Thrombosis

Thrombosis is a serious medical condition where blood clots form inside your blood vessels or heart, blocking normal blood flow and potentially causing life-threatening emergencies like stroke, heart attack, or pulmonary embolism.

Table of contents

• What Is Thrombosis?
• Types of Thrombosis
• How Common Is Thrombosis?
• Symptoms of Thrombosis
• Causes and Risk Factors
• Complications of Thrombosis
• How Thrombosis Is Diagnosed
• Treatment of Thrombosis
• Prevention of Thrombosis
• Living After a Blood Clot

What Is Thrombosis?

Thrombosis is the formation of a blood clot, called a thrombus, inside one of your blood vessels or a chamber of your heart^[1]. While blood clots normally help prevent blood loss when you are injured, they can become dangerous when they form inside blood vessels without injury^[5].

When a blood clot forms, it can block blood flow in your blood vessels or break free and travel elsewhere in your body^[1]. If a clot gets stuck in a critical location like your lungs or brain, it can disrupt blood flow to that organ and result in a life-threatening emergency^[1]. A clot that breaks free and begins to travel around the body is known as an embolus^[5].

Thrombosis is a serious condition that 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^[1].

Types of Thrombosis

The two main types of thrombosis are arterial thrombosis and venous thrombosis^[1][6].

Arterial thrombosis is when a blood clot forms in an artery. Your arteries carry blood from your heart to the rest of your body. A blood clot blocks an artery carrying blood away from the heart to the body^[6]. Arterial thrombosis is the most common cause of heart attacks and strokes^[1].

Venous thrombosis is when a blood clot forms in a vein. Veins carry blood back to your heart from your body^[1]. A blood clot blocks a vein carrying blood from the body back into the heart^[6]. Venous thrombosis is the most common cause of a pulmonary embolism, which is a blood clot in your lung^[1].

Deep vein thrombosis, or DVT, occurs when a blood clot forms in one of the deep veins in the body, usually in the legs^[4][7]. DVT most commonly occurs in the lower leg, thigh, or pelvis, but can also occur in the arm^[7].

When deep vein thrombosis and pulmonary embolism occur together, it is called venous thromboembolism, or VTE^[4][7].

How Common Is Thrombosis?

Thrombosis is extremely common and is the underlying cause of 1 in 4 deaths worldwide^[1]. Together, acute venous and arterial thromboses account for the most common causes of death in developed countries, with myocardial infarction (heart attack) and cerebrovascular accident (stroke) accounting for the highest proportion of thrombosis-associated death in the United States^[2].

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^[1]. 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^[1]. Sometimes deep vein thrombosis can occur without noticeable symptoms^[4].

Deep Vein Thrombosis Symptoms

About half of people with DVT have no symptoms at all^[7]. The most common symptoms of DVT that occur in the affected leg or arm include^[7][13]:

• Leg swelling
• Throbbing pain in one leg, usually in the calf or thigh, when walking or standing up
• Leg pain, cramping, or soreness that often starts in the calf
• Warm skin around the painful area
• Change in skin color on the leg, such as red, purple, or darkened skin (this may be harder to see on brown or black skin)
• Swollen veins that are hard or sore when you touch them

Pulmonary Embolism Symptoms

You can have a pulmonary embolism without any symptoms of a DVT^[7]. Signs and symptoms of pulmonary embolism can include^[7][1]:

• 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
• Difficulty breathing
• Faster than normal or irregular heartbeat
• Chest pain or discomfort, which usually worsens with a deep breath or coughing
• Cough or coughing up blood
• Very low blood pressure, lightheadedness, or fainting

Stroke Symptoms

A blood clot in blood vessels in your brain can cause a stroke^[3]. Symptoms of a stroke can include^[3][6]:

• Weakness or drooping in your face, arm, or leg
• Confusion or difficulty understanding and speaking
• Difficulty speaking or understanding
• Dizziness or loss of balance
• Blurred vision or difficulty swallowing
• Severe headaches with no other known cause

Heart Attack Symptoms

A blood clot in the blood vessels that supply your heart can lead to a heart attack^[3]. Symptoms of a heart attack can include^[3]:

• Chest pain or discomfort (it may feel like your chest is being pressed or squeezed by a heavy object)
• Shortness of breath
• Feeling weak
• Nausea
• A cold sweat
• Feeling anxious
• Feeling dizzy or lightheaded

If you or someone with you has symptoms of thrombosis, seek emergency medical care immediately. Call triple zero (000), 999, or 911 depending on your location and ask for an ambulance^[3][4].

