ECHOCARDIOGRAPHIC DETECTION OF ISCHEMIC AND INFARCTED MYOCARDIUM

[摘要] The potential of a clinically adaptable 2-dimensional echocardiographic system was determined using computer enhancement and a mathematically defined integrated backscatter ratio for the early detection of ischemic and infarcted myocardium. Fifteen dogs had 2-dimensional echocardiograms recorded during either open chest coronary occlusion (n = 5), closed chest occlusion (n = 5), occlusion followed by reperfusion (n = 3) or sham coronary occlusion (n = 2). A serial increase in integrated backscatter ratio, representing differences in returned ultrasound intensities between a reference point and specific myocardial regions, was detected between 7 and 12 min of complete occlusion in 9 of 12 animals (P < 0.05), and at min 18, 43 and 67 in the remaining 3 animals. Reperfusion after 20 min of occlusion in 2 studies resulted in normalization of the backscatter ratio. An increase in backscatter ratio was not detected when 5 min occlusion periods were used or during the 5 h sham occlusion studies. The computer enhancement techniques utilized in this study provided increased visual detail of intracardiac structures over that provided by routine 2-dimensional echocardiograms; myocardial tissue was identifiable in what appeared to be echo-free segments; and boundaries that appeared as noncontiguous horizontal lines on the routine echocardiograms were identifiable as trabeculae. Significant increases in backscatter from nonperfused myocardium are detectable echocardiographically within 12 min of coronary occlusion and temporal changes can be assessed in the canine model, and the echocardiographic data acquisition and computer analysis system utilized provide a clinically adaptable approach to identify and map myocardial characteristics in human beings.