The purpose of the study is to evaluate the hypothesis that Trevo thrombectomy plus medical management leads to superior clinical outcomes at 90 days as compared to medical management alone in appropriately selected subjects experiencing an acute ischemic stroke when treatment is initiated within 6-24 hours after last seen well.

The study is a prospective, randomized, multi-center, Phase II/III (feasibility/pivotal), adaptive, controlled trial, designed to demonstrate that mechanical thrombectomy using the Trevo Retriever with medical management is superior to medical management alone in improving clinical outcomes at 90 days in appropriately selected wake up and late presenting acute ischemic stroke subjects.

The intent of this study is to support the use of the Trevo Retriever beyond the currently labeled 8 hour indicated time limit in wake up, unclear onset, and late presenting ischemic stroke subjects, who currently have no other option besides medical management of their symptoms.

Patients with wake-up strokes, strokes with unclear onset time, and witnessed late presenting strokes may potentially benefit from intra-arterial reperfusion therapy. However, an important indicator of whether subjects will benefit or not during this later time window is the confirmation of a large vessel occlusion (LVO), and assessment of the core infarct volume relative to the volume of salvageable penumbra. Therefore, standardized imaging selection of subjects is required for inclusion into the study.

This trial has been designed with subject safety in mind, as a seamless Phase II (feasibility) / Phase III (pivotal) adaptive design, in order to address the concerns around potential unknown harms to enrolled subjects. This study will help to answer the question of whether carefully selecting subjects by using Clinical Imaging Mismatch will allow acute ischemic stroke patients who present at or beyond 6 hours from Time Last Seen Well (TLSW) to be considered for intra-arterial intervention. If Trevo thrombectomy plus medical management leads to better clinical outcomes over medical management alone, more patients in the future could receive endovascular treatment (either in addition to or in lieu of IV tPA).

General Inclusion Criteria:

1. Clinical signs and symptoms consistent with the diagnosis of an acute ischemic stroke, and subject belongs to one of the following subgroups:

   1. Subject has failed IV t-PA therapy (defined as a confirmed persistent occlusion 60 min after administration)
   2. Subject is contraindicated for IV t-PA administration

2. Age ≥18

3. Baseline NIHSS ≥10 (assessed within one hour of measuring core infarct volume)

4. Subject can be randomized between with 6 to 24 hours after time last known well

5. No significant pre-stroke disability (pre-stroke mRS must be 0 or 1)

6. Anticipated life expectancy of at least 6 months

7. Subject willing/able to return for protocol required follow up visits

8. Subject or subject's Legally Authorized Representative (LAR) has signed the study Informed Consent form*

   • If approved by local ethics committee and country regulations, the investigator is allowed to enroll a patient utilizing emergency informed consent procedures if neither the patient nor the representative or person of trust is available to sign the informed consent form. However, as soon as possible, the patient is informed and his/her consent is requested for the possible continuation of this research. (Not applicable to U.S. Sites.)

Imaging Inclusion Criteria:

1. < 1/3 MCA territory involved, as evidenced by CT or MRI

2. Occlusion of the intracranial ICA and/or MCA-M1 as evidenced by MRA or CTA

3. Clinical Imaging Mismatch (CIM) defined as one of the following on MR-DWI or CTP-rCBF maps:

   1. 0-<21 cc core infarct and NIHSS ≥ 10 (and age ≥ 80 years old)
   2. 0-<31 cc core infarct and NIHSS ≥ 10 (and age < 80 years old)
   3. 31 cc to <51 cc core infarct and NIHSS ≥ 20 (and age < 80 years old)

General Exclusion Criteria:

1. History of severe head injury within past 90 days with residual neurological deficit, as determined by medical history
2. Rapid improvement in neurological status to an NIHSS <10 or evidence of vessel recanalization prior to randomization
3. Pre-existing neurological or psychiatric disease that would confound the neurological or functional evaluations, e.g. dementia with prescribed anti-cholinesterase inhibitor (e.g. Aricept)
4. Seizures at stroke onset if it makes the diagnosis of stroke doubtful and precludes obtaining an accurate baseline NIHSS assessment
5. Baseline blood glucose of <50mg/dL (2.78 mmol) or >400mg/dL (22.20 mmol)
6. Baseline hemoglobin counts of <7 mmol/L
7. Baseline platelet count < 50,000/uL
8. Abnormal baseline electrolyte parameters as defined by sodium concentration <130 mmol/L, potassium concentration <3 mEq/L or >6 mEq/L
9. Renal failure as defined by a serum creatinine >3.0 mg/dL (264 µmol/L) NOTE: subjects on renal dialysis may be treated regardless of serum creatinine levels
10. Known hemorrhagic diathesis, coagulation factor deficiency, or on anticoagulant therapy with INR > 3.0 or PTT > 3 times normal. Patients on factor Xa inhibitor for 24-48 hours ago must have a normal PTT.
11. Any active or recent hemorrhage within the past 30 days
12. History of severe allergy (more than rash) to contrast medium
13. Severe, sustained hypertension (Systolic Blood Pressure >185 mmHg or Diastolic Blood Pressure >110 mmHg) NOTE: If the blood pressure can be successfully reduced and maintained at the acceptable level using medication the subject can be enrolled
14. Female who is pregnant or lactating at time of admission
15. Current participation in another investigational drug or device study
16. Presumed septic embolus, or suspicion of bacterial endocarditis
17. Treatment with any cleared thrombectomy devices or other intra-arterial (neurovascular) therapies prior to randomization

Imaging Exclusion Criteria:

1. Evidence of intracranial hemorrhage on CT/MRI
2. CTA or MRA evidence of flow limiting carotid dissection, high-grade stenosis, or complete cervical carotid occlusion requiring stenting at the time of the index procedure (i.e., mechanical thrombectomy).
3. Excessive tortuosity of cervical vessels on CTA/MRA that would likely preclude device delivery/deployment
4. Suspected cerebral vasculitis based on medical history and CTA/MRA
5. Suspected aortic dissection based on medical history and CTA/MRA
6. Intracranial stent implanted in the same vascular territory that would preclude the safe deployment/removal of the Trevo device
7. Occlusions in multiple vascular territories (e.g., bilateral anterior circulation, or anterior circulation/vertebrobasilar system) as confirmed on CTA/MRA, or clinical evidence of bilateral strokes or strokes in multiple territories
8. Significant mass effect with midline shift as confirmed on CT/MRI
9. Evidence of intracranial tumor (except small meningioma) as confirmed on CT/MRI