High resolution integrated backscatter in acute myocardial ischemia

The value of high resolution integrated backscatter (IB) for use in myocardial tissue characterization during acute ischemia was examined. In closed chest dogs, myocardial ischemia was induced in a small region. Before and after 5, 30 and 60 minutes of occlusion, echocardiography was performed. High resolution digital radiofrequency (RF) data of the complete sectorscan, and of 2 consecutive heart cycles, were acquired using a new acquisition approach. A region of interest was drawn on each image in both the (normally perfused) septum and the (ischemic) posterior wall. IB and cyclic variation (CV) of IB was calculated. Values were expressed using a linear scale. We found a significant increase in mean IB after 5 min in the ischemic region compared to the normally perfused region in all experiments. This increase persisted during the 60 minutes of occlusion. Furthermore, an increase in CV was observed during ischemia. This is in contradiction to the findings of other groups. One of the explanations is that we don't express the values on a logarithmic scale (dB), We can state that comparing the mean IB from different regions within the myocardium can discriminate ischemia in a very early stage in a canine model. The value and the meaning of the change in CV of IB however is not straightforward and remains an issue for further investigation.