title: Delayed rt-PA treatment in a rat embolic stroke model: diagnosis and prognosis of ischemic injury and hemorrhagic transformation with magnetic resonance imaging.
abstract: The authors characterized effects of late recombinant tissue plasminogen activator (rt-PA) administration in a rat embolic stroke model with magnetic resonance imaging (MRI), to assess potential MRI correlates, or predictors, or both, of rt-PA-induced hemorrhage. Diffusion-, perfusion-, and postcontrast T1-weighted MRI were performed between 4 and 9 hours and at 24 hours after embolic stroke in spontaneously hypertensive rats. Treatment with either rt-PA or saline was started 6 hours after stroke. A spectrophotometric hemoglobin assay quantified hemorrhage severity. Before treatment, relative cerebral blood flow index (rCBFi) and apparent diffusion coefficient (ADC) in the ischemic territory were 30% +/- 23% and 60% +/- 5% (of contralateral), respectively, which increased to 45% +/- 39% and 68% +/- 4% 2 hours after rt-PA. After 24 hours, rCBFi and ADC were 27% +/- 27% and 59 +/- 5%. Hemorrhage volume after 24 hours was significantly greater in rt-PA-treated animals than in controls (8.7 +/- 3.7 microL vs. 5.1 +/- 2.4 microL, P < 0.05). Before rt-PA administration, clear postcontrast T1-weighted signal intensity enhancement was evident in areas of subsequent bleeding. These areas had lower rCBFi levels than regions without hemorrhage (23% +/- 22% vs. 36% +/- 29%, P < 0.05). In conclusion, late thrombolytic therapy does not necessarily lead to successful reperfusion. Hemorrhage emerged in areas with relatively low perfusion levels and early blood-brain barrier damage. Magnetic resonance imaging may be useful for quantifying effects of thrombolytic therapy and predicting risks of hemorrhagic transformation.
authors.affiliation: Neuroprotection Research Laboratory, Departments of Radiology and Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
authors.forename: R M
authors.initials: RM
authors.lastname: Dijkhuizen
authors.forename: M
authors.initials: M
authors.lastname: Asahi
authors.forename: O
authors.initials: O
authors.lastname: Wu
authors.forename: B R
authors.initials: BR
authors.lastname: Rosen
authors.forename: E H
authors.initials: EH
authors.lastname: Lo
mesh_terms: D000818:Animals; D002545:Brain Ischemia / Q000000981:diagnostic imaging / Q000473:pathology; D002543:Cerebral Hemorrhage / Q000000981:diagnostic imaging / Q000473:pathology; D020766:Intracranial Embolism; D008279:Magnetic Resonance Imaging; D008297:Male; D011379:Prognosis; D011859:Radiography; D051381:Rats; D011918:Rats, Inbred SHR; D011994:Recombinant Proteins / Q000494:pharmacology / Q000627:therapeutic use; D020521:Stroke / Q000000981:diagnostic imaging / Q000188:drug therapy* / Q000473:pathology; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000494:pharmacology / Q000627:therapeutic use*
chemical_list: D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator