VTE occurs in the veins that carry blood to your heart. A deep vein thrombosis may occur if the flow of blood slows down in your body’s deep veins, if something damages the blood vessel lining, or if the makeup of the blood itself changes so that blood clots form more easily. A pulmonary embolism (PE) refers to an embolus from a deep vein blood clot that breaks loose and travels to the lungs, blocking an artery in the lung. Blood clots can develop in veins damaged by surgery or trauma, or a result of inflammation in response to an infection or injury.
Learn more about how blood clots form.
Risk factors for VTE include a history of a previous VTE event; surgery; medical conditions such as cancer or spinal cord injury; pregnancy; paralysis or long periods of immobilization; specific genes; and certain circumstances related to age, race, and sex. In most cases of VTE, there is more than one risk factor involved. The more risk factors you have, the greater the chance you have of developing VTE.
Read Life After for information about the risk of repeat VTE events.
Knee and hip replacement surgery, in particular, carry a high risk for VTE, as does peripheral and coronary artery bypass surgery, surgery to remove cancer, neurosurgery, abdominal surgery, and other major operations. Clotting is one of the body’s natural ways to heal the damage to your blood vessels from surgery. While you wear a cast or stay in bed to heal, your venous circulation slows because you stop moving as much as usual. This lack of movement increases the risk of blood clotting.
The risk of developing VTE is highest in the first three months after surgery and decreases with time. Ask your medical team about prevention strategies if you are scheduled for major surgery.
Certain medical conditions can increase your risk of developing a DVT. Some conditions are more closely linked to developing VTE than others and include the following:
Women who take birth control pills or get hormone therapy have an increased risk of clotting. Some medicines appear to put people at a higher risk than other medicines do, and the risk tends to be highest in the first few months after starting to take them. If you have other risk factors in addition to taking hormone-based medicines, keep in mind that risk for blood clots may be even higher.
Women are at higher risk for VTE during the first six weeks after giving birth to a baby. The risk is also somewhat higher than usual during pregnancy. This may be due to hormones or other factors in the blood, changes in the way blood flows through your veins, or damage to your blood vessels during delivery. If you are required to be on bed rest while you are pregnant, the lack of movement can reduce blood flow through your veins. Surgery for a cesarean delivery may also increase your risk.
Being still slows blood flow through the veins in your arms and legs, raising your risk of deep vein thrombosis. Especially when combined with other risk factors, not moving for long periods of time—such as when on bed rest in a nursing home or hospital setting, when you have a cast, or during a long flight—can increase your risk. Slower blood flow can create a low-oxygen environment that makes it easier for clots to form or trap blood in places such as the veins in the legs where they have a tougher time breaking up.
VTE can occur at any age, but your risk increases as you age. After age 40, the risk of VTE almost doubles every 10 years.
Heredity can affect your chances of developing VTE. Researchers have found dozens of genetic changes that can increase your risk of VTE. Some changes make your blood more likely to clot. If your parents have these genetic changes, you may have inherited them. Studies show that the risk of VTE among siblings of someone who has had VTE is more than double the risk among the general population.
Factor V Leiden is the most common known genetic risk factor for VTE. What is Factor V Leiden?
Studies suggest that the frequency and severity of VTE may vary by a person’s race and ethnicity. In the United States, African Americans have the highest rates of VTE. VTE is less common among Asian Americans and Pacific Islanders. Recent findings have revealed new genetic factors influencing a person’s risk for VTE, and those appear to be more common among African Americans.
Women in their childbearing years are more likely to develop VTE than men of the same age. After menopause, women’s risk is lower than men’s.
If you are preparing to go to the hospital for a procedure or have other risk factors for VTE, talk with your doctor about a plan for preventing blood clots from forming. Doctors may suggest three ways to help prevent VTE:
Your doctor may recommend some combination of these preventive treatments for a month or more after surgery. These approaches to prevention may also be appropriate if you are admitted to the hospital for reasons other than surgery, cannot move for an extended period, or have a condition that makes it more likely that your blood will clot.
