Use of Peak Systolic Strain as an Index of Regional Left Ventricular Function: Comparison with Tissue Doppler Velocity During Dobutamine Stress and Myocardial Ischemia

Abstract

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 ischemia, and to compare these results with peak systolic myocardial tissue Doppler velocity (MDV). Background: Myocardial tissue Doppler velocity is an objective measure of regional left ventricular responses to inotropic stimulation and ischemia, but it is affected by tethering from adjacent segments and translational movement. Myocardial Doppler strain (ϵ, relative change in length) is a more local measure of contractility, which can now be derived noninvasively from MDV. Methods: Eight dogs underwent graded dobutamine infusion followed by coronary occlusion. Epicardial 2-dimensional echocardiography and color MDV of the left ventricle were obtained and digitized from the short-axis view at baseline and with dobu-tamine doses of 2, 4, and 8 μg/kg per minute. These were repeated 0, 10, 20, 45, and 90 seconds after occlusion of the left anterior descending artery (LAD) (n = 3) or circumflex coronary artery (n = 5). Dobutamine was continued at 8 μg/kg per minute during coronary occlusion. The peak systolic radial MDV (cm/s) and systolic strain (ϵs, percent thickening) in the anterior and posterior walls were measured off-line at each stage. Results: Dobutamine caused an increase in MDV (P =.0001) and ϵs (P =.09) above baseline values. Coronary occlusion caused a reduction in wall motion; after 45 seconds, all nonperfused segments were hypokinetic. There was a corresponding decrease in MDV and ϵs, but this occurred earlier for ϵs, and the difference between ischemic and nonischemic segments was greater for ϵs than for MDV (P <.03). Nonischemic regions trended to an increase in ϵs (compensatory hyperkinesis), whereas MDV trended downward, probably reflecting the global decrease in left ventricular function. Conclusion: Both MDV and ϵs increase with dobutamine and decrease during ischemia. ϵs appears to respond to local ischemia earlier than MDV, perhaps because it is a more local measure. Thus ϵs may prove to be an accurate parameter for the clinical recognition of regional ischemia. (J Am Soc Echocardiogr 2000;13:731-7.)