Aspirin: A Risk for Hemorrhagic Stroke?

As we discussed in class last week and Allison also mentions in her blog, there are two main classes or types of stroke.  They are hemorrhagic and ischemic; ischemic is the vast majority of all stroke cases.  It accounts for about 87% of stroke cases according to www.strokeassociation.org.  Ischemic stroke is where there is a blockage in the blood vessel.  Hemorrhagic stroke is where a blood vessel around the brain is ruptured and bleeding around or in the brain occurs.  This rupture is called an aneurysm.  This post will be focusing on hemorrhagic stroke.  It will also discuss aspirin, a common drug given to aid prevention of cardiovascular and ischemic occurences, and its possibility as a risk factor for hemorrhagic stroke.  Hemorrhagic stroke is more uncommon than ischemic, but it has a higher fatality rate.

            Inside of the category of hemorrhagic stroke, there are two subgroups.  These are intracerebral hemorrhage and subarachnoid hemorrhage.  Intracerebral is exactly what it sounds like; it is bleeding inside of the brain.  Subarachnoid hemorrhage is bleeding in the space between the brain and the skull.  Blood causes brain tissue irritation and swelling.  A common cause for hemorrhagic stroke is high blood pressure, which eventually causes enough stress on the arteries that they rupture.  Testing for hemorrhagic stroke is usually accomplished by a CT scan of the brain.  This will show the hemorrhage, if there is one in the brain.  An MRI can also be used, however CT scans are the most common way to determine a hemorrhage in the brain.

            As many of us know, aspirin is a very common drug given to people who want to prevent heart disease, ischemic stroke, and heart attacks.  Aspirin is an NSAID and it has an effect on platelets that leads to a decrease in their aggregation.  This decrease in platelet aggregation means there is less chance a blockage will form.  More specifically, aspirin bind irreversibly to platelet COX-1, cyclooxygenase-1, to inhibit it.  COX-1 is a vasoconstrictor and causes platelet aggregation (Stroke, pg 1801).  This means that should bleeding occur, it will be much harder to stop because clots are less likely to form.  This makes sense then, that aspirin could be a risk factor for hemorrhagic stroke and other bleeding events.  The article “Risk of Hemorrhagic Stroke With Aspirin Use” discusses aspirin and resulting trials to test for an increased risk of hemorrhagic stroke when the patients were using aspirin.  They found that “in 11 of the 13 trials reporting hemorrhagic stroke, aspirin was associated with an increase in absolute risk of hemorrhagic stroke” (Stroke, 1802).  They also discuss that hypertension is the leading cause of hemorrhagic stroke, and state that the magnitude of the benefit in reducing blood pressure from aspirin far outweighs the risk.  It seems to me that since hypertension is such a large part in inducing hemorrhages in the brain, that although aspirin could be a risk factor for hemorrhagic stroke, its role at reducing blood pressure and preventing heart attack and ischemia is much more valuable and important.  It is definitely something to think about as far as a risk factor for this type of stroke, however I do think that the good benefits from aspirin outweigh the very low risk of hemorrhagic stroke. 

References

Gorelick, P. B.. "Risk Of Hemorrhagic Stroke With Aspirin Use: An Update."Stroke 36.8 (2005): 1801-1807. http://stroke.ahajournals.org/content/36/8/1801.full.pdf+html

http://www.nytimes.com/health/guides/disease/hemorrhagic-stroke/overview.html

http://www.uptodate.com/contents/hemorrhagic-stroke-treatment-beyond-the-basics