Assessment of ischemic myocardium by strain-rate imaging during adenosine stress echocardiography

Strain rate (SR) provides a quantitative segmental analysis of myocardial function. However, the use of SR with stress echocardiography to determine the ischemic myocardium has not been completely investigated. The present study aimed to determine the changes in systolic function of the ischemic myocardium by strain-rate imaging (SRI) with adenosine stress echocardiography.

Stenosis and complete occlusion of coronary arteries were produced in 11 canine models by constricting the left anterior descending coronary artery (LAD). Myocardial longitudinal strain with adenosine was measured at baseline and during ischemia and infarction.

Strain and SR did not differ during ischemia and infarction as compared with that at baseline in non-LAD segments or after adenosine treatment. As compared with baseline, during ischemia, LAD segments showed significantly decreased peak systolic SR (SR_peak  sys) (P < 0.05) and significantly increased ratio of postsystolic strain (ɛ_ps) to strain during ejection time (ɛ_et) (ɛ_ps/ɛ_et) (P < 0.05); ɛ_max and ɛ_et were reduced slightly, ɛ_ps and the ratio of ɛ_ps to maximal systolic strain (ɛ_max)(ɛ_ps/ɛ_max) were increased minimally, but had no significance(P > 0.05). During infarction, the ɛ_ps and the ratios of ɛ_ps/ɛ_max and ɛ_ps/ɛ_et were increased markedly (P < 0.01) and ɛ_et and SR_peak  sys decreased as compared with that at baseline and during ischemia, whereas ɛ_max was reduced only with at baseline (P < 0.01). After adenosine treatment, in the non-LAD segments, the values of strain and SR did not change at baseline or during ischemia and infarction and in LAD segments, values did not change at baseline and during infarction. However, during ischemia, SR_peak  sys and ɛ_et were significantly reduced (P < 0.05), whereas ɛ_ps, ɛ_ps/ɛ_max and ɛ_ps/ɛ_et were increased (P < 0.05 and < 0.01, respectively).

Combined with adenosine stress echocardiography, SRI can quantitatively differentiate the ischemic from non-ischemic myocardium. ɛ_ps/ɛ_max and ɛ_ps/ɛ_et can be used as objective indices to identify the ischemic myocardium.