients, there are no other sites of thrombosis to explain the raised d-dimer such as the leg veins which is much more common but has only been reported in a few patients late in their illness after they have been in the hospital for several days.
Second, the strongest evidence for this extensive microvascular thrombosis comes from several autopsy studies from different countries. All these have shown extensive blood clots in ...
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