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Monday, February 14, 2011
Deep vein thrombosis (DVT) and pulmonary embolism (PE) affect nearly 1 million Americans each year. For decades, the standard treatment for these patients has been anticoagulation therapy. But for many patients, this may not be the ideal approach.
Of particular concern is post-thrombotic syndrome (PTS), which develops in approximately 30 percent of patients who suffer from DVT. Because anticoagulation therapy alone rarely dissolves a clot, a patient can develop valve damage in the femoral vein during the healing phase that results in reflux and venous insufficiency, ultimately leading to PTS.
PTS can have a significant, lasting impact on a patient’s quality of life. In severe cases, PTS can cause skin discoloration, pain, and venous skin ulcers.
The ATTRACT Study
At the Massachusetts General Hospital Vascular Center, a multidisciplinary team of experts is testing a new approach for patients with symptomatic proximal DVT that involves the iliac, common femoral, and/or femoral vein. The study, known as ATTRACT (Acute Venous Thrombosis: Thrombus Removal with Adjunctive Catheter-Directed Thrombolysis), is funded by the National Institutes of Health (NIH). ATTRACT is a large, national, multidisciplinary trial to evaluate the safety and effectiveness of catheter-directed thrombolytic methods compared with standard blood thinning—and how well they might prevent PTS.
In these approaches, specially trained interventional physicians deliver clot-dissolving medications directly into the deep vein blood clot, thereby making the clot easier to remove mechanically.
Specifically, medications are introduced via catheter, breaking up the blood clot and dispersing the clot-dissolving drug. Theoretically, the femoral vein valves will be cleared of the clots and their function restored, which researchers hope will prevent PTS. Devices being tested in the trial include the Trellis® Peripheral Infusion System, an EKOS device, and the AngioJet®. By testing medical and interventional treatments head to head, the study may significantly alter how DVT is treated in the future.
The ATTRACT study opened patient enrollment in late 2009, and today, more than 50 centers are involved in the trial. The Mass General Vascular Center is currently enrolling patients who will be followed for two years as part of the research project. Appropriate candidates are those with less than a two-week history of acute DVT in the lower extremities.
This landmark trial is the first NIH study to compare outcomes of medical and interventional approaches with DVT treatment. The primary goal of the ATTRACT study is to determine whether pharmacomechanical catheter-directed thrombolysis (PCDT) reduces the development of PTS over two years.
Stephan Wicky, MD, Director, Division of Vascular Imaging and Intervention, Massachusetts General Hospital, is the principal investigator. He has been treating DVT with a combination of thrombolysis using tissue plasminogen activator and mechanical clot removal since 1995 and at Mass General since 2003.
Michael R. Jaff, DO, medical director of the Mass General Vascular Center as well as of Mass General’s Vascular Diagnostic Laboratory and Vascular Ultrasound Core Laboratory (VasCore), serves on the national steering committee for the ATTRACT study. VasCore has been involved in more than 60 clinical trials since it was founded in 1998. Because of its internationally recognized expertise, the lab is training the study sites on venous duplex ultrasonography. It is also conducting a sub-study in which 142 patients will be assessed for valvular reflex and residual thrombus after one year.
Co-principal investigators for the study at Mass General include Gregory Walker, MD; Sanjeeva Kalva, MD; Shams Iqbal, MD, member, Division of Vascular Imaging and Intervention ; Virendra Patel, MD, RPVI, Division of Vascular and Endovascular Surgery; Robert Schainfeld, DO, Vascular Medicine; Christopher Kabrhel, MD, Emergency Services; and Walter Moulaison, RN, Anticoagulation Management Services. The physician-researchers will compare the severity of PTS using the Villalta PTS scale, the revised CEAP classification system, and the venous clinical severity score (VCSS). In addition, the study team will measure safety and cost-effectiveness between the medical and interventional treatment groups.
Advances in Interventional Approaches
Multiple physician specialties have managed complex cases of deep vein thrombosis with unique interventional approaches throughout their careers. For example, interventional radiologists at the Mass General Vascular Center have pioneered catheter-directed treatments for patients with DVT. In 2006, interventional radiologists introduced the EKOS catheter at Mass General. This technology uses miniature ultrasound probes that are positioned into a catheter to more rapidly break up a clot. This DVT treatment is faster than previous interventional approaches and may reduce the risk of bleeding and other complications.
In addition, Dr. Wicky and colleagues have evaluated the design and application of multiple inferior vena cava (IVC) filters over several decades. IVC filters are approved for use in patients who cannot receive standard anticoagulation, as well as in patients who have developed complications or recurrent DVT despite adequate anticoagulation. In particular, the Vascular Center has gained expertise with numerous retrievable IVC filters. Patients with such devices require ongoing follow-up to schedule retrieval of the filters.
Since 2008, the Vascular Center has offered recanalization procedures to patients with thrombosed IVC filters. In these patients, the filters become totally embedded into the clots, making retrieval impossible. The Vascular Center was among the first centers in the world to perform extensive recanalization, including stent placement across a filter. This can restore blood flow at the occlusion site and provide patients with dramatic relief of PTS symptoms.
Optimal Medical Management of Patients with Clots
As many as half of all patients with clots have an identifiable risk factor, such as pregnancy, trauma, surgery, immobility, malignancy, or a genetic condition. At Mass General, each patient who presents with a clot is seen by experts within the Center for Hematology, led by David J. Kuter, MD, DPhil. The Hematology team works closely with the Mass General Vascular Center to evaluate the patient for risk factors and then recommends the ideal course and duration of anticoagulation therapy. Collaboration with the patient’s primary care physician helps provide more comprehensive information on the etiology of the clot so the team can select the most appropriate therapy.
The Center for Hematology has been instrumental in the development and use of novel anticoagulants and anticoagulation strategies in patients with DVT and PE. Agents other than warfarin may help reduce the rate of recurrence in both conditions. Tests to assess thrombotic risk and its reduction by anticoagulation are commonly used and include novel tests, such as the thrombin generation assay.
When a patient develops long-term complications of a clot, such as PTS, Dr. Kuter and his team will refer the patient back to the Vascular Center for assessment. There, the patient can receive comprehensive treatment for vascular complications from a multidisciplinary team of physicians, vascular-trained nurses, and technologists.
At the Mass General Vascular Center, the collaboration between Hematology and Vascular Center physicians and nurses has helped the center earn national recognition for its expertise in vascular disease. By advancing clinical care as well as participating in groundbreaking research projects like the ATTRACT study, physician-researchers hope to uncover better answers for treating DVT and preventing PTS.
Massachusetts General Hospital Vascular Center
Massachusetts General Hospital established the Vascular Center to provide comprehensive care for patients with vascular disease. As a dedicated vascular center with specialists in every area of vascular disease, the Vascular Center offers a uniquely focused, multidisciplinary approach to vascular medicine. Specialists in seven critical disciplines work together. These include cardiac surgery, cardiology/vascular medicine, nephrology, neurology, neurosurgery, vascular and endovascular surgery, and vascular imaging and intervention.
Multispecialty Programs: Aortic Disease Program; Brain Aneurysm and Arteriovenous Malformations Program; Fibromuscular Dysplasia Program; Peripheral Artery Disease Program; Stroke and Carotid Artery Disease Program; Venous Disease Program; Visceral Vascular Disease Program.
For more information about the Vascular Center services or to refer a patient, please call 877-644-8346 or visit the Vascular Center website
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