Echocardiographic detection of ischemic and infarcted myocardium

Abstract

The purpose of this study was to determine the potential of a clinically adaptable two-dimensional echocardiographic system using computer enhancement and a mathematically defined integrated backscatter ratio for the early detection of ischemic and infarcted myocardium. Fifteen dogs had two-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 minutes of complete occlusion in 9 of 12 animals (p less than 0.05), and at minutes 18, 43 and 67 in the remaining 3 animals. Reperfusion after 20 minutes of occlusion in two studies resulted in normalization of the backscatter ratio. An increase in backscatter ratio was not detected when 5 minute occlusion periods were used or during the 5 hour sham occlusion studies. The computer enhancement techniques utilized in this study provided increased visual detail of intracardiac structures over that provided by routine two-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. The results indicate that: 1) significant increases in backscatter from nonperfused myocardium are detectable echocardiographically within 12 minutes of coronary occlusion and temporal changes can be assessed in the canine model, and 2) the echocardiographic data acquisition and computer analysis system utilized provide a clinically adaptable approach to identify and map myocardial characteristics in human beings.

Two-dimensional ultrasonic tissue characterization: backscatter power, endocardial wall motion, and their phase relationship for normal, ischemic, and infarcted myocardium.

“…Thus, a variable must be free of any angle dependence with respect to the region of interest and free from attenuation effects. An absolute measurement such as mean backscatter power, which has been used by several investigators, 22,23,28,29 has certain reference difficulties that potentially limit its clinical usefulness. On the other hand, relative measurements such as the cyclic backscatter power and the phase relationship may be useful in the clinical environment.…”

Echocardiography and coronary artery disease: Current and future applications

“…Those schemes which rely on cyclic variation in this backscattered intensity [50] are directly linked to the mechanical function of the heart and may not provide additional information above analysis of wall motion alone. Other investigators however have looked at the myocardial intensity at only one point in time, thus in part separating out the effect of wall motion [51][52][53][54][55]. In virtually all studies reported to date there are statistically significant differences in the intensity and quality of backscattered ultrasound in infarcted or ischemic myocardium when compared to normal control regions.…”

“…The distribution of these intensities is then subject to statistical analysis and a description of their uniformity (or lack of uniformity) is generated. Most studies have demonstrated that with the onset of ischemia overall backscatter intensity increases [51][52][53][54][55] and the range of distribution of the gray levels becomes broader [53]. Fig.…”

“…Fig. 7 was taken from the work of Rasmussen et al [52] and demonstrates the increase in backscatter seen with transient myocardial ischemia in an animal model. The studies reported to date are limited in that they compare 249 normal with infarcted or ischemic myocardium.…”

Ultrasound Characterization of Acute Myocardial Ischemia by Quantitative Texture Analysis

“…As mentioned above, improved methods of gain compensation for attenuation will be required to deal effectively with this problem. Rasmussen et al [27] recently described a method involving the use of an internal myocardial reference calibration which compensates for the backscatter influence of the chest wall, coupled with computer acquisition and enhancement of myocardial images. The further applicability of this method to all myocardial regions remains to be determined.…”