Thrombosis Vs. Embolism

Medically Reviewed by Melinda Ratini, MS, DO on April 29, 2022
5 min read

Thrombosis and embolism are both blood clots that reduce or block blood flow inside your blood vessels. They’re two different yet serious conditions. Here’s a look at the differences and similarities.

Thrombosis happens when a blood clot (thrombus) forms locally in a blood vessel and slows or blocks the flow of blood. There are two types of thrombosis:

Venous thrombosis is when the blood clot blocks a vein. Veins carry blood from the body back into your heart. Deep vein thrombosis (DVT) is the most common type. It usually forms in the deep veins of your lower leg. But it can also form in the veins of your thigh, pelvis, or arm.

Arterial thrombosis is when the blood clot blocks an artery. The arteries carry oxygen-rich blood from the heart to the rest of your body.

Arterial thrombosis happens when deposits of fat and calcium (plaque) build up on the walls of the arteries that supply blood to the heart. When this buildup makes the artery walls thick, it’s called arteriosclerosis. This thickening slows or blocks the flow of blood and causes blood pressure to build. If a plaque deposit bursts, a blood clot can form and cause a heart attack. If it blocks the arteries that carry blood to your brain, it can cause a stroke.

An embolus is any foreign substance that moves in your bloodstream until it blocks a blood vessel. An embolism is often caused when a thrombus or a piece of thrombus breaks off from where it formed and travels to another area of your body.

An embolism is a life-threatening condition and can cause serious complications such as stroke (clot in the brain) and pulmonary embolism (clot or blockage in the lung).

There are many types of thrombosis and embolism. Venous thromboembolism (VTE) is an umbrella term that doctors use to refer to blood clots that start in the veins, such as DVT. The most serious complication of these clots is a pulmonary embolism (PE). This is when the clot travels through the bloodstream to the lung, where it can cause permanent damage.

A DVT can happen to anybody at any age. But they are usually preventable and treatable if found early. This can also prevent a PE from forming.

Blood clot conditions like DVT and PE affect as many as 900,000 people per year in the U.S.

Risk factors for thrombosis and embolism include:

  • Family history of a blood clots
  • Use of birth control, especially methods that use estrogen
  • Pregnancy
  • Injury to a vein, such as from surgery, or other trauma
  • Lack of movement for long periods, such as after surgery or during a long plane or car trip
  • Genetic blood clotting disorders
  • A central venous catheter
  • Older age, usually above 60
  • Smoking
  • Obesity
  • Health conditions, such as cancer, heart disease, lung disease, or Crohn's disease

Signs and symptoms vary for each person and depend on where the clot is located and how big it is. And it’s possible that you might not have symptoms. In fact, it happens in about half the cases.

Common DVT symptoms include:

  • Pain
  • Swelling
  • Redness in the area
  • Tender to touch

If you notice this, tell your doctor right away.

Arterial thrombosis symptoms may include:

  • Numbness or weakness on one side of the body
  • Sudden change in your mental state
  • Chest pain
  • A visible change in skin color
  • Skin that’s cool to the touch in the affected area

If you have any of these signs, call 911 and get immediate medical help.

If you have a PE, your symptoms may include:

  • Difficulty breathing
  • Fast and irregular heartbeat
  • Chest pain or discomfort, which worsens with a deep breath or coughing
  • Coughing up blood
  • Very low blood pressure
  • Lightheadedness, or fainting

PE is life-threatening. If you notice these symptoms, get medical help right away.

If your doctor suspects a thrombosis, they’ll first do a detailed physical exam and history. Your doctor will also run imaging tests to help locate the clot, such as:

Your doctor may also use blood tests:

  • Blood count: Analyzes the makeup of your blood, including the platelets involved in clotting.
  • D-troponin test: Looks for a protein called D-troponin that shows up in your blood when your heart has been damaged, such as with a heart attack.
  • D-dimer test: Measures levels of a blood protein called D-dimer. A high level of D-dimer may mean that you have a blood clotting condition.

These tests can help your doctor pinpoint where the clot is located and what might have caused it. This will help come up with an appropriate treatment plan.

A pulmonary embolism is hard to diagnose, especially if you have heart or lung disease. Diagnostic tests are similar to a thrombosis. Additional tests may include:

  • Chest X-ray
  • CT pulmonary angiography
  • Ventilation-perfusion scan
  • Pulmonary angiogram

Many different things will affect your treatment plan. Your doctor will look at:

  • Your age
  • Overall health
  • Medical history
  • How sick you are
  • Your tolerance for certain medicines, treatments, or therapies
  • If your condition is expected to get worse

Treatment options for thrombosis and embolism may include:

  • Blood-thinning medicines (anticoagulants)
  • Thin tubes (catheters) to widen the affected vessels
  • A wire mesh tube (stent) that holds a blood vessel open and stops it from closing
  • Clot dissolvers (thrombolytics)
  • Surgery (thrombectomy) to remove the clot
  • Inferior vena cava filters. These are little pieces of mesh surgically placed over the clot to prevent it from spreading to the heart or lungs.

If your embolism is caused by an air bubble, your doctor might recommend a hyperbaric chamber. It’s a clear case long enough for you to lie down. The air pressure inside the chamber is higher than the normal air pressure outside. This helps to reduce the air bubble inside your body.

Complications may include:

  • A pulmonary embolism. A larger clot or many clots can raise your risk for death.
  • Postphlebitic syndrome. This is when a clot damages the vein and reduces overall blood flow to an area. This can cause leg pain, swelling, and discoloration.
  • Bleeding risk from blood-thinning drugs like warfarin and heparin
  • Stroke
  • Heart attack

If you have a thrombosis like DVT, the outlook is good. The symptoms usually go away in time with proper treatments like medication and lifestyle changes. It may take anywhere from 3-6 months for your clot to dissolve.

As for embolisms like PE, how well you recover depends on a few things such as:

  • What caused the embolism
  • The size of the clot
  • If the blood clot dissolves over time

About 33% of those with a DVT or PE have another blood clot within 10 years. Untreated or serious DVT or PE kills up to 100,000 people per year in the U.S. And about 25% of those with PE die suddenly with no symptoms.

It’s hard to detect a blood clot in your body before it forms. But they are preventable. The key to preventing a clot from becoming a deadly embolism is lifestyle changes.

You should:

  • Stay active with regular exercise
  • Maintain a healthy weight
  • Eat a balanced diet
  • Quit smoking

If you have a DVT, it’s important to follow your treatment plan closely to stop it from progressing to PE. If you notice signs and symptoms of an embolism, call 911 immediately or head to the nearest hospital for medical help.