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 (epsilon(ps)) to strain during ejection time (epsilon(et)) (epsilon(ps)/epsilon(et)) (P < 0.05); epsilon(max) and epsilon(et) were reduced slightly, epsilon(ps) and the ratio of epsilon(ps) to maximal systolic strain (epsilon(max))(epsilon(ps)/epsilon(max)) were increased minimally, but had no significance(P > 0.05). During infarction, the epsilon(ps) and the ratios of epsilon(ps)/epsilon(max) and epsilon(ps)/epsilon(et) were increased markedly (P < 0.01) and epsilon(et) and SR(peak sys) decreased as compared with that at baseline and during ischemia, whereas epsilon(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 epsilon(et) were significantly reduced (P < 0.05), whereas epsilon(ps), epsilon(ps)/epsilon(max) and epsilon(ps)/epsilon(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. epsilon(ps)/epsilon(max) and epsilon(ps)/epsilon(et) can be used as objective indices to identify the ischemic myocardium.