VTE stands for venous thromboembolism, a condition where a blood clot forms in a vein. It affects up to 900,000 people in the United States each year and causes an estimated 60,000 to 100,000 deaths annually. VTE is actually an umbrella term that covers two related conditions: deep vein thrombosis (DVT), where a clot forms in a deep vein, and pulmonary embolism (PE), where a clot travels to the lungs.
How DVT and PE Are Connected
Deep vein thrombosis typically starts in the lower leg, thigh, or pelvis. A clot forms in one of the deep veins, partially or fully blocking blood flow. If that clot breaks loose, it can travel through the bloodstream and lodge in the blood vessels of the lungs. That’s a pulmonary embolism, and it’s the more immediately dangerous form of VTE because it can cut off blood supply to lung tissue.
Not every DVT leads to a PE, but every PE starts somewhere else in the body, usually as a DVT. This is why the two conditions are grouped under the single term VTE: they represent different stages of the same underlying problem.
What Causes Blood Clots to Form
Three conditions make clots more likely to develop in veins. The first is slow or stagnant blood flow, which happens during long periods of immobility like bed rest, long flights, or sitting for hours after surgery. The second is damage to the inner lining of a blood vessel, which can result from injury, surgery, or inflammation. The third is blood that clots more easily than normal, a state that can be triggered by genetics, certain medications, or conditions like cancer.
Most cases of VTE involve at least one of these three factors. Often two or three overlap. Someone recovering from hip surgery, for instance, has vessel damage from the procedure, reduced blood flow from limited movement, and potentially an inflammatory state that makes blood stickier.
Risk Factors
Some risk factors are situational. Surgery, trauma, broken bones, hospitalization, pregnancy, and long-distance travel all temporarily increase VTE risk. Cancer is one of the strongest triggers, both because tumors release substances that promote clotting and because cancer treatment often involves surgery and extended bed rest. Acute infections and the use of central venous catheters also raise the risk.
Other risk factors are more persistent. Obesity roughly doubles the odds of VTE. Oral contraceptives and hormone replacement therapy increase clotting tendency. Older age, high blood pressure, and diabetes are also associated with higher risk. A sedentary lifestyle, independent of any acute illness, contributes as well. Some people carry inherited genetic variants that make their blood clot more readily, which can make even minor triggers enough to cause a clot.
Symptoms of DVT
A blood clot in a deep vein typically causes swelling in one leg, along with pain or cramping that often starts in the calf. The skin over the affected area may feel warm and look red or purple. These symptoms tend to develop gradually and worsen over hours to days. Some DVTs, however, produce no noticeable symptoms at all, which is part of what makes VTE dangerous.
Symptoms of Pulmonary Embolism
A pulmonary embolism feels very different. The hallmark symptom is sudden shortness of breath that comes on without explanation. Chest pain that worsens with deep breathing or coughing is common. Other signs include a rapid pulse, rapid breathing, lightheadedness, fainting, and coughing up blood. A large PE can be life-threatening within minutes, making it a medical emergency.
How VTE Is Diagnosed
When a doctor suspects DVT, the first step is often a blood test that measures a substance released when clots break down. If that test comes back negative, it’s a strong signal that no significant clot is present. If the result is positive or borderline, the next step is a duplex ultrasound, which uses sound waves to visualize blood flow in the deep veins and can identify blockages. This is the standard imaging test for DVT.
For a suspected pulmonary embolism, the standard test is a specialized CT scan that uses contrast dye injected into a vein to create detailed images of the blood vessels in the lungs. In patients who can’t undergo this scan (due to kidney problems or dye allergies, for example), an alternative imaging test compares airflow and blood flow patterns in the lungs to detect mismatches caused by clots.
Treatment
Blood-thinning medications are the primary treatment for nearly all cases of DVT and PE. These drugs don’t dissolve existing clots, but they prevent clots from growing and stop new ones from forming, giving the body time to gradually break down the clot on its own. The standard treatment duration is three to six months, though this varies based on the size of the clot, the underlying cause, and whether the patient has had VTE before.
Newer oral blood thinners have largely replaced older options like warfarin for most patients. These newer medications carry a lower risk of serious bleeding complications, particularly bleeding in the brain, and they don’t require the regular blood monitoring that warfarin demands. Studies comparing the two approaches have found that the newer drugs are associated with fewer recurrent clots during extended treatment, which is why major medical guidelines now recommend them as the first choice.
Some patients with recurrent VTE or identifiable ongoing risk factors may need to stay on blood thinners indefinitely. The decision to extend treatment beyond six months involves weighing the risk of another clot against the risk of bleeding from continued medication.
Prevention in Hospitals
Because hospitalized patients face elevated VTE risk from immobility and acute illness, prevention is a routine part of hospital care. For patients at meaningful risk, injectable blood thinners given once daily are the standard preventive measure. Mechanical options like compression sleeves that intermittently squeeze the legs to keep blood moving are used for patients who can’t safely take blood thinners. For low-risk patients, neither approach is necessary.
Long-Term Complications
VTE doesn’t always end when the acute clot resolves. After a DVT, damaged vein valves can cause chronic swelling, pain, and skin changes in the affected leg, a condition sometimes called post-thrombotic syndrome. After a pulmonary embolism, roughly half of survivors report persistent shortness of breath, reduced exercise tolerance, or decreased quality of life. One large study found that over 56% of PE patients had ongoing symptoms at follow-up.
The most severe long-term complication of PE is chronic thromboembolic pulmonary hypertension, where unresolved clot material in the lung arteries leads to permanently elevated blood pressure in the lungs. This is relatively rare, occurring in an estimated 0.5 to 3.8% of PE survivors, but it can cause progressive heart failure if untreated. Between 29 and 38% of PE patients have residual blockages in their lung blood vessels even after treatment, though not all of these cause symptoms.