May 2021

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Blood Clots Explained

Clearing Blockages in the System

Your blood is an amazing, multi-purpose substance. It flows continuously through the body, carrying oxygen and nutrients to your cells. But if you get a scrape or cut, some of this flowing liquid quickly turns to a protective clot.

Clots are tangles of molecules and blood cells that clump together. They help prevent blood loss when the skin breaks open. They also help stop infections from getting inside the body. But when clotting happens inside a blood vessel, it can be dangerous.

Clots can form on the blood vessel walls to help them heal if they get damaged. Afterward, the clots usually dissolve. But sometimes a clot doesn’t get broken down as it’s supposed to. Clots may also form when they’re not needed.

Sometimes, clots break off a vessel wall and travel through the blood to other parts of the body. They may cause a lot of damage, depending on where they block blood flow. Blood clots can potentially harm the brain, heart, lungs, or other organs.

But researchers have made great progress over the last few decades in managing blood clots. They continue to develop new ways to treat and prevent such blockages.

Clogs in the System

Three main things can lead to dangerous blood clots, explains Dr. Mitchell Elkind, an expert on stroke at Columbia University. “One is an abnormality in the blood that makes it more likely to clot. For example, Having to do with genes. Genes are stretches of DNA you inherit from your parents. They define features like your risk for certain diseases. genetic causes, cancer, or damage from smoking,” he says. “The second is when blood doesn’t flow properly.” This can be a side effect of diseases and disorders of the heart or blood vessels.

The third is damage to the lining of blood vessels. One cause of such damage is cholesterol buildup in the blood. Cholesterol is a waxy, fat-like substance that can clump together to form plaques. If a plaque breaks apart, it can damage the blood vessel.

Blood clots can happen to anyone, at any age. But some people are at increased risk. These include older adults and those with certain heart conditions.

Major surgery or a serious injury also add risk. Obesity, being physically inactive, and some medications can boost the chance of a dangerous clot, too.

“And once you’ve had one blood clot, you’re at high risk of another one,” notes Dr. Nigel Key, an expert on blood disorders at the University of North Carolina.

Some infections may also increase the risk of blood clotting. Recent studies have shown that the virus that causes COVID-19, SARS-CoV-2, can cause blood clots in some people.

Symptoms of a Clot

Blood clots can occur anywhere in the body. That makes it difficult to find them before they cause a problem, Elkind explains. The symptoms of a blood clot depend on where they are.

A clot blocking blood flow to the brain can lead to a stroke. Strokes can cause sudden difficulty seeing, speaking, or walking. They can also make you feel weak, numb, dizzy, or confused.

A clot that blocks blood flow to the heart can cause a heart attack. The most common signs are crushing chest pain and difficulty breathing. Others range from cold sweats to arm or shoulder pain.

A clot in the lungs can cause shortness of breath, pain when breathing deeply, or even coughing up blood. A clot in a vein deep within the body is called a deep vein thrombosis, or DVT. Symptoms include swelling, pain, warmth, or red or discolored skin. These usually happen in your legs. Long periods of inactivity can increase your risk.

“Compared with a heart attack or stroke, there’s low awareness of the symptoms of deep vein thrombosis,” Key says. Many symptoms overlap with less dangerous conditions, such as a muscle sprain.

If you have symptoms of a blood clot, call your health care provider or 911 immediately. You may need to go to the hospital to have blood or imaging tests.

Busting Blockages

Treatment depends on where a clot is and how long you’ve had symptoms. Certain drugs can break up and dissolve some types of clots. But they have to be given within a few hours of when symptoms start.

A type of surgery called a thrombectomy can be used to remove clots in large blood vessels. It can be used even if people don’t get to the hospital in time to receive clot-busting drugs. “That’s been a huge benefit for patients,” says Dr. Waleed Brinjikji, an expert on stroke at the Mayo Clinic.

This technique has also let researchers study what clots are made of after they’re removed. “We’re starting to realize how different clots can be,” says Brinjikji.

Different types of clots might benefit from different removal techniques or drugs. So Brinjikji’s team is now testing ways to identify the type of clot before it’s removed. That way they can start to test which treatments work best.

Stopping a Clot

If you have a clot that’s forming, certain medications may help shrink it or stop it from growing. These drugs are called anticoagulants. They’re more commonly known as blood thinners.

Sometimes, people with certain heart conditions are given blood thinners to prevent blood clots from forming. But blood thinners can have side effects, including an increased risk of bleeding. So doctors don’t give them to everyone.

Elkind’s team has been researching which heart conditions may benefit from this type of preventive treatment.

Recent research has shown that blood thinners may help in COVID-19. They might reduce the risk of blood clots and organ damage in people hospitalized with COVID-19. More work is underway to figure out how best to prevent and treat blood clots for those with the disease.

This work will also help researchers better understand how other viruses can affect the blood, Elkind explains. “I think we’re going to learn a lot about how other infections also trigger clotting from studying COVID-19,” he says.

There are many things you can do to decrease your risk of harmful blood clots. See the Wise Choices box for tips.

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