RSNA Press Release

• Researchers at the National Institutes of Health have developed an effective treatment for deep vein thrombosis.
• Deep vein thrombosis is a serious health problem in which blood clots form in the deep veins and can break off and travel to the lungs.
• Using a clot-busting agent called alteplase, the researchers were able to dissolve the clots and reduce the risk of recurrence or complications.

OAK BROOK, Ill. - A novel treatment for blood clots in the legs appears to be safe and effective, according to a pilot study published in the February issue of Radiology. The study found that injecting or "lacing" the clot with a fiber-binding thrombolytic agent effectively treats deep vein thrombosis (DVT) and reduces the risk of subsequent recurrence or bleeding.

"This treatment regimen is able to clear blood clots rapidly and safely, restoring blood flow in the veins of the lower leg, and the results are durable," said lead author Richard Chang, M.D., chief of the interventional radiology section of the Department of Radiology, Clinical Center, National Institutes of Health (NIH), Bethesda, Md.

DVT is a common and serious health problem in which a blood clot, or thrombus, form in the deep veins, particularly in the lower leg or thigh. Complications occur when the clot breaks off and travels to the lungs, resulting in pulmonary embolism, a potentially fatal condition.

Most patients with DVT are treated solely with anticoagulation therapy (blood thinners) and compression stockings. However, studies have shown that one-third of these patients will suffer from post-thrombotic syndrome, characterized by pain, swelling, or in severe cases by changes in skin color or skin ulceration. Another third are likely to have another clot or pulmonary embolism within five years of their initial DVT.

Treatments with thrombolytic (clot-dissolving) therapy could potentially protect against these occurrences, but can pose a bleeding risk. Therefore, Dr. Chang and colleagues sought to develop a safe, effective and affordable thrombolytic treatment regimen for DVT.

Twenty patients with acute DVT were treated with direct intraclot lacing of the thrombus with a clot-dissolving agent called alteplase and full systemic anticoagulation. Alteplase binds to the clot, so the procedure does not require continuous infusion of the drug, as do some thrombolytic therapies. With this treatment, after lacing one vein segment with alteplase, the interventional radiologist can immediately direct catheters to treat other vein segments to ensure that the entire clot has been adequately treated.

The results of the study showed that blood flow was restored throughout the deep venous system in 16 (80 percent) of the 20 patients during therapy with complete resolution of symptoms in 18 patients (90 percent) after six months of anticoagulation. Alteplase was cleared from the patients' circulatory system within two hours of treatment, reducing the risk of subsequent bleeding.

There were no serious complications or bleeding during the treatment, and no cases of post-thrombotic syndrome or recurrent clotting during follow-up of 3.4 years.

"With this therapy, pain and swelling resolve rapidly, and, in most cases, the patient is able to resume all normal activity within a week," said the study's co-author, McDonald K. Horne III, M.D., from the hematology section of the Department of Lab Medicine, Clinical Center, NIH.

The authors caution that larger clinical trials are required to further support the efficacy of this promising treatment.

Journal attribution required.

Radiology is a monthly scientific journal devoted to clinical radiology and allied sciences. The journal is edited by Herbert Y. Kressel, M.D., Harvard Medical School, Boston, Mass. Radiology is owned and published by the Radiological Society of North America, Inc. (RSNA.org/radiologyjnl)

The Radiological Society of North America (RSNA) is an association of more than 40,000 radiologists, radiation oncologists, medical physicists and related scientists committed to promoting excellence in radiology through education and by fostering research, with the ultimate goal of improving patient care. The Society is based in Oak Brook, Ill. (RSNA.org)

"Deep Vein Thrombosis of the Lower Extremity: Direct Intraclot Injection of Alteplase Once Daily with Systemic Anticoagulation—Results of a Pilot Study." Collaborating with Drs. Chang and Horne were Clara C. Chen, M.D., Anthony Kam, M.D., Ph.D., Edie Mao, M.B., and Thomas H. Shawker, M.D.

This study was funded by the National Institutes of Health.