Venous Thromboembolism
The risk of developing VTE is highest after major surgery or a major injury, or when you have heart failure, cancer, or a heart attack. Swelling, redness, and pain are some of the signs and symptoms of deep vein thrombosis. A pulmonary embolism can cause sudden chest pain and shortness of breath. Sometimes VTE occurs without any obvious signs. Medicines that help prevent further blood clots from forming or that dissolve serious vein blockages are the main treatments for VTE. Without treatment, VTE can restrict or block blood flow and oxygen, which can damage the body’s tissue or organs. This can be especially serious in the case of a pulmonary embolism, which blocks blood flow to the lungs. If a blood clot is large or there are many clots, a pulmonary embolism can cause death.
Explore this Health Topic to learn more about VTE, including deep vein thromboses and pulmonary embolisms; NHLBI’s role in research and clinical trials to improve health; and where to find more information.
Causes - Venous Thromboembolism
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 - Venous Thromboembolism
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.
Surgery
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.
Other medical conditions
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:
- Spinal cord injury. In addition to damaging veins deep in your body, spinal cord injury may cause paralysis, which can reduce blood flow and raise your risk of VTE. The risk is highest in the first weeks after the injury.
- A broken hip or leg bone or other trauma.
- Cancers such as advanced brain, breast, colon, and pancreatic cancer. Cancer chemotherapy, surgical treatment, and placement of a central venous catheter—a tube inserted into a vein to deliver chemotherapy treatment or other medicine—all increase the risk of VTE. Some cancers release substances that can make it easier for blood to clot. Some cancerous tumors may directly block blood flow by pressing on a vein. A central venous catheter increases the risk for VTE in arm veins, especially in children.
- Heart conditions such as heart attack or congestive heart failure.
- Stroke
- Obesity
- Varicose veins. Most varicose veins do not cause problems, but large, untreated varicose veins can lead to VTE.
- Infections, such as SARS-CoV-2, the virus responsible for COVID-19. Watch our video to learn more about how COVID-19 can lead to a blood clot in the lungs or deep veins, usually in the legs.” Additionally, we offer information and resources on how we are working hard to support necessary COVID-19 research.
- Sickle cell disease. This condition makes the blood clot more easily and can be a risk factor for VTE.
Hormone-based medicines
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.
Surgery
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.
Other medical conditions
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:
- Spinal cord injury. In addition to damaging veins deep in your body, spinal cord injury may cause paralysis, which can reduce blood flow and raise your risk of VTE. The risk is highest in the first weeks after the injury.
- A broken hip or leg bone or other trauma.
- Cancers such as advanced brain, breast, colon, and pancreatic cancer. Cancer chemotherapy, surgical treatment, and placement of a central venous catheter—a tube inserted into a vein to deliver chemotherapy treatment or other medicine—all increase the risk of VTE. Some cancers release substances that can make it easier for blood to clot. Some cancerous tumors may directly block blood flow by pressing on a vein. A central venous catheter increases the risk for VTE in arm veins, especially in children.
- Heart conditions such as heart attack or congestive heart failure.
- Stroke
- Obesity
- Varicose veins. Most varicose veins do not cause problems, but large, untreated varicose veins can lead to VTE.
- Infections, such as SARS-CoV-2, the virus responsible for COVID-19. Watch our video to learn more about how COVID-19 can lead to a blood clot in the lungs or deep veins, usually in the legs.”(Poyiadi, 2020; Llitjos, 2020)
- Sickle cell disease. This condition makes the blood clot more easily and can be a risk factor for VTE.
Pregnancy and giving birth
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.
Not moving for long periods
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.
Age
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.
Family history and genetics
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?
Race or ethnicity
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.
Sex
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.
Screening and Prevention - Venous Thromboembolism
There are no methods to screen for VTE. If you have certain risk factors, such as recent surgery or a major injury, your doctor may start one or more approaches to help prevent a first VTE event.
