What is deep vein thrombosis?
Deep Vein Thrombosis, or DVT, is the formation of one or more blood clots in the body's large veins, usually in the lower leg or calf. These clots can partially or completely block the vein, causing pain, swelling, and tenderness.
One in three women and men with DVT suffer a serious complication called pulmonary embolism (PE).1,2 This happens when part of the DVT breaks off and travels through the bloodstream, eventually blocking an artery that supplies blood to the lungs. PE is extremely serious and often causes sudden death. It is estimated that PE is the number one cause of death in hospitalized patients in the US.3
Together, DVT and PE are known as venous thromboembolism, or VTE. Each year 350,000 to 600,000 Americans (half of them women) suffer from VTE, and these conditions may contribute to 100,000 deaths every year.4,5 In addition to painful leg symptoms and the risk of PE, blood clots can damage the veins in the legs, sometimes leading to chronic vein disease.
Despite the fact that blood clots in the veins are common and put you at risk for serious complications, public awareness is low. Three quarters of Americans have never heard of DVT, and 95% say their doctor has never discussed the condition with them. Of people who have heard of the disease, fewer than half know any of the common characteristics or conditions that put you at risk.6
The good news is that DVT is treatable and often preventable. By learning how to recognize the symptoms of DVT and how to know if you are at risk, you can take steps to prevent a blood clot from forming and seek treatment before serious complications occur.
What are the symptoms of DVT?
DVT is often "silent" and produces no symptoms as much as half the time. Seek treatment immediately if you experience any of the following signs of DVT, as prompt treatment can prevent a potentially deadly PE:
- Swelling in one leg or along a vein in a leg or arm
- Pain or tenderness in one limb (may only appear when standing or walking)
- Warmth, redness, or discolored skin in the affected leg or arm
Unfortunately, the first sign of DVT is often a life-threatening pulmonary embolism. If you experience these symptoms of PE, call 9-1-1 immediately:
- Unexplained shortness of breath or difficulty breathing
- Sharp chest pain, especially during deep breathing
- Other symptoms:
- Rapid heartbeat, sweating, anxiety
- Dizziness, fainting, coughing up blood
Who is at risk for DVT?
Blood clots can occur in anyone at any age. However, like other forms of heart and blood vessel disease, DVT becomes more common as you age. Up to age 50, rates rise relatively slowly, but the risk of DVT doubles for each 10-year increase in age after 50.7
Because of hormonal factors, women have a higher risk of DVT than men during their childbearing years. After age 50, men have about a 20% higher risk than women.7 Overall, DVT is equally common in women and men.2
DVT is more common in certain races: African Americans are at the greatest risk, with a 30% higher risk than whites. People of Asian or Native American backgrounds have a much lower risk, 70% less than whites.8,9
Half of women and men who suffer DVT have one or more risk factors that set the stage for DVT, combined with a triggering event that actually causes the blood clot to form. In the other half of cases, the causes of DVT are not known.2
In addition to your age, race, and gender, certain characteristics and conditions put you at risk for DVT, including:
- Obesity and overweight, especially if you carry your weight around the hips10
- Inherited blood clotting disorders ( thrombophilia)
- Varicose veins (an early sign of vein problems)11
Unique factors that can put women at risk include:
- Birth control pills (oral contraceptives) that contain estrogen and progestin increase a woman's risk of blood clot 2 to 8 times.12 Because they contain more estrogen, contraceptive patches may carry an even greater risk. Progestin-only contraceptives do not appear to increase risk.13
- Hormone replacement therapy (HRT) increases a woman's risk of DVT by 2 to 4 times14
- Pregnancy stresses the blood vessels because of hormonal changes and an increased volume of blood. During pregnancy and the first few months after the baby is born, the risk of DVT or PE is increased more than 4-fold.15 PE is the number one cause of maternal death in the US.16
If you have more than one DVT risk factor you are at even greater risk. For example, a women who is obese (BMI over 30) has 2 to 3 times the normal risk of DVT, but if she also takes oral contraceptives, her risk increases to 10 times the normal risk.17
While the above factors make you more likely to develop DVT, often a " trigger" event causes the blood clot to form. Common triggers include:
- Major surgery
- Trauma (especially fractures of the pelvis, hip, or leg)
- An extended period of immobility, for example:
- During a hospital stay
- In a nursing home
- During long travel - travel of 4 hours or more (flying, driving, or on bus or train) doubles your risk of blood clots for weeks after the trip18; longer travel increases risk even more19
See also: Preventing DVT: The Basics