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Ultrasound used on blood clots

Technique shows promise vs. stroke

The same type of sound waves that pulsate from sonar fish-finders and ultrasound fetal monitors can dramatically boost the power of anticlotting medicine and help it dissolve brain blockages in stroke patients, a study suggests.

This technique may one day offer a safe accessory for helping up to 100,000 US patients a year, about 15 percent of the nation's stroke victims, doctors said.

Dr. Joseph Polak, an imaging specialist at New England Medical Center in Boston, said more doctors should now consider adopting the technique.

"It's a relatively big impact for a disease where we don't have many options," he said.

The study and Polak's commentary appear today in The New England Journal of Medicine. The research was conducted by the University of Texas Medical School at Houston, with partners in Canada and Spain.

About 700,000 people suffer strokes each year in the United States, making it the leading cause of serious, long-term disability, according to the American Stroke Association. About 163,000 died from a stroke in 2001, third only to heart disease and cancer.

Like a heart attack within the brain, a stroke happens when a clot gets stuck in a blood vessel and cuts off circulation. The anticlotting drug TPA is sometimes given to break up the clot before brain tissue starves for lack of blood.

In recent years, research has intensified on whether ultrasound, long used to diagnose strokes, can also supercharge the clot-breaking medication. The ultrasound equipment used in the study, known as transcranial Doppler, is fairly common at major hospitals for diagnosing strokes but is rarely employed as a treatment, partly because it can take months to learn how to pinpoint clots with the lipstick-size wand.

In this experiment on 126 patients, it appeared to help break clots impressively. Within two hours, almost half of the ultrasound patients with blockage of the middle cerebral artery showed restored blood flow or dramatic recovery from symptoms. With TPA alone, only 30 percent of patients did.

Longer-term results were also favorable, though not statistically significant because of the way the study was designed. After three months, 42 percent of ultrasound patients were symptom-free or living independently, compared with only 29 percent of those treated with TPA alone.

The risk of bleeding in the brain appeared to be small and no greater than with TPA alone.

Exactly how the ultrasound works is not well understood. But researchers believe it may stir up blood near the clot, like a sonic spoon, and thus help mix in the drug. It may also help the drug bind directly to the clot.

Researchers in this study hope to take part soon in a more definitive test of the technique.

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