Laser Blasts Blood Clot in 49 Seconds

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Feb. 10, 2000 (New Orleans) -- Welcome to 'Star Wars' medicine. Here a clot that cuts off the blood supply to the brain, causing a massive stroke, is vaporized in just 49 seconds by a tiny laser placed in a catheter that is threaded through the body and up into the carotid artery, which supplies blood to the brain. In Portland, Ore., a team of stroke specialists successfully reversed the course of a massive stroke in a 78-year-old woman using this latest high-tech approach.

William M. Clark, MD, associate professor of neurology at Oregon Health Sciences University, reported the successful intervention at a press conference yesterday at the 25th International Stroke Conference. Clark, director of the Oregon Stroke Center, tells WebMD, "I'm convinced that mechanical clot removal is the wave of the future." He says that several types of mechanical clot removal systems -- laser, vacuum removal, and sound wave systems -- are currently being studied and he predicts that "in five years we will be using these systems in clinical practice."


Although he presented very early findings from a laser safety study, Clark says he is also participating in a study of a device called Angio Jett. "This is a very nice device, it shoots out a stream of water, thus creating a vacuum that just sucks the clot right up," he says. Still another mechanical device now undergoing a safety study is a laser that uses a much lower energy but much higher frequency. "It's like using either a big punch or a lot of little jabs to get the job done," he says.

In the study reported yesterday, Clark's team received FDA approval to enroll 12 patients in a safety trial of the LaTIS Neuro Laser Thrombolysis System. The team first identifies and locates a clot using complex X-rays and then "threads the laser catheter from the groin up to the carotid," he says. The laser catheter is first pushed through the clot and then the laser is "fired" as the laser is pulled back through the clot," says Clark. "Using this method we hope to cut down on any possibility that smaller parts of the clot will break off and cause additional damage," he says.


Clark says one advantage of the laser used in this trial is that "it is designed to only interact with things that are red, so while it will affect the red clot, it leaves the white vessel wall untouched." He says this is very vividly demonstrated with an apple. "You put the laser inside the white flesh of the apple, fire it, and nothing happens. Aim at the red skin, however, and it will be vaporized," he says.

Clark says one potential advantage of the mechanical systems is that they have a larger time window than clot-busting medications. The clot-buster, known as tPA, has to be given within three hours of the onset of stroke, whereas mechanical removal can be done within eight to 24 hours, depending on where the clot is, says Clark. The patient in whom the intervention was successful had the laser procedure at four and a half hours after stroke onset.

Clark's team had to redesign the catheter after they discovered that it was too stiff, making it unable to pass through the blood vessels of two different patients. In one of the three patients attempted after the redesign, there was significant bleeding. Clark says that the team then "decided to halt the trial because of safety concerns."


In the interim, he says that the team has decided to modify the procedure by decreasing the energy and increasing the frequency of the laser. He says they are now awaiting FDA approval for the safety trial to continue at the lower energy level and higher frequency. "We expect approval within about a month and will restart the trial this spring," he says.

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