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Microbubble-Augmented Ultrasound Sonothrombolysis Decreases Intracranial Hemorrhage in a Rabbit Model of Acute Ischemic Stroke

Flores, Rene PhD*; Hennings, Leah J. DVM; Lowery, John D. DVM; Brown, Aliza T. PhD*; Culp, William C. MD*

doi: 10.1097/RLI.0b013e31820e143a
Original Article
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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/cm2) 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.

From the Departments of *Radiology, †Pathology, University of Arkansas for Medical Sciences, Little Rock, AR; and ‡Division of Lab Animal Medicine, University of Arkansas for Medical Sciences, Little Rock, AR.

Received October 21, 2010, and accepted for publication (after revision) December 31, 2010.

Supported by NIH grant R01 HL092481.

Reprints: William C. Culp, MD, Department of Radiology, University of Arkansas for Medical Sciences, M1/269, 4301 West Markham St., Little Rock, AR 72205. E-mail: CulpWilliamC@uams.edu.

© 2011 Lippincott Williams & Wilkins, Inc.