UChicago Medicine doctors report an increased risk of blood clots in patients with COVID-19

Drs. Ahmed and Paul review scan
(Left to right) Jonathan Paul, MD, and Osman Ahmed, MD, examine patient imaging for blood clots.
Doctors at the University of Chicago Medicine have seen a sharp increase in large blood clots found in the legs and lungs of people with COVID-19, including younger patients who typically don’t experience them.

UChicago Medicine’s Jonathan Paul, MD, said the Pulmonary Embolism Response Team, or PERT, saw a 75% increase in cases last year (from 154 in 2019 to 270 in 2020). Similarly, the volume of patients with large blood clots in the legs (also known as deep vein thrombosis, or DVT) has increased significantly, said vascular and interventional radiologist Osman Ahmed, MD. While not all of them had COVID-19, the doctors attribute part of the uptick in volume to the virus.

Studies are underway to learn more about COVID-19’s lasting impacts on the body. In some patients, this can include damage to the lungs, heart, kidneys and/or brain. UChicago Medicine is actively studying strategies to prevent and manage COVID-19-related blood clotting. Early in the pandemic, hospitals in New York City reported a 30% rate of blood clots among ICU patients with COVID-19, a percentage well above normal for patients who are critically ill.

“It’s likely a direct effect of COVID-19,” said Paul, UChicago Medicine’s PERT director and an interventional cardiologist.

Here are a few basic facts about blood clots, the symptoms, and what you should do if you think you might have one. This information applies to everyone, but is especially important for people infected with COVID-19.

What is a blood clot?

A blood clot forms when liquid blood coagulates and becomes a semisolid, gel-like structure inside a blood vessel. Blood clots may form in response to a number of conditions, such as an acute illness, immobility or inflammation. If you get hurt, a blood clot usually forms to stop the bleeding. Most of the time, the body can dissolve a clot on its own. In certain cases, however, the clot does not resolve and continues to grow in size.

When a blood clot forms in the large veins in the legs (a DVT), it can break off and travel through the bloodstream to the lungs, a condition known as pulmonary embolism (PE). A PE can be life-threatening and can cause symptoms such as shortness of breath, chest pain, rapid heart rate, dizziness or excess fatigue.

How do you know if you have a blood clot?

Only a medical provider can make the diagnosis, using imaging tests performed in a hospital or office. DVT can be silent, but some people experience limb pain, swelling or discoloration of the skin. A PE typically causes shortness of breath, chest pain, dizziness or extreme fatigue. If you believe you may have either a DVT or PE, it is important to see a doctor immediately.

Will a blood clot go away on its own?

It could. Our bodies have their own innate mechanisms to dissolve blood clots. This process may take weeks to months. In some cases, blood clots may cause permanent damage to blood vessels.

What happens if a blood clot goes untreated?

If a DVT is left untreated, there may be scarring of the veins in the legs and abdomen. If that occurs, then there is essentially a blockage of the blood flow back to the heart. That doesn’t mean the blood doesn’t get back to the heart, but the blockage can cause leg swelling, pain and skin changes, such as darkening or ulcers. This can be very debilitating, and it’s sometimes not recognized by non-vascular specialists.

What should you do if you think you have a blood clot?

It is important to be evaluated immediately if you experience symptoms of a blood clot. Your medical provider will likely do imaging exams such as an ultrasound of the leg or, for concerns of a PE, a CT scan of the lungs.

What medications can treat blood clots?

Most blood clots can be managed simply with blood thinners. However, a small percentage of patients will need additional treatment. Through UChicago Medicine’s comprehensive PE and DVT program, we routinely treat patients with high risk blood clots using advanced technologies to dissolve or remove the blood clot, using minimally invasive methods with short recovery times.

How does UChicago Medicine help patients with a blood clot?

We have a streamlined system to evaluate each patient individually, shortly after the patient comes to the hospital. Our experienced team of experts considers all possible options, from conservative management with medications or, if necessary, procedures to directly remove the blood clot. We also routinely follow patients in our post-PE clinic, where we evaluate for lingering symptoms, discuss blood thinner management and screen for chronic blood clotting disorders.

What’s the latest on COVID-19 vaccines that may cause blood clots?


Osman Ahmed, MD

Osman Ahmed, MD, is an expert vascular and interventional radiologist who diagnoses and treats a wide range of conditions. Using image-guided technology and small, sophisticated instruments, Dr. Ahmed performs minimally invasive procedures for acute and chronic deep vein thrombosis, benign prostatic hyperplasia, peripheral vascular disease and more.

Learn more about Dr. Ahmed

Comprehensive Venous Thrombosis and Pulmonary Embolism Program

Blood clots can be dangerous, and even fatal, if you do not receive treatment in a timely manner. The University of Chicago Medicine, our multidisciplinary venous thrombosis and pulmonary embolism team works closely together to quickly identify, screen, diagnose and treat these conditions.

Learn more about our services.

At The Forefront Live: Vascular Disease FAQ

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At The Forefront Live: Vascular Disease FAQ

Chicago Medicine vascular surgeon Chelsea Dorsey, MD, joins interventional cardiologist Jonathan D. Paul, MD, and vascular and interventional radiologist Osman Ahmed, MD, to discuss how to detect, treat and prevent a variety of vascular diseases.

Watch Video With Transcript