DEFUSE 2 suggests extended treatment window with MRI mismatch
MedWire News: Patients with stroke who have salvageable tissue on magnetic resonance imaging (MRI) benefit from endovascular therapy even late after symptom onset, say the DEFUSE 2 investigators.
The team previously reported that the RAPID MRI post-processing program can identify patients with salvageable tissue, who are likely to have a good outcome if they achieve reperfusion.
The subanalysis, also presented at the European Stroke Conference in Lisbon, Portugal, focused only on the 78 patients who had a mismatch between their lesion sizes on perfusion- and diffusion-weighted imaging, defined as a ratio of at least 1.8. Of these patients, 36 were treated no later than 6 hours after symptom onset (median=4.8 h) and 42 were treated more than 6 hours after onset (median=7.9 h).
Fewer patients treated in the later timeframe had received intravenous thrombolysis, but otherwise they had similar characteristics to patients treated earlier, including similar lesion volumes.
However, Gregory Albers (Stanford University, California, USA), who presented the data said: "I'm going to argue that I think this population is different."
He explained that previous data have shown that patients' lesion sizes increase at different rates, presumably depending upon how good their collaterals are. This suggests that the patients who underwent imaging more than 6 hours after onset had fairly good collateral flow, which limited their lesion growth.
"We think that, with imaging, it changes the parameters of the normal 'time is brain' equation," said Albers.
The odds ratio for having a favorable 30-day clinical response (≥8 point National Institutes of Health Stroke Scale improvement or final score 0‑1) with versus without reperfusion was 2.9 in patients treated up to 6 hours after onset and 8.5 among those treated later. The difference between the odds ratios was not statistically significant.
Among patients treated up to 6 hours after onset, the rate of good 90-day functional outcomes was 59% for those who reperfused versus 29% for those who did not. The corresponding rates among patients treated later were 54% and 33%.
The median lesion growth between baseline and 5-day follow up was 41 mL in the group treated no later than 6 hours after onset, compared with 26 mL in the group treated later. This therefore supports the idea that patients with MRI mismatch at 6 hours have slow-growing lesions.
However, Albers stressed that the favorable outcomes in the latter group were not because these patients were not destined to have further lesion growth; the 14 patients with mismatch who did not reperfuse had a "dramatic and continued" median lesion growth of 108 mL.
Based on these findings, the DEFUSE team aims to initiate a randomized trial of endovascular therapy versus control treatment in MRI-selected patients up to 12 hours after stroke onset, said Albers.
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By Eleanor McDermid