Doctor Doctor: Deep Venous Thrombosis — What You Need to Know
Network - Spring 2007
In 2004, David Bloom, an NBC correspondent working in Iraq, died of complications from undiagnosed deep venous thrombosis. Suddenly, a little-known health threat came to national attention. While 600,000 people are hospitalized each year with DVT and around 300,000 die, the American Heart Association estimates that two million people suffer from this disease each year, most of them undiagnosed or diagnosed too late. This is of concern to Shu-Wei Gao, M.D., assistant professor in the Division of General Internal Medicine, and his colleagues at M. D. Anderson where each month 120 new cases occur.
What is deep venous thrombosis and where does it occur?
DVT is a clot that occurs in a major vein, blocking blood flow either partially or completely. Approximately 90 percent of these clots occur in the lower extremities. When DVT occurs in the deep veins of upper extremities, it is usually caused by a central venous catheter and referred to as catheter-related thrombosis.
What are its complications?
DVT sets up the possibility of a pulmonary embolism or PE. This occurs when a blood clot breaks away from the venous wall and travels to the lung, obstructing the pulmonary artery or one of its branches and causing severe, life-threatening cardiopulmonary consequences. DVT may also cause post-thrombotic syndrome, chronic edema, non-healing ulceration and persistent pain in the involved extremity.
What are the symptoms for DVT and PE?
Typical symptoms of DVT are pain, swelling and discoloration of the involved extremity. The involved area also may become warm, red and tender when pressed. Occasionally, a cord can be felt along the vein. The problem with diagnosis is that more than 50 percent of patients with DVT have none of these symptoms. Typical symptoms of PE include a combination of sharp chest pain with a deep intake of breath, a sudden onset of shortness of breath and coughing up blood. As with DVT, more than half of the patients will not have any or all of these symptoms.
How are DVT and PE diagnosed?
DVT and PE cannot be diagnosed with certainty by a clinical examination alone. The diagnosis relies on objective imaging studies. Ultrasonography is the most common means of detecting DVT, while spiral CT is best for the diagnosis of PE. Because these don’t always provide an accurate diagnosis, and delay of treatment may have serious consequences, it is important for the physician to vigorously seek medical information from patients suspected of having a higher risk for either. This information will help determine when to order the imaging study and how to interpret the results more accurately.
What are the risk factors for DVT?
Any conditions that increase blood clotting, reduce blood flow or damage the integrity of the blood vessel will increase the risk for development of DVT. The major risk factors are cancer, major surgery, a previous DVT/PE, immobility, trauma to the leg, pelvis or spine or a family history of DVT/PE. The other risk factors include advanced age, obesity, smoking, pregnancy, contraceptive pills and dehydration. The risk of developing DVT will be much higher if more than one risk factor exists.
What are the risk factors for cancer patients?
Compared to the general patient population, cancer patients have a higher risk of developing DVT due to increased coagulability, venous stasis and damage to the venous wall from cancer and/or its treatments, such as surgery, chemotherapy, radiation and central venous catheter placement. Other possible chemical causes have not been isolated yet because of combination therapies. However, it is known that tamoxifen, thalidomide, some growth factors and andriomycin are culprits.
How can DVT be prevented?
The most important way to prevent DVT is to avoid risky behaviors, such as prolonged immobilization, smoking, obesity and dehydration. If risk factors are not avoidable, mechanical or pharmacologic prophylaxis should be applied whenever possible, for example, using a compression stocking or blood thinner when hospitalized, receiving chemotherapy or undergoing surgery. During long distance travel, one should avoid wearing tight clothing, staying immobile for prolonged periods and dehydration. Those who already have significant risk factors should wear a compression stocking or have a shot of low-molecular weight heparin hours before the trip.
Network - Spring 2007
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- Doctor Doctor: Deep Venous Thrombosis — What You Need to Know
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