Rare but fatal, blood clots are fast emerging as a covid-19 complication

One of the biggest discoveries in our fight against covid-19 has been the slew of new symptoms that the SARS-Cov-2 virus seems to showcase. From breathlessness to loss of smell and taste—these signs have been markers for diagnosis. And now another threat from the virus that has emerged and can cause massive damage is blood clots.

Doctors around the world are noticing clotting-related disorders in covid-19 patients—from benign skin lesions on the feet, referred to as “covid toe” to life-threatening strokes and blood-vessel blockages.

The clotting phenomenon is “probably the most important thing that’s emerged over the last perhaps month or two,” said Mitchell Levy, chief of pulmonary critical care and sleep medicine at the Warren Albert School of Medicine at Brown University in Providence, Rhode Island, US.

Other viral infections also cause clotting
Covid-19 isn’t the only viral infection to increase the risk of blood clots in its patients. The 1918 Spanish flu pandemic, caused by a novel strain of influenza that killed some 50 million people worldwide, was also linked to downstream damage from clots that could end lives dramatically.

Viruses including HIV, dengue, and Ebola are all known to make blood cells prone to clumping. But this pro-clotting effect may be even more pronounced in patients with the coronavirus.

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“There’s something about this virus that’s exaggerated that to the nth degree,” said Levy, who is also medical director of the medical intensive care unit at Rhode Island Hospital. “We’re seeing clotting in a way in this illness that we have not seen in the past.”

Are clots the reason for sudden deterioration in covid-19 patients?
According to Margaret Pisani, an associate professor of medicine at the Yale University School of Medicine in New Haven, Connecticut (US), these clots are

probably the reason why patients who otherwise appear well to suddenly “fall off the ledge” and develop severe blood-oxygen deficiency.

Clotting disorders in covid-19 patients were also noted by researchers in China in February—but their gravity has since become clearer. While doctors had thought the vast majority of lung damage was due to viral pneumonia, they’re now looking more closely at clotting.

Separate studies from France and the Netherlands found that as many as 30% of severely-ill covid-19 patients suffered a pulmonary embolism—a potentially deadly blockage in one of the arteries of the lungs. These often occur when bits of blood clots from veins deep in the legs travel to the lungs. By comparison, the prevalence of pulmonary embolism was just 1.3% in critically ill patients without covid-19, one study found.

Blood clots put overwhelming strain on the heart
If untreated, large arterial lung clots can cause cardiac arrest. Even tiny clots in the capillaries of lung tissue may interrupt blood flow, undermining attempts to help oxygenate patients with ventilators, said Edwin van Beek, chair of clinical radiology at the University of Edinburgh’s Queen’s Medical Research Institute, UK.

Clots can also form in many other parts of the body, potentially damaging vital organs including the heart, kidneys, liver, bowel, and other tissues. In pregnant covid-19 patients, clots may impair blood supply to the foetus, leading to complications associated with miscarriages and low birth weight, doctors in New York reported last month.

Blood clotting might just be a rare complication of covid-19
It’s a rare complication amplified by the “sheer numbers of infected patients,” says Jean Connors, a Harvard Medical School haematologist.

In Italy, the first European country gripped by the pandemic, it was after covid-19 patients died from acute pulmonary emboli and other clotting-related events that doctors moved to inflammation-blocking treatments, said Frank Rasulo, a head of neuro critical care at Spedali Civili University Hospital in Brescia.

Some doctors are starting to see covid-19 as less of a typical respiratory disease, and more of one that involves dangerous clotting, said Rasulo, who is also an associate professor of anesthesia and intensive care. “That’s quite frightening when you think of it, because we didn’t know what we’re up against until we were in a later stage.”

(With inputs from Bloomberg)