Prevent a first VTE event
- Venous Thromboembolism
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:
- Movement. Helping your blood circulate makes it harder for clots to form. Your doctor may recommend that you move around as soon as possible after surgery and as you heal. If you cannot get up and walk, try to flex and stretch your feet to improve blood flow in your calves.
- Pressure. Gentle pressure keeps blood from pooling and clotting. Your doctor may recommend applying pressure—for example, by wearing a sleeve or boot that periodically fills with air, or by wearing graduated compression stockings.
- Medicines. Your doctor may give you anticoagulant, or blood-thinning, medicines to prevent clotting. Sometimes this preventive therapy starts before surgery. Or, you may be asked to take a blood thinner during your recovery period at home. These medicines, such as heparin, warfarin, and direct oral anticoagulants, are also used to treat 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.
Look for
- Venous Thromboembolism
- Diagnosis will discuss tests and procedures that your doctor may use to diagnose VTE.
- Life After will explain what your doctor may recommend to prevent your VTE from recurring, getting worse, or causing complications.
- Research for Your Health will discuss how we are using current research and advancing research to prevent VTE.
- Participate in NHLBI Clinical Trials will explain our ongoing clinical studies that are investigating prevention strategies for VTE.
Signs, Symptoms, and Complications - Venous Thromboembolism
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.
Signs and symptoms
- Venous Thromboembolism
Deep vein thrombosis may cause the following to occur around the area of a blood clot:
- Swelling
- Pain or tenderness
- Increased warmth, cramps, or aching in the area that is swollen or painful, usually the calf or thigh
- Red or discolored skin
Signs and symptoms of pulmonary embolism include:
- Shortness of breath
- Pain with deep breathing
- Rapid breathing
- Increased heart rate
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.
Complications
- Venous Thromboembolism
Possible complications of VTE include:
- Post-thrombotic syndrome (PTS), in which poor blood flow, inflammation, and blood vessel damage from deep vein thrombosis cause swelling and discomfort. PTS is a long-lasting condition that can be disabling. With PTS, you may notice swelling, pain, itchiness, or discoloration in the affected area, along with cramping or fatigue. The symptoms may feel worse if you have been on your feet for an extended period. In severe cases, skin sores may develop. Compression stockings may help relieve PTS symptoms.
- Pulmonary hypertension, which occurs when pulmonary embolism blocks blood flow and raises blood pressure in the vessels leading to your lungs. This condition can lead to heart failure. If you develop pulmonary hypertension, you may find it hard to breathe, especially after physical activity, or you may cough up blood, notice swelling, feel tired, have palpitations, or faint. If you still have pulmonary hypertension several months after a VTE event, your doctor may refer you to a specialist to talk about the possibility of surgery to remove a lung clot that has not gone away with treatment.
Look for
- Venous Thromboembolism
Diagnosis - Venous Thromboembolism
Your doctor will diagnose deep vein thrombosis with or without pulmonary embolism based on your medical history, a physical exam, and various imaging or blood test results. Your doctor will identify your risk factors and rule out other causes of your symptoms.
Medical history and physical exam
- Venous Thromboembolism
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:
- Your recent medical history, especially any paralysis or periods of immobilization
- Medicines you are taking
- Recent surgeries or injuries you have had
- Whether you have been treated for cancer
Diagnostic tests and procedures
- Venous Thromboembolism
- D-dimer test to measure a substance in the blood that is released when the fibrin proteins in a blood clot dissolve. If the test shows high levels of the substance, you may have VTE. If your test results are normal and you have few risk factors, you likely do not have VTE.
- Ultrasound to look for deep vein blood clots. This test uses sound waves to create pictures of blood flowing in your veins. The person doing the test may press on your veins to see if they compress normally or if they are stiff with blood clots.
- Computed tomography (CT) angiography to take pictures of your blood vessels and look for blood clots in the lungs and legs. This is the most common diagnostic test for pulmonary embolism.
