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.
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