BACKGROUNDSince the size of ischemic myocardium is closely related with both global and regional function of the myocardium, it is of great significance to measure the size of ischemic myocardium with non-invasive methods.

METHODSEleven mongrel dogs were subjected to occlusion of the left anterior descending coronary artery for acute ischemia. Strain rate imaging had M-mode of strain-rate (CAMM) curve pointed from the basal segment of the anterior wall to the basal segment of the inferior wall to detect the border of ischemia size. The strain rate (SR) defined the cut-off value of ischemic myocardium in a two-chamber apical view, and marked by the anterior and inferior wall on two-dimensional images respectively. Along the endocardium and epicardium, the ischemic size was curved on two-dimensional images by the trackball method and then compared with the pathologically ischemic size. And then longitudinal strain rates were compared in the cut-off value, adjacent non-ischemic and ischemic segments at which the cut-off point was defined by changing the curve M-mode of strain rate after ischemia.

RESULTSLinear correlation existed between pathology and strain rate ischemic size (r = 0.884, P < 0.001). The SR parameters were lower in ischemia and cut-off point than in non-ischemic segments. The peak SRs of systole (S(SR)), early diastole (E(SR)), late diastole (A(SR)), strain during ejection time (epsilon(et)), and the maximum length change during the entire heart cycle (epsilon(max)) in ischemic segments lowered (P < 0.05). Time to onset of regional relaxation (T(R)) was prolonged (P = 0.012).

CONCLUSIONSR imaging can accurately assess the size of ischemic myocardium.