Recruitment to trials of late thrombolysis: lessons from the EXTEND study

IV thrombolysis for treatment of patients with stroke upon awakening: Yes? No?

Current guidelines recommend IV administration of recombinant tissue plasminogen activator (rtPA) to carefully selected patients who can be treated within 4.5 hours of ischemic stroke onset. Patients whose neurologic symptoms are discovered upon awakening (wake-up stroke) generally are not given rtPA because of the uncertainty about the time of stroke onset. This group of patients may be relatively large. Preliminary reports suggest that patients with wake-up stroke who can be treated within 4.5 hours of discovery may respond similarly to patients with an established time of stroke onset. Clinical trials, which are selecting patients to treat primarily based on imaging surrogates, are under way. Pending the results of these trials, data about the utility of clinical or imaging findings that would identify those patients who could be treated and information about the safety and efficacy of IV rtPA in this situation are not available.

Are the current MRI criteria using the DWI-FLAIR mismatch concept for selection of patients with wake-up stroke to thrombolysis excluding too many patients?

Background

Up to 25% of stroke patients wake up with a neurological deficit, so called wake-up stroke (WUS). Different imaging approaches that may aid in the selection of patients likely to benefit from reperfusion therapy are currently under investigation. The magnetic resonance imaging (MRI) diffusion weighted imaging – fluid attenuated inversion recovery (DWI-FLAIR) mismatch concept is one proposed method for identifying patients presenting within 4.5 hours of the ischemic event.

Purpose

To report our experience with the DWI-FLAIR mismatch concept for selection of wake-up stroke patients to be thrombolysed at our centre.

Material and methods

Patients treated with off label intravenous thrombolysis (IVT) for WUS at our centre during a 6.5-month period were included. We performed MRI including DWI and FLAIR in all patients at admission. Each MRI examination was rated as either DWI-FLAIR mismatch or match. National Institutes of Health Stroke Scale (NIHSS) and modified Rankin Scale were used to measure clinical outcome. Cerebral computed tomography (CT) or MRI was performed within 24 hours after thrombolysis to determine the presence of any intracranial haemorrhage (ICH).

Results

Ten patients treated with IVT for WUS were included. Four patients had a DWI-FLAIR mismatch and after IVT treatment the mean reduction in NIHSS in the DWI-FLAIR mismatch group was 4.0. In the DWI-FLAIR match group the mean reduction in NIHSS after IVT therapy was 4.8. None of the ten patients had any signs of ICH on follow-up imaging.

Conclusions

In this small series DWI-FLAIR mismatch was not associated with worse outcome or ICH. This suggests that selecting WUS patients using DWI-FLAIR mismatch in clinical trials may exclude a large group of patients who might benefit.