Clot-Busting Drug Offers New Approach to DVT
TUESDAY, Jan. 29 -- When it comes to treating deep vein thrombosis, injecting the clot-busting drug alteplase (rTPA) directly into clots in the legs reduces the risk of complications and recurrence, a small U.S. study suggests.
Adding rTPA to the standard treatment of blood thinners appears to completely destroy the clots, something not achieved by blood thinners alone, according to the researchers.
"The anticoagulation therapy that you get for DVT is pretty good at protecting you from pulmonary embolism, which is the life-threatening part of DVT," said study author Dr. Richard Chang, of the National Institute of Health's Department of Diagnostic Radiology.
DVT is the formation of blood clots in veins deep within the legs. These clots can turn life-threatening when they become dislodged and travel through the veins into the lungs, where they can block pulmonary veins, causing breathing problems and even death. Some 250,000 people in the United States suffer a first episode of DVT each year.
The problem with blood-thinning therapy is that it doesn't completely remove the clots in the leg veins, Chang said. "So, years down the line, about a third of the people develop post-thrombotic syndrome," he said.
Post-thrombotic syndrome can cause severe leg pain, difficulty walking and skin changes and venous ulcers. Dissolving the clot can help prevent this syndrome, Chang said.
For the study, researchers treated 20 DVT patients with a course of blood-thinning therapy. They were also given daily 50-milligram injections of rTPA for a maximum of four days. During a three-year follow-up, none of the patients developed complications associated with DVT or had a recurrence of the condition, Chang said.
The findings are published in the February issue of Radiology.
Chang noted that the objection to the clot-busting approach is the fear of bleeding caused by rTPA. However, by injecting rTPA directly into the clot, little of the drug circulates through the bloodstream. In addition, this method allows doctors to treat all the clots in leg veins, Chang said.
In an extension of this study, Chang's team has done the same procedure using rTPA doses that are five times lower than the ones used in this trial. Lower doses of rTPA further reduce the risk of bleeding, he said.
Although the results of this second study haven't been published yet, Chang said the results were "even better."
"There is a lot of margin for improving this even further," Chang said. The use of thrombotic therapy is not meant to replace blood-thinning therapy, he added, but to be used in tandem to help prevent later complications and recurrence of DVT.
Dr. Suresh Vedantham, an interventional radiologist and an assistant professor of radiology and surgery at Washington University School of Medicine in St. Louis, thinks that this method of dissolving clots could eventually become an outpatient procedure.
"That would be a major step forward," Vedantham said. "This technique is very promising, but it needs to be tested in a larger trial."
But another expert said he wasn't sure if this treatment will prove to be useful.
"The fundamental question is if one requires this intensive type of treatment in order to improve patient outcome over the long term," said Dr. Samuel Z. Goldhaber, director of the venous thromboembolism research group at Brigham and Women's Hospital in Boston.
Goldhaber noted that the clot-busting procedure is difficult to do and requires advanced training and it goes against the currently accepted treatment for DVT. "This approach needs to be proven in a randomized, controlled trial," he said.
The trial would have to show that the clot-dissolving procedure was superior to current therapy, worth the extra cost and effort, and the temporary discomfort to the patient, Goldhaber said.
For more on deep vein thrombosis, visit the Society for Interventional Radiology.
Posted: January 2008
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