Some people face a higher risk of thrombosis due to medical conditions or other factors. Learning your risk can help you prevent thrombosis, and learning the symptoms can help you recognize problems if they occur. Thrombosis is a serious condition, and it can become more dangerous as time passes. It can quickly turn into a medical emergency. The sooner you seek care for thrombosis, the better your chances of a good outcome. If you or someone with you has symptoms of thrombosis, seek emergency medical care immediately.

Complications of thrombosis

Thrombosis can lead to many different complications depending on where the blood clot forms or travels to:

• Lungs: Pulmonary embolism.

• Brain: Transient ischemic attack (TIA) or stroke.

• Heart (coronary artery): Heart attack.

• Neck (carotid artery): TIA or stroke.

• Belly (superior mesenteric artery or one of its branches): Mesenteric ischemia.

Types of thrombosis

The two main types of thrombosis are:

• Arterial thrombosis. This is when a blood clot forms in an artery. Your arteries carry blood from your heart to the rest of your body. Arterial thrombosis is the most common cause of heart attacks and strokes.

• Venous thrombosis.This is when a blood clot forms in a vein. Veins carry blood back to your heart from your body. Venous thrombosis is the most common cause of a pulmonary embolism (blood clot in your lung).

Thrombosis is dangerous in either location (artery or vein) because it can:

• Cause a blockage where it forms.The clot may stay in place and grow until it’s big enough to block blood flow. The severity of that blockage depends on where the clot forms and how big it grows.

• Cause a blockage somewhere else.The clot may break free from its origin and become an embolus. It can then travel in your blood and get stuck in a smaller blood vessel, creating a blockage (embolism). This is usually what causes conditions like stroke and pulmonary embolism.

How common is thrombosis?

Thrombosis is extremely common and is the underlying cause of 1 in 4 deaths worldwide. That’s because thrombosis can lead to dangerous conditions like a heart attack, stroke or pulmonary embolism.

Thrombosis is more common among people with certain medical conditions, including:

• Atrial fibrillation.

• Cancer.

• Coronary artery disease.

• Diabetes.

• Clotting disorders such as antiphosph olipid syndrome.

• Tobacco use.

Symptoms and Causes

What are the symptoms of thrombosis?

Thrombosis symptoms depend on the size of the clot, its location (where it forms or gets stuck) and the complications it causes. Blockages are more likely to occur in areas with very small blood vessels, especially your lungs, brain and farther down in your legs and arms. Listed below are common symptoms for each location:

Lungs (pulmonary embolism)

• Sharp pain in your chest and surrounding areas (jaw, neck, shoulder, back or arm).
• Pain when you breathe in.
• Sudden trouble breathing when active or at rest.

Brain or neck (transient ischemic attack (TIA) or stroke)

• Weakness or trouble controlling muscles on one side of your body.
• Slurred or garbled speech.
• Noticeable droop and lack of muscle control on one side of your face.
• Confusion, agitation or otherwise unusual behavior changes.

Heart (heart attack)

• Chest pain or discomfort (angina).
• Trouble breathing.
• Dizziness or passing out.
• People assigned female at birth often have additional symptoms.

Belly (mesenteric ischemia)

• Severe stomach or abdominal pain, especially after eating.
• Bloating, nausea and vomiting.
• Diarrhea, which may contain blood.
• Fever.

Artery in arm or leg

• Skin that looks paler than other areas.
• Skin that feels cool to the touch.
• Weakness and inability to move the affected body part.
• Numbness or tingling (pins and needles), possibly with pain.
• Blisters, wounds or sores.
• Skin sloughing, which is when skin falls away from the tissue underneath.
• Necrosis, or tissue death.

Vein in arm or leg

• Skin that looks redder or darker than other areas.
• Pain, especially around the affected area.
• Swelling from fluid buildup.
• Skin that feels warm to the touch.

What causes thrombosis?

