Recanalization with Stent-Retriever Devices in Patients with Wake-Up Stroke

Discussion

Recently, stent-retriever devices have been developed and play an increasing role in endovascular recanalization procedures. With these devices, high recanalization rates (89%–100%) and rapid recanalization with a good clinical outcome in a substantial number of patients can be achieved.^6,9 It has been shown that stent-retriever devices outperform conventional recanalization devices. The Solitaire with the Intention for Thrombectomy (SWIFT) trial, presented at the International Stroke Conference in New Orleans in February 2012,¹⁰ compared the angiographic and clinical results of patients with acute stroke with a symptom onset of <8 hours, who were treated with either the Merci retriever (Concentric Medical, Mountain View, California) or the Solitaire stent. The SWIFT investigators demonstrated that with the Solitaire stent, a higher vessel recanalization rate and a better functional outcome of the treated patients could be achieved.

To our knowledge, all publications describing stent-retriever recanalization include only patients with known short time windows, but no publication about the use of stent-retriever devices in patients with wake-up stroke exists.

The time interval for intravenous rtPA has been shifted from 3 to 4.5 hours after stroke onset.^11⇓–13 However, there is evidence that patients with salvageable brain tissue benefit from thrombolytic treatment up to 9 hours after stroke onset^14,15 and that thrombolysis is safe in patients with wake-up stroke.² Correspondingly, patients with wake-up stroke who have MR imaging–proved diffusion/perfusion mismatch may be candidates for endovascular mechanical interventions.

In the literature, there are only a few reports of patients who underwent endovascular acute stroke treatment within an uncertain or extended time window. Natarajan et al¹⁶ performed a retrospective review of 30 patients who underwent endovascular recanalization >8 hours after stroke onset, including wake-up stroke. In this study, endovascular intervention included various techniques such as intra-arterial thrombolysis, mechanical thrombectomy by using the Merci device or intracranial stents (no stent-retriever devices), and angioplasty, with 20% of patients presenting with mRS 0–2 at 3 months. Findings in our study are similar, with unsatisfactory outcome in most patients despite high recanalization rates.

Compared with studies evaluating thrombectomy patients with a known time of symptom onset,⁶ mRS at 90 days is less favorable in patients with wake-up stroke. This can be explained with time-dependent progression of brain cell destruction within the infarction rim zone.

However, 36.8% of our patients had an acceptable 3-month outcome (mRS 0–3), and 8 patients had an NIHSS improvement of ≥4 points (42.1%). Recanalization with stent-retriever devices was technically successful in 94.7%, which corresponds to the results of previous stent-retriever studies with a symptom onset of ≤6 hours (89%–100%^6,9). However, this recanalization rate is considerably higher than that described by Natarajan et al,¹⁶ (66.7%) who used various recanalization techniques but no stent-retriever devices for endovascular recanalization.

In our study, bleeding rates were higher than those in other interventional stroke series: Four patients presented with hemorrhage classified as sICH according to ECASS (21.1%).

As an obvious limitation of our study, the number of patients was small (n = 19), a retrospective data analysis was performed, and there was no control group.

In this series of patients with wake-up-stroke, mechanical thrombectomy with stent-retriever devices was technically successful in >90%. If one keeps in mind the severity of strokes of this cohort predominantly with CTA- or MRA-proved mainstem occlusions, favorable clinical outcome (mRS 0–2) could be achieved in 10.5%; 42.1% of patients had an NIHSS improvement of ≥4 points. Bleeding complications were higher compared with those in other interventional stroke series (21.1%).

However, our results raise the question of an improved patient selection for invasive stroke treatment, in particular for patients beyond the 4.5-hour time window. In this study, patients with wake-up stroke were referred for mechanical thrombectomy if they had a diffusion lesion of less than one-third within the territory of the middle cerebral artery and a perfusion/diffusion mismatch of >50%. These criteria also included patients with a substantial MCA infarction at the time of imaging and may explain, in part, the relatively unsatisfactory clinical outcome. The evaluation of diffusion and perfusion maps was based on visual estimation only. Furthermore, collateral supply, which probably influences the infarction extent as well, was not evaluated.

The recently presented preliminary results of the Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution (DEFUSE) 2 study¹⁷ and the Echoplanar Imaging Thrombolysis Evaluation Trial¹⁸ demonstrated that a defined target mismatch profile [PWI (time to maximum > 6 seconds) / DWI ≥1.8 and DWI < 70 mL and PWI (time to maximum > 10 seconds) < 100 mL] and a defined time to maximum threshold may predict more accurately the likelihood of cerebral ischemia and clinical outcome. Furthermore, DEFUSE 2 showed that clinicians in an emergency setting were able to analyze MR imaging profiles by using a fully automatic MR imaging analysis program (RAPID;Stanford Stroke Center, Palo Alto, California) to evaluate DWI and PWI lesions and to identify which patients have the target mismatch profile. In patients without this target mismatch profile, early reperfusion did not result in a reduction of infarct growth. In the future, such clearly predefined criteria might help to select patients who would possibly benefit from endovascular recanalization and to separate them from those patients who would only be exposed to the risks of endovascular therapy without potential improvement of their condition.