High-frequency ultrasound for quantitative characterization of myocardial edema

Myocardial edema has been associated with impaired ventricular compliance a nd diastolic filling. To determine the sensitivity of high-frequency (40 MH z) ultrasound to myocardial edema, we employed a model in which myocardial edema was induced by immersion of tissue in isotonic saline. The effect of freezing tissue on edema formation was also evaluated. Rat hearts were arre sted at end-diastole and insonified fresh within 15 min of excision (n = 5) or following being frozen for 24 h and thawed (n = 4), Measurements of att enuation, backscatter, tissue thickness and speed of sound were performed a t baseline and hourly for 4 h, and compared with direct measurements of myo cardial edema. Fresh tissue demonstrated a greater propensity for the devel opment of edema than frozen tissue. Integrated backscatter increased in bot h tissues, whereas the magnitude and slope of attenuation decreased as edem a evolved. We conclude that high-frequency ultrasound sensitively detects m yocardial edema, and we propose that the extension of these methods to clin ical frequencies may prove useful for monitoring and treatment of cardiac e dematous disease states. (C) 2000 World Federation for Ultrasound in Medici ne & Biology.