Improved Ultrasound-Mediated Molecular Imaging of Previously Ischemic Mouse Myocardium Using Dual-Targeted Microbubbles and Constant Infusion

Molecularly targeted ultrasound contrast agents have been shown to identify previously-ischemic regions of the myocardium by targeting cell adhesion molecules that are displayed on activated endothelial surfaces in response to ischemia/reperfusion injury. An improved method for targeted microbubble (MB) delivery using constant infusion and dual targeted microbubbles is presented to enable better characterization of microbubble interaction with activated endothelium. Ten male C57BL/6 mice underwent 15-minute Left Anterior Descending (LAD) coronary occlusion followed by 2-hour reperfusion. Immediately after the 2-hour reperfusion, mouse hearts were imaged with a Sequoia scanner and 15L8 transducer. All mice received three of five MB preparations in random order: Sialyl Lewis X MB (MB_X), anti-P-Selectin (MB_P), anti-VCAM MB (MB_V), Sialyl Lewis X + anti-VCAM MB (MB_D), and isotype control MB (MB_I). Subsequently, mouse hearts were excised and stained with TTC & Phthalo blue dyes to assess infarct size and area at risk, respectively. Video data indicated that the binding of targeted MB to ischemic regions was significantly higher for MB_D, MB_X, MB_P, and MB_V, compared to MB_I (p<;0.05). Furthermore, normalized intensity for MB_D was higher than both MB_X and MB_V (p<;0.05). Using Phthalo blue dye as the gold standard, receiver operating curve analysis demonstrated accurate detection of both ischemic and non-ischemic regions using MB_D (AUC = 0.90), MB_X (AUC = 0.89), MB_P (AUC = 0.87), and MB_V (AUC = 0.97).