Thrombosis happens when something damages the inner lining of your blood vessel (endothelium) or slows blood flow. In either case, cells in your blood start to stick together when they shouldn’t.

Normally, many cells in your blood coexist in harmony and come together when needed for a certain job. For example, if you have a wound, platelets and proteins join together at the site of injury to serve as a plug. This multistage process (hemostasis) forms a necessary clot that stops you from losing too much blood. The clot dissolves when your wound heals. It’s like an emergency meeting at work when everyone huddles at one desk. When the problem’s solved, everyone leaves and goes their separate ways.

But various medical conditions, medications and other factors can cause components of your blood to cluster together when they don’t need to or fail to dissolve when they should. As a result, a blood clot (thrombus) may form from clumps of blood clotting components and potentially get bigger. It may also break away and travel through your bloodstream until it gets stuck in a smaller blood vessel (embolus).

Both of these situations can lead to dangerous — or even life-threatening — complications. That’s why it’s important to learn what may put you at risk.

What are the risk factors?

Anything that interferes with your blood’s ability to flow freely or clot normally can raise your risk for thrombosis. This includes many conditions, medications and lifestyle factors.

• Atherosclerosis.
• Atrial fibrillation.
• Being over age 60.
• Blood clotting disorders.
• Cancer.
• Chemotherapy.
• Diabetes.
• Family history of blood clots.
• Having certain surgeries or procedures, including central line placement.
• Heart failure.
• Heart valve disease.
• High blood pressure.
• High cholesterol.
• Inflammatory or autoimmune diseases.
• Obesity.
• Paralysis of a leg.
• Pregnancy.
• Prior heart attack or stroke.
• Sitting still for too long for various reasons, including long flights or bed rest.
• Tobacco use.
• Using birth control pills containing estrogen.
• Using hormone replacement for menopause symptoms.

Outlook / Prognosis

What can I expect if I have this condition?

Early diagnosis and treatment can restore your blood flow and lower your chance of complications. If a complication (like a heart attack or stroke) leads to your diagnosis, your provider will treat that condition and do whatever possible to restore function to affected organs and tissues.

How long does thrombosis last?

It depends on the underlying cause, the treatments and how quickly you seek medical attention. Thrombosis can be short-lived with prompt treatment. However, the conditions that cause it may be chronic or lifelong. For example, blood clotting disorders that you’re born with may put you at risk for thrombosis throughout life. Your provider can help you manage underlying conditions to lower your risk.

What is the outlook for people with thrombosis?

Your outlook or prognosis depends on many factors, including:

• How quickly you seek care.
• Where the clot forms.
• Whether the clot stays in one place or travels in your bloodstream.
• Whether complications occur.

A clot that stays in place is a problem, but it’s usually less dangerous than a clot traveling in your bloodstream. The outlook for thrombosis can worsen when a free-floating clot ends up in a critical organ like your heart, brain or lungs.

Your provider can tell you more about your prognosis based on your individual situation.

Living With

How do I take care of myself?

If you’ve had thrombosis in the past or are at risk, it’s crucial to:

• Take your medications exactly as your provider tells you to. The risk of complications increases sharply if you suddenly stop taking medications that prevent thrombosis, especially blood-thinners. It’s also dangerous to take more than the recommended amount (such as double-dosing after forgetting to take a dose).
• See your provider regularly. Your provider will tell you how often you should come in for appointments. Go to all of your appointments so your provider can keep an eye on your condition.
• Make lifestyle changes. Ask your provider which changes are most important for you, and ask for resources to support you along the way.
• Connect with others. Talking with others who are in your shoes can help manage any worries or anxieties you might feel. Your provider can help you find communities where you can connect in-person or online.

When should I go to the ER?

Call 911 or your local emergency number if you have symptoms of thrombosis. Don’t delay. Thrombosis can very easily become a dangerous, life-threatening condition. The more minutes that pass, the greater the risk of complications.