Causes and Risk Factors

Blood clots can happen for many reasons, but generally they develop because of one or more risk factors^[21]. Often, several of these risk factors contribute to the development of a clot. Sometimes blood clots can happen for reasons that are never identified; these are called unprovoked (unexplained) blood clots^[21].

Common Risk Factors

Blood clots can form if you don’t move around a lot^[12]. You may also get a blood clot if you^[12][7][1]:

• Have had recent surgery
• Are 65 or older
• Are over 40
• Are overweight or obese
• Smoke
• Have had DVT before
• Take hormones, especially for birth control or hormone replacement therapy (HRT)
• Are staying in or recently left hospital, especially if you cannot move around much (like after an operation)
• Are confined to bed
• Go on a long journey (more than 3 hours) by plane, car, or train
• Are pregnant or if you have had a baby in the previous 6 weeks
• Are dehydrated

Medical Conditions That Increase Risk

Thrombosis is more common among people with certain medical conditions, including^[1][6][13]:

• Atrial fibrillation
• Cancer
• Coronary artery disease
• Diabetes
• Clotting disorders such as antiphospholipid syndrome
• Heart failure
• Varicose veins

Individual risk depends on the cause of the blood clot. For example, DVT patients who have a genetic mutation that puts them at higher risk of blood clots have a very high risk of recurrent DVT and will need to be on blood thinners for life. But for patients whose DVT is the result of a temporary risk factor, such as surgery or trauma, the risk of future blood clots is quite low^[17].

Complications of Thrombosis

Thrombosis can lead to many different complications depending on where the blood clot forms or travels to^[1]:

• 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

The most serious complication of DVT happens when a part of the clot breaks off and travels through the bloodstream to the lungs, causing a blockage called pulmonary embolism^[7]. If the clot is small and with appropriate treatment, people can recover from PE. However, there could be some damage to the lungs^[7].

One-third to one-half of people who have a DVT will have a long-term complication called post-thrombotic syndrome, or PTS^[7]. PTS is caused by the damage the clot does to the valves in the vein. People with PTS have symptoms such as swelling, pain, discoloration, and in severe cases, scaling or ulcers in the affected area^[7].

How Thrombosis Is Diagnosed

To diagnose DVT, your healthcare provider will do a physical exam and ask questions about your symptoms^[10]. The provider will check the legs for swelling, tenderness, or changes in skin color^[10].

If a doctor thinks you have DVT, you should be referred to hospital within 24 hours for an ultrasound scan^[13]. The scan shows whether blood is flowing normally through the vein^[13].

Tests used to diagnose or rule out DVT include^[10]:

• D-dimer blood test: D dimer is a type of protein produced by blood clots. Almost all people with severe DVT have increased blood levels of D dimer. This test often can help rule out pulmonary embolism.
• Duplex ultrasound: This test uses sound waves to create pictures of how blood flows through the veins. It is the standard test for diagnosing DVT.
• Venography: This test uses X-rays and dye to create a picture of the veins in the legs and feet.
• Magnetic resonance imaging (MRI) scan: This test may be done to diagnose DVT in veins of the belly.

Treatment of Thrombosis

The primary objectives for the treatment of deep venous thrombosis are to prevent pulmonary embolism, reduce morbidity, and prevent or minimize the risk of developing the post-thrombotic syndrome^[15]. The mainstay of medical therapy for DVT has been anticoagulation, which means using blood-thinning medicines^[15].

Blood Thinners

There are three main goals to deep vein thrombosis treatment^[10]:

1. Prevent the clot from getting bigger
2. Prevent the clot from breaking loose and traveling to the lungs
3. Reduce the chances of another DVT

You may have an injection of a blood-thinning medicine called heparin while you’re waiting for an ultrasound scan to see if you have a DVT^[13]. Blood thinners, also called anticoagulants, help prevent blood clots from getting bigger and reduce the risk of developing more clots^[10].

The main treatments include^[13]:

• Blood-thinning medicines, such as warfarin or rivaroxaban—you’ll probably need to take these for at least 3 months
• If you get a DVT when you’re pregnant, you’ll have injections for the rest of the pregnancy and until your baby is 6 weeks old

Anticoagulation options for acute VTE include unfractionated heparin, low molecular weight heparin, fondaparinux, and the direct oral anticoagulants, or DOACs^[11]. DOACs are as effective as conventional therapy with LMWH and vitamin K antagonists^[11].

