Medical Device Daily National Editor
Deep vein thrombosis (DVT) is a condition in which blood clots in the legs block the blood flow there, with the clot then frequently moving to the lungs and causing pulmonary embolism (PE) and death. It's a condition that kills 100,000 Americans every year, according to Steven Galson, acting U.S. attorney general.
At a press conference on Monday, Galson put this mortality figure in scary everyday perspective: the equivalent of killing the population of Cambridge, Massachusetts — or any town of similar size. And beyond that, those who survive experience a range of complicating after-effects deteriorating their quality of life.
Galson joined with others at a press conference early Monday to ratchet up the fight against DVT and PE, attempting to alert the public to the nature of the disease and raise awareness concerning the size of the threat.
Carolyn Clancy, MD, executive director of the Agency for Healthcare Research and Quality (Washington), was on hand to report the roll-out of new publications concerning the disease.
And other participants cited new device and diagnostics weapons being developed for the therapeutic armamentarium, which so far has consisted primarily of blood-thinning drugs to break up a clot in the legs.
As one of these, a new drug/device strategy will be assessed for preventing what is called post-thrombotic syndrome (PST), a complication that follows drug treatment of DVT, according to a report by the Society of Interventional Radiology (SIR; Fairfax, Virginia). Additionally, molecular diagnostics will be used to track genetic predisposition to the device and the impact of device therapies.
The Acute Venous Thrombosis: thrombus Removal With Adjunctive Catheter-Directed Thrombolysis (ATTRACT) study will asses the combination of a clot-dissolving drug with a miniature clot removal device, catheter-mounted, to break up and remove the clot from a leg vein to restore full blood flow and avoid the follow-on complication.
Suresh Vedantham, MD, an interventional radiologist who is an associate professor at Mallinckrodt Institute of Radiology at the Washington University School of Medicine (St. Louis), is leading the study, and he described the method as a pharmaco-mechanical catheter-directed thrombolysis (PCDT) system.
Vedantham told Medical Device Daily that the methods for the total removal of clots have been shown to be effective in reducing PST but that the trials demonstrating this were small and used outdated procedures.
PST is described by SIR as a common, and irreversible, complication of DVT which causes permanent damage to the veins, and their valves, resulting in chronic leg pain, swelling, fatigue and, potentially, skin ulcers, and that from 25% to 50% of patients who suffer DVT develop this complication when treated with blood thinners alone.
The researchers say that blood thinners definitely are required to prevent DVT but that they often do not dissolve the clot entirely, resulting in blood pooling in the legs and causing the post-therapeutic complications.
Vedantham called the standard procedure using drugs a "very user-unfriendly treatment," taking 48 hours to complete infusion and often with bleeding complications.
Using the interventional approach, he said, the drug can be delivered with 'much faster results" in just two hours and at lower dosage.
He told MDD that two catheters will be used in the research: the Trellis from Bacchus Vascular (Santa Clara, California), and the AngioJet from Possis Medical (Minneapolis).
He said he expects trial enrollment to begin in the fourth quarter, "probably in November," and that it will take two and one-half years to complete, with a patient follow-up of two years. The study is being funded by more than $10 million from the National Heart, Lung and Blood Institute of the NIH, over the five-year study period.
Enrolling 692 patients at up to 28 centers in the U.S., the trial will assess the presence and severity of PTS, quality of life, relief of pain and swelling, safety and costs.
Vedantham, chair of the DVT Research Committee of SIR's Venous Forum and vice chair of a group called the Venous Disease Coalition, said that if the technique is shown to be successful it "could fundamentally shift the 50-year-old DVT treatment paradigm" to the interventional approach.
Michael Darcy, MD, chair of the board for the SIR Foundation, called the new research "critical."
He noted that SIR initiated a DVT research panel four years ago, bringing together a wide range of clinical experts who pushed the need for a trial such as ATTRACT. And SIR said that ATTRACT is the first NIH-funded, multi-center, randomized trial of any interventional DVT therapy.
This past July, the American College of Chest Physicians (ACCP; Northbrook, Illinois) published new clinical guidelines that for the first time suggest the use of PCDT for acute proximal DVT in conjunction with anticoagulation drug therapy. The ACCP's previous guideline called for use of drug therapy alone.
At Monday's press conference on the subject, Galson cited a figure of up to 600,000 people in the U.S. diagnosed with DVT every year, noting also that half of those hit with the problem have no initial symptoms. Additionally, the early symptoms of the disease are often difficult to identify, frequently suggesting a variety of other problems rather than DVT and also suggesting the need for better education of clinicians.
The risks of DVT include advancing age, a broken leg resulting in hospitalization, pregnancy, smoking, obesity or "even just traveling for several hours" – this latter having been associated with long plane flights.
The risk of DVT may be heightened by genetic factors, so that a family history of the problem may point to its increased occurrence.
Thus, Elizabeth Nabel, MD, director of the NHLBI, at Monday's conference pointed to the use of "an ongoing multi-center randomized clinical trial of phenotype-guided dosing of warfarin therapy" to link the genetic predisposition to better guidance of using warfarin.
She said that this program is complementing the work of six thrombosis and hemostasis centers "looking at the basic and clinical science behind blood clots."