Thrombosis

What is thrombosis?

Thrombosis occurs when blood clots block your blood vessels. There are 2 main types of thrombosis:

  • Venous thrombosis is when the blood clot blocks a vein. Veins carry blood from the body back into the heart.
  • Arterial thrombosis is when the blood clot blocks an artery. Arteries carry oxygen-rich blood away from the heart to the body.

What causes thrombosis?

Venous thrombosis may be caused by:

  • Disease or injury to the leg veins
  • Not being able to move around (immobility) for any reason
  • A broken bone (fracture)
  • Certain medicines
  • Obesity
  • Inherited disorders, or a greater likelihood of having a certain disorder based on your genes
  • Autoimmune disorders that make it more likely your blood will clot
  • Medicines that increase your risk of clotting (such as certain birth control medicines)

Arterial thrombosis may be caused by a hardening of the arteries, called arteriosclerosis. This happens when fatty or calcium deposits cause artery walls to thicken. This can lead to a buildup of fatty material (called plaque) in the artery walls. This plaque can suddenly burst (rupture), followed by a blood clot.

Arterial thrombosis can occur in the arteries that supply blood to the heart muscle (coronary arteries). This can lead to a heart attack. When arterial thrombosis occurs in a blood vessel in the brain, it can lead to a stroke.

What are the risk factors for thrombosis?

Many of the risk factors for venous and arterial thrombosis are the same.

Risk factors for venous thrombosis may include:

  • A family history of a blood clot in a vein deep in the body, called a deep vein thrombosis (DVT)
  • A history of DVT
  • Hormone therapy or birth control pills
  • Pregnancy
  • Injury to a vein, such as from surgery, a broken bone, or other trauma
  • Lack of movement, such as after surgery or on a long trip
  • Inherited blood clotting disorders
  • A central venous catheter
  • Older age
  • Smoking
  • Being overweight or obese
  • Some health conditions, such as cancer, heart disease, lung disease, or Crohn’s disease

Risk factors for arterial thrombosis may include:

  • Smoking
  • Diabetes
  • High blood pressure
  • High cholesterol
  • Lack of activity and obesity
  • Poor diet
  • Family history of arterial thrombosis 
  • Lack of movement, such as after surgery or on a long trip
  • Older age

What are the symptoms of thrombosis?

Each person’s symptoms may vary. Symptoms may include:

  • Pain in one leg (usually the calf or inner thigh)
  • Swelling in the leg or arm
  • Chest pain
  • Numbness or weakness on one side of the body
  • Sudden change in your mental state

The symptoms of thrombosis may look like other blood disorders or health problems. Always see your healthcare provider for a diagnosis.

How is thrombosis diagnosed?

Your healthcare provider will take your medical history and give you a physical exam. Other tests may include:

  • Ultrasound. This test uses sound waves to check the blood flow in your arteries and veins.
  • Blood tests. These may include tests to see how well your blood can clot.
  • Venography. For this test, a dye is injected into your veins. Then X-rays are taken to show blood flow and look for clots. The dye makes your veins easier to see on the X-rays.
  • MRI, MRA or CT. The imaging procedure that is used will depend on the type of blood clot you have and where it is located.