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Expert Says There's An 'Incredible Association' Between Blood Clots And COVID-19

A general practitioner shows the information sheet about the risk of blood clots that is given to people who are injected with the AstraZeneca vaccine against COVID-19 during a campaign in Amsterdam, Netherlands, Wednesday, April 14, 2021. (AP Photo/Peter Dejong)
Peter Dejong
AP File
A general practitioner shows the information sheet about the risk of blood clots that is given to people who are injected with the AstraZeneca vaccine against COVID-19 during a campaign in Amsterdam, Netherlands on April 14.

Up to 100,000 Americans die every year due to deep vein thrombosis (DVT) or pulmonary embolism (PE). On Talk of Iowa, host Charity Nebbe spoke with experts about some of the risk factors and the relationships between blood clots and other diseases. You can find that entire conversation here.

Hematologist Dr. Rachel Rosovsky is the director of thrombosis research in the division of hematology at Massachusetts General Hospital and an assistant professor at the Harvard Medical School. She joined the conversation to talk about the risks associated with blood clots and COVID-19.

This interview has been edited for length and clarity.

Nebbe: "When people are in the hospital, that puts them at greater risk for developing blood clots. That's something that medical teams are aware of, and, if this seems to be a risk factor, should treat. Is that something that, if we are in the hospital, we should ask our doctor about?"

Rosovsky: "Absolutely, absolutely. If the hospital is not having that be a priority, and you're in the hospital, and you're sitting around and bed-bound and immobile, just had surgery, just had anesthesia, if it's safe for you, you're not at a big bleeding risk, then absolutely it's something to ask your doctor. The other thing is, usually, when people are in the hospital, they try to encourage people to get out of bed and walk around, again, if that can be done safely. And then, unless there's a reason you're not allowed to keep yourself hydrated, keeping yourself hydrated is really important as well."

Nebbe: "Let's talk about blood clots and COVID-19. Because, of course, that is something that we've heard a lot about this year. COVID-19 is a virus that affects the body in so many different ways. We've learned so much about it, but there's still a lot we don't know, and it affects us in some really surprising ways. What is the relationship, at least what do we know about the relationship, between COVID-19 and blood clots?"

Rosovsky: "COVID-19 has obviously been quite devastating. And I would say, one of the silver linings is that, I think, it has raised awareness about blood clots because it's in the news. And there is this incredible association between patients with COVID-19 and blood clots. And, essentially, we think it has to do with lots of different pathways, whereby the virus, once it attaches and gets in, can kind of create this inflammatory state in this relationship between inflammation and coagulation and really revving up your clotting system when it shouldn't be revved up. For example, if you cut yourself you want your clotting system to be revved up and make a scab and stop that bleeding. But when blood clots happen when they're not supposed to, that's when people get these DVTs and PEs. And so, unfortunately, COVID kind of retaliated in terms of this inflammation and revving up of the clotting system."

via the National Blood Clot Alliance

Nebbe: "When people go to the hospital for COVID-19, blood clots are something that seemed to cause a lot of problems for the people who wound up in the hospital. Tell me about that."

Rosovsky: "Early on, we were seeing a lot of people come in and (we were) thinking, 'how do we treat these patients?' And, early on, we realized that there was a marker of clotting that was much higher in the really sick patients. And if they were really sick, and in the ICU, they were at a higher risk of developing these blood clots. So, very early on, thrombosis experts around the world came together to try and publish guidelines like 'what should we be doing?' And one of the universal guidelines was really put people on blood thinners, if you're hospitalized, and there are no contraindications to being put on one of those low-dose blood thinners, you should absolutely be put on one.

"Then the question was 'should we do a higher dose with some people?' and also, 'what is the rate of fibrosis?' And if you look at the literature, it spans the gamut. So we looked at our own institution, and we found the rate of clotting just took everybody — people in the wards and in the ICU — was about 4.8 percent. But we actually found the rate of bleeding to be just as high. So we were concerned about giving more than a higher dose of blood thinner. So we kept everybody kind of at a low dose. And patients in the intensive care unit, just because they're sicker, and again, they might be more inflamed from their severities of COVID, and they have various lines in place, maybe they're more immobile, maybe they're more sedated, those people are at a higher risk. And we do find that the number could be higher than that. So I think there's a definite connection, there are definite ways to try to prevent blood clots, very similar to non-COVID patients. But we just know that there's this very strong association. A lot of people say, 'well, what do we do for patients that are sick with COVID and don't need to be hospitalized? Should they be on blood thinner?' And right now, we don't know the answer to that question. We don't think that they're at a higher risk, but there is a study going on to try to figure out that question.

