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Figure 5 Impact of angulation on strain rate imaging. Interrogation parallel with the wall (mid-septum, shown in blue) identifies long-axis shortening, and at right angles to the wall (apex, shown in red) identifies short-axis thickening. However, an intermediate angle (apical septum, shown in yellow) causes underestimation—a mixture of vectors at 45% produces a net absence of recordable strain. Scan planes are shown as continuous lines, longitudinal and radial contraction vectors as broken lines.