What Is Thromboembolism?

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Thromboembolism is the name for when a blood clot (thrombus) that forms in a blood vessel breaks loose, is carried by the bloodstream, and blocks another blood vessel. This is a dangerous condition that can affect multiple organs, causing organ damage and even death.

As such, it requires immediate treatment. Knowing the signs of thromboembolism and who is at risk can help you better recognize when you or someone you love needs medical attention.

Artwork showing a blood clot traveling through a vessel

Science Photo Library / Getty Images

This article takes a closer look at the different types of thromboembolism, including the possible causes and symptoms. It also explains how thromboembolism is diagnosed and the different options used to treat blockages in arteries and veins.

Types of Blockages

There are two main categories of thromboembolism—venous and arterial. As their names suggest, they are differentiated by the types of blood vessels they affect.

Venous Thromboembolism

Venous thromboembolism occurs when a blood clot breaks off and blocks a vein—a blood vessel that brings blood in need of oxygen back to your heart.

Venous thromboembolism often starts in the legs with a condition known as deep vein thrombosis (DVT).

If the clot breaks off and lodges in a lung, it causes a serious condition known as pulmonary embolism (PE). PE can be fatal depending on the location of the clot (also referred to as an embolus) and the degree of blood flow obstruction.

The broader term venous thromboembolism generally refers to DVT, PE, or a combination of the two (called DVT/PE). With that said, thromboembolism can involve other veins of the body, both deep and superficial.

Less common sites of venous thromboembolism include the arms, liver, kidneys, and brain.

Arterial Thromboembolism

Arterial thromboembolism occurs when a blood clot breaks off and blocks an artery, a vessel that brings oxygen-rich blood from the heart to the rest of the body. This causes ischemia, or the restriction of blood flow and oxygen. Sometimes, infarction—tissue death due to an inadequate blood supply—also occurs.

Arterial thromboembolism often occurs in the legs and feet. Some may occur in the brain, causing a stroke, or in the heart, causing a heart attack (myocardial infarction). Less common sites include the kidneys, intestines, and eyes.


There are two types of thromboembolism. Venous thromboembolism occurs in veins and includes deep vein thrombosis (DVT) and pulmonary embolism (PE). Arterial thromboembolism occurs in arteries and is linked to ischemia (the restriction of blood flow due to an obstruction).

Possible Symptoms

The symptoms of thromboembolism vary by where the embolus is located, the extent of blood flow obstruction, and whether ischemia is involved.

When a Vein Is Affected

The most common forms of venous thromboembolism may be recognized by the following signs and symptoms:

  • Deep vein thrombosis (leg): Throbbing, cramps, swelling, warmth, pain, hardened veins, and redness or darkened skin in one leg
  • Pulmonary embolism (lung): Sudden shortness of breath, rapid breathing, chest pain, coughing up blood, and the blueish discoloration of the lips or finger (cyanosis)
  • Cerebral venous thrombosis (brain): Headaches, facial drooping, limb weakness, difficulty speaking, and, in some cases, seizures
  • Portal vein thrombosis (liver): Upper abdominal pain, nausea, abdominal swelling, and persistent fever
  • Renal vein thrombosis (kidney): Flank or lower back pain, decreased urine output, blood in urine, and swelling of the lower limbs

When an Artery Is Affected

Sudden pain is a characteristic symptom of arterial thromboembolism. The most common forms can be recognized by the following signs and symptoms:

  • Limb infarction: Limb coldness, numbness, tingling, pain, muscle weakness, muscle spasms, pale skin, and decreased pulse in the affected arm or leg
  • Heart attack: Chest pains, shortness of breath, profuse sweating, weakness, lightheadedness, nausea, vomiting, and heart palpitations
  • Stroke: Sudden difficulty walking, speaking, and understanding, as well as paralysis or numbness of the face, arm, or leg


Symptoms of thromboembolism can vary by whether the obstruction occurs in a leg, lung, brain, heart, liver, or kidney. The symptoms of a venous obstruction can differ from those of an arterial obstruction.


Venous thromboembolism and arterial thromboembolism affect many of the same people and share several risk factors, but there are key distinctions between the two.

Why Venous Thromboembolism Occurs

Almost anyone can have DVT and, by association, pulmonary embolism. There are risk factors for DVT/PE you can change or control and others you cannot. These include:

  • Family history of venous thromboembolism
  • Obesity
  • Older age
  • Chronic illnesses such as heart disease, lung disease, inflammatory bowel disease, and cancer
  • An injury to a vein (due to trauma or major surgery)
  • Use of a central venous catheter
  • Wearing a cast
  • Bed confinement
  • Sitting for a long time, particularly with crossed legs
  • Estrogen-based treatments (including birth control pills)

Why Arterial Thromboembolism Occurs

Arterial thromboembolism is strongly linked to the same risk factor for heart disease. These include:


Risk factors for venous thromboembolism include bed confinement and sitting for a long time without movement (such as on a plane). Risk factors for arterial thromboembolism are largely the same as for heart disease. Obesity and older age contribute to both.

How Thromboembolism Is Diagnosed

The diagnosis of thromboembolism largely involves imaging studies in combination with blood and lab tests. Some tests are organ-specific.

Confirming DVT and PE

The main challenge of diagnosing DVT and PE is that symptoms can be very similar to those of a heart attack, limb infarction, or even pneumonia.

