What is laser clot busting?


This clot needs busting so that blood flow to the brain can be restored.
This clot needs busting so that blood flow to the brain can be restored.
3D Clinic/Getty Images

Laser clot busting might sound like something you do in a video game, but you're not likely to see the game Brain Attack at an arcade near you anytime soon. Haven't heard of Brain Attack? Here's how it's played: The goal of the game is to maintain as many points as possible -- points in this game are symbolized by the cells in your brain. You drop your quarter in the game, which leads the enemy, the blood clot, to strike. The clot stops blood flow to the brain, and the brain is instantly deprived of oxygen and nutrients. Now you're going to start losing points -- your brain cells are dying. "Ischemic stroke" the screen flashes. With each lost point, you're losing whatever bodily function that part of the brain controls, be it movement, speech or vision. Time is ticking. What do you do?

If this was a real video game, you might have lots of weapons at your disposal to bust up that clot. But an ischemic stroke, sometimes known as a brain attack, is no game. An ischemic stroke is a type of stroke caused by a blood clot. Time is still of the essence so that brain cells can be saved and brain damage minimized. But right now, there's only one weapon in a doctor's clot-busting arsenal. That weapon is tissue plasminogen activator, or tPA. The drug tPA was approved by the FDA for use in 1996. It's intravenously administered and it works to dissolve the clot so that blood can flow again.

But for being a doctor's major weapon in a brain attack, tPA is very rarely used. Only one in five patients that could benefit from the drug actually receives it [source: Brody]. The drug only has a three-hour window in which it can be administered after symptoms of a stroke start to appear, and many patients simply don't make it to the hospital in time. After that window, tPA may cause bleeding in the brain.

Scientists are studying several new treatments for stroke that could both elongate that treatment window and break up the clot faster. One of those methods is laser clot busting, which despite its video game-ready name, would actually be more akin to a game of Operation. In the game Operation, players try to extract organs, bones and other items without touching the sides of a bodily cavity. In laser clot busting, doctors would be trying to bust up a clot without breaking the surrounding blood vessel.

Turn the page to find out more about how this treatment might work.

Laser Clot Busting Devices

Doctors will use brain imaging to place the laser near the blood clot.
Doctors will use brain imaging to place the laser near the blood clot.
John Coletti/The Image Bank/Getty Images

In 1994, the Lawrence Livermore National Laboratory identified lasers as a main focus in developing stroke treatments. The challenge in developing and using a laser is determining how strong the pulse of the laser should be in order to effectively bust up the clot without breaking the vessel walls. That's no small feat when you consider that the vessels in the brain are much narrower than other vessels in the body; they're also fairly fragile. Two types of laser clot busters have been tested so far that differ in how they apply a laser's force.

The first method is the LaTIS laser device, which, depending on the location of the clot, could be used on a patient 8 to 24 hours after their stroke symptoms appeared. The laser is encased in a catheter, which is inserted in the groin and guided through the body to the brain. Doctors can monitor the catheter's progress in relation to the location of the blood clot through an imaging device such as angiogram. The doctors then push the catheter through the blood clot. As they pull the catheter back, they fire the laser. The laser is able to sense color and light so that it only fires at the red of the blood clot, as opposed to the white vessel wall.

In 2000, scientists at the Oregon Stroke Center revealed that they had been able to vaporize a blood clot in just 49 seconds with this device, as compared to a couple of hours for tPA to dissolve a clot [source: Peck]. However, follow-up testing has had limited success, due to problems inserting the catheter.

The LaTIS laser device is fired in powerful one second long pulses to break up the clot. Another method uses a less powerful laser that is fired at the rate of about one thousand pulses per second to attack the clot. This method is the Endovascular Photo Acoustic Recanalization (EPAR) Laser. Though it involves a laser, this laser isn't directly busting the clot. Rather, the laser's energy is converted to acoustic energy. This creates tiny bubbles at the tip of the catheter, and the expansion and collapse of the bubbles suck in the clot.

In testing the EPAR device, there have also been issues related to catheter insertion, but there have been no problems during the actual lasering [source: Leary et al]. In the first testing of EPAR, the device was used on 26 patients, 6 to 24 hours after their symptoms began, with a recanalization rate of 48 percent [source: Leary et al]. Recanalization is the process of opening the vessel to restore blood flow. In follow-up testing of 34 patients, results were slightly lower. In that test, 41 percent of the group demonstrated recanalization [source: Berlis et al].

These results may make it seem like laser testing isn't that successful, but it's important to remember that these results are extremely preliminary. Much more research and development is underway, but the takeaway is that in certain cases, laser treatment is feasible. That's a huge step forward in the fight against brain damage caused by stroke.

In addition to lasers, several other mechanical means of removing clots have been tested. These include an ultrasound device that could change the structure of a clot, making it easier for intravenous drugs to do their work; a corkscrew inside a catheter that could pull out a clot; a jet inside a catheter that creates a clot-busting vacuum by spraying a saline solution at high pressures; and a catheter outfitted with a vacuum to suck in the clot and blades to chop it up.

To learn more about your brain, blood and lasers, see the links on the next page.

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Sources

  • Berlis, Ansgar, Helmi Lutsep, Stan Barnwell, Alexander Norbash, Lawrence Wechsler, Charles A. Jungreis, Andrew Woolfenden, Gary Redekop, Marius Hartmann, Martin Schumacher. "Mechanical Thrombolysis in Acute Ischemic Stroke with Endovascular Photoacoustic Recanalization." Stroke. May 2004. (July 8, 2008) http://stroke.ahajournals.org/cgi/content/full/35/5/1112
  • Brody, Jane E. "With Strokes, Knowledge is a Lifesaver." New York Times. Dec. 12, 2006. (July 8, 2008) http://www.nytimes.com/2006/12/12/health/12brody.html
  • Leary, Megan C., Jeffrey L. Saver, Y. Pierre Gobin, Reza Jahan, Gary R. Duckwiler, Fernando Vinuela, Chelsea S. Kidwell, John Frazee, Sidney Starkman. "Beyond Tissue Plasminogen Activator: Mechanical Intervention in Acute Stroke." Annals of Emergency Medicine. June 2003. (July 8, 2008) http://138.5.102.101/emergency_medicine/pdf.docs/interventions%20for%20CVA.pdf
  • Lutsep, Helmi L. "Mechanical Thrombolysis in Acute Stroke." WebMD. Nov. 2, 2006. (July 8, 2008) http://www.emedicine.com/neuro/TOPIC702.HTM
  • Peck, Peggy. "Laser Blasts Blood Clot in 49 Seconds." WebMD Health News. Feb. 10, 2000. (July 8, 2008) http://www.webmd.com/news/20000210/laser-blasts-blood-clot-in-49-seconds
  • Wheatcraft, Dean. "On the Offensive against Brain Attack." Science & Technology Review. June 1997. https://www.llnl.gov/str/Fitch.html