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The recent JNIS editorial, ‘The tribulations of stroke trials’,1 discusses three recent failed endovascular stroke treatment trials, including the Interventional Management of Stroke III (IMS III) trial. The authors assess the impact of these trials on patient treatment, as well as on future trials. However, some clarifications of the data presented and the statements made in that editorial regarding IMS III are needed.
The authors are incorrect to suggest that large vessel occlusion (LVO) was the ‘index disease’ for IMS III. As stated clearly in the protocol and trial design, the index disease for the IMS III trial was major ischemic stroke, as defined by the National Institutes of Health Stroke Scale (NIHSS), and the primary efficacy endpoint was a Rankin Scale score of 0–2 or functional independence at 90 days. Although the primary outcome of IMS III was not revascularization of LVO, the expectation was that endovascular therapy would revascularize those patients in the trial with LVO better than IV tissue plasminogen activator (tPA). IMS III was testing a paradigm for management, just as IMS I and II did before it. Virtually all IMS III subjects had the index disease of major ischemic stroke but not all were expected to have LVO at the time of angiography.
The authors suggest a significant per cent of subjects would/should have been excluded by imaging methods other than non-contrast CT, referring again to subjects without a LVO. At no time in IMS III was CT angiography (CTA) required as an entry criterion in the trial, and the reason for this is straightforward. At the time of the trial design and initiation, a poll of participating centers indicated that approximately 20% performed CTA as part of local standard of practice, a low figure, which gave no assurance CTA should/could be used as an …
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