Diagram of left-ventricular strain and twist. Diagram of left-ventricular strain and twist. A 3D view is shown in (A), a 2D short-axis view as observed from the LV base is shown in (B), and a 2D long-axis view is displayed in (C). Strain measures the lengthening or shortening of muscle tissue in a given direction. During contraction, normal tissue lengthens radially (RR), shortens both circumferentially (CC) and longitudinally (LL), and shears slightly (RC, RL, CL). Twist (θ) measures the angular displacement of muscle tissue around the left ventricular centerline. During contraction, normal tissue undergoes a clockwise twist from p(0) to p(t).