You may know someone who has suffered a blood clot in their legs (deep vein thrombosis, or DVT) or lungs (pulmonary embolism, or PE). An estimated 900,000 Americans are hospitalized with DVT or PE every year, and 60,000 to 100,000 die from it as soon as one month after it occurs. Others can experience complications that last for years.
“With leg DVT, if the clot doesn’t clear, or it damages a valve in the veins, chronic swelling, pain and leg ulcers can result. This is called post-thrombotic syndrome,” says Cleveland Clinic vascular medicine specialist Deborah Hornacek, MD.
“With PE we worry about short-term risk of death due to sudden strain on the heart. PE is the third-most common cause of cardiovascular death in this country,” she adds.
Long-term complications from PE can be caused by increased blood pressure in the lungs from an old clot blocking the arteries. Fortunately, this condition is rare.
Who Is at Risk?
An estimated 5 to 8 percent of people inherit the tendency for their blood to clot. However, most clots develop when blood flow slows down (stasis) or a blood vessel wall is injured (endothelial injury). This sets off a cascade of events that makes the blood more clottable.
“Things that slow blood flow-prolonged sitting or bed rest, or long surgical procedures-are common triggers,” says Dr. Hornacek.
After surgery or hospital admission for a severe illness, patients may be given mini-doses of anticoagulants to prevent blood clots.
Pregnancy and estrogen use, as well as older age, higher weight and other classic cardiovascular risk factors, including smoking, add to DVT risk. Additionally, intravenous catheters can cause DVT in the vein in which they are placed.
A rare, but serious, problem can occur when a DVT blood clot breaks off and is carried into a heart that has a hole between its upper chambers (patent foramen ovale, or PFO). If the clot passes from the right side of the heart into the left and is pumped into the arteries supplying the brain, it can cause a stroke.
Symptoms of DVT
A blood clot forming in one of the deep veins of the leg may cause the leg to become swollen, tender, red and hot to the touch. These are signs that blood flow through the vein has stopped. “It can happen fairly quickly. Leg swelling or crampy pain that persists are telltale signs,” says Dr.Hornacek.
Immediate treatment with blood thinners is needed to stop the clot from growing, prevent new clots from forming and stop the existing clot from moving to thelungs.
How a DVT Becomes a PE
If a DVT breaks from the blood vessel wall, it can travel up through the veins to the heart. There, it enters the right atrium, passes into the right ventricle and is pumped into the lungs, where it can become stuck in a pulmonaryartery.
Symptoms of PE include sudden, unexplained shortness of breath, chest pain or discomfort that worsens with coughing or inhaling deeply, feeling faint or coughing up blood. “This is a medical emergency,” says Dr. Hornacek.
Treatment for PE
Most patients with PE are hospitalized and treated with intravenous anticoagulants to break up the clot.
When a PE is large enough to be life threatening, some physicians may choose to deliver the clot-busting drug tPA or remove the clot surgically.
“There are significant risks that have to be balanced against the risk of dying from the PE. Sometimes, it’s hard to know which way to go,” says Dr. Hornacek.
The majority of patients with PE are given oxygen, intravenous heparin or injections of enoxaparin (Lovenox), and sent home on a blood thinner.
Select low-risk patients with a small PE, who are medically stable and feel well, may be treated as outpatients and started promptly on blood thinners.
When a small PE causing no symptoms is found accidentally on a scan done for another reason, new guidelines say treatment with blood thinners is optional. “This is still controversial,” says Dr. Hornacek. “Many of us still like to err on the safe side and treat the patient for a period of time with blood thinners.”
After the Diagnosis
Unless preventive measures are taken, one-third of patients who suffer a DVT or PE may experience another clot within 10 years. Identifying the cause of the clot allows it to be prevented or treated.
“Especially when the underlying cause is inactivity or travel, and you plan a long-distance trip by car or plane, we advise you to stay hydrated and stop every hour or two to move around and stretch your legs,” says Dr. Hornacek.
If you have had a PE, you may want to ask your doctor whether you should undergo pulmonary function testing before you fly. These tests can determine whether your body will be able to tolerate the lower oxygen levels in an airplane cabin.
In most patients, the decision when to stop anticoagulants is individualized. “When the contributing trigger is known and addressed, the risk usually goes down enough that we can take them off blood thinners after a couple months,”‘ says Dr. Hornacek.
Guidelines generally recommend three months of anticoagulation for a blood clot caused by temporary risk factors such as surgery or medical illness.
In 10 to 15 percent of patients, the underlying cause is never identified. “These patients, along with those confined to bed or having other ongoing risk factors, are at the highest risk of a second occurrence and may need to take blood thinners indefinitely,” she says.
Tip for Travelers: After a DVT, Dr. Hornacek encourages patients to wear medical-grade, graduated compression stockings. These stockings have stronger support at the ankle and lighter support near the knee to help increase blood flow up the legs when seated or standing. They are different from thrombo-embolic deterrent (TED) hose, which are tube-shaped socks that provide uniform pressure throughout their length. TED hose help prevent blood clots in bedbound patients and are typically used in the hospital and after surgery.