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Ultrasound May Help Dissolve Deadly Blood Clots

Just like a spoon is used to stir sugar into a cup of tea, high-frequency sound waves may help doctors get rid of deadly blood clots in the brain, according to a study released on Wednesday.

Researchers reported they were able to increase the efficiency of Genentech Inc.’s clot dissolver t-PA by 63 percent by bathing the area in front of the clot with ultrasound while the drug went to work.

In addition, the technique seemed to reduce the likelihood of brain bleeding, a well-known risk of t-PA therapy.

"We break up clots faster, more efficiently and with less bleeding," said Andrei Alexandrov, who led the study.

Although t-PA is very effective at dissolving clots, it doesn’t work well if blood isn’t flowing. Ultrasound helps by creating turbulence in blood trapped in front of the clot -- similar to the way a person might use a spoon to add sugar to a cup of tea, Alexandrov said.

"If you don’t stir, the sugar’s going to sit there for a long time. But if you stir, the sugar dissolves very quickly," says Alexandrov, of the University of Texas-Houston.

"In the same way, t-PA cannot get where it’s supposed to be because the fluid in front of the blockage is stagnant. So your ultrasound is like a harmless spoon, and you can stir from a distance."

If proven effective in further tests, the technique could be used by most hospitals, which already have ultrasound machines comparable to the ones used in this study, he said.

However, ultrasound technicians would need a lot more training to locate clots so that ultrasound probes can be positioned properly during treatment, Alexandrov said.

The Alexandrov team studied clots in the middle cerebral artery, located on each side of the head about an inch forward and up from the temple, and about 5 centimeters (2 inches) below the skin. Clots at that site are responsible for at least 80 percent of strokes, and 80 percent of the blood flowing to a hemisphere of the brain flows through that artery.

After two hours, blocked arteries cleared in nearly a third of the 63 patients who got t-PA alone, and nearly half of the other 63, who also got ultrasound, the researchers reported.

After three months, 42 percent of the ultrasound recipients and 29 percent who got conventional care were doing well, but the number of patients checked at the three-month mark was too small to be statistically significant, which is why further tests are needed, they cautioned.

In a commentary in The New England Journal of Medicine, where the study appears, Joseph Polak of Tufts School of Medicine in Boston said the Alexandrov team has introduced "a new and exciting use of diagnostic ultrasonography."

Clots are also a major problem in the heart, but the Texas researcher said the technique was not tested there because the arteries in the heart move too much compared to the brain.

"The brain is easier to target. That’s why we made the first stab there," he said.

A follow-up study, to involve about 550 volunteers, is expected to begin in a year or two.