- Pulmonary angiography to confirm a pulmonary embolism if, after other testing, your doctor suspects you might have one. This test requires inserting a tube into your blood vessel. It also uses X-rays to create video of the blood flow to your lung so your doctor can identify any blood clots.
- Other imaging tests to look at blood flow through your veins, heart function, and lung function if the results of previous tests could not diagnose or rule out VTE. These include venography, echocardiography, ventilation/perfusion scanning, and magnetic resonance imaging (MRI).
Tests for other medical conditions
- Venous Thromboembolism
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:
- Blood tests to check whether you have an inherited blood clotting disorder if you have had repeated blood clots that are not related to another cause. Blood clots in an unusual location, such as the liver, kidney, or brain, may also suggest an inherited clotting disorder. Blood tests can also measure the level of oxygen and other gases in your blood.
- Chest X-ray to give your doctor information about what may be causing your symptoms, such as pneumonia or fluid in the lungs. A chest X-ray does not show whether you have a pulmonary embolism.
- Electrocardiogram (ECG) to identify other conditions that are causing signs of pulmonary embolism. An ECG records the electrical activity of your heart.
Reminders
- Venous Thromboembolism
- Return to Risk Factors to review family history, lifestyle, or other environmental factors that increase your risk of developing clots.
- Return to Signs, Symptoms, and Complications to review common signs and symptoms of VTE.
- Return to Screening and Prevention to review what you can do to prevent clots from forming.
Treatment - Venous Thromboembolism
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.
Medicines
- Venous Thromboembolism
Anticoagulants, or blood thinners, and thrombolytics are medicines commonly used to treat VTE.
- Anticoagulants, or blood thinners, keep blood clots from getting larger and stop new clots from forming. Conventional blood thinners include warfarin and heparin, but newer blood-thinning medicines are also available. To take them, you might get an injection, take a pill, or have an IV tube inserted. Possible side effects include bleeding, especially if you are taking other medicines that also thin your blood, such as aspirin.
- Thrombin inhibitors interfere with the process of clot formation. They may be used for people who cannot take heparin.
- Thrombolytics may be used to dissolve large blood clots that cause severe symptoms or other serious complications. Because thrombolytics can cause sudden bleeding, they are used only for serious and potentially life-threatening VTE events, such as pulmonary embolism.
Catheter-assisted thrombus removal
- Venous Thromboembolism
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.
Vena cava filter
- Venous Thromboembolism
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.
Look for
- Venous Thromboembolism
- Life After will discuss what your doctor may recommend, including lifelong lifestyle changes and medical care to prevent your condition from recurring, getting worse, or causing complications.
- Research for Your Health will explain how we are using current research and advancing research to treat people who have VTE.
- Participate in NHLBI Clinical Trials features ongoing clinical studies that are investigating treatments for VTE.
Life After - Venous Thromboembolism
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.
Receive routine follow-up care
- Venous Thromboembolism
Follow your doctor’s instructions and schedule regular appointments.
- Tell your doctor if symptoms such as pain or swelling continue. Your doctor may prescribe graduated compression stockings to give you relief.
- Take all medicines as prescribed. You will probably keep taking medicines to treat VTE for three months or longer. The most common side effect of blood thinners is bleeding. This side effect can be life-threatening.
- Check your legs for any signs or symptoms of deep vein clotting, such as swollen areas, pain or tenderness, increased warmth in swollen or painful areas, or red or discolored skin. If you think you may have another deep vein clot or are having symptoms of pulmonary embolism, contact your doctor right away.
- Tell your doctor if you notice that you bruise easily; have unexpected bleeding, such as when you floss or go to the toilet; or have unusually heavy menstrual periods.
Monitor your condition
- Venous Thromboembolism
To monitor your condition, your doctor may recommend the following tests:
- Blood tests to monitor the proper dose of medicine so that adjustments can be made as necessary. If you are taking warfarin to treat VTE, you will need to take regular tests that show how long it takes for your blood to clot. Usually, you do these tests at the doctor’s office or at a clinic. The FDA has approved several devices for self-testing. Your doctor may also run regular blood tests to check your kidneys or liver if you have been taking other blood-thinning medicines for more than a year. This will help your doctor make sure your body can still tolerate the medicine well.
