How do we do that?
Tissue plasminogen activator is one of those drugs.
This is a cloned enzyme that you have normally in your body.
It seeks out clot that is in, anywhere within
the blood vessels of the body and dissolves enzymatically.
In a clinical trial that performed
testing tissue plasminogen activator, NIH researchers randomized
over 300 patients to a trial in each arm. Those who got the drug itself, t-PA
and the other half received a bolus of placebo medication.
They looked at the outcome of patients at 90 days and
in every one of the measures of clinical outcome, patients did better.
This came at a cost though.
Because TPA opens up blood vessels that have
clot in them it may also open up
damaged blood vessels and cause bleeding into the brain.
So in this study, 3% of patients who had a
hemorrhage, had a hemorrhage and died, actually from the drug.
Overall patients did better despite these hemorrhages.
But it still raises concern to us, that
giving this drug can have a hemorrhage risk.
The longer you wait to give TPA after the onset of the stroke,
the higher the risk of bleeding. It's very time sensitive.
So we don't give this drug beyond four point five
hours after the onset of neurologic symptoms for that safety reason.
What do these hemorrhages look like?
Well, here's a patient who has an ischemic stroke,
who's then develops a hemorrhage into the brain in white.
And you can see brain herniation where the brain on the
right side here is all pushed over onto the left side.
And part of that's
because of the blood that escaped from the blood vessels.
So this hemorrhagic transformation, itself, can
be a major concern using thrombolytic drugs.
In a patient who reperfuses the brain
but doesn't bleed extensively into the brain, you
can see the brain itself is just stained
with iron products from the blood that's escaped.
So, Thrombectomy is a technique where you actually mechanically remove the
clot from the brain.
This was originally tried in the 1960s, where surgeons would go and
open the middle cerebral artery itself for example and take the clot out.
That's pretty tricky to do, and was, not helpful.
But now we can do it with catheters.
So we can go from the groin up into the
brain with devices that actually ensnare the clot and remove it.