Usefulness of strain rate imaging in detecting ischemic myocardium during dobutamine stress.

Background: Tissue Doppler imaging-derived systolic myocardial velocity can detect subtle alterations in contractility during dobutamine stress. However, increased cardiac translation and tethering during dobutamine stress may affect measurements.

Methods: To examine the hypothesis that regional ischemic myocardium can be sensitively detected during dobutamine stress using myocardial strain rate, a new indicator of regional myocardial contraction that is independent of cardiac translation and tethering, we studied seven closed-chest pig confirmed chronic ischemic models produced by placing an ameroid constrictor on the left circumflex artery. Left ventricular short-axis tissue Doppler imaging was obtained at baseline and during dobutamine stress (10 and 30 microg/kg/min). Peak systolic myocardial velocity and peak systolic myocardial strain rate in anterior and posterior segments were derived offline at each stage.

Results: In peak systolic myocardial velocity and peak systolic myocardial strain rate, repeated-measures analysis of variance showed significant interaction between nonischemic and ischemic segments during dobutamine stress. Statistical significance between nonischemic and ischemic segments was reached at baseline, 10 microg/kg/min dobutamine, and 30 microg/kg/min dobutamine in peak systolic myocardial strain rate, and at 30 microg/kg/min dobutamine in peak systolic myocardial velocity. By receiver operating characteristic (ROC) analysis for predicting ischemic segments at 30 microg/kg/min dobutamine, a cutoff value of peak systolic myocardial strain rate was 4.84, with a sensitivity of 100% and a specificity of 100%. Peak systolic myocardial velocity was the less discriminating parameter (cutoff, 6.46; sensitivity, 86%; specificity, 86%).

Conclusions: Myocardial strain rate imaging might represent an accurate parameter for clinical recognition of regional ischemic myocardium during dobutamine stress echocardiography.