As if the lung damage from COVID-19 wasn’t enough to worry us, doctors have noticed another potential hit from the virus: it could lead to vascular problems.

“We have definitely seen more cases of venous blood clots in COVID patients,” said Gregory G. Salzler, vascular surgery at Geisinger Medical Center. “And we have seen the number of patients that have had clots in their arteries in the setting of COVID, as well.”

“It’s been clearly obvious as this COVID pandemic has gotten started that we were very early on seeing an increase in people who were having thrombogenic events, or blood clotting in places where it ought not to be,” agreed Dr. J. Franklin Oakes, vascular surgeon, UPMC Williamsport. “People coming in with their limbs cold. People coming in with blood clots or strokes or heart attacks. Along with all the other things that happen with COVID, we just noticed these cases were happening more.”

Vascular problems related to COVID-19 are not restricted to older patients.

“I’ve seen a significant uptick in young people with DVT (deep vein thrombosis) who were COVID patients,” said Benjamin Keyser, DO, vascular surgeon at the Heart and Vascular Center of Evangelical. “A lot of them were in their 30s and 40s.”

One question medical researchers are trying to answer is, is it COVID or is it numbers?

“Because the COVID virus has made so many people so critically ill, it’s not clear whether the disease itself is causing the problem. Or just the mere fact that so many people have significant illness and then they’re a lot more likely to have blood clots,” Oakes said.

COVID-19 promotes a very intense inflammation reaction in some patients, Salzler said, especially in severe cases although sometimes also in more mild cases.

“That process in and of itself can cause the blood to become more sticky and form clots,” he said. “And these can be in both the veins and in the arteries.”

Venous clots are what most people commonly think of, clots that form in veins in the leg and cause swelling. Patients typically end up needing blood thinning medication. The biggest fear is that the clot will break off and travel to the lungs, causing a pulmonary embolism.

Clots in the arteries are a little less common but tend to cause more severe problems, depending on which artery is involved, Salzler said. A clot in an artery going to the brain can cause a stroke. Clots in arteries going to the intestines or kidneys can cause severe kidney malfunction or issues with the intestines. Clots going to an arm or leg cause severe pain and can lead to muscles dying and requiring amputation.

“These tend to be surgical emergencies where we need to get those clots out as soon as possible,” Salzler said.

“This is a very different virus from what we are used to dealing with,” Keyser said, adding that while the mortality rate for COVID-19, at about one percent, is lower than originally thought, “that doesn’t account for the problems people can have from COVID”

Those problems can include stroke, heart attack and limb ischemia, or a clot in the arm or leg that can lead to amputation if not handled quickly. Keyser mentioned a COVID patient who has needed three surgeries to save his leg and is still dealing with numbness in his foot.

“It’s important to know these things are happening,” he said.

COVID-19 and the vascular system

Research is not clear on exactly how COVID-19 has affected the vascular system, but doctors know that any critical illness increases the risk for thrombogenic events, Oakes said.

“It’s the immune response,” he said. “It’s the inflammatory response. It’s the nature of being ill and all the war machinery that your body brings to the table to try to combat that illness that then sometimes puts you at risk for a blood clot in one place or another.”

A combination of three factors can lead to blood clotting, Salzler said. They are:

- immobility

- injury to the blood vessel itself

- hypercoagulability, or the propensity to form clots or make your blood stickier—an inflammatory reaction to COVID, for example, can cause blood to be a little more sticky.

Beyond the body’s immune response and the three factors that can lead to clotting, research is being done to see if COVID-19 directly injures blood vessels.

“There is actually evidence that some of the receptors on the cell walls are potentially damaged by COVID directly, as well, which could be a factor,” Salzler said.

Keyser noted that inflammation of the lining of the blood vessels is unique to COVID-19 and is not found in flu cases.

“Autopsies on COVID patients have shown significant evidence of inflammation of the lining of the arteries,” he said. “They’ve found viral DNA in those cells.”

How to avoid blood clots due to COVID

When asked how to avoid blood clots due to COVID-19, Dr. Salzler had to chuckle as he said, “The best way to avoid any complications of COVID is to not get COVID.”

Thus, the usual suggestions of social distancing, hand washing and mask wearing remain important.

“We know what we need to do to prevent this,” Keyser said. “There is a 75-percent risk reduction for COVID with a mask that is worn correctly.”

If despite your best efforts you do get COVID, be as active as possible. When a person lies inactive in bed for a prolonged time, blood does not flow as it normally does and tends to pool in the legs and pelvis, Keyser said. When blood doesn’t move, it tends to clot.

“So if you do get sick, try to get up and walk around and move your legs around a little bit,” Salzler said. “Keep the blood flowing so your blood is not pooling and may have less propensity to forming clots.”

Moving around is necessary even though it might be the last thing an ill person wants to do.

“Just getting out of bed can be a challenge,” Keyser said. “But it’s critical.”

Another preventive measure? An aspirin a day.

“It’s reasonable to think it might help,” Keyser said. “It’s a mild blood thinner. It can reduce inflammation in the walls of the arteries.”

Beyond that, it helps to avoid blood clots just by being as healthy as possible.

“The things we as vascular surgeons want people to do all the time is reduce their risk,” Oakes said. “My mother would say, do the stuff you’re supposed to do. Don’t do the stuff you’re not supposed to do.”

Watch your blood pressure. Take the medications that keep diabetes under control. Eat correctly. Try not to be sedentary or overweight. Don’t smoke.

“I really encourage people to get the vaccine,” Keyser said, noting that 45 million people have been vaccinated so far, with no major side effects. “The faster we can get people vaccinated, the less chance this virus has of mutating.”

“If you do have swelling in an arm or leg that is unexplained, or pain symptoms or other symptoms that aren’t explained, reach out to your health care provider,” Salzler said. “They’ll order appropriate imaging and get you on appropriate therapy.”

It will take years for doctors to have a full understanding of COVID-19 and its long-term risks, Oakes said. In the meantime, continue to focus on the basics.

“Be good. Do good,” he said. “Don’t do stuff that hurts you. Take responsibility for yourself. That’s probably your best risk reduction prescription.”

n Cindy O. Herman lives in Snyder County. Email comments to her at

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