Different Mismatch Concepts for Magnetic Resonance Imaging-Guided Thrombolysis in Unknown Onset Stroke.

Objective: To explore the prevalence of the perfusion-weighted imaging (PWI)-diffusion-weighted imaging (DWI) mismatch and response to intravenous thrombolysis in the WAKE-UP trial.

Methods: We performed a prespecified post hoc analysis of ischemic stroke patients screened for DWI-fluid-attenuated inversion recovery (FLAIR) mismatch in WAKE-UP who underwent PWI. We defined PWI-DWI mismatch as ischemic core volume < 70ml, mismatch volume > 10ml, and mismatch ratio > 1.2. Primary efficacy end point was a modified Rankin Scale score of 0-1 at 90 days, adjusted for age and symptom severity.

Results: Of 1,362 magnetic resonance imaging-screened patients, 431 underwent PWI. Of these, 57 (13%) had a double mismatch, 151 (35%) only a DWI-FLAIR mismatch, and 54 (13%) only a PWI-DWI mismatch. DWI-FLAIR mismatch was more prevalent than PWI-DWI mismatch (48%, 95% confidence interval [CI] = 43-53% vs 26%, 95% CI = 22-30%; p < 0.0001). Screening for either one of the mismatch profiles resulted in a yield of 61% (95% CI = 56-65%). Prevalence of PWI-DWI mismatch was similar in patients with (27%) or without (24%) DWI-FLAIR mismatch (p = 0.52). In an exploratory analysis in the small subgroup of 208 randomized patients with PWI, PWI-DWI mismatch status did not modify the treatment response (p for interaction = 0.73).

Interpretation: Evaluating both the DWI-FLAIR and PWI-DWI mismatch patterns in patients with unknown time of stroke onset will result in the highest yield of thrombolysis treatment. The treatment benefit of alteplase in patients with a DWI-FLAIR mismatch seems to be driven not merely by the presence of a PWI-DWI mismatch, although this analysis was underpowered. ANN NEUROL 2020;87:931-938.