A tiny clot-buster
If victims of severe strokes are to avoid serious brain damage or death, they must be treated within hours of developing symptoms.
Yet only one drug is known to dissolve the blood clots that cause most strokes, and it isn’t suitable for many patients. Strokes kill 168,000 Americans each year and are the leading cause of permanent disability.
Now a few doctors are using an experimental corkscrew-like tool, invented by UCLA researchers, to manually extract the clots that deprive the brain of the oxygen it needs to survive.
“This device could save lots of lives and lessen the level of disability so people can go home, rather than being institutionalized,” says Dr. Marilyn Rymer, a spokeswoman for the National Stroke Assn. in Englewood, Colo.
Called the MERCI Retriever, the tool has been tested on people ineligible for the current therapy for stroke, t-PA (Activase), a clot-busting drug that is given intravenously. The drug is given to only 2% to 5% of stroke victims because it must be used within three hours of the onset of the stroke.
Stroke is difficult to diagnose, however, and victims often come to the hospital too late. Furthermore, the drug doesn’t dissolve big clots; it can take an hour or more to work; and it can’t be used on patients who are prone to bleeding because it can cause cerebral hemorrhages.
In contrast, the Retriever can be used up to eight hours after a stroke; it can yank out larger clots; and it can remove the blockage immediately, potentially preserving more brain tissue than t-PA because it works much faster.
“Because of the bigger therapeutic window, we can now offer treatment to 27% of patients instead of just 2%,” says Rymer, medical director of the stroke center at Mid America Brain & Stroke Institute at Saint Luke’s Health System in Kansas City, Mo.
The MERCI Retriever is a thin tube that contains a wire made of a metal alloy that is able to change shape. The device is threaded inside a blood vessel at the groin and pushed through the body into the brain. Once the device reaches the clot, the wire is pushed out of the tube, coiling into a corkscrew shape that latches on to the clot -- much the way a corkscrew does in a bottle of wine. A tiny balloon simultaneously inflates to halt blood flow and prevent a second stroke if a piece of the clot breaks off before it is removed. Doctors then gently pull the wire to dislodge the clot, which is sucked out of the body with the aid of a syringe.
Tests conducted at UCLA over the last two years have been encouraging. One-fourth of patients who had a severe stroke “were able to resume normal lives almost immediately without rehabilitation,” says Dr. Sidney Starkman, co-director of the UCLA Stroke Center and head of the team that studied the Retriever. Although two-thirds died or were left seriously disabled, he says, normally “the death rate is close to half, and most survivors need constant care.”
The first UCLA patient, for instance, had been paralyzed for six hours. After doctors pulled out the clot, the man began speaking while still on the operating table; he completely recovered. “We were flabbergasted,” says Starkman.
A larger study, of 110 patients who were ineligible for t-PA, was recently conducted at 25 U.S. stroke centers; those results will be released early next month. If all goes well, the device could be available this spring at about 100 hospitals that have stroke specialists trained to use the Retriever, says Gary Curtis, chief executive of Concentric Medical Inc. The Mountain View, Calif., company makes the device.
Further study is needed to determine how many patients will ultimately benefit. “We’re excited about having another weapon in our treatment arsenal,” says Dr. Joseph P. Broderick, a neurologist at the University of Cincinnati College of Medicine. “But it shouldn’t be overplayed as the salvation for acute ischemic stroke, and more research needs to be done.”
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Know the signs and act quickly
For stroke victims, time is of the essence. “Every minute that goes by could mean the destruction of brain areas crucial to normal functioning,” says Dr. Sidney Starkman. Recognizing the signs of a stroke, and acting quickly, can greatly improve your chances of getting lifesaving treatment.
If you or someone you know is experiencing these symptoms, call 911:
* Sudden numbness or weakness of the face, arm or leg, especially on one side of the body.
* Sudden confusion; trouble speaking or understanding.
* Sudden trouble seeing in one or both eyes.
* Sudden trouble walking, dizziness, loss of balance or coordination.
* Sudden severe headache with no known cause.
