Enzyme Prevents Stroke Disability Scientists Develop First Emergency Therapy
Neuroscientists report they have developed the first effective emergency therapy for stroke, an advance that could prevent as many as 44,000 Americans from becoming disabled each year.
The treatment involves intravenous injection of the clot-dissolving enzyme t-PA - the same enzyme used to treat clots in the heart - into patients within three hours after the onset of stroke symptoms.
In a multicenter study of 624 patients, those who received the enzyme were at least 30 percent more likely to have minimal or no disabilities than those who received a placebo, the team reports in today’s New England Journal of Medicine.
“This is the first unequivocal evidence of an effective treatment of stroke,” said neuroscientist Zach W. Hall, director of the National Institute of Neurological Disorders and Stroke, which sponsored the study. The results “signal the the beginning of a new era in which stroke will be recognized as an acute illness that can be treated.”
“Yesterday, stroke was an untreatable disease,” said Dr. James Grotta of the University of Texas, Houston, one of the principal investigators of the study. “Today, it is treatable.”
Just as importantly, he noted, the study showed that stroke must be treated as “a dire emergency” in which victims must be gotten to the hospital for treatment as quickly as possible.
T-PA’s manufacturer, Genentech Inc. of South San Francisco, said Wednesday it will apply immediately to the Food and Drug Administration for permission to market the drug as a stroke treatment. But because the drug is already approved for use in treating heart attacks, physicians can already use it for stroke if they desire.
The researchers cautioned that the t-PA can be hazardous if given to the wrong patients, if used in too high a concentration or if administration is delayed beyond three hours. “We must train physicians how to use this drug,” said Dr. Patrick Lyden of the University of California, San Diego.
If too much drug is given or treatment is delayed too long, the drug can cause hemorrhaging into the brain. In fact, 6.4 percent of the patients who received t-PA in the trial suffered from intracranial bleeding, compared with only 0.6 percent of those who received placebo. But that bleeding did not affect mortality: Only 17 percent of those who received t-PA died within 36 hours, compared to 21 percent of those who received placebo.
Stroke is the No. 1 cause of adult disability in the United States and the No. 3 cause of death. An estimated 400,000 Americans have a stroke each year. More than 3 million have suffered lasting impairment from a stroke, with at least a third of those having severe impairment, ranging from loss of speech to paralysis.
The vast majority of strokes, about 84 percent, are caused by a clot blocking a blood vessel in the brain, cutting off the flow of blood and vital oxygen to brain tissues. These are the targets for t-PA therapy. The remainder are caused by leaky or ruptured blood vessels that allow blood to escape into the brain. T-PA is not an appropriate treatment for these so-called aneurysmal strokes because bleeding is already occurring.
To distinguish between the two types of strokes, physicians use a sophisticated CT scanner to provide three-dimensional X-ray images of the brain. Fortunately, noted Grotta, emergency rooms in virtually every U.S. hospital now have CT scanners and are equipped to make such a distinction.
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This sidebar appeared with the story: WARNING SIGNS OF STROKE Sudden weakness or numbness of the face, arm or leg on one side of the body. Sudden dimness or loss of vision, especially in one eye. Trouble talking or understanding speech. Sudden severe headaches of no known cause. Unexplained dizziness, unsteadiness or sudden falls.