What Is Thromboembolism?

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Thromboembolism is a medical term used to describe a blood clot (thrombus) that forms in a blood vessel, breaks loose, and is carried by the bloodstream to block another blood vessel. When an unattached mass of any sort (called an embolus) causes an obstruction, the blockage is referred to as an embolism.

Artwork showing a blood clot traveling through a vessel

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Thromboembolism is a dangerous condition that can affect multiple organs, causing organ damage and even death. Although the terms thromboembolism and thrombosis are sometimes used interchangeably, the latter describes a blood clot that forms in a blood vessel rather than one that breaks off and blocks a blood vessel.

Types

There are two main categories of thromboembolism, differentiated by the types of blood vessels they affect.

Venous Thromboembolism

Venous thromboembolism occurs when a blood clot breaks off and blocks a vein. 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 embolus and the degree of blood flow obstruction.

The broader term venous thromboembolism generally refers to DVT, PE, or a combination of the two (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, causing ischemia (the restrictions of blood flow and oxygen) and sometimes infarction (tissue death due to an inadequate blood supply). The majority of arterial embolisms involve a blood clot.

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.

Symptoms

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

Venous Thromboembolism

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

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

Arterial Thromboembolism

The sudden onset 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 limb
  • 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

Causes

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

Venous Thromboembolism

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)

Arterial Thromboembolism

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

Diagnosis

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

Venous Thromboembolism

The main challenge of DVT/PE is that the 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 to diagnose PE
  • 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 getting oxygen or not

Arterial Thromboembolism

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 transducer (sensor) into the throat and esophagus
  • Myocardial contrast echocardiography (MCE): A form of ultrasound that uses an injection of tiny microbubbles 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

Treatment

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 the treatment.

Venous Thromboembolism

The first-line treatment of venous thromboembolism are anticoagulants ("blood thinners") that prevent a clot from becoming larger while the body slowly reabsorbs it. There are injectable anticoagulants like heparin and Arixtra (fondaparinux) and oral ones like Coumadin (warfarin), Eliquis (apixaban), and Xarelto (rivaroxaban).

If an anticoagulant is not enough, a procedure called an inferior vena cava filter 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.

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).

Arterial Thromboembolism

Many of the same interventions 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 include embolectomy (to remove the clot), arterial bypass surgery (to reroute the blood supply), and angioplasty (to increase blood flow with a balloon catheter with or without a stent).

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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14 Sources
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