- Ultrasounds to monitor your blood clot. These tests will help your doctor see if your blood clot has gotten bigger or has moved.
Healthy lifestyle changes
- Venous Thromboembolism
When you return home, your doctor may recommend healthy lifestyle changes to help improve your recovery.
- Heart-healthy eating. Heart-healthy eating includes limiting the amount of alcohol you drink. Alcohol can also be dangerous if you are taking blood-thinning medicine. If you are taking warfarin, talk with your doctor about your eating patterns and any supplements you take. Foods that contain vitamin K can affect how well warfarin works, so it is important to eat about the same amount of vitamin K each day. Vitamin K is found in green leafy vegetables and some oils, such as canola and soybean oils.
- Being physically active. It is important to keep moving regularly while you are healing. Ask your medical care team when you can start being physically active and how much activity is appropriate.
- Aiming for a healthy weight. If you are overweight or have obesity, you can improve your health by aiming for a healthy weight. Obesity is a risk factor for a repeat VTE event.
- Managing stress. Stress can increase the risk of other conditions that can lead to VTE, such as heart attack and stroke.
- Quitting smoking. Smoking also increases the risk of heart attack and stroke, and it may aggravate other factors known to raise the risk of VTE. Visit Smoking and Your Heart and the National Heart, Lung, and Blood Institute’s Your Guide to a Healthy Heart. For free help quitting smoking, you may call the National Cancer Institute’s Smoking Quitline at 1-877-44U-QUIT (1-877-448-7848).
Prevent a repeat VTE event
- Venous Thromboembolism
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:
- See your doctor for regular checkups and follow-up tests and treatment.
- Talk to your doctor about your risk for a repeat VTE event. The risk of a repeat VTE is higher for African Americans and Hispanic Americans than it is for white Americans. It is also higher for men than for women.
- Take all medicines as your doctor prescribes. A repeat event while you are taking medicines is rare, but if it does occur, your doctor may switch your medicine or increase the dose.
- If you stop taking blood-thinning medicines, your doctor may suggest that you take aspirin to reduce the risk of getting another clot.
Learn the warning signs of serious complications and have a plan
- Venous Thromboembolism
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:
- Bright red vomit or vomit that looks like coffee grounds
- Bright red blood in your stool or black, tarry stools
- Pain in your abdomen
Signs and symptoms of bleeding in the brain include:
- Severe pain in your head
- Sudden changes in your vision
- Sudden inability to move your legs or arms
- Memory loss or confusion
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.
Research for Your Health
The NHLBI is part of the U.S. Department of Health and Human Services’ National Institutes of Health (NIH)—the Nation’s biomedical research agency that makes important scientific discovery to improve health and save lives. We are committed to advancing science and translating discoveries into clinical practice to promote the prevention and treatment of heart, lung, blood, and sleep disorders, including VTE. Learn about current and future NHLBI efforts to improve health through research and scientific discovery.
Improving health with current research
- Venous Thromboembolism
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.
- Surgeon General’s Call to Action to Prevent Deep Vein Thrombosis and Pulmonary Embolism. With the Surgeon General’s office, the NHLBI drafted a call to action summarizing research on VTE and focusing the attention of stakeholders and the public on the importance of saving lives and reducing the burden of VTE.
- Advances in VTE diagnosis. Clinical trials led by the NHLBI have led to important advances in clinical care. The Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study, originally launched in the 1980s, has tested the accuracy of several technologies used to diagnose pulmonary embolism. Based on the findings of the second phase of this study, investigators issued recommendations. PIOPED research continues, with the aim of finding safer and less expensive approaches to reliably assess patients.
