Abstract
OBJECTIVES: Increasing evidence confirms that microbubble (MB)-augmented ultrasound (US) thrombolysis enhances clot lysis with or without tissue plasminogen activator (tPA). Intracranial hemorrhage (ICH) is a major complication militating against tPA use in acute ischemic stroke. We quantified the incidence of ICH associated with tPA thrombolysis and MB + US therapy and compared infarct volumes in a rabbit model of acute ischemic stroke. MATERIALS AND METHODS: Rabbits (n = 158) received a 1.0-mm clot, angiographically injected into the internal carotid artery causing infarcts. Rabbits were randomized to 6 test groups including (1) control (n = 50), embolized without therapy, (2) US (n = 18), (3) tPA only (n = 27), (4) tPA + US (n = 22), (5) MB + US (n = 27), and (6) tPA + MB + US (n = 14). US groups received pulsed wave US (1 MHz, 0.8 W/cm) for 1 hour; rabbits with tPA received intravenous tPA (0.9 mg/kg) over 1 hour. Rabbits with MB received intravenous MB (0.16 mg/kg) given over 30 minutes. Rabbits were killed 24 hours later and infarct volume and incidence, location, and severity of ICH were determined by histology and pathologic examination. RESULTS: Percentage of rabbits having ICH outside the infarct area was significantly decreased (P = 0.004) for MB + US (19%) rabbits compared with tPA + US (73%), US only (56%), tPA (48%), tPA + MB + US (36%), and control (36%) rabbits. Incidence and severity of ICH within the infarct did not differ (P > 0.39). Infarct volume was significantly greater (P = 0.002) for rabbits receiving US (0.97% ± 0.17%) than for MB + US (0.20% ± 0.14%), tPA + US (0.15% ± 0.16%), tPA (0.14% ± 0.14%), and tPA + MB + US (0.10% ± 20%) rabbits; these treatments collectively, excluding US only, differed (P = 0.03) from control (0.45% ± 0.10%). CONCLUSIONS: Treatment with MB + US after embolization decreased the incidence of ICH and efficacy was similar to tPA in reducing infarct volume.