Interventional Management of Stroke (IMS) III Trial

Inclusion Criteria * Age: 18 through 82 years (i.e., candidates must have had their 18th birthday, but not had their 83rd birthday) * Initiation of intravenous rt-PA within 3 hours of onset of stroke symptoms. Time of onset is defined as the last time when the subject was witnessed to be at baseline (i.e., subjects who have stroke symptoms upon awakening will be considered to have their onset at beginning of sleep) * An NIHSSS \>/= 10 at the time that intravenous rt-PA is begun or an NIHSSS \>7 and \<10 with an occlusion seen in M1, ICA or basilar artery on CTA at institutions where baseline CTA imaging is standard of care for acute stroke patients. * Investigator verification that the subject has received/ is receiving the correct IV rt-PA dose for the estimated weight prior to randomization Exclusion Criteria * History of stroke in the past 3 months * Previous intra-cranial hemorrhage, neoplasm, subarachnoid hemorrhage, or arteriovenous malformation * Clinical presentation suggests a subarachnoid hemorrhage, even if initial CT scan is normal * Hypertension at time of treatment; systolic BP \> 185 or diastolic \> 110 mm Hg) or aggressive measures to lower BP to below these limits are needed. * Presumed septic embolus, or suspicion of bacterial endocarditis * Presumed pericarditis, including pericarditis after acute MI * Suspicion of aortic dissection * Recent (within 30 days) surgery or biopsy of parenchymal organ * Recent (within 30 days) trauma, with internal injuries o…