COVID-19 and blood clots

In addition to the immune and cardiovascular response associated with COVID-19, it also appears to cause blood clots in some patients, which has become a common and menacing complication of the disease. Depending on the location, clots can cause stroke, heart attack and pulmonary embolism.

People with more severe COVID-19 symptoms seem to be more susceptible to blood clots. A study from the Netherlands reported that 30% of patients with COVID-19 who were admitted to a hospital's intensive care unit experienced blood clots.

SARS-CoV-2, the new coronavirus that causes the disease known as COVID-19, infects the body by entering cells that have receptors — called angiotensin converting enzyme-2 (ACE2) — on their surface. The virus's spiky proteins bind to these receptors. Once bound, the virus can enter and infect the cell.

ACE2 receptors are found on various cells throughout the body, such as lung and heart muscle cells. It is in these locations where symptoms and complications due to the body's systemic inflammatory response against the disease can occur.

"Lung and heart muscle cells have these receptors that the virus can bind to, and in turn, infect the cell, which can lead to pulmonary embolisms and heart attacks," says Dr. Scott Musicant, a vascular surgeon affiliated with Sharp Grossmont Hospital. "But we also know that these receptors are found on the smooth muscle cells that line the inside of blood vessels. When the virus infects these cells, coagulation and thrombosis — or blood clots — can form."

Blood clots can then travel by blood vessels to vital organs. They have riddled the lungs of patients with severe COVID-19 infection. Coupled with additional respiratory complications like pneumonia, patients with these micro-clots experience dangerously low blood oxygen levels.

"Low blood oxygen can interfere with bodily functions affecting everything from the kidneys to the brain. When organs are deprived of oxygen, it can cause the body's systems to fail," says Dr. Musicant.

Doctors are also seeing ischemic stroke in patients with COVID-19. An ischemic stroke happens when a blood clot traveling in a blood vessel blocks oxygen-rich blood from reaching the brain. Strokes can result in impaired speech and reduced mental and physical function.

"Risk factors such as high blood pressure, diabetes, high cholesterol and smoking can put anyone at a higher risk for stroke," says Dr. Ryan Viets, an interventional neuroradiologist affiliated with Sharp Grossmont Hospital. "However, along with these groups, we are also seeing patients with low or no risk factors, particularly middle-aged and younger individuals, experiencing stroke due to COVID-19."

For instance, clots in large blood vessels leading to the brain have been observed in patients under age 50. In these cases, surgeons may perform a thrombectomy, which involves threading special tools through the blood vessels to grab and remove the clot, in order to restore blood flow to the brain.

Blood-thinning medications are a standard stroke treatment, and are also being used for patients with COVID-19. Doctors are working to get a better understanding of the ideal dose when administering blood-thinning medications because they can have serious side effects, including excessive bleeding. However, the medications have proven to be beneficial for the critically ill. A study noted fewer deaths among patients with COVID-19 on mechanical ventilation who were given blood-thinning medicines, compared to those not treated with the drugs.

"Regardless of whether a stroke is brought on by COVID-19, it is important to get to the hospital immediately once you notice signs and symptoms," says Dr. Viets. "When blood flow to the brain stops, brain cells die quickly, causing sometimes irreversible damage and disability. So quick treatment, whether medical or surgical, is imperative to preserve brain function."

Dr. Viets adds, "I understand that people may be nervous about going to a hospital during this pandemic. Be assured that safety is a priority for us at all times. We employ exceptional measures to keep our patients safe while providing essential, quick treatment."

Learn more about stroke care at Sharp Grossmont Hospital.