Ultrasound-enhanced thrombolysis

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Also introduced at ISET was a new ultrasound device that dissolves clots faster, more easily and more safely than conventional methods. The Lysus Ultrasound Infusion (developed by Ekos) is composed of tiny transducers that emit sound waves that loosen the fibrin and push conventional clot-busting drugs into the clot, encouraging it to dissolve faster.

Currently, clot-busting drugs are infused at the site of the clot, whether in the leg or pelvic arteries (where it is known as a peripheral arterial occlusion or PAO) or thigh veins (deep vein thrombosis or DVT). The current infusion process can take up to 48 hours, particularly if the clot is large. The longer the infusion, the greater the risk of limb- or life-threatening bleeding elsewhere in the body, particularly the brain. Also, patients are immobilized and must be treated in monitored care beds, which increases costs.

The new device delivers drugs in the same manner as the conventional catheter system, with the addition of a central wire that has tiny ultrasound transducers situated half an inch apart on the wire. Each device has from six to 30 transducers, depending on the size of the clot. When the drug is delivered, the transducers emit high-frequency, low-energy ultrasound waves to both loosen up the fibers and force the drug throughout the clot. The more fibrin the drug touches, the better and faster the clot dissolves.

Dr Keith M Sterling, Cardiovascular & Interventional Associates, VA, presented data from a 13-center ongoing observational study involving clots in 99 patients: 66 with PAOs and 33 with DVT. In the PAO group, 1.3% of patients experienced major bleeding after treatment with the ultrasound-enhanced delivery system. The bleeding caused bruising but was not fatal. After 17.5 hours of treatment with the new system, clots were completely dissolved in 58 patients of the 66 (88%). Comparatively, a study found 68% of patients’ clots were completely dissolved 24.4 hours after conventional treatment, and the major bleeding rate was 12.5%. Overall, ultrasound-enhanced delivery resulted in a 28% improvement in dissolution of clots and a 92% reduction in bleeding complications compared to conventional treatment.

Data on 33 DVT patients were also presented at ISET. Results showed that 5% suffered non-fatal major bleeding that caused bruising. After 23.3 hours, clots were completely dissolved in 23 of the patients (7%). In DVT studies of conventional clot-busting therapy, 31-38% of clots were completely dissolved after 36.8 to 53.4 hours and 11.4% had major bleeding. Ultrasound-enhanced delivery more than doubled the number of patients whose clots were completely dissolved and resulted in a 56% reduction in bleeding complications compared to conventional treatment.

“This device is exciting because it enhances the ability to dissolve clots and may lead to a procedure with fewer complications,” said Dr James F Benenati, medical director of the peripheral vascular laboratory Baptist Cardiac & Vascular Institute, Miami, one of the sites in the on-going study. “It also may have the advantage of allowing the procedure to be done much more quickly, which will save physicians and hospitals time, and lower the cost of the procedure.”

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