Background Postsystolic shortening (PSS) has been proposed as a marker of myocardial dysfunction. Strain rate imaging (SRI)is a novel ultrasonic technique, allowing reliable and noninvasive measurement of myocardial deformation.The purpose of this study was to investigate the characteristics of myocardial longitudinal PSS by SRI in ischemic and infarct myocardium in patients with coronary artery disease, and to explore its clinical applicability.Methods Eleven patients with angina pectoris, 21 patients with myocardial infarction and 20 healthy subjects were included in the study. Apical four-, three- and two-chamber views were displayed; and septal, lateral, anteroseptal,posterior, anterior and inferior walls of the left ventricle were scanned, respectively. PSS strain (εpss), the ratio of εpss and systolic strain (εpss/εsys), the ratio of εpss and maximum strain (εpss/εmax) and the duration of PSS (Tpss) in ischemic, infarct and normal myocardium were analyzed.Results PSS was found more frequent in the ischemic and infarct segments compared with the normal segments (39%vs 22% and 56% vs 22%, respectively; both P＜0.01). It was even more frequent in the infarct segments than in the ischemic segments (56% vs 39%, P＜0.01). The absolute magnitude of εpss, εpss/εsys, εpss/εmax were significantly larger and Tpss significantly longer in the ischemic and infarct segments compared with that in the normal myocardium (P＜0.01).εpss/εsys, εpss/εmax were even larger and Tpss even longer in the infarct than in the ischemic segments (P＜0.01).Conclusions PSS is a common and important feature of the ischemic and infarct myocardium. εpss, εpss/εsys, εpss/εmax and Tpss as measured by SRI may be promising markers for the quantitative assessment of regional myocardial dysfunction in patients with coronary artery disease. εpss/εsys, εpss/εmax and Tpss may be helpful in differentiating infarct from ischemic myocardium.