"What I tell my patients is 'if you have COVID, you need to keep yourself very well hydrated.' The problem is people have to be quarantined. I had a patient who had COVID and she had to be quarantined in her bedroom by herself and ended up getting a blood clot. She was really likely in bed the entire time. So if you are at home, even if you are quarantined, try and do leg exercises, try to get up and walk around. And again, the hydration is key, just to, again, try to prevent that. But at this point, we're not putting people who are at home with COVID on a blood thinner, but being aware of the symptoms. And it's hard with COVID because COVID you're short of breath. So one of the symptoms of a blood clot is shortness of breath. So how do you tease that out? And, oftentimes, it's very difficult to tease that out. But if you're at home with COVID, and your breathing is getting worse, you should absolutely seek medical attention to make sure it's not just worsening COVID, in which case, you might need different therapies, but also that it's not a blood clot."

Nebbe: "Tell me about the difference between blood thinners and anticoagulants?"

Rosovsky: "Well, blood thinners are anticoagulants. Essentially, when you get a blood clot, your own body has natural anticoagulants and those are going to start to break down the blood clot. But without putting somebody on an anticoagulant, which is a blood thinner, then that blood clot can get bigger, and that blood clot can break off and go various places. So the blood thinner that people are on, it's trying to shut the coagulation system down, so you don't make more blood clots and make the blood clot that you have worse. But your own body kind of breaks down the blood clot."

Nebbe: "Now, of course, we also all know that, particularly with theJohnson & Johnson vaccine, and with the AstraZeneca vaccine to prevent COVID-19, we know that there was identified a small risk, a slight risk for blood clots with those vaccines. Tell me more about what we know about that."

Rosovsky: "We do know that, first of all, it's exceedingly rare, and that some people that get those vaccines can go into a similar kind of inflammatory system where they're getting, almost like reaction, where their platelets can go low. And in that situation, they actually develop blood clots from the vaccine. And again, this is exceedingly rare. But I would say we do know that it's higher in a certain percentage of people — the women ages 18 to 49. And so, because we have alternatives, it's important for people in that age range, if they do have alternatives, to think about the alternatives. But again, it's so exceedingly rare, that it's more important, I think, that people actually get the vaccine. And then if they do fall into that category to think, if they do have access to the alternative, to think about that."

Nebbe: "Alright, and so what I hear you saying is thatrisks of serious blood clottingfrom getting COVID-19 are far, far higher than the risk presented by the Johnson & Johnson vaccine."

Rosovsky: "Well, yes, but actually, the risk of getting COVID and dying from COVID is what I'm most concerned about. I'm also concerned about people getting blood clots from COVID, but people get COVID — not only just blood clots, but there can be some post sequelae from the COVID itself. So I really encourage people to get the vaccine and not not delay that."

Nebbe: "When somebody experiences blood clots, they seem to be more likely to experience blood clots in the future. Do you think that for people who have survived COVID, and have had blood clotting related to COVID, is this something that they're at risk for now for the rest of their lives?"

Rosovsky: "When people get a blood clot, we kind of think about, is it provoked? Can we identify the cause? Or is it unprovoked, like completely out of the blue and we have no idea? And so when people get a blood clot related to COVID, we do think of that as is a provoking factor. Things like pregnancies provoked, oral contraceptives, long travel, surgery, cancer, things like that, that have already been alluded to. And when people have a blood clot, yes, they are at risk of getting another blood clot in the high clotting situation.

"So what I tell my patients is when they've had a provoked blood clot, we usually treat between three and six months on the blood thinner and, at that time, we sit down together and think 'are there any ongoing risk factorsthat that person has that still might put them at risk of getting another blood clot?' And if we've taken away all the risk factors, and they have a low chance of getting another blood clot, we'll stop the blood thinner. But I also tell those people, in any other high-clotting risk situation, I'm going to want to put you back on a low-dose blood thinner if you're in one of those high-clotting risk situations, again, because we already know that you tend to clot in these high clotting risk situations. And so if you do that, then the risk goes way down. I'll also just point out that in people that have a provoked blood clot, who have ongoing risk factors, there's actually literature now to suggest they should stay on a low dose blood thinner. Because if you have ongoing risk, and you haven't taken away that ongoing risk, they're going to be at a higher chance of getting a blood clot. And that's very similar to people that have an unprovoked blood clot, which means you can't identify the cause. If you can't identify the cause, if you stop those people's blood thinner, they're at a very high risk of getting another blood clot too. These are just really important questions to ask your provider and really play out the situations, and, really, for the provider to really listen to their patients and know what their risks are.

Nebbe: "And I can imagine that providers are still learning about this as well. I mean, you've published 25 articles on COVID and blood clots in the last year. So you've been spreading a lot of information. But I mean — this is a new virus. This is something that we're still experiencing and learning about, and not every provider is going to know about that risk."

Rosovsky: "Exactly. I mean, even, how long should we treat people with COVID and a blood clot? Where does that come from? You know, we didn't really know. And so we're extrapolating from the other other literature and other situations that you're exactly right."

