Venous Thromboembolism: The Silent Clot That Can Change a Life

Each year, as many as 900,000 Americans develop a venous thromboembolism, according to the Centers for Disease Control (CDC). Tens of thousands die from it, often suddenly and often before anyone recognizes the cause. Many who survive live with leg pain, swelling, and skin changes that never fully resolve.

Venous thromboembolism (VTE) is common. It is frequently silent. And in a significant number of cases, it is preventable. Knowing how these clots form, who is most at risk, and which symptoms require immediate attention can change the outcome.

What Is Venous Thromboembolism?

Venous thromboembolism refers to a blood clot that forms in a vein. It takes two forms.

• Deep vein thrombosis (DVT): a clot in a deep vein, most often in the leg or pelvis, though it can also occur in the arm.
• Pulmonary embolism (PE): part of that clot breaks loose, travels through the bloodstream, and lodges in the lungs, blocking blood flow. This is a medical emergency.

DVT and PE are not separate diseases. They are two manifestations of the same underlying condition. The study "Epidemiology of Venous Thromboembolism," reported in Circulation, found that approximately one third of patients with symptomatic VTE present as pulmonary embolism, while two thirds present as deep vein thrombosis alone.

Silent, symptomless clots are common enough that a PE is sometimes the first sign anything is wrong. A clot can sit in a deep leg vein for days without producing pain or swelling severe enough to send anyone to a doctor.

Who Is at Risk?

Clots develop when one or more elements of Virchow’s triad are present:

• Slowed blood flow, known as venous stasis
• Injury to the wall of the blood vessel
• An increased tendency for the blood to clot, known as hypercoagulability

Most clinical risk factors trace back to one of those three mechanisms. Common ones include:

• Recent surgery, particularly orthopedic and abdominal procedures
• Hospitalization or an extended illness
• Cancer and certain cancer treatments
• Pregnancy and the postpartum period
• Hormonal therapy or birth control pills
• Long-distance travel or prolonged immobility
• Obesity
• Smoking
• Increasing age
• A previous DVT or PE
• Inherited clotting disorders or a strong family history of clots

These risks are cumulative. A single factor may raise risk only modestly, while several together can raise it substantially. Age matters more than most patients expect, with 60 percent of all VTE events occurring in those 70 years and older, according to the Journal of Thrombosis and Haemostasis.

What Are the Symptoms of a Blood Clot?

Deep Vein Thrombosis
Symptoms of a DVT typically affect one limb and may include:

• Swelling in one leg
• Calf pain or tenderness
• Warmth over the affected area
• Redness or discoloration
• A sensation of tightness or heaviness

Roughly half of DVTs produce few symptoms or none at all. Symptoms alone are also not specific to clots. Leg swelling and calf pain can point to cellulitis, a Baker’s cyst, a muscle injury, or lymphedema. That overlap is exactly why imaging matters.

Are you concerned about a possible blood clot? CVR offers a DVT rule-out service for individuals who suspect they have a DVT. This comprehensive approach includes a scan, anticoagulation treatment, education, and follow-up if necessary. Contact the DVT hotline at 877-SCAN-DVT (877-722-6388) for more information and to schedule an appointment.

Pulmonary Embolism
A pulmonary embolism may present with:

• Sudden shortness of breath
• Chest pain, often sharper with a deep breath
• Rapid heartbeat
• Lightheadedness or fainting
• Cough, sometimes producing blood
• Sweating

NOTE: A suspected PE requires emergency evaluation. Call 911 rather than driving yourself or waiting for an office appointment.

How Is Venous Thromboembolism Diagnosed?

Evaluation is built in layers, starting with the clinical picture and moving to imaging when the risk warrants it.

• Clinical risk assessment, using validated scoring tools to estimate the likelihood of a clot
• D-dimer blood testing in selected patients, which is most useful for ruling a clot out when suspicion is low
• Venous duplex ultrasound, the standard imaging test for DVT
• CT pulmonary angiography, the first-choice imaging test for suspected PE
• Ventilation-perfusion (V/Q) scanning when CT contrast is not appropriate, such as in pregnancy or kidney impairment

How Is Venous Thromboembolism Treated?

Treatment depends on the size and location of the clot, the severity of symptoms, and the patient’s overall health. Options include:

• Anticoagulation. Blood thinners are the foundation of treatment. They do not dissolve an existing clot. They stop it from growing and prevent new clots from forming while the body breaks the clot down on its own. Most patients take them for at least three months, and some longer.
• Catheter-directed thrombolysis or thrombectomy. In selected patients with large or severely symptomatic clots, a catheter is threaded directly to the clot to deliver clot-dissolving medication or remove the clot mechanically.
• Inferior vena cava (IVC) filters. Used in carefully selected situations, most often when a patient cannot safely take anticoagulants.
• Compression therapy. Graduated compression stockings reduce swelling and heaviness and support the leg during recovery.
• Early mobilization. Walking is encouraged once treatment has begun and it is safe to do so.

Why Early Diagnosis Matters

A DVT is not a temporary inconvenience that resolves on its own.

Left untreated, a clot can enlarge or break loose and travel to the lungs. Even after successful treatment, a clot can permanently damage the one-way valves inside the leg veins or leave behind residual blockage. Either outcome allows blood to pool in the leg, a condition called post-thrombotic syndrome.

Post-thrombotic syndrome develops in up to half of people who have had a DVT, including those who received appropriate anticoagulation. Its features include:

• Persistent leg swelling
• Aching or heaviness that worsens through the day
• Skin discoloration and texture changes around the ankle
• Venous ulcers in severe cases

There is also the question of what comes next. Anyone who has had one episode of DVT carries an elevated risk of having another, which is why treatment duration, follow-up, and long-term risk assessment are part of the conversation rather than an afterthought.

The sooner it's caught and treated, the lower these risks become. Wait too long, and the risks climb.

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Can Blood Clots Be Prevented?

Many VTEs can be prevented, and most of the measures are straightforward.

• Move regularly during long trips. Walk the aisle when it is safe, stop the car periodically, and perform calf pumps and ankle circles while seated.
• Stay well hydrated, particularly during air travel.
• Get your legs moving after surgery or illness, as early as your care team allows.
• Wear compression stockings when they are recommended for you.
• Take prescribed blood thinners after certain surgeries or during other high-risk periods, exactly as directed.

Prevention is not one-size-fits-all. Current hematology guidelines reserve compression stockings and preventive anticoagulation for travelers at elevated risk on trips longer than four hours, and do not recommend routine prophylaxis for travelers without risk factors. If you have a personal or family history of blood clots, discuss your risk with your physician before surgery, extended travel, or starting hormone therapy.

When Should You Seek Medical Care for a Blood Clot?

Timing matters with blood clots, and knowing which symptoms call for a phone call versus a 911 call can change the outcome.

If you notice the leg symptoms described above, such as new swelling, pain, or discoloration in one limb, contact your physician or CVR promptly for evaluation. These signs are not an emergency on their own, but they should be checked without delay.

If you have any of the pulmonary embolism symptoms above, including sudden shortness of breath, chest pain, or coughing up blood, treat it as an emergency. Call 911 right away rather than driving yourself or waiting for an appointment. A clot in the lungs can become life-threatening quickly, and minutes count.

Understanding Your Blood Clot Risk: When to See a Vein Specialist

Venous thromboembolism is common, potentially life-threatening, and often preventable. Knowing the risk factors and spotting the early symptoms can be the difference between a routine recovery and a medical emergency. If you have leg swelling, unexplained leg pain, a history of blood clots, or other risk factors for venous disease, an evaluation with a board-certified vein specialist can clarify your risk and guide the right testing and treatment.

Frequently Asked Questions

Q: Can a blood clot go away on its own?
A: The body does slowly break down clots over time, but that is not a reason to leave one untreated. Without treatment, a clot can grow or break loose before your body clears it, which is why evaluation matters even when symptoms feel mild.

Q: Is it safe to travel or fly after having a DVT?
A: Travel is often fine once your treatment is underway and your care team says the timing is right, but that varies from person to person. If you have had a recent clot, check with your physician before a long trip so you can plan the right precautions.

Q: Can young, healthy people get blood clots?
A: Yes. Age raises the risk, but clots can still affect younger adults, especially with triggers like surgery, pregnancy, birth control, long travel, or an inherited clotting disorder.

Q: Should I stop my birth control if I am worried about clots?
A: Estrogen-containing birth control does raise clot risk somewhat, but stopping any medication is a decision to make with your doctor rather than on your own. Your physician can weigh your personal risk factors and help you find the safest option.

Q: Will I have to take blood thinners for the rest of my life?
A: Not always. Many people take them for a few months after a clot, while those with ongoing risk factors or an unexplained clot may need them longer, which is something your care team decides based on your individual risk.