Use of peak systolic strain as an index of regional left ventricular function: Comparison with tissue Doppler velocity during dobutamine stress and myocardial ischemia

Objectives: The goals of this study were to examine peak systolic strain as an index of regional function in an animal model of inotropic stress and i schemia, and to compare these results with peak systolic myocardial tissue Doppler velocity (MDV). Background: Myocardial tissue Doppler velocity is an objective measure of r egional left ventricular responses to inotropic stimulation and ischemia, b ut it is affected by tethering from adjacent segments and translational mov ement. Myocardial Doppler strain (epsilon(s) relative change in length) is a more local measure of contractility, which can now be derived noninvasive ly from MDV. Methods: Eight dogs underwent graded dobutamine infusion followed by corona ry occlusion. Epicardial 2-dimensional echocardiography and color MDV of th e left ventricle were obtained and digitized from the short-axis view at ba seline and with dobutamine doses of 2, 4, and 8 mu g/kg per minute. These w ere repeated 0, 10, 20, 45, and 90 seconds after occlusion of the left ante rior descending artery (LAD) (n = 3) or circumflex coronary artery (n = 5). Dobutamine was continued at 8 mu g/kg per minute during coronary occlusion . The peak systolic radial MDV (cm/s) and systolic strain (epsilon(s), perc ent thickening) in the anterior and posterior walls were measured off-line at each stage. Results: Dobutamine caused an increase in MDV (P = .0001) and epsilon(s) (P = .09) above baseline values. Coronary occlusion caused a reduction in wal l motion; after 45 seconds, all nonperfused segments were hypokinetic. Ther e was a corresponding decrease in MDV and epsilon(s), but this occurred ear lier for epsilon(s), and the difference between ischemic and nonischemic se g ments was greater for epsilon(s) than for MDV (P < .03). Nonischemic regi ons trended to an increase in epsilon(s) (compensatory hyperkinesis), where as MDV trended downward, probably reflecting the global decrease in left ve ntricular function. Conclusion: Both MDV and epsilon(s) increase with dobutamine and decrease d uring ischemia. epsilon(s) appears to respond to local ischemia earlier tha n MDV, perhaps because it is a more local measure. Thus epsilon(s) may prov e to be an accurate parameter for the clinical recognition of regional isch emia.