ROME — Several relatively new percutaneous pharmacomechanical devices may have a major impact on the treatment of deep vein thrombosis, speakers predicted at the annual meeting of the Cardiovascular and Radiological Interventional Society of Europe.
Devices such as Bacchus Vascular Inc.'s Trellis and the EKOS Lysus System render tough clots more amenable to low-dose lytic therapy, albeit through very different mechanisms. The thrombus clears dramatically faster than with conventional catheter-delivered thrombolysis (CDT), which often takes 24–50 hours or more of continuous infusion conducted in an ICU or step-down unit.
And the faster thrombus clearance translates into lower hospital costs and—in the view of many interventionalists—less risk of lytic-related hemorrhage as well.
Dr. Thomas O. McNamara said both the Trellis and Lysus devices are so new to the marketplace that their optimal roles aren't defined yet. Outcome data remain scarce. But he has used both devices, and it's his impression they are particularly well-suited for treating subacute DVT of about 8–90 days' duration.
Fresh thrombus not more than a week old is often readily cleared using slow-drip CDT. But subacute clot that has begun to harden and cross-link with fibrin is much more resistant to conventional CDT. The pharmacomechanical devices thus broaden the spectrum of DVT amenable to lysis, explained Dr. McNamara, professor of radiology at the University of California, Los Angeles.
The Trellis device consists of a lytic-infusion catheter with an oscillating wire and occluding balloons at either end. The catheter is passed across the clot, the balloons above and below the thrombus are inflated, and the oscillating wire is activated for 15 minutes, during which a small quantity of a thrombolytic agent is administered at 5-minute intervals.
The oscillating wire macerates the clot, breaking it up into smaller fragments with far greater surface area. This enhances the effectiveness of lytic therapy. Meanwhile, the balloons trap the clot so it can't embolize. They also theoretically trap the lytic so it can't become systemic and cause bleeding. “I think the device does that, but not completely,” Dr. McNamara commented.
After the oscillating wire has been fired up for several 15-minute bursts, the dissolved clot is sucked out through the catheter and the balloons are deflated.
Dr. Stephen T. Kee noted that total Trellis procedure time, from access site puncture to sheath removal, is typically 1 hour to just over 2 hours, even when stenting or other adjunctive procedures are performed.
“This is a revolutionary way of treating patients that we haven't previously had. It means you can get in, get out, and go home. You don't have to keep these patients in the hospital overnight if you don't want to,” said Dr. Kee, chief of interventional radiology at UCLA Medical Center.
Dr. McNamara characterized the Trellis as “a lovely idea.” Interventionalists who have difficulty getting patients into the ICU for lengthy CDT may use it routinely as a single-session treatment. But he added that the Trellis system is too expensive to use as initial therapy for most of his patients.
One situation where the device is clearly justified, though, is in the postop patient with DVT, he continued. He has used the Trellis in 24 such patients and found it quite effective. It's not foolproof, however: One spinal fusion surgery patient required transfusion after bleeding into the buttock that was believed to be caused by systemic escape of the lytic triggering bleeding at the donor bone site.
The Lysus System combines high-frequency, low-power ultrasound with simultaneous CDT. The system includes a catheter with multiple ultrasound transducers placed 1 cm apart. The same catheter emits a thrombolytic agent in a continuous infusion through a separate channel.
The radially delivered ultrasound waves loosen the clot while driving the lytic agent deep within it. The result is accelerated thrombolysis, with an average infusion time of 24 hours or less, and lower lytic doses than in conventional CDT, said Dr. McNamara, who is a consultant to EKOS.