Other Treatment Options

Other treatment approaches may include^[13][11]:

• Surgery to remove blood clots or stop them forming
• Thrombolytic therapy (clot-dissolving medicine), which is reserved for massive pulmonary embolism or extensive deep vein thrombosis
• Inferior vena cava filters, which are used in certain situations when anticoagulation cannot be used

Important Treatment Notes

If you take the blood thinner warfarin and certain other blood thinners, you shouldn’t take aspirin unless your doctor says it’s OK. That’s because it can raise your chances of major bleeding^[20]. Some antibiotics can keep these medicines from working the way they should. You should be careful with over-the-counter herbal supplements^[20].

If you take warfarin, you’ll need to watch what you eat. Vitamin K can affect how the drug works. So you have to be careful about the amounts of kale, spinach, Brussels sprouts, chard, or collard or mustard greens you eat. Green tea, cranberry juice, and alcohol can affect blood thinners, too^[20].

Prevention of Thrombosis

There are things you can do to lower your chance of getting DVT^[13][19]:

• Stay a healthy weight
• Stay active—taking regular walks can help
• Drink plenty of fluids to avoid dehydration (DVT is more likely if you’re dehydrated)
• Do not sit still for long periods of time—get up and move around every hour or so
• Do not cross your legs while you’re sitting
• Do not smoke
• Do not drink lots of alcohol

Prevention During Long Journeys

If you’re traveling for 3 hours or more by plane, train, or car, there are things you can do during the journey to lower your chances of getting DVT^[13][19]:

• Wear loose clothing
• Drink plenty of water
• Avoid alcohol
• Walk around when possible
• Try not to stay seated for more than 2 hours at a time
• Pump your feet up and down by pulling your toes up toward your knees then pointing them down
• Exercise your lower leg muscles

Prevention in Hospital

If you go into hospital, your healthcare team should check if there’s a higher chance you’ll get DVT^[13]. If they think you’re more likely to get DVT, you may be given treatment to prevent it, such as medicine or compression stockings (knee-high elastic socks that help your blood circulation), while you’re in hospital^[13]. You may continue treatment after you leave hospital because a blood clot can happen weeks later^[13].

You can also help protect yourself against DVT while you’re in hospital by^[13][19]:

• Staying active and walking around if you can
• Moving your toes (up and down) and ankles (in circles) if you have to stay in bed
• Getting up out of bed as soon as your doctor says it’s okay

Living After a Blood Clot

Life after deep vein thrombosis or pulmonary embolism can be stressful. Recovery can take upwards of several months and you’ll need to make sure you adhere to your doctor’s medication and treatment schedule^[17].

Risk of Another Clot

If you’ve had a blood clot before, your chances of another one are higher^[20]. After treatment, you’ll need to watch for signs of another clot. After a clot in one of your legs or arms, it’s sometimes normal for that limb to stay slightly swollen after treatment. After a clot in your lungs, you might feel mild pain or pressure in your chest. But watch out for new or worse pain, pressure, or cramping in your calf. That could signal a new DVT. Shortness of breath or fainting could be signs of another PE^[20].

For patients whose DVT is the result of a temporary risk factor, such as surgery or trauma, the risk of future blood clots is quite low. For those patients whose cause of DVT is unknown, if they’ve been treated with a blood thinner for three to six months, the risk of having a recurrent blood clot in the next year is about 10 to 15 percent. Within five years, the risk of having a recurrent blood clot is 5 percent^[17].

Recovery Tips

After you leave hospital, you’ll be encouraged to^[13][20]:

• Walk regularly
• Keep your affected leg raised when you’re sitting
• Delay any flights or long journeys until at least 2 weeks after you start taking blood-thinning medicine
• Get moving—exercises like walking or swimming can help you heal after a clot
• Exercise—activities that get your heart pumping can make your lungs stronger if you had a pulmonary embolism

Important Safety Measures

Your doctor may prescribe clot-fighting drugs called blood thinners. These can make you more likely to bleed from small injuries, so it’s important to be careful when trimming your nails. You should wear gloves when you use sharp tools, and wear safety gear for sports and hobbies^[20].

Let all your doctors know if you’ve had a blood clot of any kind. And if you take blood thinners, tell your dentist when you make your appointment^[20].

Compression Stockings

Your doctor might recommend compression stockings after a PE to boost your circulation^[20]. These special tight-fitting socks keep a certain amount of pressure on your leg, and that can help with blood flow after a DVT^[20].