Thrombolysis benefits prevail in face of severe stroke, tissue damage
MedWire News: Intravenous thrombolysis has marked benefits in stroke patients over the age of 80 years and also benefits those who have severe stroke or early ischemic changes on imaging, subgroup analysis of the International Stroke Trial (IST)-3 confirms.
The results, presented today at the European Stroke Conference in Lisbon, Portugal, also confirm that patients derive the greatest benefits from thrombolysis if they are treated within 3 hours of onset.
The main results, presented on Tuesday, showed benefits for the cohort (n=3035) overall in the secondary, ordinal analysis, but not in the primary dichotomized outcome analysis. Although IST-3 was a randomized trial, there were some large imbalances affecting the subgroup analyses, in that older patients and those with severe stroke presented and were randomized earlier than younger patients with less severe stroke. The subgroup analyses were therefore adjusted to account for these variables.
Richard Lindley (University of Sydney, Australia), who presented the subgroup findings, said that they expected to see reduced benefit in patients older than 80 years, those with severe stroke or early ischemic changes, and those with delays to treatment.
However, there was no evidence for an interaction between early ischemic changes and treatment effect, indicating that patients with and without these changes benefited equally from treatment. There was an interaction between stroke severity and treatment, but such that patients with more severe strokes (National Institutes of Health Stroke Scale >14) seemed to derive the greatest benefit from thrombolysis.
There was also a positive interaction between age and treatment, suggesting that patients older than 80 years derived as much benefit from treatment as younger patients, if not more.
Lindley then revealed that the benefits of thrombolysis were greatest in patients treated within 2 hours of stroke onset, who were 2.2-fold more likely to have less disability with treatment than without. The size of the benefit fell to about 1.3-fold for patients treated between 2 and 3 hours after onset and remained at this low level up to 6 hours, although the benefits outweighed the harms at all times.
"So one of the ironies of the trial is that we wanted to see if treatment was beneficial up to 6 hours, but we've actually perhaps confirmed that early treatment is really very, very important," concluded Lindley.
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By Eleanor McDermid