Modern Medicine

Why is clot-busting medicine rarely used on brain blood clots?
Answered by Susan Sherwood and Discovery Fit & Health
  • Susan Sherwood

    Susan Sherwood

  • Discovery Fit & Health

    Discovery Fit & Health

  1. A stroke is potentially life threatening, perhaps more serious than a heart attack. During a stroke (a.k.a., a brain attack) blood flow within the brain is impeded. This can be caused by a burst blood vessel (hemorrhagic stroke) or, much more commonly, by a blood clot in a vessel or artery (ischemic stroke). The lack of blood flow kills brain cells, and the longer blood delivery is interrupted, the more severe and lasting the effects.

    Treatment for a ischemic stroke can include a drug that dissolves blood clots, but only if used within three hours of the onset of symptoms. The drug is a genetically engineered (recombinant) version of a naturally occurring enzyme (t-PA) that enables clot dissolution. The drug, rt-PA, significantly helps reduce stroke recovery time; after three months most patients have recuperated.

    Though highly effective, rt-PA is often not prescribed because of the small time window in which it must be administered. Unfortunately, many victims do not recognize the symptoms of a stroke, so medical attention is postponed, the average delay 24 hours.

    If rt-PA is inadvisable, what other treatments are offered? If the three-hour limit has passed or a patient is otherwise ineligible for rt-PA, the MERCI Retrieval System can be used at any time. The device is inserted into the brain where it enfolds and removes the clot . The Penumbra System, another option, has a more limited time frame (within eight hours of symptom onset), but it can successfully suction out clots and reinstate blood flow.

    There are also new treatments under development. Neuroprotectives are used in conjunction with rt-PA and with the same time limitations. While the rt-PA dissolves blood clots, neuroprotectives prevent brain cell death in the areas adjacent to the stroke.

    Neuroperfusion, for its part, creates a detour for the circulatory system. Near the site of the stroke the direction of blood flow is reversed, allowing unaffected veins to carry blood drawn from an artery and deliver it to oxygen-starved brain cells.

    Finally, one unexpected use for blood substitutes may be stroke treatment. Although originally developed to address safety and shortage issues, blood substitutes might be used to carry oxygen to brain cells injured by the stroke.

    In the end, while medical treatment for a stroke has advanced greatly, nothing is more effective than getting help fast.

    Artificial Blood 2
    Red blood cells, also called erythrocytes, are shaped like biconcave discs (Photo courtesy Garrigan.net)

     

     

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  2. During an ischemic stroke, or brain attack, blood clots block the flow of oxygen into your brain. As soon as your brain is deprived of oxygen and nutrients, the brain cells begin to die. As different parts of your brain die, you'll begin to lose some bodily functions such as movement, speech or vision. The brain begins to die fairly quickly, so getting immediate treatment for a brain attack is critical to maintaining the full functions of your brain after the attack.

    Although tissue plasminogen activator, or tPA, was approved by the Food and Drug Administration for use in dissolving brain blood clots in 1996, only one in five patients who could benefit from tPA actually receive it [source: Brody]. That's because tPA has to be administered to the patient within three hours after symptoms of a stroke begin to appear. After that, tPA can do more harm than good by causing bleeding in the brain. Unfortunately, most stroke patients don't make it to the hospital within this three-hour window.

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