By Mike Moffitt, SFGATE
Published
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This test tube contains a blood sample from a patient who tested positive for the COVID-19 coronavirus at Amphia Hospital in Breda, Netherlands. As of March 20, the hospital was carrying out between 400 and 500 tests a day for suspected cases of the virus. less
This test tube contains a blood sample from a patient who tested positive for the COVID-19 coronavirus at Amphia Hospital in Breda, Netherlands. As of March 20, the hospital was carrying out between 400 and 500 … more
Photo: CBSI/CNET
This test tube contains a blood sample from a patient who tested positive for the COVID-19 coronavirus at Amphia Hospital in Breda, Netherlands. As of March 20, the hospital was carrying out between 400 and 500 tests a day for suspected cases of the virus. less
This test tube contains a blood sample from a patient who tested positive for the COVID-19 coronavirus at Amphia Hospital in Breda, Netherlands. As of March 20, the hospital was carrying out between 400 and 500 … more
Photo: CBSI/CNET
Physicians have known for weeks about a vexing complication of COVID-19 — patients are overwhelmed by an onslaught of blood clots. Studies in the Netherlands and France conclude that 20 to 30 percent experience clotting issues.
“This is like a storm of blood clots,” Behnood Bikdeli, a fourth-year cardiology fellow at Columbia University in New York City, told the journal Nature.
Some clots are pudding-like globs of cells and proteins that can cause strokes when they reach the brain. Others are so tiny they can clog up capillaries. Blood thinners don’t seem to work.
Scientists are just now beginning to unravel the mystery of these clots. Here are some of the theories so far, according to Nature:
—A protein fragment known as D-dimer, which is produced when a clot dissolves, may be a predictor of mortality in hospitalized COVID-19 patients. Those experiencing a spike in D-dimer levels were less likely to survive.
—Studies by the Weill Cornell Medicine in New York City and the Irish Centre for Vascular Biology at the Royal College of Surgeons in Dublin found capillaries clogged with clots in lung and skin samples. Patients may be suffering a double whammy: pneumonia gums up the tiny sacs in the lungs with fluid and pus, meanwhile microclots jam the capillaries, blocking the flow of oxygenated blood.
The phenomenon may explain why some patients have critically low blood-oxygen deficits and why machine ventilation frequently doesn’t work.
— Why does this mass clotting happen in the first place? We know SARS-CoV-2 attacks ACE2 receptor cells, which are the pathway for the virus to enter the lungs. But since the endothelial cells that line blood vessels also have these same ACE2 receptors, they may also be targeted. The invading pathogens could be compromising a key function of the lining that prevents clots from forming.
—The tendency of the immune system to go into overdrive in some people while fighting the virus, causing a “cytokine storm,” may be linked to a defense mechanism that triggers coagulation and clotting.
Agnes Lee, director of the Hematology Research Program at the University of British Columbia in Vancouver, noted that many COVID-19 patients are already predisposed to excessive clotting by the time they enter the hospital. Obesity, high blood pressure, diabetes, certain medications, immobilization and advanced age all can contribute to the risk of clots forming.
On the other hand, a small number of young COVID-19 patients in their 30s and 40s, who otherwise are barely sick, have been suffering severe clot-related strokes. That kind of stroke, which can result in death or severe disability, normally occurs in people in their 70s (the median age is 74).
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Mike Moffitt is an SFGATE Digital Reporter. Email: [email protected]. Twitter: @Mike_at_SFGate
