Asked & Answered: COVID-19 FAQs

Since the start of the pandemic, NATF has received several questions on COVID-19 and blood clots. We’re pleased to welcome Dr. Alex Spyropoulos to answer some of these FAQs! Dr. Spyropoulos is a Professor of Medicine at the Zucker School of Medicine in New York and the Systems Director of the Hofstra-Northwell Anticoagulation and Thrombosis Services. He has been involved in thrombosis-related research for 25 years.

Q: Why do blood clots occur in patients with COVID-19?

COVID-19 represents “the perfect storm” for thrombosis. The virus causes a local inflammatory response, usually starting in the lungs, which progresses to what we call a cytokine storm, an immune-mediated storm. In other words, the body’s “over-response” to the virus causes all of these complications. The cytokines and inflammation in the body activate multiple steps of the blood clotting system. It’s almost like a cascade, like a domino effect, resulting in high rates of things like pulmonary embolism (PE), heart attack, and stroke.

We really worry about these complications in the COVID-19 patients who are sick enough to be hospitalized, especially those who are in the intensive care unit. And we’re still concerned about clots when these patients leave the hospital.

For outpatients with COVID-19—the patients who have mild illness and can manage the virus at home—we think the risk of blood clots is low, but we don’t know for sure.

Q: Are patients in a high-risk category for a COVID-related blood clot if they’ve had a prior blood clot unrelated to COVID-19? 

Yes. In my view, these patients represent a high-risk group. Patients with blood clots—especially “unprovoked” clots—have a chronic cardiovascular disease (CVD) process. With acute COVID-19 infection, that underlying risk “activates” so to speak, putting these patients at higher risk than patients without underlying heart disease.

Any patient with underlying cardiopulmonary disease is also in a higher risk category. For example, chronic PE, meaning chronic thromboembolic pulmonary hypertension (CTEPH), is a cardiopulmonary disease, and that would raise a patient’s risk.

Q: Are there other diseases or conditions that raise the risk for blood clots in the setting of COVID-19? 

Yes. We now have data that several conditions are risk factors for COVID-related thrombotic complications, including diabetes, obesity, and current tobacco abuse. We think autoimmune diseases may also be a risk factor, although there’s not a lot of data yet.

Q: Do genetic clotting disorders increase a patient’s risk of COVID-related thrombosis?

Well, not all genetic disorders are the same. For example, there are some severe genetic disorders such as protein C and S deficiency, which are deficiencies of anticlotting proteins. In my view, those disorders represent a higher-risk genetic category than heterozygous Factor V Leiden or heterozygous prothrombin gene mutation – heterozygous meaning that you have a gene from one parent causing this disorder. If you have a homozygous clotting disorder—two bad genes from mom and dad—then yes, you’re in a higher-risk category. The vast majority of patients who have a heterozygous Factor V Leiden or prothrombin gene mutation and have had a blood clot may be in a slightly elevated, but not very elevated, thrombotic risk category. It’s really the patients with severe disorders or homozygosity states that I worry about.

Q: What advice would you give to patients with genetic clotting disorders?

The best advice is don’t get COVID! If you have a genetic clotting disorder, I’d recommend being strict about social isolation and preventative measures. Stay hydrated, exercise or do some physical activities around the house, walk, etc. Those are the commonsense things you could do. Some patients have asked me about taking antithrombotic therapy, like a baby aspirin. That may not be a bad thing to do, although you should talk to your healthcare provider before starting any new medication.

Q: If patients already take a blood thinner and then get COVID-19, are they protected from COVID-related clots?

There’s good and bad news with anticoagulation. The good news is that more and more data suggest that being on an anticoagulant decreases your risk of getting hospital-associated blood clots. So, if you’re already on an anticoagulant and are hospitalized for COVID-19, you’ll have a lower risk of getting a clot in the hospital than someone not on anticoagulation. But regardless of COVID-19, if you’re on a blood thinner, definitely stay on the blood thinner – and be rigid and disciplined about taking it. If you’re on warfarin, you have to be very good about maintaining your INR in the appropriate target range. If you’re on a direct oral anticoagulant (DOAC), you need to make sure to take it like clockwork.

The bad news is that if you’re on an anticoagulant, you either have a previous history of clots or you have a risk factor for a clot, like atrial  fibrillation. As I mentioned, a previous history of clots puts you at an elevated risk, so don’t think you’re out of the woods simply because you’re on a blood thinner. Again, this means that social distancing and other preventative measures are in order and patients should take these precautions seriously.

Q: What is the anticoagulation protocol for COVID-19 patients both in the hospital and after discharge?

In the US, the medical community quickly realized that all hospitalized COVID-19 patients should get some type of preventive anticoagulation, which we call chemical prophylaxis. The two front-line agents that we use are called low-molecular-weight heparin or unfractionated heparin. If you’re a hospitalized COVID-19 patient, you should be on some type of prophylaxis unless there’s a reason you can’t be, like active bleeding, a history of bleeding, or a low platelet count. So, preventive anticoagulation is the first order of business and I would call it a universal protocol at this point.

I should point out that the dose of heparin used varies among institutions. Some hospitals are more aggressive with the dose and others are comfortable giving a lower dose. There’s no evidence at this point that a higher dose of heparin, what we call a treatment dose, is more likely to prevent blood clots. There are ongoing clinical trials to look at this issue.

Many institutions prescribe preventive anticoagulation for COVID-19 patients who have been discharged from the hospital as well. Even though there’s no COVID-specific data, we have data to draw from in other patients with infections, and we’ve found that the risk for a blood clot can linger for up to 30 days after leaving the hospital.

At my institution, most patients will go home on a post-discharge rivaroxaban (Xarelto^®) dose of 10 mg for up to 30 days, which is FDA-approved. Other DOACs (dabigatran, and edoxaban) have not been studied in patients leaving the hospital, and apixaban hasn’t been shown to be effective in this setting.

Q: If patients are taking warfarin, should they continue to come to the hospital for blood tests or would you suggest transitioning to home testing or to a DOAC?

I think COVID-19 has created a perfect opportunity for home testing. As a matter of fact, some colleagues and I recently published a study and found that telehealth INR management may improve time spent in the therapeutic INR range by up to 45%, which is a huge jump. Most insurers now cover home testing.

I also think it’s is a great time to switch to a DOAC (from warfarin) if you can. But “if you can” is the important point here. Most patients on warfarin take it because they have situations that prevent them from taking a DOAC, like a mechanical heart valve, or warfarin is simply more affordable. 

I’d recommend speaking to your doctor or pharmacist if you’re interested in either home testing or switching to a DOAC.

Q: Are there any conditions that would prevent someone from wearing a mask? 

Absolutely not. Wearing a mask is critical to preventing the spread of COVID-19 and protecting yourself from COVID-19. Don’t use the excuse of having an underlying heart or lung condition to avoid wearing a mask. It’s probably the single most important thing you can do.

Q: Is there any role for vitamin C, vitamin D, other supplements in preventing or treating COVID-19? 

There’s no high-quality data suggesting that vitamins or supplements can prevent or treat COVID-19. I think the most important thing that a patient can do is make their everyday health a priority. Exercise, stop bad habits like smoking, keep your blood pressure and blood sugar under control, and take your medications as prescribed. If you’re on a statin, stay on it. The usual cardiovascular preventative measures, in my view, are the best thing to do, along with social distancing and wearing a mask when you leave your home!

Interested in learning more about COVID-19 and blood clots? Check out our patient resource page and video library.

If you have specific questions about COVID-19 and your health, please contact your healthcare provider.

*Originally published in The Beat – August 2020. Read the full newsletter here.