- Enhancing the translation of research discoveries into improved prevention and treatment of VTE. The NHLBI funds cooperative agreements for research centers to participate in the Translational Research Centers in Thrombotic and Hemostatic Disorders (TRC-THD) program. The individual centers address important clinical questions through research and collaboration with other centers to improve diagnostic tools and treatments for patients who have VTE.
- Enabling progress in thrombosis research and clinical care through trans-NHLBI and trans-NIH working groups. We regularly convene working groups of experts to discuss where there are gaps in our understanding of VTE. The NHLBI helps identify areas where doctors need more evidence to help make decisions about patients in their care and funds studies to help find the answers. We have organized research meetings around thrombosis in people who have congenital heart disease or cancer, as well as meetings on pulmonary embolism complications such as pulmonary hypertension, how to tailor antithrombotic treatments, and the risk of clotting with heart pumps known as ventricular assist devices.
Learn about some of the pioneering research contributions we have made over the years that have improved clinical care.
- Women receiving hormone therapy have a higher risk of VTE. The Women’s Health Initiative (WHI) is one of the largest women’s health projects ever launched in the United States, having enrolled more than 161,000 women at 40 clinical centers. The WHI found that the use of estrogen plus progestin hormone therapy after menopause increased the risk for blood clots.
- Lifestyle factors can increase the risk of VTE. The goal of the NHLBI’s Atherosclerosis Risk in Communities (ARIC) study is to investigate the causes of atherosclerosis, a disease marked by plaque build-up in the arteries, and the clinical outcomes in adults from four U.S. communities. ARIC has enrolled approximately 16,000 adults and has monitored them for 30 years. The study produced some of the first evidence that lifestyle factors contribute to the risk of VTE, offering possible keys to prevention.
- Research investigates whether a patient’s genetic information improves warfarin dosing. Our genes influence how the body makes use of blood thinning medicines. Several NHLBI studies researched how to personalize VTE medicine dosing, based on a patient’s genes, to help determine a more accurate initial dose of blood thinning medicine for each patient. In NHLBI’s Clarification of Optimal Anticoagulation through Genetics (COAG) study, researchers found that the approach that used the patient’s genetic information was no better than the standard approach at predicting the right dosage. Their results also showed that the genetic information approach did not close a gap in treatment effectiveness between white and African American patients. Read Genetic data does not improve anticoagulation control with warfarin to learn more about the COAG study. In the NHLBI Genetic Informatics Trial (GIFT), researchers found that personalizing warfarin dosing based on a patient’s genetics did reduce the risk of blood clots in patients who were undergoing hip or knee surgery. Read Precision Medicine: Making Warfarin Safer to learn more about the GIFT study.
- Recurrence of VTE prevented by low doses of blood thinner. Early results from our Prevention of Recurrent VTE (PREVENT) study found that after their initial treatment, VTE patients who continued taking a low dose of the blood thinner warfarin had a 64 percent lower risk of a recurrence than participants who received a placebo.
- Research provides evidence to improve medicines for VTE. Launched in 2014, the Vascular Interventions/Innovations and Therapeutic Advances (VITA) Program supports research to develop new medicines that doctors can use to break up blood clots without increasing bleeding. VITA is a translational program that supports and accelerates the early-stage development of promising tests and treatments. VITA seeks to address unmet clinical needs for vascular disease, particularly in underserved communities.
- Research investigates whether bridging treatment before and after surgery is necessary to prevent blood clots. For patients with atrial fibrillation who take warfarin and need surgery, doctors stopped treatment five days before surgery and for up to 10 days after surgery. These patients received medicine to bridge that gap in treatment and prevent blood clots. The NHLBI Bridging Anticoagulation in Patients who Require Temporary Interruption of Warfarin Therapy for an Elective Invasive Procedure or Surgery (BRIDGE) trial found no difference in the risk for blood clots in patients who received bridging treatment and those who did not. Read Study indicates blood thinners may not be needed during surgery in atrial fibrillation to learn more about the BRIDGE trial.
