Acoustic Activation Imaging of Intravenous Perfluoropropane Droplets To Detect Risk Area and Ultimate Infarct Size in a Large Animal Model of Ischemia/Reperfusion.

Abstract

OBJECTIVE: Acoustically activatable perfluoropropane droplets (PD) have been utilized to enhance the reperfused zone in acute myocardial infarction small animal models. Despite the correlation with infarct size, the enhanced area consistently overestimates infarct size. We hypothesized that the enhanced area correlates with risk area, and that hypo-enhanced areas (HEA) within the enhanced zone represent the ultimate infarct size. METHODS: Intravenous PD was administered in the reperfusion period following a 90 min period of ischemia in 30 pigs. Injections were given at either 30 min, 1 d or 7 d following reperfusion to determine what the enhanced regions within the reperfused zone following acoustic activation (AA) were detecting. Correlations of the enhanced and unenhanced regions with the infarct size using delayed enhancement magnetic resonance imaging (DE-MRI) were determined. RESULTS: AA within the reperfused zone was evident in 26 pigs (9/10 pigs injected at 30 min post-reperfusion, 9/10 pigs injected at 1 d and 8/10 pigs injected at 7 d). In the 26 pigs with AA, the extent of enhancement was significantly larger than the infarct size by DE-MRI, and correlated more closely with risk area (r = 0.55, p = 0.0002). A HEA within the enhanced region was observed in 21 of the 26 pigs with AA, and the spatial extent of HEA correlated with infarct size (r = 0.85; p < 0.0001). CONCLUSION: AA of intravenous PD enhances the risk area following reperfusion. However, it is the extent of hypo-enhancement within the enhanced region that predicts infarct size irrespective of the time AA is performed following reperfusion.