Dangerous blood clots form in leg arteries of COVID-19 patients

COVID-19 is associated with potentially fatal blood clots in the arteries of the legs, according to a study published in Radiology. According to the researchers, COVID-19 patients with symptoms of inadequate blood supply to the lower extremities tend to have larger clots and a significantly higher rate of amputation and death than uninfected people with the same disease.

The association of COVID-19 with blood clots in the pulmonary arteries is well established. Less known is the association between the virus and lower extremity arterial thrombosis, a condition characterized by blood clots in the arteries that impede the flow of oxygenated blood to the lower extremities.

At the height of the COVID-19 pandemic in New York City, radiologists at Montefiore Medical Center observed an increase in the number of patients with lower extremity arterial thrombosis during CT angiography exams. Patients had arrived at the hospital with cold sensations, pain or discoloration of their legs. Often, these symptoms of leg ischemia, a condition in which blood flow to the lower extremities is restricted, were accompanied by respiratory distress, cough, fever, and altered mental status.

This alarming trend prompted researchers to look more closely at a possible link between COVID-19 and lower extremity arterial thrombosis and to determine whether people with the virus had a worse prognosis.

In March and April 2020, they identified 16 COVID-19-positive patients, average age 70 years, who underwent CT angiography of the lower extremities for symptoms of leg ischemia. These patients were compared with 32 COVID-19-negative patients, mean age 71 years, who underwent CT angiography with similar symptoms in previous years and who were well matched to the COVID-19 cohort for demographic and clinical characteristics.

All COVID-19 patients undergoing CT angiography of the lower extremities had at least one clot in the leg, compared with only 69% of controls. Clots in COVID-19 patients were significantly larger and more frequently involved arteries higher in the leg than in controls. Death or limb amputation was more common in patients in the COVID-19 group.

"We found that COVID-19-associated arterial thrombosis was characterized by disastrous outcomes, namely a striking increase in amputation and death rates, which in our series were 25% and 38%, respectively," said the study's senior author, Inessa A. Goldman, M.D., a radiologist at Montefiore and assistant professor at Albert Einstein College of Medicine in New York City. "For comparison, the rate of amputation and death was only 3 percent in controls. It is unclear whether the patients' concomitant COVID-19-related pneumonia, the virulence of the COVID-19-related bleeding disorder, or the late initial arrival at the hospital contributed to these results."

COVID-19 patients with only leg ischemia symptoms were more likely to avoid amputation or death than patients with ischemia symptoms and systemic symptoms, including cough, respiratory distress or failure, hypoxia, fever, or altered mental status.

"In our cohort, none of the five patients complaining only of leg symptoms, such as pain or discoloration, without systemic symptoms, underwent amputation or died," Dr. Goldman said.

Dr. Goldman noted that with increasing rates of infection in many parts of the country, it is important that physicians be aware of the link between COVID-19 and lower extremity arterial thrombosis.

"Awareness of lower extremity arterial thrombosis as a possible complication of COVID-19 infection is important for all providers caring for these patients, as early diagnosis is usually crucial for limb preservation in lower extremity ischemia," she said.

The association of COVID-19 with lower extremity arterial thrombosis is likely related to a combination of factors, Dr. Goldman said, including an increased tendency of blood to clot, artery wall damage, and immune responses related to SARS-CoV-2 and COVID-19 infection.

"This area continues to be intensely studied around the world," she said.