"And there's so little known about the post-COVID. Like, we know, patients that get blood clots that are not related to COVID, there's something called post-PE syndrome or post thrombotic syndrome (pts), where people can have ongoing shortness of breath, ongoing leg pain or leg swelling. But there's also this major — which we don't really know that much about — impact on quality of life that must be mentioned. And that can be associated with depression and anxiety and pain and shortness of breath and all that. And so we don't know, at this point, what this post-COVID-PE, and -DBT can be because we just don't have the data. So there's actually some studies that are hopefully going to be up and running about this so that we can really learn more about it to be able to help our patients.

"I would say the most important thing is if you've had COVID, and you've had a blood clot, just to be in touch with your provider, and discuss with them 'how long do I need to be on the blood thinner?' And then 'once I stop it, what do I need to watch out for?' And, specifically, what to watch out for is any new shortness of breath, new chest pain, chest pressure, leg pain, leg swelling. Or if you notice, 'wow I'm having a hard time doing my workout like I used to,' or 'I improved and then I got worse.' So any kind of changes, definitely to reach out.

"The other thing is, just in terms of lifestyle changes, we know, the risks. Isolation we talked about, dehydration we talked about, but weight is another big risk factor, obesity. And so I just encourage people to think about getting themselves healthy and getting themselves in shape. Smoking is another one. And so if people are smoking, I really encourage people to stop smoking. So I think being healthy is important."

Nebbe: "I want to address a question we have from Tom in Iowa City. He's asking: 'is taking an aspirin a day or taking a baby aspirin a day something that I should do to try to prevent blood clots?' And I know that that used to be a recommendation, but I don't believe it is anymore."

Rosovsky: "So Toddsaid that he has theFactor V Leiden. Factor V Leiden didn't cause the blood clot. Factor V Leiden places, or any inherited risk factor, will place people at a higher risk of getting a blood clot. But if somebody has Factor V Leiden, and let's say I had a patient who had Factor V Leiden and was on an oral contraceptive with estrogen, well once we stop that woman's estrogen, we've taken away the main cause of her blood clot, and that's somebody who could consider stopping blood thinner. That's somebody I might say, well, maybe we keep you on a baby aspirin because you have the underlying, inherited predisposition. And that might help you. I think, for people that have no underlying risk factors, we don't have data to suggest that they should be put on an aspirin to prevent this."

Nebbe: "Okay, so talk to your doctor about that. We do know that there's a relationship between cancer and blood clots. Tell me, briefly, what that's about."

Rosovsky: "Remember, we talked about COVID and that revving up the blood clotting system? That's exactly what cancer can do, is that can rev up the clotting system. And the risk of getting a blood clot if you have cancer ranges anywhere from five to 40 percent. And we know that there are certain cancers that are at a much higher risk of developing a blood clot. And in fact, there's been two recent studies that show putting those patients at the highest risk of getting blood clots, high risk cancers like pancreatic cancer and certain gastrointestinal cancers, those people, actually, this study showed that if they're put on a blood thinner at the time of their cancer diagnosis, there's less chance that they're going to get a blood clot. So if, God forbid, somebody develops cancer, that's definitely something you want to talk to your doctor about: 'what is my risk of a blood clot? Do I have one of those high risk cancers? Should I be put on a blood thinner?' and oftentimes, if people don't have any other contraindications for not putting on a blood thinner, we will do that. The other thing about cancer and clotting is it's so important — when people first find out they have cancer, they're so overwhelmed. There's so much going on, and oftentimes, it's not talked about, but just really educating patients about the signs and symptoms of blood clot. And if they develop any of those to absolutely seek medical attention and let their providers know."

Nebbe: "Can being put on a blood thinner interfere with your ability to get a surgery?"

Rosovsky: "If you are on a blood thinner because you've had a blood clot, oftentimes we'll ask the surgeons if we can delay any elective surgery for a certain amount of time because the risk of getting another blood clot is very high in that acute setting. And if you are on the blood thinner to prevent blood clots, then we just hold the blood thinner before the surgery, and how long we hold will depend on the surgery and what your other issues are, if you have normal kidney function, things like that.

"But in general, if people are on a blood thinner and they're going to have a surgery that might involve some kind of bleeding, we'll hold the blood thinner for a few days beforehand. Now your risk of getting a blood clot by holding it for those few days is not zero, but it's pretty low. And again, we have to kind of weigh those risks and benefits. In general, if people are on a blood thinner and they need urgent surgery, sometimes we can do things to help decrease that risk of bleeding which is what we care about if people are on a blood thinner and need urgent surgery."

You can hear the entire conversation with Rosovsky and other experts on this episode of the Talk of Iowa podcast. And you can find more information about blood clots from the National Blood Clot Alliance.

Rick Brewer was a producer for IPR's Talk of Iowa and River to River
Charity Nebbe is the host of IPR's Talk of Iowa