The Signs and symptoms of VTE are not the same for everyone. Sometimes VTE does not cause symptoms until serious complications occur. In other cases, deep vein thrombosis causes swelling or discomfort near the blood clot. Pulmonary embolism can cause chest pain and difficulty breathing. Pulmonary embolism can be a life-threatening condition.
Deep vein thrombosis may cause the following to occur around the area of a blood clot:
Signs and symptoms of pulmonary embolism include:
Less common signs and symptoms of pulmonary embolism may include coughing, with or without blood; feelings of anxiety or dread; light-headedness or fainting; and sweating.
Contact your doctor right away if you suspect that you have signs or symptoms of VTE. Deep vein thrombosis should be taken seriously, as it may lead to pulmonary embolism.
Possible complications of VTE include:
Your doctor will ask you about your risk factors and your signs and symptoms for VTE. Your doctor may examine your heart rate and the area that is affected and ask about your overall health, including:
To help diagnose VTE, your doctor may need to do tests to find out if other medical conditions are causing your symptoms. Other tests include:
Not everyone who is diagnosed with VTE needs treatment. In some cases, your doctor will detect a clot and decide to monitor it instead of treating it right away. Doctors usually recommend medicines to treat VTE, but a vena cava filter may be used if you cannot take the medicine.
Anticoagulants, or blood thinners, and thrombolytics are medicines commonly used to treat VTE.
In some cases, including emergencies, a doctor may need to do a catheter-assisted thrombus removal. This procedure uses a flexible tube to reach a blood clot in your lung. The doctor can insert a tool in the tube to break up the clot or to deliver medicine through the tube. Usually you will get medicine to put you to sleep for this procedure.
Some people who cannot take blood thinners may need a vena cava filter to treat their deep vein thrombosis. The filter is inserted inside a large vein called the vena cava. The filter catches blood clots before they travel to the lungs, which prevents pulmonary embolism. However, the filter does not stop new blood clots from forming. A filter is not usually recommended if you have taken blood thinners.
As you recover from your short-term treatment for VTE, you will need to follow up with your doctor regularly to monitor your condition and discuss whether you need to continue taking blood-thinning medicines. You will also want to take steps to prevent a repeat VTE event and be aware of possible long-term complications. See a doctor or go to the emergency room if you have any signs of excessive bleeding, which can happen if your medicine dose is too high.
Follow your doctor’s instructions and schedule regular appointments.
To monitor your condition, your doctor may recommend the following tests:
When you return home, your doctor may recommend healthy lifestyle changes to help improve your recovery.
Nearly one in three patients who have had VTE will experience a repeat VTE event in the next 10 years. It can take a year or more for clots to break up or stabilize and for blood flow to return to normal. If you were previously treated with blood thinners and experience a repeat VTE event, your doctor may recommend changing your medicine dose or switching you to a different type of blood thinner.
To prevent a repeat VTE event:
Medicines used to treat VTE can thin your blood too much or impair your body’s ability to clot after a wound. If you take a dose of blood-thinning medicine that is too high, it may cause bleeding in the digestive system or in the brain. These side effects can be life threatening.
Signs and symptoms of bleeding in the digestive system include:
Signs and symptoms of bleeding in the brain include:
A lot of bleeding after a fall or injury, or easy bruising or bleeding, may mean that your blood is too thin. Excessive bleeding is bleeding that will not stop after you apply pressure to a wound for 10 minutes. Call your doctor right away if you have any of these signs. If you have severe bleeding, call 9-1-1.
Learn about the following ways the NHLBI continues to translate current research into improved health for people who have VTE. Research on this topic is part of the NHLBI’s broader commitment to advancing scientific discoveries in blood disorders and blood safety.
Learn about some of the pioneering research contributions we have made over the years that have improved clinical care.
In support of our mission, we are committed to advancing VTE research in the following ways.
Learn about exciting research areas the NHLBI is exploring about VTE.
We lead or sponsor many studies on venous thromboembolism, including deep vein thrombosis and pulmonary embolism. See if you or someone you know is eligible to participate in our clinical trials.
After reading our VTE Health Topic, you may be interested in additional information found in the following resources.