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| ASPECTS cut-off for thrombolysis determined |
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09 March 2006
Analysis of data from a major stroke trial has indicated that a threshold Alberta Stroke Program Early Computed Tomography (CT) Score (ASPECTS) of 7 points may be informative in the selection of patients for thrombolysis.
Dr Imanuel Dzialowski (University of Calgary, Alberta, Canada) and co-workers analysed CT data from the European-Australian Acute Stroke Study (ECASS) II, which evaluated the use of recombinant tissue plasminogen activator or placebo in 800 stroke patients within 6 hours of onset. They hypothesised that patients with extensive early ischaemic changes, defined as ASPECTS of 7 points or less, could be more vulnerable to thrombolysis-related haemorrhage.
"The ASPECTS semiquantitatively assesses early ischaemic changes within the middle cerebral artery territory using a 10-point grading system," the team explains. Using this system, 231 patients were found to have extensive early ischaemic changes, while 557 suffered less cerebral damage, with ASPECTS of more than 7 points. No association was found between dichotomised ASPECTS and functional outcome after thrombolysis, the results, published in the journal Stroke, show.
However, patients with ASPECTS of 7 points or less were 18.9 times more likely to suffer parenchymal hematoma (PH) after thrombolysis than after placebo treatment and 5.2 times more likely to experience symptomatic intracerebral hemorrhage (ICH).
In contrast, patients with higher ASPECTS were about twice as likely to suffer either of these complications after thrombolysis as they were after placebo. "It appears paradoxical that low ASPECTS does not influence treatment effect on functional outcome on one hand, but predicts risk of thrombolysis-related PH on the other," say the researchers. They suggest that PH and symptomatic ICH may not influence neurological status in patients with baseline ASPECTS of 7 or lower, due to the large extent of existing damage. Alternatively, they concede: "It is most likely that the low number of patients with ASPECTS =7 resulted in a very low power to find a clinically meaningful interaction effect." Nevertheless, Dr Dzialowski concludes: It seems to be "reasonably safe to treat patients with ASPECTS >7 up to 6 hours from stroke onset."
Reference:
Stroke 2006; 37 (4): 973-978.
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