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Figure 9 Direct in vivo imaging of anterior wall of a beating porcine left ventricle using high-resolution linear array transducer (10 MHz). (A) Anatomic M-mode imaging of the different layers of anterior segment of left ventricular apex at high temporal resolution (250 frames/s). During isovolumic contraction, the endocardium moves toward the cavity (blue arrows) and is accompanied with a reciprocal outward movement of the subepicardium (white arrows). A reverse pattern of movement is seen during isovolumic relaxation. These reciprocal movements of the subendocardial and subepicardial regions also are seen in tissue Doppler imaging, in the form of simultaneous red and blue colors within the inner and outer layers of the same segment of the myocardial wall during isovolumic contraction and vice versa during isovolumic relaxation (B). Phases 1 to 5 are described in the legend to Figure 6.