Every cell in your body thrives on the oxygen and nourishment blood provides, so when circulation is slowed down or blocked, trouble is usually not far behind. Blood clots within blood vessels can weaken and cut off blood flow altogether. Their impact and severity depend on their size and shape and where they’re located. One variety, known as venous thromboembolism (VTE), affects an estimated 900,000 Americans each year, according to the CDC, and as many as 60,000 to 100,000 victims don’t survive.
It’s important to know how to recognize a potentially dangerous blood clot so you can get prompt treatment. Moreover, taking some simple steps can help minimize your risk for these blood blockers.
Clotting gone wrong
In most people blood clotting happens naturally anytime a blood vessel is injured, such as when you get a cut or a bruise. To prevent excessive bleeding, blood cells called platelets combine with other proteins to form a gel-like clot over the injury, a process known as coagulation. After the injury heals, the clot dissolves naturally.
Sometimes, however, the normal blood clotting process can go awry. A blood clot becomes a concern when it forms within a blood vessel in the absence of an injury and the clot fails to go away on its own. An abnormal clot formation in a vein is called venous thrombosis, or a venous blood clot. (Blood clots can also form in the arteries, usually as a result of atherosclerosis, which occurs when cholesterol and other substances form waxy deposits called plaques within the walls of arteries, causing them to narrow. This form of blood clot can lead to heart attacks and strokes.)
The most common type of venous thrombosis is deep vein thrombosis (DVT), in which blood clots form in a vein set far beneath the skin. While these clots can form anywhere in the body, they most commonly occur in the calf, thigh, or pelvis. If one or more of the clots break loose and travel through the bloodstream to the lungs, they can become lodged and block blood flow. This is called a pulmonary embolism (PE), and it can be a life-threatening emergency.
Risk factors and causes
Your likelihood of having a venous blood clot rises as you age. Anyone can develop one, but African Americans have the highest risk of any racial group in the United States. And if you’ve had a past episode of DVT or PE, there’s a roughly one in three chance you’ll have another within the next decade.
Risk factors like obesity and smoking appear to promote venous blood clots, too. Other influences that raise your risk include:
- Prolonged immobility. Moving around gets your blood pumping, while being inactive for long stretches slows the flow, making it easier for clots to form, especially in the veins of the calves. People who have a leg in a cast, have had a stroke and are paralyzed, or are confined to long-term bed rest for any other reason have an increased risk for blood clots. Even sitting for an extended period, such as on a long flight, can put you at risk.
- Surgery. DVT is a common complication following surgery (see inset at end of article), and the risk for it rises after age 40. The risk for VTE is particularly heightened if you undergo a procedure involving the legs and hips, such as joint replacement surgery, though other operations can trigger blood clots, too. Being immobile after surgery contributes to risk as well.
- Trauma. Any serious injury, such as a broken hip, leg, or pelvis; a spinal cord injury; or any other form of trauma that results in extended immobility can make you more susceptible to blood clots.
- Cancer. Having cancer increases the risk for DVT, especially if you develop certain types of malignancies (see inset below).
- Hormones. Women who use menopausal hormone therapy or birth control pills that contain estrogen increase their risk for blood clots. And recent research suggests that taking testosterone may more than double a man’s risk for VTE.
- Heart failure. A weakened or damaged heart can’t pump enough blood, allowing clots to form.
- Inflammatory bowel disease. Studies have shown that VTEs are more common in people who have the digestive disorders Crohn’s disease and ulcerative colitis.
- Your genes. Between 5 and 8 percent of the U.S. population carries inherited gene mutations that cause blood to have an increased tendency to form clots. Being born with one of these gene defects can make you up to 8.5 times more likely to develop a blood clot compared to someone who lacks one of the mutations.
Cancer and Blood Clots: How They’re Linked
Having cancer increases your risk for blood clots in several ways. And if your cancer requires surgery, that raises your clotting risk as well.
Symptoms and warning signs
Some blood clots cause no symptoms, at least initially. However, the clots will often cause pain and swelling at the site (usually on a leg) where they’ve formed. The skin may feel warm and turn red or even purple or blue. The onset of symptoms is usually gradual, but you should contact your doctor about them promptly.
The symptoms of PE are quite different. You may feel short of breath or have rapid breathing. Deep breaths may cause sharp pain in your chest, and you could develop a cough (which may produce blood) or a rapid heartbeat. You may feel dizzy or faint. If you experience any of these symptoms, seek medical help immediately.
Diagnosis and treatment
In addition to taking a medical history, performing a physical exam, and considering your symptoms, a doctor will use certain tools to diagnose a blood clot. A blood test can measure a substance called D-dimer that rises in the presence of blood clots, though additional tests may be used. Positive results are confirmed with imaging tests. Doppler ultrasound is typically used to diagnose DVT, while computed tomography (CT) angiography is the usual choice for identifying a suspected PE and blockages in thearteries.
Doctors almost always treat VTE with an anticoagulant (“blood thinner”) given as either a pill, an injection, or an infusion, depending on the circumstances and the particular anticoagulant used. Anticoagulants help stop a blood clot from worsening and help prevent new ones from forming. More serious cases may require treatment with “clot-busting” therapy known as thrombolysis.
Some VTE patients also require placement of a device called an inferior vena cava filter in the large vein that runs from the lower body to the heart to block blood clots from traveling from the legs to the lungs.
Cut your venous clot risk
Most people who develop blood clots have more than one risk factor. There are some risk factors you can’t change, such as having a personal or family history of blood clots or being 60 or older. But there are other risk factors you can control. Consider taking the following measures to limit your risk of developing a blood clot:
- Practice a healthy lifestyle: Lose excess weight; cut back on salt; avoid tobacco; and get regular exercise, such as walking, dancing, swimming, or bike riding.
- Stay hydrated: Dehydration causes the blood vessels to narrow and the blood to thicken, which increases clot risk.
- Wear loose-fitting clothing around the legs and waist.
- Avoid tight socks or stockings unless your doctor has recommended that you wear compression stockings, which improve blood flow and reduce swelling and pain. Compression stockings can also help stop blood from pooling and clotting, such as after surgery or during long flights.
- Try not to remain seated for more than 20 minutes without changing position or getting up and moving around—even if you’re on a plane or a train.
- When you do sit, avoid crossing your legs, which inhibits blood flow. Try to keep your legs elevated if possible, occasionally stretching them and flexing your feet.
- If you can’t get up to move around, try to exercise your legs while you’re sitting: Lift your heels up and down while keeping your toes on the floor, raise and lower your toes while keeping your heels on the floor, and tighten and release your leg muscles.
- If you’re driving a long distance, make frequent pit stops to get out of the car and walk around.
- If you’re confined to bed, consider elevating the foot of your bed four to six inches or using a pillow or wedge specifically designed to elevate the legs.
Tips for Preventing Blood Clots After Surgery
If you need to undergo surgery, be sure to talk with your doctor about guarding against blood clots after the procedure. Several simple measures can help prevent such clots, known as postsurgical venous thromboembolism.
This article first appeared in the February 2020 issue of UC Berkeley Health After 50.
Published February 20, 2020