2I-2 Quantification and MRI Validation of Regional Cardiac Contractile Dysfunction in Mice Post Myocardial Infarction Using High Resolution Ultrasound

High resolution 30 MHz ultrasound imaging was performed on the left ventricles (LV) of C57B1/6 mice post myocardial infarction (MI). Normal (no MI) C57B1/6 mice were examined as control experiments. Ultrasound imaging was performed at 5-7 short axis slices and 4-5 long axis slices at 1 mm intervals that encompass the LV. Myocardial tissue displacement vectors were measured using a 2D ultrasonic speckle tracking algorithm with sub-pixel resolution. The pixel block window size was approximately 0.4 mm times 0.4 mm and the search region was 0.6 mm times 0.6 mm. The extent of contractile dysfunction and cardiac dyssynchrony were revealed in post-MI mouse LVs by regional myocardial displacement and strain analyses. Strain analyses from the mid-ventricular short axis based upon the ultrasound images were compared to those obtained using MRI, and high levels of correlation were obtained (R = 0.91 and R = 0.84 for radial and circumferential strain, respectively). Displacement and strain analyses were conducted on multiple short axis and long axis slices, and 3D displacement vectors were determined at the lines of intersection by summing the vector components derived from each of the orthogonal slices