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Figure 1 Representative strain rate and strain profiles at baseline and during ischemia. (a) Strain rate curves of the ischemic (apical) and nonischemic (basal) septal segments in an apical four-chamber view at baseline and during ischemia. Negative strain rate reflects shortening; positive strain rate reflects lengthening. The vertical lines in each image mark the time of the aortic valve opening and mitral valve closure, respectively. Peak strain rates were measured during ejection (S_SR), isovolumic relaxation (IVR_SR), and early filling (E_SR); t-S_SR represents the time to onset of longitudinal shortening (S_SR). At baseline, negative IVR_SR (postsystolic shortening) was found in the basal septal (nonischemic) segment. During occlusion, S_SR decreased and t-S_SR was delayed, while a prominent IVR_SR developed in the ischemic segment, but not in the normally perfused segment. Importantly, IVR_SR/S_SR was >1 only in the ischemic segment. (b) The corresponding regional strain curves. Reduced systolic strain (_sys) and increased postsystolic strain (_ps) occurred in the ischemic segment. Conversely, a normal sequence of contraction/relaxation occurred in the nonischemic (basal) segment.