Figure 3 Example of longitudinal strain rate (SR) graph (Doppler derived). Longitudinal strain rate using the region of interest. y-Axis represents strain rate (s-1), x-axis represents time (one cardiac cycle). Note the negative SR during systole when ε becomes more negative (myocardial shortening) and the positive SR during the upstroke of the strain curve during the E and A wave. The SR is zero when no deformation occurs .