• Efficacy: modified Rankin Scale score, dichotomized to 0-2 verses greater than 2. [ Time Frame: at 3 months from randomization ] [ Designated as safety issue: No ]
  
• Safety:(1) death due to any cause [ Time Frame: within 3 months ] [ Designated as safety issue: Yes ]
  
• (2) presence of symptomatic ICH (intracranial hemorrhage). [ Time Frame: within the first 24 (+ 6 hours) hours ] [ Designated as safety issue: Yes ]
  

• Barthel Index, NIHSSS and Trail Making Test at 3 months; early response to treatment as determined by NIHSSS of 0-2 at 24 hours from randomization; and dichotomized mRS score (0-2) versus 306 [ Time Frame: at 6, 9, and 12 months from randomization ] [ Designated as safety issue: No ]
  
• Incidence of parenchymal Type II (PH2) hematomas and any asymptomatic ICH as determined by a standard head CT scan [ Time Frame: obtained within the first 24(+ 6hours) of randomization ] [ Designated as safety issue: Yes ]
  

Stroke remains a major cause of death and disability. Acute thrombolytic therapy offers the potential to achieve early recanalization (reopening of blocked arteries), save tissues, and improve outcome. Currently, intravenous (IV) recombinant tissue plasminogen activator (rt-PA) is the only approved acute stroke therapy. IV rt-PA is an effective therapy for acute ischemic stroke but has substantial limitations when used alone to open blocked arteries The Interventional Management of Stroke (IMS III) Trial is a multi-center study that will compare two different treatment approaches for restoring blood flow to the brain. One approach, giving the clot-dissolving drug rt-PA, is already FDA-approved when given through a vein (IV). This treatment will be compared to a new approach, giving rt-PA at a lower dose first through IV in the arm and then, if a blood clot in the brain artery is found, through a small tube or catheter at the site of the blood clot (intra-arterial or IA) to see which is better. Both approaches must be initiated within three hours of stroke onset.

The primary goal of this trial is to determine if individuals with ischemic stroke treated with rt-PA using a combined IV/IA approach to recanalization started within 3 hours of onset are more likely to have a better outcome than individuals treated with standard IV rt-PA alone.

Nine hundred participants with moderate to severe ischemic stroke will be enrolled at more than 50 centers in the United States, Canada, Australia and Europe.

Subjects will be randomized in a 2:1 ratio with more subjects enrolled in the combined IV/IA group. If enrolled under Amendment 5 or later both treatment groups will receive the standard approved therapy dose of rt-PA (0.9 mg/kg, 90 mg max) administered intravenously over one hour. The consent process and randomization can take place prior to or anytime up to forty minutes after the IV bolus dose. If, at the 40 minute time point, no consent has been obtained or randomization has not been completed, the patient will no longer be eligible for IMS III enrollment. After consent, the combined IV/IA group will then undergo immediate angiography. If clot is not demonstrated, no more treatment is administered.

If clot is demonstrated, the neurointerventionalist will then choose from currently available but trial defined intra-arterial treatment approaches, choosing the treatment they feel will be most effective in attempting to reopen the blocked artery. These approaches utilize local regulatory, US FDA and IMS III Executive Committee approved devices for the intra-arterial infusion of investigational rt-PA using standard microcatheter or the EKOS Micro-Infusion Catheter® (in US) or embolectomy devices including the Concentric Retriever Device®, the Penumbra System ™, or the Solitaire™ FR Revascularization Device. All devices must be used per the manufacturer's instructions for use. Intra-arterial therapy, whether initially with the Merci® Retriever, EKOS Micro-Infusion Catheter, Penumbra System™, Solitaire™, a future device, or infusion of IA rt-PA via a standard microcatheter, must be started within 5 hours and completed within 7 hours of symptom onset. The maximum dose of IA rt-PA is 22mg (maximum 2 to 4 mg bolus and infusion at a rate of 10 mg/hr). Use of tandem devices (i.e. EKOS Micro-Infusion Catheter, Merci Retriever®, Penumbra System™, or Solitaire™) in a single case is a protocol violation. Only standard microcatheter rt-PA infusion therapy may be administered following attempt with a device.

The primary measure of benefit in this trial is the ability of the individual with stroke to live and function independently 3 months after the stroke. This trial will also determine and compare the safety and cost effectiveness of the combined IV/IA approach to the standard IV rt-PA approach.

Duration of the study for participants is approximately 12 months.