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Figure 7 Circumferential deformation of the subendocardial and subepicardial regions of left ventricular apex by 2-dimensional speckle tracking of B-mode ultrasound images (2-dimensional strain). Note the presence of positive strains (lengthening) during the phase of isovolumic contraction. Note the higher circumferential strains of the subendocardial regions as compared with the subepicardial region. Peak shortening in some segments of the subepicardial region extends beyond the timing of aortic valve closure (postsystolic shortening, arrow). Phases 1 to 5 are described in the legend to Figure 6. ECG = electrocardiogram.