In 2011 tennis star Serena Williams was hospitalized with a life-threatening blood clot in her lung. This condition is called a pulmonary embolism. It was probably triggered by foot surgery followed by a long flight from New York to Los Angeles.
Although a pulmonary embolism is a blood clot in the lung, it usually starts with a clot in a leg vein. This is called a deep venous thrombosis (DVT).
One out of every 10 men will have a DVT during his lifetime. Here's what you need to know about DVTs and how to protect your veins.
Although venous clots can sometimes form without an obvious cause, they majority of DVTs are triggered by a condition that:
Other conditions that increase the risk of a DVT include:
Typical symptoms include:
In most cases, only one leg is affected. The calf can feel tense and swollen, and fluid may accumulate in the ankle or foot.
In severe cases, the leg may feel warm or appear bluish; a swollen vein may also be visible. DVTs can cause fever.
Many DVTs have no symptoms. In addition, many unrelated conditions can mimic DVTs. These include:
So the correct diagnosis can be tricky. A high level of suspicion by the doctor — and the patient — is the first requirement. Without it, the doctor may not order tests to diagnose a possible DVT.
DVTs of the arm veins are relatively uncommon. Most occur when a patient in the hospital has a plastic catheter (tube) inserted in a vein to administer fluids or medication. But some are caused by unusual physical effort or by abnormal pressure on a vein from a rib.
Veins just beneath the skin can also develop clots. This condition is called superficial thrombophlebitis. The vein becomes red, hard, warm and tender to the touch. Because complications are rare, therapy is much simpler than for DVTs; in most cases, warm packs and nonsteroidal anti-inflammatory drugs such as aspirin or ibuprofen will do the trick.
Until recently, doctors thought they could diagnose a DVT by carefully examining a patient's legs. But this can miss many DVTs. Useful diagnostic tests include:
Ultrasound. A healthy vein will flutter when compressed by an ultrasound probe, but a clot-filled vein will not. Ultrasound is about 95% accurate for detecting DVTs in the large veins of the thigh. It is less accurate (about 70%) for diagnosing clots in the calf veins. That's less of a problem than it might seem. Calf vein DVTs are much less likely to break off and travel to the lungs. This makes them less dangerous.
D-Dimer blood test. As the blood clotting protein fibrin breaks down, it releases smaller fragments into the bloodstream. D-Dimer is one of them. It's easy to measure. A low level argues strongly against an active DVT. A high level, however, isn't nearly as helpful, because a variety of conditions can boost d-Dimer levels.
Blood tests to detect over-activity of the blood clotting system. Patients with a family history of DVTs, with unusual or recurrent DVTs, or with DVTs that develop before age 45 or without evident cause are appropriate candidates for testing.
Special tests. Helical CT has become the standard test to diagnose pulmonary emboli, the life-threatening complications of DVTs.
Most DVTs start in the calf veins. Complications are uncommon if the clot remains in the calf; in fact, the body can often dissolve calf DVTs even without medication.
Unfortunately, though, calf vein DVTs can move up to the veins of the thigh and pelvis, which can cause major complications. These include:
The first lines of treatment are medicines called anticoagulants. They are commonly referred to as "blood thinners." They prevent the blood from clotting. This stops a DVT from moving up a vein and gives the body time to dissolve the clot on its own without allowing it to break apart and move to the lungs.
When the clot forms rapidly causing marked swelling and pain in the leg, the person may benefit from a "clot-busting" (thrombolytic) medication. It is usually not needed. The person will still need anticoagulants as well.
Therapy has two parts:
Therapy usually lasts for three to six months for a first DVT episode. But patients with recurrent DVTs, certain clotting abnormalities or other risk factors, or major pulmonary emboli should continue medication and often require lifelong therapy.
The major complication of anticoagulant therapy is bleeding. In most cases, the risk can be minimized by careful therapy, but DVT patients who cannot take anticoagulants because of bleeding may need to have a filter placed in their major abdominal vein (the inferior vena cava) to protect them from pulmonary emboli.
Compression stockings can reduce the risk of permanent vein damage. The average patient can return to exercise after about a month of treatment.
Treatment may cause bleeding or other side effects. So prevention is the best treatment of all.
Many DVTs and pulmonary emboli occur in people in the hospital. Doctors can prevent these major complications by prescribing anticoagulants. In most cases, low-molecular-weight heparin is best. High-risk patients, such as those who have had hip replacements, benefit from oral anticoagulant medicines after they leave the hospital. Special leg compression stockings can protect patients who have had brain surgery and others who cannot take anticoagulants.
To prevent DVTs at home keep moving, walk nearly every day and avoid prolonged bed rest. Avoid being overweight, don't smoke and stay well-hydrated.
Any form of prolonged sitting can trigger the problem. Air travel increases the risk due to cramped quarters and dry air, which make the blood “thicker” and "stickier." DVTs are uncommon on flights of less than four hours, but the risk increases with longer trips, particularly those of eight hours or more. Here are some travel tips:
The risk is also higher in people who have had recent surgery, especially hip or leg operations, and in people with certain types of cancer, chronic leg swelling or heart failure. Other risk factors include obesity, smoking and any condition that results in prolonged immobility or bed rest within two weeks of the trip. People with overactive blood clotting systems and those who have had previous episodes of deep vein thrombosis face the highest risk of all.
Compression stockings gently squeeze the leg veins and make it easier for the body to keep blood flowing up to the heart. Aspirin is a very effective way to prevent clots in arteries but its value for DVTs is far less certain. An aspirin a day can’t hurt, but people who need the fullest protection should ask their doctors about an injection of low-molecular-weight heparin before they take off.
At home or in an airplane, do what it takes to protect your veins, your lungs and your life by keeping the blood moving in your legs. Be sure your doctor considers DVT prevention if you are hospitalized. Take your anticoagulant medicine if it's recommended.
Most men spend much more time thinking about SUVs than DVTs. That's okay if you're at low risk, but before you fly across the country or check into a hospital, you should show your veins the respect they deserve.
Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.