Acoustic Activation Imaging With Intravenous Perfluoropropane Nanodroplets Results in Selective Bioactivation of the Risk Area

Background Acoustically activatable perfluoropropane droplets (PD) can be formulated from commercially available microbubble preparations. Diagnostic transthoracic ultrasound frequencies have resulted in acoustic activation (AA) predominately within myocardial infarct zones (IZ). Objective We hypothesized that the AA area following acute coronary ischemia/reperfusion (I/R) would selectively enhance the developing scar zone, and target bioeffects specifically to this region. Methods We administered intravenous PD in 36 rats and 20 pigs at various stages of myocardial scar formation (30 minutes, 1 day, and 7 days post I/R) to determine what effect infarct age had on the AA within the IZ. This was correlated with histology, myeloperoxidase activity, and tissue nitrite activity. Results The degree of AA within the IZ in rats was not associated with collagen content, neutrophil infiltration, or infarct age. AA within 24 hours of I/R was associated with increased nitric oxide utilization selectively within the IZ (P < .05 compared with remote zone). The spatial extent of AA in pigs correlated with infarct size only when performed before sacrifice at 7 days (r = .74, P < .01). Conclusions Acoustic activation of intravenous PD enhances the developing scar zone following I/R, and results in selective tissue nitric oxide utilization.