- Research investigates new treatment approaches. The NHLBI supports the Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT) study to evaluate the use of medicine delivered directly to a clot to prevent post-thrombotic syndrome. In 2017, researchers found that adding this invasive approach was no more effective than using blood thinners alone.
Advancing research for improved health
- Venous Thromboembolism
In support of our mission, we are committed to advancing VTE research in the following ways.
- We perform research. Our Division of Intramural Research includes some of the investigators at NHLBI who are actively engaged in research on VTE.
- We fund research. Our Division of Blood Diseases and Resources (DBDR) and Division of Lung Diseases (DLD) fund research on VTE. DBDR-supported research improves our understanding of normal and abnormal blood, blood clotting, and blood flow. It also supports scientific advances in biomarkers to diagnose blood conditions and in therapeutics to treat them. The DLD funds research on the causes, diagnosis, prevention, and treatment of lung diseases. Its Lung Vascular Biology Program supports research on pulmonary embolism, including understanding how the condition develops. Search the NIH RePORTer to learn about research the NHLBI is funding on VTE.
- We stimulate high-impact research. Our Trans-Omics for Precision Medicine (TOPMed) program includes participants with pulmonary embolism and deep vein thrombosis, which may help us understand how genes contribute to differences in disease severity and how patients respond to treatment. The NHLBI Strategic Vision highlights ways we may support research over the next decade.
Learn about exciting research areas the NHLBI is exploring about VTE.
- Advancing understanding to improve patient care. We are committed to supporting research to improve VTE prevention and treatment. This includes developing tests that better identify patients who are at risk of VTE, improving the use of new blood-thinning medicines, finding out if the timing of treatment influences its effectiveness, and reducing clotting complications with heart pumps.
- Exploring interactions between cancer and VTE. We support research to improve understanding about the relationship between cancer and thrombosis. Research can help us determine who is at risk. Understanding how medicines for VTE can affect cancer progression and treatment is another priority. The Consortium Linking Oncology with Thrombosis (CLOT) will support these efforts.
- Expanding our understanding of how sex hormone levels affect a woman’s risk of VTE. Building on the legacy of the Women’s Health Initiative, we support research to understand better how hormones affect clotting. Experts at a 2012 meeting organized by the NHLBI identified research priorities that guide these efforts today. This includes investigating clotting disorders in pregnant women that developed after taking hormone-based therapies such as oral contraceptives, or after undergoing fertility treatments.
- Refining our ability to predict and improve outcomes. Ongoing research includes efforts to further define factors that put patients at risk of developing a blockage, identify which patients are most at risk of developing repeat pulmonary embolism, prevent VTE in cancer patients, and test new medicines to prevent or treat blood clots.
Participate in NHLBI Clinical Trials
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.
Do you know someone being treated for cancer who may be at risk for VTE?
Were you or your child recently diagnosed with VTE?
Was your child recently diagnosed with DVT?
Do you know a child or young adult recently treated for VTE?
Learn more about participating in a clinical trial.
View all trials from ClinicalTrials.gov.
More Information
After reading our VTE Health Topic, you may be interested in additional information found in the following resources.
Related Health Topics
NHLBI resources
- Venous Thromboembolism
- Atherosclerotic Risk in Communities (ARIC Study)
- Blood Disorders and Blood Safety
- Clarification of Optimal Anticoagulation through Genetics (COAG) Study
- Trans-Omics for Precision Medicine (TOPMed) Program
- Vascular Interventions/Innovations and Therapeutic Advances (VITA) Program.
- Women’s Health Initiative
Non-NHLBI resources
- Venous Thromboembolism
- Blood Clots that Kill: Preventing DVT (National Library of Medicine [NLM], MedlinePlus)
- Deep Vein Thrombosis (NLM, MedlinePlus)
- Pulmonary Embolism (NLM, MedlinePlus)
- Venous Thromboembolism (Blood Clots) (Centers for Disease Control and Prevention)
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