Objective
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.
Methods
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.
Results
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 (SRpeak sys) (P < 0.05) and significantly increased ratio of postsystolic strain (ɛps) to strain during ejection time (ɛet) (ɛps/ɛet) (P < 0.05); ɛmax and ɛet were reduced slightly, ɛps and the ratio of ɛps to maximal systolic strain (ɛmax)(ɛps/ɛmax) were increased minimally, but had no significance(P > 0.05). During infarction, the ɛps and the ratios of ɛps/ɛmax and ɛps/ɛet were increased markedly (P < 0.01) and ɛet and SRpeak sys decreased as compared with that at baseline and during ischemia, whereas ɛmax 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, SRpeak sys and ɛet were significantly reduced (P < 0.05), whereas ɛps, ɛps/ɛmax and ɛps/ɛet were increased (P < 0.05 and < 0.01, respectively).
Conclusion
Combined with adenosine stress echocardiography, SRI can quantitatively differentiate the ischemic from non-ischemic myocardium. ɛps/ɛmax and ɛps/ɛet can be used as objective indices to identify the ischemic myocardium.