Thrombolysis of cerebral clot embolism in rat: effect of treatment delay

RATS submitted to focal cerebral ischemia by middle cerebral artery clot em bolism were treated with recombinant tissue plasminogen activator (rt-PA) a t increasing delays (1.5, 3 and 4.5 h) after the onset of ischemia. Treatme nt efficacy was evaluated by NMR-imaging of the apparent diffusion coeffici ent of water (ADC). In untreated animals the size of the ADC-detectable les ion gradually increased after clot embolism, expanding over 8 h to 174 +/- 17% of the volume visible at 30 min. Thrombolysis initiated 1.5 h after emb olism did not reverse the ischemic lesion but reduced its growth to 113 +/- 19% (P < 0.05). Lesion size increased to 135 +/- 14% after 3 h (NS) and to 214 +/- 35% after 4.5 h delay (NS). Thrombolysis with rt-PA attenuates inf arct expansion but does not reverse ischemic injury. NeuroReport 10:3269-32 72 (C) 1999 Lippincott Williams & Wilkins.