Thrombosis (Blood Clot)
A blood clot blocking a vein or artery
Quick Facts
- Type: Cardiovascular condition
- Main types: Venous and arterial thrombosis
- Key danger: Clot fragments traveling to lungs or brain
- Seek emergency care: Chest pain, breathlessness, stroke signs
Overview
Thrombosis is the formation of a blood clot (thrombus) inside a blood vessel. Clotting is a normal, life-saving process that stops bleeding from a wound, but when a clot forms inside an intact vessel it can dangerously block blood flow.
Doctors distinguish two broad types. Venous thrombosis forms in veins, most often the deep veins of the legs (deep vein thrombosis), and a piece can break off and lodge in the lungs as a pulmonary embolism. Arterial thrombosis forms in arteries and can cut off blood supply to the heart (causing a heart attack) or brain (causing a stroke). Recognizing the warning signs and seeking care quickly is critical because complications can be life-threatening.
Symptoms
Symptoms depend on where the clot forms and what it blocks.
- Deep vein thrombosis (leg): Swelling, pain or tenderness, warmth, and redness, usually in one leg.
- Pulmonary embolism (lung): Sudden shortness of breath, sharp chest pain that worsens with breathing, rapid heartbeat, and sometimes coughing up blood.
- Arterial clot to the brain (stroke): Sudden weakness or numbness on one side, facial drooping, slurred speech, or vision loss.
- Arterial clot to the heart (heart attack): Chest pressure or pain, often spreading to the arm or jaw, with sweating or breathlessness.
Sudden breathlessness, chest pain, or stroke-like symptoms are medical emergencies. Call emergency services immediately.
Causes
Clots tend to form when blood flow slows, the vessel wall is damaged, or blood clots more easily than normal. Common contributors include:
- Immobility: Long bed rest, recovery from surgery, or long flights that slow blood flow in the legs.
- Vessel damage: Injury, surgery, or fatty plaque buildup (atherosclerosis) in arteries.
- Increased clotting tendency: Inherited clotting disorders, cancer, pregnancy, and some hormone medications.
- Atrial fibrillation: An irregular heartbeat that lets clots form in the heart and travel to the brain.
Risk Factors
- Recent surgery, hospitalization, or prolonged immobility
- A personal or family history of blood clots
- Cancer and some cancer treatments
- Pregnancy and the weeks after childbirth
- Estrogen-containing birth control or hormone therapy
- Obesity, smoking, and older age
- Inherited clotting disorders such as factor V Leiden
Diagnosis
Doctors use a combination of examination, blood tests, and imaging:
- Ultrasound: The main test for diagnosing deep vein thrombosis in the legs.
- CT pulmonary angiography: A scan that shows clots in the lungs.
- D-dimer blood test: Helps rule out clotting in lower-risk patients.
- ECG and imaging of the heart or brain: Used when a heart attack or stroke is suspected.
Treatment
Treatment aims to stop the clot from growing, prevent it from traveling, and lower the risk of new clots:
- Anticoagulants (blood thinners): The mainstay of treatment for venous clots, given by injection or as tablets.
- Clot-dissolving drugs: Used for large or life-threatening clots, such as a major pulmonary embolism or some strokes and heart attacks.
- Procedures: Catheter-based clot removal or, in selected cases, a filter placed in a large vein.
- Treating the cause: Controlling atrial fibrillation, managing atherosclerosis, and addressing other risk factors.
Prevention
- Move and stretch your legs during long trips and after surgery
- Stay well hydrated and avoid prolonged immobility
- Take prescribed blood thinners or wear compression stockings if advised after surgery
- Stop smoking and maintain a healthy weight
- Manage conditions like atrial fibrillation and high cholesterol
When to See a Doctor
Call emergency services immediately for:
- Sudden shortness of breath or sharp chest pain
- Coughing up blood
- Sudden weakness, numbness, facial drooping, or slurred speech (signs of stroke)
- Chest pressure spreading to the arm or jaw with sweating (signs of heart attack)
See a doctor promptly for new leg swelling, pain, warmth, or redness, especially in one leg.
Frequently Asked Questions
What are the warning signs of a dangerous blood clot?
Sudden shortness of breath, sharp chest pain that worsens with breathing, coughing up blood, or stroke-like symptoms such as one-sided weakness and slurred speech are emergencies. Leg swelling, pain, and warmth in one leg also need prompt evaluation. Call emergency services for the urgent symptoms.
What is the difference between a venous and an arterial clot?
Venous clots form in veins, often in the legs, and can travel to the lungs. Arterial clots form in arteries and can block blood supply to the heart or brain, causing a heart attack or stroke. Both are serious and need urgent care.
Why do clots form during long flights or bed rest?
Sitting still for long periods slows blood flow in the leg veins, which makes clotting more likely. Moving your legs, walking periodically, and staying hydrated reduce the risk.
Can blood clots be prevented?
Often, yes. Staying active, moving during long trips, managing weight and smoking, and taking prescribed blood thinners or wearing compression stockings after surgery all lower the risk.
How are blood clots treated?
Most venous clots are treated with anticoagulant medicines (blood thinners) that stop the clot from growing and prevent new ones. Large or dangerous clots may need clot-dissolving drugs or a procedure to remove them.
References
- Centers for Disease Control and Prevention (CDC). Venous Thromboembolism (Blood Clots).
- National Heart, Lung, and Blood Institute (NHLBI). Venous Thromboembolism.
- Mayo Clinic. Deep vein thrombosis (DVT).
- MedlinePlus, U.S. National Library of Medicine. Blood clots.