Blood clot treatments subject of major trial
By Michael C. Purdy • September 24, 2008
A $10 million, government-funded, multicenter clinical trial of an aggressive treatment for blood clots in the leg — known as deep vein thrombosis (DVT) — will be led by School of Medicine researchers.
About 250,000 U.S. patients are diagnosed with new DVTs every year. Current clinical standards call for the patients to be treated with blood-thinning agents, which prevent clot migration and formation of new clots but do not break up the original clot. Clinicians recently have realized the original clot often leads to serious, difficult-to-treat, long-term complications.
Suresh Vedantham, M.D., associate professor of radiology and of surgery, is the national principal investigator for the Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis (ATTRACT) Trial, which will test the use of catheter-mounted technology that can both chew up DVTs and directly administer clot-busting drugs. The trial is funded by the National Heart, Lung, and Blood Institute.
“This is the first large-scale test of these new techniques, and the potential to change clinical DVT practice on a large scale is very exciting,” said Vedantham, an interventional radiologist at Barnes-Jewish Hospital. “If the trial is positive, it will alter the paradigm to say we don’t just prevent the next clot, we’ve got to also remove the existing clot first.”
The initial symptoms of DVT are pain and swelling in the affected leg. Associated risk factors include surgery or trauma to the leg, genetic factors, immobilization, hormonal therapies and cancer. DVTs are more common in older patients but also can occur in childhood and throughout life.
The most immediate danger from a DVT is the clot breaking loose and moving to the lungs, a condition called pulmonary embolism that kills about 100,000 people annually nationwide. Complications from the continued presence of the clot, known as post-thrombotic syndrome (PTS), occur in 50 percent of all DVT patients.
“PTS causes long-term chronic pain, swelling, venous ulcers and difficulty walking,” Vedantham said. “This often leads to disability, is very costly and difficult to treat and significantly impairs quality of life. By removing the clot when it is first diagnosed, we can prevent permanent damage to the leg veins and thereby prevent PTS.”
Physicians tested clot-busting drugs on DVTs as early as the 1970s, but the approach was deemed unsafe because general administration of the drugs incurred too much risk of bleeding. Radiologists can now pinpoint the location of DVTs with X-rays and an injectable dye.
Recently developed catheter technology makes it possible not only to deliver clot-busting drugs directly to the DVT but also to mash the clot to help break it up and ensure better distribution of the drugs. One such technology uses a wire in the catheter turned via a small handheld motor to break up the clot; others use ultrasound.
“The goal is to provide a safer, quicker and much more effective approach to treatment,” Vedantham said.
Plans call for 692 patients to be enrolled in the ATTRACT Trial at 28 clinical centers nationwide.