Clinical Pearls & Morning Reports

Posted by Carla Rothaus

Published July 15, 2020


Is there evidence that mechanical thrombectomy performed more than 6 hours after stroke onset may be beneficial? 

Treatment for patients with acute ischemic stroke is guided by the time from the onset of stroke, the severity of neurologic deficit, and findings on neuroimaging. Read the NEJM Clinical Practice Article here.

Clinical Pearls

Q: What imaging test is preferred for initial evaluation in cases of suspected acute ischemic stroke?

A: Rapid onset of neurologic deficits localized to a single cerebral arterial vascular territory is the archetypal clinical presentation of acute ischemic stroke. Brain imaging is necessary to rule out intracerebral hemorrhage; noncontrast CT is preferred because of its availability, rapidity, and high sensitivity. In clinically typical cases, a noncontrast CT that shows no other explanation for the neurologic deficit is sufficient to diagnose acute ischemic stroke on initial imaging; diffusion-weighted MRI is not necessary.

Q: What conditions must be met before alteplase can be administered?

A: Before the administration of alteplase, no neuroimaging other than initial diagnostic noncontrast CT is necessary. Given the low prevalence of unsuspected coagulopathies, intravenous alteplase should be administered while the results of hematologic tests are pending if there is no reason to suspect an abnormality. On the basis of the National Institute of Neurological Disorders and Stroke trial protocol for the use of tissue plasminogen activator, the blood pressure must be lower than 185/110 mm Hg before and during infusion and lower than 180/105 mm Hg for at least the first 24 hours afterward.

Morning Report Questions

Q: Given that the benefit of alteplase is time dependent, what has been learned about the treatment window for thrombolysis with alteplase?

A: Randomized, controlled trials have shown that intravenous administration of alteplase within 4.5 hours after the onset of stroke reduces disability from acute ischemic stroke. In the WAKE-UP trial, 503 patients with a time of onset of disabling acute ischemic stroke that was unclear, but greater than 4.5 hours from the time last known to be well (94% of whom awoke with stroke), were randomly assigned to receive intravenous alteplase at a standard dose or placebo administered within 4.5 hours after the recognition of stroke symptoms. Patients were eligible if they had an abnormal signal on diffusion-weighted MRI, no visible signal change on fluid-attenuated inversion recovery imaging, a lesion on diffusion-weighted MRI that was not larger than one third of the territory of the middle cerebral artery, an NIHSS score of 25 or lower, and no planned thrombectomy. More participants in the alteplase group than in the placebo group attained the primary end point of a modified Rankin scale score of 0 or 1 at 90 days. Data from randomized, controlled trials that used imaging eligibility criteria support a benefit of late administration of intravenous alteplase (4.5 to 9.0 hours after the onset of stroke or measured from the mid-point of sleep).

Q: Is there evidence that mechanical thrombectomy performed more than 6 hours after stroke onset may be beneficial?

A: Mechanical thrombectomy, performed within 6 hours after the onset of stroke, is another first-line treatment for selected patients on the basis of multiple randomized, controlled trials that have shown a benefit. Two randomized, controlled trials have shown a benefit of mechanical thrombectomy performed at more than 6 hours after the onset of stroke in patients with an occlusion of the intracranial internal carotid artery or the first segment of the middle cerebral artery. The efficacy of mechanical thrombectomy within 6 hours after the onset of stroke is uncertain in patients who have a causative occlusion of an intracranial artery other than the internal carotid artery or the first segment of the middle cerebral artery.

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