10 Signs You're at Risk for a Blood Clot 10 Signs You're at Risk for a Blood Clot

Health Conditions Related to DVT

DVT means a blood clot in a deep vein. If you have cancer, a heart health condition, or are pregnant or overweight, you may be at risk.

 

By Chris Iliades, MD

Medically reviewed by Lindsey Marcellin, MD, MPH

Certain health conditions or their treatments can put you at an increased risk of blood clotting. When a blood clot, or thrombus, forms within a vein deep in your body, it’s called deep vein thrombosis (DVT). DVT can be dangerous because a clot that pulls loose from your vein may travel through your bloodstream and lodge in a lung. A blood clot in a lung is a pulmonary embolism, and this can be fatal.

"To understand why certain medical conditions increase your risk of DVT, you need to know about Virchow's Triad," says Harold J. Welch, MD, a vascular surgeon at the Lahey Clinic in Burlington, Mass. Rudolf Virchow was a German physician who studied blood clots, and in 1856, he described the three important factors that contribute to DVT. "Those three factors still hold true today,” says Dr. Welch. “They include any alteration of normal blood flow, any damage to the inside of a vein, and any tendency for the blood to clot too much. Medical conditions that cause one or more of these factors can lead to DVT."

 

Conditions That Increase Your Risk of DVT
One of the highest risk factors for DVT is having had a previous pulmonary embolism or DVT. People who form blood clots too easily are said to have hypercoagulability. In some cases, this is an inherited tendency.
"It's the opposite of hemophilia, which is not clotting enough,” says Welch. “There is a lot we don't know about why clotting becomes abnormal. I sometimes tell patients that understanding blood clotting is harder than sending someone to the moon."
The following conditions can increase the formation of blood clots, and therefore lead to DVT and pulmonary embolism:

• Cancer. "Cancer cells release chemicals that increase blood clotting,” explains Welch. “In some cases, DVT may be the first sign of cancer." Cancer treatment may also damage blood vessels and cause you to be less active, both of which contribute to DVT.
• Heart health. Any condition that affects your heart’s ability to pump blood normally can lead to blood clots. Heart health conditions, particularly congestive heart failure and a previous heart attack or stroke, can cause blood to back up inside your veins, which encourages clots to form. Having poor heart health may also make you less active.
• Pregnancy. Women who are pregnant are at a short-term risk of DVT. "Pregnancy causes venous pressure to build up in your legs, which is where most blood clots form,” says Welch “Pregnancy also increases blood clotting in ways we don't completely understand." Women who are overweight or over age 35 are at higher risk of DVT and embolisms during pregnancy.
• Obesity. Being overweight is bad for your heart health and often goes hand-in-hand with inactivity. Studies show that obesity increases your risk of DVT. If you are obese, you also have a greater risk of DVT during surgery and during pregnancy.

Other health factors may also put you at risk, including:

• Trauma. Trauma can injure blood vessels, which may lead to clot formation. Injuries to bones, especially the bones in your legs, commonly release fats and other substances that increase clotting into the blood.
• Surgery. Surgery is a very common cause of DVT. Surgery can result in damage to blood vessels, slowing of blood flow, and the release of chemicals that increase clotting.
• Inflammation. Inflammation is your body's response to injury or infection. Proteins released by your body during inflammation have been shown to be associated with a higher risk of blood vessel disease. Some chronic inflammatory conditions that increase your risk of DVT include Crohn's disease and ulcerative colitis.
• Estrogen. Estrogen is a hormone used in birth control pills and hormone replacement therapy, a treatment that may be prescribed after menopause. Estrogen increases blood clotting. "Taking estrogen as birth control or replacement therapy does increase your risk of DVT," notes Welch.
• Catheters. Catheters are long, thin tubes that are inserted into your body. A catheter may be inserted into a vein to administer fluids or liquid feedings when you are sick, or to measure the pressure inside your heart. These procedures may damage the inside of a vein and lead to a blood clot.
• Pacemakers. Pacemakers implanted in the chest to treat abnormal heart rhythms may also increase the risk of DVT.

If you know you are at increased risk of DVT, the best thing you can do is work closely with your doctor to prevent blood clots and watch for symptoms of DVT.

Always let your doctor know if you have any changes in skin color, increased warmth, tenderness, swelling, or pain in one of your legs. Your doctor can prescribe medications to prevent DVT if you are at high risk and to treat DVT if you develop it.

Last Updated: 06/08/2010