Ask your doctor if you fall into this category.
http://www.medpagetoday.com/Cardiology/Strokes/36024
Individuals who are resistant to aspirin's antiplatelet effects
appear to have more severe ischemic strokes than those who respond to
the drug, researchers found.
Among patients admitted with an acute stroke, those shown to be
resistant to aspirin with a platelet function assay were significantly
more likely to have an NIH Stroke Scale (NIHSS) score of 16 or higher on
admission (OR 7.49, 95% CI 1.49 to 48.00), the cutoff for severe
stroke, according to Bernard Yan, MD, of Royal Melbourne Hospital in
Parkville, Australia, and colleagues.
In addition, resistant patients were more likely to have an Alberta
Stroke Program Early CT Score (ASPECTS) of less than 7 (OR 60.0, 95% CI
10.5 to 343.2), indicating a large area of infarction, the researchers
reported online in Archives of Neurology.
"Our results support the need for a randomized controlled study to
investigate alternative antiplatelet therapy in patients with aspirin
resistance," they wrote.
The use of aspirin before a stroke has been associated with less
severe symptoms at admission and improved functional outcomes at
discharge. And short-term aspirin therapy has been shown to
significantly reduce the risks of death and dependency at 6 months
following an acute ischemic stroke.
Resistance to aspirin, however, may contribute to poor clinical outcomes in some patients.
Yan and colleagues explored the issue using data from 90 adult
patients admitted with an acute ischemic stroke at their center. All had
been using aspirin for at least 7 days before stroke onset (median 5
years).
The mean age of the patients was 75, and 64.4% were male.
At admission, the median NIHSS score was 4, indicating minor
symptoms. The median ASPECTS was 9, indicating a small area of
infarction (the maximum score of 10 indicates a normal CT scan).
As measured by the VerifyNow assay, 28.9% of the patients were
resistant to aspirin, defined as an aspirin reaction unit (ARU) of 550
or higher. The median ARU for the entire cohort was 486.
Each 1-point increase in ARU was associated with a 0.03-point increase in NIHSS score (P=0.001) and a 0.02-point decrease in ASPECTS (P less than 0.001).
That works out to a 1-point increase in NIHSS score for a 33-point
increase in ARU and a 1-point decrease in ASPECTS for a 50-point
increase in ARU.
The presence of aspirin resistance was associated with a worse stroke according to both the NIHSS and ASPECTS.
"Platelets are critical to thrombus formation, contributing as much
as 50% of the total thrombus volume. Antiplatelet agents decrease
platelet aggregation and, in turn, the size and frequency of
thrombolytic emboli," the authors wrote.
Thus, they said, "the increased severity and infarct size observed in
the present study may be due to larger thrombus formation as a result
of inadequate platelet inhibition."
"Aspirin also reduces platelet microaggregates and platelet-derived
vasoconstricting products," they added. "This may ease ischemic injury
by improving local blood flow. Aspirin-resistant patients may not
experience the same therapeutic effect and, as a result, sustain a
larger stroke."
Alternatively, other neuroprotective or anti-inflammatory processes
could be involved in the observed relationship, Yan and colleagues
noted.
They acknowledged that their study was limited by the small sample
size, the slight selection bias favoring patients with milder symptoms,
and the possible insensitivity of ASPECTS to early ischemic changes.
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