Intraarterial treatment for acute ischemic stroke.

To the Editor: We are encouraged by the results of the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN) by Berkhemer et al. (Jan. 1 issue)1 and the thoughtful editorial by Hacke that outlines the window of opportunity to improve stroke trials.2 One possibility is targeting patients with reversible ischemia rather than randomly assigning all patients presenting with stroke. Therapeutic windows vary among patients.3,4 The use of a fixed 6-hour window may exclude patients with reversible ischemia beyond 6 hours. This one-size-fits-all approach may also include patients with irreversible or nonviable ischemia within 6 hours, when revascularization provides no benefit but increases the risk of hemorrhage.3 As such, demonstrated therapeutic efficacy may be substantially underestimated. The penumbra is defined as reversible ischemia salvageable with prompt and successful reperfusion. In patients with successful recanalization, pretreatment perfusion imaging differentiates patients with reversible and viable ischemia up to 12 hours after onset.4 However, imaging-based identification of penumbra has been derived mostly from untreated patients. As such, advanced penumbral imaging has not had a major effect on treatment outcomes.5 Future penumbral imaging that is derived from patients who have undergone prompt reperfusion may provide a personalized window of opportunity that is not determined only by the time after onset.