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Breaking Up Clots At The Speed Of Light

February 14, 2000
American Heart Association
The first use of lasers as a treatment to remove stroke-causing blood clots was reported in a study here at the American Stroke Association's 25th International Stroke Conference.

NEW ORLEANS (Feb. 10, 2000) -- The first use of lasers as a treatment to remove stroke-causing blood clots was reported in a study here today at the American Stroke Association's 25th International Stroke Conference.

The American Stroke Association is a division of the American Heart Association.

A team led by Wayne M. Clark, M.D., of the Oregon Stroke Center in Portland, Ore., discussed preliminary results on five stroke patients they have treated with an experimental procedure involving the use of lasers to "vaporize" clots in the carotid arteries, the vessels that supply blood to the brain.

The researchers say their study represents the first use of laser clot-busting, or thrombolysis, in stroke patients. The study is designed to examine the safety of the technique and the scientists add there is much to be done before determining whether patients show improvements following laser treatment. "It looks very promising," says Clark. "But at this point, we're mainly studying the safety. We have achieved complete vessel re-opening in some patients, while in others, treatment was not possible due to difficulties getting to the clot with the laser-tipped catheter."

Clark adds that mechanical clot removal -- whether it's the use of lasers, clot-suction devices, or other means by which to physically remove the obstruction -- could be the next wave of acute stroke treatment.

"We don"t know which device or which technique will be the answer, but I think it is reasonable to say that five years from now, mechanical clot disruption will be a major factor in the treatment of acute stroke," he says. "Particularly in patients with larger strokes, this type of treatment could be useful.

"Regardless of what type of mechanical disruption you're using, the opportunity is there to remove the clot instantly, in minutes instead of hours, theoretically," adds Clark. "We do not have the necessary data on this yet, which is why we are moving forward cautiously."

Patients studied had to be given the treatment within 8 to 24 hours of a stroke, depending on the location of the stroke. If the stroke was in the anterior carotid artery, it had to be treated within eight hours. A stroke caused by a blockage in the posterior carotid artery had to be treated within 24 hours. Researchers also took into consideration the stroke's severity, using the National Institute of Health Stroke Score, which measures a patient's motor skills, language capability and other factors.

Currently, the only federally-approved acute treatment for stroke caused by blood clots is a clot-dissolving drug called tissue plasminogen activator (TPA), which must be administered within three hours of stroke onset to be effective.

"It is still very true that 'time is brain,' but we hope that through treatments like this one, we can provide a longer time window for stroke treatment," says Clark.

The laser procedure is not as simple as aiming a laser at a person's neck and "zapping" the clot away.

After it has been determined by medical personnel at the hospital that a person has had a stroke caused by a blood clot, the cause of about 80 percent of strokes, a catheter equipped with a laser is threaded through the vessels to the exact spot of the clot. The physician can see where the catheter is by use of an angiogram -- a widely-used imaging technique which gives a "picture" of what's going on inside the blood vessels.

The physician then must move the laser tip to within a centimeter of the clot for the system to work. The laser is activated and the light is drawn only to the components of the blood clot, which is composed of various proteins, red blood cells and other particles. Light and energy are only created where there is red -- the color of the clot -- not in the white walls of the vessel surrounding the clot.

"The light only causes energy when it hits something red," adds Clark. "The laser will hit the clot and vaporize it."


Co-authors are Lisa A. Buckley, M.D.; Gary M. Nesbit, M.D.; Helmi L. Lutsep, M.D.; Stanley L. Barnwell, M.D.; Anne J. Doherty, R.N.; and Kenton W. Gregory, M.D.; all of the Oregon Stroke Center.

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Materials provided by American Heart Association. Note: Content may be edited for style and length.

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American Heart Association. "Breaking Up Clots At The Speed Of Light." ScienceDaily. ScienceDaily, 14 February 2000. <>.
American Heart Association. (2000, February 14). Breaking Up Clots At The Speed Of Light. ScienceDaily. Retrieved July 18, 2024 from
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