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Treatment of Acute Intravascular Thrombi With Diagnostic Ultrasound and Intravenous Microbubbles

Feng Xie, MD^_*, John Lof, MS^_*, Carr Everbach, PhD, Anming He, PhD, Richard M. Bennett, PhD, Terry Matsunaga, PhD, Jason Johanning, MD^_*, Thomas R. Porter, MD^_*,_*

^_* Department of Internal Medicine/Section of Cardiology or the Department of Surgery, University of Nebraska Medical Center, Omaha, Nebraska
Swarthmore College, Swarthmore, Pennsylvania
Siemens Medical Solutions, Mountain View, California
University of Arizona, Tucson, Arizona

^_* Reprint requests and correspondence: Dr. Thomas R. Porter, University of Nebraska Medical Center, 982265 Nebraska Medical Center, Omaha, Nebraska 68198-2265 (Email: trporter{at}unmc.edu).

The purpose of this study was to determine whether high mechanical index (MI) impulses from diagnostic ultrasound (DUS) could dissolve intravascular thrombi using intravenous microbubbles. Using a canine model, DUS was applied during a continuous intravenous infusion of microbubbles. Completely thrombosed grafts were assigned to 2 treatment regimens: low-MI (<0.5-MI) ultrasound alone; or intermittent high-MI impulses (1.9-MI) guided by low-MI ultrasound (contrast pulse sequencing). A 20-MHz cavitation detector was placed confocal to the ultrasound transducer to make intravascular cavitation measurements in 1 dog. Intravascular cavitational activity was detected when an MI of >0.5 was applied. In grafts treated with intermittent high-MI ultrasound, angiographic success was 71% at 30 min and 79% at 45 min, compared with 20% and 30% at these times in the low-MI ultrasound alone group (p < 0.05). We conclude that a commercially available DUS transducer can successfully recanalize acute intravascular thrombi during a continuous microbubble infusion.

Key Words: cavitation • microbubbles • ultrasound • thrombolysis

Abbreviations and Acronyms   CPS = contrast pulse sequencing   DUS = diagnostic ultrasound   MI = mechanical index   PNP = peak negative pressures