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New Test Predicts Which Stroke Patients Will Be Helped or Harmed by Clot-Busting Drugs
Johns Hopkins researchers say they have developed a technique that can predict — with 95% accuracy — which stroke victims will benefit from intravenous, clot-busting therapy and which will suffer dangerous and potentially lethal bleeding in the brain.
Reporting online in Stroke, the authors say these predictions were made possible by applying a new method they developed that uses standard magnetic resonance imaging (MRI) scans to measure damage to the blood–brain barrier, which protects the brain from drug exposure.
According to the investigators, if further tests confirm their method’s accuracy, it could form the basis of expanded and more precise use of intravenous tissue plasminogen activator (tPA), a drug that is currently limited to patients who are within 4.5 hours of stroke onset, in order to have the best chance of dissolving the blood clot causing the stroke without risking additional damage.
“If we are able to replicate our findings in more patients, it will indicate we are able to identify which people are likely to have bad outcomes, improving the drug’s safety and also potentially allowing us to give the drug to patients who currently go untreated,” said lead investigator Richard Leigh, MD.
The new method is a computer program that lets physicians see how much gadolinium — the contrast material injected into a patient’s vein during an MRI scan — has leaked into the brain tissue from surrounding blood vessels. By quantifying this damage in 75 stroke patients, the researchers identified a threshold for determining how much leakage was dangerous. They then applied this threshold to those 75 records to determine how well it would predict who had suffered a brain hemorrhage and who had not. The new test correctly predicted the outcome with 95% accuracy.
Receiving tPA in a timely manner provides a significant benefit in approximately 30% of stroke patients, Leigh says. In some stroke patients — about 6% — too much damage has been done to the blood–brain barrier, and treatment with tPA can cause bleeding in the brain, severe injury, and sometimes death.
Doctors haven’t known with precision which patients are likely to suffer a drug-related bleed and which are not. In these situations, if physicians knew the extent of the damage to the blood–brain barrier, they would be able to administer treatment more safely, Leigh says.
Most stroke patients, Leigh notes, don’t get to a hospital within the window for optimal tPA use, so physicians don’t give them tPA, fearing dangerous complications. Sometimes, more aggressive treatment can be attempted, such as pulling the clot out mechanically via a catheter threaded from the groin area or by directly injecting tPA into the brain.
Typically, clinicians perform a computed tomography (CT) scan of a stroke victim to see whether he or she has visible bleeding before administering tPA. Leigh says his computer program, which works with an MRI scan, can detect subtle changes to the blood–brain barrier that are otherwise impossible to see. If his findings hold up, Leigh says, “we should probably be doing MRI scans in every stroke patient before we give tPA.”
Leigh is currently analyzing data from patients who received other treatments for stroke outside the typical time window, in some cases many hours after the FDA-approved cut-off for tPA. It’s possible, he says, that some people who come to the hospital many hours after a stroke can still benefit from tPA, the only FDA-approved treatment for ischemic stroke.
Source: Johns Hopkins; May 20, 2014.