To confirm the diagnosis and differentiate DVT/PE from other medical conditions, the doctor may order the following tests:

  • D-dimer blood test: Used to detect a substance released with a clot breaks up
  • Factor VIII blood test: Used to detect a protein essential to blood clotting
  • Platelet aggregation test: A blood test that measures how well blood cells called platelets are clumping together
  • Duplex ultrasound: An non-invasive imaging test able to detect blockages in deep veins using sound waves
  • Contrast venography: An X-ray procedure that involves the injection of a contrast dye into a vein
  • Magnetic resonance imaging (MRI): An imaging study that uses powerful magnetic fields and radio waves to create highly detailed images of soft tissues
  • Pulmonary angiography: A specialized X-ray that delivers a contrast dye to the vessels of the lungs
  • Computed tomographic pulmonary angiography: An imaging test that involves the injection of a contrast dye to locate a blockage in the lungs using computed tomography (CT) scan
  • Ventilation-perfusion (V/Q) scan: A specialized procedure that uses a radioactive substance to highlight parts of the lungs that are and are not getting oxygen

Confirming Blockages in Arteries

Some of the same tests used to diagnose venous thromboembolism can be used to diagnose arterial thromboembolism. Others are specialized and specific. These include:

  • Blood tests: Including D-dimer, factor VII, and platelet aggregation
  • Doppler or duplex ultrasound: Used to detect arterial clots using sounds waves
  • Echocardiogram: Used to visualize heart movement using reflect sound waves
  • Transesophageal echocardiography (TEE): A form of echocardiogram that involves the insertion of a sensor into the throat and esophagus
  • Myocardial contrast echocardiography (MCE): A form of ultrasound that uses an injection of very tiny bubbles to provide a more accurate picture of the movement of your heart
  • Plethysmography: A test that uses a blood pressure cuff and sensors to measure changes in volume in arteries
  • Transcranial Doppler exam: Used to detect any blockages in arteries that service the brain


Thromboembolism is diagnosed with specialized imaging studies such as duplex ultrasound and echocardiogram, as well as blood tests called D-dimer and factor VII.


The treatment of venous or arterial thromboembolism can vary based on the location of the embolus and the extent of the blockage. Medications are central to any plan.

Options for Venous Thromboembolism

Anticoagulants ("blood thinners") are the first-line treatments for venous thromboembolism. These drugs prevent a clot from becoming larger while the body slowly reabsorbs it.

There are injectable anticoagulants like heparin and Arixtra (fondaparinux), as well as oral ones like Coumadin (warfarin), Eliquis (apixaban), and Xarelto (rivaroxaban).

If an anticoagulant is not enough, a special filter device can be inserted into the inferior vena cava—the large vein that brings blood back to the heart—to capture a clot before it reaches the lungs.

Drugs called thrombolytics ("clot busters") are reserved for severe cases, as they can cause bleeding. Options include Eminase (anistreplase), Retavase (reteplase), Streptase (streptokinase), and others.14

If needed, surgery can be performed to remove the clot causing DVT (referred to as thrombectomy) or to remove the clot causing PE (referred to as embolectomy).

Options for Arterial Thromboembolism

Many of the same medications used to treat venous thromboembolism are used for arterial thromboembolism. This includes the use of anticoagulants and thrombolytics, as well as antiplatelet drugs like Plavix (clopidogrel) that prevent platelets from clumping together.

Some people may require surgery if the blockage is severe. This may involve:

  • Embolectomy (to remove the clot)
  • Arterial bypass surgery (to reroute the blood supply)
  • Angioplasty (to increase blood flow): This is done with a balloon catheter, a device that enlarges the vessel. A stent, a device left in place to hold the vessel open, may or may not be placed.


Anticoagulants (blood thinners) play a central role in the treatment of thromboembolism. In severe cases, a surgical procedure known as embolectomy may be needed to remove the clot. Bypass surgery or angioplasty may also be needed to treat or repair an arterial blockage.


Thromboembolism describes the obstruction of a blood vessel by a blood clot that has become dislodged from another site in the circulatory system. There is both venous thromboembolism (in which a vein is blocked) and arterial thromboembolism (in which an artery is blocked).

Symptoms of thromboembolism vary by the location of the blockage. Venous thromboembolism often occurs in the legs and lungs, causing deep vein thrombosis and pulmonary embolism, respectively. Arterial embolism can prevent blood flow to the brain or heart, triggering a stroke or heart attack.

Thromboembolism can be often diagnosed with a combination of blood tests and imaging studies. The treatment typically involves blood thinners and other medications, although surgery may be needed to clear the obstruction or reroute the blood flow.

A Word From Verywell

Thromboembolism is almost invariably serious, requiring immediate medical attention. Arguably, the biggest challenge is recognizing the signs and acting quickly.

It helps to identify your risk factors for conditions like DVT, heart attack, and stroke, and do what you can to minimize the risks.

For example, if you have heart disease and are on a long-distance flight, be sure to wear a pair of compression socks, sit with your legs uncrossed, and get up and move frequently. If you are at risk of a heart attack or stroke, controlling your cholesterol and high blood pressure (and quitting cigarettes) can go a long way toward reducing your risk.

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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Richard N. Fogoros, MD
Richard N. Fogoros, MD, is a retired professor of medicine and board-certified in internal medicine, clinical cardiology, and clinical electrophysiology.