Thrombosis: What It Is, Types, Treatment, and Prevention

Medically Reviewed By John A. Moawad, MD, FACS
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Thrombosis is when a blood clot, called a thrombus, develops in a blood vessel. A thrombus can occur in either an artery or a vein, partially or completely blocking blood flow. Symptoms of thrombosis will depend on where the clot forms. There are various causes and risk factors for thrombosis. Some of them are preventable, while others are not.

Treatment depends on where the clot is and how serious the symptoms are. Doctors may opt to dissolve or remove the clot or use medications to prevent it from growing. 

This article gives an overview of thrombosis. It covers the types, causes, risk factors, symptoms, treatment, and prevention of this common condition.

What is thrombosis?

Thrombosis refers to the presence of a thrombus. A thrombus is a blood clot in a blood vessel, either an artery or vein.

A thrombus that breaks away from where it forms and travels to another area is an embolus. An embolus is a blood clot or other substance that travels in the bloodstream and lodges in a vessel.

Thromboembolism is the term for a thrombus becoming an embolus. A pulmonary embolism (PE) is an example. This article focuses on thrombosis.

A thrombus limits blood flow through a blood vessel, either partially or completely blocking it. This can occur anywhere, such as the arms, legs, heart, lungs, brain, or kidneys. Depending on where the clot forms, it can be fatal. In fact, thrombosis is at the core of the most common causes of death in the developed world: heart attack and stroke.

What are the types of thrombosis?

There are two types of thrombosis.

Arterial thrombosis

Arterial thrombosis occurs when a blood clot develops in an artery. Arteries are the vessels that deliver blood from the heart to the organs and tissues. This includes the heart muscle itself, through the coronary arteries. Common types of arterial thrombosis include:

  • heart attack or coronary artery thrombosis
  • peripheral artery disease
  • brain or cerebral thrombosis, including stroke and transient ischemic attack

Other sites of arterial thrombosis include the kidneys, intestines, and eyes.

Venous thrombosis

Venous thrombosis is the formation of a blood clot in a vein, which returns blood to the heart. Types of venous thrombosis include:

  • cavernous sinus thrombosis
  • deep vein thrombosis (DVT), which can affect the deep veins in the arms or the legs
  • jugular vein thrombosis
  • retinal vein occlusion
  • superficial vein thrombosis, which affects veins close to the surface
  • superior vena cava thrombosis

What causes thrombosis?

There are three main factors that contribute to thrombosis:

  • damage to the lining of blood vessels
  • hypercoagulation, when there is an imbalance in blood clotting factors that makes blood more likely to clot
  • stasis, when blood is not flowing optimally and can pool or collect

Arterial thrombosis is mainly the result of damage to the lining of the blood vessels due to atherosclerosis. This process starts with fatty deposits that form hardened plaques on the vessel walls. The plaques narrow vessels and increase the risk of clots developing.

Arterial thrombosis can also form due to an arterial embolus, a clot that blocks the flow of blood through an artery, usually traveling from the heart.

Venous thrombosis, such as DVT, often occurs as the result of hypercoagulation or stasis. Damage to vessel wall linings can also cause it.

What are the risk factors for thrombosis?

A man is sitting at desk; prolonged sitting can be a risk factor for thrombosis.
Irina Polonina/Stocksy United

There are several risk factors and conditions that contribute to thrombosis, including:

What are the symptoms of thrombosis?

Symptoms of thrombosis vary depending on the site of the blood clot. However, they all can result from reduced blood flow and lack of oxygenated blood. Venous thrombosis can also occur due to congestion in the veins causing a backup of blood flow, similar to water backing up behind a dam.

Pain is a common symptom of all types of thrombosis. The pain will occur where the clot is, such as in the legs for a DVT or the chest for a coronary artery thrombosis.

Symptoms of thrombosis in the abdomen may include:

Symptoms of thrombosis in the arms and legs may include:

  • muscle pain and cramping
  • redness or warmth of the skin
  • swelling

Symptoms of thrombosis in the brain may include:

Symptoms of thrombosis in the coronary arteries may include:

  • chest pain, tightness, or discomfort
  • lightheadedness
  • pain in the upper body, including the arm, shoulder, neck, or jaw
  • shortness of breath
  • sweating

Symptoms of thrombosis in the lungs may include:

How do doctors diagnose thrombosis?

Diagnosing a blood clot will depend on the type and location. In general, doctors will take a detailed medical history and perform an exam. If they suspect a blood clot, testing is usually necessary.

This may include various blood tests and imaging exams. The diagnostic process is more aggressive for potentially life threatening clots, such as coronary artery thrombosis, which can cause a heart attack.

How is thrombosis treated?

Treatment of thrombosis also depends on the type of blood clot. This includes whether it is a venous or arterial thrombus and if it is acute or chronic.

Doctors will also take into account whether this is the first incident and if you are medically stable or not.

Treatment generally relies on three options:

  • anticoagulants, which are the most common treatment, make the blood less able to clot
  • thrombolytics, which can dissolve large or life threatening clots
  • surgical procedures to remove the clot

How do you prevent thrombosis?

Thrombosis is very preventable if you know your risk factors. Many risk factors are modifiable. Others are not under your control.

Depending on your risks, your doctor may prescribe medicines to reduce the risk of developing a clot. This may involve taking an anticoagulant, such as:

Other ways to prevent thrombosis include:

  • getting regular physical activity
  • maintaining a moderate body weight
  • stopping smoking
  • taking frequent breaks during periods of sitting
  • seeking treatment for chronic conditions that can lead to clotting

Summary

Thrombosis occurs when a blood clot forms in either an artery or vein. The symptoms and severity of the problem depend on where the clot develops. Some clots, such as those in a coronary artery, can be life threatening.

Treatment also depends on where the clot is, along with other factors. Anticoagulants are a common treatment option. However, life threatening clots require more aggressive treatment.

Knowing your risk factors is key to preventing thrombosis. Talk with your doctor about how to modify or mitigate your risk.

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Medical Reviewer: John A. Moawad, MD, FACS
Last Review Date: 2022 Mar 30
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